Method and procedure for a downlink physical channel to reduce latency in an extended LTE system

Abstract

To provide a method, a system, and an apparatus for reducing latency in extended LTE transmission.SOLUTION: A method, a system, and an apparatus uses short transmission time interval (sTTI) resource types and sTTI resource configurations for reduced latency transmission. Design for an sTTI indicator for dynamic sTTI resource presence and / or sTTI resource type indication may be disclosed. Embodiments may include sPDCCH blind decoding complexity handling based on the number of sPDCCH regions within a sTTI window. Joint sPDCCH and normal PDCCH (nPDCCH) search space configurations may be disclosed. Reference signal overhead control for sPDCCH / sPDSCH based on the number of bundled sTTI and / or one or more link adaptation parameters (e.g., MCS level) may be disclosed. A sCCE based sPDCCH and sPDSCH transmission scheme may also be disclosed.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] This invention relates to a method and procedure for a downlink physical channel to reduce latency in an extended LTE system. [Background technology]

[0002] Cross-reference of related applications This application claims the interests of U.S. Provisional Patent Application No. 62 / 315,404 filed on 30 March 2016, U.S. Provisional Patent Application No. 62 / 334,886 filed on 11 May 2016, and U.S. Provisional Patent Application No. 62 / 373,046 filed on 10 August 2016, and incorporates all of their contents herein by reference.

[0003] With the emergence of new applications for cellular technology, such as alarm reporting, automotive safety, and factory process control, the importance of low-latency cellular communications, including machine-type communications (MTC), is rapidly increasing. For example, in enhanced LTE (LTE-A) systems, a typical 1ms transmit time interval (TTI) and associated latency is no longer sufficient. Existing applications such as gaming, as well as real-time applications like VoLTE and video conferencing, can also benefit from reduced latency, for example, in terms of a higher perceived quality of experience. [Overview of the project]

[0004] A method for a wireless transceiver unit (WTRU) to receive control information for shortened transmit time interval (sTTI) communication is disclosed. The method may include the steps of receiving a configuration for one or more sTTI resources, receiving an indication of the presence of the configured sTTI resources, and monitoring a shortened PDCCH (sPDCCH) in the configured sTTI resources using several blind decoding candidates. The number of blind decoding candidates may be based on the length of the sTTI. The indication may be received on a physical hybrid ARQ indicator channel (PHICH). The configuration of the sTTI resources may be received in an sTTI indicator. The sTTI indicator may be based on a set of PHICH resources. [Brief explanation of the drawing]

[0005] A more detailed understanding can be gained from the following explanation, provided as an example, along with the attached diagram.

[0006] [Figure 1A] This is a system diagram of an exemplary communication system in which one or more disclosed embodiments may be implemented. [Figure 1B] Figure 1A is a system diagram of an exemplary wireless transceiver unit (WTRU) that may be used in the communication system shown. [Figure 1C] Figure 1A is a system diagram of an exemplary radio access network and an exemplary core network that may be used within the communication system shown. [Figure 2] This diagram shows the conventional Hybrid Automatic Retransmission Request (HARQ) and the HARQ for Shortened Transmit Time Interval (sTTI). [Figure 3] This figure shows the use of legacy EPDCCH for sTTI resource scheduling. [Figure 4] This is an example diagram of a Resource Element Group (REG). [Figure 5] This is an example diagram of a Resource Element Group (REG). [Figure 6]It is a diagram illustrating allocation of Physical Control Format Indicator Channel (PCFICH) Resource Elements (REG) by Physical Cell ID (PCI). [Figure 7] It is a diagram illustrating PCFICH and Physical Hybrid ARQ Indicator Channel (PHICH) REG based on PCI. [Figure 8] It is a diagram illustrating a plurality of short Transmission Time Interval (sTTI) resource types configured in a subframe. [Figure 9] It is a diagram of control region locations for a shortened transmission time interval indicator (sTTI indicator). [Figure 10] It is a diagram of control region locations for a shortened transmission time interval indicator (sTTI indicator). [Figure 11] It is a diagram illustrating association between sTTI physical downlink control channel (sPDCCH) and sTTI physical downlink shared channel (sPDSCH) per sTTI. [Figure 12] It is a diagram illustrating a plurality of sPDCCH and sPDSCH associations. [Figure 13] It is a diagram illustrating use of PHICH resources as an sTTI indicator.

Mode for Carrying Out the Invention

[0007] FIG. 1A is a diagram of an example communication system 100 in which one or more of the disclosed embodiments may be implemented. Communication system 100 may be a multiple-access system that provides content such as audio, data, video, messaging, and broadcast to a plurality of wireless users. Communication system 100 may allow multiple wireless users to access such content through sharing of system resources including wireless bandwidth. For example, communication system 100 may employ 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), and Single-Carrier FDMA (SC-FDMA).

[0008] As shown in Figure 1A, the communication system 100 may include wireless transceiver units (WTRUs) 102a, 102b, 102c, 102d, a radio access network (RAN) 104, a core network 106, a public telephone network (PSTN) 108, the internet 110, and other networks 112, but it should be understood that the disclosed embodiments intend any number of WTRUs, base stations, networks, and / or network elements. Each of the WTRUs 102a, 102b, 102c, and 102d may be any type of device configured to operate and / or communicate in a wireless environment. For example, WTRUs 102a, 102b, 102c, and 102d may be configured to transmit and / or receive wireless signals and may include user equipment (UEs), mobile stations, fixed or mobile subscriber units, pagers, cellular phones, personal digital assistants (PDAs), smartphones, laptops, netbooks, personal computers, wireless sensors, and consumer electronics.

[0009] The communication system 100 may also include base stations 114a and 114b. Each of the base stations 114a and 114b may be any type of device configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, and 102d and to facilitate access to one or more communication networks, such as the core network 106, the internet 110, and / or network 112. For example, base stations 114a and 114b may be transceiver base stations (BTS), node B, evolved node B, home node B, evolved home node B, site controller, access point (AP), wireless router, etc. Although base stations 114a and 114b are shown as single elements, it should be understood that base stations 114a and 114b may include any number of interconnected base stations and / or network elements.

[0010] Base station 114a may be part of RAN 104, which may include other base stations and / or network elements (not shown), such as a base station controller (BSC), a radio network controller (RNC), and relay nodes. Base stations 114a and / or base stations 114b may be configured to transmit and / or receive wireless signals within a specific geographic area, which may be called a cell (not shown). A cell may be further divided into cell sectors. For example, a cell associated with base station 114a may be divided into three sectors. Thus, in one embodiment, base station 114a may include three transceivers, i.e., one transceiver for each sector of the cell. In another embodiment, base station 114a may use multiple input / multiple output (MIMO) technology, and therefore may use multiple transceivers for each sector of the cell.

[0011] Base stations 114a, 114b may communicate with one or more WTRUs 102a, 102b, 102c, 102d via an air interface 116, which may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 may be established using any suitable radio access technology (RAT).

[0012] More specifically, as noted above, the communication system 100 may be a multiple access system and may use one or more channel access schemes such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, etc. For example, base stations 114a and WTRUs 102a, 102b, and 102c in RAN 104 may implement radio technologies such as Universal Mobile Communications System (UMTS) Terrestrial Radio Access (UTRA) which can establish an air interface 116 using broadband CDMA (W-CDMA). WCDMA® may include communication protocols such as High Speed ​​Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA may include High Speed ​​Downlink Packet Access (HSDPA) and / or High Speed ​​Uplink Packet Access (HSUPA).

[0013] In another embodiment, base stations 114a and WTRUs 102a, 102b, 102c may implement radio technologies such as an Evolved UMTS terrestrial radio access network (E-UTRA) that can establish an air interface 116 using Long-Term Evolution (LTE) and / or Enhanced LTE (LTE-A).

[0014] In other embodiments, base stations 114a and WTRUs 102a, 102b, and 102c may implement wireless technologies such as IEEE 802.16 (i.e., WiMAX (Worldwide Interoperability for Microwave Access)), CDMA2000, CDMA2000IX, CDMA2000EV-DO, Provisional Standard 2000 (IS-2000), Provisional Standard 95 (IS-95), Provisional Standard 856 (IS-856), Global Mobile Communications System (GSM®), Extended Data Transfer Rate for GSM Evolution (EDGE), and GSM EDGE (GERAN).

[0015] In Figure 1A, base station 114b may be, for example, a wireless router, home node B, home-evolved node B, or access point, and may use any suitable RAT to facilitate wireless connectivity in local areas such as offices, homes, vehicles, or campuses. In one embodiment, base station 114b and WTRU 102c, 102d may implement radio technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In another embodiment, base station 114b and WTRU 102c, 102d may implement radio technology such as IEEE 802.15 to establish a wireless personal area network (WPAN). In yet another embodiment, base station 114b and WTRU 102c, 102d may use a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, etc.) to establish a picocell or femtocell. As shown in Figure 1A, base station 114b may have a direct connection to the internet 110. Therefore, base station 114b may not be required to access the internet 110 via the core network 106.

[0016] RAN 104 may communicate with core network 106, which may be any type of network configured to provide voice, data, applications, and / or Voice over Internet Protocol (VoIP) services to one or more of WTRU 102a, 102b, 102c, and 102d. For example, core network 106 may provide call control, billing services, mobile location-based services, prepaid calls, internet connectivity, video distribution, etc., and / or implement high-level security functions such as user authentication. Although not shown in Figure 1A, it should be understood that RAN 104 and / or core network 106 may communicate directly or indirectly with other RANs using the same RAT or a different RAT as RAN 104. For example, in addition to connecting to RAN 104, which may be using E-UTRA radio technology, core network 106 may also communicate with another RAN (not shown) using GSM radio technology.

[0017] Furthermore, the core network 106 may act as a gateway for WTRUs 102a, 102b, 102c, and 102d to access the PSTN 108, the Internet 110, and / or other networks 112. The PSTN 108 may include a circuit-switched telephone network providing plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices using common communication protocols such as the Transmission Control Protocol (TCP), User Datagram Protocol (UDP), and Internet Protocol (IP) in the TCP / IP Internet Protocol Suite. Networks 112 may include wired or wireless communication networks owned and / or operated by other service providers. For example, network 112 may include another core network connected to one or more RANs that may use the same RAT as RAN 104 or a different RAT.

[0018] Some or all of the WTRUs 102a, 102b, 102c, and 102d in the communication system 100 may include multimode functionality, i.e., WTRUs 102a, 102b, 102c, and 102d may include multiple transceivers to communicate with different wireless networks via different wireless links. For example, WTRU 102c, shown in Figure 1A, may be configured to communicate with base station 114a, which may use cellular-based radio technology, and base station 114b, which may use IEEE 802 radio technology.

[0019] Figure 1B is a system diagram of an exemplary WTRU 102. As shown in Figure 1B, the WTRU 102 may include a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, a non-removable memory 130, a removable memory 132, a power supply 134, a Global Positioning System (GPS) chipset 136, and other peripherals 138. It should be understood that the WTRU 102 may include any subcombinations of the aforementioned elements while remaining consistent with one embodiment.

[0020] The processor 118 may be a general-purpose processor, a dedicated processor, a conventional processor, a digital signal processor (DSP), multiple microprocessors, one or more microprocessors associated 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. The processor 118 may perform signal coding, data processing, power control, input / output processing, and / or any other functions that enable WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to a transceiver 120, and the transceiver may be coupled to a transmit / receive element 122. Although Figure 1B shows the processor 118 and transceiver 120 as separate components, it should be understood that the processor 118 and transceiver 120 may be integrated together in an electronic package or chip.

[0021] The transmit / receive element 122 may be configured to transmit signals to or receive signals from a base station (e.g., base station 114a) via the air interface 116. For example, in one embodiment, the transmit / receive element 122 may be an antenna configured to transmit and / or receive RF signals. In another embodiment, the transmit / receive element 122 may be an emitter / detector configured to transmit and / or receive, for example, IR signals, UV signals, or visible light signals. In yet another embodiment, the transmit / receive element 122 may be configured to transmit and / or receive both RF signals and optical signals. It should be understood that the transmit / receive element 122 may be configured to transmit and / or receive any combination of wireless signals.

[0022] Furthermore, although the transmit / receive element 122 is shown as a single element in Figure 1B, the WTRU 102 may include any number of transmit / receive elements 122. More specifically, the WTRU 102 may use MIMO technology. Thus, in one embodiment, the WTRU 102 may include two or more transmit / receive elements 122 (e.g., multiple antennas) to transmit and receive wireless signals via the air interface 116.

[0023] The transceiver 120 may be configured to modulate the signal to be transmitted by the transmit / receive element 122 and to demodulate the signal received by the transmit / receive element 122. As noted above, the WTRU 102 may have multimode capabilities. Therefore, the transceiver 120 may include multiple transceivers to enable the WTRU 102 to communicate via multiple RATs, such as UTRA and IEEE 802.11.

