Method and apparatus for enhancing coverage of machine type communication (MTC) devices

Abstract

To provide a method and apparatus allowing a low cost machine-type-communication (LC-MTC) wireless transmit / receive unit to enhance coverage.SOLUTION: An example method for physical broadcast channel enhancement includes receiving system information on an enhanced PBCH. The ePBCH is located in a set of radio frames which is a subset of available radio frames, where the subset includes fewer radio frames than all the available radio frames. The ePBCH is received in at least one radio frame in the set of radio frames. An example method for physical random access channel enhancement includes receiving a configuration of legacy PRACH resources and a configuration of enhanced PRACH resources. The WTRU selects one of the legacy PRACH resources and ePRACH resources on the basis of a coverage capability.SELECTED DRAWING: Figure 1A

Description

Technical Field

[0001] This application relates to wireless communications.

Background Art

[0002] This application claims the benefit of U.S. Provisional Application No. 61 / 710,315, filed October 5, 2012; U.S. Provisional Application No. 61 / 753,263, filed January 16, 2013; U.S. Provisional Application No. 61 / 807,945, filed April 3, 2013; and U.S. Provisional Application No. 61 / 863,223, filed August 7, 2013.

[0003] Communication devices, such as wireless transmit-receive units (WTRUs), can communicate with remote devices via a communication system. A WTRU can be configured to perform machine-to-machine (M2M) or machine-type communication (MTC), which are communications that can be performed without human intervention. This form of communication can have applications in smart metering, home automation, e-health, fleet management, and other similar environments.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The service coverage of a device such as a low-cost MTC device or a type of device (e.g., a Long-Term Evolution (LTE) or LTE-Advanced (LTE-A) device) may desirably be improved, for example, by up to several dB (e.g., 20 dB), compared to the LTE cell coverage defined for a device different from the low-cost MTC device. In this case, the requirements for throughput and latency can be relaxed. For example, the message size can be limited, such as on the order of a maximum of 100 bytes per message in the uplink (UL) and / or on the order of a maximum of 20 bytes per message in the downlink (DL). In another example, the latency can be relaxed to allow a maximum of 10 seconds for the DL and / or a maximum of 1 hour for the UL. Such relaxation of requirements can make it impossible to support certain services such as voice.

Means for Solving the Problem

[0005] Methods and apparatuses for enhancing coverage of a low cost machine type communication (LC-MTC) wireless transmit receive unit (WTRU) are described. In an example, a method for physical broadcast channel (PBCH) enhancement includes receiving, at a WTRU, system information for an enhanced PBCH (ePBCH) from a base station. The ePBCH is placed within a set of radio frames that is a subset of the available radio frames, where the subset includes fewer radio frames than all of the available radio frames. The ePBCH is received within at least one radio frame of the set of radio frames. In another example, a method for physical random access channel (PRACH) enhancement includes receiving, by a WTRU, a configuration of legacy PRACH resources and a configuration of enhanced (enhanced) PRACH (ePRACH) resources. The WTRU selects one of the legacy PRACH resources or the ePRACH resources based on a coverage capability. In another example, a method for physical random access channel (PRACH) enhancement includes receiving a configuration of enhanced (enhanced) PRACH (ePRACH) resources, where the ePRACH resources include a plurality of ePRACH resource types, and each ePRACH resource type is associated with a coverage capability.

[0006] A more detailed understanding can be obtained from the following description, given by way of example and used in conjunction with the accompanying drawings.

Advantages of the Invention

[0007] Methods and apparatuses for enhancing coverage of a low cost machine type communication (LC-MTC) wireless transmit receive unit (WTRU) are provided.

Brief Description of the Drawings

[0008]

Figure 1A

Figure 1B

Figure 1C

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Best Mode for Carrying Out the Invention

[0009] FIG. 1A is a diagram of an exemplary communication system 100 in which one or more of the disclosed embodiments may be implemented. The communication system 100 can be a multi-connection system that provides content such as voice, data, video, messaging, broadcasting, etc. to a plurality of wireless users. The communication system 100 can enable a plurality of wireless users to access such content through sharing of system resources including wireless bandwidth. For example, the communication system 100 can utilize one or more (one or more) channel access methods such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single carrier FDMA (SC-FDMA).

[0010] As shown in FIG. 1A, the communication system 100 can include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, a radio access network (RAN) 104, a core network 106, a public switched telephone network (PSTN) 108, the Internet 110, and other networks 112, although it will be understood that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of the WTRUs 102a, 102b, 102c, 102d can be any type of device configured to operate and / or communicate in a wireless environment. By way of example, the WTRUs 102a, 102b, 102c, 102d can be configured to transmit and / or receive wireless signals and can include user equipment (UE), mobile stations, fixed or mobile subscriber units, pagers, cellular telephones, personal digital assistants (PDA), smartphones, laptops, netbooks, personal computers, wireless sensors, home appliances, machine-to-machine, etc.

[0011] The communication system 100 may also include base stations 114a and 114b. Each of the base stations 114a, 114b may be any type of device configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more (one or more) communication networks such as the core network 106, the Internet 110, and / or other networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), Node B, eNode B, home Node B, home eNode B, site controller, access point (AP), wireless router, etc. Although the base stations 114a, 114b are each shown as a single element, it will be understood that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0012] Base station 114a may be part of the RAN 104, which may also include other base stations and / or network elements (not shown) such as a base station controller (BSC), radio network controller (RNC), relay node, etc. Base station 114a and / or base station 114b may be configured to transmit and / or receive wireless signals within a particular geographic area, sometimes referred to as a cell (not shown). The cell may be further divided into cell sectors. For example, the cell associated with base station 114a may be divided into three sectors. Thus, in one embodiment, base station 114a may include three transceivers, one for each sector of the cell. In another embodiment, base station 114a may utilize multiple-input multiple-output (MIMO) technology and thus may utilize multiple transceivers for each sector of the cell.

[0013] Base stations 114a, 114b can communicate with one or more of WTRUs 102a, 102b, 102c, 102d over air interface 116, and air interface 116 can be any suitable wireless communication link (e.g., radio frequency (RF), microwave, infrared (IR), ultraviolet (UV), visible light, etc.). Air interface 116 can be established using any suitable radio access technology (RAT).

[0014] More specifically, as mentioned above, communication system 100 can be a multi-connectivity system and can utilize one or more (one or more) channel access methods such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, etc. For example, base stations 114a within RAN 104, and WTRUs 102a, 102b, 102c can implement radio technologies such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA) where air interface 116 can be established using Wideband CDMA (WCDMA). WCDMA can include communication protocols such as High-Speed Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA can include High-Speed Downlink Packet Access (HSDPA) and / or High-Speed Uplink Packet Access (HSUPA).

[0015] In another embodiment, base stations 114a, and WTRUs 102a, 102b, 102c can implement radio technologies such as Evolved UMTS Terrestrial Radio Access (E-UTRA) where air interface 116 can be established using Long-Term Evolution (LTE) and / or LTE-Advanced (LTE-A).

[0016] In other embodiments, base station 114a, and WTRUs 102a, 102b, 102c may implement radio technologies such as IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile Communications (GSM), Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), etc.

[0017] The base station 114b of FIG. 1A may be, for example, a wireless router, a home Node B, a home eNode B, or an access point, and may utilize any suitable RAT to facilitate wireless connectivity in a local area such as a workplace, home, vehicle, and campus. In one embodiment, base station 114b, and WTRUs 102c, 102d may implement a radio technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In another embodiment, base station 114b, and WTRUs 102c, 102d may implement a radio technology such as IEEE 802.15 to establish a wireless personal area network (WPAN). In yet another embodiment, base station 114b, and WTRUs 102c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, etc.) to establish a pico cell or a femto cell. As shown in FIG. 1A, base station 114b may have a direct connection to the Internet 110. Thus, base station 114b may not need to access the Internet 110 via the core network 106.

[0018] RAN 104 can communicate with core network 106, which can be any type of network configured to provide voice, data, applications, and / or Voice over Internet Protocol (VoIP) services to one or more of WTRUs 102a, 102b, 102c, 102d. For example, core network 106 can provide call control, billing services, mobile location-based services, prepaid calls, Internet connectivity, video distribution, etc., and / or can perform high-level security functions such as user authentication. Although not shown in Figure 1A, it will be understood that RAN 104 and / or core network 106 can communicate directly or indirectly with other RANs that utilize the same or a different RAT as RAN 104. For example, in addition to connecting to RAN 104 that can utilize E-UTRA radio technology, core network 106 can also communicate with another RAN (not shown) that utilizes GSM radio technology.

[0019] Core network 106 can also serve as a gateway for WTRUs 102a, 102b, 102c, 102d to access PSTN 108, Internet 110, and / or other networks 112. PSTN 108 can include a circuit-switched telephone network that provides plain old telephone service (POTS). Internet 110 can include a global system of interconnected computer networks and devices that use common communication protocols such as Transmission Control Protocol (TCP), User Datagram Protocol (UDP), and Internet Protocol (IP) within the TCP / IP Internet protocol suite. Network 112 can include wired or wireless communication networks owned and / or operated by other service providers. For example, network 112 can include another core network connected to one or more (one or more) RANs that may utilize the same or a different RAT as RAN 104.

[0020] Some or all of the WTRUs 102a, 102b, 102c, 102d within the communication system 100 can include a multi-mode function, i.e., the WTRUs 102a, 102b, 102c, 102d can include a plurality of transceivers for communicating with different wireless networks over different wireless links. For example, the WTRU 102c shown in Figure 1A can be configured to communicate with a base station 114a that can utilize cellular-based wireless technology and to communicate with a base station 114b that can utilize IEEE 802 wireless technology.

[0021] Figure 1B is a system diagram of an exemplary WTRU 102. As shown in Figure 1B, the WTRU 102 can include a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, a removable memory 130, a removable memory 132, a power supply 134, a global positioning system (GPS) chipset 136, and other peripheral devices 138. It will be understood that the WTRU 102 can include any sub-combination of the above elements while maintaining consistency with the embodiments.

[0022] Processor 118 can be a general - purpose processor, a dedicated processor, a conventional processor, a digital signal processor (DSP), multiple microprocessors, one or more (one or more) microprocessors in cooperation with a DSP core, a controller, a microcontroller, an application - specific integrated circuit (ASIC), a field - programmable gate array (FPGA) circuit, any other type of integrated circuit (IC), a state machine, etc. Processor 118 can perform signal encoding, data processing, power control, input / output processing, and / or any other function that enables the WTRU 102 to operate in a wireless environment. Processor 118 can be coupled to transceiver 120, and transceiver 120 can be coupled to transmit / receive element 122. Although FIG. 1B shows processor 118 and transceiver 120 as separate components, it will be understood that processor 118 and transceiver 120 can be integrated together in an electronic package or chip.

[0023] The transmit / receive element 122 can be configured to transmit signals to, or receive signals from, a base station (e.g., base station 114a) on the air interface 116. For example, in one embodiment, the transmit / receive element 122 can be an antenna configured to transmit and / or receive RF signals. In another embodiment, the transmit / receive element 122 can be a radiator / detector configured to transmit and / or receive, for example, IR, UV, or visible light signals. In yet another embodiment, the transmit / receive element 122 can be configured to transmit and receive both RF signals and optical signals. It will be understood that the transmit / receive element 122 can be configured to transmit and / or receive any combination of wireless signals.

[0024] In addition, in Figure 1B, the transmit / receive element 122 is shown as a single element, but the WTRU 102 can include any number of transmit / receive elements 122. More specifically, the WTRU 102 can utilize MIMO technology. Thus, in one embodiment, the WTRU 102 can include two or more transmit / receive elements 122 (e.g., multiple antennas) for transmitting and receiving wireless signals on the air interface 116.

[0025] The transceiver 120 can be configured to modulate signals transmitted by the transmit / receive element 122 and demodulate signals received by the transmit / receive element 122. As mentioned above, the WTRU 102 can have a multi-mode function. Thus, the transceiver 120 can include multiple transceivers to enable the WTRU 102 to communicate via multiple RATs such as, for example, UTRA and IEEE 802.11.

[0026] The processor 118 of the WTRU 102 can be coupled to the speaker / microphone 124, keypad 126, and / or display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or an organic light emitting diode (OLED) display unit) and can receive user input data therefrom. The processor 118 can also output user data to the speaker / microphone 124, keypad 126, and / or display / touchpad 128. In addition, the processor 118 can obtain information from and store data in any type of suitable memory, such as the non-removable memory 130 and / or the removable memory 132. The non-removable memory 130 can include a random access memory (RAM), read only memory (ROM), hard disk, or any other type of memory storage device. The removable memory 132 can include a subscriber identity module (SIM) card, memory stick, secure digital (SD) memory card, and the like. In other embodiments, the processor 118 can obtain information from and store data in a memory located on a server or home computer (not shown) rather than a memory physically located on the WTRU 102.

[0027] The processor 118 can receive power from the power supply 134 and can be configured to distribute and / or control the power to other components within the WTRU 102. The power supply 134 can be any suitable device for powering the WTRU 102. For example, the power supply 134 can include one or more dry cells (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium ion (Li-ion), etc.), solar cells, and fuel cells.

[0028] Processor 118 can also be coupled to a GPS chipset 136, which can be configured to provide location information (e.g., longitude and latitude) regarding the current location of WTRU 102. In addition to, or instead of, information from GPS chipset 136, WTRU 102 can receive location information on air interface 116 from a base station (e.g., base stations 114a, 114b), and / or can determine its location based on the timing of signals received from two or more nearby base stations. It will be understood that WTRU 102 can acquire location information using any suitable positioning method while maintaining compliance with one embodiment.

[0029] Processor 118 can further be coupled to other peripheral devices 138, which can include one or more software modules and / or hardware modules that provide additional features, functionality, and / or wired or wireless connectivity. For example, peripheral devices 138 can include an accelerometer, an e-compass, a satellite transceiver, a digital camera (for photos or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands-free headset, a Bluetooth® module, a frequency modulation (FM) radio unit, a digital music player, a media player, a video game player module, an Internet browser, etc.

[0030] FIG. 1C is a system diagram of RAN 104 and core network 106 according to an embodiment. As mentioned above, RAN 104 can utilize E-UTRA radio technology to communicate with WTRU 102a, 102b, 102c on air interface 116. RAN 104 can also communicate with core network 106.

[0031] RAN 104 can include eNodeBs 140a, 140b, 140c, but it will be understood that RAN 104 can include any number of eNodeBs while maintaining consistency with the embodiments. Each of eNodeBs 140a, 140b, 140c can include one or more transceivers for communicating with WTRUs 102a, 102b, 102c over air interface 116. In one embodiment, eNodeBs 140a, 140b, 140c can implement MIMO technology. Thus, eNodeB 140a can, for example, transmit a wireless signal to WTRU 102a and receive a wireless signal from WTRU 102a using multiple antennas.

[0032] Each of eNodeBs 140a, 140b, 140c can be associated with a particular cell (not shown) and can be configured to handle radio resource management decisions, handover decisions, user scheduling in the uplink and / or downlink, etc. As shown in Figure 1C, eNodeBs 140a, 140b, 140c can communicate with each other over the X2 interface.

[0033] The core network 106 shown in Figure 1C can include a Mobility Management Entity Gateway (MME) 142, a Serving Gateway 144, and a Packet Data Network (PDN) Gateway 146. Each of the above elements is shown as part of the core network 106, but it will be understood that any one of these elements can be owned and / or operated by a party different from the core network operator.

[0034] The MME 142 can be connected to each of the eNodeBs 140a, 140b, 140c within the RAN 104 via the S1 interface and can serve as a control node. For example, the MME 142 can be responsible for user authentication of the WTRUs 102a, 102b, 102c, bearer activation / deactivation, and selection of a specific serving gateway during the initial connection of the WTRUs 102a, 102b, 102c. The MME 142 can also provide control plane functions for exchanges between the RAN 104 and other RANs (not shown) that utilize other radio technologies such as GSM or WCDMA.

[0035] The serving gateway 144 can be connected to each of the eNodeBs 140a, 140b, 140c within the RAN 104 via the S1 interface. The serving gateway 144 can generally perform routing and forwarding of user data packets to / from the WTRUs 102a, 102b, 102c. The serving gateway 144 can also perform other functions such as user plane anchoring during handover between eNodeBs, triggering of paging when downlink data is available for the WTRUs 102a, 102b, 102c, and management and storage of the contexts of the WTRUs 102a, 102b, 102c.

[0036] The serving gateway 144 can also be connected to the PDN gateway 146, which can provide access to a packet switched network such as the Internet 110 to the WTRUs 102a, 102b, 102c and facilitate communication between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0037] The core network 106 can facilitate communication with other networks. For example, the core network 106 can provide access to a circuit-switched network such as the PSTN 108 to the WTRUs 102a, 102b, 102c to facilitate communication between the WTRUs 102a, 102b, 102c and conventional landline communication devices. For example, the core network 106 can include, or communicate with, an IP gateway (e.g., an IP multimedia subsystem (IMS) server) that serves as an interface between the core network 106 and the PSTN 108. In addition, the core network 106 can provide access to a network 112 to the WTRUs 102a, 102b, 102c, where the network 112 can include other wired or wireless networks owned and / or operated by other service providers.

[0038] Transmission Time Interval (TTI) bundling can enhance the uplink (UL) coverage for a user or a WTRU that experiences limited UL coverage, for example, as the transmission power approaches its maximum. Using TTI bundling, the same data can be transmitted in multiple consecutive TTIs, enabling the WTRU to expand the effective transmission time window for the data. For example, in the case of Frequency Division Duplex (FDD) LTE, up to four consecutive TTIs can be bundled, and the effective transmission time window can be expanded up to four times. In each of the consecutive subframes, a single transport block can be coded and transmitted using different redundancy versions (RVs), where subframes and TTIs can be used interchangeably. For example, consecutive RVs can be assigned to consecutive TTIs within the same TTI bundle. The same Hybrid Automatic Repeat reQuest (HARQ) process number can be assigned to all TTIs within the TTI bundle, and all TTIs within the TTI bundle can be treated as a single resource, to which a single UL grant and a single Acknowledgment / Negative Acknowledgment (ACK / NACK) (e.g., Physical HARQ Indicator Channel (PHICH)) can be associated. The TTI bundling mechanism can be configured by higher layer signaling for each WTRU. In FDD TTI bundling, any round trip time (RTT) of retransmission can be made equal to 16 ms. When FDD TTI bundling is activated, the WTRU can receive a UL grant for the first subframe within the TTI bundle according to the rules of FDD UL grants, and once UL data is transmitted within the TTI bundle, the WTRU can expect a PHICH or other UL grant according to the PHICH rules corresponding to the last subframe of that TTI bundle. The rules can be, for example, the rules of 3GPP Release 8.

[0039] Figure 2 is a diagram showing an example of TTI bundling where the TTI bundle consists of 4 consecutive TTIs. In the example, HARQ ID#0 includes 4 bundled TTIs 205, and ACK / NACK 210 is received 4 TTIs after the last TTI of TTI bundle 205, and a retransmission occurs 16 TTIs after the first TTI of the initial transmission. Once FDD TTI bundling is activated, the WTRU can support a certain number, e.g., up to 4 in the case of 3GPP Release 10, of HARQ processes. In FDD operation, all TTI bundles of the same HARQ process can have the same number of UL subframes, can have the same pattern (e.g., including consecutive UL subframes), and can be uniformly distributed in the time domain.

[0040] Figure 3 is a diagram showing an example of layer 2 (L2) processing 300 for an incoming data packet 305. Generally, the incoming data packet 305 can be processed through a packet data convergence protocol (PDCP) layer or entity 310, a radio link control (RLC) layer or entity 312, a media access control (MAC) layer or entity 314, and a physical (PHY) layer or entity 316. In the example, a PDCP header 320 is added to the incoming packet that is to be transmitted in the DL or UL direction. The example shown is simplified for low data rates, and the RLC layer 312 splits the PDCP protocol data unit (PDU) (e.g., into 3 RLC PDUs 325) so that each MAC PDU 330 can contain a single RLC service data unit (SDU) 325, but does not concatenate. In this way, the protocol header overhead for each layer can include a few bits, e.g., 1 bit, for data or control PDU indication, and can also include other bits, e.g., 7 bits, for a sequence number (SN), a PDCP header (e.g., 8 bits) 320, an RLC header having a size that can depend on the configured mode, e.g., whether unacknowledged mode (UM) is configured or acknowledged mode (AM) is configured, a MAC header having 5 bits for a logical channel ID (LCID), e.g., 8 bits, and a cyclic redundancy check (CRC) (e.g., 24 bits) that can be added to the end of the MAC PDU 330 before further processing in the PHY layer 316. Regarding the PDCP header 320, the SN can be used for sequential delivery of PDCP SDUs to higher layers and for hyperframe number (HFN) sequence management and encryption. Regarding the RLC header in the case of AM, it can include a 16-bit header, e.g., 10 bits of the header are for the SN. Regarding the RLC header in the case of UM, it can include an 8-bit header, e.g., 5 bits of the header are for the SN. The header can be applied to each split RLC SDU 325.

[0041] When a high data rate data radio bearer (DRB) is configured, for each protocol layer, a larger header can be configured. For example, the PDCP layer 310 and the RLC layer 312 can allocate a larger SN bit size in the header. The RLC layer 312 can concatenate or combine a plurality of RLC SDUs 325 into a single PDU, which can further increase the RLC header size. If the transport block size allocated for the transmission opportunity permits, the MAC layer 314 can multiplex a plurality of MAC SDUs into a single MAC PDU 335, and the MAC header can increase according to the number of MAC SDUs multiplexed into the MAC PDU 335.

[0042] The physical resources that can be used for the physical uplink control channel (PUCCH) can be given by two parameters from a higher layer

[0043]

Number

[0044] and

[0045]

Number

[0046] can depend on. The variable

[0047]

Number

[0048] can represent the bandwidth in units of resource blocks (RBs) that can be made available for use with a certain PUCCH format, such as format 2 / 2a / 2b, in each slot. The variable

[0049]

Number

[0050] can represent the number of cyclic shifts that can be used for a certain PUCCH format such as format 1 / 1a / 1b in an RB that can be used for mixing formats such as 1 / 1a / 1b and 2 / 2a / 2b.

[0051]

Number

[0052] The value of

[0053]

Number

[0054] can be an integer multiple, and the integer multiple can be in the range of {0, 1,..., 7},

[0055]

Number

[0056] can be provided by a higher layer. In an embodiment,

[0057]

Number

[0058] if it is, a mixed RB cannot be presented. In an embodiment, at most, only one RB within each slot can support the mixing of formats 1 / 1a / 1b and 2 / 2a / 2b. The resources that can be used for the transmission of a certain PUCCH format such as 1 / 1a / 1b, 2 / 2a / 2b, 3, etc. each have a non - negative index

[0059]

Number

[0060] 、

[0061]

Number

[0062] can be represented by

[0063] Complex numerical symbol

[0064]

Number

[0065] The block consisting of PUCCH can multiply the amplitude scaling factor β PUCCH in order to match with the transmission power P

[0066]

Number

[0067] can be mapped in order to the resource elements starting from

[0068]

Number

[0069] The mapping to the resource element (k, l) can be performed first in ascending order of k, then in ascending order of l, and finally in ascending order of the slot number starting from the first slot within the subframe. Slot n s The physical resource blocks used for PUCCH transmission in slot n are

[0070]

Number

[0071] which can be given by, where the variable m can depend on the PUCCH format. For formats 1, 1a, 1b, for example,

[0072]

Number

[0073] and for formats 2, 2a, 2b, for example,

[0074]

Number

[0075] and for format 3, for example,

[0076]

Number

[0077] are. Figure 4 is a diagram showing an exemplary mapping of modulation symbols for PUCCH.

[0078] In embodiments where only one serving cell can be configured and sounding reference signals (SRS) and PUCCH formats 1, 1a, 1b, or 3 can be transmitted simultaneously, a shortened PUCCH format can be used, and the last single carrier frequency division multiple access (SC-FDMA) symbol that can be present in the second slot of a subframe can be left blank. For PUCCH formats 1a / 1b, HARQ-ACK transmission on two antenna ports (p ∈ [p0, p1]) can be supported.

