WTRU and method performed thereby

Abstract

The WTRU may receive downlink control information (DCI) indicating the start of a frame. The DCI may be received on a control channel, such as a physical downlink control channel (PDCCH), from an eNB, a base station, an AP, or other infrastructure equipment operating in a wireless communication system. The WTRU may decode the DCI and determine a transmission time interval (TTI) duration, which may be expressed as an integer number of basis time intervals (BTIs). The WTRU may determine a downlink (DL) transmission portion and assignment and an uplink (UL) transmission portion and UL grant based on the received DCI. Additionally, the WTRU may determine the downlink (DL) transmission portion and assignment and the uplink (UL) transmission portion and UL grant based on an offset (t offset ) determines the start of the UL portion. The WTRU may receive data in the DL portion of the frame and may transmit in the UL portion of the frame based on the determined UL grant and TTI duration.

Description

[0001] This application is a divisional application of Chinese patent application No. 201680048908.7, entitled “Framing, Scheduling and Synchronization in Wireless Systems”, filed on August 25, 2016, the contents of which are incorporated herein by reference.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims the benefit of U.S. Provisional Application Serial No. 62 / 209,665 filed on August 25, 2015, U.S. Provisional Application Serial No. 62 / 250,840 filed on November 4, 2015, U.S. Provisional Application Serial No. 62 / 254,916 filed on November 13, 2015, and U.S. Provisional Application Serial No. 62 / 273,245 filed on December 30, 2015, the contents of which are incorporated herein by reference. Background Art

[0004] Mobile communication technology continues to evolve and is on the verge of its fifth generation – 5G. As with previous generations, new use cases are largely setting the requirements for this new generation.

[0005] The 5G air interface is expected to enable these use cases as improved wideband performance (IBB), large bandwidth (e.g., 1 ms transmission time interval (TTI), ultra-low latency (e.g., approximately 125 μs), ultra-reliable transmission (e.g., single TTI versus multiple TTI scheduling)), low-power node transmission, such as device-to-device (D2D) and vehicular applications (V2X), industrial control and communications (ICC), and massive machine type communications (mMTC). Summary of the Invention

[0006] Various approaches for flexible and adaptable framing are disclosed. In some embodiments, the frame structure and timing for the variable frame structure are determined. Synchronization and frame timing for the flexible frame structure are acquired. Scheduling and link adaptation are performed. Scheduling and link adaptation can be based on two instances of downlink control information (DCI).

[0007] A WTRU may receive a DCI indicating the start of a frame. The DCI may be received on a control channel, such as a physical downlink control channel (PDCCH), from an eNB, a base station, an AP, or other infrastructure equipment operating in a wireless communication system. The WTRU may decode the DCI and may determine a transmission time interval (TTI) duration, which may be expressed as an integer number of basis time intervals (BTIs). The WTRU may determine a downlink (DL) transmission portion and assignment and an uplink (UL) transmission portion and UL grant based on the received DCI. Additionally, the WTRU may determine the downlink (DL) transmission portion and assignment and the uplink (UL) transmission portion and UL grant based on an offset (t offset) determines the start of the UL portion. The WTRU may receive data in the DL portion of the frame and may transmit in the UL portion of the frame based on the determined UL grant and TTI duration. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] A more detailed understanding may be obtained from the following description given by way of example with reference to the accompanying drawings, in which:

[0009] Figure 1A is a system diagram of an example communication system in which one or more disclosed embodiments may be implemented;

[0010] Figure 1B Yes, you can Figure 1A A system diagram of an example wireless transmit / receive unit (WTRU) for use within a communication system is shown in FIG.

[0011] Figure 1C Yes, you can Figure 1A A system diagram of an example radio access network and an example core network for use within a communication system shown in FIG.

[0012] Figure 2 is a diagram of some examples of supported system transmission bandwidths;

[0013] Figure 3 is a diagram of an example flexible spectrum allocation;

[0014] Figure 4 is a diagram of an example flexible frame structure for TDD that may be used in a wireless communication system, such as a 5gFLEX system;

[0015] Figure 5 is a diagram of an example frame structure for FDD that may be used in a wireless communication system such as a 5gFLEX system;

[0016] Figure 6A is a flow chart of an example process for dynamically determining the structure and timing of a variable frame;

[0017] Figure 6B is a flow chart of an example process for dynamically configuring the structure and timing of a variable frame;

[0018] Figure 7 is a flow chart of an example transmission process for flexible framing;

[0019] Figure 8 is a flow chart of an example process for determining frame timing and / or system frame number;

[0020] Figure 9 is a flow chart of an example transmission control and scheduling process; and

[0021] Figure 10is a flow chart of an example link adaptation and scheduling process. DETAILED DESCRIPTION

[0022] Figure 1A is a diagram of an example communication system 100 in which one or more embodiments may be implemented. Communication system 100 may be a multiple access system that provides content, such as voice, data, video, messaging, broadcast, etc., to multiple wireless users. Communication system 100 may enable multiple wireless users to access this content by sharing system resources, including wireless bandwidth. For example, communication system 100 may utilize one or more channel access methods, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), etc.

[0023] like Figure 1A As shown, the communication system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, a radio access network (RAN) 104, a core network 106, a public switched telephone network (PSTN) 108, the Internet 110, and other networks 112. However, it should be understood that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of the WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment. By way of example, the WTRUs 102a, 102b, 102c, 102d may be configured to transmit and / or receive wireless signals and may include user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a pager, a cellular phone, a personal digital assistant (PDA), a smartphone, a laptop, a netbook, a personal computer, a wireless sensor, a consumer electronic product, and the like.

[0024] The communication system 100 may also include a base station 114a and a base station 114b. Each of the base stations 114a, 114b may be any type of device configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks, such as the core network 106, the Internet 110, and / or the networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a Node B, an eNode B (eNB), a Home Node B, a Home eNode B, a site controller, an access point (AP), a wireless router, and the like. While each of the base stations 114a, 114b is depicted as a single element, it will be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0025] The base station 114a may be part of the RAN 104, which may also include other base stations and / or network elements (not shown), such as a base station controller (BSC), a radio network controller (RNC), relay nodes, etc. The base station 114a and / or the base station 114b may be configured to transmit and / or receive wireless signals within a particular geographic area, which may be referred to as a cell (not shown). A cell may be further divided into cell sectors. For example, the cell associated with the base station 114a may be divided into three sectors. Thus, in one embodiment, the base station 114a may include three transceivers, one for each sector of the cell. In another embodiment, the base station 114a may employ multiple-input multiple-output (MIMO) technology and, therefore, may use multiple transceivers for each sector of the cell.

[0026] The base stations 114a, 114b may communicate with one or more of the WTRUs 102a, 102b, 102c, 102d over 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).

[0027] More specifically, as described above, the communication system 100 may be a multiple-access system and may employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. For example, the base station 114a in the RAN 104 and the WTRUs 102a, 102b, 102c may employ a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may employ Wideband CDMA (WCDMA) to establish the air interface 116. 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).

[0028] In another embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may utilize a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may utilize Long Term Evolution (LTE) and / or LTE-Advanced (LTE-A) to establish the air interface 116.

[0029] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile communications (GSM), Enhanced Data Rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and the like.

[0030] Figure 1A The base station 114b in may be a wireless router, a Home NodeB, a Home eNodeB, or an access point, for example, and may utilize any appropriate RAT to facilitate wireless connectivity in a local area, such as a business, a residence, a vehicle, a campus, and the like. In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In another embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a radio technology such as IEEE 802.15 to establish a wireless personal area network (WPAN). In another embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, etc.) to establish a picocell or femtocell. Figure 1A As shown, the base station 114b may have a direct connection to the Internet 110. Thus, the base station 114b may not be required to access the Internet 110 via the core network 106.

[0031] The RAN 104 may be in communication with the 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 the WTRUs 102a, 102b, 102c, 102d. For example, the core network 106 may provide call control, billing services, mobile location-based services, pre-paid calling, Internet connectivity, video distribution, and / or perform high-level security functions, such as user authentication. Figure 1A Although not shown, it will be appreciated that the RAN 104 and / or the core network 106 may be in direct or indirect communication with other RANs that employ the same RAT as the RAN 104 or a different RAT. For example, in addition to being connected to the RAN 104, which may utilize E-UTRA radio technology, the core network 106 may also be in communication with another RAN (not shown) employing a GSM radio technology.

[0032] The core network 106 may also serve as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or other networks 112. The PSTN 108 may include a circuit-switched telephone network that provides plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices that use common communication protocols, such as TCP, User Datagram Protocol (UDP), and IP from the Transmission Control Protocol (TCP) / Internet Protocol (IP) suite. The networks 112 may include wired or wireless communication networks owned and / or operated by other service providers. For example, the networks 112 may include another core network connected to one or more RANs, which may employ the same RAT as the RAN 104 or a different RAT.

[0033] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communication system 100 may include multi-mode capabilities, i.e., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks over different wireless links. Figure 1A The WTRU 102c shown in FIG. 1 may be configured to communicate with the base station 114a, which may employ a cellular-based radio technology, and with the base station 114b, which may employ an IEEE 802 radio technology.

[0034] Figure 1B is a system diagram of an example WTRU 102. Figure 1B As shown, 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, non-removable memory 130, removable memory 132, a power supply 134, a global positioning system (GPS) chipset 136, and other peripherals 138. It will be appreciated that the WTRU 102 may include any subcombination of the foregoing elements while remaining consistent with an embodiment.

[0035] The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of 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, and the like. The processor 118 may perform signal coding, data processing, power control, input / output processing, and / or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit / receive element 122. Although Figure 1B The processor 118 and the transceiver 120 are described as separate components, but it should be understood that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0036] The transmit / receive element 122 may be configured to transmit signals to a base station (e.g., base station 114a) or receive signals from a base station (e.g., base station 114a) over 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, UV, or visible light signals. In another embodiment, the transmit / receive element 122 may be configured to transmit and receive both RF and light signals. It will be appreciated that the transmit / receive element 122 may be configured to transmit and / or receive any combination of wireless signals.

[0037] Furthermore, although the transmit / receive element 122 is Figure 1B Although depicted as a single element in the embodiment, the WTRU 102 may include any number of transmit / receive elements 122. More specifically, the WTRU 102 may employ, for example, MIMO technology. Thus, in one embodiment, the WTRU 102 may include two or more transmit / receive elements 122 (e.g., multiple antennas) for transmitting and receiving wireless signals over the air interface 116.

[0038] The transceiver 120 may be configured to modulate signals to be transmitted by the transmit / receive element 122 and / or demodulate signals received by the transmit / receive element 122. As mentioned above, the WTRU 102 may have multi-mode capabilities. Thus, the transceiver 120 may include multiple transceivers that enable the WTRU 102 to communicate via multiple RATs, such as UTRA and IEEE 802.11.

[0039] The processor 118 of the WTRU 102 may be coupled to, and may receive user input data from, the speaker / microphone 124, the keyboard 126, and / or the display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or an organic light emitting diode (OLED) display unit). The processor 118 may also output user data to the speaker / microphone 124, the keyboard 126, and / or the display / touchpad 128. Furthermore, the processor 118 may access information from, and store data in, any suitable type of memory, such as non-removable memory 130 and / or removable memory 132. The non-removable memory 130 may include random access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory device. The removable memory 132 may include a subscriber identity 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, and store data in, memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).

[0040] The processor 118 may receive power from the power source 134 and may be configured to distribute and / or control the power to the other components in the WTRU 102. The power source 134 may be any suitable device for powering the WTRU 102. For example, the power source 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.), solar cells, fuel cells, etc.

[0041] The processor 118 may also be coupled to the GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU 102. In addition, or in lieu of the information from the GPS chipset 136, the WTRU 102 may receive location information from a base station (e.g., base stations 114a, 114b) over the air interface 116 and / or determine its location based on the timing of signals received from two or more neighboring base stations. It will be appreciated that the WTRU 102 may obtain location information by any suitable location-determination method while remaining consistent with an embodiment.