[0024] The processor 118 of the WTRU102 may be coupled to a speaker / microphone 124, a keypad 126, and / or a display / touchpad 128 (for example, a liquid crystal display (LCD) display unit or an organic light-emitting diode (OLED) display unit) and may receive user input data from them. The processor 118 may also output user data to the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128. Furthermore, the processor 118 may access information from any type of suitable memory, such as non-removable memory 130 and / or removable memory 132, and store data in them. Non-removable memory 130 may include random access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. Removable memory 132 may include a subscriber identification module (SIM) card, a memory stick, a secure digital (SD) memory card, and the like. In other embodiments, the processor 118 may access information from memory not physically located on the WTRU 102, such as on a server or home computer (not shown), and store data in that memory.

[0025] The processor 118 may be configured to receive power from the power supply 134, distribute power to other components within the WTRU 102, and / or control that power. The power supply 134 may be any suitable device for supplying power to the WTRU 102. For example, the power supply 134 may include one or more dry cell batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel-metal hydride (NiMH), lithium-ion (Li-ion), etc.), a solar cell, a fuel cell, etc.

[0026] Furthermore, the processor 118 may 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 the WTRU 102. In addition to, or instead of, the WTRU 102 may receive location information from base stations (e.g., base stations 114a, 114b) via the air interface 116 and / or determine its location based on the timing of signals received from two or more nearby base stations. It should be understood that the WTRU 102 may acquire location information by any preferred location determination method while remaining consistent with one embodiment.

[0027] Furthermore, the processor 118 may be coupled to other peripherals 138, which may include one or more software and / or hardware modules that provide additional features, functions, and / or wired or wireless connectivity. For example, peripherals 138 may include an accelerometer, an electronic compass (e-compass), a satellite transceiver, a digital camera (for photography 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, and the like.

[0028] Figure 1C is a system diagram of RAN 104 and core network 106 according to one embodiment. As noted above, RAN 104 can communicate with WTRU 102a, 102b, and 102c via air interface 116 using E-UTRA wireless technology. RAN 104 can also communicate with core network 106.

[0029] RAN104 includes evolved nodes B140a, 140b, and 140c, but it should be understood that RAN104 may include any number of evolved nodes B while remaining consistent with one embodiment. Each evolved node B140a, 140b, and 140c may include one or more transceivers to communicate with WTRU102a, 102b, and 102c via the air interface 116. In one embodiment, evolved nodes B140a, 140b, and 140c may implement MIMO technology. Thus, for example, evolved node B140a may use multiple antennas to transmit wireless signals to and receive wireless signals from WTRU102a.

[0030] Each of the evolved nodes B140a, 140b, and 140c may be associated with a specific cell (not shown) and may be configured to handle wireless resource management decisions, handover decisions, user scheduling on uplink and / or downlink, etc. As shown in Figure 1C, the evolved nodes B140a, 140b, and 140c may communicate with each other via the X2 interface.

[0031] The core network 106 shown in Figure 1C may include a mobility management gateway (MME) 142, a serving gateway 144, and a packet data network (PDN) gateway 146. While each of the aforementioned elements is shown as part of the core network 106, it should be understood that any one of these elements may be owned and / or operated by an entity other than the core network operator.

[0032] The MME142 can be connected to each of the evolved nodes B140a, 140b, and 140c within RAN104 via the S1 interface and can function as a control node. For example, the MME142 may be responsible for authenticating users of WTRU102a, 102b, and 102c, activating / deactivating bearers, and selecting a specific serving gateway during the initial attachment of WTRU102a, 102b, and 102c. The MME142 may also provide control plane functionality for switching between RAN104 and other RANs (not shown) using other radio technologies such as GSM or W-CDMA.

[0033] The serving gateway 144 may be connected to each of the evolved nodes B140a, 140b, and 140c in RAN104 via the S1 interface. The serving gateway 144 can generally route and forward user data packets to and from WTRU102a, 102b, and 102c. The serving gateway 144 may also perform other functions, such as anchoring the user plane during handover between evolved nodes B, triggering paging when downlink data is available for WTRU102a, 102b, and 102c, and managing and remembering the context of WTRU102a, 102b, and 102c.

[0034] Furthermore, the serving gateway 144 may be connected to the PDN gateway 146, which provides WTRUs 102a, 102b, and 102c with access to packet-switched networks such as the Internet 110, and facilitates communication between WTRUs 102a, 102b, and 102c and IP-enabled devices.

[0035] The core network 106 can facilitate communication with other networks. For example, the core network 106 can provide WTRU 102a, 102b, and 102c with access to circuit-switched networks such as PSTN 108, and facilitate communication between WTRU 102a, 102b, and 102c and conventional land-line communication devices. For example, the core network 106 may include, or communicate with, an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) acting as an interface between the core network 106 and PSTN 108. Furthermore, the core network 106 may provide WTRU 102a, 102b, and 102c with access to network 112, which may include other wired or wireless networks owned and / or operated by other service providers.

[0036] Furthermore, other networks 112 may be connected to an IEEE 802.11-based wireless local area network (WLAN) 160. The WLAN 160 may include an access router 165. The access router may include gateway functionality. The access router 165 may communicate with multiple access points (APs) 170a, 170b. Communication between the access router 165 and APs 170a, 170b may be via wired Ethernet® (IEEE 802.3 standard) or any type of wireless communication protocol. AP 170a communicates wirelessly with WTRU 102d via an air interface.

[0037] Shortened transmit time intervals (sTTI) can be used to reduce latency. Physical channels designed based on a normal 1TTI (nTTI) length (e.g., 1ms) may not be optimized for, or may not function properly for, shorter TTI lengths (e.g., one or more symbols within a duration). For example, shortening the TTI of a control channel (e.g., a downlink (DL) control channel) or reducing the number of symbols available for the control channel may affect channel performance. Redesigning one or more channels may be necessary to mitigate the performance impact that can result from shortening the TTI.

[0038] Furthermore, the rules for monitoring the control channel are designed for a certain level of blind decoding complexity and battery consumption for a given TTI length. Reducing the TTI by a factor of N increases the number of blind decodings by a factor of N if the same rules are used. A mechanism may be needed to mitigate the potential impact of TTI reduction on blind decoding complexity and battery consumption.

[0039] The terms low-latency transmission, reduced-latency transmission, and sTTI transmission may be used interchangeably. Reduced-latency transmission may use reduced TTI or sTTI. The terms reduced TTI, shortened TTI, sTTI, and rTTI may be used interchangeably. The terms TTI and TTI length may be used interchangeably. Shortened TTI length may refer to a TTI length shorter than another TTI length, which may be a typical normal nTTI or regular TTI length, such as 1 ms or 14 orthogonal frequency division multiplexing (OFDM) symbols. Regular (e.g., normal or legacy) transmission may use nTTI. The terms typical, normal, regular, and legacy may be used interchangeably. Shortened TTI length may be defined by the number of OFDM symbols Ns, where Ns may be less than the number of OFDM symbols for nTTI (e.g., Ns < 14).

[0040] Time, frequency, and / or spatial resources may be configured, predefined, allocated, or indicated as resources for sTTI transmission and / or reception. Resources for sTTI transmission, sTTI resources, sTTI PRB, sTTI subframe, sTTI symbol, sTTI RE, and sTTI antenna ports may be used interchangeably as described herein.

[0041] Time resources may include, but are not limited to, one or more OFDM symbols, one or more SC-FDMA symbols, one or more time slots, one or more subframes, one or more radio frames, and / or one or more time samples. Frequency resources may include, but are not limited to, one or more subcarriers, one or more PRBs, and / or one or more component carriers. Spatial resources may include, but are not limited to, one or more antenna ports, one or more reference signals, one or more cells, one or more physical cell IDs (PCIDs), and / or one or more virtual cell IDs (VCIDs).

[0042] Figure 2 shows an example of a conventional Hybrid Auto Retransmission Request (HARQ) 210 for nTTI and an example of HARQ 220 for shortened transmit time interval (sTTI). In one embodiment, the sTTI length can be between one symbol and one time slot which can be seven symbols. As shown in Figure 2, sTTI may require less processing time and can provide a reduced Hybrid Auto Retransmission Request (HARQ) round-trip time (RTT). An nTTI length of 1 ms may be too long to meet the needs of low-latency communications such as machine-type communications, alarm reporting, automotive safety, factory process control, gaming, and Voice over LTE (VoLTE). The range of reduced latency may include physical channel design with shortened TTI for PDCCH, PDSCH, PUSCH, and PUCCH, reference signal design for shortened TTI physical channel demodulation, and HARQ operation with sTTI.

[0043] One or more components may contribute to the total end-to-end delay for a connected WTRU. These components may include, for example, one or more of the following: scheduling grant acquisition time, TTI, processing time, and hybrid RTT. Requests, grants, HARQ feedback, and / or data transmission may occur according to the timing of subframes, which may have a block or chunk, for example, a fixed or known duration (e.g., 1 ms). This duration may be referred to as TTI. Processing time may be, or include, the time required or used to process the data (e.g., encode and / or decode) and / or signal or control the information. This may be done, for example, in or by the WTRU and / or eNB. Data processing time may be proportional to the TTI and / or the data transport block (TB) size.

[0044] A downlink (DL) control channel may be mapped to at least a portion of a subframe. For example, a DL control channel may be located within a set of OFDM symbols in a subframe (e.g., transmitted within it), such as the first 1-3 or first 2-4 OFDM symbols of the subframe. The range of OFDM symbols that can be used (e.g., 1-3 or 2-4) may be based on the system bandwidth. A DL control channel may be located within one or more subframes. In one embodiment, a DL control channel may be located within any subframe.

[0045] A DL control channel is required for sTTI resource (e.g., sPDCCH) scheduling. Figure 3 shows an example using legacy EPDCCH for sTTI resource scheduling. In Figure 3, a subframe contains a PDCCH region at the beginning of the subframe. The subframe also contains an EPDCCH region occurring within the symbol after the PDCCH over a portion of the bandwidth. The subframe also contains six sPDSCH regions occurring over a portion of the bandwidth allocated for sTTI frequency resources. Each sPDSCH region has a duration of 1 sTTI.

[0046] As shown in Figure 3, the use of legacy PDCCH for sTTI resource scheduling can increase latency depending on the location of sTTI resources within a subframe. Furthermore, using legacy EPDCCHs for sTTI resource scheduling cannot reduce latency because the WTRU may have to wait until the end of the subframe to decode the EPDCCH. If sPDCCHs are located within each sTTI resource, the complexity of blind decoding within a time window (e.g., 1 ms) can be increased by the additional sPDCCH blind decoding operation at the beginning of the legacy EPDCCH.

[0047] The number of symbols that can be used for a DL control channel within a subframe (e.g., 1-3 or 2-4) may be determined according to the control channel overhead. The control channel overhead can be, for example, the amount of control information present in or transmitted within a subframe. The number of symbols that can be used may differ across different subframes. For example, downlink control channel overhead may enable dynamic resource allocation to allow for efficient downlink resource utilization, which can result in higher system throughput. DL control channels that can be transmitted within a subframe may include one or more of the following: Physical Control Format Indicator Channel (PCFICH), Physical Hybrid ARQ Indicator Channel (PHICH), and Physical Downlink Control Channel (PDCCH).

[0048] A DL control channel resource unit can be defined as one or more resource elements (REs) that may be continuous in the frequency domain. In one embodiment, a DL control channel resource unit may include four REs. DL control channel resource elements are sometimes referred to as a REG (resource element group).

[0049] Next, referring to Figures 4 and 5, examples of REGs are shown. Figures 4 and 5 show exemplary definitions of REGs based on the number of cell-specific reference signals (CRS) that may be CRS ports. Figure 4 shows a REG definition in a downlink control channel region with 2Tx cell-specific reference signals (CRS) indicated as RS0 and RS1. Figure 5 shows a REG definition in a downlink control channel region with 4TxCRS indicated as RS0, RS1, RS2, and RS3. If the CRS is located as a DL control channel within the same OFDM symbol, the DL control channel REG may consist of consecutive REs (e.g., 4REs) with exceptions to the RE containing CRSs that may be skipped. In these examples, 3 symbols are used for the DL control channel, but other configurations are possible. For example, a set of symbols that may be used for a DL control channel within a subframe may be referred to herein as the DL control channel region.

[0050] PCFICH can be transmitted within an OFDM symbol (e.g., the first OFDM symbol or symbol 0) in one or more subframes that may contain any subframe. PCFICH may indicate the number of OFDM symbols that can be used for the downlink control channel within the subframe. Dynamic downlink control channel resource allocation at the subframe level can be performed using PCFICH. WTRU can detect the Control Format Indicator (CFI) from PCFICH. The downlink control channel area (e.g., the size of the DL control channel area) can be defined within the subframe according to the CFI value. Table 1 shows an example of a CFI codeword that can be detected from PCFICH. Table 2 shows an example of downlink control channel resource allocation with one or more parameters, such as the CFI value, subframe type, frame structure, and system bandwidth. System bandwidth in DL is DL

[0051]

number

[0052] [Table 1]

[0053] [Table 2]

[0054] PCFICH may not be transmitted and / or used in some subframes, for example, in subframes that do not support PDSCH or in subframes where PDSCH or another DL channel begins with a known symbol or time position. WTRU does not need to attempt to detect PCFICH in subframes where it cannot be transmitted and / or used.