[0079] In embodiments of FDD where there is one configured serving cell, the WTRU can use a PUCCH resource for transmission of HARQ-ACK in subframe n, where

[0080]

Number

[0081] is mapped to the antenna port p for PUCCH formats 1a / 1b. In this embodiment, for example, for a physical downlink shared channel (PDSCH) transmission indicated by the detection of the corresponding physical downlink control channel (PDCCH) in subframe n - 4, or for a PDCCH indicating the release of a downlink semi-persistent scheduling (SPS) that can be present in subframe n - 4, the WTRU, for antenna port p0

[0082]

Number

[0083] is mapped to the antenna port p for PUCCH formats 1a / 1b. In this embodiment, for example, for a physical downlink shared channel (PDSCH) transmission indicated by the detection of the corresponding physical downlink control channel (PDCCH) in subframe n - 4, or for a PDCCH indicating the release of a downlink semi-persistent scheduling (SPS) that can be present in subframe n - 4, the WTRU, for antenna port p0

[0084]

Number

[0085] can be used, where n CCE can be the number of first control channel elements (CCEs) used for transmission of the corresponding DL control information (DCI) allocation (e.g., the lowest CCE index that can be used to form a PDCCH),

[0086]

Number

[0087] can be configured by a higher layer. For 2-antenna port transmission, the PUCCH resource for antenna port p1 is

[0088]

Number

[0089] can be given by. For PDSCH transmission on a primary cell where there may be no corresponding PDCCH detected in subframe n - 4,

[0090]

Number

[0091] The value of can be determined according to the configuration of a higher layer. For a WTRU configured for 2-antenna port transmission, the PUCCH resource value can be mapped to 2 PUCCH resources, and the first PUCCH resource

[0092]

Number

[0093] is for antenna port p0, and the second PUCCH resource

[0094]

Number

[0095] is for antenna port p1. Otherwise, the PUCCH resource value is a single PUCCH resource for antenna port p0

[0096] [Number]

[0097] can be mapped to.

[0098] PHICH can be used to transmit an ACK or NACK corresponding to the PUSCH transmitted in the UL subframe. PHICH can be transmitted in a distributed manner across the system bandwidth and across orthogonal frequency division multiplexing (OFDM) symbols within the DL control channel. The number of OFDM symbols can be defined as the PHICH duration and can be configurable via signaling from a higher layer. The physical resource position of PHICH can vary according to a PHICH duration that can be different from that of the physical control format indicator channel (PCFICH).

[0099] FIG. 5 is an exemplary diagram of PCFICH and PHICH resource element group (REG) allocation according to a physical cell identifier (PCI). In the example, a plurality of PHICH groups are defined within the cell, and a PHICH group can include a plurality of PHICHs using orthogonal sequences. In an embodiment, the PHICH for the WTRU is the lowest physical resource block (PRB) index (

[0100] [Number]

[0101] ) and the demodulation reference signal (DM-RS) cyclic shift (n DMRS) etc., can be dynamically defined using the resource information within the UL grant. Two index pairs (PHICH group index:

[0102]

Number

[0103] , PHICH sequence index:

[0104]

Number

[0105] ) can indicate the PHICH resources for a specific WTRU. The PHICH index pair (

[0106]

Number

[0107] ,

[0108]

Number

[0109] ) in which, each index can be

[0110]

Number

[0111]

Number

[0112] defined as such, where

[0113]

Number

[0114] can represent the number of PHICH groups available in the system,

[0115]

Number

[0116] can be defined as, where N g can be information (e.g., 2-bit information) and can be transmitted via a Physical Broadcast Channel (PBCH), and the information is such that N g ∈ {1 / 6, 1 / 2, 1, 2}. The orthogonal sequence according to the spreading factor can be, for example, as provided in Table 1.

[0117]

Table 1

[0118] The eNB and / or WTRU can use a random access procedure for at least one of (e.g., WTRU initial access to a cell or eNB), reset of UL timing (e.g., to reset or adjust the WTRU UL timing for a certain cell), and reset of timing during handover (e.g., to reset or adjust the WTRU timing for a handover target cell). The WTRU transmits a certain Physical Random Access Channel (PRACH) preamble sequence at a certain power P PRACHcan be transmitted, which can be based on configured parameters and / or measurements, and the WTRU can transmit a preamble using one or more time-frequency resources. The configured parameters, which can be provided or configured by the eNB, can include one or more of an initial preamble power (e.g., preamblelnitialReceivedTargetPower), a preamble format-based offset (e.g., deltaPreamble), a random access response window (e.g., ra-ResponseWindowSize), a power ramping factor (e.g., powerRampingStep), and a maximum number of retransmissions (e.g., preambleTransMax). (Can include a preamble or set of preambles, and / or the time / frequency resources that can be used for preamble transmission) The PRACH resources can be provided or configured by the eNB. The measurements can include path loss. The time-frequency resources can be selected by the WTRU from a permitted set, or selected by the eNB and communicated to the WTRU. After the WTRU transmits a preamble, the eNB can respond using a random access response (RAR) if the preamble was detected. If the WTRU cannot receive or does not receive an RAR for a transmitted preamble (e.g., corresponding to a certain preamble index and time / frequency resource) within the allocated time (e.g., ra-ResponseWindowSize), the WTRU can transmit another preamble at a higher power at a later time (e.g., powerRampingStep higher than the previous preamble transmission), and the transmission power is limited by the maximum power, e.g., generally the maximum power configured by the WTRU for the WTRU (e.g., P CMAX ), or the maximum power configured by the WTRU for a serving cell of the WTRU (e.g., P CMAX,c) can be restricted by. The WTRU can wait to receive the RAR from the eNB again. This sequence of transmission and waiting can continue until the eNB can respond using the RAR or until the maximum number of random access preamble transmissions (e.g., preambleTransMax) is reached. In response to a single preamble transmission, the eNB can send the RAR and the WTRU can receive the RAR.

[0119] A specific example of the random access procedure can be contention-based or contention-free. A contention-free procedure can be initiated by higher layer signaling such as a PDCCH order (e.g., via physical layer signaling such as from the eNB), or a request from the eNB, or can include mobility control information, e.g., indicating a handover request or corresponding to a handover request, such as an RRC reconfiguration message (e.g., an RRC connection reconfiguration message). For a contention-free procedure that can be initiated by a PDCCH order in subframe n, the PRACH preamble can be transmitted in the first subframe (or the first subframe available for the PRACH) n + k2, k2 ≥ 6. When initiated by an RRC command, other delays can be specified (e.g., there can be a minimum and / or maximum delay required or allowed). The WTRU can autonomously initiate a contention-based procedure for reasons that can include, for example, initial access, UL synchronization recovery, or recovery from a radio link failure. For an event, e.g., an event other than recovery from a radio link failure, it may not be defined or specified as to how long after such an event the WTRU can transmit a PRACH preamble.

[0120] In the case of a random access (RA) procedure without contention, the PRACH preamble transmitted by the network can be used. In the case of a contention-based random access procedure, the WTRU can autonomously select the preamble that the WTRU will use. The preamble format and / or the time / frequency resources available for preamble transmission can be based on an indication or index (e.g., prach-configIndex) provided or transmitted by the eNB.

[0121] It is essential in the LTE system design that the eNB can eventually detect one of the preambles transmitted with a gradually increasing transmission power. The RAR can be transmitted by the eNB in response to that one detected preamble.

[0122] The preamble format for PRACH can be defined in three parts: a cyclic prefix (T CP ), a preamble (T PRE ), and a guard time (T GT ). The total time including these three parts can be considered as the time for RA (T RA ). In the case of an FDD system, for example, as shown in Table 2 below which includes an exemplary preamble format for PRACH, several preamble formats, e.g., four preamble formats, can be supported.

[0123]

Table 2

[0124] In the example of Table 2, T SEQ can be made equal to T PRE + T GT , and Ts can represent the basic time unit (e.g., sample time). Preamble formats 2 and 3 have twice the T SEQ compared to the other two formats.It can have a length, whereby the signal power can be increased by repeating the preamble twice.

[0125] For example, in the IDLE mode, paging can be used for the connection setup of the WTRU initiated by the network. In the physical layer, paging can be transmitted using the PDCCH and PDSCH. A single paging radio network temporary identification information (P-RNTI) can be assigned to the paging channel (PCH). In the MAC, the HARQ process cannot be used for the PCH, and the RLC transparent mode (TM) can be applied to the paging control channel (PCCH). The RRC paging message can include individual WTRU indication or identification information about the specific WTRU being paged to initiate a connection, and / or a system information block (SIB), and / or a common indication about a change to a certain system information, including changes to information related to earthquake and tsunami warning systems (ETWS), commercial mobile alert systems (CMAS), and extended access barring (EAB).

[0126] For energy efficiency purposes, for example, a discontinuous reception (DRX) mechanism can be used together with paging so that the WTRU can conserve energy between the reception and reception of paging messages, which can be assigned to a single subframe per WTRU and per paging (DRX) cycle. The parameters for the DRX cycle can be configured via the system information block (SIB) or a higher layer. For example, the higher layer can be the non-access stratum (NAS) layer.

[0127] The paging opportunity for a given WTRU can be defined by, for example, WTRU identification information such as international mobile subscriber identity (IMSI), DRX cycle length, and a parameter “nB” set in the RRC layer. The value of nB can define the density of paging opportunities in a given cell, ranging from a paging frame and opportunity occurring every 32 frames (nB = T / 32) to four paging opportunities (nB = 4T) per paging frame, in sub - frames s{0,1,5,6} in the case of TDD or sub - frames s{0,4,5,9} in the case of FDD. The WTRU can receive its own paging record only during the assigned paging opportunities and can read indications of changes to broadcast information in other paging opportunities.

[0128] In some embodiments, certain terms can be used interchangeably. eNB, cell, and network can be used interchangeably. Serving cell and component carrier can be used interchangeably. Carrier and cell can be used interchangeably. One or more of message, command, request, and signaling can be used interchangeably. One or more of provide, convey, configure, and transmit can be used interchangeably. Send and transmit can be used interchangeably.

[0129] The WTRU can obtain cell and / or network related system information that can be used, for example, for cell selection, access, connection establishment, cell reselection, etc. The system information can be transmitted, for example broadcast, by the eNB or cell in groups or blocks. One or more of the Master Information Block (MIB), and / or one or more of the System Information Blocks (SIB), such as System Information Block type 1 (SIB1) and System Information Block type 2 (SIB2), can be provided by the eNB or cell and / or can be required by the WTRU for one or more functions such as cell access. The SIB can be carried in a System Information (SI) message, although exceptions such as SIB1 are possible. Each SIB can be included within a single SI message.

[0130] The MIB can be transmitted on the Physical Broadcast Channel (PBCH), and the PBCH can have a fixed schedule. For example, a PBCH such as the LTE legacy PBCH can be transmitted within subframe #0 of all radio frames. An MIB such as the legacy MIB can have periodicity within a radio frame (e.g., 4 frames or 40 ms) and can repeat in all radio frames (e.g., 10 ms) within the period (e.g., 40 ms). In each of the radio frames of the MIB period, one or more (one or more) information bits can be the same. In each of the radio frames of the MIB period, the encoded bits can be different. The physical resources of the PBCH can be fixed and can be the central 6 PRBs of the transmission band and can be arranged within 72 central subcarriers. The PBCH resources can be present within the first 4 symbols of the second time slot of the subframe. The information contained in the MIB can include one or more of at least a part of the System Frame Number (SFN) (e.g., the most significant 8 bits of the SFN), the configured DL bandwidth of the cell, and the PHICH configuration for the cell. By acquiring (e.g., successfully decoding) at least one of the MIBs repeated within the MIB period (e.g., 40 ms) (e.g., one of the 4 repeated MIBs), the WTRU can derive the least significant bits of the SFN (e.g., the 2 least significant bits) and combine it with the partial SFN contained in the MIB to obtain the full SFN value (e.g., the full SFN value of the frame in which the MIB decoding was successful). The term legacy PBCH can be used to represent a PBCH according to a certain standard or specification, such as one or more 3GPP LTE releases prior to a certain release, such as 3GPP LTE Release 10 (R10) or Release 11 (R11). The term legacy MIB can be used to represent an MIB according to a certain standard or specification, such as one or more 3GPP LTE releases prior to a certain release, such as 3GPP LTE R10 or R11.The term "legacy PRACH" can be used to represent PRACH according to a certain standard or specification, such as one or more 3GPP LTE releases prior to a certain release, such as 3GPP LTE Release 10 (R10) or Release 11 (R11). The term "legacy" can generally be used to represent or refer to a certain standard or specification, such as one or more 3GPP LTE releases prior to a certain release, such as 3GPP LTE Release 10 (R10) or, for example, Release 11 (R11).

[0131] SIB1 can be transmitted on the PDSCH within a certain subframe, such as subframe 5, can have a TTI of 80 ms, and can be repeated every 20 ms. The resource location of SIB1 can be indicated by a PDCCH scrambled with a system information radio network temporary identification (SI-RNTI). SIB1 can provide scheduling information about other SIBs in addition to the information that can be used by the WTRU to access the cell and the network.

[0132] SIB2 can be transmitted on the PDSCH based on the scheduling information contained in SIB1. The resource location can be indicated by a PDCCH scrambled with the SI-RNTI. SIB2 can provide the information that can be used by the WTRU to access the cell and the network and initiate connectivity therewith. The information in SIB2 can include, for example, a common channel configuration that provides a configuration for channels such as the PRACH and / or RACH, a multicast-broadcast single frequency network (MBSFN) subframe configuration, and / or UL information.

[0133] A scheduling information list for system information (SI) messages can also be used. Each SI listed within the scheduling information list can include one or more SIBs. The scheduling of SI can be based on the periodicity of the system information and the length of the SI window. The eNB can have some flexibility in terms of the time and frequency resources for transmitting the SIBs.

[0134] Other SIB information can relate to cell reselection information, multimedia broadcast multicast service (MBMS), or information related to an emergency and warning system (EWS) that the WTRU may need. The validity of the SIB for a cell can be based on the cell or network configuration and, if not valid, may not be transmitted by the cell.

[0135] A WTRU, such as a WTRU in RRC_CONNECTED mode, can continuously monitor (e.g., in every radio frame) the DL radio link quality. The WTRU monitors the quality of the DL radio link and can compare it with thresholds such as Q in and Q out In an embodiment, Q out can be defined as a quality level at which the DL radio link cannot be received with high reliability and can correspond to a 10 percent block error rate (BLER) for virtual PDCCH transmission. In an embodiment, Q in can be defined as a quality level at which the DL radio link can have significantly higher reliability than Q out and can correspond to a 2 percent block error rate (BLER) for virtual PDCCH transmission. The thresholds can be configured based on the reference signal received power (RSRP) measurement value, and the radio link monitoring can be performed on the primary cell (PCell) cell-specific reference signal (CRS).

[0136] Q incan be evaluated over an evaluation period, e.g., 100 ms, without DRX. If the radio link quality is better than Q in during the evaluation period, a synchronization match indication can be provided to a higher layer. Correspondingly, Q out can be evaluated over an evaluation period, e.g., 200 ms, without DRX. If the radio link quality is worse than Q out during the evaluation period, a synchronization mismatch indication can be provided to a higher layer.

[0137] The processing of the synchronization match or synchronization mismatch indication performed by the higher layer can be executed based on a radio link monitoring (RLM) counter or timer configured by radio resource control (RRC), which can be provided within system information such as SIB2. For example, consecutive synchronization mismatch indications N310 can start timer T310. In another example, consecutive synchronization match indications N311 while T310 is running can stop T310. In another example, when T310 expires, a radio link failure indication can be detected, and the WTRU can start an RRC re-establishment procedure. Timer T311 can be started at this point.

[0138] A radio link failure can be declared based on whether a physical layer problem, detection of a random access problem, or the radio link controller (RLC) indicating that the maximum number of retransmissions has been reached.

[0139] It may be desirable to improve the service coverage of a device or type of device, such as a low-cost machine type communication (MTC) (LC-MTC) device, e.g., an LTE or Long Term Evolution-Advanced (LTE-A) device, by, for example, up to a few dB (e.g., 15 or 20 dB) compared to the LTE cell coverage defined for other devices that may not be LC-MTC devices. In this case, the requirements for throughput and latency can be relaxed. For example, the message size can be limited to an order of up to 100 bytes per message in the UL and / or an order of up to 20 bytes per message in the DL. In another example, the latency can be relaxed to allow up to 10 seconds for the DL (e.g., for available DL data transmitted by the eNB and successfully received by the WTRU) and / or up to 1 hour for the UL (e.g., for available UL data transmitted by the WTRU and successfully received by the eNB). Such relaxation of requirements may make it impossible to support certain services such as voice.

[0140] In the embodiments described herein, a WTRU, device, LC WTRU, LC device, LC-MTC WTRU, LC-MTC, and LC-MTC device can be used interchangeably. The LC-MTC device is used as a non-limiting example. The embodiments described herein can be applicable to other devices that can benefit from an extended coverage and can tolerate relaxed throughput and / or latency requirements.

[0141] In some embodiments, a legacy WTRU can be defined as a WTRU that can comply with a certain release or version, such as a 3GPP or LTE standard release or version. For example, a WTRU that can comply with a 3GPP or LTE standard release that is prior to a certain release, such as Release 8, Release 9, or Release 10, can be considered a legacy WTRU. A legacy WTRU can be a WTRU that can or cannot support a certain functionality. For example, a legacy WTRU can be a WTRU that cannot support a certain coverage enhancement technique that can be introduced for a certain device, such as an LC-MTC device or an LC-MTC device with limited coverage.

[0142] In the case of the Physical Uplink Shared Channel (PUSCH), TTI bundling can be supported in up to four consecutive subframes (e.g., 4 ms), which can provide a coverage improvement of up to 6 dB. To achieve further coverage enhancements, such as up to 15 or 20 dB, additional techniques can be supported for the PUSCH. Since TTI bundling in the DL PDSCH has not been supported heretofore, the coverage of the DL shared channel (PDSCH) can also be improved.

[0143] The segmentation function in the RLC layer can enable smaller segmented data to be transmitted using increased energy per bit. However, the layer 2 (L2) header overhead added to each segmented data can limit the coverage enhancement gain provided by the segmentation. The overhead added by the L2 protocol header can further reduce these gains.

[0144] When the coverage of the shared channel in both UL and DL is improved, the coverage of the associated HARQ ACK channel may also need to be improved accordingly to support the HARQ process.

[0145] Coverage may deteriorate not only for data channels but also for control channels. Since control channels can be received for data channel transmission and / or reception (e.g., to indicate resources and parameters), it may be necessary to enhance not only data channel coverage but also control channel coverage.

[0146] When a WTRU is troubled by a low received signal-to-interference and noise ratio (SINR), at least, since signal integration can increase the received SINR, a PBCH such as a legacy PBCH can be transmitted 4 times over 40 ms so that the WTRU can integrate signals within a 40 ms window size. However, at least, since the SFN that can be carried by the PBCH (e.g., in the MIB) can change every 40 ms, physical broadcast channel signal integration beyond 40 ms may not be possible. PBCH coverage enhancement techniques can be considered.

[0147] PBCH coverage can affect SFN acquisition, which can in turn affect cell access and other procedures that rely on frame-level timing for LC-MTC devices. Improvements for determining the SFN can be considered. Additionally, LC-MTC specific system information acquisition can be considered for further coverage enhancement.

[0148] The eNB can ultimately detect and respond to a power-ramped preamble transmission from the WTRU. LC-MTC devices may experience much higher path losses (e.g., up to 20 dB) than expected in the LTE system design. In the case of LC-MTC devices experiencing such high path losses, the eNB may not be able to detect any ramped preambles, including those transmitted using maximum transmit power, and may not be able to respond to any of them. Therefore, methods and procedures for random access procedures for devices such as LC-MTC devices that may experience very high path losses may be desirable.

[0149] The paging channel configuration may not include a HARQ process, and therefore, no benefit can be obtained from retransmission. The PCCH can operate in RLC TM and can obtain additional gains from the RLC segmentation process. A method for the PCH to benefit from signaling accumulation for coverage enhancement gain may be desirable.

[0150] To improve the coverage of channels such as enhanced (enhanced) PDCCH (EPDCCH), PDSCH, and PUCCH, iterative transmission can be considered as a coverage enhancement technique. In this case, since the reference subframe can be redefined between the subframes transmitted iteratively, the current HARQ process, such as the n+4 timing relationship (in the case of FDD), cannot be used. In addition, the timing relationship between the UL grant and the PUSCH transmission can also be redefined using the new reference subframe n. The term (E)PDCCH can be used to mean PDCCH and / or EPDCCH, which can also be represented by PDCCH / EPDCCH.

[0151] A method for enhancing service coverage of data channels in UL and DL is described herein. If the LC-MTC WTRU has a high delay tolerance and can support a very low data rate with respect to service quality, the WTRU can shorten the size of each protocol layer header for each transport block that the WTRU can receive and / or transmit.

[0152] In an exemplary embodiment, PDCP and RLC can allocate a smaller sequence number (SN) size within the header. In PDCP, the WTRU can allocate an SN size smaller than 7 bits. In RLC, the WTRU can allocate an SN size smaller than 5 bits in the case of UM and smaller than 10 bits in the case of AM. The WTRU can adjust the size of the RLC and PDCP PDUs such that the resulting PDU having a header part and a data part can maintain octet (byte) alignment. The WTRU can have a PDCP PDU that is not byte-aligned, but the RLC header and PDU can be processed such that the resulting RLC PDU byte alignment can be maintained.

[0153] In another exemplary embodiment, the WTRU may not include an extended (``E'') field in MAC and RLC, thereby further reducing the header size. For example, the WTRU can be configured for a data radio bearer (DRB) with a very low data rate such that small data packets (e.g., 100 bytes in the UL) can arrive at the PDCP at a low frequency (e.g., once per hour). In that case, the WTRU can be configured with a small SN size in the PDCP, such as 2 bits, so that the sequence number can range from 0 to 3. In the RLC, the WTRU can be configured for UM, the RLC SDU can be split into 8 smaller RLC PDUs, and in relation thereto, the RLC SN size can be specified to 3 bits. Further, since the RLC SDU and MAC SDU may be concatenated and may not fit into the RLC and MAC PDUs (e.g., 1 PDU per SDU), the WTRU can exclude the RLC or MAC ``E'' bit in the header. In that case, the WTRU can perform L1 processing of the resulting MAC PDU for UL transmission. Given the reduced header size, the PDCP can have a header size reduced to 3 bits, an RLC header size reduced to 6 bits, and a MAC header size reduced to 7 bits. The WTRU and eNB can apply the same shortening of the protocol header also in the DL.

[0154] As part of the DRB setup procedure, the WTRU can be configured using shortened PDCP, RLC, and MAC header configurations that can be signaled by the RRC. For example, as part of the RRC procedure, the WTRU can be signaled to apply a 2-bit SN length in PDCP, a 3-bit SN length for UM mode RLC, and apply bits to indicate exclusion of the "E" bit in the MAC header. The WTRU can use a default or pre-defined set of MAC, RLC, and PDCP configurations, which can include exemplary header configurations defined in the RRC. The WTRU can be explicitly signaled by the network to use coverage enhancement mode protocol layer parameters, or the WTRU can autonomously use coverage enhancement mode parameters and signal their use to the network.

[0155] In another exemplary embodiment, the WTRU / eNB can shorten the RLC header size by scrambling the CRC bits applied to the MAC PDU that includes the SN of the RLC PDU. In that case, the WTRU can remove the SN from the RLC header. For example, independently or in combination with RLC SN size shortening, the WTRU can descramble the CRC parity bits using possible SN values when receiving a MAC PDU, prior to performing a CRC check. The WTRU can perform the descrambling based on the entire possible SN range, or based on the current RLC receiver window excluding already received SNs. When the correct SN is identified and the MAC PDU is correctly received, the WTRU can pass the determined SN value to the RLC for appropriate PDU processing.