[0042] 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, functionality, and / or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an electronic compass, a satellite transceiver, a digital camera (for photos or videos), a Universal Serial Bus (USB) port, a vibration device, a television transceiver, a hands-free headset, a Bluetooth modules, FM radio units, digital music players, media players, video game console modules, Internet browsers, and more.

[0043] Figure 1C 1 is a system diagram of the RAN 104 and the core network 106 according to an embodiment. As mentioned above, the RAN 104 may employ an E-UTRA radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also be in communication with the core network 106.

[0044] The RAN 104 may include eNode-Bs (eNBs) 140a, 140b, and 140c, though it will be appreciated that the RAN 104 may include any number of eNode-Bs while remaining consistent with various embodiments. Each of the eNode-Bs 140a, 140b, and 140c may include one or more transceivers for communicating with the WTRUs 102a, 102b, and 102c over the air interface 116. In one embodiment, the eNode-Bs 140a, 140b, and 140c may implement MIMO technology. Thus, the eNode-B 140a, for example, may use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a.

[0045] Each of the eNodeBs 140a, 140b, 140c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, user scheduling in the uplink and / or downlink, and the like. Figure 1C As shown, the eNode-Bs 140a, 140b, 140c may communicate with one another via an X2 interface.

[0046] Figure 1C The core network 106 shown in FIG may include a mobility management entity gateway (MME) 142, a serving gateway 144, and / or a packet data network (PDN) gateway 146. While each of the aforementioned elements is depicted as part of the core network 106, it should be understood that any of these elements may be owned and / or operated by an entity other than the core network operator.

[0047] The MME 142 may be connected to each of the eNode-Bs 140a, 140b, 140c in the RAN 104 via an S1 interface and may serve as a control node. For example, the MME 142 may be responsible for user authentication of the WTRUs 102a, 102b, 102c, bearer activation / deactivation, selecting a particular serving gateway during an initial attach of the WTRUs 102a, 102b, 102c, and the like. The MME 142 may also provide a control plane function for switching between the RAN 104 and other RANs (not shown) employing other radio technologies, such as GSM or WCDMA.

[0048] The serving gateway 144 may be connected to each of the eNode-Bs 140a, 140b, 140c in the RAN 104 via an S1 interface. The serving gateway 144 may generally route and forward user data packets to and from the WTRUs 102a, 102b, 102c. The serving gateway 144 may also perform other functions, such as anchoring the user plane during inter-eNB handovers, triggering paging when downlink data is available for the WTRUs 102a, 102b, 102c, managing and storing the context of the WTRUs 102a, 102b, 102c, and the like.

[0049] The serving gateway 144 may also be connected to the PDN gateway 146, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0050] The core network 106 may facilitate communications with other networks. For example, the core network 106 may provide the WTRUs 102a, 102b, 102c with access to circuit-switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional land-line communications devices. For example, the core network 106 may include, or communicate with, an IP gateway, such as an IP Multimedia Subsystem (IMS) server, which serves as an interface between the core network 106 and the PSTN 108. In addition, the core network 106 may provide the WTRUs 102a, 102b, 102c with access to the networks 112, which may include other wired or wireless networks owned and / or operated by other service providers.

[0051] Other networks 112 may also be connected to an IEEE 802.11-based wireless local area network (WLAN) 160. WLAN 160 may include an access router 165. The access router may include gateway functionality. Access router 165 may communicate with multiple access points (APs) 170a, 170b. Communication between access router 165 and APs 170a, 170b may be via wired Ethernet (IEEE 802.3 standard) or any other type of wireless communication protocol. AP 170a wirelessly communicates with WTRU 102d over the air interface.

[0052] This article uses the following abbreviations and acronyms:

[0053] Δf subcarrier spacing

[0054] 5gFlex 5G Flexible Radio Access Technology

[0055] 5gNB 5GFlex Node B

[0056] ACK

[0057] BLER Block Error Rate

[0058] BTI Basic TI (an integer multiple of one or more symbol durations)

[0059] CB connection-based (e.g., access, channels, resources)

[0060] CoMP Coordinated Multipoint Transmission / Reception

[0061] CP Cyclic Prefix

[0062] CP-OFDM Conventional OFDM (depends on cyclic prefix)

[0063] CQI Channel Quality Indicator

[0064] CN Core Network (e.g. LTE Packet Core)

[0065] CRC Cyclic Redundancy Check

[0066] CSI Channel State Information

[0067] D2D device-to-device transmission (e.g. LTE sidelink)

[0068] DCI Downlink Control Information

[0069] DL Downlink

[0070] DM-RS Demodulation Reference Signal

[0071] DRB Data Radio Bearer

[0072] EPC Evolved Packet Core

[0073] FBMC Filter Band Multi-Carrier

[0074] FBMC / OQAM FBMC technology using offset quadrature amplitude modulation

[0075] FDD Frequency Division Duplex

[0076] FDM Frequency Division Multiplexing

[0077] ICC Industrial Control and Communications

[0078] ICIC inter-cell interference cancellation

[0079] IP Internet Protocol

[0080] LAA License Assisted Access

[0081] LBT Listen Before Talk

[0082] LCH Logical Channel

[0083] LCP Logical Channel Prioritization

[0084] LTE Long Term Evolution, such as 3GPP LTE R8 and above

[0085] MAC Media Access Control

[0086] NACK Negative ACK

[0087] MC Multi-Carrier

[0088] MCS modulation and coding scheme

[0089] MIMO Multiple Input Multiple Output

[0090] MTC Machine Type Communication

[0091] NAS Non-Access Stratum

[0092] OFDM Orthogonal Frequency Division Multiplexing

[0093] OOB Out of Band (Emit)

[0094] Pcmax Total available UE power in a given TI

[0095] PHY Physical Layer

[0096] PRACH Physical Random Access Channel

[0097] PDU Protocol Data Unit

[0098] PER Packet Error Rate

[0099] PLR Packet Loss Rate

[0100] QoS Quality of Service (from the physical layer perspective)

[0101] RAB Radio Access Bearer

[0102] RACH Random Access Channel (or procedure)

[0103] RF Radio Front End

[0104] RNTI Radio Network Identifier

[0105] RRC Radio Resource Control

[0106] RRM Radio Resource Management

[0107] RS reference signal

[0108] RTT Round Trip Time

[0109] SCMA Single Carrier Multiple Access

[0110] SDU Service Data Unit

[0111] SOM Spectrum Operation Mode

[0112] SS synchronization signal

[0113] SRB Signalling Radio Bearer

[0114] SWG Switching Gap (in self-contained subframe)

[0115] TB transfer block

[0116] TDD Time Division Duplex

[0117] TDM Time Division Multiplexing

[0118] TI time interval (one or more integer multiples of BTI)

[0119] TTI Transmission Time Interval (one or more integer multiples of TI)

[0120] TRx transceiver

[0121] UFMC Universal Filtered Multi-Carrier

[0122] UF-OFDM Universal Filtered OFDM

[0123] UL Uplink

[0124] V2V Vehicle-to-Vehicle Communication

[0125] V2X vehicle communications

[0126] WLAN Wireless Local Area Network and related technologies (IEEE 802.xx domain)

[0127] Mobile communications technology continues to evolve and has reached its fifth generation—5G. As with previous generations, new use cases are largely setting the requirements for this new generation. The 5G air interface enables use cases including, but not limited to, improved broadband performance (IBB), industrial control and communications (ICC), vehicular applications (V2X), and massive machine-type communications (mMTC). These use cases can result in several requirements for the 5G interface, including, but not limited to, baseband filtering to support frequency-domain waveforms, ultra-low transmission latency, ultra-reliable transmission, and MTC operation (including narrowband operation).

[0128] Support for baseband filtering of frequency-domain waveforms may involve several design considerations. For example, such design considerations may include the ability to achieve efficient spectrum aggregation (e.g., up to 150 to 200 MHz of total spectrum within a given RF transceiver path) without relying on a redesign of the front end.

[0129] Spectrum aggregation between widely separated operating bands (e.g., 900 MHz and 3.5 GHz) can be based on the use of multiple RF transceiver chains due to antenna size requirements and amplifier optimization design constraints. For example, a WTRU implementation may include three separate RF transceiver paths: a first RF transceiver path below 1 GHz, a second RF transceiver path for the 1.8 to 3.5 GHz frequency range, and a third RF transceiver path covering the 4 to 6 GHz frequency range. Native built-in support for large MIMO antenna configurations may also be a second-level requirement.

[0130] Various use cases (e.g., IBB) may require efficient aggregation of multiple bands of spectrum of varying sizes to achieve data rates on the order of, for example, tens of Mbps (cell edge) up to peak data rates of several Gbps (e.g., up to 8 Gbps) (typical data rates are on the order of hundreds of Mbps).

[0131] Support for ultra-low transmission latency may also involve some design considerations. For example, air interface latency as low as 1 ms RTT may require support for TTIs between 100 μs and 250 μs (no larger).

[0132] Support for ultra-low access latency (e.g., the time from initial system access until the first user plane data unit transmission is complete) may also be of interest. For example, IC and V2X may require specific end-to-end (e2e) latency. Such e2e latency may be less than 10ms.

[0133] Support for ultra-reliable transmission can also involve some design considerations. One such design consideration can include transmission reliability that is significantly better than what is currently possible using legacy LTE systems. For example, a target transmission reliability rate can be 99.999% transmission success and service availability. Another consideration can be support for mobility in the speed range of 0 to 500 km / h. For example, IC and V2X can require a specific packet loss rate. Such a packet loss ratio can be below 10e -6 .

[0134] Support for MTC operations (including narrowband operations) may involve several design considerations. For example, the air interface may be required to efficiently support narrowband operations (e.g., operations using bandwidths less than 200 kHz), may require extended battery life (e.g., up to 15 years of autonomy), and may require minimal communication overhead for small and infrequent data transmissions (e.g., low data rates in the range of 1 to 100 kbps with access latency of seconds to hours).

[0135] Support for mMTC use cases may require narrowband operation. The resulting link budget may be required to be comparable to the LTE extended coverage budget while supporting a very large number of MTC devices (up to 200k / km). 2 ) without adversely affecting the spectrum efficiency of other supported services.

[0136] The example requirements above can in turn relate to the following design aspects:

[0137] The 5G system design can enable flexible spectrum usage, deployment strategies, and operations. The design can support operations using spectrum blocks of variable sizes or spectrum, including aggregation of non-adjacent carriers in the same and / or different bands, licensed or unlicensed. The system can also support narrowband and wideband operation, different duplexing methods (and for TDD, dynamically variable DL / UL allocations), variable TTI lengths, scheduled and unscheduled transmissions, synchronous and asynchronous transmissions, separation of the user plane and control plane, and multi-node connectivity.

[0138] The 5G system design may be integrated with multiple legacy (E-)UTRAN and EPC / CN aspects. While there may not be a requirement for backward compatibility, it may be desirable for the system to integrate and / or operate with legacy interfaces (or their evolution). For example, the system may be backward compatible towards at least legacy CN (e.g., S1 interface, NAS) and eNB (e.g., X2 interface including dual connectivity with LTE), as well as implement legacy aspects such as support for existing QoS and security mechanisms. In addition, other functionality supported by legacy systems may be considered. For example, D2D / sidelink operation, LAA operation using LBT, and relaying may be supported.

[0139] Several fundamental concepts may underpin the flexible radio access system for 5G (5gFLEX). OFDM is used as the base signal format for data transmission in LTE and IEEE 802.11. OFDM effectively divides the spectrum into multiple parallel orthogonal subbands. Each subcarrier may be shaped using a rectangular window in the time domain, resulting in a sinusoidal subcarrier in the frequency domain. OFDMA may therefore require perfect frequency synchronization and tight management of uplink (UL) timing alignment over the duration of the cyclic prefix to maintain orthogonality between signals and minimize inter-carrier interference. Such synchronization may also not be well suited for systems where the WTRU is simultaneously connected to multiple access points. Additional power reduction is also typically applied to uplink transmissions to comply with out-of-band (OOB) emissions or spectrum emission requirements (e.g., to adjacent bands), especially in cases where there is aggregation of segmented spectrum for transmissions by the WTRU.