[0055] Several REGs (e.g., 4REGs) may be used for PCFICH transmission, for example, within the first OFDM symbol in a subframe. These REGs may be uniformly distributed across at least a portion of the system bandwidth (e.g., DL system bandwidth) or across the entire system bandwidth. This distribution may utilize frequency diversity gain.

[0056] Referring now to Figure 6, the figure shows the assignment of PCFICH REGs by physical cell ID (PCI). The starting point (e.g., in frequency) of PCFICH transmission may differ according to PCI. Frequency shifting of PCFICH based on cell ID can improve PCFICH detection performance, for example, by avoiding PCFICH between multiple adjacent cells.

[0057] A WTRU may initiate downlink control channel detection within a subframe by decoding the PCFICH to determine the number of OFDM symbols for the downlink control channel within that subframe. A PCFICH detection error may result in the loss of at least one of the following: downlink grants, uplink grants, and PCFICH receptions, for example, since downlink control resources may be defined by the PCFICH.

[0058] A PHICH may be used to transmit an ACK or NACK corresponding to a PUSCH transmitted within an uplink subframe. A PHICH may be transmitted in a distributed manner, for example, over at least a portion of the system bandwidth (e.g., DL system bandwidth) and at least some of the OFDM symbols in the downlink control channel area. The number of OFDM symbols that can be used for a PHICH may be referred to as the PHICH duration. The PHICH duration may be configurable, for example, by higher-layer signaling or broadcast signaling (e.g., in the MIB or SIB). The PHICH resource location (e.g., in frequency) may vary according to PCI and / or the PHICH duration.

[0059] Next, referring to Figure 7, a diagram showing PCI's PCFICH and PHICH REG is shown. Multiple PHICH groups may be defined or used within a cell. A PHICH group may contain multiple PHICHs that have or can have an orthogonal sequence. PHICHs that can be directed to a WTRU may be dynamically defined in resource information provided, for example, within an uplink grant. An uplink grant may be for a PUSCH, where the PHICH may contain an ACK or NACK. Resource information is the lowest PRB index.

[0060]

number

[0061]

number

[0062]

number

[0063] Exemplary PHICH index pairs

[0064]

number

[0065]

number

[0066]

number

[0067]

number

[0068]

number

[0069]

number

[0070] The orthogonal sequence can be determined according to the diffusivity. An example is shown in Table 3.

[0071] [Table 3]

[0072] The HARQ indicator (HI) can be encoded as shown in Table 4, for example. For an affirmative response, HI may be equal to 1, and for a negative response, HI may be equal to 0.

[0073] [Table 4]

[0074] A PDCCH (or PDCCH candidate) may consist of one or more control channel element (CCE) resources, which may be contiguous. One CCE may contain several REGs, such as 9REG. The number of available CCEs (N) CCE ) For example, for the case of 9REG per CCE, N CCE =[N REG It can be defined as / 9], where N REG This could be the number of REGs not associated with PCFICH or PHICH. Table 5 shows an example of the PDCCH format with a number of CCEs that may be consecutive.

[0075] [Table 5]

[0076] A WTRU may, or may need to, monitor one or more PDCCH candidates in order to decode, or successfully decode, a PDCCH format such as DL Control Information (DCI) format that may be directed to the WTRU. A WTRU may decode (e.g., blindly decode) or attempt to decode one or more candidates at each of one or more aggregation levels. The set of PDCCH candidates that a WTRU may, may, may attempt to decode, may need to monitor, may need to decode (e.g., blindly), or may need to attempt to decode may constitute a search space. Table 6 shows examples of search spaces and associated PDCCH candidates.

[0077] [Table 6]

[0078] The number of CCEs may differ for different PDCCH formats, as shown in Table 5, for example. Aggregation levels may correspond to the number of CCEs in a PDCCH format, for example. A set of aggregation levels (e.g., {1, 2, 4, 8}) may be supported or used within a WTRU-specific search space. Another set of aggregation levels (e.g., {4, 8}) may be supported or used within a common search space. A WTRU-specific search space may be a search space configured for a WTRU that a WTRU can monitor. A common search space may be a search space configured for a cell, for example in broadcast signaling, that one or more (e.g., all) WTRUs within a cell can monitor.

[0079] Search space at aggregation level L

[0080]

number

[0081]

Math

[0082]

Math

[0083] WTRU-specific search space at aggregation level L

[0084]

Math

[0085]

Math

[0086] The value of m' may be defined according to one or more of the search space type and configurations for the use of cross-carrier scheduling. Configurations for the use of cross-carrier scheduling may be indicated by configurations accompanied by a carrier indicator field. When cross-carrier scheduling is not used or configured for a serving cell, a control channel for the serving cell (e.g., carrying grants or ACK / NACKs) may be transmitted and / or monitored, for example, on the DL control channel area of ​​that serving cell. When cross-carrier scheduling is used or configured for a serving cell, a control channel for the serving cell (e.g., carrying grants or ACK / NACKs) may be transmitted and / or monitored, for example, on the DL control channel area of ​​another serving cell.

[0087] For example, for a common search space, m' can be defined as m'=m. For a WTRU-specific search space, and for a serving cell monitored by PDCCH, m' is m'=m+M. (L) ·n CI This can be defined as follows. This may apply when the WTRU to be monitored is configured with a carrier indicator field for the serving cell to which a PDCCH candidate applies. CI The value of can be a carrier indicator field value. For WTRU-specific search spaces and for serving cells where a PDCCH is monitored, m' can be defined as m'=m. This may be applicable when the WTRU being monitored is configured, for example, with a carrier indicator field for the serving cell to which a PDCCH candidate applies.

[0088] Resource element (RE) muting can be used to avoid signal collision. For a muted RE, puncturing or rate matching can be used, for example from the perspective of an encoding chain. When puncturing is used, a signal that can be mapped to the punctured RE may not be transmitted, or may be transmitted with zero power in that RE. When rate matching is used, the mapping of signals to REs may avoid mapping to some REs, which may result in other signals not being transmitted.

[0089] In one example, an N-bit encoded bit sequence for a channel, for example (c1,...,c N ) may be an output of a channel encoder that receives a payload or information as an input. The channel encoder may be any channel code, including, for example, a turbo code, a convolutional code, or a Reed-Muller code. The encoded bit sequence may be an input to a mapper.

[0090] An M-symbol modulation symbol sequence, for example (x1,...,x M ) may be an output of a mapper where the encoded bit sequence is modulated with a modulation scheme (e.g., BPSK, QPSK, 16QAM, or 64QAM). Depending on the modulation scheme used, the modulation symbol sequence length M may be less than or equal to N.

[0091] The modulation symbol sequence may be mapped to a set of REs for a channel according to a predefined order. For example, x1,...,x M may be mapped to M REs, and these REs may be used for the channel in the predefined order. If the k-th RE (where k < M) is muted due to collision for example, puncturing is applied to the modulation symbol x kThis could mean that it will not be transmitted. Rate matching can mean that the mapping will skip muted REs and that fewer modulation symbols may be mapped. For one rate-matched RE, M-1 modulation symbols may be mapped and transmitted. For example, x1,...,x M-1 A last modulation symbol may be transmitted, and one last modulation symbol may not be transmitted due to muting at the k-th RE. Puncture can result in the loss of coded bits at the location of the muted RE, while rate matching can result in the loss of coded bits from the last coded bit.

[0092] Hereinafter, RE muting with puncturing may be referred to as "RE puncturing," and RE muting with rate matching may be referred to as "RE rate matching." The term "RE muting" may include RE puncturing and / or RE rate matching.

[0093] In conventional LTE systems, RE muting may be implemented to avoid collisions between different types of signals in the same direction. For example, in DL, PDSCH RE may be muted to avoid collisions with CSI-RS, and PRS RE may be muted to avoid collisions with PSS and SSS. In UL, PUSCH and PUCCH may be shortened to avoid collisions with SRS within UL.

[0094] In one embodiment, one or more sTTI resource types may be used. An sTTI resource type may be associated with and / or determined based on one or more parameters. One parameter may be a frequency position including at least one of PRB positions, component carrier positions, frequency bands, and subcarrier positions. Another parameter may be the amount of frequency resources used, including at least one of several PRBs, several subcarriers, several REs, and several component carriers. Another parameter may be a time position including at least one of DL or UL symbol positions in a subframe, starting DL or UL symbol positions in a subframe, subframe number or starting subframe, and SFN number.

[0095] Another parameter may be a time resource quantity, which includes at least one of several DL symbols (e.g., OFDMA symbols) or UL symbols (e.g., SC-FDMA symbols), several slots, several subframes, several time samples, and several radio frames. The time resource quantity may be a function of, or based on, the number of sTTIs available within a subframe. Another parameter may be a spatial resource, which includes at least one of the associated antenna port number or number, reference signal type (e.g., DM-RS or CRS), associated physical cell ID, and associated virtual cell ID.

[0096] One or more sTTI resource types may be used, configured, allocated, and / or represented for a period of time. This period may be one or more symbols, subframes, radio frames, or slots. This period may be referred to herein as an sTTI time window. The terms sTTI period, sTTI window, sTTI resource type time window, and sTTI time window may be used interchangeably. An sTTI time window may be one or more of an sTTI period, a regular TTI period, and / or subframes.

[0097] The sTTI resource type may refer to resources for sTTI physical downlink control channels (sPDCCH), sTTI physical downlink shared data channels (sPDSCH), sTTI physical uplink shared data channels (sPUSCH), and / or sTTI physical uplink control channels (sPUCCH). The terms sTTI resource type and sTTI type may be used interchangeably. Channels or signals described herein may be represented by abbreviations beginning with s, such as sPDCCH, sPDSCH, sPUSCH, and sPUCCH. In the examples and embodiments described herein, these beginnings may be used to represent abbreviated TTI or sTTI.

[0098] Figure 8 shows a diagram illustrating multiple sTTI resource types configured within a subframe. More specifically, Figure 8 shows an example of a resource configuration with multiple sTTI resource types within a subframe, where non-overlapping frequencies may be used for different sTTI resource types. The first and second sTTI resource types may be located within a non-overlapping set of PRBs.

[0099] As described herein, sTTI resource types may be determined, configured, or predefined for one or more sTTI physical channels (e.g., per sTTI physical channel). For example, a first sTTI resource type (e.g., sTTI type 0) may be used for sPDCCH, and a second sTTI resource type (e.g., sTTI type 1) may be used for sPDSCH. In another example, the first sTTI resource type may be used for downlink physical channels, and the second sTTI resource type may be used for uplink physical channels. In yet another example, the first sTTI resource type may be used for physical shared data channels (e.g., sPDSCH and / or sPUSCH), and the second sTTI resource type may be used for physical control channels (e.g., sPDCCH and / or sPUCCH).

[0100] In another example, a first sTTI resource type may be used for one or more sTTI physical channels using the first sTTI (e.g., an sPDSCH using N symbols, where N could be 2), and a second sTTI resource type may be used for one or more sTTI physical channels using the second sTTI (e.g., an sPDSCH using M symbols, where M could be 7). sTTI physical channels using the first and second sTTI resource types may be transmitted and / or received within the same subframe. sTTI physical channels using the first and second sTTI resource types may be directed to (or to the same WTRU) and / or received by (or by the same WTRU).

[0101] Figure 8 shows an example where sTTI resources overlap in time but not in frequency, but note that there are many different possible configurations for allocating sTTI resources within a subframe. For example, one or more sTTI resource types may be configured within a subframe, and these one or more sTTI resource types may not overlap in time, frequency, and spatial resources. In another example, one or more sTTI resource types may be configured within a subframe, and these one or more sTTI resource types may fully or partially overlap in time, frequency, and / or spatial resources. The terms resource overlap and resource sharing can be used interchangeably. Two or more sTTI resource types may fully or partially overlap in a first resource (e.g., time, frequency, or space), while not overlapping in a second resource (e.g., time, frequency, or space), and the first and second resources may be different. Two or more sTTI resource types may completely or partially overlap in time and / or frequency resources, while different spatial resources may be used for those two or more sTTI resource types. Two or more sTTI resource types may completely or partially overlap in time, while different frequency resources may be used for those two or more sTTI resource types. Two or more sTTI resource types may completely or partially overlap in frequency, while different time resources may be used for those two or more sTTI resource types. Two or more sTTI resource types may be assigned to any other combination of overlapping and non-overlapping time, frequency, and time resources within a subframe.

[0102] One or more of the following parameters may apply to a set of PRBs. One or more PRB allocation types may be used to determine the set of PRBs allocated to an sTTI resource type. A first PRB allocation type may use localized PRBs (e.g., continuous PRBs) to allocate a set of PRBs. A second PRB allocation type may use distributed PRBs (e.g., discontinuous PRBs) to allocate a set of PRBs. The PRB allocation type (or PRB location for a set of PRBs) may be defined (e.g., predefined) and / or determined based on the sTTI resource type. The PRB allocation type (or PRB location for a set of PRBs) may be configured via higher-layer signaling. The PRB allocation type may be configured for one or each of the sTTI resource types, or may be configured to be cell-specific or WTRU-specific. The PRB allocation type (or PRB location for a set of PRBs) may be dynamically represented in one or each of the sTTI time windows.