[0156] In another exemplary embodiment, the WTRU can scramble CRC parity bits using MAC LCID information. For example, the WTRU can use the 5-bit LCID information of the DRB to scramble the CRC parity bits if, for example, there is a single LCID associated with the MAC SDU multiplexed in the MAC PDU.

[0157] In another exemplary embodiment, the WTRU can transmit and receive data on a DRB in a single HARQ process for the UL and / or DL directions. For example, if an LC-MTC WTRU has a high tolerance for delay and can transmit and receive data at a very low data rate, the WTRU can use a single HARQ process in each of the UL and / or DL directions. Since the WTRU only receives a single MAC PDU at a time, it can reduce the burden of maintaining sequence numbers in both the RLC layer and the PDCP layer, and further support the SN size shortening described above.

[0158] In another exemplary embodiment, the WTRU can shorten the CRC size using a multi-step CRC attachment and calculation procedure. Here, the WTRU can reduce the overhead from the attachment of CRC parity bits to the data. To transmit data, the WTRU can calculate long CRC parity bits in the RLC layer and attach them to the RLC SDU before the segmentation / concatenation procedure. Then, the WTRU can segment the RLC SDU with the CRC parity bits attached at the end. The WTRU can calculate a shorter set of CRC parity bits in the physical layer and attach them to each MAC PDU before transmission. To receive data, the WTRU can receive the MAC PDU in the MAC layer and, if the CRC is calculated correctly, consider the reception successful and deliver the corresponding MAC SDU to the RLC.

[0159] In the RLC layer, when the WTRU receives an RLC PDU and successfully reconstructs the RLC SDU, it can perform a CRC check based on the long CRC calculation and parity bits applied to the RLC SDU. Based on the result of the CRC check, if the CRC check is passed, the WTRU can deliver the RLC SDU to the PDCP. If the CRC check fails, the WTRU can discard the SDU and related PDUs if, for example, the WTRU is configured for RLC UM, or it can discard the SDU and provide an indication to the transmitter side to request retransmission of the related PDUs. For example, if the WTRU is configured for RLC AM, the WTRU can provide an RLC STATUS PDU indicating the SN of the RLC PDU that can be part of the discarded RLC SDU.

[0160] In an exemplary embodiment, the WTRU can attach a 24-bit CRC to the RLC SDU before segmentation in the RLC. For the purposes of this example, the RLC SDU could be segmented into 8 RLC PDUs. The WTRU can then attach an 8-bit CRC to the MAC PDU that can contain the previously segmented RLC SDU. Compared to attaching a 24-bit CRC to each MAC PDU, which results in a CRC overhead of 24×8 = 192 bits, the above-described CRC attachment procedure can result in a CRC overhead of 24 + 8×8 = 88 bits. For example, if the number of RLC PDUs to be segmented increases, the CRC overhead can be further reduced.

[0161] A method for providing coverage enhancement using TTI bundling is described herein. TTI bundling can be used because it can provide a higher received signal-to-noise ratio (SNR).

[0162] In an embodiment, when the WTRU is configured to use a coverage enhancement mode of operation, TTI bundling using a TTI longer than 4 can be used, and the number of subframes for TTI bundling can be predefined or configured. Additionally, the subframes to be bundled can be repeatedly transmitted over time, which can further enhance the coverage. For example, N TTI subframes are bundled and N TTI subframes are repeatedly transmitted (N rep times), effectively, a total of N TTI × N rep subframes can be used. The broadcast channel can include an indication regarding the capacity of the coverage enhancement mode of operation so that a WTRU capable of entering the coverage enhancement mode can select the coverage enhancement (enhanced) mode or report a preferred mode of operation (e.g., the coverage enhancement mode) according to conditions.

[0163] One or more of the following are the bundling size (N TTI ) and / or the repetition rate (N rep) can be applied. In an example, the bundling size and / or the repetition rate can be configured via a higher layer together with the transmission mode configuration. In another example, default values for the bundling size and / or the repetition rate for the coverage enhancement mode can be defined, and when the WTRU is configured for the coverage enhancement mode or enters the coverage enhancement mode, the default values can be used until the WTRU receives a WTRU-specific configuration for the bundling size and / or the repetition rate. In this case, the default value can be the maximum value among the candidate values, or the WTRU can start receiving the PDSCH using the default value and can perform a certain number of attempts to receive the PDSCH. If the WTRU fails to receive the PDSCH, the WTRU can increase the bundling size and / or the repetition rate using a specific step size. The step size can be predefined and can be the same regardless of the number of failures, or can be different according to the number of failures. In another example, TTI bundling and repetition can be used together, and HARQ-ACK cannot be reported until the last bundled TTI is received within the number of repetitions.

[0164] In another embodiment, up to N TTI subframes can be supported for TTI bundling, and the N TTI subframes can be configured by the eNB in a semi-static manner. In the embodiments described herein, subframes, TTIs, and ms can be used interchangeably.

[0165] The WTRU can transmit / receive the same data within N consecutive TTI subframes, and the data can be coded using different redundancy versions (RVs) according to the subframe index or the position of the subframe among the bundled subframes.

[0166] FIG. 6 shows an exemplary cyclic RV assignment where the RV order is {0, 1, 2, 3}. The RV can cyclically change in the order of {0, 1, 2, 3} within the window. For example, when using an 8 TTI window size, if 6 subframes (605) are bundled as shown in the example of FIG. 6, the RV can be used in the order of {0, 1, 2, 3, 0, 1}. For other WTRUs not configured using TTI bundling, when 8 HARQ processes are used, an 8 ms window size can be used. The window size may not be defined, and thus, the maximum N TTI can be equal to or less than 8, but it is possible to bundle any subframe.

[0167] FIG. 7 shows an exemplary cyclic RV assignment where the RV order is {0, 2, 1, 3}. The RV can cyclically change in the order of {0, 2, 1, 3} within the window. For example, when an 8 TTI window size is used, if 6 subframes (705) are bundled, the RV can be used in the order of {0, 2, 1, 3, 0, 2}. In this case, the RV order {0, 2, 1, 3} can only be used for DL TTI bundling. The RV order {0, 2, 1, 3} can be used when N TTI is greater than a threshold (for example, the threshold can be 4) (otherwise, the RV order {0, 1, 2, 3} can be used). The RV order {0, 2, 1, 3} can be replaced with another RV order such as {1, 3, 0, 2}. For transmission to and / or reception from one or more WTRUs, two or more RV orders (for example, RV orders {0, 1, 2, 3} and {0, 2, 1, 3}) can be used. For example, one RV order (for example, RV order {0, 1, 2, 3}) can be used in the initial transmission, and the other RV order (for example, RV order {0, 2, 1, 3}) can be used for retransmission.

[0168] FIG. 8 is a diagram illustrating an exemplary cyclic RV allocation without a window size. In the case of retransmission, the RV can cyclically change in an RV order without a window size. For example, if an RV order {0, 1, 2, 3} is used and six subframes (805) are bundled, for an initial transmission, RV-{0, 1, 2, 3, 0, 1} can be used, and for a first retransmission, RV-{2, 3, 0, 1, 2, 3} can be used. In the example shown in FIG. 8, when the maximum N TTI is equal to 8 or less, the window may not be defined. The WTRU may not be able to transmit / receive any common data within a subframe not configured for TTI bundling.

[0169] The WTRU can transmit / receive the same data in N TTI subframes within the window, and the data can be coded using different RVs according to the subframe index or the position of the subframe among the bundled subframes. The N TTI bundled subframes can be defined as any subset of the subframes within the window. In this case, the window size (N window ) can be defined, and / or the subset of subframes for TTI bundling can be indicated using a bitmap within the window, and the bitmap can be signaled via higher layer signaling.

[0170] The window size (N window ) can be defined as at least one of a positive integer (which can have a fixed value such as 8), a positive integer (which can be configured via higher layer signaling), a positive integer (which can be defined as a function of at least one of the system parameters), or a WTRU identification number (which can be the C-RNTI or the IMSI).

[0171] FIG. 9 is a diagram showing an example of TTI bundling having a bitmap display. A subset of subframes for TTI bundling 905 can be indicated by using a bitmap within a window, and the bitmap can be signaled via higher layer signaling.

[0172] TTI bundling can support up to N TTI subframes, and N TTI can be configured in a dynamic manner by the eNB. Here, the WTRU can be configured using a specific transmission mode that dynamically supports TTI bundling. For example, a new transmission mode (e.g., TM-x) and a related new DCI (e.g., DCI format IE) can be defined. In the new DCI format, for each DL / UL data transmission, N TTI can be defined such that it can include display bits for TTI bundling, and the WTRU can transmit / receive data N TTI times according to the display.

[0173] A set of TTI bundling cases can be defined via higher layer signaling, and the display bits within the DCI format can indicate one of the bundle sizes within the set. For example, four TTI bundling cases are {Ν TTI,1 =1, Ν TTI,2 =4, Ν TTI,3 =6, Ν TTI,4When defined as =8}, two bits in the DCI format can be used, for example, for indication, to notify which TTI bundling case is used for UL and / or DL grants. The set of TTI bundling cases can be pre-defined and fixed for all WTRUs so that higher layer signaling need not define a set of TTI bundling cases. Indication bits can still be used to indicate which TTI bundling case is used for UL and / or DL grants. Irrespective of the transmission mode configured for PUSCH / PDSCH transmission, the WTRU can be configured to use TTI bundling dynamically. The WTRU may not monitor the (E)PDSCH for PDSCHs including DCI format 1A / 2 / 2A / 2B / 2C in a subframe in which the WTRU can receive the PDSCH as a TTI-bundled subframe. For example, if the WTRU receives a DCI including a TTI bundling indication (N TTI ) and the TTI bundling indication indicates N TTI =3, the WTRU receives the PDSCH in the bundled TTIs from subframe n to subframe n+2, and the WTRU need not monitor the (E)PDSCH in subframes n+1 and n+2.

[0174] HARQ processing using TTI bundling is described herein. In an embodiment, the bundled TTI can have a single HARQ_ACK, and the WTRU can transmit / receive a HARQ_ACK after receiving / transmitting a bundled TTI for PDSCH / PUSCH. When TTI bundling is used in the DL, the WTRU can transmit a HARQ_ACK. If the downlink subframe n is the last subframe within a bundled subframe associated with a PDSCH, the WTRU can transmit a HARQ_ACK in the UL subframe n + k. Here, k can be defined as a fixed positive integer such as k = 4. If the downlink subframe n includes a PDCCH or EPDCCH associated with a grant for a PDSCH, the WTRU can transmit a HARQ_ACK in the UL subframe n + k. In this case, k is a function of N TTI (e.g., k = N TTI + 4).

[0175] The subframe n can be a subframe that includes a PDCCH or EPDCCH associated with a grant for a PDSCH. Here, k is a function of the bundling window N window (e.g., k = N window + 4).

[0176] If the WTRU successfully receives a PDSCH of a bundled DL transmission, the WTRU can transmit a HARQ_ACK corresponding to the bundled DL transmission.

[0177] When the WTRU receives the PDSCH within a time window of x ms (e.g., 8 ms), it can transmit HARQ_ACK in UL subframe m. A single PDSCH can be transmitted on one or more (one or more) subframes within the time window of x ms. Subframe m can be a predefined subframe, which can be arranged within the next radio frame of the last subframe of the window in which the corresponding PDSCH is transmitted. The PUCCH resource for HARQ_ACK transmission can be defined as a function of the first CCE and / or enhanced CCE (ECCE) index of the PDCCH / EPDCCH associated with the PDSCH. Alternatively, the PUCCH resource can be defined via higher layer signaling. The term (E)CCE can be used to mean CCE and / or ECCE, which can also be represented by CCE / ECCE.

[0178] When TTI bundling is used in UL, the WTRU can receive HARQ_ACK. The WTRU can receive HARQ_ACK in DL subframe n + k. UL subframe n can be the last subframe within the bundled subframes associated with the PUSCH transmission. Here, k can be a fixed number such as 4. DL subframe n can be the subframe in which the WTRU receives the grant for the PUSCH it is associated with. Here, k can be a function of the bundling size or the bundling window. For example, k = N TTI + 4, or k = N window + 4.

[0179] The bundled TTI can have two or more HARQ_ACKs so that the WTRU can accumulate multiple HARQ_ACKs to improve coverage. The WTRU can assume that all of the individual subframes within the bundled subframe can have associated HARQ_ACKs in subframe n+k, and that multiple HARQ_ACKs can have the same HARQ indicator (HI) code so that the WTRU can add multiple HARQ_ACKs to improve coverage. Multiple HARQ_ACKs for the bundled subframe can be used when N TTI is greater than a threshold. For example, when N TTI is greater than 4, the WTRU can assume that multiple HARQ_ACKs are transmitted.

[0180] The WTRU can assume that a subset of the subframes within the bundled subframe can have associated HARQ_ACKs. The WTRU can assume that the subset of subframes has the same HI code. In an embodiment, multiple HARQ_ACKs can be used for the bundled subframe when N TTI is greater than a threshold. For example, when N TTI is greater than 4, the WTRU can assume that multiple HARQ_ACKs are transmitted.

[0181] FIG. 10 is a diagram illustrating exemplary behavior of a legacy WTRU in the case of an ACK / NACK repetition embodiment. ACK / NACK repetition was introduced in LTE to enhance coverage for cell-edge WTRUs that may be subject to power limitations and / or inter-cell interference. More specifically, when configured as such, the legacy WTRU has N ANRep- In one consecutive subframe, ACK / NACK information can be repeatedly transmitted. Regarding the HARQ timeline with ACK / NACK repetition enabled, when a PDSCH transmission is detected in subframe n-4 (1005), if the WTRU does not repeat the transmission of HARQ_ACK in subframe n corresponding to the PDSCH transmission in subframes n-N ANRep -3,..., n-5, the legacy WTRU can transmit HARQ_ACK responses in N ANRep consecutive subframes starting from subframe n (1010). The legacy WTRU does not have to transmit HARQ_ACK responses corresponding to any detected PDSCH transmissions in subframes n-3,..., n+N ANRep -5 either.

[0182] Figure 11 is a diagram showing an example of ACK / NACK repetition for DL subframe bundling. In an embodiment where subframe bundling is used in the DL to improve DL coverage, the WTRU can repeat the transmission of a single HARQ_ACK response corresponding to all PDSCH transmissions within a bundle on the UL. Therefore, the WTRU can first collect and decode all PDSCH transmissions within the DL subframe bundle and then generate a single HARQ_ACK response for transmission on the UL. Regarding the UL ACK / NACK timing, according to an embodiment, when the WTRU detects a PDSCH transmission within subframe n-l (1105) addressed to the WTRU (where l is the index of the subframe within the DL subframe bundle), the WTRU transmits the first HARQ_ACK response in UL subframe n (1110) and then can repeat the HARQ_ACK response in subframes n+1,..., n+N ANRep -1 (1115). In the example shown in Figure 11, the index l is 3, 4, or 5, and the size of the DL subframe bundle is 3.

[0183] In the case of PDSCH transmission detected in a subframe within a DL subframe bundle for which there is a corresponding (E)PDCCH, the WTRU may transmit the first ACK / NACK response corresponding to the entire DL bundle transmission in UL subframe n, and then use the PUCCH resource derived from the (E)CCE index of the corresponding (E)PDCCH detected within the bundled subframes to transmit the ACK / NACK response corresponding to the entire DL bundle transmission in subframes n+1, ..., n+N ANRep -1. Thus, for all subframes within a DL subframe bundle, the WTRU can first detect the (E)PDCCH within that subframe and then derive the PUCCH index for ACK / NACK repetition in the corresponding UL subframe based on the lowest (E)CCE index used to configure the corresponding DCI assignment.

[0184] The WTRU may use the PUCCH resource derived from the (E)CCE index of the (E)PDCCH detected in the last subframe of the bundle, the PUCCH resource derived from the (E)CCE index of the (E)PDCCH detected in the first subframe of the bundle, or the PUCCH resource configured by higher layer signaling to transmit the ACK / NACK response corresponding to the entire DL transmission in subframes n+1, ..., n+N ANRep -1.

[0185] In the case of PDSCH transmission not detected in a subframe in which the corresponding (E)PDCCH is bundled, the WTRU may transmit the first ACK / NACK response corresponding to the entire DL bundle transmission in UL subframe n, and then use the PUCCH resource derived from the (E)CCE index of the (E)PDCCH detected in the most recent DL scheduling assignment, or the PUCCH resource configured by higher layer signaling, to transmit the ACK / NACK response corresponding to the entire transmission in subframes n+1, ..., n+N ANRep and repeat on - 1.

[0186] In LTE, ACK / NACK repetition can be limited to a repetition factor of 4 to enhance UL coverage. The WTRU may need to re - transmit the ACK / NACK response using a higher repetition factor. The enhanced repetition factor used by the WTRU can be signaled to the WTRU through higher layers or can be implicitly derived based on the subframe bundling parameters used in the DL. For example, this can be indicated by the number of DL subframes in the bundle or as a function of the number of DL subframes in the bundle.

[0187] Methods that can be used by the WTRU to improve PHICH coverage in the DL are described herein. The methods or embodiments can be utilized alone or in combination with each other.

[0188] In a PHICH repetition embodiment, the WTRU can receive and detect ACK / NACK (A / N) information associated with UL PUSCH transmission using multiple PHICH resources. In this embodiment, the ACK / NACK information transmitted on the PHICH can be associated with UL PUSCH transmission on a single subframe. In the case of subframe bundling operation, the ACK / NACK feedback can be associated with bundled PUSCH transmissions on multiple subframes. The ACK / NACK feedback can also be distributed across multiple subframes or within a single subframe. This can be different from legacy WTRU operation where the WTRU can process a single PHICH resource for a given subframe corresponding to a single UL transport block.

[0189] Regarding the PHICH resources, the WTRU can determine the corresponding PHICH resources from the physical resource block (PRB) index of the UL resource allocation. The PRB index can be associated with the PRBs used for PUSCH transmission within a single subframe. Here, for a given subframe, the WTRU determines the first PHICH resource using the lowest PRB index and then determines the other allocated PHICH resources within that subframe by sequentially incrementing the PRB index that constitutes the UL resource allocation based on the configured PHICH repetition factor.

[0190] Thus, the PHICH resources can be identified by an index pair (

[0191]

number

[0192] ), where

[0193]

number

[0194] can be the PHICH group number for the i-th PHICH resource,

[0195] [Number]

[0196] can be the orthogonal sequence index within the group, and they are

[0197] [Number]

[0198] can be defined by, where

[0199] [Number]

[0200] is, and N PHICHRep is the PHICH repetition factor.

[0201] In the case of subframe bundling operation, the PHICH resource can be derived from the PRB index associated with UL transmission on multiple UL subframes within the bundle. This approach can be different from that of legacy WTRU behavior where the corresponding PHICH resource is exclusively associated with the last subframe within the bundle.

[0202] Regarding the PHICH resource, the WTRU can determine the corresponding PHICH resource from the UL demodulation reference symbol (DMRS) cyclic shift associated with the PUSCH transmission. The DMRS cyclic shift can be associated with the PUSCH transmission within a single subframe. Here, for a given subframe, the WTRU uses the cyclic shift from the DMRS field in the most recent PDCCH to determine the first PHICH resource, and then can determine the other allocated PHICH resources within that subframe by sequentially increasing the cyclic shift. However, there may be a limit of up to eight cyclic shifts that can be used by the WTRU. Therefore, the PHICH resource can be identified by an index pair (

[0203] [Number]

[0204] ), where

[0205] [Number]

[0206] can be the PHICH group number for the i-th PHICH resource, and

[0207] [Number]

[0208] can be the orthogonal sequence index within the group, and they can be defined by (

[0209] [Number]

[0210] ), where

[0211]

Number

[0212] and N PHICHRep is the PHICH repetition factor.

[0213] In embodiments of PHICH power boosting, power control can be applied to the PHICH according to the channel state of the WTRU. The power boosting, together with the ACK / NACK repetition using multiple PHICH resources, can significantly enhance the coverage of the PHICH.

[0214] For a PHICH that does not perform code division multiplexing (CDM), a legacy PHICH group can include multiple PHICH resources that are code division multiplexed and mapped to the same set of resource elements. This can result in power distribution across multiple PHICH resources at the transmitter. Further, due to channel estimation errors in the WTRU, orthogonality between the code division multiplexed PHICH resources within a PHICH group may be lost, which may cause coverage degradation in the future. In an embodiment, the WTRU can assume that there is only one PHICH resource utilized within a PHICH group without any code division multiplexing.

[0215] In an embodiment, a PHICH or a group of PHICHs can be transmitted using an enhanced PHICH (EPHICH). For example, a new DCI format can be defined to carry information about a PHICH or a group of PHICHs. In another example, a DCI containing A / N information can be transmitted at a specific (E)PDCCH location that includes an (E)PDCCH common search space. Alternatively, a DCI containing A / N information can be transmitted in a pre-defined (E)CCE or an (E)CCE composed of a higher layer. In another example, a new RNTI can be defined for the detection of a DCI containing A / N information. For example, a HARQ RNTI (HA-RNTI) can be defined, and a WTRU can monitor, in subframe n + k, a DCI containing corresponding A / N information that can be used to scramble its CRC using the HA-RNTI when the WTRU transmits a PUSCH in subframe n, where k can be 4 in the case of FDD.

[0216] The position of the A / N information bits for a WTRU transmitting a PUSCH in subframe n can be defined and can include at least one of the starting (E)CCE number of the corresponding UL grant, the starting PRB number for PUSCH transmission, the cyclic shift of the uplink DM-RS, or a value composed of a higher layer. The number of DCIs containing A / N information can be configured as the number of PHICH groups.

[0217] A coverage enhancement method for improving the coverage of (E)PDCCH that carries DCI including A / N information is described herein. (E)PDCCH is used for DL / UL grants, broadcast channel transmission, paging, RACH response, group power control, etc. DCI formats have been introduced to support various DL / UL transmission modes, such as DCI format 0, 4 for UL grants, DCI format 1A, 1B, 1C, 2A, 2B, 2C for DL transmission, and DCI format 3, 3A for group power control. The embodiments described herein can be applied to both PDCCH and EPDCCH, or can be applicable to only either PDCCH or EPDCCH. Terms commonly used with respect to PDCCH, such as CCE, resource element group (REG), PDCCH candidate, and search space, can be used interchangeably with ECCE, enhanced (enhanced) REG (EREG), as well as EPDCCH candidate, and search space.

[0218] In an embodiment, the DCI content can be downsized for better coverage. Since (E)PDCCH link adaptation can be based on the number of (E)CCEs, the number of (E)CCEs may be closely related to the coverage of (E)PDCCH. For example, one CCE can be equivalent to a coding rate of 1 / 2. Thus, two CCEs can be equivalent to a coding rate of 1 / 4 since twice the number of (E)PDCCH resources are used for DCI transmission. Since there are four available CCE aggregation levels (e.g., {1, 2, 4, 8}), reduction of the DCI content can increase the coverage of (E)PDCCH at a given (E)CCE aggregation level.

[0219] For example, for this category of WTRUs, a new DCI format associated with DL transmission and / or UL grant can be defined. For the HARQ process number indication, 2 bits or less can be used, which implies that the number of HARQ processes can be reduced from 8 HARQ processes. The HARQ process number field may not be included in the DCI, and a single HARQ process or synchronous HARQ processes may be used. For the modulation and coding scheme (MCS) indication, 4 bits or less can be used. Assuming that N bits (N < 5) can be used for the MCS, the most significant bit (MSB) of the 5-bit MCS table can be inferred at the receiver, and the least significant bit (LSB) can be regarded as predefined bits. For example, in the new DCI format, a 3-bit MCS field (N = 3) can be used, and the 3 bits correspond to the first 3 bits of the MCS table, and the 2-bit LSB can be predefined as "00". Thus, 3 bits of the MCS table can be used together with the 3-bit MCS field, and the WTRU can interpret the 3-bit MCS field as xxx00, where xxx is the MSB of the 5-bit MCS field and "00" is the 2-bit LSB. Alternatively, the 3-bit MCS field can be regarded as part of the LSB, and the MSB can be predefined. For either alternative, the LSB part or MSB part of the 5-bit MCS field not indicated by the 3-bit MCS field in the new DCI format can be predefined or configured by higher layer signaling and / or broadcast.