[0140] Some of the shortcomings of conventional OFDM (CP-OFDM) can be addressed through stricter RF requirements for implementation, especially when operating with large amounts of contiguous spectrum that do not require aggregation. CP-based OFDM transmission schemes can also result in a downlink physical layer for 5G that is similar to the downlink physical layer of legacy systems (e.g., with modifications primarily to pilot signal density and location).

[0141] Therefore, 5gFLEX design can focus on other waveform candidates, but conventional OFDM is still a likely candidate for 5G systems, at least for downlink (DL) transmission schemes. Building on the foundational technologies already known from conventional OFDMA and legacy LTE systems, the various principles behind the design of flexible radio access for 5G are discussed further below.

[0142] The 5gFLEX downlink transmission scheme can be based on a multi-carrier waveform, which can be characterized by high spectral capacity (i.e., lower sidelobes and lower OOB emissions). In particular, possible MC waveform candidates for 5G include OFDM-OQAM and UFMC (UF-OFDM). Multi-carrier modulation waveforms can divide a channel into subchannels and modulate data symbols on subcarriers in these subchannels.

[0143] Using OFDM-OQAM, a filter can be applied to the OFDM signal in the time domain for each subcarrier to reduce OOB. OFDM-OQAM can result in very low interference to adjacent bands, may not require a large guard band, and may not require a cyclic prefix. OFDM-OQAM may be the most popular FBMC technique. However, OFDM-OQAM can be sensitive to multipath effects and high-delay propagation in terms of orthogonality, thus complicating equalization and channel estimation.

[0144] With UFMC (UF-OFDM), filters can also be applied to the OFDM signal in the time domain to reduce OOB. However, filtering can be applied per subband to utilize spectrum segmentation, potentially reducing complexity and making UF-OFDM somewhat more practical for implementation. However, if there are one or more unused spectrum segments in the band, OOB emissions in these segments may still remain as high as in conventional OFDM. In other words, UF-OFDM performs better than OFDM only at the edges of the filtered spectrum, not in the holes of the spectrum.

[0145] The method described herein is not limited to the above waveforms and can be applied to other waveforms.The above waveforms will be further used herein for illustrative purposes.

[0146] Such waveforms can enable frequency reuse of signals with non-orthogonal characteristics (e.g., different subcarrier spacings) and coexistence of asynchronous signals without the need for complex interference cancellation receivers. Such waveforms can also facilitate aggregation of segmented portions of the spectrum in baseband processing as a lower-cost alternative to implementing such aggregation as part of RF processing.

[0147] Coexistence of different waveforms within the same frequency band can be used, for example, to support mMTC narrowband operation (e.g., using SCMA). Another example may include supporting a combination of different waveforms within the same frequency band (e.g., CP-OFDM, OFDM-OQAM, and UF-OFDM, for all aspects and for downlink and uplink transmissions).

[0148] The 5gFLEX uplink transmission scheme may use the same or different waveforms for downlink transmissions. Multiplexing of transmissions to and from different WTRUs in the same cell may be based on FDMA and TDMA.

[0149] The methods, devices, and systems described herein may be particularly applicable to the evolution of 5G systems and other existing systems (e.g., LTE systems), or the evolution of other wireless technologies (e.g., HSPA, WiFi / IEEE 802.11, etc.). For example, some of the proposed methods, devices, and systems may be backward compatible with existing technologies. For example, TTIs shorter than LTE time slots (0.5ms) may be supported using different waveforms to achieve ultra-low latency. Operating the 5G physical layer (DL and / or DL) in TDM and / or FDM using LTE may also be supported.

[0150] The 5gFLEX radio access design can be characterized by a very high degree of spectrum flexibility, which enables deployment in different frequency bands with different characteristics, including different duplex arrangements and different and / or variable sizes of available spectrum, including contiguous and non-contiguous spectrum allocations in the same or different frequency bands. The 5gFLEX radio access design can also support variable timing aspects, including support for multiple TTI lengths and support for asynchronous transmissions.

[0151] 5gFLEX supports both TDD and FDD duplexing schemes. For FDD operation, spectrum aggregation can be used to support supplementary downlink operation. FDD operation can support both full-duplex FDD and half-duplex FDD operation. For TDD operation, DL / UL allocations can be dynamic, meaning they are not based on a fixed DL / UL frame configuration; instead, the length of the DL or UL transmission interval can be set for each transmission opportunity.

[0152] The 5gFLEX design allows for different transmission bandwidths on the uplink and downlink, ranging from the nominal system bandwidth up to any bandwidth corresponding to the maximum value of the system bandwidth.

[0153] Figure 2 is a diagram that provides some examples of system transmission bandwidths supported by an example 5gFLEX system 200. For single carrier operation, the supported system bandwidths may include at least 5, 10, 20, 40, and 80 MHz. In some embodiments, the supported system bandwidths may include any bandwidth in a given range (e.g., from a few MHz up to 160 MHz). The nominal bandwidth may have one or more fixed possible values. Support for 160 MHz and for a nominal system bandwidth (e.g., 5 MHz) may also be possible. Narrowband transmissions up to 200 KHz may be supported within the operating bandwidth for MTC devices. Note that the system bandwidth 201 used herein may refer to the maximum portion of the spectrum that can be managed by the network for a given carrier. For such a carrier, the portion of the spectrum that the WTRU minimum supports for cell acquisition, measurement, and initial access to the network may be referred to here as the nominal system bandwidth 202. The WTRU may be configured with channel bandwidths 203, 204, and 205, which are within the range of the overall system bandwidth. The WTRU's configured channel bandwidths 203, 204, and 205 may or may not include a nominal system bandwidth 202 portion of the system bandwidth 201. Bandwidth flexibility may be achieved because all applicable sets of RF requirements for a given maximum operating bandwidth in a band may be met without introducing additional allowed channel bandwidths for that operating band due to efficient support of baseband filtering of frequency domain waveforms.

[0154] The channel bandwidth of a WTRU for single carrier operation may be configured, reconfigured, and / or dynamically changed, and spectrum may be allocated for narrowband transmission within the nominal system, system, or configured channel bandwidth.

[0155] The 5gFLEX physical layer can be band-agnostic and can support operation in licensed bands (e.g., below 5 GHz) as well as operation in unlicensed bands (e.g., in the range 5 to 6 GHz). For operation in these unlicensed bands, LBT Cat 4-based channel access frames similar to LTE LAA can be supported.

[0156] Cell-specific and / or WTRU-specific channel bandwidths for arbitrary spectrum block sizes may also be scaled and managed (eg, scheduling, resource addressing, broadcast signals, measurements).

[0157] 5gFLEX may support flexible spectrum allocation as described herein. Downlink control channels and signals may support FDM operation. A WTRU may acquire a downlink carrier by receiving transmissions using only a nominal portion of the system bandwidth. In other words, a WTRU may not initially need to receive transmissions covering the entire bandwidth managed by the network for a particular carrier.

[0158] The downlink data channel may be allocated on a bandwidth that may or may not correspond to the nominal system bandwidth, with no restrictions other than being within the WTRU's configured channel bandwidth. For example, the network may operate a carrier at a 12 MHz system bandwidth using a 5 MHz nominal bandwidth, allowing devices supporting up to 5 MHz maximum RF bandwidth to acquire and access the system while allocating +10 to -10 MHz of the carrier frequency to other WTRUs supporting up to 20 MHz worth of channel bandwidth.

[0159] Figure 3 is a diagram of an example flexible spectrum allocation 300. A system bandwidth 301 may support a spectrum allocation with variable transmission characteristics 302 and a nominal system bandwidth 303. Figure 3 In the example of , different subcarriers 304 may be assigned, at least conceptually, to different operating modes (e.g., spectrum operating modes (SOMs)). Different SOMs may be used to meet different requirements for different transmissions. The SOM may include subcarrier spacing, TTI length, and / or one or more reliability aspects (e.g., hybrid automatic repeat request (HARQ) processing aspects) and possibly auxiliary control channels. The SOM may refer to specific waveform or processing aspects (e.g., support for coexistence of different waveforms in the same carrier using FDM and / or TDM, or support for coexistence of FDD operation in a TDD band using TDM or other means).

[0160] The WTRU may be configured to perform transmissions according to one or more SOMs. For example, the SOM may correspond to transmissions using at least one of a specific TTI duration, a specific initial power level, a specific HARQ process type, a specific upper bound for successful HARQ reception / transmission, a specific transmission mode, a specific physical channel (uplink or downlink), a specific waveform type, or transmissions according to a specific RAT (e.g., legacy LTE or according to a 5G transmission method). The SOM may correspond to a QoS level and / or related aspects such as maximum / target latency, maximum / target BLER, or the like. The SOM may correspond to a spectrum region and / or a specific control channel or aspects thereof (including search space, DCI type, etc.).

[0161] Spectrum aggregation may be supported for single carrier operation. In spectrum aggregation, the WTRU may support transmission and reception of multiple transport blocks on a contiguous or non-contiguous set of physical resource blocks (PRBs) within the same operating band. A single transport block may also be mapped to a separate set of PRBs.

[0162] Simultaneous transmissions may be associated with different SOM requirements. Multi-carrier operation may also be supported using contiguous or non-contiguous spectrum blocks within the same operating band or across two or more operating bands. Aggregation of spectrum blocks using different modes (e.g., FDD and TDD) and using different channel access methods (e.g., licensed and unlicensed band operation below 6 GHz) may also be supported. The WTRU's multi-carrier aggregation may be configured, reconfigured, or dynamically changed.

[0163] Efficient baseband filtering in the frequency domain may have the advantage of allowing highly flexible spectrum aggregation and support for additional channel or band combinations without requiring RF regulation work.

[0164] Scheduling functionality may be supported in the MAC layer. Scheduling modes may include, but are not limited to, network-based scheduling with tight scheduling of resources, timing, and transmission parameters for downlink and / or uplink transmissions, and WTRU-based scheduling with greater flexibility in timing and transmission parameters. For both modes, scheduling information may be valid for a single or multiple TTIs.

[0165] Network-based scheduling may enable the network to closely manage the available radio resources assigned to different WTRUs, for example, to optimize the sharing of these resources.Such network-based scheduling may be dynamic.

[0166] WTRU-based scheduling allows the WTRU to opportunistically access uplink resources as needed with minimal latency within a set of shared or dedicated uplink resources assigned (dynamically or not) by the network. Both synchronous and asynchronous opportunistic transmissions can be supported, as well as contention-based and contention-free transmissions.

[0167] Support for opportunistic transmissions (scheduled or unscheduled) may have the advantage of meeting the ultra-low latency requirements of 5G and the energy-saving requirements of mMTC use cases.

[0168] Flexible framing may be used in wireless communication systems, such as 5gFLEX systems, for downlink and uplink transmissions. Downlink and uplink transmissions may be organized into radio frames characterized by a number of fixed aspects (e.g., location of downlink control information) and a number of varying aspects (e.g., transmission timing, supported transmission types). One or more of these aspects may differ in the radio frame arrangement between different types of transmissions, between transmissions of the same WTRU (e.g., spectrum operating mode (SOM) specific framing structures), between transmissions of different WTRUs (e.g., WTRU specific framing structures), and between transmissions in the downlink direction and the uplink direction. The timing relationships supported by the flexible frame structure may be indicated to the WTRU dynamically or semi-statically, as shown in the examples described herein.

[0169] The transmission time interval (TTI) may be the minimum time supported by the system between consecutive transmissions, where each transmission may be the same as the downlink (TTI) DL ) and is associated with different transport blocks (TBs) for the uplink (UL TRx), excluding any preamble (if applicable), but including any control information (such as downlink control information (DCI) or uplink control information (UCI)). A TTI can be represented as an integer number of one or more basic time intervals (BTIs).