[0103] One or more sTTI resources having the same sTTI resource type may be used, for example, in an sTTI, an sTTI window, a regular TTI, and / or a subframe. For example, a first sTTI resource may be configured at a first frequency position, and a second sTTI resource may be configured at a second frequency position. The first and second frequency positions do not have to overlap in the frequency domain. The first and second sTTI resources may be of the same sTTI resource type. For example, one or more of the time resource amount, frequency resource amount, and spatial resource may be the same.

[0104] An sTTI resource type can refer to resources for multiple sTTI physical channels, such as sPDCCH and sPDSCH, or sPDSCH and sPUCCH, where the resources for these multiple channels may be related, but may not overlap or even completely overlap. For example, an sTTI resource type can be used for sPDCCH and sPDSCH, where these channels may use the same frequency resources, but sPDSCH may be after sPDCCH in time (e.g., by a configured relationship, a predetermined relationship, or a known relationship).

[0105] A WTRU may transmit, receive, monitor, attempt to receive, or attempt to decrypt one or more sTTIs within an sTTI time window. A WTRU may transmit, receive, monitor, attempt to receive, or attempt to decrypt one or more sTTI resources and / or resource types within an sTTI time window.

[0106] The following description may include sTTI resource presence and / or sTTI resource type indications. In one embodiment, a WTRU may receive or attempt to decode indications for sTTI resource presence and / or one or more sTTI resource types during a certain sTTI time window. The WTRU may receive or attempt to decode these indications within a control channel region that may be located within the sTTI time window. This indicator may be referred to as an sTTI indicator.

[0107] An sTTI indicator is, or may include, an indicator for sTTI resource presence or an indicator for an sTTI resource type. Indicators and indications may be used interchangeably. One or more sTTI indicators may be used for one or more sTTI resources. For example, if multiple sTTI resources are configured or used within an sTTI time window, the presence of the sTTI resources may be indicated by the associated sTTI indicators. The multiple sTTI resources may be of the same sTTI resource type or different sTTI resource types. sTTI indicators may be explicit indications or based on events, signaling formats, timing, etc.

[0108] One or more control regions (e.g., control channel regions) may be located within an sTTI time window, and the WTRU may receive or attempt to decode at least one sTTI indicator in at least one of the control regions. A control region may include a set of time and / or frequency resources. A control region may carry control information and / or one or more control channels. The terms control region and control channel region may be used interchangeably. A control region that may carry an sTTI indicator may be a control region located at the beginning of a period that may be an sTTI time window (e.g., a first control region).

[0109] Figures 9 and 10 show the control region locations for sTTI indicators. In Figure 9, the PDCCH region 910 is located at the beginning of a regular TTI or subframe. The PDCCH region 910 may include indications 940 of presence and / or resource type and the location of sTTI resources within the subframe. In the example in Figure 9, the first frequency domain includes sTTI type 1 resource 920, and the second frequency domain includes sTTI type 0 resource 930. The sTTI type 1 resource 920 and the sTTI type 0 resource 930 overlap in time. In this example, the PDCCH region 910 may include indications 940 of presence and / or resource type and the location of each sTTI region 920, 930.

[0110] Figure 10 shows a subframe that includes a PDCCH region 1010 at the beginning of the subframe. The control region may be within a plurality of sPDCCH regions 1035, 1045 or the first sPDCCH region 1025 among them, as shown in Figure 10. The control region may be within a plurality of sPDCCH regions (e.g., all sPDCCH regions) or the first sPDCCH region among them within a period that may be an sTTI time window (e.g., a regular TTI or subframe).

[0111] A control region that may carry an sTTI indicator may be a PDCCH region (e.g., a legacy PDCCH control region) located within the first N OFDM symbols of a subframe. The value of N may be a defined, determined, or configured value (e.g., N=2) when the subframe contains one or more sTTI resources. The value of N may be dynamically represented from PCFICH. PCFICH may be located within a control region that may carry an sTTI indicator (e.g., a first control region).

[0112] A control region that can carry an sTTI indicator may be a first sPDCCH within an sTTI time window. For example, M sTTIs may be used, configured, or available within an sTTI time window. At least one of the M sTTIs may include an associated sPDCCH. A WTRU may receive, or attempt to receive, at least one sTTI indicator within an sPDCCH in the first sTTI of the M sTTIs.

[0113] A WTRU may monitor, attempt to receive, receive, or attempt to receive sTTI indicators in at least one control region within an sTTI time window. Using the sTTI indicators, the WTRU may determine the presence of at least one sTTI resource within an sTTI time window or another period. An example of such a period might be when the WTRU successfully received or determined the presence of an sTTI indicator. Another possible period might be a later sTTI time window.

[0114] A WTRU may determine the presence of at least one sTTI resource within an sTTI time window based on at least one of the presence, value, or content of an sTTI indicator that may be received within that sTTI time window or another period. An example of another period may be a previous (e.g., immediately preceding) or earlier sTTI time window. If an sTTI resource is configured within an sTTI time window, the WTRU may attempt to receive one or more sPDCCHs within that sTTI resource. If no sTTI resource is configured, the WTRU may not attempt to receive at least some sTTI physical channels within the sTTI time window, or any other physical channels that may be within the sTTI time window. Other physical channels may refer to physical channels different from those that the WTRU monitored, attempted to receive, or received an sTTI indicator from. A control region that may carry an sTTI indicator is part of, or may be included in, an sTTI resource (or resource type) in which the sTTI indicator may indicate presence (or lack thereof).

[0115] The presence of an sTTI resource or sTTI resource type may be determined based on one or more of the following parameters: system parameters, which may include one or more of the following: system bandwidth, physical cell ID, number of slots, number of subframes, and number of SFNs; WTRU-specific parameters, which may include one or more of the following: WTRU-IDs (e.g., C-RNTI, IMSI, sTMSI, etc.); and configuration information for sTTI that can be signaled in higher-layer signaling (e.g., MIB, SIB, or WTRU-specific RRC signaling).

[0116] The following description may include an sTTI resource configuration mechanism. sTTI resources may be configured and / or used. One or more sTTI resources may be configured via higher-layer signaling. sTTI resources may be configured with time / frequency position. An sTTI resource may refer to a resource that can carry at least one sTTI physical channel (e.g., sPDCCH, sPDSCH, sPUCCH, sPUSCH).

[0117] One or more sTTI resources may be configured via DCI. A DCI that may constitute one or more sTTI resources may be monitored by a WTRU, for example, periodically, or at a configured or predetermined time. A DCI scrambled with RNTI associated with at least one sTTI transmission may be used. This DCI may be referred to, for example, as sTTI-RNTI. For example, a DCI scrambled with sTTI-RNTI may be monitored within a subframe, a set of subframes, an SFN, and / or a set of SFNs (for example, a set of SFNs or a set of SFNs that meet certain criteria).

[0118] DCI can constitute one or more sTTI resources. For example, DCI scrambled with sTTI-RNTI may be monitored by a WTRU (e.g., by a base station) in the first subframe of each radio frame. A set of subframes or SFNs may be configured to monitor sTTI-RNTI. DCI scrambled with sTTI-RNTI may be monitored by a WTRU (e.g., by a base station) in a set of subframes or SFNs that can be configured and / or used for sTTI-RNTI.

[0119] sTTI resources can be configured by base stations. WTRUs can receive sTTI resource configurations from base stations, for example. WTRUs can use sTTI resources that may be configured by base stations or other network entities (for example, by transmitting, receiving, or attempting to receive within the sTTI resources).

[0120] A base station may transmit within an sTTI resource, for example, in DL. A WTRU may receive or attempt to receive a transmission within an sTTI resource, for example, in DL. A WTRU may transmit within an sTTI resource, for example, in UL. A base station may receive or attempt to receive a transmission within an sTTI resource, for example, in UL.

[0121] sTTI indicators may be based on, transmitted on, or associated with PHICH resources. In one embodiment, one or more PHICH resources may be located within a control region, such as a PDCCH region or an sPDCCH region, and such region may carry or be used to provide sTTI indicators. For example, one or more sTTI resources may be configured, and the presence of sTTI resources may be indicated by sTTI indicators within an sTTI time window. One or more PHICH resources (e.g., resources that may be configured, reserved, or used for PHICH) may be used to carry at least one sTTI indicator. One or more PHICH resources may be configured and / or used for sTTI indicators.

[0122] PHICH resources are PHICH group indexes.

[0123]

number

[0124]

number

[0125] [Table 7]

[0126] Table 8 shows an example of an sTTI indicator that uses one or more PHICH resources for sTTI resource presence and sTTI resource type indication.

[0127] [Table 8]

[0128] Please note that Tables 7 and 8 provide non-restrictive examples of using PHICH resources to indicate sTTI resource presence and / or sTTI resource types.

[0129] The transmission and / or reception of a indicated HARQ indicator (HI) codeword using the indicated PHICH sequence within the indicated PHICH location by the indicated PHICH group may correspond to the indicated sTTI configuration (for example, within the sTTI window of PHICH transmission and / or reception).

[0130] When using PHICH resources to support an sTTI indicator, one or more of the following parameters may apply: The sTTI indicator for the first sTTI resource and the sTTI indicator for the second sTTI resource may be in different PHICH groups and / or use different PHICH sequences. The sTTI indicator for the first sTTI resource type and the sTTI indicator for the second sTTI resource type may be in different PHICH groups and / or use different PHICH sequences. HI codewords may be used to indicate the presence or type of the sTTI resource. Even or odd PHICH sequences may be used for the sTTI indicator. The presence of the sTTI resource may be indicated by using PHICH sequences with the greatest distance (e.g., indices 0 and 4 for a normal CP) or the least distance (e.g., the number of consecutive sequences).

[0131] Based on the reception of an sTTI indicator using a PHICH resource, the WTRU may determine that an sTTI resource or resource type exists within an sTTI window, such as the sTTI window in which the sTTI indicator or PHICH resource was received. When the WTRU determines that an sTTI resource exists, it may monitor, attempt to receive, and / or receive the sTTI resource. When the WTRU determines that an sTTI resource of a certain sTTI resource type exists, it may monitor, attempt to receive, and / or receive the sTTI resource according to that sTTI resource type.

[0132] One or more PHICH resources that can be used for at least one sTTI indicator may be determined based on system parameters, which may include one or more of the following parameters: system bandwidth, PHICH configuration, physical cell ID, subframe count, and / or SFN count; WTRU-specific parameters, which may include one or more WTRU-IDs (e.g., C-RNTI, full or partial IMSI, sTMSI, etc.); and configuration information for sTTI that can be signaled in higher-layer signaling (e.g., MIB, SIB, or WTRU-specific RRC signaling). A PHICH resource that can carry an sTTI indicator is part of, or may be included in, an sTTI resource (or resource type) in which the sTTI indicator can indicate presence (or absence of presence).

[0133] Signals may be used to carry sTTI indicators. The term sTTI indicator signal may be used to describe a signal that can be used as an sTTI indicator. An sTTI indicator signal may be a predefined signal, a configured signal, or a known signal. An sTTI indicator signal may be associated with one or more sTTI resources and / or sTTI resource types. The presence of an sTTI indicator signal may indicate the presence of the associated sTTI resources and / or sTTI resource types within an sTTI window, such as the sTTI window in which the sTTI indicator signal resides.

[0134] sTTI indicator signals may be transmitted at known locations. For example, a predefined signal may be transmitted at known locations, and the presence of that predefined signal (e.g., an sTTI indicator signal) may determine the presence of sTTI resources.

[0135] The sTTI indicator signal is N of the sTTI time window or sTTI resource. STTI Symbols (for example, the first N) STTICan be located within the symbol. STTI N can be a positive integer, including 1. STTI This can be configured via predefined or higher-layer signaling. STTI This can be determined as a function of one or more of the following parameters, namely the time resource amount of the relevant sTTI resource, the sTTI window length, the number of subframes, the number of slots, and / or SFN, as well as system parameters including frame structure (e.g., TDD, FDD), system bandwidth, and / or physical or virtual cell ID. STTI This can be dynamically indicated from the relevant control channel (e.g., legacy PDCCH).

[0136] The sTTI indicator signal may be a PCFICH. The sTTI indicator signal may be transmitted within the sPDCCH region (e.g., a first sPDCCH region) within the sTTI time window. The sTTI indicator signal may be a known sequence (e.g., Zadovchu sequence, PN sequence, Goley sequence).

[0137] A WTRU may attempt to receive, receive, decode, or attempt to decode sTTI indicator signals to determine the presence of one or more sTTI resources. A WTRU may monitor, receive, attempt to receive, decode, and / or attempt to decode one or more sTTI resources (e.g., sTTI channels such as sPDCCH) when the WTRU determines that one or more sTTI resources exist, for example, based on the reception and / or decoding of sTTI indicator signals (e.g., successful reception and / or decoding), when the WTRU determines that one or more sTTI resources exist, for example, within the sTTI window of the sTTI indicator signal, one or more sTTI resources (e.g., sTTI channels such as sPDCCH).