[0220] The new MCS table can be defined using the N-bit MCS field, and the new MCS table can be defined using a subset of the 5-bit MCS table of the previous release.

[0221] Resource allocation bits according to a resource allocation type (0, 1, and / or 2) can be reduced by limiting the maximum number of PRBs used for PDSCH transmission. For example, assuming that 25 PRB pairs are available in the DL system bandwidth, the resource allocation indication can require within a limited number of PRB pairs, such as 6 PRB pairs instead of 25 PRBs, for example, so that the number of bits for resource allocation can be reduced. The maximum number of PRBs allocated in a subframe can be limited to 6 PRB pairs. Alternatively, in a new DCI format, the resource allocation field can be not used, and instead, signaling of a higher layer can be used. Thus, DL resource allocation in the frequency domain can be semi-static allocation, while time allocation can be based on (E)PDCCH. For example, a WTRU can receive a PDSCH or EPDCCH in a configured PRB pair among the PRB pairs in the system, while the WTRU can be indicated whether to receive a PDSCH in a subframe via (E)PDCCH.

[0222] The redundancy version can be removed or downsized in a new DCI format. For example, the redundancy version can be fixed to "0", and the bit field for the redundancy version may not be used. Assuming that a lower coding rate can be used for the new DCI format to support better coverage, other redundancy versions {i.e., 1, 2, and 3} may not be required, and a single redundancy version may be sufficient. Thus, a single redundancy version among {0, 1, 2, or 3} can be fixedly used. Alternatively, a 1-bit redundancy version can be used so that two of the four redundancy versions can be used.

[0223] In another embodiment, to improve (E)PDCCH coverage, repetition or extension of the (E)PDCCH format can be used. The repetition of (E)PDCCH can be applied within a subframe or over multiple subframes. For the embodiments described herein, the (E)PDCCH coverage enhancement (enhanced) mode, the (E)PDCCH coverage extension (enhanced) mode, the coverage enhancement mode, and the coverage enhanced (enhanced) mode can be used interchangeably.

[0224] (E)CCE aggregation levels can be different so that (E)PDCCH candidates can have a larger aggregation level compared to legacy (E)PDCCH. For example, the aggregation levels {2, 4, 8, 16} or {4, 8, 16, 32} can be used for the coverage enhancement (enhanced) mode, where only the (E)PDCCH coverage enhancement (enhanced) mode may be applicable to the WTRU-specific search space, the PDCCH coverage enhancement (enhanced) mode can be used regardless of transmission, or the PDCCH coverage enhancement (enhanced) mode may be applicable to specific DCI formats and / or transmission modes.

[0225] (E)CCE aggregation levels set for the WTRU-specific or common search space can be different according to the operating mode of the WTRU. The operating mode of the WTRU can include the coverage enhancement (enhanced) mode. When the WTRU is configured as the coverage enhancement (enhanced) operating mode, a larger set of (E)CCE aggregation levels (e.g., {16, 32}) can be used, while when the WTRU is not configured as the coverage enhancement (enhanced) operating mode, a legacy set of (E)CCE aggregation levels (e.g., {4, 8}) can be used. The WTRU can be configured as the coverage enhancement (enhanced) operating mode via signaling of a higher layer or indicated during the PRACH procedure.

[0226] (E)CCE aggregation level sets can be configured or defined according to the PRACH resources used for PRACH preamble transmission from the WTRU. By using the PRACH resources that can be used for the coverage enhancement mode of operation, a larger (E)CCE aggregation level set can be used when the WTRU receives a RAR. By using the PRACH resources that can be configured for a WTRU without coverage limitations, a smaller (E)CCE aggregation level set can be used when the WTRU receives a RAR.

[0227] (E)CCE aggregation level sets can be configured or defined according to the coverage limitation level of the WTRU, and the coverage limitation level can be defined by one or more of RSRP, path loss, timing advance, and PRACH resources. For example, if the path loss or RSRP calculated at the WTRU receiver is lower than a predefined threshold, the WTRU can determine a larger (E)CCE aggregation level set among the (E)CCE aggregation level set candidates.

[0228] (E) For PDCCH coverage enhancement mode, a default WTRU-specific search space can be defined, where a subset of aggregation levels can be used. For example, if {1, 2, 4, 8, 16, 32, 64} is the set of aggregation levels used for (E) PDCCH coverage enhancement mode, in the default WTRU-specific search space, the subset {2, 4, 8, 16} can be used. Therefore, before performing WTRU-specific configuration, the WTRU can monitor (E) PDCCH in the default WTRU-specific search space using the subset of aggregation levels {2, 4, 8, 16}. If the WTRU fails to decode (E) PDCCH within a certain number of attempts or time period in the default WTRU-specific search space, the WTRU can autonomously change the aggregation level to a higher aggregation level set (e.g., {4, 8, 16, 32}). Alternatively, the WTRU can monitor the default WTRU-specific search space until it receives the WTRU-specific configuration from a higher layer.

[0229] Two or more default WTRU-specific search spaces (WSS) can be defined in different time / frequency resources, and the aggregation level sets can be different according to the position of the default WTRU-specific search space. For example, two default WTRU-specific search spaces can be, for example, default WSS1 and default WSS2, and the aggregation level set {1, 2, 4, 8} can be used for default WSS1, and the aggregation level set {16, 32, 64, 128} can be used for default WSS2. The WTRU can be notified during the PRACH procedure which default WSS it may need to implicitly monitor.

[0230] (E)PDCCH coverage enhancement (enhanced) mode, for (E)PDCCH transmission, subframes can be bundled. For example, (E)PDCCH can be transmitted over K (K>1) subframes. Within the bundled subframes, the starting (E)CCE numbers can be made the same so that the WTRU can integrate (E)CCEs on multiple subframes without performing demodulation. The (E)PDCCH coverage enhancement (enhanced) mode can be applicable to the WTRU-specific search space. The (E)PDCCH coverage enhancement (enhanced) mode can be used regardless of transmission. The (E)PDCCH coverage enhancement (enhanced) mode can be made applicable only to specific DCI formats and / or transmission modes.

[0231] WTRU behavior can be defined by two control channel modes (mode 1 and mode 2) and can be configured by higher layer signaling. Mode 1 can be called / defined, without limitation, as the normal mode, legacy mode, normal coverage mode, and / or legacy coverage mode. Mode 2 can be called / defined, without limitation, as the extended mode, coverage extension mode, extended coverage mode, and larger coverage mode. The WTRU can be configured using any type of transmission mode (TM1~TM10) and control channel mode. The WTRU category can be defined using one or more control channel coverage extension methods. Therefore, a WTRU falling into this category can know which type of control channel mode needs to be used. A WTRU category using a control channel coverage extension method can operate as a WTRU of another category initially until the WTRU transmits the WTRU category to the eNB.

[0232] The two modes of operation can be defined as a normal mode and a coverage enhancement (enhanced) mode. When the WTRU switches to, or enters, the coverage enhancement (enhanced) mode, a solution for (E)PDCCH coverage enhancement (enhanced) mode can be used.

[0233] Closed-loop MIMO operation using enhanced feedback is described herein. In an exemplary method for (E)PDCCH coverage enhancement, closed-loop beamforming with a large feedback overhead can be used. LC-MTC devices may suffer from short coverage, but since LC-MTC devices can be deployed underground, for example, the channel status can be static. Therefore, since the channel does not change at least frequently, closed-loop beamforming with a large feedback overhead can be reported for better beamforming gain. Here, a Channel Quality Indicator (CQI) / Precoder Matrix Indicator (PMI) and / or Rank Indicator (RI) can be applied, and / or the WTRU can report the channel covariance matrix over a long term if it is configured using the control channel coverage extension mode. The WTRU may need to report explicit channel feedback if it is configured using the control channel coverage extension mode. Here, explicit channel feedback can include a wideband and / or sub-band channel covariance matrix, a wideband and / or sub-band quantized channel matrix, and / or a multi-rank PMI, explicit channel feedback can be reported via higher layer signaling, and / or whether explicit channel feedback is reported can be based on the eNB configuration.

[0234] A method for providing enhanced or improved PBCH coverage is provided herein. The PBCH can include some important information for initial access, such as the DL system bandwidth, SFN number information (e.g., 8 MSB of a 10-bit SFN), PHICH configuration, and the number of common reference signal (CRS) ports, to enable DL signal reception in a WTRU receiver. Embodiments described herein can provide system information that is robust to WTRUs suffering from low received SINR. Some embodiments can be based on actual PBCH coverage enhancement, and other embodiments can use another container for carrying system information.

[0235] In an embodiment, a new PBCH can be used or intended to be used by a WTRU, such as a WTRU that may experience coverage limitations. The new PBCH may be referred to herein as an enhanced PBCH or ePBCH, and the new PBCH can be used interchangeably with those terms. In addition to the legacy PBCH, an ePBCH can be transmitted within a system or on a carrier that can support, or is intended to support, for example, legacy signals and / or legacy WTRUs, to enable backward compatibility. The ePBCH can be transmitted within a non-backward compatible carrier (e.g., a new carrier type) that cannot support, or is not intended to support, a certain legacy signal and / or legacy WTRU. The ePBCH can differ from the legacy PBCH in at least one of the transmission mode, time / frequency position, or repetition frequency (e.g., within a subframe and / or frame).

[0236] In an example, the ePBCH can use DM-RS-based transmission, and thus, without limitation, use at least one of antenna ports {107, 108, 109, 110} or {7, 8, 9, 10}. Alternatively, a new antenna port can be defined. The DM-RS can be scrambled using a physical cell ID or physical cell identification information (PCI). For the broadcast channel, DM-RS-based TxD can be used. For example, 2Tx or 4Tx transmits in a diversity (TxD) mode. One of the transmission modes of single antenna port 2Tx TxD or 4Tx TxD can be used in a predefined manner. One of the transmission modes of single antenna port 2Tx TxD or 4Tx TxD can be used, and the WTRU may need to blindly decode one of them.

[0237] The antenna port number for single antenna port 2Tx TxD or 4Tx TxD can be defined in at least one of the following ways, i.e., the single antenna port can be predefined as a fixed antenna port number such as port 107, or the single antenna port can be configured as a function of PCI using modulo arithmetic between antenna ports {107, 108, 109, 110} or {107, 108}. For example, modulo-4 arithmetic can be used with the PCI as n = (PCI) modulo-4, where n can indicate one of the antenna ports. Two or four antenna ports such as {107, 108} for 2Tx and {107, 108, 109, 110} can be predefined. For a simple system design, a single antenna port and 2Tx TxD can be used for ePBCH transmission.

[0238] In another embodiment, the ePBCH can be arranged within several physical resource blocks (PRBs), such as the central PRBs, for example, the central six PRBs, or six or fewer PRBs, where the center can be related to the transmission bandwidth. The ePBCH can be present in a subframe different from the legacy PBCH. Since the legacy PBCH can be transmitted in the first subframe within a radio frame or can always be transmitted, the ePBCH can be arranged in other subframes. The ePBCH can be arranged in a different PRB from the legacy PBCH, and when arranged in different PRBs (or non-overlapping resources), it can be arranged in the same subframe as the legacy PBCH. In each subframe where the ePBCH can be arranged, the same PRB can be used for the ePBCH.

[0239] The ePBCH and / or the legacy PBCH can be transmitted by the eNB or the cell.

[0240] In an embodiment, the ePBCH can be arranged in one or more (one or more) subframes within each radio frame, or within a certain radio frame, for example, a radio frame having a certain SFN number, or a radio frame having an SFN with certain characteristics, and can be used interchangeably when arranged and transmitted. Examples of SFNs with certain characteristics include an SFN whose remainder when divided by a certain number X is equal to 0 or another value, an SFN whose remainder when dividing the most significant n bits of the SFN by a certain number X is equal to 0 or another value, or an SFN whose remainder when dividing (SFN + offset Y) by a certain number X is equal to 0 or another value. An example of an SFN can be one or more (one or more) sets of consecutive SFNs, and the start SFN of each set can have a certain characteristic, such as the remainder when dividing the most significant n bits (which can include all bits of the SFN) of the SFN by a certain number X being equal to 0 or another value. The subframes and / or radio frames and / or radio frame characteristics for the ePBCH can be fixed or can be a function of the physical cell identification information (PCI) of the cell and / or other system parameters.

[0241] In one example, the ePBCH can be placed in one or more (one or more) subframes within a radio frame, and a radio frame can be, for example, a certain (e.g., predefined) subset of radio frames within an SFN cycle (which can include 1024 radio frames that can be numbered from 0 to 1023). The subset of radio frames can occur periodically or can be arranged. For example, the ePBCH can be arranged with a certain periodicity (e.g., repeating every x ms or every y radio frames, where x and y can be positive integers) within a certain number of, for example, 4 consecutive radio frames. The starting radio frame (e.g., the lowest SFN number) of the subset of radio frames (or each period of radio frames) containing the ePBCH can be determined or defined as a function of one or more (one or more) system parameters and / or PCI. As an alternative to consecutive frames, they can be separated by a certain (e.g., fixed) number of frames. In the embodiments described herein, frames and radio frames can be used interchangeably.

[0242] In some embodiments, each radio frame that can be transmitted by an eNB or cell and / or received by a WTRU can be associated with a system frame number (SFN). The SFN or a part of the SFN can be transmitted or broadcast in at least one subframe of each radio frame (e.g., 8 bits of the SFN can be broadcast in the legacy PBCH within subframe 0 of all radio frames). The SFN can have a cycle of N frames, i.e., the SFN number can range from 0 to N - 1, and after reaching frame N - 1, it can start again from 0 in the next frame. In the case of a system such as LTE, N can be 1024. N frames can constitute an SFN cycle.

[0243] The information carried by the ePBCH, such as system information, can be the same during a certain time period, such as one or more repetition periods or one or more SFN cycles, or can be the same in all radio frames, for example, as long as the system parameters of the cell are not reconfigured.

[0244] In an embodiment, the ePBCH arranged within a certain radio frame can have the same signal structure as the legacy PBCH that can be transmitted within that radio frame, for example, within subframe 0. The signal structure can include at least one of information, information bits, and coded bits. The ePBCH can be transmitted in one or more (one or more) subframes within a certain radio frame, and in each of those subframes, it can have the same signal structure as the legacy PBCH within that radio frame. In each of the subframes in which the ePBCH within a certain radio frame can be transmitted, the ePBCH transmission can be present at the same time / frequency position as where the legacy PBCH can be transmitted in subframe 0. For example, the ePBCH transmitted in one or more (one or more) subframes within radio frame m can have the same signal structure as the legacy PBCH that can be transmitted in subframe 0. In the case of the ePBCH transmitted in four consecutive frames, such as frames m, m + 1, m + 2, m + 3, etc., in each of those frames, the ePBCH that can be arranged in one or more (one or more) subframes within each frame can have the same signal structure as the PBCH of that frame (for example, the ePBCH within m can have the same signal structure as the PBCH within m, the ePBCH within m + 1 can have the same signal structure as the PBCH within m + 1, etc.), and the PBCH signal structure can be different in one or more of those frames (for example, different in each of those frames). The ePBCH within each subframe of a frame can have the same signal structure.

[0245] In an embodiment, the ePBCHs arranged in a certain radio frame can have the same signal structure in each subframe of the radio frame in which the ePBCHs are arranged. The ePBCHs can have different signal structures for different radio frames. For example, in the case of ePBCHs transmitted in four consecutive frames, such as frames m, m + 1, m + 2, m + 3, etc., the ePBCH signal structure can be the same in each subframe in which the ePBCH is transmitted, but can be different in different frames. This can correspond to repeating coded bits within a frame and dispersing coded bits across frames.

[0246] In another embodiment, the ePBCHs arranged in a certain radio frame can have different signal structures in each subframe of the radio frame in which the ePBCHs are arranged, and the ePBCH transmissions in the radio frames within a certain period can be the same. For example, in the case of ePBCHs transmitted in four consecutive frames, such as frames m, m + 1, m + 2, m + 3, etc., the ePBCH signal structure can be different in each subframe in which the ePBCH is transmitted, and the transmissions in consecutive frames can be the same. This can correspond to dispersing coded bits within a frame and repeating them for each of a plurality of frames.

[0247] In another example, the ePBCH can include a payload size that is smaller than that of the legacy PBCH. This can be enabled because the configuration options may not require as many bits as are defined for the legacy MIB. The ePBCH can include, for example, a 3-bit DL system bandwidth (options that can be 6, 15, 25, 50, 75, and 100 PRB may be sufficient), a 3-bit PHICH configuration (options that can include normal and extended durations and resources equal to 1 / 6, 1 / 2, 1, 2 may be sufficient), an 8-bit SFN, and a 16-bit CRC, which can result in a 30-bit payload size for the ePBCH. Alternatively, a 3-bit DL system bandwidth, a 3-bit PHICH configuration, and an 8-bit SFN number with an 8-bit CRC added can be used, thus resulting in a 22-bit payload size. Alternatively, one or more of the system information, such as the PHICH configuration, can be removed from the ePBCH payload.

[0248] In another embodiment, the WTRU can determine the SFN based on the location of the ePBCH, e.g., based on one or more (one or more) frames in which the WTRU can determine that the ePBCH is present. In this case, the ePBCH payload may not include bits for the SFN number (e.g., 8 bits). For example, the ePBCH can be placed within a frame, such as a sequence of frames (e.g., four consecutive frames) that can have a certain SFN characteristic, e.g., the SFN of the consecutive frames can have the same k most significant bits, where k can be equal to 8, and / or can be determined based on one or more system parameters and / or PCI.

[0249] In an embodiment, the WTRU can determine the SFN of a radio frame (e.g., a set of one or more (more than one) radio frames within a set, such as a consecutive set of radio frames, e.g., the first radio frame within the set) based on information carried by the ePBCH and / or based on one or more frames in which the WTRU can determine that the ePBCH exists. The WTRU can use, for example, a windowing technique, in which it can know what to expect (e.g., format, content, coding, etc.) regarding the ePBCH in a set of subframes (e.g., three subframes in each of four consecutive frames) within a set of frames in which the ePBCH can exist. The WTRU can move the window from one set of frames to the next and can attempt to decode the ePBCH (which can include combinations over subframes and / or frames required to achieve a gain), including moving the window by a certain number, such as one frame at a time, until the ePBCH information bits can be decoded. If the WTRU can successfully decode the ePBCH, it can obtain the SFN (e.g., the SFN of the first frame of the window) from the information bits, or the WTRU can determine the SFN based on the frame in which the ePBCH was found, e.g., based on a certain (e.g., a known) SFN, or based on a certain (e.g., a known) SFN characteristic of the frame in which the ePBCH can be found. As a variation, for example, if the ePBCH signal structure within a frame is the same as the PBCH signal structure within the frame, in addition to the ePBCH, the PBCH can be used. The PBCH can be treated in the same way as if it were the ePBCH, e.g., it can be combined with the ePBCH to achieve a gain.

[0250] In another embodiment, one or more ePBCH subframes within a frame can be arranged using a subframe offset so that a WTRU can know subframes in which the ePBCH can be placed and which may be capable of successfully demodulating the ePBCH. The WTRU can acquire synchronization with the cell before attempting to receive the legacy PBCH, and since the synchronization signal can be transmitted in a known subframe, after acquiring synchronization, the WTRU can know which subframes can contain the legacy PBCH or the synchronization channel. The WTRU can determine the position of the ePBCH using one or more subframe offsets that can be an offset from the subframe of the synchronization channel (primary synchronization signal (PSS) or secondary synchronization signal (SSS)) or from the subframe in which the legacy PBCH can be found.

[0251] In an example, the subframe offset can be pre-defined as a fixed number, such as N offset =4, or the subframe offset can be configured as a function of the physical cell ID (PCI), for example, using modulo arithmetic. For example, N offset =(PCI) modulo-K, where K can be a pre-defined number that can be, for example, greater than 2 and / or less than 10. If the ePBCH is present in more than one subframe within a frame, more than one offset can exist.

[0252] In an example of TDD, the subframe offset can be a function of the TDD UL / DL configuration.

[0253] In another example, multiple subframe offsets can be used for repetition. For example, to transmit the ePBCH more frequently, N offset,1 and N offset,2It can be used. The subframe offset can be pre-defined as a fixed number or configured as a function of the physical cell ID.

[0254] In another embodiment for the ePBCH, fewer bits can be used for the SFN indication. For example, instead of an 8-bit SFN number, a SFN number indicator of 7 bits or less can be used so that the SFN number provided by the ePBCH can be the same over a longer time window. If a 7-bit SFN number indicator can be used, the 7-bit SFN number can indicate, for example, the most significant 7 bits of a 10-bit SFN number, and the WTRU can implicitly detect the least significant 3 bits 000, 001, 010, 011, 100, 101, 110, 111 in each radio frame, for example, from the scrambling code of the coded bits. In this case, the broadcast channel (BCH) transport block can be coded / rate matched and scrambled at the bit level so that each radio frame can have a different part of the scrambled coded bits. For a 7-bit SFN indication, the ePBCH time window can be 80 ms, which can be twice the legacy PBCH time window, where the PBCH time window can be considered as the TTI for PBCH transmission.

[0255] In another embodiment, when both legacy PBCH and ePBCH can be transmitted within the same cell, the WTRU behavior for PBCH reception can include at least one of the following exemplary behaviors. In an example, the WTRU can measure the reference signal received power (RSRP) before receiving the PBCH, and if the measured RSRP is lower than a threshold, the WTRU can attempt (or start to attempt) to receive and / or decode the ePBCH. Otherwise, the WTRU can attempt (or start to attempt) to receive and / or decode the legacy PBCH. In another example, the WTRU can attempt (or start to attempt) to receive and / or decode the legacy PBCH, for example, at the start of initial access, and if the WTRU fails to receive and / or decode the legacy PBCH during a certain number of attempts (which can be predefined or implementation-dependent), the WTRU can stop attempting to receive and / or decode the legacy PBCH and can attempt (or start to attempt) to receive and / or decode the ePBCH. In another example, if the WTRU can fall into or belong to a specific WTRU category, the WTRU can attempt (or start to attempt) to receive and / or decode the ePBCH, or can always attempt (or always start to attempt) to do so, which can be done instead of or in addition to attempting to receive and / or decode the legacy PBCH.

[0256] In another example, when both the legacy PBCH and the ePBCH can be transmitted within the same cell, the WTRU behavior for PBCH reception can include at least one of the following. The WTRU can attempt (or begin to attempt) to receive and / or decode the legacy PBCH, for example, at the start of initial access. If the WTRU fails to receive and / or decode the legacy PBCH during a certain number of attempts (which can be predefined or implementation-dependent), the WTRU can attempt (or begin to attempt) to receive and / or decode the ePBCH. The WTRU can combine ePBCH reception (e.g., ePBCH bits that can be demodulated bits) with legacy PBCH reception (e.g., PBCH bits that can be demodulated bits) to achieve a gain. Alternatively, the WTRU can decide to attempt (or begin to attempt) to receive and / or decode the ePBCH in addition to the legacy PBCH based on an RSRP or another measurement value that meets a certain criterion, such as falling below a threshold. Alternatively, the WTRU can decide to attempt (or begin to attempt) to receive and / or decode the ePBCH or the legacy PBCH based on an RSRP measurement value or another measurement value that meets a certain criterion, such as falling below a threshold.

[0257] A WTRU is described herein that can have a low received SINR, or can fall into or be a certain WTRU category that may not be able to successfully receive system information that can be carried via the legacy PBCH. Another channel can be provided for receiving system information, such as one or more of the elements of system information generally provided by the legacy PBCH, and / or can be used by a WTRU such as a certain WTRU.

[0258] To carry system information, such as at least one of DL system bandwidth, PHICH configuration, and SFN number, the (E)PDCCH common search space (or newly defined search space) can be used. The (E)PDCCH common search space, or a subset of the (E)PDCCH common search space (or other search spaces such as a system information search space (e.g., system information PDCCH (SI-PDCCH))) can be used to carry system information.