[0170] The BTI may be expressed as an integer number of one or more symbols, where the symbol duration may be a function of the subcarrier spacing applicable to the time-frequency resource. For FDD, the subcarrier spacing may thus be 1 for a given frame on the uplink carrier frequency f UL With the downlink carrier frequency f DL BTI can also be represented as a legacy timing structure, such as the legacy TTI.

[0171] Supported frame durations may include at least, for example, 100 μs, 125 μs (1 / 8 ms), 142.85 μs (1 / 7 ms is 2 LTE OFDM symbols with a normal cyclic prefix), and 1 ms to achieve alignment with the legacy LTE timing structure.

[0172] Figure 4 is a diagram of an example flexible frame structure 400 that may be used for TDD in a wireless communication system such as a 5gFLEX system according to one embodiment, which may be used in any combination with the embodiments described herein. Figure 4As shown in the example, the start of each frame can be determined by a fixed time duration t dci The downlink control information (DCI) 401a and 401b of 412a and 412b indicate that the fixed time duration is for the carrier frequency f in question. UL+DL Before any DL transmission portion of each frame (DLTRx) 402a and 402b. The duration of the DL transmission portion 402a and 402b may be based on an integer number of transport blocks (TBs).

[0173] exist Figure 4 In the example of FIG, in addition to any downlink assignments and / or any uplink grants indicated by DCIs 401a and 401b, DCI 401a may also indicate for the DL TRx portion 402a of frame n at least a duration of t DL(n) 405a, and the DCI 401b may indicate at least duration t for the DL TRx portion 402b of frame n+1. DL(n+1) 405b.

[0174] The frame may also include an UL transmission portion of the frame (UL TRx) 403a and 403b. The duration of the UL transmission portion 403a and 403b may be based on an integer number of transport blocks (TBs). Figure 4 In the example of FIG. 4 , the DCI 401a may indicate at least a duration t for the UL TRx portion 403a of frame n. UL(n) 406a, and the DCI 401b may indicate at least duration t for the UL TRx portion 403b of frame n+1. UL(n+1) 406b. If the uplink portion of the frame exists, such as Figure 4 As shown in the example of , switching gaps (SWGs) 404a and 404b may precede the uplink portion of each frame.

[0175] The WTRU may then derive the final TTI duration for each frame based on the DCI 401a and 401b. Figure 4 As shown in the example of , the variable duration of each frame can be expressed as a TTI duration, which is expressed as an integer number of BTIs. Figure 4 In the example, the duration of frame n is denoted as TTI n , which is denoted as x*BTI 409a, and the duration of frame n+1 is denoted as TTI n+1 , which is represented as y*BTI 409b. Figure 4 The example also shows an inter-subframe space (ISS) 411.

[0176] For TDD, 5gFLEX may support sidelink operation for device-to-device (D2D) or vehicle-to-external (V2X) communication purposes in the frame structure 400 by including respective downlink control and forward transmissions in the DCI and DL TRx portions (if semi-static allocation of respective resources is used). Alternatively, sidelink operation for D2D or V2X communication purposes may be supported in the frame structure 400 by including respective downlink control and forward transmissions only in the DL TRx portion (for dynamic allocation). Respective reverse transmissions for sidelink operation for D2D or V2X communication purposes may be included in the UL TRx portion of the frame structure 400.

[0177] Note that DL and / or t UL The indication or configuration may correspond to a setting in which there is no DL TRx and / or UL TRx portion. This may be useful in cases where only DL or only UL transmission is scheduled.

[0178] Figure 5 FIG2 is a diagram of an example frame structure 500 for FDD that may be used in a wireless communication system such as a 5gFLEX system according to another embodiment, which may be used in combination with any of the embodiments described herein. The frame structure 500 may include a downlink reference TTI and one or more TTIs for the uplink. Figure 5 As shown in the example, the start of a frame can be determined by a fixed time duration t dci 506a and 506b (which are for the carrier frequency f in question) DL The DCI 501a and 501b preceding any downlink data transmission portion (DL TRx) 502a and 502b indicates that the duration of the DL transmission portion 502a and 502b may be based on an integer number of transport blocks (TBs).

[0179] exist Figure 5 In the example of FIG, DCI 501a may indicate the TTI duration t for the DL TRx portion 502a of frame n. DL(n) 507a, and the DCI 501b may indicate the TTI duration t for the DL TRx portion 502b of frame n+1. DL(n+1) 507b. Figure 5 As shown in the example of , the variable duration of each frame can be expressed as a downlink reference TTI duration, which can be expressed as an integer number of BTIs. Figure 5 In the example, the duration of frame n can be expressed as TTI DL(n) , which may be denoted as x*BTI 509a, and the duration of frame n+1 as TTI DL(n+1), which can be expressed as y*BTI509b.

[0180] The DCI may indicate the offset (t offset )505 and TTI duration. Separate DCI can also be used for downlink and uplink directions. Figure 5 In the example of UL The duration of the UL transmission parts 503a, 503b and 503c may be based on an integer number of transport blocks (TBs). An offset (t offset )505 derives the start of the uplink TTI. offset 505 may include timing advance, for example where UL synchronization is applicable. Figure 5 In the example of FIG, DCI 501a may indicate at least duration t of UL TRx parts 503a and 503b for frame n. UL(n,0) 508a and t UL(n,1) 508b. The DCI 501b may indicate at least the duration t of the UL TRx portion 503c for frame n+1. UL(n+1,0) 508c. Figure 5 The example also shows ISS 504.

[0181] For FDD, 5gFLEX may support sidelink operation for the purpose of D2D or V2X communication in the UL TRx portion of the frame structure 500 by including respective downlink control and forward and reverse transmissions in the UL TRx portion (which may use dynamic allocation of respective resources).

[0182] DL timing / resources of the HARQ A / N using the frame structure 400 or 500 may also be determined for uplink transmissions. The timing between the data transmission and the corresponding HARQ A / N may be indicated explicitly or implicitly.

[0183] Note that the ISS can support asynchronous operation (e.g., for License Assisted Access (LAA), Massive Machine Type Communication (mMTC), and low latency) when determining the start of a frame by detecting the preamble. Note also that t offset Processing delays in the range of 0 μs up to one or more ms can be supported. offset CP-OFDM based transmissions can be supported by additionally including a timing advance (i.e., in these cases t offset ≥Timing Advance). The t offsetSynchronous DL / UL relations can also be supported (if set to a value equal to the sum of the required processing delay and the required timing advance (0 μs in the case where it is not required for the applicable waveform). This is the case for FDD operation, given that it does not need to support Listen Before Talk (LBT) operation. If Uplink Control Information (UCI) is present at the beginning of the UL TRx part or if scheduling of uplink control channels is supported, the t offset Can support UCI asynchronous scheduling.

[0184] Figure 6A is a flow chart of an example process for dynamically determining the structure and timing of the variable frame 600 as described above. Figure 6A 600 , each step of the process 600 is shown and described separately, but the steps may be performed in a different order than shown, in parallel with each other, or simultaneously with each other. The WTRU may receive a DCI 601 indicating the start of a frame via a transceiver or receiver of the WTRU as described above. The DCI may be received on a control channel such as a physical downlink control channel (PDCCH) from an eNB, a base station, an AP, or other infrastructure operating in a wireless communication system. The WTRU may decode 602 the DCI. The WTRU may determine a TTI duration 603 based on the received DCI. As described above, the TTI duration may be expressed as an integer number of BTIs. The WTRU may determine a DL transmission portion and a DL transmission assignment 604 based on the received DCI. The WTRU may then determine an UL transmission portion and an UL grant 605 based on the received DCI. Additionally, the WTRU may determine an offset (t offset ) determines the start of the UL portion. The WTRU, via the WTRU's transceiver or receiver as described above, may receive data in the DL transmission portion of the frame based on the determined DL transmission assignment and the TTI duration 606. The WTRU, via the WTRU's transceiver or transmitter as described above, may transmit data in the UL transmission portion of the frame based on the determined UL grant and the TTI duration 607.

[0185] Figure 6B is a flow chart of an example process for dynamically configuring the structure and timing of a variable frame as described above. Figure 6BEach step of the process in is shown and described separately, but the multiple steps may be performed in a different order than shown, in parallel with each other, or simultaneously with each other. The eNB (or base station, AP, or other infrastructure equipment operating in a wireless communication system) may transmit a DCI 611 to the WTRU via the transceiver or transmitter of the eNB as described above, indicating the start of a frame. The DCI may be transmitted on a control channel such as a PDCCH. The transmitted DCI may enable the WTRU to determine the TTI duration based on the DCI. The transmitted DCI may enable the WTRU to determine the DL transmission portion and the DL transmission assignment based on the DCI. The transmitted DCI may enable the WTRU to determine the UL transmission portion and the UL grant based on the DCI. In addition, the transmitted DCI may enable the WTRU to determine the TTI duration based on the offset (t offset ) determines the start of the UL portion. The eNB, via the eNB's transceiver or transmitter as described above, may transmit data 612 to the WTRU in the DL portion of the frame based on the DL transmission assignment and the TTI duration. The eNB, via the eNB's transceiver or receiver as described above, may receive data 613 in the UL portion of the frame based on the UL grant and the TTI duration.

[0186] Figure 7 is a flow chart of an example transmission process for flexible framing 700 that may be used in a wireless communication system such as 5gFLEX according to one embodiment, which may be used in any combination with the embodiments described herein. Figure 7 If uplink control information (DCI) is transmitted only in the UL TRx portion (e.g., if there is no UL transport block for a given WTRU), the WTRU may obtain or receive the UCI resources to be used in the UL TRx portion 701. The WTRU may use one or a combination of methods to obtain or receive the UCI resources to be used 701, including but not limited to the following:

[0187] (1) The allocated resources for the UCI to be used by the WTRU may be derived from the configured resource set. These allocated resources may be WTRU-specific or may be associated with multiple WTRUs.

[0188] (2) The UCI resources may be indicated to the WTRU using DCI.

[0189] (3) The UCI resources to be used by the WTRU to transmit UCI in the UL TRx portion may be determined by the WTRU based on the transmission parameters used for reception in the previous DL TRx portion. In a first example, the frequency location and / or allocated bandwidth and / or transmission duration and / or coding parameters of the data channel received by the WTRU in the DL TRx portion may be used by the WTRU to determine the transmission parameters of the corresponding UCI transmission in terms of frequency domain resources and coding parameters in the UL TRx portion. In a second example, the WTRU may determine the UCI resources to be used from the coding parameters of a known signal sequence (e.g., pilot symbols and / or pattern). One of the following parameters and / or a combination of two or more of the following parameters or other parameters may be used by the WTRU to generate such a known sequence to determine the UCI resources: one or more frequency locations, an index identifier generation sequence, a sequence number and a frame number, and symbol timing.

[0190] refer to Figure 7 The WTRU may then determine the frame start timing 702 (e.g., with respect to the start of the frame where the DCI may be decoded) using one or a combination of methods including, but not limited to, the following:

[0191] (1) The WTRU may determine the start of the frame transmission by measuring and determining the presence of a known signal sequence. The WTRU may search for a known signal sequence from a set of candidate signal sequences in frequency and / or time. In one embodiment, the known signal sequence may be or correspond to a set of fixed-value symbols distributed in a frequency / time allocation grid at the start of a frame. In another embodiment, the known signal sequence may be or correspond to a preamble signal. Upon detecting a known signal sequence, the WTRU may determine the presence of a DCI by deriving a position in frequency and / or time and a candidate occurrence position based on the detected known signal sequence.