[0138] A WTRU may skip receiving an sTTI resource (e.g., sPDCCH and / or sPDSCH) if it determines that no sTTI resource (or additional sTTI resource) exists (e.g., it may not attempt to monitor, receive, and / or decode it). A WTRU may skip receiving an sTTI resource (or additional sTTI resource) within an sTTI window if it determines that no sTTI resource (or additional sTTI resource) exists within that sTTI window. A WTRU may determine that no sTTI resource (or additional sTTI resource) exists (e.g., within an sTTI window) if it does not detect, receive, or decode an sTTI indicator signal.

[0139] The WTRU may assume that no sPDCCH and / or sPDSCH are transmitted within an sTTI window or the time corresponding to that sTTI window, during which the WTRU does not detect, receive, or decode an sTTI indicator or sTTI indicator signal.

[0140] Receiving one or more sTTI resources when one or more sTTI resources exist may include monitoring sPDCCHs within the relevant sTTI resources for downlink DCIs (e.g., DCIs indicating DL grants or other DL requests or allocations) and / or uplink DCIs (e.g., DCIs indicating UL grants or other UL requests or allocations), and receiving one or more sPDSCHs within scheduled time, frequency, and / or spatial resources.

[0141] In another embodiment, a set of REGs within a control region (e.g., a PDCCH region or an sPDCCH region) within an sTTI time window may be reserved or used for sTTI indicator signals. The set of REGs may be distributed across the system bandwidth or a portion of the system bandwidth. The set of REGs may be associated with a CCE number (e.g., a certain number of CCEs that may be configured and / or known). The set of REGs may be determined based on at least one of the following parameters: system parameters (e.g., physical or virtual cell ID, system bandwidth), sTTI resource types (e.g., time / frequency / spatial resources, sTTI length), and WTRU-specific parameters (e.g., WTRU-ID, C-RNTI).

[0142] Downlink Control Information (DCI) messages may be used to configure sTTI resources. In one embodiment, DCI may be used to indicate the presence of one or more sTTI resources. For example, DCI may be used to indicate the presence of one or more sTTI resources within an sTTI time window. DCI within an sTTI time window may be used to indicate the presence of one or more sTTI resources within the same sTTI time window or within a different period, such as another sTTI window.

[0143] One or more sTTI resources may be configured via higher-layer signaling. The presence of one or more sTTI resources (e.g., one or more configured sTTI resources) within an sTTI time window may be indicated within a DCI (e.g., a DCI within an sTTI time window or another period such as a previous sTTI time window). DCI may be transmitted within an sTTI window, within a control region. For example, DCI may be transmitted within an sTTI window, within a legacy PDCCH region. DCI may be monitored within a common search space of a control region (e.g., a legacy PDCCH region). Alternatively, DCI may be monitored within a set of PDCCH resources (e.g., legacy PDCCH resources) (e.g., a predetermined set or a configured set). For example, a predetermined or configured set of CCEs (e.g., CCE#16-32) may be used. DCI may be scrambled with sTTI-specific RNTIs (e.g., sTTI-RNTIs). A DCI may indicate the presence of sTTI resources and / or associated sTTI resource types. The presence of sTTI resources may be determined based on the sTTI-specific RNTI used. For example, one or more sTTI-specific RNTIs may be used to indicate the presence of one or more sTTI resources. Each sTTI resource may be associated with a specific sTTI-RNTI. Bitmaps may be used within the DCI to indicate which sTTI resources exist within an sTTI time window.

[0144] DCI can be used to configure sTTI resources within an sTTI time window. For example, time, frequency, and / or spatial resources for an sTTI resource may be represented within the DCI.

[0145] A downlink control channel, referred to as sPDCCH, may be associated with one or more sTTIs. The terms sPDCCH, downlink control channel for sTTI, downlink control information for sTTI, sTTI DCI, and sDCI may be used interchangeably.

[0146] An sPDCCH may be located within an sTTI resource. An sTTI resource may be, or contain, at least one sPDCCH. An sPDCCH may be, or may be referred to as, an sTTI resource. An sPDCCH may be, or may be referred to as, an sTTI resource. The terms sPDCCH resource, sPDCCH region, sPDCCH symbol, sPDCCH subcarrier, and sPDCCH REs may be used interchangeably.

[0147] An sPDCCH resource may be associated with one or more sTTIs. For example, an sPDCCH may be associated with one or more sPDSCHs located within sTTIs that are the same or different from each other, or that are the same or different from the sTTI of the sPDCCH. An sPDCCH may contain scheduling information for the associated one or more sPDSCHs.

[0148] An sTTI may contain at least one sPDCCH. An sTTI may contain at least one sPDSCH that may be associated with an sPDCCH that may be contained within that sTTI. For example, in an sTTI, a subset of sTTI resources may be used for an sPDCCH, and the remainder of sTTI resources may be used for an sPDSCH. A WTRU may monitor or attempt to decode an sPDCCH within an sTTI or sPDCCH region. An sPDCCH may contain one or more scheduled sPDSCHs.

[0149] A WTRU may skip monitoring sPDCCH if it does not need to monitor sPDSCH within a resource (e.g., within an sTTI) where sPDSCH may be scheduled. A WTRU may determine where sPDSCH is scheduled (e.g., within an sTTI) based on the reception of sPDCCH, which includes sPDSCH scheduling (e.g., for an sTTI). For example, two or more sTTIs may overlap, which may be the same length or different lengths. Each sTTI may contain a subset of resources for sPDCCH and a subset of resources for sPDSCH. For each sTTI, sPDCCH and resources for sPDSCH may not overlap. Resources for sPDSCH in a first sTTI may overlap with sPDCCH resources in a second sTTI. If the WTRU determines that an sPDSCH resource is scheduled within a first sTTI, the WTRU does not need to monitor sPDCCH within the sPDCCH resources in the second sTTI. This may be due to overlap with sPDSCH resources scheduled within the first sTTI. The WTRU may monitor sPDCCH within the sPDCCH resources in the second sTTI if the sPDCCH resources in the second sTTI do not overlap with scheduled sPDSCH resources (for example, in the first sTTI). The WTRU may determine that the sPDCCH resources in the second sTTI do not overlap with scheduled sPDSCH resources.

[0150] An sTTI window may contain one or more sTTIs, which may or may not overlap. The sTTIs within an sTTI window may be of the same length or of different lengths. A control channel (e.g., PDCCH or sPDCCH) or control information (e.g., DCI or sDCI) may indicate potential scheduling that may exist within an sTTI window (e.g., a regular TTI or subframe). Potential scheduling may be, or include, at least one of the following parameters: the number of sTTIs, the number of sPDSCHs, the number of sPDCCHs, the number of sTTI control regions, and / or the number of sPDCCH regions. A WTRU may monitor one or more sTTIs within an sTTI window or one or more sPDCCH regions. After receiving an sPDSCH scheduling within or between sTTI windows, the WTRU does not need to monitor sPDCCHs within an sTTI window. A WTRU does not need to monitor an sPDCCH within the sTTI window for resources that overlap with a scheduled sPDSCH. This can happen, for example, when the WTRU receives a scheduling for an sPDSCH and / or determines that the sPDSCH is scheduled.

[0151] An sPDCCH (e.g., DCI) may represent several sPDSCHs that can exist in a set, such as {nl, n2, n3, n4}. This set can be configured, defined, and / or determined. The number of sPDSCHs (e.g., n2) may determine the number of sTTIs (e.g., consecutive sTTIs) that can be used for sPDSCH scheduling within an sTTI window. A WTRU may monitor an sPDCCH or sPDCCH region within an sTTI when the WTRU is not scheduled (e.g., within an sTTI window or within a resource that overlaps with an sPDCCH resource).

[0152] sPDCCH (for example, sDCI) may indicate a set of sTTIs within an sTTI time window for scheduling sPDSCH. For example, a bitmap may be used to indicate which sTTI resources or multiple sTTIs within an sTTI time window may bear an sPDCCH. The sPDCCH region within an sTTI may be used for sPDSCH transmissions, for example, when an sPDSCH can be scheduled within a previous sTTI (for example, by an sPDCCH within an sPDCCH region in a previous sTTI). The sPDCCH region that may be used for scheduling sPUSCH may be reserved and / or not reserved for sPDSCH transmissions. Note that PDCCH may be used instead of sPDCCH, and DCI may be used instead of sDCI.

[0153] Figure 11 shows an example of sPDCCH and sPDSCH associations per sTTI. An sPDCCH may be located within each sTTI, and associated sPDSCHs may be scheduled from sPDCCHs located within the same sTTI.

[0154] Figure 12 shows multiple sPDCCH and sPDSCH associations. An sPDCCH may be associated with one or more sPDSCHs, and the number of sPDSCHs associated with an sPDCCH may be determined based on the sPDCCH cycle.

[0155] Figure 13 illustrates the use of PHICH resources as sTTI indicators. One or more sTTI resources may be configured via higher-layer signaling. A WTRU may receive one or more sTTI indicators associated with one or more sTTI resources within a subframe. A WTRU may monitor sPDCCH within one or more sTTI resources based on the configuration indicated by the sTTI indicators. A WTRU may receive sPDSCH or transmit sPUSCH based on scheduling information from DCI within sPDCCH.

[0156] An sPDCCH cycle can be the time between sPDCCH regions. An sPDCCH cycle can be the period during which an sPDCCH region may exist. An sPDCCH cycle can indicate the number and / or location (e.g., time location) of sPDCCH regions within, for example, an sTTI window (e.g., a normal TTI or subframe).

[0157] One or more of the following parameters may apply to the sPDCCH configuration. The sPDCCH cycle may be determined based on system parameters, WTRU-specific parameters, and / or sTTI resource configuration information. The sPDCCH cycle may be determined as an integer multiple of the sTTI length. Different sPDCCH cycles may be used for the configuration and / or sTTI resources that may be used (e.g., different sTTI resources). An sDCI may be associated with one or more sPDCCHs.

[0158] An sDCI may be associated with an sPDSCH, and one or more sDCIs may be transmitted or monitored within an sPDCCH region. An sDCI (or DCI) may implicitly or explicitly include or identify an associated sTTI, sPDSCH, or sPDSCH region (for example, an associated sTTI, sPDSCH, or sPDSCH region). For example, an sPDCCH or sPDCCH region may be associated with one or more sTTIs, sPDSCHs, and / or sPDSCH regions, and scheduling information for the sTTIs, sPDSCHs, and / or sPDSCH regions may be received via an sDCI within the associated sPDCCH or sPDCCH region.

[0159] An RNTI may be used to indicate an sTTI (e.g., sTTI length or sTTI time position). For example, the CRC of a DCI or sDCI may be scrambled with an RNTI that can correspond to an sTTI that may be used within an sTTI window. An RNTI associated with a particular sTTI may be used for the sDCI. The RNTI may indicate the sTTI length (or sTTI time position) for one or more sPDCCHs associated with the sDCI. An RNTI associated with a particular sTTI may be used to indicate an sTTI for sPDCCH monitoring or an sPDCCH cycle within an sTTI window, for example.

[0160] For example, a set of RNTIs may be used. Each RNTI may be associated with an sTTI, sTTI length, sPDCCH cycle, and / or sPDSCH region. A WTRU may monitor one or more sPDCCHs or sPDCCH regions according to the sTTI length or sPDCCH cycle indicated by the RNTI. A WTRU may monitor one or more sPDCCHs or sPDCCH regions according to the sTTI length or sPDCCH cycle indicated by the RNTI. A WTRU may obtain the sTTI length of an sPDSCH region from an RNTI. A WTRU may use the sTTI length to receive and / or decode a scrambled sPDSCH.

[0161] An RNTI may be used to indicate or identify an sPDSCH or sPDSCH region (for example, by scrambling the CRC with the corresponding RNTI). An RNTI may be used to indicate or identify the time and / or frequency location of one or more sPDCCH regions (for example, by scrambling the CRC with the corresponding RNTI). A WTRU may determine the location of an sPDCCH region and / or sPDSCH region from an RNTI. A WTRU may monitor, receive, attempt to receive, decode, and / or attempt to decode sPDCCH within the determined location. A WTRU may receive and / or decode scheduled sPDSCH from the determined location. The terms sPDSCH, sPDSCH region, and sPDSCH in sTTI may be used interchangeably.

[0162] The locations of sPDCCH candidates that may carry an sDCI (e.g., the number of control channel elements (CCEs) and / or the number of sPDCCH candidates) can determine the associated sTTI locations (e.g., the associated sPDSCH region). The WTRU can determine the locations of the associated sPDSCH from the locations of the sPDCCH. The WTRU can receive and / or decode the scheduled sPDSCH from the determined locations. Bit fields within the sDCI may be used to indicate the associated sPDSCH region.