[0259] For system information, a new DCI format can be defined. For example, for system information, DCI format x can be defined, and DCI format x can include one or more of DL system bandwidth, PHICH configuration, and SFN number. The DCI format can include the same information provided by the legacy PBCH, and the information can be represented in the same way (e.g., the information elements (IEs) of the MIB can be included in the DCI). For the system information DCI format x, the same coding chain used for other DCI formats can be used. For the DCI format x, a pre-defined ECCE number can be used. Here, the aggregation level can be a pre-defined number (e.g., 8), or multiple aggregation levels can be used in the blind decoding method.

[0260] The DCI format x that can include system information can be transmitted periodically in a pre-defined subframe. For example, in all subframes 4 within a radio frame, the DCI format x can be transmitted within the EPDCCH common search space (or other search spaces that can be used for system information).

[0261] The subframe position within a radio frame can be different, such as 2, 3, 4, or 6. Therefore, a WTRU in coverage enhancement operation mode can decode the DCI format x that can include system information instead of the PBCH.

[0262] In TDD, the subframe position can be defined as a function of the TDD UL / DL subframe configuration. For example, in UL / DL subframe configuration 1, subframe 4 can be used, while in UL / DL subframe configuration 2, subframe 3 can be used.

[0263] Consecutive subframes or a plurality of subframes that can exist within a certain time window can include DCI format x without changing the SFN number. To improve coverage, for example, for a plurality of subframes that can be consecutive DL subframes, DCI format x can be transmitted repeatedly. Since the SFN does not need to be changed within these multiple subframes, the WTRU can integrate DCI format x to improve coverage. The time window can be a radio frame. The multiple subframes that can transmit DCI format x without changing the SFN number can exist within the same frame.

[0264] Two types of (E)PDCCH can be defined, such as type 1 and type 2 (E)PDCCH common search space (CSS), and one of the (E)PDCCH common search space types can be used for system information. The type 1 (E)PDCCH CSS can be used interchangeably with cell-specific (E)PDCCH CSS, system (E)PDCCH CSS, pre-defined (E)PDCCH CSS, distributed (E)PDCCH CSS, and / or broadcast (E)PDCCH CSS. The type 1 (E)PDCCH CSS position can be pre-defined to be within the central six RBs and does not have to be transmitted in all subframes. For example, in FDD, the type 1 (E)PDCCH CSS can be transmitted in all or a subset of subframes {1, 2, 3, 4, 6, 7, 8, 9}, or only therein. The type 1 (E)PDCCH CSS can be transmitted in a subset of radio frames. The type 2 (E)PDCCH CSS can be used interchangeably with WTRU-specific (E)PDCCH CSS, (E)PDCCH CSS configured by the eNB, and / or localized (E)PDCCH CSS. The type 2 (E)PDCCH CSS position can be configured by higher layer signaling and / or a broadcast channel. The broadcast channel can include DCI format x. The DCI format x for system information can be transmitted in the type 1 (E)PDCCH CSS.

[0265] The newly defined search space for use with system information (e.g., SI-PDCCH) can have the characteristics described above for type 1 (E) PDCCH. Based on the means by which an eNB (or cell) transmits a certain system information (e.g., system information that can be included within a legacy PBCH) to (e.g., a certain WTRU that can be part of a group of WTRUs) and / or based on the means by which a WTRU receives such information, one or more of the following can be applied. An eNB or cell communicating with a certain WTRU may not provide a PHICH in response to a UL transmission from the WTRU that is granted or scheduled by the eNB or cell. The WTRU can understand that it is not expected to support a PHICH. The WTRU does not have to search for a PHICH that may be provided by the eNB or cell in response to a UL transmission from the WTRU, does not have to expect a PHICH, and / or does not have to operate based on a PHICH.

[0266] The WTRU can understand that it is not expected to support CRS-based transmission. The WTRU can assume that CRS is not transmitted in the subframe in which the WTRU receives a DL grant, and can assume that rate matching around the CRS for PDSCH reception is not required. An exception to this is a certain subframe in which it is known by the WTRU that CRS is transmitted and one or more port numbers are known in advance (e.g., CRS can be transmitted in subframes 0 and 5 using port 0). The means can include a channel in which a certain system information, e.g., ePDCCH common search space or SI-PDCCH, is transmitted or received.

[0267] A subset of the system information that can be included within a legacy PBCH can be transmitted by the eNB or cell and received by the WTRU in a channel other than the PBCH, e.g., (E) PDCCH CSS or SI-PDCCH.

[0268] The PHICH configuration may not be provided and / or the CRS port number may not be provided. The system information that can be included in the legacy PBCH can be grouped into multiple subsets, which can be transmitted separately by the eNB or cell and / or received by the WTRU.

[0269] Each subset, such as System Information Subset 1 (SBS1) and System Information Subset 2 (SBS2), can be defined, transmitted, or received separately. For example, SBS1 can include the DL system bandwidth and the SFN number, and SBS2 can include the CRS port number and / or the PHICH configuration. In another example, SBS1 can include the DL system bandwidth, and SBS2 can include the SFN number and the CRS port number. In another example, SBS1 can include the DL system bandwidth and the CRS port number, while SBS2 can include only the SFN number.

[0270] Some of the system information that can be included in the legacy PBCH may not be included in any of the subsets (for example, the PHICH configuration may not be included in any of the subsets).

[0271] Each subset can have a different period or pattern for transmission. In an example, SBS1 can be transmitted every 5 ms, and SBS2 can be transmitted every 10 ms. In another example, SBS1 can be transmitted once every j ms, while SBS2 can be transmitted over consecutive subframes every k ms.

[0272] The system information inherent to LC-MTC is described in this specification. A device, such as an LC-MTC device or other device within a low SINR coverage area, can obtain network and cell information for cell access and connection establishment from a certain System Information Block (LC-SIB) that can be broadcast by an eNB supporting coverage enhancement such as LC-MTC coverage enhancement. In this case, one or more of the following methods can be applied to the LC-SIB. One or more LC-SIBs can exist.

[0273] In an example, the LC-SIB can be a signaling message (e.g., a Radio Resource Control (RRC) message) transmitted at a predefined frequency and time position. The LC-SIB can be semi-static (e.g., it does not need to change over a long time period) and can be periodically repeated in a predefined frame and in one or more predefined subframes between those frames.

[0274] In an example, the WTRU can consider the stored LC-SIB information valid during a predefined window duration or can follow the legacy SIB change procedure. The WTRU can receive a specific indication of an LC-SIB change with paging information. In an embodiment, the WTRU can re-acquire the LC-SIB each time for small data reception and / or connection establishment for reception. For example, the LC-SIB can include a sysInfoValue Tag indicating whether the LC-SIB currently stored in the WTRU is valid and up-to-date.

[0275] In an example, the LC-SIB may not include the SFN, and the LC-MTC device can obtain the SFN through means other than the LC-SIB or the legacy MIB.

[0276] In an example, the LC-SIB content can be restricted to one or more of the following information, which can be for the purpose of the LC-MTC device establishing a connection to the network. The information can be a PLMN-IdentityList. Since the mobility of the LC-MTC device can be restricted, the list can be restricted to a single Public Land Mobile Network (PLMN) ID. The information can be cell selection information. This can include RSRP / RSRQ thresholds for proper cell selection. The LC-MTC device can operate under coverage enhancement and may not have thresholds for proper cell selection criteria. Proper detection of the LC-SIB can be a selection criterion for a proper cell. For example, when proper cell selection according to legacy criteria fails, LC-MTC can consider cell selection with coverage enhancement operation.

[0277] In another exemplary embodiment, the information included in the LC-SIB can include random access channel (RACH) configuration information. There may be a configuration common to both the RACH and the physical RACH (PRACH) for the LC-MTC device to initiate connection establishment with the network. Certain parameters, such as those related to power control for the RACH procedure and UL transmission power, can be predefined in the WTRU so that it can reach the maximum transmission power relatively quickly in the random access process. For example, parameters such as the number of preambles, the maximum number of preamble transmissions, and the retransmission power step can be predefined to the maximum allowable values as defined in the RRC. For example, if the parameters are different from the predefined ones, the configuration for the RACH and PRACH can be specified in the LC-SIB. The configuration can be different from that of the RACH and PRACH in the SIB that provides the configuration for legacy (e.g., non-coverage-restricted) WTRUs and can include separate resources (e.g., preambles or preamble sets, and / or time / frequency resources).

[0278] In another exemplary embodiment, the information included in the LC-SIB can include PDSCH / PUSCH / PUCCH common configuration parameters. These parameters can be included for the WTRU operation of the UL / DL signaling radio bearer during the initial connection establishment with the network. The LC-SIB can also include UL information. For example, if the UL is not configured using the default UL / DL separation, or if the UL bandwidth is not the same as the DL bandwidth, UL carrier information is specified within the LC-SIB.

[0279] The LC-SIB can include information for RRC-specific timers. In an embodiment, the LC-MTC device can be pre-defined using different constant values and timer values compared to a normal WTRU. For example, the default values of the radio link failure detection timer and constants T310, N310, T311 can be set to different longer values to enable a lower likelihood of radio link failure (RLF) detection by the LC-MTC device in a coverage enhancement scenario. In an embodiment, the LC-MTC device can be configured not to perform radio link monitoring or not to indicate a radio link failure.

[0280] In coverage enhancement operations, some functions may not be supported by the LC-MTC device, so some parameters in the legacy SIB that may be required for normal WTRU cell access may not be included in the LC-SIB. It may also be possible for the LC-MTC device to fallback to normal operation for legacy SIB acquisition by reading and using normal cell system information. If the WTRU successfully reads the normal system information and maintains its validity, it can use the information from the normal SIB instead of the LC-SIB.

[0281] An SFN display that does not read the SFN in the legacy PBCH is described herein. A WTRU or device, such as an LC-MTC device or other device, that may be present in a coverage area with low SINR, can acquire or otherwise determine the SFN of the cell, and such acquisition or determination can be done without obtaining it from the legacy PBCH. In an embodiment, the determination of the SFN can be based on reception (e.g., successful reception or acquisition of a known signal and the timing of that signal).

[0282] The WTRU can determine the SFN at a resolution that can be full resolution (e.g., 10-bit resolution if the SFN cycle is 1024) or lower than full resolution. The full resolution SFN may be referred to as the full SFN. The SFN having a resolution lower than full resolution may be referred to as a reduced resolution SFN, reduced SFN, or subset SFN.

[0283] The timing of the signal can include one or more subframes in which the signal can be transmitted, one or more frames in which the signal can be transmitted, one or more subframes in which the WTRU can receive or successfully receive the signal, one or more frames in which the WTRU can receive or successfully receive the signal, and / or the periodicity of the transmission of the signal.

[0284] Known signals can be transmitted by an eNB or a cell. The signals can be transmitted in one or more of the following ways. In an exemplary embodiment, the signals can be transmitted in one or more pre-defined time / frequency resources. In another exemplary embodiment, the signals can be transmitted periodically at a pre-defined period which can be a number of frames. In another exemplary embodiment, the signals can be transmitted in one or more fixed or configured frames within a period. The one or more frames in which the signals can be transmitted can be a function of cell-specific configuration (e.g., physical cell ID). For example, a cell with a PCI of 100 can transmit a known signal every SFN cycle (e.g., every 1024 frames) such as SFN100 to indicate a certain SFN to a WTRU.

[0285] In another exemplary embodiment, the signals can be repeated in two or more sub-frames within the frame in which the signals can be transmitted. In another exemplary embodiment, the signals can be a pre-defined sequence, a system information block such as LC-SIB or SIB1, P-RNTI, or SI, or ePBCH.

[0286] A WTRU can receive or attempt to receive the signals and / or decode the signals in one or more sub-frames of the frame in which the signals can be transmitted. The WTRU can combine (e.g., integrate) signals from multiple such sub-frames within the frame in which the signals can be transmitted and use the combination to successfully receive and / or decode the signals in, for example, a single frame.

[0287] One or more frames capable of transmitting a signal and / or the periodicity of the transmission can indicate the SFN using full resolution. For example, the signal can be transmitted once per SFN cycle (e.g., once per 1024 frames) in a certain frame (e.g., frame 0) and can be used to indicate a certain SFN, such as 0. Upon successful reception of the signal, the WTRU can understand that the received frame is a certain SFN (e.g., SFN0). The WTRU can integrate signals on multiple frames that can be separated by the frames of the SFN cycle to achieve successful reception. A certain frame can be fixed or can be a function of the physical cell ID.

[0288] In another embodiment, the signal can be transmitted in a plurality of subframes (e.g., a certain subframe or all DL subframes) of a certain frame per SFN cycle (e.g., per 1024 frames) and can be used to indicate a certain SFN, such as 0. Upon successful reception of the signal, the WTRU can understand that the received frame is a certain SFN (e.g., SFN0). The WTRU can integrate signals on one or more of the plurality of subframes to achieve successful reception. Successful reception by the WTRU can be achieved in one frame. A certain frame and / or subframe can be fixed or can be a function of the physical cell ID.

[0289] One or more frames capable of transmitting a signal and / or the periodicity of the transmission can indicate the SFN using reduced resolution. For example, the signal can be transmitted every N frames, where (SFN cycle) / N can be an integer. The WTRU can integrate the reception in a certain frame, such as every Nth frame, until the signal is successfully received. Since the signal can be transmitted every N frames, the resolution of the SFN can be reduced.

[0290] For example, if a WTRU can successfully receive a signal, which can be achieved by integrating signals received every N frames (e.g., in one or more subframes every N frames), the WTRU can understand which frames are in the set of frames X, (X + N) modulo SFN cycle, (X + 2×N) modulo SFN cycle, (X + 3×N) modulo SFN cycle, but does not know which frame is which. For example, X can be 0, another known value, or X can be a function of the physical cell ID. For example, when X = 0, N = 8, and the SFN cycle is 1024, the WTRU can determine which frames are in the set of frames including frames 0, 8, 16, ..., 1016, but does not know which frame is which. In another example, when X = 0, N = 512, and SFN cycle = 1024, the WTRU can determine which frames are in the set of frames including frames 0, 512, but does not know which is frame 0 and which is frame 512.

[0291] The value of X can be provided to the WTRU via signaling such as broadcast signaling, which can be provided, for example, in a frame capable of transmitting a signal used for SFN determination. The WTRU can use the value of X to determine a revised set of frames starting from 0 (e.g., 0, N, 2N, etc.). For example, when X = 3, N = 8, and SFN cycle = 1024, the WTRU can recognize the set of frames that are 3, 11, 19, etc. In those frames, the WTRU can receive signaling such as broadcast signaling that identifies X as 3. The WTRU can then determine which frames are in the set of frames 0, 8, 16, 24, etc.

[0292] When SIB or other control signaling can be used as a signal for SFN determination, the SIB or control signaling can include the value of X.

[0293] When the WTRU understands the SFN using a reduced resolution (e.g., a set of frames X, (X+N) modulo SFN cycle, (X+2×N) modulo SFN cycle, (X+3×N) modulo SFN cycle, etc.), the WTRU can implicitly determine which frames are even, which are odd, and which are frames between known frames. The WTRU can use that information for a procedure such as a random access procedure. For example, if the WTRU can know the set of frames 0, 8, 16,..., it can also know the set of frames 1, 9, 17,... and 2, 10, 18,... by shifting by 1 frame and 2 frames respectively. Thus, the WTRU can know which are the even frames that may be required for a random access procedure such as an initial random access procedure and which are the odd frames that may be required.

[0294] The acquisition or determination of the subset SFN by the WTRU can include frames per N that can be used by the WTRU to determine the subset SFN (where N is the period of the signal in frame units), meaning or resulting in the WTRU discriminating one or more sets of frames. The sets of frames can be unique. There can be a maximum of N such sets of frames. The number of elements in each set can be (SFN cycle) / N. This can be equivalent to the WTRU understanding the value of SFN modulo N for that frame for each frame.

[0295] The WTRU can obtain or determine a subset SFN based on acquisition of the LC-SIB, predefined frame rules, and periodicity of LC-SIB transmission. The WTRU can obtain or determine a subset SFN based on successfully decoding SIB1 appropriately. For example, SIB1 can be transmitted at SFN X, where X can be 0 and can correspond every 2 frames (e.g., every even frame) and can repeat every 20 ms. It can be understood that acquisition of SIB1 can correspond to finding an even frame, which can enable the WTRU to determine which frames are even and which are odd.

[0296] If the paging density of the cell (e.g., the nB parameter in RRC) is greater than 1 frame (e.g., nB = T / 2, T / 4, T / 8, T / 16, or T / 32), the WTRU can obtain and determine a subset SFN based on the P-RNTI in the common search space of the PDCCH or EPDCCH.

[0297] The WTRU can obtain a subset SFN based on SI periodicity, which can be indicated in the SI schedule. The configuration of a SI can enable a periodicity of up to 512 frames.

[0298] In another embodiment, the determination of the SFN can be based on reception (e.g., successful reception) of the full-resolution SFN and / or subset SFN. The subset SFN can be sufficient for certain procedures such as random access, such as system information acquisition and initial random access (e.g., random access).

[0299] The eNB or cell can transmit a signal that can include a full-resolution SFN (e.g., 10-bit resolution if the SFN cycle is 1024) and / or a subset SFN. One or more of the following can be applied to the signal. In an example, the subset SFN can represent the least significant B bits of the full-resolution SFN, such as the three least significant bits. This can correspond to SFN modulo (2^B), which can be SFN modulo 8 in the case of a 3-bit example. If the reception of the subset SFN is successful, the WTRU can obtain the SFN modulo (2^B) for the frame in which the subset SFN was received and use it to understand the SFN modulo (2^B) for other frames, such as all frames.

[0300] In another example, the full-resolution SFN can be transmitted periodically using a duty cycle shorter than the SFN cycle. For example, the signal using the full SFN can be transmitted, among other things, every 8, 16, or 32 frames. The subset SFN can be transmitted one or more times during the duty cycle of the full SFN. The full SFN and / or the subset SFN can be transmitted in one or more subframes, including perhaps all or all of the DL, within the frame in which each is transmitted. The full SFN and the subset SFN can be transmitted in different numbers of subframes within the frame in which they are transmitted.

[0301] In another example, the definition of the periodicity and length of the SFN transmitted for a cell can be a function of the acceptable delay tolerance in the cell access procedure of a device, such as an LC-MTC device, and the cell-specific configuration for certain SFN-based procedures, such as DRX and RACH access. The SFN transmitted by the cell can be the full SFN and / or part of the SFN based on the periodicity of the full SFN and / or part of the SFN.

[0302] The WTRU can acquire and decode signals that can include a full SFN or a subset SFN. The WTRU can understand which SFN to receive based on one or more schedules for different SFNs. The WTRU can integrate (e.g., full SFN with full SFN and subset SFN with subset SFN) or otherwise combine the same signal from multiple subframes within a frame in order to receive the signal properly.

[0303] The WTRU can integrate (e.g., full SFN with full SFN and subset SFN with subset SFN) or otherwise combine the same signal from multiple frames, such as signals within frames separated by the periodicity of transmission, in order to receive the signal properly. This can be applicable to the full SFN when the periodicity is equal to the SFN cycle. This can also be applicable to the subset SFN when the periodicity is a multiple of the subset SFN cycle. For example, if the subset is 3 bits, the subset cycle can be 8. The SFN subset signal within a given frame can be combined with the SFN subset signal 8 frames or a multiple of 8 frames away from that frame.

[0304] For cell access purposes, the WTRU can use one or more of the above-described methods of SFN acquisition to complete the establishment of a connection with the cell. For example, knowledge of odd / even SFNs can enable the WTRU to initiate a random access procedure when the RACH / PRACH configuration is obtained by LC-SIB and / or normal SIB.

[0305] A method for enhanced PRACH coverage is described herein. For each case of the random access procedure, in embodiments for increasing PRACH coverage (and for the purpose of some form of preamble integration in, for example, the eNB), the WTRU can transmit multiple (e.g., many) preambles (or repeated preambles) from which it can draw only one RAR from the eNB. The repeated preambles can use the same preamble sequence as the first preamble and the same transmission power P PRACH can be used. The RACH can be used interchangeably with random access. The number of repetitions for the repeated preambles can be defined as "n" (e.g., a repetition factor, which can be a positive integer).

[0306] In embodiments, the WTRU can transmit a RACH preamble. Following the first preamble for the RACH procedure, the WTRU can transmit a repeated preamble at a later time, e.g., using the same resources, but in a later permitted frame. For example, if the first preamble uses the resource "subframe 4 of any SFN", the repeated preamble can be transmitted in subframe 4 of a subsequent frame. As another example, if the first preamble uses the resource "subframe 4 of even SFNs", the repeated preamble can be transmitted in subframe 4 of subsequent even frames.

[0307] The first preamble that can be followed by a repeated preamble can be present in any frame, or, if restricted to a certain frame (e.g., an even-numbered frame), can be present in any such restricted (e.g., even) frame. Alternatively, the first such preamble can be further restricted to only a certain frame. The first frame having the first preamble and subsequent frames having the repeated preamble may be referred to as a block of frames. The WTRU can, for example, transmit the first preamble in the first frame of the block or only in the first frame of the block.

[0308] A block can be identified as being within a group of frames, where any frame can be identified as being at a particular position within a particular block and each block can be identified as being at a particular position within the group. This can be known at the eNB and the WTRU. For example, the frame group can be a series of 1024 consecutive frames starting at SFN0 and ending at SFN1023.

[0309] The identification of frames within a block can be, for example, as shown in FIG. 12(a), where the length consisting of a series of blocks of equal length can be equal to the length of a frame group, if different block lengths are referred to as the first length, the second length, etc., or the length consisting of a series of blocks of equal length may not be equal to the length of a frame group, and some frames within the frame group may not be present within the block, as shown in FIGS. 12(b), (c), and (d), or the length consisting of a series of blocks of equal length and blocks of unequal length can be equal to the length of a frame group, as shown in FIGS. 12(e) and (f), or it can be any combination of all the methods shown in FIG. 12. Alternative methods not shown can be any deterministic method that the eNB and WTRU can know and specify or configure to disperse the frames within the block and the blocks within the group, for example, making them non - consecutive or mixing them.

[0310] An example of determining frames within a block is as follows. Let the group of frames be the frames numbered from SFN0 to SFN1023. Let Npre be the number or maximum number of preambles transmitted within a block, where Npre is a power of 2 (e.g., 64, 128, etc.) so that an integer number of blocks can be initially configured within the group as shown in Figure 12(a). For the case of a preamble that can be transmitted in any frame, the frames within the first block can be frames having SFN0 to (Npre - 1), the second block can be frames having SFN Npre to 2Npre - 1, and so on, and the last block includes frames having SFN1023 - (Npre - 1) to 1023. For the case of a preamble that can be transmitted only in frames numbered even, the frames within the first block can be frames having SFN0 to 2Npre - 1 (however, the last frame itself, since its SFN is odd, cannot be used to transmit a preamble), the second block can be frames having SFN 2Npre to 4Npre - 1 (however, the last frame itself, since its SFN is odd, cannot be used to transmit a preamble), and so on, and the last block includes frames having SFN1024 - 2Npre to 1023 (however, the last frame itself, since its SFN is odd, cannot be used to transmit a preamble).

[0311] In an example, the eNB can respond to a block of preambles using a RAR that can be transmitted after the last preamble in the block, for example, after it has been able to receive the last preamble, or after a time corresponding to the last preamble has elapsed if a preamble has been received. The WTRU can search for the RAR after the last preamble and within the configured response window for that preamble. In another example, the eNB can respond to a block of preambles using a RAR that can be transmitted after receiving any preamble in the block, for example, within the response window for any such preamble. The WTRU does not have to transmit a preamble within the block if it has been able to receive the RAR before transmitting the last preamble in the block.

[0312] If the WTRU is unable to receive the RAR within the response window for the last preamble of the block, it can start transmitting another block of preambles. In the case of a contention-based RACH procedure, the WTRU can select another specific preamble sequence for subsequent blocks, for example, applying the same timing backoff rules as those performed for Release 11.