[0192] (2) The WTRU may determine the start of a frame by determining the presence or absence of a frame in a finite set of candidate positions in time. In a first exemplary embodiment, a frame may start only at times ... 50, 100, 150, 200, ... microseconds (μs), but not in between. A WTRU that has determined the DL timing from the acquisition of a DL common signal / channel may therefore attempt to detect the possible start of a DL frame transmission only at these precisely known times. This approach may reduce detection complexity and / or increase detection reliability. In another embodiment, the candidate times at which a frame transmission may start are determined by the WTRU based on another DL signal transmission. For example, a WTRU that has acquired a DL reference signal may determine the possible start position of a frame transmission based on the transmission parameters of the DL reference signal.

[0193] Note that the timing parameters and start time of frame transmissions may be WTRU-specific, shared by a group of WTRUs, or common to all WTRUs. Furthermore, different DL signals / channels may use different configurations regarding transmission timing and possible start times. For example, a DL common control channel may use a start timing that is fixed and deterministic with respect to time. A DL data channel may use flexible start timing and occurrence depending on the data available for scheduling.

[0194] refer to Figure 7 , the WTRU may then determine when to transmit UL HARQ feedback 703 to support HARQ when using flexible framing transmission and reception. Note that HARQ feedback below may refer to a mapping of Ack, Nack, or DTX bits, or equivalent indices derived by the receiver after receiving a transport block, to individual or grouped bits or indices derived for one or more HARQ processes. The WTRU may determine when to transmit UL HARQ feedback 703 using one or a combination of methods, including but not limited to the following:

[0195] (1) The WTRU sends DL HARQ feedback for the TBs received in the DL TRx part immediately after the UL TRx part of the same frame.

[0196] (2) The WTRU may send DL HARQ feedback for TBs received in the DL TRx section in a configurable UL TRx section, where the configurable UL TRx section may be another frame. The WTRU may determine in which UL TRx section it transmits the DL HARQ feedback based on configured and / or signaled parameters. For example, the WTRU may determine that DL HARQ feedback for one or a group of DL HARQ processes is to be transmitted in the UL TRx section of every nth frame. Alternatively, the WTRU may determine that the DL HARQ feedback corresponding to the DL TRx in a frame is to be transmitted in the UL TRx section of the next frame. In another example, the DL HARQ feedback corresponding to multiple TBs received in multiple BTIs or TTIs may first be aggregated by the WTRU and then transmitted by the WTRU to the eNB in the UL TRx section of a determined frame. In such a case, the relationship between the DL TRx portion where the WTRU receives data and the DL TRx portion for which the DL HARQ feedback is derived, and the UL TRx portion where the aggregated multi-TTI HARQ feedback is transmitted to the eNB may be configured, may be given by a timing relationship, or may be determined from the receipt of a DL control signal or channel or its content.

[0197] (3) The UL HARQ feedback corresponding to the TB transmitted by the WTRU in the UL TRx portion of the frame may be transmitted by the eNB in the DL TRx portion of the next frame.

[0198] (4) The WTRU may determine which DL TRx portion and / or which frame may contain the UL HARQ feedback corresponding to the TBs transmitted by the WTRU in the UL TRx portion based on configured and / or signaled scheduling parameters, or the WTRU may determine that the UL HARQ feedback corresponding to the UL TRx in a frame is to be transmitted in the DL TRx portion of the frame. In another example, the UL HARQ feedback corresponding to multiple TBs received in multiple BTIs or TTIs may be first aggregated by the eNB and then transmitted to the WTRU by the eNB in the DL TRx portion of the determined frame. In such a case, the relationship between the UL TRx portion in which the eNB receives data and the UL TRx portion for which the UL HARQ feedback is derived, and the DL TRx portion in which the aggregated multi-TTI HARQ feedback is to be transmitted may be configured, given by a timing relationship, or signaled to the WTRU by transmission of a DL control signal or channel or its contents.

[0199] (5) The WTRU may determine, based on detection of a signal sequence and / or control signal, that a DL TRx portion may contain UL HARQ feedback corresponding to one or more previous UL TBs. For example, the signal sequence may indicate the presence of HARQ feedback carrying a signal / channel in the DL TRx portion of the frame, or the signal sequence may correspond to a DCI or equivalent control signal indicating the presence and / or identification of a recipient of HARQ feedback information. Note that the signal sequence or control signal announcing the presence of HARQ feedback may be different from the signal sequence or control signal carrying the HARQ feedback. Similarly, the presence, recipient, or process identification of HARQ feedback information may be decoded from one or a combination of such first and second signals.

[0200] (6) HARQ feedback corresponding to the DL TRx or UL TRx portion may be transmitted using a non-5gFLEX carrier. For example, DL HARQ feedback corresponding to a DL data channel received by a WTRU in the DL TRx portion may be transmitted to the eNB using an UL 3G HSPA or 4G LTE channel. The WTRU may first receive one or more TBs on the DL data channel using DL 5gFLEX. The WTRU may then determine the transmission timing and payload sequence for the 3G HSPA UL or 4G UL LTE control channel to transmit one or more DL HARQ feedback bits to the eNB using the 4G LTE UL. In one embodiment, the 4G LTE UL PUCCH may be used in a 1 millisecond (ms) TTI interval to carry N=10 A / N bits corresponding to N=10 received 5gFLEX DL data channels. This illustrative example can also be applied to 4G LTE UL PUSCH, carrying HARQ feedback for DL data received for DL 5gFLEX, or it can be used when the UL and DL directions are reversed, i.e., where the WTRU transmits UL 5gFLEX data in one or more frames in the UL TRx part and then receives HARQ feedback on the DL 3G HSPA or 4G LTE channel.

[0201] Various techniques may be used to determine the timing of different types of transmissions and / or the timing of certain periods in which no transmission occurs (i.e., transmission gaps). The expression "transmission type" may be used to refer to a transmission or transmission interval that may be characterized by any combination of the following: direction; purpose associated with the transmission gap; whether the transmission is used to carry control information or data; whether the control information includes a particular type of control; signal type; physical channel type; service, SOM, quality of service (QoS), or purpose associated with the transmission; whether the transmission corresponds to a scheduled or unscheduled transmission; a given resource allocation in the frequency domain, or a given carrier; or attributes associated with the transmission.

[0202] The direction may include downlink, uplink, sidelink transmission, or sidelink reception. The purpose associated with the transmission gap may include switching from DL to UL, inter-subframe spacing, measurement or radio resource management for CSI reporting, and clear channel assessment. Specific types of control information may include hybrid automatic repeat request (HARQ) feedback, channel state information (CSI), scheduling request (SR), frequency assignment, modulation and coding scheme (MCS), transport block size, precoding matrix information, etc. The information type may include reference signal type, such as sounding reference signal, demodulation reference signal, CSI reference signal, or cell-specific reference signal; synchronization signal; preamble, midamble, or postamble. The physical channel type may include a shared channel, a dedicated channel, or a control channel. The service, SOM, quality of service (QoS), or purpose associated with the transmission may include whether the transmission is associated with ultra-low latency communication, ultra-reliable communication, mobile broadband, device-to-device communication, vehicle-to-the-world communication, large machine-type communication, etc. Scheduled transmissions may be network controlled. Unscheduled transmissions may be WTRU-initiated. Attributes associated with a transmission may include modulation order, coding scheme, rank, subcarrier spacing, symbol duration, coding rate, and the like.

[0203] A given transmission type may occur in a single continuous time period, or in multiple (non-contiguous) time periods. The possible duration for certain transmission types (e.g., data transmissions) may be multiples of the BTI. Multiple transmissions of the same or different types may or may not be allowed to occur during the same time period, depending on the duplexing scheme and WTRU capabilities.

[0204] Flexible DCI to transmission timing may be supported by using a variable time offset (e.g., between DCI and transmission time) and / or multi-frame scheduling (e.g., DCI scheduling) in various embodiments. The WTRU may receive a DCI (e.g., DCI(t)) that is applicable at the beginning of a time period. The time period may be time period t, where t may be one of at least t=n, n+1, n+2, etc. Alternatively, t may represent a time offset (e.g., a number of symbols, a BTI, etc.). The DCI(t) may include a single value of t in the case of a single transmission time period (e.g., TTI) allocation (e.g., resource allocation) or multiple values in the case of an allocation that may be applicable for multiple transmission time periods (e.g., multiple TTIs). The multiple transmission time periods may be contiguous (e.g., one or more values for t may represent a range, including possibly a single value of t, with an indication of the total number of opportunities), or separated in time (e.g., one opportunity for each value of t). For example, the WTRU may receive a DCI that indicates multiple transmissions using multiple values of t, where each value may correspond to a transmission opportunity for a different HARQ process (multi-process scheduling), and / or using a single value of t with an indication of the total number of transmission opportunities for a single HARQ process (e.g., for bundling operations).

[0205] Transmissions can also be sequenced with variable timing. The timing of transmission types can be sequence-based, for example, based on the sequence of transmission types in a frame and the duration associated with each transmission type in the sequence. The start time of a given transmission type can then be determined as the sum of the durations of earlier transmission types in the sequence. The duration of a transmission type can be fixed or dynamically determined based on any of the methods described herein.

[0206] For example, a subsequent sequence of transmission types may be configured as follows: 1) downlink control information, 2) downlink data, 3) switching gap, 4) uplink data, and 5) uplink control information. In a particular frame, the duration of "downlink control information" transmission and "downlink data" transmission may correspond to 1 BTI and 5 BTI, respectively. In this case, the start time of "uplink data" transmission may be determined to be 6 BTIs after the start of the frame plus the duration of the switching gap.

[0207] The timing may vary based on the transmission type. The timing of a transmission type may be based on constraints, such as a function of conditions and / or priorities associated with the transmission type. Such conditions may include, but are not limited to, the following examples: a set of allowed BTIs for a given transmission type, a delay or minimum delay between a transmission and an associated transmission (possibly of a different type), a priority associated with a transmission type relative to other transmission types (in cases where other transmission types cannot occur simultaneously), or a maximum duration associated with each transmission type.

[0208] The set of allowed BTIs for a given transmission type may include, for example, that transmission of uplink control information may be allowed only starting from the nth BTI after the start of the frame.

[0209] An example of a delay or minimum delay between a transmission and an associated transmission (of a possibly different type) may include a case where the transmission of a HARQ-ACK associated with a downlink data transmission may be permitted only to occur at least 1 BTI after the end of the downlink data transmission plus a duration that may correspond to a timing advance and / or a switching gap. Alternatively, a delay or minimum delay between a transmission and an associated transmission may include a case where the transmission of an uplink data transmission may be permitted only to occur at least 1 BTI after a physical downlink control channel indicates the end of its parameters.

[0210] The priority associated with a transmission type relative to other transmission types in situations where other transmission types cannot occur simultaneously may itself be timing related. Such priorities may include, but are not limited to, the following examples: transmission of certain types of uplink control information (e.g., HARQ-ACK) may have a higher priority than other types (e.g., CSI); transmission of uplink control information may have a higher priority than transmission of uplink data or (in the case of TDD or FDD half-duplex operation) reception of downlink data; transmission of uplink data (or uplink control information) may be prioritized according to the associated SOM (e.g., transmission associated with an ultra-low latency SOM may have a higher priority than transmission associated with a mobile broadband SOM); and transmission of a HARQ-ACK associated with a first downlink data transmission may have a higher priority than transmission of a HARQ-ACK associated with a second downlink data transmission if the first downlink data transmission started (or completed) earlier than the second downlink data transmission, at least where the transmissions are associated with the same SOM.

[0211] Based on the above principles, a transmission of a given type can be initiated (or continued) at the earliest BTI for which the transmission is allowed, if it meets any delay or minimum delay conditions and / or if it is the highest priority transmission type that needs to be transmitted. In some cases, an ongoing transmission can be interrupted in a BTI that does not meet the conditions and can be resumed in a BTI that meets the conditions. Alternatively, if an ongoing transmission is interrupted, it can be stopped and canceled.