[0163] In an sTTI, a signal (e.g., a predefined or known signal) may be transmitted to indicate the presence of at least an sPDCCH within that sTTI. This signal may be transmitted within a location within the sTTI (e.g., a predefined or known location). For example, PCFICH may be transmitted within a symbol of the sTTI (e.g., a first symbol) to indicate the presence of at least an sPDCCH within that sTTI. When a signal exists, or is determined to exist by the WTRU, the WTRU may monitor at least an sPDCCH within that sTTI. The signal may indicate at least one of the following: the presence of an sPDCCH within an sTTI, the presence of an sPDCCH within at least one sTTI or sPDCCH region within an sTTI window, the sTTI length, the sPDCCH cycle within an sTTI time window, and the sTTI length for an sPDCCH. The signal may be transmitted within a previous sTTI or sTTI window. The signal may indicate the sPDCCH presence and / or one or more of the above parameters for subsequent or later sTTI or sTTI windows.

[0164] The following description may include sPDCCH resource indicators. In one embodiment, a DCI in a certain sPDCCH search space for each sTTI resource may indicate the presence of an sPDCCH resource. For an indicated sPDCCH resource, the WTRU may need to monitor DCIs that may be associated with the sTTI resource allocation. A DCI indicating the presence of an sPDCCH resource within an sTTI may be referred to as a config-DCI, configuration DCI, or monitoring indicator.

[0165] For example, one or more potential sPDCCH resources may be configured, predefined, used, or determined within a subframe. Whether a WTRU may need to monitor one or more sPDCCH candidates for sPDSCH and / or sPUSCH within the potential sPDCCH resources may be determined based on config-DCI. The term “potential sPDCCH resources” may be used interchangeably with the term “sTTI resources” and may still be consistent with this disclosure.

[0166] config-DCI may be monitored within one or more sPDCCH candidates. One or more sPDCCH candidates that may carry config-DCI may be located in known locations within each potential sPDCCH resource.

[0167] A single sPDCCH candidate may be used. The time / frequency position and / or (E)CCE aggregation level of an sPDCCH candidate capable of carrying config-DCI may be predetermined. For example, a first sPDCCH candidate having the largest (E)CCE aggregation level in the set may be used for config-DCI. The time / frequency position and / or (E)CCE aggregation level of an sPDCCH candidate capable of carrying config-DCI may be configured via higher-layer signaling and / or dynamically indicated from DCI from a control channel region, such as a legacy control channel region (e.g., PDCCH).

[0168] A search space may be defined for config-DCI monitoring. The search space may be common for all WTRUs or for groups of WTRUs. The number of blind code trials for config-DCI monitoring (e.g., the number of sPDCCH candidates for config-DCI monitoring) may be determined as Nbd. Nbd may be predefined, configured, or determined based on at least one of several potential sPDCCH resources within an sTTI time window, several symbols used for sPDCCH resources, several (E)CCEs, or several PRBs used for sPDCCH resources. A common search space may be configured or predefined. The common search space may be determined based on at least one of the sTTI length, several sTTI resources within an sTTI time window (e.g., a subframe), or the number of potential sPDCCH resources within an sTTI time window.

[0169] A specific RNTI may be used for config-DCI. For example, config-DCI-RNTI may be used to scramble the CRC of config-DCI.

[0170] The WTRU may receive, monitor, or attempt to decode one or more sPDCCH candidates that may carry the config-DCI within a potential sPDCCH resource. If the WTRU receives the config-DCI within a potential sPDCCH resource, the WTRU may begin monitoring the sPDCCH candidate for sPDSCH and / or sPUSCH. If the WTRU does not receive the config-DCI within a potential sPDCCH resource, the WTRU may skip monitoring the sPDCCH candidate for sPDSCH and / or sPUSCH.

[0171] The presence of config-DCI within potential sPDCCH resources can determine the presence of sPDCCH candidates for sPDSCH and / or sPUSCH scheduling. A config-DCI may include one or more of the following: a subset of sPDCCH candidate sets that can be monitored by WTRUs for sPDSCH and / or sPUSCH; aggregation levels that can be monitored by WTRUs; or sPDCCH resources for monitoring one or more DCIs associated with sPDSCH and / or sPUSCH.

[0172] The number (Mbd) of sPDCCH candidates for sPDSCH and / or sPUSCH may be indicated from the relevant config-DCI. For example, a WTRU may monitor Nbd sPDCCH candidates for a config-DCI within the potential sPDCCH resources, and a WTRU may monitor Mbd sPDCCH candidates, the Mbd of which may be indicated from the config-DCI.

[0173] WTRU may monitor Mbd sPDCCH candidates for sPDSCH and / or sPUSCH within an sPDCCH resource. WTRU may determine Mbd (e.g., the value of Mbd). Mbd may be determined from or based on the number of sPDCCH candidates for config-DCI (Nbd). Mbd may be determined from or based on the number of potential sPDCCH resources that config-DCI may receive. Mbd may be determined from or based on the number of potential sPDCCH resources within an sTTI time window (e.g., a subframe). Mbd may be determined from or based on the number of sPDCCH resources indicated for monitoring within a potential sPDCCH resource. For example, WTRU may be indicated to monitor an Nsp subset of potential sPDCCH resources, and Mbd may be determined based on the number of sPDCCHs within that subset. The Mbd may be determined from or based on the number of PRBs configured, used, or determined for at least one potential sPDCCH resource. The Mbd may also be determined from or based on the sTTI length associated with the potential sPDCCH resource.

[0174] Nsp potential sPDCCH resources may be configured, determined, used, or indicated, and a WTRU may receive, monitor, or attempt to decode at least one of these Nsp potential sPDCCH resources for config-DCI. Each potential sPDCCH resource may be configured or determined based on one or more parameters, which may include at least one of the following: a start symbol, some symbols, some PRBs, some (E)CCEs, or a reference signal type associated with or that may be used for demodulation. The start symbol of an sPDCCH resource may be determined as a function of the number of sPDCCH resources within an sTTI time window (e.g., a subframe). The number of symbols for an sPDCCH resource may be predetermined, configured, or indicated, for example, by a base station. Potential sPDCCH resources may be configured in a WTRU-specific manner. sTTI windows and sTTI time windows may be used interchangeably.

[0175] In another embodiment, one or more sPDCCH resources within an sTTI time window may be activated or deactivated for monitoring. Activation and / or deactivation may be configured, received, or indicated via higher-layer signaling (e.g., via RRC signaling or via MAC-CE). For example, one or more sPDCCH regions may be used, each sPDCCH region may contain one or more sPDCCH resources. One or more sPDCCH regions may be located within different frequency resources that do not overlap in frequency within an sTTI time window.

[0176] The WTRU may receive indications via higher-layer signaling (e.g., MAC-CE) within subframe nk. These indications may or may not be used to activate (or deactivate) one or more sPDCCH regions associated with subframe n. The WTRU may monitor (or skip monitoring) sPDCCH resources within the activated (or deactivated) sPDCCH regions based on the indications or higher-layer signaling within the subframe. The variable k can be a predefined or configured number.

[0177] A WTRU may be associated with (for example, a single) sPDCCH region, and one or more sPDCCH resources (or potential sPDCCH resources) may be used. One or more sPDCCH resources within an sPDCCH region may be located in different time periods (for example, in different time locations). A config-DCI may be monitored by the WTRU within each potential sPDCCH resource if the associated sPDCCH region is activated.

[0178] An sPDCCH (for example, an sPDCCH region) may contain one or more sPDCCH candidates. For example, an sPDCCH region within an sTTI may contain N SPDCCH Can include candidates, N SPDCCH This can be determined based on at least one of the following parameters: The parameter may be an sPDCCH resource configuration that includes or can identify time and / or frequency resources that can be used. The parameter may be an sTTI resource configuration that includes or can identify time and / or frequency resources that can be used. The parameter may be one or more system parameters. The parameter may be several available resource elements (REs). The number of available REs may exclude, for example, REs that can be used for at least one of the following: cell-specific reference signals, CSI-RS, DM-RS, and RS for sTTI.

[0179] A candidate sPDCCH may carry at least one sDCI that can be used for scheduling one or more sPDSCHs, scheduling one or more sPUSCHs, system information update indication, sPDCCH sequence for initiating PRACH transmissions, and activating or deactivating semi-persistent scheduling of an sPUSCH or sPDSCH.

[0180] sPDCCH candidates may be determined based on one or more shortened TTI control channel elements (sCCEs). One or more sPDCCH candidates may be used, transmitted, and / or monitored within the sPDCCH region. sPDCCH candidates may be determined based on at least one of the following parameters: the number of sCCEs used, the initiating sCCE, the number of initiating sCCEs and sCCEs used, the supported sDCI type, and the sCCE type (e.g., localized or distributed).

[0181] sCCE can be determined or defined as a set of REs within the sPDCCH region. For example, sCCE is a set of consecutive Ns within PRB pairs in a downlink OFDM symbol. SCCE,RE It can be defined or determined as an individual RES. One or more of the following parameters may apply: N SCCE,RE This can be 12. The number of sCCEs in the sPDCCH region may be determined based on the number of PRBs and the number of OFDM symbols used for the sPDCCH region. The reference signal type, the number of antenna poles, and / or the number of antenna poles used for sCCEs may be determined based on (or as a function of) at least one of the sTTI resource type, system parameters, WTRU-specific parameters, the number of associated PRBs, and the transmit mode used for associated sPDCCH transmissions (e.g., CRS-based transmit mode or DM-RS-based transmit mode). sCCEs may be determined, defined, and / or configured together with one or more abbreviated TTI resource element groups (sREGs).

[0182] In another embodiment, a subset of nPDCCH resources may be used as sPDCCH resources. For example, Ncce (E)CCEs may be located within the nPDCCH region, and a subset of (E)CCEs may be used for sPDCCH transmissions. The subset of (E)CCEs may be determined based on one or more of the following parameters. A predefined set of (E)CCEs may be used. For example, the first Ns (E)CCEs (excluding those used for the common search space) may be used as the set of (E)CCEs for sPDCCH transmissions.

[0183] The first Ncom (E)CCEs may be used for the common nPDCCH search space, and Ncom+1 to Ncom+Ns (E)CCEs may be used for sPDCCH transmissions. In one example, Ncom may be 16. A WTRU may attempt to decode, monitor, or receive nPDCCH candidates that do not necessarily contain one or more (E)CCEs used for sPDCCH. For example, if an nPDCCH candidate in the WTRU-specific search space contains one or more (E)CCEs for sPDCCH transmissions, the WTRU may skip monitoring the nPDCCH candidate.

[0184] A subset of (E)CCEs may be constructed via higher-layer signaling. The initial (E)CCE count and / or the number of (E)CCEs may be constructed, for example, via higher-layer signaling. A subset of (E)CCEs may be determined as a function of Ncce. A subset of (E)CCEs may be dynamically represented from DCI in a common search space. A subset of (E)CCEs may be replaced by (E)REG or (E)CCE / (E)REG.

[0185] An sPDCCH search space may be provided and / or used. The sPDCCH search space may include one or more sPDCCH candidates. The sPDCCH search space may be cell-specific, WTRU-specific, and / or physical channel-specific. The sPDCCH search space may include one or more sPDCCH candidates that can be associated with one or more sPDCCH search space types (e.g., cell-specific, WTRU-specific, and / or physical channel-specific).

[0186] A WTRU may attempt to decode, monitor, receive, or attempt to receive sPDCCH candidates within an sPDCCH search space that may be associated with that WTRU. An sPDCCH candidate within an sPDCCH search space may be blind-decoded for an sDCI scrambled with an RNTI that may be associated with the WTRU. The number of blind-decode attempts within an sPDCCH search space may be equal to the number of sPDCCH candidates within that sPDCCH search space.

[0187] In one embodiment, the sPDCCH search space may be defined, configured, or determined per sTTI time window. For example, an sTTI time window may include one or more sPDCCH regions, and a WTRU may monitor or attempt to decode one or more sPDCCH regions within the sTTI time window.

[0188] For example, the total number of blind decoding attempts within an sTTI time window (e.g., the total number of PDCCH candidates) may be divided among (or across or within) the number of sPDCCH regions. If the number of sPDCCH regions increases, the number of blind decoding attempts within an sPDCCH region (e.g., the number of PDCCH candidates) may decrease. The number of sPDCCH candidates within an sPDCCH region may be determined based on the number of sPDCCH regions constructed or determined within an sTTI time window. The terms sPDCCH region and / or sPDCCH search space may be used interchangeably.

[0189] Within an sTTI time window, at least one cell-specific sPDCCH region and at least one WTRU-specific sPDCCH region may be used, configured, and / or determined. The cell-specific and WTRU-specific sPDCCH regions may be located within non-overlapping time / frequency resources. A cell-specific sPDCCH region may be located within a first sPDCCH region within an sTTI time window. A WTRU-specific sPDCCH region may be located within one or more sPDCCH regions that cannot be used as a cell-specific sPDCCH region. A WTRU-specific sPDCCH region may be a subset of a cell-specific sPDCCH region. For example, a cell-specific sPDCCH region may be configured for each sTTI, and a WTRU-specific sPDCCH region may be determined or configured within a subset of sTTIs within an sTTI time window.