[0313] The number of preambles transmitted within a block, the maximum number of preambles transmitted within a block, or the length of the block can be configured or specified. The value can indicate the total number of preambles to transmit, the length of the preambles (e.g., in units of frames), or how many additional preambles to transmit. In such a case, for example, zero can indicate that no repeated preambles can be transmitted.

[0314] The eNB can directly indicate the ability to detect repeated preambles, or by broadcasting a related quantity (e.g., the number of preambles transmitted within a block), and / or by indicating a separate PRACH resource for the repeated preambles. Such resources can use various indexes or tables. Alternatively, there may be no special resources for the repeated preambles.

[0315] In the case of an eNB capable of detecting repeated preambles, the maximum number of RACH preamble transmissions, e.g., preambleTransMax, can refer to the maximum number of preamble blocks. Alternatively, the network can configure the maximum number of preamble blocks separately.

[0316] The WTRU can autonomously determine to transmit a repeated preamble, e.g., if permitted by the network, and such determination can be based on one or more conditions including whether Pcmax < preambleInitialReceivedTargetPower + deltaPreamble + pathloss, whether (Pcmax ± some quantity) < preambleInitialReceivedTargetPower + deltaPreamble + pathloss, whether the previous RACH procedure failed due to reaching the maximum number of PRACH transmissions (preambleTransMax), or whether the device is always configured or hardwired to do so. The repeated preambles can be transmitted at the same power using the same preambles for a certain resource.

[0317] In an embodiment, a new or enhanced preamble format can be introduced that can increase the repetition factor (e.g., the number of repetitions) for the preamble. The terms new and enhanced can be used interchangeably. As a result, the energy for the PRACH preamble can be increased over more subframes. For example, a new preamble format as shown in Table 3 can be introduced, which can be used for coverage enhancement purposes.

[0318]

Table 3

[0319] In Table 3, “n” can be an integer greater than 2 and can be regarded as the repetition factor for the PRACH preamble.

[0320] For example, for coverage enhancement purposes, a new preamble format can be introduced for each CP length (i.e., T CP ). The repetition factor “n” can be defined using the configuration. For example, “n” can be a PRACH configuration parameter. The eNB can indicate or notify the value of “n” as part of the PRACH configuration, where “n” can be applied to the new preamble format. A subset of the preamble format can have the repetition factor “n”.

[0321] The repetition factor "n" can be calculated or determined by the WTRU, and the value "n" can be configured as a function of at least one of the DL path loss, RSRP, RSRQ, and / or other measurements. As an exemplary WTRU behavior, the WTRU can measure the DL path loss, and if the path loss is greater than a threshold, the WTRU can use a new additional preamble format. The calculated or determined path loss value can be used to obtain the repetition value "n". When the WTRU obtains the repetition value "n", it can transmit a PRACH preamble in a specific PRACH resource that can be used for the new preamble format having the repetition value "n".

[0322] Separate PRACH resources can be defined according to the repetition value "n". For example, repetition candidates {4, 8, 16} can be defined, and if the WTRU may need to use a repetition value such as n = 4, there can be a specific PRACH resource that can be used for the repetition value n = 4. In the example, the repetition candidates {4, 8, 16} can be used or used only, but other numbers and values of the repetition candidates can also be selected. In another example, the repetition value "n" can be a predefined number greater than 2, and there can be a PRACH resource configured for the repetition value "n" and another PRACH resource configured for the legacy PRACH format.

[0323] The subframe for PRACH transmission can be defined as a function of the repetition factor "n" since the required subframe can depend on the repetition factor. Table 4 shows examples of the required subframe lengths according to the repetition factor. For example, if the repetition factor is smaller than a threshold (e.g., 9), the starting subframe for PRACH transmission can be configured in all radio frames. Otherwise, the subframe can be configured in even or odd radio frames. Table 4 also shows examples of the required subframe lengths for the preamble format according to "n".

[0324]

Table 4

[0325] For coverage enhancement purposes, one or more additional preamble formats can be introduced. For example, additional preamble formats can be defined, and each CP length (T CP ) can have different repetition factors. Table 5 shows examples of multiple additional preamble formats for each CP length (T CP ).

[0326]

Table 5

[0327] As an example, preamble format 5 can include all supportable CP lengths in preamble formats 0 to 3, but the sequence length can be the same and use the repetition factor n1. Except for the repetition factor, the same can be applied to other new preamble formats, thus resulting in preamble formats 5, 6, and 7 having repetition factors n1, n2, and n3 respectively.

[0328] The repetition factor {n1, n2, n3} can be pre-defined, for example, as {4, 8, 16}. The repetition factor can be defined as a function of path loss and / or other measurements.

[0329] The PRACH resource can be configured / defined according to the repetition factor. For example, the WTRU can obtain the repetition factor and the WTRU can know which PRACH resource it needs to use for preamble transmission. The new preamble format can use the same CP length as in the previous preamble format, but the sequence length can be increased. The new preamble format can use the same sequence as the legacy format, but the sequence is repeated several times.

[0330] The preamble format and subframe configuration can be configured together in the broadcast channel. In the case of FDD, unused PRACH configuration indexes (e.g., 30, 46, 60, 61, 62) can be used for the new additional preamble format.

[0331] For coverage enhanced PRACH configuration, a separate random access configuration table can be defined. A separate group of preamble sequence indexes can be allocated (e.g., "Group C") for use by the WTRU for coverage enhancement purposes, e.g., explicitly, and can be communicated to the WTRU (e.g., in SIB2). The configuration of Group C preambles can also include an extended preamble format configuration and configuration index, which can be different from those specified for the configuration of preamble groups A, B. The WTRU can use the Group C configuration specified in SIB2, in addition to or instead of, the Group A / B preamble configuration.

[0332] In another embodiment, preamble formats such as preamble formats 0 to 3 can be reused using repetition. In the same PRACH resource, the same preamble format can be used. Here, coverage-enhanced (enhanced) PRACH transmission can use repetition of the same PRACH preamble. In the case of repetition of PRACH transmission, at least one of the following techniques can be used.

[0333] In an example, for a repetition-based PRACH preamble, a subset of the PRACH preamble can be defined or configured, and the repetition-based PRACH preamble can be transmitted repetitively within a time window size. For example, the time window size can be defined as win subframes or radio frames of N, and the same PRACH preamble may need to be transmitted in all PRACH resources within the time window of N. For example, if N win = 3 is used and the PRACH subframe is defined as {1 in any radio frame}, the WTRU may need to transmit the repetition-based PRACH preamble in three radio frames. The time window size can be predefined or configured as a function of the PRACH configuration. win = 3 is used and the PRACH subframe is defined as {1 in any radio frame}, the WTRU may need to transmit the repetition-based PRACH preamble in three radio frames. The time window size can be predefined or configured as a function of the PRACH configuration.

[0334] For a repetition-based PRACH preamble, additional frequency resources can be reserved, which can be orthogonal to the frequency resources for non-repetition-based PRACH preambles (such as PRACH preambles for legacy WTRUs). Thus, both types of WTRUs can use the same PRACH configuration, except for the frequency offset index (prach-FrequencyOffset). The time window can be used to indicate the number of repetitions of PRACH preamble transmission.

[0335] For repeated - based PRACH preambles, a subset of PRACH sub - frames can be reserved. Thus, the WTRU can transmit repeated - based PRACH preambles only in a subset of the configured PRACH sub - frames.

[0336] The same preamble format can be used in different PRACH sub - frames. For example, a sub - frame offset can be used that indicates the PRACH sub - frame for a repeated - based PRACH preamble. The sub - frame offset can be notified or indicated to the WTRU via the broadcast channel so that a WTRU that needs to transmit a repeated - based PRACH preamble can use the sub - frame for transmitting the repeated - based PRACH preamble.

[0337] Techniques for PRACH link adaptation and enhanced coverage are described herein. In an embodiment, a PRACH resource (e.g., PRACH resource type A) that can be used by, or can be intended to be used by, a legacy WTRU and / or a normal coverage WTRU, and / or a PRACH resource (e.g., PRACH resource type B) that can be used by, or can be intended to be used by, a WTRU that can require coverage enhancement, can be made available in a cell. The PRACH resource type A can be configured by a broadcast channel (e.g., SIB). A normal coverage WTRU can here suggest that an enhanced coverage operation mode is not used for the WTRU. The PRACH resource type B can be configured by a broadcast channel. An enhanced coverage WTRU can here suggest that the WTRU is configured using, or using an enhanced coverage operation mode. The broadcast channel for configuring the PRACH resource type B can be a dedicated broadcast channel for the enhanced coverage WTRU. The PRACH resource type A and type B can be used according to a PRACH preamble format. For example, the PRACH resource type A can be used for PRACH preamble formats 0 to 3, while the PRACH resource type B can be used for other PRACH preamble formats (e.g., formats 5 to 7). The PRACH resource type A and type B can be configured in separate time resources and frequency resources. Alternatively, the PRACH resources can completely or partially overlap in time resources and frequency resources. In another example, the type A PRACH resource is part of the type B PRACH resource.

[0338] PRACH resources that may require coverage enhancement or may be able to benefit from coverage enhancement and that can be used or can be intended to be used by a WTRU can be referred to as enhanced PRACH (ePRACH) resources. The ePRACH resources can be configured, for example, by signaling to the WTRU, for example, by broadcast (e.g., in an LC-SIB), by the eNB.

[0339] In the case of an FDD system, in an embodiment, type A PRACH resources can occupy six consecutive RBs in a selected set of UL subframes, while type B PRACH resources can be configured using six consecutive RBs at non-overlapping frequency positions within the same set of UL subframes. Here, the frequency positions for type B PRACH resources can be indicated by an offset from type A PRACH resources. In another embodiment, type A PRACH resources can occupy six consecutive RBs in a selected set of UL subframes, and type B PRACH resources can be configured using the central six RBs in an uplink subframe that does not overlap with type A PRACH resources. In another embodiment, type A PRACH resources can occupy six consecutive RBs in a selected set of UL subframes, and type B PRACH resources can be configured using six consecutive RBs at any time-frequency position that does not overlap with type A PRACH resources. In another embodiment, type A PRACH resources can be configured at any frequency position within a selected set of UL subframes, while type B PRACH resources can be configured at predefined positions. For example, for type B PRACH resources, the central six RBs in all UL subframes within a particular radio frame can be used.

[0340] In an embodiment, two or more type B PRACH resources can be configured using different coverage enhancement levels. For example, there can be a PRACH resource type B1 (level 1) and a PRACH resource type B2 (level 2), and the PRACH resource type B2 can provide better coverage than the PRACH resource type B1.

[0341] In the case of PRACH resource type or level selection, in an embodiment, the WTRU can select the level of the PRACH resource type according to a DL measurement value related to at least one of DL path loss, combined loss, geometry, RSRP, and RSRQ. For example, the WTRU can first measure the RSRP, and if the RSRP is lower than a threshold, the WTRU can select the PRACH resource type B to transmit the PRACH preamble. Otherwise, the WTRU can select the PRACH resource type A to transmit the PRACH preamble. In another embodiment, the PRACH resource type selection can be based on the WTRU category. For example, if the WTRU is a coverage-enhanced (enhanced) LC-MTC WTRU, the WTRU can always select the PRACH resource type B for PRACH preamble transmission. However, other WTRUs can select the PRACH resource type A. A coverage-enhanced (enhanced) WTRU can be a WTRU that requires coverage enhancement, or utilizes coverage enhancement techniques, or supports a coverage enhancement mode. The terms coverage-limited WTRU and coverage-enhanced (enhanced) WTRU can be used interchangeably.

[0342] In another embodiment, power control and PRACH resource hopping can be used for PRACH preamble transmission link adaptation. For example, if multiple PRACH resource types are configured with different levels of coverage limitation, the WTRU behavior when it does not receive the RAR for the transmitted PRACH preamble within the allocated time (e.g., ra-ResponseWindowSize) can be at least one of the following behaviors. In an exemplary behavior, if the WTRU is not configured with a coverage extension operation mode, the WTRU can transmit another PRACH preamble at a later time using higher power. For example, the preamble can be made higher by only powerRampingStep relative to the previous preamble transmission. Thus, the transmission power for preamble transmission can be increased with respect to the amount of powerRampingStep. In another exemplary behavior, if the WTRU is configured with a coverage extension operation mode, the WTRU can transmit another PRACH preamble at a later time using higher power or a different PRACH resource type. For example, if the WTRU does not receive the RAR for the transmitted PRACH preamble within the allocated time, the WTRU can choose to transmit another preamble at a later time using higher power with the same PRACH preamble format (e.g., formats 0 to 3) and the same PRACH resource type (e.g., type A), or can choose to transmit another preamble at a later time using a certain transmission power with a different PRACH preamble format (e.g., formats 5 to 7) and a PRACH resource corresponding to the preamble format (e.g., PRACH resource type B).

[0343] In another exemplary behavior, if the WTRU is configured to use a coverage extension (enhanced) operating mode, the WTRU can transmit another PRACH preamble at a later time using a higher power until it reaches the maximum transmit power (e.g., Pcmax or Pcmax,c). If the WTRU reaches the maximum transmit power for PRACH preamble transmission and does not receive a RAR for the transmitted PRACH preamble within the allotted time, the WTRU can transmit another PRACH preamble at a later time using a certain transmit power on a PRACH resource corresponding to the preamble format using a different PRACH preamble format.

[0344] A method is described herein for indicating, using a Physical Random Access Channel (PRACH), to an evolved Node B (eNB), for example, a coverage enhancement level that may be required by a Wireless Transmit / Receive Unit (WTRU). In an embodiment, the coverage limitation (or enhancement) level for each WTRU can be indicated by one or more of the following methods. In an exemplary method, the WTRU can be configured using a plurality of PRACH resource types, and the WTRU can select a PRACH resource type according to criteria such as downlink (DL) measurement values (e.g., one or more of path loss, combined loss, geometry, Reference Signal Received Power (RSRP), and Reference Signal Received Quality (RSRQ)). For example, the WTRU can first measure the RSRP and then select a PRACH resource type according to the measured RSRP, where the PRACH resource type can include one or more of a PRACH preamble format, a PRACH subframe, a PRACH frequency resource, and a preamble sequence. Other criteria or other DL measurement values than the RSRP can be used by the WTRU to determine which PRACH resource type should be transmitted to indicate the level of coverage enhancement required. Based on the PRACH resource type transmitted by the WTRU, the eNB can learn the coverage limitation (or required coverage enhancement) of the WTRU. For each resource type, a set of PRACH resources (which can be defined by one or more of a PRACH preamble format, a PRACH subframe, a PRACH frequency resource, and a preamble sequence) can exist. Once the WTRU has determined a PRACH resource type, it can select from among the set of PRACH resources associated with the type, and can do so according to random access procedure selection rules according to, for example, Release 11.

[0345] In another example, the WTRU can be configured using a single PRACH resource type that uses PRACH resource splitting. Thus, according to DL measurements or other criteria, the WTRU can select one of the split PRACH resources so that the eNB can understand the level of the WTRU's coverage limitation. The splitting of the PRACH resources can include one or more of the UL subframe, frequency resources, and the PRACH preamble. For example, the PRACH resources within an even-numbered radio frame can be considered as one PRACH split associated with a measured RSRP level 1, while the PRACH resources within an odd-numbered radio frame can be considered as another PRACH split associated with a measured RSRP level 2. In another example, the PRACH preamble can be split and, according to the measured RSRP level, the PRACH preamble can be selected by the WTRU from a set of PRACH preambles associated with the measured RSRP level. In these examples, the RSRP level can be replaced with any type of DL measurement or other criteria that can be related to WTRU coverage.

[0346] The PRACH preamble reserved for non-competition-based resources can be used to indicate the coverage limitation level. The PRACH transmission power can be set to the maximum value for the coverage-limited WTRU so that the eNB can estimate the coverage limitation level.

[0347] In embodiments, the WTRU can be shown to indicate a coverage enhancement level or to use a coverage enhancement level as part of the RACH process and the RRC connection establishment procedure.

[0348] Pre-assignment or semi-static assignment of C-RNTI is described herein. A WTRU within a limited coverage can be assigned using a C-RNTI that can be pre-defined or provided by the network at initial access. The WTRU can continue to use the C-RNTI semi-statically until the network indicates otherwise for using different C-RNTIs. The WTRU can consider the C-RNTI to be valid during long DRX and sleep cycles between cycles, as well as during the transition from RRC_IDLE to the RRC_CONNECTED mode for data transfer. In an embodiment, the WTRU can consider the C-RNTI to be valid between cell reselection or cell re-establishment in the RRC_IDLE mode and handover in the RRC_CONNECTED mode.

[0349] The WTRU can be signaled to use an enhanced coverage level by receiving a random access response (RAR) from the eNB in response to a preamble transmission based on a RA-RNTI or C-RNTI that can be assigned in one or more of the following ways. In an exemplary method, the WTRU can use a RA-RNTI from a set that can be specifically assigned for the WTRU in an enhanced coverage mode. For example, the WTRU can calculate the RA-RNTI as a function of time and frequency resources and, in an embodiment, as a function of an additional offset defined for the enhanced coverage WTRU. In another example, RA-RNTI values from 60 to 119 can be specifically assigned for the WTRU in an enhanced coverage mode.

[0350] In an embodiment, the WTRU can be further subdivided and the RA-RNTIs that can be allocated to different amounts for coverage enhancement can be specifically used for the coverage enhancement (enhanced) mode. For example, a WTRU with a 5 dB coverage enhancement amount can use a subset of the RA-RNTIs, and a WTRU with a 10 dB coverage enhancement amount can use another set of the RA-RNTIs.

[0351] In another exemplary method, in an embodiment, the WTRU can use a plurality of RA-RNTI candidates calculated from the time / frequency resources of the transmitted preamble, along with a set of RA-RNTIs for a plurality of coverage enhancement amounts, to search for the (E)PDCCH for the RAR from the eNB. The WTRU can be indicated to use the configured coverage enhancement amount from the eNB by the RA-RNTI for which the (E)PDCCH for the RAR is successfully decoded. The WTRU can derive the set of RA-RNTI candidates from a subset of the available coverage enhancement levels or from all of the available levels.

[0352] In another exemplary method, the WTRU can calculate a coverage enhancement-specific RA-RNTI or a coverage enhancement level specific to the RA-RNTI based on the selection of the time and / or frequency resources of the PRACH preamble. The assignment of a coverage enhancement WTRU or coverage enhancement level to a certain PRACH and preamble resource can be indicated to the WTRU by a normal SIB (e.g., SIB2) or an LC-MTC-specific MIB and SIB.

[0353] In another exemplary method, a WTRU in coverage enhancement mode can receive a RAR in response to a transmitted PRACH preamble via a pre-assigned or previously semi-statically assigned C-RNTI. The WTRU can detect and decode an (E)PDCCH for the RAR in CSS or WSS. When the WTRU receives the RAR via an (E)PDCCH scrambled with the C-RNTI, it does not have to search for contention resolution when transmitting msg3 (e.g., an RRC connection request) in response to the RAR. In embodiments, a WTRU that receives a RAR MAC control element (CE) via an (E)PDCCH and C-RNTI can receive one or more of the following shortened MAC CE information, namely, a UL grant, a timing advance (TA) command, and a coverage enhancement (enhanced) mode amount, in the RAR. For example, a coverage enhancement (enhanced) mode amount information element (IE) can indicate a 5 dB, 10 dB, or 15 dB coverage enhancement procedure.

[0354] In another exemplary method, the WTRU can receive information provided to it in a RA-RNTI-based RAR in a MAC CE. In embodiments, the WTRU does not have to receive any MAC subheaders for the RAR that include a RACH preamble identifier (RAPID) or a temporary C-RNTI, thus reducing the potential size of the RAR control element.

[0355] The indication of the amount of coverage enhancement during the RRC connection establishment procedure is described herein. In an example, the WTRU can indicate the amount of coverage enhancement to the eNB during the RRC connection establishment procedure. In an embodiment, the WTRU can be indicated the amount by the eNB during the procedure. Upon completion of the RACH procedure, the WTRU can operate in a coverage enhancement (enhanced) mode and, in an embodiment, can be configured using the amount of coverage enhancement. In another embodiment, the WTRU can overwrite or be overwritten with a new amount of coverage enhancement using one or more of the following methods. In an exemplary method, the WTRU can indicate it in the RRC connection request message (e.g., msg3). The WTRU can receive a configuration for the amount of coverage enhancement from the eNB in the RRC connection setup or RRC connection reconfiguration message, or based on any possible change in the coverage state, the WTRU can receive the amount of coverage enhancement as a reconfiguration of the amount of coverage enhancement in the RRC connection reconfiguration message.

[0356] Regarding the WTRU indicating the amount of coverage enhancement in the RRC connection request message, the WTRU can include the indication within the establishment reason of the RRC connection request message. For example, to indicate the coverage enhancement mode and amount, the remaining unused values within the IE can be assigned. In another example, the WTRU can provide an extended or alternative information element in the message to indicate the amount or level of coverage enhancement to the network in the RRC message. For example, if an LC-MTC WTRU indicates to the eNB that it is a coverage-limited WTRU, or if the eNB derives that the access WTRU is coverage-limited before or during the random access procedure, it can use the probability reason IE and reinterpret the IE bits to indicate the level of coverage enhancement. As a further example, the bits can be reinterpreted as an enumeration of {5 dB coverage enhancement, 10 dB coverage enhancement, 15 dB coverage enhancement} within the information element and included in the message.

[0357] Regarding a WTRU that receives, from an eNB, a configuration regarding an amount of coverage enhancement in an RRC connection setup or RRC connection reconfiguration message, the eNB can derive a coverage - limited WTRU and an amount of coverage enhancement based on the detected preamble signal strength. In an embodiment, the WTRU can provide information regarding coverage limitation to the eNB, which can include one or more of the PRACH preamble transmission power, the measured RSRP / RSRQ used for appropriate cell selection criteria, the number of preamble repetitions and re - transmissions, or the number of PDCCH and PDSCH repetitions required for RAR reception.

[0358] In an embodiment, based on any possible change in the coverage state, the WTRU can receive, in an RRC connection reconfiguration message, an amount of coverage enhancement as a reconfiguration. The WTRU can apply the reconfigured coverage enhancement mode, which has an appropriate processing delay (e.g., 15 ms), on the indicated channel to any of the applicable techniques.

[0359] Paging using enhanced coverage is described herein. To enhance the coverage of the paging channel for the WTRU, a separate set of paging frames (PFs) and paging opportunities (POs) different from those of normal WTRUs can be assigned to the WTRU for coverage enhancement purposes. In an embodiment, paging messages for LC - MTC having the same information can be repeated over a number of frames and / or sub - frames so that the WTRU can utilize the accumulation of paging information.

[0360] For example, a WTRU, such as a WTRU that requires coverage enhancement and includes an LC-MTC WTRU, can be assigned a paging frame and paging opportunities that are different from those of a normal WTRU so that the WTRU can read a subset of the paging opportunities for the cell. This can be done using one or a combination of the assignment of a second P-RNTI, the assignment of an LC-MTC specific paging frame (PF), and the assignment of multiple paging frames (PFs) in a DRX / paging cycle.

[0361] Regarding the assignment of a second P-RNTI, an alternative P-RNTI to the P-RNTI assigned in Release 8 (e.g., the P-RNTI value of 0xFFFE) can be indicated to the WTRU. The WTRU can indicate the value of the second P-RNTI as part of the paging and DRX configuration, or can provide an indication to use a second P-RNTI value that can be pre-determined. For example, the second P-RNTI value can be set as 0xFFFC. The WTRU can search for both the Release 8 P-RNTI and the second P-RNTI, or just the second P-RNTI, during the assigned paging opportunity. The WTRU can be indicated whether to use the second P-RNTI as part of the paging configuration.