[0212] A wireless communication system, such as a 5gFLEX system, can use various approaches for determining the timing parameters described herein and can incorporate any of the embodiments described herein. For example, various approaches for deriving at least one of the following parameters for determining timing associated with a transmission type are discussed herein, including, but not limited to, the following examples: a start time, end time, and / or duration of the transmission (which can be derived, for example, from an associated frame / subframe duration), with the understanding that any one of these three parameters can be derived from the other two (i.e., duration = end time - start time; where the start time and end time can refer to the start of a frame or another time reference); a start time, end time, and / or duration of each consecutive portion of the transmission and the number of portions (in the case where transmissions occur discontinuously); a position of the transmission type in a sequence (if applicable); a set of allowed BTIs for the transmission type, if applicable (this can be referred to as a "frame structure"); a set of BTIs to which priorities between transmission types apply, if applicable; the applicability of constraint-based timing or sequence-based timing within a frame; a maximum duration of the transmission; or a start time of a frame. A frame (or subframe) "type" or "structure" may be defined as referring to a specific combination of values (or ranges thereof) for at least one of the above parameters. It will be appreciated that the scheme is therefore also applicable to determining a frame (or subframe) type or structure.

[0213] By extension, when the same BTI is used for more than one transmission type (e.g., at the boundary between two transmission types), these approaches can also be applied to indicate resource subsets within the BTI associated with the transmission type. For example, a first subset of frequency resources within a BTI can be associated with a first TTI or transmission type, and a second subset of frequency resources within the BTI can be associated with a second TTI or transmission type.

[0214] At least one timing parameter may be predefined, defined by higher layers, or depend on the duplex mode or WTRU capabilities. For example, the duration of the preamble signal may be predefined as a BTI.

[0215] At least one timing parameter can be dynamically determined based on implicit or explicit indications from downlink control information received at the beginning of the frame or in a previous frame. The indication can include a field in the downlink control information; the type of control physical channel; the search space and / or time in which the control physical channel is decoded; or an identifier for determining the applicability of the control physical channel. The following are examples of these indications.

[0216] The downlink control information may indicate a first transmission of uplink data associated with the first SOM, starting at an indicated time and having the first indicated duration, followed by a second transmission of uplink data associated with the second SOM, starting immediately after the first transmission and having the second indicated duration.

[0217] The downlink control information may indicate the start time of an uplink transmission carrying HARQ-ACK information applicable to a specific downlink transmission (ie, for a given carrier) and / or subframe type.

[0218] The type and / or DCI format of a successfully decoded downlink physical control channel can determine the timing parameters of the downlink or uplink transmission indicated by the control signaling. For example, successful decoding of a first type of physical control channel for indicating the purpose of one or more transmissions associated with a first specific SOM (e.g., an SOM suitable for ultra-low latency communication) can implicitly indicate a first set of timing parameters associated with the one or more transmissions (and / or a first subframe type), while decoding of a second type of physical control channel for indicating the purpose of one or more transmissions associated with a second specific SOM (e.g., an SOM suitable for mobile broadband communication) can implicitly indicate a second set of timing parameters (and / or a second subframe type).

[0219] The downlink control information may indicate the duration of a reference signal used in the downlink or uplink, such as a demodulation reference signal or a sounding reference signal.

[0220] The downlink control information may indicate the number of TTIs to be included in a time period (e.g., a subframe) and / or the set or number of HARQ processes to be used for a TTI. The start time and end time of each TTI may then be implicitly derived from the number of available symbols (or BTIs) within the time period (possibly excluding any symbols or BTIs used for transmission of downlink control information (e.g., a control region in the case of LTE-based transmissions). For example, the start time and end time of each TTI may be set such that all TTIs within the subframe have the same duration, possibly except for the last one. Furthermore, the start time and end time of any TTI may be constrained such that the TTI is completely contained within a subunit of the time period, such as a timeslot of a subframe.

[0221] For example, the downlink control information may indicate that two TTIs are transmitted in a subframe, or that two TTIs using HARQ processes 2 and 3 are transmitted in a subframe. In the case where the control region occupies two symbols and the subframe includes 14 symbols, this may implicitly indicate that the first TTI starts at the third symbol and ends at the eighth symbol, and the second TTI starts at the ninth symbol and ends at the fourteenth symbol. Alternatively, in the case where each TTI is constrained within a time slot, this may implicitly indicate that the first TTI starts at the third symbol and ends at the seventh symbol, and the second TTI starts at the eighth symbol and ends at the fourteenth symbol.

[0222] The downlink control information may indicate a transport block size or maximum transport block size for one or more TTIs to be included in a time period (e.g., a subframe). The start and end times of each TTI may then be implicitly derived from the modulation and coding scheme (MCS) and resource block (RB) allocation (for which the transport block size may not exceed the indicated maximum transport block size). For example, for the indicated MCS, RB allocation, and maximum transport block size, the WTRU may determine that the maximum number of symbols (or BTIs) is 3. The WTRU may determine the start and end times of each TTI based on this maximum value according to principles similar to those described above (e.g., in the previous example).

[0223] The timing parameters for a transmission type used to provide HARQ feedback information may be implicitly derived from the duration of the TTI used for the corresponding transmission, or from the number of TTIs transmitted within a time period. For example, the number of transmissions carrying HARQ feedback within a time period (e.g., a subframe) may correspond to the number of TTIs within the subframe used for the corresponding transmission. For example, if a transport block is transmitted in two TTIs within a subframe (e.g., via the PDSCH in the case of LTE-based transmissions), there may be two transmissions carrying HARQ feedback for these transport blocks within the subframe.

[0224] One or more timing parameters may be implicitly determined from properties associated with the transmission type.For example, timing information (eg, at least the duration) of a demodulation reference signal may depend on the modulation and coding scheme and rank of the associated data or control transmission.

[0225] One or more timing parameters may be implicitly determined from properties of a signal received at the beginning of the frame or in a previous frame. For example, the sequence of transmission types may be a function of a sequence used to generate a synchronization or reference signal received at the beginning of the frame or in a previous frame (e.g., a Zadoff-Chu root sequence or a cyclic shift of such a sequence).

[0226] One or more timing parameters may be determined from the payload associated with the transmission type. For example, the duration of a transmission carrying HARQ-ACK may be a function of the number of bits of HARQ-ACK information to be transmitted. In another example, the duration of a transmission carrying downlink control information may be a function of the number of bits used to dynamically indicate downlink or uplink data transmission.

[0227] One or more timing parameters may be determined from implicit or explicit indications in the transmission itself. Such indications may include, for example, properties of reference signals mapped to resources within a given BTI that may indicate whether the transmission ends at the end of the BTI (or BTI group) or continues for at least one additional BTI (or BTI group); properties of reference signals mapped to resources within a given BTI (or BTI group) that may indicate that a new transmission begins (or ends) at the beginning (or end) of the BTI (or BTI group); properties of reference signals mapped to resources within a given BTI that may indicate the duration or remaining duration of the transmission; or downlink control information multiplexed with data in the same physical channel.

[0228] In one example of downlink control information multiplexed with data in the same physical channel, an indication may be concatenated to each coded block of the transmission (e.g., at the beginning or end of the coded block). The indication may be jointly encoded with the data in each coded block or encoded separately from the data. The indication may also be used to mask a cyclic redundancy check attached to the end of each coded block. The WTRU may determine that a coded block was successfully decoded and that the transmission continued for a duration corresponding to at least one subsequent coded block by checking the value of the indication or by determining the value of the indication that produced a successful CRC after masking. The WTRU may interrupt decoding of a transmission in the event that a coded block could not be successfully decoded or in the event that a coded block was successfully decoded but the indication indicated the end of the transmission.

[0229] One or more timing parameters may be determined from the SOM associated with the transmission. For example, the duration of a transmission associated with a first SOM (e.g., suitable for ultra-low latency) may be 1 BTI, while the duration of a transmission associated with a second SOM (e.g., suitable for mobile broadband) may be 2 BTIs.

[0230] A WTRU operating in a wireless communication system, such as a 5gFLEX system, may be configured to determine frame timing and / or system frame number according to another embodiment, which may be used in combination with any of the embodiments described herein. Acquisition of frame timing may be used not only for receiving signals from an associated node (eNB or other WTRU), but also for transmission (e.g., so that other nodes can correctly receive the transmission). In the context of the variable frame structure described herein and the desire to minimize common control channels, it may be challenging or undesirable to continuously provide a periodic synchronization signal for frame timing acquisition.

[0231] The acquisition of frame timing and system frame number will be further described below in the context of a WTRU connected to or in the process of being connected to an eNB. However, these techniques are applicable to any type of node (WTRU, eNB, relay, access point, etc.). In the following, the term "synchronization source" may be used to describe a node that is used as a reference for determining synchronization. The synchronization source may be, for example, an eNB, a WTRU, an access point, a base station, a special device, a roadside unit, etc.

[0232] A WTRU or node acquiring frame timing may be configured to monitor one or more common reference signals from one or more synchronization sources.

[0233] The reference signal may include a special preamble transmitted by a synchronization source (e.g., an eNB). The WTRU may determine that the preamble may be used to determine frame timing based on the characteristics of the preamble signal. For convenience, this special preamble may be referred to herein as a synchronization preamble.

[0234] The WTRU may be configured to receive one or more preamble signals. Upon receiving a preamble, the WTRU may determine whether the received preamble is a synchronization preamble (e.g., based on preamble characteristics, such as in the case of a Zadoff-Chu sequence root, a cyclic prefix, or a combination thereof). Upon detecting a synchronization preamble, the WTRU may be configured to adjust its internal timing based on the received synchronization signal. The WTRU may also use the preamble for channel estimation, for example, to aid in signal detection of subsequent control / data information contained in the subframe.

[0235] The WTRU may be configured to receive special synchronization messages. These messages may carry one or more of a synchronization signal, an absolute time reference, a system frame number, or a time offset.

[0236] The synchronization signal or code may include a special sequence of bits (eg, Zadoff-Chu, Gold coding, etc.) that may be multiplexed with the payload and may be used as a synchronization reference.

[0237] An absolute time reference (e.g., UTC) or a shortened absolute time reference may include, for example, a synchronization message, which may carry a full or partial absolute time (system time). In one specific example, the message may include UTC time. The WTRU may then derive the absolute time, for example, regarding the time at which it received the message (and not the time at which it decoded the message).

[0238] The system frame number may be included in the synchronization message, which may carry the system frame number in full or in part.

[0239] A time offset may be included in the message, which may carry a time offset that the WTRU may apply to its internal clock. This may be motivated, for example, to bias the WTRU's internal clock so that some procedures in the WTRU that rely on time may use a different time value than that of neighboring WTRUs (implementing interference averaging mitigation techniques).

[0240] The WTRU may determine the system frame number based on the decision time. This may be achieved, for example, by shortening the most significant bit of the absolute time counter. In this case, the system frame number may not need to be explicitly communicated. This approach may benefit many aspects, including higher-layer security, which may now rely on an absolute and known counter value.

[0241] Synchronization messages can be public or private. Public synchronization messages can be transmitted or scheduled using a broadcast channel.

[0242] A node (e.g., a WTRU or an eNB) may periodically transmit synchronization messages. To reduce overhead, synchronization messages may be transmitted with a very low duty cycle. For example, a node transmitting synchronization messages may be configured to transmit synchronization messages at a specific (e.g., pre-configured) set of absolute times (e.g., expressed as UTC time). The WTRU (or synchronization device) may be configured to adjust a listening window long enough to acquire synchronization messages. In one example, the WTRU determines its listening window based on the amount of time since it acquired the absolute time and based on an estimated time drift of its internal hardware clock.

[0243] The WTRU may determine the schedule of synchronization messages with the help of neighboring nodes / cells. This may be used, for example, in situations where there is no preconfigured time for the transmission of synchronization messages or it is unavailable (e.g., when roaming to another network such as a PLMN or geographically determined). More specifically, the WTRU may receive information about the synchronization message schedule of one or more synchronization sources from the node to which it is connected. In one example, the WTRU may request / get synchronization source information from the network (e.g., via the node to which it is connected or via another RAT (e.g., LTE, HSPA, etc.)).