[0190] A WTRU may determine several sPDCCH regions within an sTTI time window. The number of sPDCCH regions within an sTTI time window may be determined in a WTRU-specific manner. The number of sPDCCH candidates within an sPDCCH region may be determined based on the TTI length of the sPDCCH region and / or the sTTI length of the associated sPDSCH.

[0191] A WTRU may determine several sPDCCH candidates within an sPDCCH region. Within an sPDCCH region, a WTRU may monitor one or more sPDCCH candidates, for example, a determined number of sPDCCH candidates. The number of sPDCCH candidates within an sPDCCH region may be determined based on the number of sPDSCH (or sTTI) associated with the sPDCCH region. For example, if one sTTI or one sPDSCH is associated with an sPDCCH region, a first number of sPDCCH candidates may be monitored within that sPDCCH region. If multiple sTTIs or multiple sPDSCHs are associated with an sPDCCH region, a second number of sPDCCH candidates may be monitored within that sPDCCH region. The second number of sPDCCH candidates may be greater than the first number of sPDCCH candidates. When an sPDCCH region is associated with an sPDSCH region (or one sTTI), m1 sPDCCH candidates may be monitored within the sPDCCH region. When that sPDCCH region is associated with multiple sPDSCH regions (e.g., sTTIs), m2 sPDCCH candidates may be monitored within the sPDCCH region. The value m2 can be an integer multiple of m1 (e.g., m2 = m1 × K), where K can be the number of sPDSCH regions associated with the sPDCCH region.

[0192] In another embodiment, the sPDCCH search space may be defined, configured, or determined per sTTI. A predefined or configured number of sPDCCH candidates may be monitored within each sPDCCH region. One or more of the following parameters may apply:

[0193] A WTRU may skip monitoring sPDCCH candidates within an sTTI (or sPDCCH region) if one or more of the following conditions are met: sPDSCH can be scheduled within an sTTI or sTTI window, for example, by scheduling it within a previous sPDCCH (e.g., an sPDCCH in a previous sTTI). sTTI can be associated with a WTRU (or WTRU-ID). This association can be predetermined, configured, or dynamically indicated. sTTI may not be used for one or more physical channels, such as sPDCCH and / or sPDSCH. In an sTTI, the resources available for the sTTI may be below a defined (e.g., predefined) or configured threshold. A WTRU may monitor sPDCCH within a subset of sTTIs that can be used for the sPDCCH search space.

[0194] In one example, an nPDCCH search space and one or more potential sPDCCH search spaces may be located within an sTTI time window (e.g., a subframe). The number of nPDCCH candidates that can be monitored by the WTRU may be determined, for example, by the WTRU based on the number of sPDCCH search spaces configured within or existing within an sTTI time window.

[0195] For example, one or more potential sPDCCH search spaces may or may not exist within the sTTI time window. The presence of one or more sPDCCH search spaces may be indicated by indicators described herein (e.g., sTTI resource indicator, config-DCI, etc.). The number of nPDCCH candidates may be determined based on the number of sPDCCH search spaces within the sTTI time window, for example, by WTRU.

[0196] It should be noted that the term "sPDCCH search space" is interchangeable with the terms "sTTI resource," "sPDCCH resource," and "sTTI." If no sPDCCH search space exists within the sTTI time window, the number of nPDCCH candidates may be the same as the number of legacy PDCCH candidates. If a larger number of sPDCCH search spaces are located within or used within the sTTI time window, a smaller number of nPDCCH candidates may be monitored by the WTRU. If the number of sPDCCH search spaces is greater than a predefined or configurable threshold, the WTRU does not need to monitor nPDCCH candidates within its own search space.

[0197] In another embodiment, the nPDCCH search space and one or more potential sPDCCH search spaces may be located within an sTTI time window (e.g., a subframe). Monitoring of the nPDCCH search space may be determined, for example, by a WTRU, based on the nPDCCH type and the presence of one or more sPDCCH search spaces.

[0198] If at least one sPDCCH search space exists, the search space for the first nPDCCH type does not need to be monitored by, for example, a WTRU, while the search space for the second nPDCCH type may be monitored by, for example, a WTRU. For example, the first nPDCCH type may be an EPDCCH, and the second nPDCCH type may be a PDCCH. If an sPDCCH search space exists, an nPDCCH candidate of the first nPDCCH type may be switched to another nPDCCH candidate of the first nPDCCH type.

[0199] A WTRU may be configured with a first nPDCCH type for a WTRU-specific search space. The WTRU-specific search space may be based on a first nPDCCH type (e.g., EPDCCH) if the WTRU does not require monitoring sPDCCH search spaces within a subframe. The WTRU-specific search space may be based on a second nPDCCH type (e.g., PDCCH) if the WTRU requires monitoring one or more sPDCCH search spaces within a subframe.

[0200] The following description may include sPDCCH and nPDCCH collaboration. In one embodiment, a collaborative sPDCCH and a regular PDCCH (nPDCCH) search space may be used. A regular PDCCH (e.g., legacy PDCCH, nPDCCH) search space and an sPDCCH search space may be configured (e.g., collaboratively) within an sTTI time window. For example, a regular PDCCH (nPDCCH) search space (or nPDCCH region) may be located within an sTTI time window. A DCI (e.g., a specific DCI) referred to herein as nTTI may be transmitted within at least one nPDCCH search space.

[0201] An nPDCCH may contain one or more nPDCCH candidates, which may carry one or more nDCIs that can be used for nTTI operation. An nPDCCH may be at least one of a PDCCH, an extended PDCCH (EPDCCH), an MTC PDCCH (M-PDCCH), or a narrowband PDCCH (NB-PDCCH). An nDCI may contain information about the sPDCCH search space. Several sPDCCH candidates may be included in the nDCI. A subset of the sPDCCH region within the sTTI time window may be shown in the nDCI, and the WTRU may monitor sPDCCH candidates within that subset of the sPDCCH region. Several sCCEs within the sPDCCH region may be shown in the nDCI. An sTTI resource configuration, including at least one of the time resource configuration, frequency resource configuration, spatial resource configuration, and sTTI length, may be shown in the nDCI. For example, an sDCI that cannot be transmitted within the relevant sPDCCH region due to collision with other signals or limited resources may be indicated within the nDCI.

[0202] In one embodiment, the nDCI may be used to configure a mode of operation. For example, two modes of operation (e.g., a normal TTI mode and a shortened TTI mode) may be used, and the nDCI may configure, indicate, or (de)activate the associated mode of operation. A WTRU may monitor the nDCI within an nPDCCH region. The WTRU may determine a mode of operation based on the information in the nDCI. The WTRU may monitor PDCCH candidates within one or more PDCCH regions based on the determined mode of operation. If the WTRU determines a first mode of operation (e.g., normal TTI), it may monitor nPDCCH candidates within one or more nPDCCH regions. If the WTRU determines a second mode of operation (e.g., shortened TTI), it may monitor sPDCCH candidates within one or more sPDCCH regions.

[0203] nDCI may be transmitted within at least one and any sTTI time window. An sTTI time window may be a time window for a particular mode of operation. nDCI may be transmitted within a subframe and / or a subset of SFNs. nDCI may be transmitted within a common search space in the nPDCCH region, which can be monitored (for example, commonly) by a WTRU configured for sTTI operation.

[0204] In another embodiment, nDCI may be used as a fallback DCI between at least two operating modes. For example, when a WTRU is configured with a certain operating mode or transmit mode (e.g., sTTI operating mode or sTTI transmit mode), the WTRU may monitor the nPDCCH region to receive nDCI.

[0205] In one embodiment, a WTRU may be dynamically indicated to monitor, attempt to decode, or receive one or more sPDCCH search spaces within an sTTI time window (e.g., a subframe). Based on its indication, the WTRU may determine a set (or subset) of nPDCCH candidates within the nPDCCH search space.

[0206] If a WTRU receives an indication of the presence of one or more sPDCCH search spaces within an sTTI time window, it may skip monitoring nPDCCH search spaces within that sTTI time window. If a WTRU receives an indication that there are no sPDCCH search spaces within an sTTI time window, it may monitor nPDCCH search spaces.

[0207] If a WTRU receives an indication of the presence of one or more sPDCCH search spaces, it may monitor only the nPDCCH common search space and skip monitoring the nPDCCH UE-specific search spaces. The indication of the presence of one or more sPDCCH search spaces may be received in a DCI that can be monitored, received, or signaled within the nPDCCH common search space, or in one or more CCEs within a given nPDCCH region.

[0208] If a WTRU receives an indication of the presence of one or more sPDCCH search spaces within an sTTI time window, it may monitor, attempt to decode, or receive a subset of nPDCCH candidates within the relevant nPDCCH search space within that sTTI time window. Similarly, if a WTRU receives an indication that one or more sPDCCH search spaces are absent within an sTTI time window, it may monitor, attempt to decode, or receive a complete set of nPDCCH candidates within the relevant nPDCCH search space within that sTTI time window.

[0209] The complete set of nPDCCH candidates may be the same as the nPDCCH candidates that the WTRU may need to monitor in its nPDCCH WTRU-specific search if the WTRU is not configured with sPDCCH monitoring or sTTI operating modes. A subset of nPDCCH candidates may be determined based on at least one of the following parameters: the presence of one or more sPDCCH search spaces; the number of sPDCCH search spaces within an sTTI time window that can be defined, determined, or configured as sPDCCH search spaces associated with sTTI; the number of sPDCCH candidates for an sPDCCH search space; and / or the total number of sPDCCH candidates for one or more presented or indicated sPDCCH search spaces.

[0210] The presence of one or more sPDCCH search spaces within an sTTI time window may be indicated within the nPDCCH region. The number of sPDCCH search spaces may be explicitly indicated within a DCI that can be monitored within the nPDCCH region. The sTTI length associated with one or more sPDCCH search spaces may be indicated, and the number of sPDCCH search spaces may be determined as a function of the indicated sTTI length.

[0211] A subset of nPDCCH candidates may be determined based on the CCE aggregation level. For example, if the presence of one or more sPDCCH search spaces is indicated, a subset of CCE aggregation levels may be monitored.

[0212] In another embodiment, a set (or subset) of nDCI types that can be monitored within the nPDCCH search space may be determined based on the presence of one or more sPDCCH search spaces and / or sDCI types within an sTTI time window. One or more sPDCCH search spaces and / or sDCI types within an sTTI time window may be monitored within the sPDCCH search space.

[0213] A WTRU may be indicated, configured, or determined to monitor one or more sDCI types within one or more sPDCCH search spaces. For example, a first sDCI type may be associated with an sPDSCH transmission, and a second sDCI type may be associated with an sPUSCH transmission. If a WTRU is indicated, configured, or determined to monitor a first sDCI type within one or more sPDCCH search spaces within an sTTI time window, the WTRU may monitor a set (or subset) of nPDCCH candidates for nDCI types associated with nPUSCH transmissions and may skip monitoring nPDCCH candidates for nDCI types associated with nPDSCH transmissions.

[0214] A WTRU may monitor nDCI or sDCI for similar transmission directions (downlink or uplink). A WTRU may be scheduled (or assumed to be scheduled) with sPDSCH or nPDSCH within the sTTI time window. A WTRU may be scheduled (or assumed to be scheduled) with sPUSCH or nPUSCH within the sTTI time window.

[0215] If a WTRU is indicated, configured, or determined to monitor the sDCI associated with an sPUSCH transmission within an sTTI time window (e.g., subframe n), that WTRU may skip monitoring the nDCI associated with an nPUSCH transmission within the same sTTI time window (e.g., subframe n). sPUSCH and nPUSCH transmissions within the same sTTI time window may include full or partial overlap of the sPUSCH and nPUSCH transmissions.

[0216] In another example, a WTRU might receive an indication of which subset of sPDCCH candidates it should monitor. For instance, one or more subsets of sPDCCH candidates may be configured, defined, predefined, determined, or predetermined, and one of these subsets may be indicated within the DCI.

[0217] A DL reference signal may be required for sPDSCH and sPDCCH channels. sPDSCH and / or sPDCCH transmissions may be associated with one or more reference signal types (e.g., CRS, DM-RS), antenna ports, and / or precoding granularity. One or more reference signal types may be used. The reference signal type may be determined based on at least one of the following parameters: The parameter may be the scrambling sequence used. For example, parameters used for scrambling sequence initialization (e.g., physical cell ID, WTRU-ID, virtual cell ID) may be used. The parameter may be the reference signal position in the time and frequency grid. The parameter may be the precoding granularity of the reference signal. Within a given precoding granularity, a WTRU may use the reference signal for channel estimation for the same antenna port. The parameter may be a WTRU-specific or cell-specific configuration. The parameter may be the reference signal power. The parameter may be the reference signal overhead within a given time / frequency resource. For example, RS type 0 may have zero reference signal overhead (e.g., no reference signal) for sPDSCH and / or sPDCCH transmission, RS type 1 may have 10% reference signal overhead, and RS type 2 may have 20% reference signal overhead.