[0362] Regarding the allocation of the paging frame (PF) inherent to LC-MTC, instead of being determined by the identification information of the WTRU, for example, signaling via RRC or the non-access stratum (NAS) can be used to allocate a pre-determined paging opportunity and DRX / paging cycle to the WTRU. The allocation of paging opportunities by the eNB to the WTRU for paging coverage enhancement can be a function of allocating paging opportunities for normal WTRUs and selecting paging frames not occupied by normal WTRUs. The WTRU can be provided with explicit paging frames and paging opportunities, and the WTRU does not need to apply the IMSI to determine the paging frame via legacy Rel-8 procedure means. For example, a legacy WTRU can be allocated a DRX length of 256 frames and an nB of T / 32 as paging parameters. This can enable the PF for normal WTRUs to occur in frames that are multiples of 32. To prevent the LC-MTC WTRU and normal WTRUs from sharing common paging opportunities, for example, using a long DRX cycle of 256, LC-MTC POs can be allocated to frames 1 to 31 for WTRUs for coverage enhancement.

[0363] Regarding the allocation of multiple paging frames (PFs) in the DRX / paging cycle, during the DRX cycle, multiple PFs for the LC-MTC WTRU can be specifically allocated to the WTRU. For example, this indication of multiple POs can take the form of a bitmap to indicate frames during the DRX cycle that are allocated as LC-MTC specific, or it can take the form of an offset of frames to indicate consecutive frames from the allocated LC-MTC POs allocated to the WTRU.

[0364] The WTRU can receive an indication to indicate connection initiation to the network as part of a paging record in a specified LC-MTC PO. The WTRU is unable to decrypt its own WTRU identification information within the paging record, but instead, the indication can be applied commonly to all LC-MTC WTRUs assigned that particular PO. For example, in an RRC paging message, instead of using a pagingRecordList IE that includes the WTRU identification information of each paged WTRU, there can be a 1-bit indicator that indicates that all WTRUs assigned to this PO should respond to the paging message using the RRC connection establishment procedure.

[0365] The WTRU can receive repeated RRC paging messages over a time period so that it can accumulate paging messages to obtain coverage enhancement gains. Paging can include a WTRU-specific paging record or a group paging indication (as described above). The paging message can be repeated in multiple assigned LC-MTC paging frames during a DRX cycle, or in an embodiment, can be repeated over the course of multiple DRX / paging cycles.

[0366] The WTRU can receive paging messages repeated within a plurality of subframes in the PF assigned for the LC-MTC WTRU and can accumulate them over those repeated subframes. For example, similar to Release 8 where the PO can occur in subframes {0, 4, 5, 9} of all paging frames, the WTRU can be indicated to receive repeated paging messages in up to 4 of those paging opportunities. The network can explicitly notify the WTRU of the number of subframes in which the paging message can be repeated. In an embodiment, the WTRU can decode the PDCCH using the P-RNTI in subframe 0 and cannot decode the PDCCH using the P-RNTI in other subsequent subframes, but can decode the PDSCH at the same position as the first subframe (e.g., subframe 0).

[0367] For additional cumulative gain of the paging message, the WTRU can receive paging messages in subframes other than the four subframes {0, 4, 5, 9}. The network can explicitly notify the WTRU of the subframes in which paging messages can be transmitted between paging frames.

[0368] In an embodiment, all transmission steps can have a time window such that the WTRU can execute one step at a time. For example, the DL transmission step can be defined as four time windows such as an (E)PDCCH window, a PDSCH window, a gap, and an A / N window, and the WTRU can receive the DL control channel only within the (E)PDCCH window and the PDSCH within the PDSCH window. Similarly, the A / N for the PDSCH can be transmitted only within the ACK / NACK (A / N) window. Thus, the WTRU can monitor the (E)PDCCH within the (E)PDCCH, while the WTRU can assume that no PDSCH is transmitted during the (E)PDCCH windows. In addition, the WTRU can assume that the (E)PDCCH associated with the PDSCH is not transmitted within the (E)PDCCH window. FIG. 13 is a diagram illustrating an example of window-based downlink transmission as described herein.

[0369] In another embodiment, certain steps can use window-based transmission. In this case, the following methods can be used. For example, the (E)PDCCH and the PDSCH can have windows, but the A / N transmission can end within a subframe. In another example, the (E)PDCCH can have a window, but the other transmissions can end within a subframe. In another example, the (E)PDCCH and the A / N transmission can have windows, but the PDSCH transmission can end within a subframe. In another example, the PDSCH transmission can have a window, but the other transmissions can end within a subframe.

[0370] In the case of window-based transmission, one or more of the following methods can be applied. In an exemplary method, each time window can include two or more subframes, and different numbers of subframes can be used according to the type of window. For example, for the (E)PDCCH window, the PDSCH window, the gap, and the A / N window, to define the window size, N epdcch 、N pdsch 、N gap, and N harq can be used. The values for the exemplary configuration shown in FIG. 13 are N epdcch = 6, N pdsch = 11, N gap = 4, and N harq = 9. The values of N epdcch , N pdsch , N gap , and N harq can be predefined for coverage enhanced transmission. The values of N epdcch , N pdsch , N gap , and N harq can be configured via the broadcast channel.

[0371] In an embodiment, within the (E)PDCCH window, the WTRU can monitor a search space to receive DCI for the PDSCH and / or PUSCH. In an example, the (E)PDCCH window can be defined separately for UL transmission and DL transmission. Thus, two types of (E)PDCCH windows, such as a UL-(E)PDCCH window and a DL-(E)PDCCH window, can be defined. The UL-(E)PDCCH window and the DL-(E)PDCCH window can be mutually exclusive in the time domain. Thus, the WTRU can be required to monitor PUSCH-related DCI or PDSCH-related DCI. Alternatively, the UL-(E)PDCCH window and the DL-(E)PDCCH window can partially or fully overlap in the time domain, and the WTRU can monitor both PDSCH and PUSCH-related DCI in the subframe where the UL-(E)PDCCH window and the DL-(E)PDCCH window overlap.

[0372] In another example, the WTRU-specific search space can be divided into UL-(E)PDCCH windows and DL-(E)PDCCH windows, while the common search space can be placed within both windows. For example, DCI formats related to PDSCH transmission (e.g., 1A / 2 / 2A / 2B / 2C) can be transmitted only within the DL-(E)PDCCH window, and DCI formats related to PUSCH transmission (e.g., 0 / 1) can be transmitted only within the UL-(E)PDCCH window. In this case, the subsequent window can depend on the type of (E)PDCCH window. For example, the PDSCH window can be placed after or always placed after the DL-EPDCCH window, and the PUSCH window can be placed after the UL-(E)PDCCH window.

[0373] In another example, a single (E)PDCCH window can be used for both PDSCH and PUSCH. Thus, the WTRU may need to monitor DCI formats for both PDSCH and PUSCH within the (E)PDCCH window. Here, the subsequent window can depend on the DCI format type within the (E)PDCCH window. For example, if the WTRU can receive a DCI format related to PUSCH, the subsequent window can be a PUSCH window so that the WTRU can transmit PUSCH. On the other hand, if the WTRU receives a DCI format related to PDSCH, the subsequent window can be a PDSCH window so that the WTRU can receive PDSCH within the subsequent window.

[0374] In another example, if the WTRU receives DCI and the CRC is scrambled using the WTRU's C-RNTI and the DCI is related to PDSCH, the WTRU may need to report A / N within the A / N window. The A / N transmission corresponding to PDSCH can be repeatedly transmitted within the A / N window.

[0375] In another example, the (E)PDCCH targeting the WTRU can be transmitted in only a single subframe within the (E)PDCCH window. Thus, if the WTRU receives an (E)PDCCH directed to the WTRU in the WTRU-specific search space in a subframe within the (E)PDCCH window, the WTRU can be enabled / allowed not to monitor the (E)PDCCH in the WTRU-specific search space within the (E)PDCCH window. In other words, if the WTRU successfully receives DCI scrambled with a C-RNTI in the WTRU-specific search space, the WTRU can assume that there is no other DCI scrambled with the C-RNTI in the WTRU-specific search space. This can make it possible to avoid unnecessary WTRU complexity.

[0376] In another example, the (E)PDCCH can be transmitted over multiple subframes within the (E)PDCCH window so that the WTRU can accumulate signals over multiple subframes. Here, the repetition in the same (E)PDCCH candidate can be guaranteed so that the WTRU can accumulate the same (E)PDCCH candidate over multiple subframes within the (E)PDCCH window. Thus, the (E)PDCCH WTRU-specific search space can be fixed within the (E)PDCCH window. Alternatively, the same (E)PDCCH candidate can be used for the repetition, but the WTRU-specific search space can be changed as a function of the subframe number. In another example, the (E)PDCCH candidates can be hopped in a predefined manner so as to increase the time / frequency diversity gain.

[0377] In another embodiment, within the PDSCH window, the WTRU can receive the PDSCH within the PDSCH window and can apply one or more of the following methods. In an example, the PDSCH can be repeatedly transmitted at the same frequency resource within the PDSCH window. For example, if the DCI corresponding to the PDSCH indicates that the PDSCH is arranged within a specific PRB, all of the PRBs can be reserved within the PDSCH window. Therefore, when the WTRU receives the PDSCH, the WTRU can accumulate the signals in the specific PRBs over a plurality of subframes within the PDSCH window for PDSCH decoding. In another example, the PDSCH can be repeatedly transmitted in the frequency domain so that the WTRU can accumulate the PRBs in the frequency domain. Here, the repetition can be based on the PRB level and the same MCS level can be used. Therefore, the WTRU can integrate the signals before demodulation.

[0378] In another example, the PDSCH can be repeatedly transmitted in the time domain and the frequency domain. Here, the frequency domain repetition can be based on the rate matching operation, while the time domain repetition can be based on the data symbol repetition.

[0379] In another example, the PDSCH can be transmitted only in a specific subframe. Here, the DCI for the DL transmission transmitted within the (E)PDCCH window can include the subframe information and the frequency resource information for the PDSCH transmission. For example, if four subframes are used within the PDSCH window, two bits can be used to indicate which subframe includes the PDSCH.

[0380] In another embodiment, if the WTRU receives a PDSCH within the PDSCH window in the A / N window, the WTRU can transmit an A / N within the A / N window. In this case, one or more of the following methods can be applied. In an example, the A / N resource can be allocated as a function of the resource index of the (E)PDCCH corresponding to the PDSCH transmission. For example, if an iterative-based (E)PDCCH is used, the first (E)CCE index of the (E)PDCCH can be used. Alternatively, if the (E)PDCCH is transmitted only in the subframes within the (E)PDCCH window, the A / N resource can be allocated as a function of the resource index and subframe number in which the corresponding (E)PDCCH is transmitted. For example, if four subframes are used within the (E)PDCCH window, the A / N resource can be allocated as a function of the subframe position (e.g., 0, 1, 2, or 3) within the (E)PDCCH window and the first (E)CCE index.

[0381] In another example, the A / N resource can be allocated as a function of the resource index of the PDSCH. For example, if an iterative-based PDSCH is used, the first PRB index for the PDSCH can be used. Alternatively, if the PDSCH is transmitted only in the subframes within the PDSCH window, the A / N resource can be allocated as a function of the resource index and subframe in which the PDSCH is transmitted.

[0382] In another example, the A / N resource can be allocated as a function of the resource indexes of the PDSCH and the corresponding (E)PDCCH. Here, even if multi-user based (E)PDCCH and PDSCH transmissions are used, the first (E)CCE index and the first PRB index can be used simultaneously so as to avoid A / N resource collisions. In another example, the A / N can be transmitted repeatedly within an A / N window. For example, if a PUCCH resource is allocated, the WTRU may need to repeatedly transmit the same A / N signal on the same A / N resource in all subframes between the A / N windows. In another example, the A / N corresponding to the PDSCH can be transmitted only in a subframe. Therefore, the A / N resource can be allocated only in a subframe based on the (E)PDCCH and / or PDSCH used.

[0383] Applications for using a coverage enhancement mode are described herein. The WTRU can apply all embodiments and examples herein, either individually or in combination, as part of a coverage enhancement operating mode.

[0384] The WTRU can operate in a coverage enhancement (enhanced) mode since power on, which can be indicated in its functionality. For example, the WTRU can be preconfigured to start operating in a coverage enhancement mode, and thus can perform cell search, network access (e.g., PRACH process), and other connection mode procedures based on the procedures as described herein instead of legacy procedures, e.g., procedures prior to Release 11.

[0385] The WTRU can switch between legacy operation and a coverage enhancement (enhanced) mode, and can indicate support for the coverage enhancement (enhanced) mode to the network, e.g., as part of the WTRU functionality indication, via RRC signaling.

[0386] The WTRU can switch from normal to coverage enhancement mode using one or more of the following methods. As an example, the WTRU can receive an indication from the network indicating operation in coverage enhancement mode. For example, the WTRU can receive an RRC reconfiguration message having PDCP, RLC, and MAC parameters where the SN size is shortened and other changes are made to the header configuration, as described above.

[0387] In another example, the WTRU can measure and / or detect a change in the environment such that the WTRU can no longer operate in normal mode and can begin operating in coverage enhancement mode. The WTRU can switch under one or more of the following exemplary conditions. As an example, during cell selection / reselection, the WTRU can find a cell that is suitable under coverage enhancement conditions but not suitable under normal operating conditions. For example, the WTRU may not meet the criteria of a suitable cell as defined in the cell's SIB1, but may meet the criteria of a suitable cell using coverage enhancement, as defined, for example, in LC-MTC. In another example, in normal mode, if attempts to access the network and PRACH procedures fail, the WTRU can switch to a coverage enhancement mode PRACH procedure as described herein. In another example, the WTRU can switch during radio link failure detection and subsequent re-establishment to the serving cell. In another example, the WTRU can switch based on connection mode or IDLE mode measurements, the current serving cell RSRP / RSRQ falling below a threshold, or the absence of neighboring cells whose measurements meet the criteria for handover or cell reselection.

[0388] In another example, if PSS / SSS detection takes longer than a certain threshold, the WTRU may switch to a coverage enhancement mode. The threshold can be defined as a time window, such as x ms. In another example, the WTRU may not be able to properly acquire and decode PBCH and / or SIB1, may be able to acquire LC-MIB, and for coverage enhancement purposes as described above, may be able to acquire all or a subset of the SFN through signals from the cell. For example, if the WTRU acquires the configuration necessary for random access, etc., through LC-SIB and SFN values, in order to determine appropriate RACH resources and initiate random access procedures, it can continue cell access and connection establishment procedures (e.g., RRC connection request) in a coverage enhancement mode.

[0389] In another embodiment, the WTRU can indicate to the network a change to a coverage enhancement mode, and / or a request for a change to a coverage enhancement mode, by using one or more of the following methods. In an example, a measurement report that can include a request indication for a change in the operating mode can be transmitted periodically or in response to an event trigger from the network, such as configured in a measurement object. In another example, a PRACH preamble can indicate to the network that the operating mode of the WTRU has changed. In another example, an indication that the WTRU can operate in a coverage enhancement mode can be created within an RRC connection or re-establishment request. For example, this indication can be included as a reason IE within an RRC connection request or re-establishment request message.

[0390] In another embodiment, the WTRU can return from the coverage enhancement mode to the normal operation mode using one or more of the following exemplary methods. In an example, the WTRU can autonomously return to the normal operation mode when it detects an improved coverage state while in the IDLE or connected mode. The detection can be performed using one or more of the following methods. In an example, the WTRU can detect this improvement, for example, by acquiring the legacy MIB and / or SIB using legacy procedures. In another example, the WTRU may be able to meet appropriate cell criteria as specified in the cell's SIB1. For example, this can be part of the cell selection procedure when the WTRU returns from the connected mode to the IDLE mode or as part of the connection establishment for data transmission. In another example, the random access procedure can succeed using the legacy RACH procedure. For example, the WTRU can consider returning to the normal operation state when it receives a response from the eNB indicating that the random access has succeeded within X preamble retransmissions. The threshold X for preamble transmission can be defined as the maximum number of preamble transmissions as defined in SIB2 or as a separate value configured by the cell and can be transmitted as part of the RACH configuration in SIB2. In another example, based on measurements, the WTRU can detect an improvement, for example, in the RSRP measurement value. For example, the WTRU can provide a measurement report to the eNB indicating that the RSRP has improved beyond a pre-defined threshold, i.e., indicating that the normal operation mode may be possible. In another example, the WTRU can indicate an improvement detected based on the power headroom report (PHR) and the transmitted UL power. The trigger for the PHR to the eNB can be triggered, for example, by an improvement in the measured path loss.

[0391] In another embodiment, during RRC connection establishment, the WTRU can indicate a return to the normal operation mode using the normal (e.g., Release 11) reasons defined for the RRC connection request.

[0392] In another embodiment, the eNB can also detect coverage improvement for the WTRU and can indicate to the WTRU to operate normally. This can be done by using one or more of the following methods. In an example, the WTRU can receive an RRC reconfiguration using data radio bearer parameters for a configuration prior to Release 11. In another method, the WTRU can receive an RRC connection release using an indication for the normal operating mode so that the WTRU can perform cell selection to the same cell, for example, using normal Release 11 cell selection procedures and criteria. In another example, the WTRU can receive an RRC message for an intra-cell handover using a dedicated RACH procedure. The WTRU may be able to confirm an improved coverage state using a contention-free RACH procedure. Additionally, the WTRU can reset the MAC, RLC, and PDCP layers so that the traffic bearer enables the normal operating mode.

[0393] An exemplary method for detecting an improved coverage state where the eNB can trigger the above-described signaling for the WTRU to return to the normal operating mode is described herein. In an example, the eNB can detect that the number of HARQ retransmissions and RLC SDU retransmissions has decreased for each data packet that a WTRU in the coverage enhancement mode needs to receive and / or transmit. The eNB can also detect a reduced BLER rate of the data bearer. In another example, the eNB can detect that the transmission power of the WTRU has decreased by a certain threshold based on the closed power control parameters provided to the WTRU for UL transmission. In another example, the eNB can detect an improved UL state based on SRS measurements as transmitted by the WTRU.

[0394] A method for multi-level coverage limitation indication is described herein. In an embodiment, a WTRU can indicate a coverage limitation level by using one or more of the following methods. In an example, the WTRU can report, or be configured to report, the repetition level required for data, control, and / or broadcast channels, including one or more of PUSCH, PDSCH, and (E)PDCCH. For example, if the WTRU requires "n" repetitions for PDSCH for coverage enhancement, it can report "n" so that the eNB can determine the WTRU's coverage limitation level. In another example, the WTRU can directly report RSRP measurement values via higher layer signaling or UL control channels.

[0395] A WTRU in coverage enhancement mode can use one or more of the following modified radio link monitoring (RLM) procedures and radio link failure (RLF) detection procedures. In an example, for synchronization match and synchronization mismatch indications, the WTRU can configure the Q in and / or Q out thresholds as a function of the coverage enhancement mode and / or the amount of coverage enhancement for which the WTRU can be configured. The adjustment of the Q in / Q out thresholds for normal operation can be predefined according to the amount of coverage enhancement or can be communicated to the WTRU by the network. The WTRU can reconfigure the Q in / Q out thresholds based on any reconfiguration of the amount of coverage enhancement. For example, if the WTRU is configured by the network to operate with an amount of coverage enhancement corresponding to a 15 dB coverage enhancement gain, the WTRU can use the RSRP value for the Q in and Q out thresholds that can be decreased by 15 dB or more.

[0396] In another example, the WTRU may configure Q based on the number of repetitions for the (E)PDCCH channel. in and / or Q out thresholds. Q in / Q out The amount of adjustment to the thresholds can be a function of the number of (E)PDCCH repetitions or can be explicitly signaled from the network. The WTRU may configure Q based on a certain channel that can be configured by the eNB using power spectral density (PSD) boosting. in and / or Q out thresholds. For example, the WTRU may reduce the RSRP value for Q based on the PSD boosting of EPDCCH and / or PSS / SSS transmissions from the cell. in and / or Q out

[0397] In an example, the WTRU may configure Q based on the amount of coverage enhancement. in and / or Q out to be longer than 100 ms and 200 ms respectively for the conditional periods. For example, the WTRU may extend the evaluation period based on the number of (E)PDCCH repetitions configured for the current coverage enhancement mode. The conditional periods can be predefined according to the number of (E)PDCCH repetitions or can be signaled by the network.

[0398] In an example, the WTRU may configure Q based on the length of the (E)PDCCH reception window and whether the WTRU was able to correctly decode the (E)PDCCH between reception windows. in and / or Q out conditional periods. For example, a WTRU in coverage enhanced mode may Q between one or more reception windows for decoding the (E)PDCCH. in / Q outIt is possible to evaluate the conditions. If the WTRU can successfully decode the (E)PDCCH addressed to it via any possible RNTI (e.g., C-RNTI, RA-RNTI, temporary C-RNTI), then Q in If the threshold criteria are met, it can be considered that the synchronization is in agreement and indicate it to a higher layer. There may be a situation where the WTRU cannot correctly decode any (E)PDCCH between one or more reception windows, in which case Q out the condition can be considered to be satisfied and indicate the out-of-synchronization state to a higher layer. For example, after a certain number of consecutive out-of-synchronization evaluations defined by the N310 counter and configured by a higher layer, the WTRU can declare a radio link failure. For example, after a certain number of consecutive synchronization evaluations defined by N311, the WTRU can be considered to be synchronized with the network.

[0399] In another example, the WTRU may not perform RLM for RLF detection based on physical layer problems. The WTRU can declare RLF based on indications from the MAC regarding problems related to random access and indications from the RLC regarding the maximum number of retransmissions reached.

[0400] Energy savings for LC-MTC in coverage enhanced mode are described herein. A WTRU in coverage enhanced mode can remain in the connected mode and can be configured using a connected mode DRX configuration. During small data transfers and transmissions, the WTRU can move to an inactive or sleep mode to save energy and reduce power consumption.

[0401] A WTRU in coverage enhanced mode can consider the following, namely, subframes for expected (E)PDCCH reception, subframes for expected PDSCH reception based on DCI from the (E)PDCCH, subframes for expected PHICH reception, subframes for expected PUCCH reception, and subframes for expected PUSCH reception based on DCI from the (E)PDCCH, as the active time for connected mode DRX.

[0402] The WTRU can consider that the expected reception and / or transmission of the above channels also includes the repetitions configured for each channel. For example, the WTRU can use window-based transmission and reception timings in coverage enhanced mode, and the corresponding active time for DRX can include the (E)PDCCH window, PDSCH window, and A / N window. When not in the current active time, the WTRU can move to an inactive or sleep mode for a period of time. The WTRU can consider one or more of the following as opportunities for inactive / sleep mode, namely, there is no data to be transmitted in the buffer, there is remaining time for window-based reception of channels for which data has already been successfully received (e.g., if the WTRU has received and decoded DCI successfully, it can configure the remaining time in the reception window of the (E)PDCCH as an opportunity for inactive mode until the reception window ends), and there is a gap between the reception window and the transmission window for the WTRU HARQ process based on the reception window and transmission window for repetitions.

[0403] The WTRU can provide the network with DRX capabilities that can include the duration of preferred active and / or inactive times as part of the coverage enhancement mode indication and / or configuration. The WTRU can indicate to the network an estimated data transmission period so that the WTRU can have an opportunity to consume excessive power to transmit and receive data at an appropriate time and can appropriately configure the duration of the inactive time after data transmission.

[0404] Generally, a method for physical broadcast channel (PBCH) enhancement includes receiving, at a wireless transmit / receive unit (WTRU) from a base station, system information for an enhanced PBCH (ePBCH). The ePBCH is placed within a set of radio frames that is a subset of the available radio frames. The subset includes fewer radio frames than all of the available radio frames. The WTRU receives the ePBCH within at least one radio frame of the set of radio frames. The available radio frames within a system frame number (SFN) cycle include all of the radio frames within the SFN cycle. The WTRU can receive the ePBCH when it fails to receive the legacy PBCH. The WTRU can receive the ePBCH when it determines that a measurement value is below a threshold. The WTRU can determine a system frame number (SFN) based at least on at least one radio frame in which the ePBCH was received. The WTRU can determine the SFN based at least on at least one radio frame in which the ePBCH was received and a physical cell ID. The WTRU can determine the SFN from at least an offset value within the ePBCH. The ePBCH can be placed within the central six physical resource blocks. Multiple ePBCH transmissions can be received within a radio frame. The WTRU can receive at least two ePBCH transmissions within at least one radio frame, combine the received ePBCHs, and decode system information from the combined ePBCHs.