[0244] The synchronization message schedule may be expressed as a decision time (eg, UTC time) or relative to the system / node time to which the WTRU is connected (eg, different RAT, or other).

[0245] The WTRU may be configured to acquire frame timing by requesting synchronization from a synchronization source node. This method may be motivated, for example, in situations where the synchronization source node (eg, eNB) is a low power cell or node (which is inactive or turned off).

[0246] The WTRU may be configured to transmit one or more synchronization request messages or signals during a predefined time window. The preconfigured time window may be expressed relative to UTC time, which may have been acquired by the WTRU at a previous time. For example, the WTRU may have already acquired frame synchronization and may maintain that synchronization via its internal clock. Due to clock drift, it is expected that the WTRU may eventually become misaligned in time with the UTC time or system time and therefore assumes that the synchronization source node has a sufficiently wide listening window to appropriately receive the synchronization request message.

[0247] The WTRU may be configured to periodically transmit a synchronization request signal, and upon receiving the synchronization signal, the synchronization source may respond with a synchronization message.The method may be motivated by energy efficient operation.

[0248] The WTRU may be configured to periodically send a synchronization request message to the synchronization node if it does not receive a synchronization message during a preconfigured amount of time. This amount of time may depend on the capabilities of the WTRU and may therefore vary from one WTRU to the next.

[0249] Figure 8800 is a flow chart of an example process 800 for determining frame timing and / or system frame number according to this embodiment, which may be used in any combination with the embodiments described herein. The WTRU may first receive or acquire UTC / system time and / or frame timing clock via configuration (e.g., via a wired (e.g., USB) or wireless (e.g., GPS) connection to an external source). The WTRU may receive synchronization messages and reacquire and maintain its UTC / system time 802 and / or frame timing clock according to a synchronization message schedule preconfigured by the network. The WTRU may determine its frame timing based on the value of the received synchronization message. The WTRU may temporarily power down its transceiver, receiver, or transmitter and / or lose coverage 803 of its network. The WTRU may maintain its internal UTC clock 802 and / or frame timing clock. The WTRU may then attempt to reacquire frame timing upon powering up its transceiver, receiver, or transmitter or attempt synchronization acquisition based on a preconfigured time window of transmission of synchronization messages. If the WTRU does not receive the synchronization message 804, the WTRU may be configured to transmit a synchronization signal 805 and keep monitoring the synchronization message from the downlink. Such monitoring may be continuous, such as Figure 8 shown.

[0250] Figure 9 900 is a flow chart of an example transmission control and scheduling process 900 according to one embodiment, which may be used in any combination with the embodiments described herein. A WTRU may receive DCI 901 on a control channel, such as a PDCCH. The received DCI 901 may include DCI characteristics, including but not limited to the following: an associated control channel, a search space, an RNTI for decoding the DCI, a demodulation signal, etc. Such DCI 901 may be a DCI that allocates physical layer resources for the transmission in question. Alternatively, it may be a DCI that is specific to the scheduling of framing parameters and / or timing associated with the applicable physical layer resources (e.g., SOM).

[0251] The WTRU may then determine the subcarrier spacing Δf 902 applicable to the transmission based on one or more of the characteristics of the DCI identified above. For asynchronous operation, the subcarrier spacing may be based on properties of the preamble associated with the start of the frame. For example, the WTRU may determine the subcarrier spacing applicable to the transmission based on an indication received in the DCI. In another example, the subcarrier spacing may be for uplink transmissions. The WTRU may then determine the BTI associated with the transmission from the associated subcarrier spacing.

[0252] The WTRU may then determine the total frame duration applicable to the transmission, e.g., the TTI, based on one or more of the characteristics of the DCI identified above. DL(n)(e.g., for FDD) or TTI(n) (e.g., for TDD) 903. The duration of a TTI may be in units of BTIs, symbols, etc. For asynchronous operation, the frame transmission duration may be based on properties of the preamble associated with the start of the frame. For FDD, the duration of a TTI may be equal to the duration of the downlink transmission DL_TRx associated with frame n (when a single TB is transmitted per TTI (e.g., after first excluding the DCI duration (if applicable))); otherwise, the duration of a TTI may be used to further determine the duration of multiple DL_TRx for frame n, for example, by dividing the TTI length by the number of applicable transmissions in the frame or by combining knowledge of the durations of other DL_TRx portions for the frame, or the like. For example, if the total duration of the frame (or of the entire DL portion) is known and if the durations of all DL TTIs in the frame or DL portion are known (except one), the durations of the remaining DL TTIs may be determined. For TDD, the duration of a TTI may be equal to the duration of the downlink transmission DL_TRx, switching gap (SWG), and uplink transmission UL_TRx associated with frame n (when a maximum of one TB is transmitted per UL or DL portion of the framed arrangement); otherwise, the duration of the TTI may be determined in a manner similar to the case of FDD. Multiple DL_TRx portions and / or UL_TRx portions may be supported. For example, the WTRU may determine such duration applicable to the transmission based on an indication received in the DCI.

[0253] The WTRU may then determine the uplink transmission start time offset (e.g., t offset ) 904. For asynchronous operation, the transmission start time may be based on properties of the preamble associated with the start of the frame. For FDD, if multiple UL_TRx parts are supported, then the WTRU may determine a single offset applicable to the first uplink part if all uplink parts are in consecutive symbols for the frame in question, otherwise it may determine an offset for each part. For example, the WTRU may determine one or more transmission start time offsets applicable to the transmission based on an indication received in the DCI.

[0254] The WTRU may then determine the downlink TB duration applicable for the transmission based on one or more of the characteristics of the DCI identified above, e.g., t DL(n) 905. For asynchronous operation, the downlink TB duration may be based on properties of the preamble associated with the start of the frame. If multi-DL_TRx operation is supported, the WTRU may determine one value t for all parts if all parts have the same duration within the frame (e.g., for operations such as bundling). DL(n), otherwise a value is determined for each portion. For example, the WTRU may determine one or more downlink TB durations applicable to the transmission based on an indication received in a DCI.

[0255] The WTRU may then determine the uplink TB duration applicable for the transmission based on one or more of the above-identified characteristics of the DCI, e.g., t UL(n) 906. For asynchronous operation, the uplink TB duration may be based on properties of the preamble associated with the start of the frame. If multiple UL_TRx parts are supported, the WTRU may determine a value t for all parts if all parts have the same duration within the frame (e.g., for operations such as bundling). UL(n) , otherwise a value is determined for each portion. For example, the WTRU may determine one or more uplink TB durations applicable to the transmission based on an indication received in a DCI.

[0256] The WTRU may then determine a time until the start of a subsequent frame (e.g., an inter-frame time, such as an applicable ISS from the end of the associated frame) based on one or more of the characteristics of the DCI identified above. For asynchronous operation, the time until the start of a subsequent frame may be based on properties of a preamble associated with the start of the frame. For example, the WTRU may determine a time until the start of a subsequent frame, such as an offset from the start of the current frame. Such an offset may be used by the WTRU to determine whether it may inhibit decoding control signaling until the start of a subsequent frame (e.g., applying DRX to the control channel in question). For example, the WTRU may determine such a time until the start of a subsequent frame based on an indication received in the DCI.

[0257] The WTRU may then determine the duration of a switching gap (SWG) (and / or silent / blank period) applicable to the current frame based on one or more of the characteristics of the DCI identified above 908. For asynchronous operation, the duration of the switching gap may be based on properties of the preamble associated with the start of the frame. For example, the WTRU may determine such a gap and / or period based on an indication received in the DCI.

[0258] The WTRU may then determine the timing relationship between the DL data and UCI for the received DL TRx portion 909 for HARQ parameterization based on one or more of the above-identified characteristics of the DCI. The WTRU may derive in which UL TRx portion and / or in which frame and / or with which parameters it may transmit DL HARQ feedback corresponding to the received DL data to the eNB. The WTRU may determine from the received HARQ parameterization whether it may aggregate the HARQ feedback for one or more received DL data channels for the purpose of generating UL control information. The WTRU may derive the timing relationship between the transmission of UL data and the reception of DL control information in one or more UL TRx portions, the parameters to be used for aggregation and encoding of DL control information corresponding to the multiple received UL data channels.

[0259] Figure 10 is a flow chart of an example link adaptation and scheduling process 1000 according to one embodiment, which may be used in combination with any of the embodiments described herein. The WTRU may determine parameters for downlink and uplink transmissions used in link adaptation and other transmission control aspects. Link adaptation and scheduling may be time period based. For example, referring to Figure 10 , the WTRU may receive 1001 at least one transmission parameter for an uplink or downlink transmission, which may be a function of explicit or implicit indications received from more than one instance of downlink control signaling.

[0260] The more than one instances of receiving 1001 may, for example, include a first instance and / or a second instance, such as a first DCI and a second DCI, respectively. The first instance (e.g., DCI) may indicate at least one parameter applicable to a set of transmissions occurring in a subsequent time period. For example, such a time period may be a duration equal to a 1 ms subframe, which may, for example, correspond to one LTE subframe (1 ms). Such a first instance may be referred to as "slow" downlink control signaling. The second instance (e.g., a second DCI) may indicate additional parameters applicable to a specific transmission of the set within the time period. This second instance may be referred to as "fast" downlink control signaling. The downlink control signaling applicable to each instance may be decoded from different types of physical downlink control channels, possibly in different search spaces and using different identifiers.

[0261] refer to Figure 10The WTRU may decode a second instance of downlink control signaling 1002 (e.g., a second DCI) based on explicit information derived from the first instance of downlink control signaling (e.g., the first DCI) and / or based on implicit information derived from attributes of the transmission containing the first instance of downlink control signaling. For example, the resources or possible resource sets used for the second instance of downlink control signaling may be determined from the resources used for the first instance of downlink control signaling and / or from at least one explicit indication derived from the first instance of downlink control signaling. The resources may include a set of resource blocks, a serving cell (or carrier), a set of time symbols, a set of antenna ports, a scrambling code identifier for a reference signal, or a control channel element (CEE), such as at least one of the first CCEs associated with the first instance of downlink control signaling. Alternatively, in the case of a downlink transmission, the downlink control signaling may be multiplexed with data in the same physical channel. For example, the second instance of downlink control signaling (e.g., the second DCI) may be encoded separately from the downlink data, and the modulation symbols from the downlink control signaling may be mapped onto specific time or frequency resources, such as in the first time symbol of the transmission.

[0262] Additional examples of period-based link adaptation and scheduling that the WTRU may perform. For example, see Figure 10, the WTRU may determine the MCS 1003 applicable for downlink or uplink transmissions. The WTRU may determine the MCS 1003 using a number of methods. For example, the WTRU may determine the MCS 1003 by determining the sum of a first MCS value received in a first instance (e.g., a first DCI) and a second MCS value received in a second instance (e.g., a second DCI). The number of possible values may be higher for the first instance (e.g., the first DCI) than for the second instance (e.g., the second DCI), allowing for a reduction in the overhead of control signaling applicable to a particular transmission. For example, the first instance (e.g., the first DCI) may indicate a value ranging from 0 to 31, while the second instance (e.g., the second DCI) may indicate an adjustment value ranging from -2 to 1. Alternatively, there may be no parameters related to the MCS provided in the second instance (e.g., the second DCI), resulting in the same MCS value being applied to all transmissions during the time period. The WTRU may determine the MCS 1003 applicable for downlink transmissions by performing an adjustment to the MCS after reception of each coding block (or each transport block) based on the indication. The indication may be concatenated to each coded block transmitted (e.g., at the beginning or end of a coded block) or each transport block. The indication may be encoded jointly with the data in each coded block or separately. The indication may also be used to mask a CRC attached to the end of each coded block (or transport block). The WTRU may determine an adjustment to the MCS level to apply to subsequent coded blocks (or transport blocks) based on the value of the indication. The adjustment may be relative to the MCS value received in the first instance of the downlink control information, or relative to the last adjusted MCS value.