[0218] The reference signal type may be determined based on the transmission mode configured for the sPDSCH. The reference signal type may be indicated within the downlink control information associated with the sPDCCH or sPDSCH resource. The downlink control information for an sPDSCH resource may be an sDCI that can be carried within the sPDCCH region. The downlink control information for an sPDCCH resource may be an nDCI that can be carried within the nPDCCH region.

[0219] In one embodiment, the reference signal type associated with an sPDSCH and / or sPDCCH transmission may be determined based on at least one of the following parameters:

[0220] In another embodiment, the presence of the reference signal within the sTTI for sPDSCH and / or sPDCCH may be determined based on the position of the sTTI or the number of sTTIs within the sTTI time window. For example, N sTTI The sTTI is located within the sTTI time window, and each sTTI within the sTTI time window is between 0 and N. sTTI-1 If numbered up to a certain point, the reference signal may exist within a subset of the sTTI numbers (either even-numbered sTTIs or odd-numbered sTTIs) (for example, only within them).

[0221] A method is required for sPDCCH resource allocation. In one embodiment, sCCE may be defined, configured, and / or used within the sTTI resource. sCCE may be used for sPDCCH and / or sPDSCH transmissions. For example, a subset of sCCE may be used for sPDCCH transmissions, and the remainder of sCCE may be used for sPDSCH transmissions.

[0222] An sTTI resource may be defined, configured, or determined based on a set of sCCEs. The number of sCCEs in an sTTI resource may be determined based on the time / frequency resource used for the sTTI. A first subset of sCCEs in an sTTI resource may be defined or determined as an sPDCCH region, and a second subset of sCCEs in an sTTI resource may be defined or determined as an sPDSCH region. A WTRU may receive sDCI within the sPDCCH region, and that WTRU may receive the associated sPDSCH within the sPDSCH region. The first and second subsets of sCCEs may be mutually exclusive. The first and second subsets of sCCEs may overlap completely or partially.

[0223] The sPDCCH region may be determined based on the sPDCCH candidate used for sDCI transmission. The number of sCCEs for the sPDCCH region may be determined based on the number of sCCEs used for sPDCCH transmission, and the remaining sCCEs may be considered the sPDSCH region. The number of sCCEs used for sPDCCH transmission may be indicated from the associated sDCI for sPDSCH transmission.

[0224] The sPDCCH area may be determined based on the number of sCCEs used for sDCI transmission. The sPDSCH area (or sPDSCH resource allocation) may be dynamically indicated from the relevant sDCI. For example, the starting number of sCCEs and the ending number of sCCEs may be indicated. If one or more sCCEs are not used for sPDCCH transmission, an sTTI resource configured for sPDCCH may be used for sPDSCH transmission.

[0225] In another embodiment, one or more sPDCCH candidates may be used for sPDSCH transmission. For example, an sTTI resource may be defined as an sPDCCH search space, and one or more sPDCCH candidates within the sPDCCH search space may be used for sPDSCH transmission. The number of sPDCCH candidates may be indicated for sPDSCH transmission. The start and end number of sPDCCH candidates may be indicated from the relevant sDCI for sPDSCH transmission.

[0226] System Information (SI) updates may be provided in sTTI operation. The WTRU monitors the nPDCCH common search space and may receive a DCI with a P-RNTI for SI updates. A DCI with a P-RNTI may contain scheduling information for the PDSCH, which may include a paging message. The paging message may contain at least one of the following: SI updates, Earthquake and Tsunami Warning System (ETWS), Commercial Mobile Alert Service (CMAS), or Extended Access Barring (EAB) parameters. Hereinafter, SI updates, ETWS, CMAS, and / or EAB may all be referred to as “direct indications.” Direct indications may also include a valueTag and SI updates per SI message.

[0227] When a WTRU monitors the nPDCCH search space within a subframe, it may attempt to receive indications directly from paging messages. If one or more sPDCCH search spaces exist, the WTRU may attempt to receive indications directly from DCIs within the sPDCCH search space. Candidate sPDCCHs for DCIs that can bear direct indications may be monitored in a known location (e.g., the sPDCCH common search space). One or more candidate sPDCCHs for DCIs that can bear direct indications may be monitored by the WTRU. DCIs that can bear direct indications may be scrambled with a specific RNTI (e.g., a direct RNTI).

[0228] A WTRU may attempt to receive direct indications from DCIs in the nPDCCH search space if one or more sPDCCH search spaces exist. Candidate nPDCCHs for DCIs that can carry direct indications may be monitored in a known location (e.g., the nPDCCH common search space). One or more candidate nPDCCHs for DCIs that can carry direct indications may be monitored by the WTRU. DCIs that can carry direct indications may be scrambled with a specific RNTI (e.g., a direct RNTI).

[0229] In another embodiment, the WTRU may skip monitoring one or more sPDCCH candidates within a subframe if the UE may need to monitor a DCI that has a P-RNTI. For example, if the UE may need to monitor a paging message in the nPDCCH common search space, that UE may skip monitoring one or more sPDCCH candidates within a subframe.

[0230] RE muting of sTTI resources may be performed. For example, one or more REs within an sTTI resource (e.g., sPDCCH, sPDSCH) may be muted if those REs are used, configured, and / or occupied for one or more reference signals. Reference signals may include, but are not limited to, at least one of the following: periodic CSI-RS, aperiodic CSI-RS, demodulated RS (DM-RS), cell-specific RS (CRS), and positioning RS (PRS). One or more of the following parameters may apply:

[0231] The presence of a reference signal within an sTTI resource can be determined based on the configuration of a higher layer. Therefore, the presence of a reference signal (e.g., periodic CSI-RS, CRS, or PRS) may be known to the WTRU for the sTTI time window.

[0232] The presence of a reference signal and / or reference signal configuration within an sTTI resource may be dynamically indicated within a DCI. A DCI may be received, monitored, decoded, and / or transmitted within one or more of the following resources and according to one or more of the following parameters. A DCI may include configuration information for the presented reference signal. For example, one or more CSI-RS reuse patterns may be indicated within a DCI, and the REs to be used for the indicated one or more CSI-RS reuse patterns may be muted.

[0233] DCI may be monitored within the nPDCCH region. Indications may be transmitted within a DCI which may be used to indicate the presence of one or more sTTI resources or one or more sPDCCH search spaces. If a reference signal is presented within one or more associated sPDSCH transmissions, an indication may be transmitted within an sDCI associated with one or more sPDSCH transmissions. A reference signal configuration may include one or more CSI-RS reuse patterns, a set of frequency resources on which the CSI-RS transmit power reference signal of the indicated one or more CSI-RS reuse patterns is presented, and at least one of several consecutive subframes on which the reference signal is presented.

[0234] RE muting is sometimes referred to as RE puncturing or RE rate matching. The use of RE puncturing or RE rate matching may be indicated dynamically for a given reference signal. For example, RE rate matching may be used for periodic CSI-RS, while RE muting (RE puncturing or RE rate matching) may be indicated within DCI for aperiodic CSI-RS. DCI for RE muting type indication may be monitored within a common search space (e.g., the nPDCCH common search space).

[0235] In some cases, the number of available REs within an sTTI resource (e.g., an sPDCCH resource and / or an sPDSCH resource) may be used to determine whether a WTRU monitors the sPDCCH search space. For example, a WTRU may calculate, determine, estimate, or count the number of available REs within an sTTI resource. If the number of available REs within an sTTI resource is below a threshold, the WTRU may skip monitoring the corresponding sPDCCH.

[0236] One or more of the following may be considered unavailable REs: reference signals (e.g., periodic CSI-RS, non-periodic CSI-RS, IMR, CRS, DM-RS, PRS, and discovery RS), physical broadcast channels (PBCH), synchronization signals (e.g., PSS or SSS), and nPDCCH.

[0237] The threshold can be determined as a function of the sTTI length. For example, if a first sTTI length (e.g., 2 symbols) is used, a first threshold number (e.g., N1) may be used, and if a second sTTI length (e.g., 7 symbols) is used, a second threshold number (e.g., N2) may be used. One or more threshold numbers can be predefined, configured, or dynamically represented. The relevant threshold number can be dynamically represented in the DCI, which is used to indicate presence within the sTTI resource within the sTTI time window. The DCI can be monitored within the nPDCCH region (e.g., the nPDCCH common search space or a known location within the nPDCCH region).

[0238] The threshold number can be determined as a function of the number of frequency resources used for the sTTI resource. Periodic CSI-RS, which can be constructed via higher-layer signaling, may be considered unavailable REs, while aperiodic CSI-RS, which can be shown within DCI, may be considered available REs.

[0239] In another embodiment, the number of sTTI resources for downlink transmission (e.g., sPDSCH and / or sPDCCH) may be determined based on the number of available REs in the sTTI resources. For example, if the number of available REs for an sTTI resource is lower than a threshold, the sTTI resource may be used (or bundled) together with one or more consecutive sTTI resources within an sTTI time window.

[0240] If the number of available REs for an sTTI resource (e.g., resource #n) within an sTTI time window is lower than a threshold, the number of available REs may be counted by combining the next sTTI resource (e.g., sTTI resource #n+1). If the number of available REs for the combined (or bundled) sTTI resources is higher than the threshold number, a WTRU may monitor the sPDCCH search space within those combined (or bundled) sTTI resources. The timing of HARQ-ACK and sPUSCH transmission may be based on the latest sTTI resource in the bundled sTTI resources. If K sTTI resources are combined or bundled, the effective sTTI length may be increased by K times.

[0241] The number of sPDCCH candidates in each sPDCCH region for blind decoding may be determined based on the number of sTTI resources in a subframe. When the number of sTTI resources in a subframe is larger, fewer sPDCCH candidates may be monitored. A common search space definition for legacy PDCCH and sPDCCH may be used for dynamic configuration between normal TTIs and shortened TTIs. Fallback DCI may be monitored in the common search space.

[0242] A set of sCCEs may be used in an sTTI resource, and sPDCCH and sPDSCH may be transmitted in mutually exclusive subsets of sCCEs. A first subset of sCCEs may be determined as sPDCCH that carries DCI for sPDSCH scheduling in an sTTI resource. The remaining sCCEs may be used to transmit sPDSCH.

[0243] Although features and elements are described above in specific combinations, those skilled in the art will understand that each feature or element may be used alone or in any combination with other features and elements. Furthermore, the methods described herein may be implemented in a computer program, software, or firmware incorporated in a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (transmitted via a wired or wireless connection), and computer-readable storage media. Examples of computer-readable storage media include, but are not limited to, read only memory (ROM), random access memory (RAM), registers, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, optical media such as CD-ROM disks, and digital versatile disks (DVDs). A processor associated with software may be used to implement a radio frequency transceiver for use in a WTRU, UE, terminal, base station, RNC, or any host computer.

Claims

1. A wireless transceiver unit (WTRU), Processor and Transceiver and, Equipped with, The transceiver is configured to receive configuration information that indicates the position of a monitoring indicator and constitutes a first set of normal physical downlink control channel (nPDCCH) candidates and a second set of nPDCCH candidates. The transceiver is configured to receive a first transmission including first downlink control information (DCI), wherein the first DCI includes the monitoring indicator at the indicated position. The processor and the transceiver are configured to monitor a first set of nPDCCH candidates within a time window based on the monitoring indicator, and to skip monitoring a second set of nPDCCH candidates within the time window. The processor and the transceiver are configured to decode a second transmission detected in a first set of nPDCCH candidates and receive a second DCI in a WTRU.

2. The WTRU according to claim 1, wherein the second DCI includes information indicating at least one of a downlink grant or an uplink grant.

3. The WTRU according to claim 1, wherein the first set of nPDCCH candidates is associated with a legacy PDCCH search space, and the second set of nPDCCHs is associated with an extended PDCCH (ePDCCH) search space.

4. The WTRU according to claim 1, wherein the position of the monitoring indicator is indicated by at least a time resource.

5. The WTRU according to claim 2, wherein the transceiver is configured to receive physical downlink shared channel (PDSCH) transmissions based on the downlink grant indicated by the second DCI.

6. A method performed by a wireless transceiver unit (WTRU), Receiving configuration information that indicates the position of a monitoring indicator and constitutes a first set of normal physical downlink control channel (nPDCCH) candidates and a second set of nPDCCH candidates, The process involves receiving a first transmission including first downlink control information (DCI), wherein the first DCI includes the monitoring indicator at the indicated position, Based on the monitoring indicator, the first set of nPDCCH candidates is monitored within the time window, and the monitoring of the second set of nPDCCH candidates is skipped within the time window. Decode the second transmission detected in the first set of nPDCCH candidates to receive the second DCI, Methods that include...

7. The method according to claim 6, wherein the second DCI includes information indicating at least one of a downlink grant or an uplink grant.

8. The method according to claim 6, wherein a first set of nPDCCH candidates is associated with a legacy PDCCH search space, and a second set of nPDCCHs is associated with an extended PDCCH (ePDCCH) search space.

9. The method according to claim 6, wherein the position of the monitoring indicator is indicated by at least a time resource.

10. The method according to claim 6, comprising receiving a physical downlink shared channel (PDSCH) transmission based on a downlink grant indicated by the second DCI.

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