[0405] Generally, a method for physical random access channel (PRACH) enhancement includes steps of receiving, by a WTRU, a configuration of a legacy PRACH resource and receiving, by the WTRU, a configuration of an enhanced PRACH (ePRACH) resource. The WTRU selects one of the legacy PRACH resource or the ePRACH resource based on a coverage capability. The WTRU determines the coverage capability based on measurement values. An enhanced preamble is transmitted using the ePRACH resource.

[0406] Generally, a method for physical random access channel (PRACH) enhancement includes a step of receiving a configuration of an enhanced PRACH (ePRACH) resource, where, in this specification, the ePRACH resource includes a plurality of ePRACH resource types, and each ePRACH resource type is associated with a coverage capability. The ePRACH resource types can be distinguished from one another by at least one of a preamble format, a preamble repetition, a time resource, and a frequency resource. The WTRU selects an ePRACH resource type based on the coverage capability of the WTRU and transmits an enhanced preamble using the selected ePRACH resource type. The enhanced preamble is at least a repetition of at least a part of the legacy preamble. The WTRU determines the coverage capability based on measurement values. The enhanced preamble is transmitted using the ePRACH resource.

[0407] Generally, a method for physical random access channel (PRACH) enhancement includes receiving a configuration of enhanced PRACH (ePRACH) resources, where the ePRACH resources include a plurality of ePRACH resource groups, and each group is associated with a coverage capability. A WTRU selects an ePRACH resource group based on the coverage capability of the WTRU and uses resources from the selected ePRACH resource group to transmit an enhanced preamble. The enhanced preamble is at least a repetition of at least a part of the legacy preamble. The WTRU determines the coverage capability based on measurement values. The enhanced preamble is transmitted using the ePRACH resources. The enhanced preamble is at least a repetition of at least a part of the legacy preamble. The enhanced preamble includes a plurality of enhanced preamble types, and each type is associated with a coverage capability.

[0408] Embodiment 1. A method for physical broadcast channel (PBCH) enhancement, the method including receiving, at a wireless transmit and receive unit (WTRU), system information for an enhanced (enhanced) PBCH (ePBCH) from a base station.

[0409] 2. The method according to embodiment 1, wherein the ePBCH is arranged within a set of radio frames that is a subset of the available radio frames, and the subset includes fewer radio frames than all the available radio frames.

[0410] 3. The method according to embodiment 1 or 2, further including receiving the ePBCH within at least one radio frame of the set of radio frames.

[0411] 4. The method according to any one of embodiments 1 to 3, wherein the available radio frames within a system frame number (SFN) cycle include all the radio frames within the SFN cycle.

[0412] 5. The method according to any one of embodiments 1 to 4, further comprising the step of receiving an ePBCH when reception of the legacy PBCH fails.

[0413] 6. The method according to any one of embodiments 1 to 5, further comprising the step of receiving an ePBCH when it is determined that the measurement value is below a threshold.

[0414] 7. The method according to any one of embodiments 1 to 6, further comprising the step of determining a system frame number (SFN) based at least on at least one radio frame in which the ePBCH is received.

[0415] 8. The method according to any one of embodiments 1 to 7, further comprising the step of determining an SFN based at least on at least one radio frame in which the ePBCH is received and a physical cell ID.

[0416] 9. The method according to any one of embodiments 1 to 8, further comprising the step of determining an SFN from at least an offset value within the ePBCH.

[0417] 10. The method according to embodiment 1, wherein the ePBCH is arranged within the central six physical resource blocks.

[0418] 11. A wireless transmit / receive unit (WTRU) comprising a receiver configured to receive the configuration of a legacy PRACH resource by the WTRU.

[0419] 12. The WTRU according to embodiment 11, further comprising a receiver configured to receive the configuration of an enhanced (enhanced) PRACH (ePRACH) resource by the WTRU.

[0420] 13. The WTRU according to embodiment 11 or 12, further comprising a processor configured to communicate with a receiver and to select, based on a coverage capability, one of a legacy PRACH resource or an ePRACH resource.

[0421] 14. The WTRU according to any one of embodiments 11 to 13, wherein a plurality of ePBCH transmissions are received within a radio frame.

[0422] 15. The WTRU according to any one of embodiments 11 to 14, further comprising a receiver configured to receive at least two ePBCH transmissions within at least one radio frame.

[0423] 16. The WTRU according to any one of embodiments 11 to 15, further comprising a processor configured to combine received ePBCHs.

[0424] 17. The WTRU according to any one of embodiments 11 to 16, further comprising a processor configured to decode system information from the combined ePBCHs.

[0425] 18. A method for physical random access channel (PRACH) enhancement, the method comprising the step of receiving, at a wireless transmit and receive unit (WTRU), a configuration of an enhanced (enhanced) PRACH (ePRACH) resource.

[0426] 19. The method according to any one of embodiments 1 to 10 and 18, wherein the ePRACH resource comprises a plurality of ePRACH resource types, and each ePRACH resource type is associated with a coverage capability.

[0427] 20. The method according to any one of embodiments 1 to 10 and 18 to 19, wherein an ePRACH resource type can be distinguished from another ePRACH resource type by at least one of a preamble format, a preamble repetition, a time resource, and a frequency resource.

[0428] 21. A method according to any one of embodiments 1 to 10 and 18 to 20, further comprising the step of selecting an ePRACH resource type at a WTRU based on the coverage capability of the WTRU.

[0429] 22. A method according to any one of embodiments 1 to 10 and 18 to 21, further comprising the step of transmitting an enhanced preamble using the selected ePRACH resource type.

[0430] 23. A method according to any one of embodiments 1 to 10 and 18 to 22, wherein the enhanced preamble is at least a repetition of at least a part of a legacy preamble.

[0431] 24. A method according to any one of embodiments 1 to 10 and 18 to 23, wherein the WTRU determines the coverage capability based on measurement values.

[0432] 25. A method according to any one of embodiments 1 to 10 and 18 to 24, wherein the enhanced preamble is transmitted using an ePRACH resource.

[0433] 26. A method for physical random access channel (PRACH) enhancement, the method comprising the step of receiving, at a WTRU, a configuration of an enhanced (enhanced) PRACH (ePRACH) resource.

[0434] 27. A method according to any one of embodiments 1 to 10 and 18 to 26, wherein the ePRACH resource comprises a plurality of ePRACH resource groups, each group being associated with a coverage capability.

[0435] 28. A method according to any one of embodiments 1 to 10 and 18 to 27, further comprising the step of selecting an ePRACH resource group at a WTRU based on the coverage capability of the WTRU.

[0436] The method according to any one of embodiments 1 to 10 and 18 to 28, further comprising the step of transmitting an enhanced preamble using resources from a selected ePRACH resource group.

[0437] The method according to any one of embodiments 1 to 10 and 18 to 29, wherein the enhanced preamble is at least a repetition of at least a part of the legacy preamble.

[0438] The method according to any one of embodiments 1 to 10 and 18 to 30, wherein the WTRU determines a coverage capability based on measurement values.

[0439] The method according to any one of embodiments 1 to 10 and 18 to 31, wherein the enhanced preamble is transmitted using ePRACH resources.

[0440] The method according to any one of embodiments 1 to 10 and 18 to 32, wherein the enhanced preamble is at least a repetition of at least a part of the legacy preamble.

[0441] The method according to any one of embodiments 1 to 10 and 18 to 33, wherein the enhanced preamble includes a plurality of enhanced preamble types, and each type is associated with a coverage capability.

[0442] A method for a wireless transmit / receive unit (WTRU) to bundle a predetermined number of consecutive subframes to enhance coverage, the method including the step of the WTRU encoding data in each of the subframes using different redundancy versions (RVs).

[0443] The method according to any one of embodiments 1 to 10 and 18 to 35, further comprising the step of the WTRU transmitting a plurality of subframes.

[0444] 37. The method according to any one of embodiments 1 to 10 and 18 to 36, wherein data is coded using different RVs according to a subframe index.

[0445] 38. The method according to any one of embodiments 1 to 10 and 18 to 37, wherein data is coded using different RVs according to the position of each subframe among bundled subframes.

[0446] 39. The method according to any one of embodiments 1 to 10 and 18 to 38, wherein a subframe is configured by an evolved Node B (eNB) in a semi-static manner.

[0447] 40. A method for a wireless transmit / receive unit (WTRU) to reduce the overhead of a layer 2 (L2) protocol layer, the method comprising the step of the WTRU adjusting the size of a radio link control (RLC) layer and a packet data convergence protocol (PDCP) protocol data unit (PDU) so that a resulting data PDU having a header portion and a data portion maintains byte alignment.

[0448] 41. The method according to any one of embodiments 1 to 10 and 18 to 40, wherein the WTRU assigns a sequence number (SN) smaller than 7 bits.

[0449] 42. The method according to any one of embodiments 1 to 10 and 18 to 41, wherein the WTRU assigns a sequence number (SN) smaller than 5 bits in the unacknowledged mode (UM).

[0450] 43. The method according to any one of embodiments 1 to 10 and 18 to 42, wherein the WTRU assigns a sequence number (SN) smaller than 10 bits in the acknowledged mode (UM).

[0451] 44. A method for a wireless transmit / receive unit (WTRU) to reduce the overhead of the layer 2 (L2) protocol layer, the method comprising the step of the WTRU scrambling cyclic redundancy check (CRC) bits added to a media access control (MAC) protocol data unit (PDU) using sequence number (SN) bits of a radio link control (RLC) PDU included within the MAC PDU.

[0452] 45. The method according to any one of embodiments 1 to 10 and 18 to 44, further comprising the step of the WTRU removing SN bits from an RLC header.

[0453] 46. The method according to any one of embodiments 1 to 10 and 18 to 45, further comprising the step of the WTRU receiving a MAC PDU.

[0454] 47. The method according to any one of embodiments 1 to 10 and 18 to 46, further comprising the step of the WTRU descrambling CRC parity bits using possible SN values.

[0455] 48. The method according to any one of embodiments 1 to 10 and 18 to 47, further comprising the step of performing a CRC check.

[0456] 49. A method for a wireless transmit / receive unit (WTRU) to reduce the overhead of the layer 2 (L2) protocol layer, the method comprising the step of the WTRU receiving a bundled transmission time interval (TTI) for a physical downlink shared channel (PDSCH).

[0457] 50. The method according to any one of embodiments 1 to 10 and 18 to 49, further comprising the step of the WTRU transmitting a hybrid automatic repeat request (HARQ) acknowledgement (ACK) in an uplink subframe n + k when downlink subframe n is the last subframe within a bundled subframe associated with the PDSCH, where k is a fixed positive integer.

[0458] 51. A method for a wireless transmit / receive unit (WTRU) to reduce the overhead of the layer 2 (L2) protocol layer, the method comprising the step of the WTRU receiving a bundled transmission time interval (TTI) for a physical downlink shared channel (PDSCH).

[0459] 52. The method according to any one of embodiments 1 to 10 and 18 to 51, further comprising the step of the WTRU transmitting a hybrid automatic repeat request (HARQ) positive acknowledgment (ACK) within an uplink subframe n + k when a downlink subframe n includes a physical downlink control channel (PDCCH) associated with the PDSCH.

[0460] 53. The method according to any one of embodiments 1 to 10 and 18 to 52, wherein k is a function of the number of TTIs.

[0461] 54. A method for a wireless transmit / receive unit (WTRU) to enhance a physical hybrid automatic repeat request (HARQ) indicator channel (PHICH) in the downlink, the method comprising the step of the WTRU receiving acknowledgment (ACK) / negative acknowledgment (NACK) information associated with an uplink physical uplink shared channel (PUSCH) transmission using a plurality of PHICH resources.

[0462] 55. The method according to any one of embodiments 1 to 10 and 18 to 54, further comprising the step of the WTRU determining a PHICH resource based on a physical resource block (PRB) index of an uplink resource allocation.

[0463] 56. The method according to any one of embodiments 1 to 10 and 18 to 55, wherein the PRB index is associated with the PRBs used for PUSCH transmission within a single subframe.

[0464] 57. A method for a wireless transmit / receive unit (WTRU) to enhance physical random access channel (PRACH) coverage, the method comprising the step of the WTRU transmitting a first preamble for a random access channel (RACH) procedure.

[0465] 58. The method according to any one of embodiments 1 to 10 and 18 to 57, further comprising the step of the WTRU transmitting a repeated preamble.

[0466] 59. The method according to any one of embodiments 1 to 10 and 18 to 58, wherein the first preamble and the repeated preamble are transmitted using the same resource.

[0467] 60. A wireless transmit / receive unit (WTRU) comprising a processor configured to encode data in each of a plurality of consecutive subframes using different redundancy versions (RVs) to enhance coverage.

[0468] 61. The WTRU according to any one of embodiments 11 to 17 and 60, further comprising a transmitter configured to transmit a plurality of subframes.

[0469] 62. The WTRU according to any one of embodiments 11 to 17 and 60 to 61, wherein the data is encoded using different RVs according to a subframe index.

[0470] 63. The WTRU according to any one of embodiments 11 to 17 and 60 to 62, wherein the data is encoded using different RVs according to the position of each subframe among bundled subframes.

[0471] 64. The WTRU according to any one of embodiments 11 to 17 and 60 to 63, wherein the plurality of consecutive subframes can be configured by an evolved Node B (eNB) in a semi-static manner.

[0472] 65. A method for a wireless transmit - receive unit (WTRU) to operate in a coverage enhancement mode, the method comprising the step of pre - defining or configuring the number of sub - frames for performing transmission time interval (TTI) bundling.

[0473] 66. The method according to any one of embodiments 1 to 10, 18 to 59, and 65, further comprising the step of bundling sub - frames.

[0474] 67. The method according to any one of embodiments 1 to 10, 18 to 59, and 65 to 66, further comprising the step of repeatedly transmitting the bundled sub - frames.

[0475] 68. The method according to any one of embodiments 1 to 10, 18 to 59, and 65 to 67, wherein at least one of the bundling size of the bundled sub - frames or the repetition rate for repeatedly transmitting the bundled sub - frames is configured via signaling of a higher layer.

[0476] 69. The method according to any one of embodiments 1 to 10, 18 to 59, and 65 to 68, further comprising the step of configuring a transmission mode.

[0477] 70. The method according to any one of embodiments 1 to 10, 18 to 59, and 65 to 69, further comprising the step of defining a default value for at least one of the bundling size or the repetition rate.

[0478] 71. The method according to any one of embodiments 1 to 10, 18 to 59, and 65 to 70, further comprising the step of using the default value when the WTRU is configured to operate in a coverage enhancement mode.

[0479] 72. The method according to any one of embodiments 1 to 10, 18 to 59, and 65 to 71, further comprising the step of the WTRU receiving a WTRU - specific configuration for at least one of the bundling size or the repetition rate.

[0480] 73. The method according to any one of embodiments 1 to 10, 18 to 59, and 65 to 72, further comprising the step of the WTRU receiving a physical downlink shared channel (PDSCH) using a default value.

[0481] 74. The method according to any one of embodiments 1 to 10, 18 to 59, and 65 to 73, further comprising the step of the WTRU performing a defined number of attempts to receive the PDSCH.

[0482] 75. The method according to any one of embodiments 1 to 10, 18 to 59, and 65 to 74, further comprising the step of the WTRU increasing at least one of a bundling size or a repetition rate when the physical downlink shared channel (PDSCH) is not received.

[0483] 76. The method according to any one of embodiments 1 to 10, 18 to 59, and 65 to 75, further comprising the step of the WTRU receiving a physical hybrid automatic repeat request indicator channel (PHICH) or a group of PHICHs using one of a packet data control channel (PDCCH) or an enhanced (enhanced) PDCCH (EPDCCH).

[0484] 77. The method according to any one of embodiments 1 to 10, 18 to 59, and 65 to 76, further comprising the step of the WTRU selecting one of a plurality of preconfigured physical random access channel (PRACH) resource types configured with different levels of coverage limitation according to downlink measurement values.

[0485] 78. The method according to any one of embodiments 1 to 10, 18 to 59, and 65 to 77, further comprising the step of the WTRU reporting the selected level of coverage limitation to a base station.

[0486] 79. The method according to any one of embodiments 1 to 10, 18 to 59, and 65 to 78, wherein the WTRU reports a selected level of coverage limitation to the base station via either higher layer signaling or one of the uplink control channels.

[0487] 80. A hybrid automatic repeat request (HARQ) method performed by a wireless transmit / receive unit (WTRU), the method including collecting and decoding physical downlink shared channel (PDSCH) transmissions within a downlink (DL) subframe bundle.

[0488] 81. The method according to any one of embodiments 1 to 10, 18 to 59, and 65 to 80, further including generating a single HARQ positive acknowledgment (ACK) response for transmissions on the uplink (UL).

[0489] 82. The method according to any one of embodiments 1 to 10, 18 to 59, and 65 to 81, further including the WTRU detecting a PDSCH transmission within a first DL subframe.

[0490] 83. The method according to any one of embodiments 1 to 10, 18 to 59, and 65 to 82, further including the WTRU transmitting a HARQ-ACK response in a first UL subframe and then repeating the transmission of the HARQ-ACK response in subsequent UL subframes.

[0491] 84. A method for a wireless transmit / receive unit (WTRU) to bundle a predetermined number of consecutive subframes to enhance coverage, the method including the WTRU encoding data in each of the subframes using different redundancy versions (RVs).

[0492] 85. The method according to any one of embodiments 1 to 10, 18 to 59, and 65 to 84, further including the WTRU transmitting a plurality of subframes.

[0493] 86. The data is the method according to any one of Embodiments 1 to 10, 18 to 59, and 65 to 85, which is coded using different RVs according to the subframe index.

[0494] 87. The data is the method according to any one of Embodiments 1 to 10, 18 to 59, and 65 to 86, which is coded using different RVs according to the position of each subframe among the bundled subframes.

[0495] 88. The subframe is configured by an evolved Node B (eNB) in a semi-static manner, according to the method of any one of Embodiments 1 to 10, 18 to 59, and 65 to 87.

[0496] 89. A method for a wireless transmit / receive unit (WTRU) to reduce the overhead of the layer 2 (L2) protocol layer, the method including the step of the WTRU adjusting the sizes of the radio link control (RLC) layer and the packet data convergence protocol (PDCP) protocol data unit (PDU) so that the resulting data PDU having a header part and a data part maintains byte alignment.

[0497] 90. The WTRU is the method according to any one of Embodiments 1 to 10, 18 to 59, and 65 to 89, which assigns a sequence number (SN) smaller than 7 bits.

[0498] 91. The WTRU is the method according to any one of Embodiments 1 to 10, 18 to 59, and 65 to 90, which assigns a sequence number (SN) smaller than 5 bits in the unacknowledged mode (UM).

[0499] 92. The WTRU is the method according to any one of Embodiments 1 to 10, 18 to 59, and 65 to 91, which assigns a sequence number (SN) smaller than 10 bits in the acknowledged mode (UM).

[0500] 93. A method for a wireless transmit / receive unit (WTRU) to reduce the overhead of the layer 2 (L2) protocol layer, the method comprising the step of the WTRU scrambling cyclic redundancy check (CRC) bits added to a media access control (MAC) protocol data unit (PDU) using sequence number (SN) bits of a radio link control (RLC) PDU included within the MAC PDU.

[0501] 94. The method according to any one of embodiments 1 to 10, 18 to 59, and 65 to 93, further comprising the step of the WTRU removing SN bits from the RLC header.

[0502] 95. The method according to any one of embodiments 1 to 10, 18 to 59, and 65 to 94, further comprising the step of the WTRU receiving a MAC PDU.

[0503] 96. The method according to any one of embodiments 1 to 10, 18 to 59, and 65 to 95, further comprising the step of the WTRU descrambling CRC parity bits using possible SN values.

[0504] 97. The method according to any one of embodiments 1 to 10, 18 to 59, and 65 to 96, further comprising the step of performing a CRC check.

[0505] 98. A wireless transmit / receive unit (WTRU) comprising a processor configured to allocate a set of paging frames (PFs) and paging opportunities (POs).

[0506] 99. The WTRU according to any one of embodiments 11 to 17, 60 to 64, and 98, further comprising a receiver configured to receive a plurality of paging messages on a plurality of paging frames with a predetermined paging radio network temporary identity (P-RNTI) value, and the WTRU accumulates the paging messages for coverage enhancement gain.

[0507] A method for a wireless transmit / receive unit (WTRU) to obtain a system frame number (SFN), the method comprising the steps of: the WTRU receiving and decoding a signal comprising at least one of a full SFN or a subset SFN.

[0508] 101. The method according to any one of embodiments 1 to 10, 18 to 59, 65 to 97, and 100, further comprising the step of: the WTRU integrating or combining similar signals having a full SFN and integrating or combining similar signals having a subset SFN.

[0509] Although the features and elements have been described in specific combinations above, those skilled in the art will understand that each feature or element can be used alone or in any combination with other features and elements. Additionally, the methods described herein can be implemented by a computer program, software, or firmware included in a computer-readable medium and executed by a computer or processor. Examples of computer-readable media include electronic signals (transmitted over a wired or wireless connection) and computer-readable storage media. Examples of computer-readable storage media include, but are not limited to, magnetic media such as read-only memory (ROM), random access memory (RAM), registers, cache memory, semiconductor memory devices, internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks and digital versatile disks (DVDs). The processor associated with the software can be used to implement a radio frequency transceiver for a WTRU, UE, terminal, base station, RNC, or any host computer.

Industrial Applicability

[0510] The method and apparatus can be used for a wireless transmit / receive unit (WTRU) to enhance coverage.

Description of Signs

[0511] 100 Communication system 102, 102a to 102d Wireless Transceiver Unit (WTRU) 104 RAN 106 Core Network 108 PSTN 110 Internet 112 Other Networks 118 Processor 120 Transceiver

Claims

1. A wireless transmit / receive unit (WTRU) comprising: a receiver configured to receive a random access configuration from a base station, the random access configuration including a first random access resource associated with a first repetition factor, the random access configuration including a second random access resource associated with a second repetition factor, the first repetition factor being lower than the second repetition factor; and a transmitter configured to transmit a first preamble using the first random access resource associated with the first repetition factor; and the transmitter further configured to transmit a second preamble using the second random access resource associated with the second repetition factor if a random access response message is not received within a random access response time window. The WTRU of claim 1.

2. The WTRU of claim 1, wherein the transmitter is further configured to repeatedly transmit the first preamble based on the first repetition factor.

3. The WTRU of claim 1, wherein the transmitter is further configured to repeatedly transmit the second preamble based on the second repetition factor.

4. The WTRU of claim 1, wherein the first preamble is transmitted from a first time associated with the first repetition factor and the second preamble is transmitted from a second time associated with the second repetition factor.

5. The WTRU of claim 4, wherein a first subframe is determined for the first time based on the first repetition factor and a second subframe is determined for the second time based on the second repetition factor.

6. The WTRU of claim 1, wherein the first repetition factor is determined to be used based on a comparison of a reference signal received power (RSRP) measurement or a path loss measurement to a threshold.

7. A method implemented by a wireless transmit / receive unit (WTRU), the method comprising: Receiving a random access configuration from a base station, the random access configuration including a first random access resource associated with a first repetition factor, the random access configuration including a second random access resource associated with a second repetition factor, the first repetition factor being lower than the second repetition factor, and Transmitting a first preamble using the first random access resource associated with the first repetition factor Transmitting a second preamble using the second random access resource associated with the second repetition factor on the condition that a random access response message is not received within a random access response time window A method comprising the above steps

8. The method according to claim 7, further comprising repeatedly transmitting the first preamble based on the first repetition factor

9. The method according to claim 7, further comprising repeatedly transmitting the second preamble based on the second repetition factor

10. The method according to claim 7, wherein the first preamble is transmitted from a first time associated with the first repetition factor, and the second preamble is transmitted from a second time associated with the second repetition factor

11. The method according to claim 10, wherein a first subframe is determined for the first time based on the first repetition factor, and a second subframe is determined for the second time based on the second repetition factor

12. The method according to claim 7, wherein the first repetition factor is determined to be used based on a comparison of a reference signal received power (RSRP) measurement or a path loss measurement with a threshold

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