[0263] refer to Figure 10 , the WTRU may determine an allocation 1004 (e.g., a set of resource blocks) in the frequency domain by combining an indication received in a first instance (e.g., a first DCI) with an indication received in a second instance (e.g., a second DCI). For example, the indication in the first instance (e.g., a first DCI) may include the complete set of resource blocks that may be used by applicable transmissions for the time period. Such an indication may have a high granularity (e.g., 20 bits). The indication in the second instance (e.g., a second DCI) may indicate a subset of the allocation indicated in the first instance (e.g., a first DCI) using a low number of bits for a particular transmission. For example, a first value may indicate that all resource blocks are used for a particular transmission, a second value may indicate that only the first half of the allocation is used, a third value may indicate that only the second half of the allocation is used, and so on. It is also possible that no indication is provided in the second instance, such that the same allocation is used for all transmissions in the time period.

[0264] refer to Figure 10, the WTRU may determine resource allocation 1005 (e.g., a set of time symbols and / or timing) in the time domain of the transmission by combining an explicit indication received in a first instance (e.g., a first DCI) with an implicit indication of successful decoding from a second instance (e.g., a second DCI). The first instance may relate to or indicate multiple sets of one or more time symbols in which a second instance of downlink signaling and / or data (in the case of a downlink transmission) may be transmitted. For example, the first instance (e.g., a first DCI) may indicate a first set of time symbols (e.g., from the second to the seventh) and a second set of time symbols (e.g., from the eighth to the fourteenth) of an LTE subframe. The WTRU may attempt to decode the second instance of downlink control signaling (e.g., the second DCI) in specific resources (or search spaces) within each set of time symbols. The WTRU may determine that the second instance of downlink control signaling (e.g., the second DCI) was successfully decoded based on a cyclic redundancy check (CRC) attached to the payload. The WTRU may then determine the timing of the downlink or uplink transmission based on the set of time symbols within which the second instance of downlink signaling (e.g., the second DCI) was successfully decoded. For example, if the second instance (e.g., the second DCI) is successfully decoded in the eighth time symbol, the WTRU may determine that the downlink transmission is allocated within the second set of time symbols. In another example, the WTRU may be configured to use the applicable set of time symbols for a given frame (e.g., an LTE subframe). The first instance (e.g., the first DCI) may indicate for which set the WTRU is expected to perform further processing of the DCI in a manner similar to that described above.

[0265] refer to Figure 10, the WTRU may determine further HARQ process states 1006 based on the same indication as above in the first instance of downlink control signaling (e.g., the first DCI). Each symbol set may be further associated with a HARQ process identification space, e.g., where a single HARQ process may be active per frame, e.g., per LTE subframe, for each such space and / or symbol set. Alternatively, each symbol set may be further associated with a HARQ process identifier, e.g., such as an identifier that increments for each symbol set starting from the first symbol of the frame and onward. In other words, the HARQ process identifier may increment sequentially over time for each symbol set. For example, the WTRU may receive HARQ feedback for one or more previous uplink transmissions, e.g., using the Physical HARQ Indicator Channel (PHICH) in LTE. Such feedback may be received based on slow control information timing, e.g., once per frame, e.g., a 1 ms subframe in LTE. The WTRU may use this feedback to determine whether it can perform a WTRU-autonomous retransmission for the applicable HARQ process, e.g., if the WTRU is configured to perform such a retransmission. For example, in LTE, the WTRU may perform autonomous retransmissions in accordance with its synchronized HARQ processes in the uplink. In other words, the WTRU may interpret this feedback as an indication to enable or disable WTRU autonomous transmissions for the HARQ process in question. This HARQ state may be further determined based on the indication in the first instance. For example, if WTRU autonomous retransmissions are enabled, this determination may correspond to a command to suspend one or more of the HARQ processes in question and / or to disable any WTRU autonomous retransmissions (e.g., where the WTRU determines that it is not desired to perform further processing for the associated set of symbols). Alternatively, the WTRU may interpret the PHICH in accordance with legacy WTRU behavior and perform a logical function (e.g., a logical AND) using the indication of this setting in the first instance of downlink control signaling. For example, such control signaling may include one bit for each symbol set, further indicating HARQ-related feedback for each HARQ process in the frame (e.g., LTE subframe), and further indicating whether (adaptive transmission, if applicable) or not (non-adaptive retransmission, if applicable) the WTRU is expected to perform further processing of the downlink control information in a manner similar to the above.

[0266] refer to Figure 10 If a certain set of identification parameters is indicated in (or used to decode) a first and a second instance of downlink control signaling (e.g., a first and a second DCI), the WTRU may determine that a downlink or uplink transmission is scheduled for that WTRU 1007. The same parameters (e.g., a cell radio network temporary identifier (C-RNTI)) may be used to mask the CRC of the payload attached to the first and second instances (e.g., the first and the second DCI).

[0267] The first and second identification parameters of the first and second instances (e.g., the first and second DCIs) can be derived based on the same C-RNTI and used to mask the CRC of the payload attached to the first and second instances, respectively. For example, the first identification parameter can correspond to an RNTI value assigned or defined for operation with two instances of downlink control signaling, and the second identification parameter can correspond to the C-RNTI or a function thereof. In this example, the first instance of downlink control signaling (e.g., the first DCI) can also indicate a set of short identifications corresponding to WTRUs that can be scheduled in the time period. The short identification can be a function or hash based on the C-RNTI or other means, or can be assigned by a higher layer. The WTRU can determine that a downlink or uplink transmission is scheduled if it is indicated by a short identification from the first instance (e.g., the first DCI), it has decoded itself using the first identification, and it has successfully decoded the second instance (e.g., the second DCI) using its second identification.

[0268] In another example, an explicit indication from a first instance of downlink control signaling (e.g., a first DCI) can be used to derive a second identification parameter. The second identification parameter can be used to decode a second instance of downlink control signaling (e.g., a second DCI). For example, it can be included in the payload or used to mask a cyclic redundancy check (CRC) attached to the payload.

[0269] In another example, a first instance of downlink control signaling (e.g., a first DCI) may include an ordered set of identification parameters (e.g., a C-RNTI or a function thereof) indicating a set of WTRUs that may receive a second instance of downlink control signaling (e.g., a second DCI) during an applicable time period. The WTRU may derive the second identification parameter based on the order of its identification within the set of identification parameters indicated in the first instance (the first DCI).

[0270] One or more of the following parameters applicable to downlink or uplink transmissions may be used Figure 10 The link adaptation and scheduling process 1000 is derived from the first (slow) instance of downlink control signaling (e.g., the first DCI):

[0271] a second (fast) instance of downlink control signaling applicable to the transmission (e.g., a second DCI) and / or an indication of a resource or possible set of resources for the transmission (e.g., an indication of a set of resource blocks or an indication of a time domain structure, where the structure includes a set of possible initial and final time symbols for the transmission); a carrier indicator; a modulation and coding scheme; an order; a set of antenna ports; an indication of at least one reference signal used as a timing reference and / or demodulation reference; and / or a power control command.

[0272] One or more of the following parameters applicable to the same downlink or uplink transmission may be derived from a second (fast) instance of downlink control signaling (e.g., a second DCI):

[0273] A HARQ process identifier applicable to a downlink or uplink transmission; a retransmission sequence number and / or redundancy version; an indication of whether the transmission is a retransmission or new data (or an initial transmission); HARQ feedback information (e.g., a PHICH or a value that can be logically combined with the PHICH received for the time period in question (e.g., an LTE subframe); an indication of a parameter applicable to at least one reference signal, such as at least one cyclic shift index (e.g., for uplink transmissions); an indication of operation in an unlicensed band, such as a request to provide information on whether the channel is busy (e.g., a clear channel assessment); and / or an indication of resources for providing control signaling for HARQ-related feedback for the transmission (e.g., a PUCCH for downlink transmissions, a HARQ-ACK on a PHICH for uplink transmissions).

[0274] Although features and elements are described above in particular combinations, it will be understood by those skilled in the art that each feature or element can be used alone or in any combination with the other features and elements. In addition, the methods described herein may be implemented using a computer program, software, and / or firmware, which may be incorporated into a computer-readable medium executed by a computer and / 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, buffer memory, semiconductor memory devices, magnetic media (such as internal hard disks and removable disks), magneto-optical media, and optical media (such as CD-ROM disks and digital versatile disks (DVDs)). A processor associated with the software is used to implement a radio frequency transceiver for use in a WTRU, UE, terminal, base station, eNB, RNC, or any host computer.

Claims

1. A method for implementing flexible downlink control information (DCI) transmission timing using a variable time offset, comprising: receiving, by a wireless transmit / receive unit (WTRU), downlink control information (DCI) in a physical downlink control channel (PDCCH) transmission, the DCI including an indication of a starting symbol timing for a downlink transmission, an indication of a number of symbols used for the downlink transmission, an indication of a time offset for an uplink transmission, and an indication of resources used for the uplink transmission; receiving, by the WTRU, the downlink transmission based on the starting symbol timing and the number of symbols indicated in the DCI; as well as The uplink transmission is transmitted by the WTRU using the time offset and the resources indicated by the DCI.

2. The method according to claim 1, wherein The uplink transmission includes hybrid automatic repeat request (HARQ) information.

3. The method according to claim 1, wherein The uplink transmission includes uplink control information (UCI). 4 . The method of claim 1 , further comprising receiving configuration information indicating a set of resources to be used for uplink control information (UCI).

5. The method of claim 1, further comprising interrupting the uplink transmission so that the uplink transmission does not occur in symbols indicated by the starting symbol timing and the number of symbols for a resource set indicated in the DCI.

6. The method according to claim 1, wherein The DCI in the PDCCH transmission includes a first DCI, and The method further comprises: receiving a second DCI, and The second DCI is decoded based on at least one of the following of the first DCI: the indication of the starting symbol timing for the downlink transmission, the indication of the number of symbols used for the downlink transmission, the indication of the time offset for the uplink transmission and the indication of resources used for the uplink transmission.

7. The method according to claim 1, wherein The DCI in the PDCCH transmission includes a first DCI, and The method further includes receiving a second DCI in at least one symbol of the number of symbols used for the downlink transmission. 8 . The method according to claim 7 , wherein the second DCI includes information indicating resources used for the uplink transmission, a starting symbol for the uplink transmission, and a number of symbols corresponding to a duration of the uplink transmission.

9. The method according to claim 7, wherein: The second DCI indicates a subcarrier spacing used for the uplink transmission.

10. The method according to claim 7, further comprising: receiving a third DCI including an indication regarding a second set of one or more downlink symbols and an indication regarding a second set of one or more uplink symbols; receiving a fourth DCI received in at least one of the second set of one or more downlink symbols, the fourth DCI including information indicating resources used for a downlink transmission, a starting symbol for the downlink transmission, and a number of symbols corresponding to a duration of the downlink transmission; as well as The downlink transmission is received according to the resource, the starting symbol, and the number of symbols indicated by the fourth DCI.

11. The method according to claim 10, wherein the fourth DCI indicates timing information for transmission of hybrid automatic repeat request (HARQ) ACK / NACK information for the downlink transmission.

12. The method according to claim 11, wherein The timing information is indicated as an offset value.

13. The method of claim 11, wherein the fourth DCI indicates resources used to transmit the HARQ ACK / NACK information for the downlink transmission.

14. The method of claim 7, wherein the first DCI indicates a switching gap between one or more downlink symbols and one or more uplink symbols.

15. A wireless transmit / receive unit (WTRU), the WTRU comprising: Receiver; transmitter; as well as processor, The receiver and the processor are configured to: receiving downlink control information (DCI) in a physical downlink control channel (PDCCH) transmission, the DCI including an indication of a starting symbol timing for a downlink transmission, an indication of a number of symbols used for the downlink transmission, an indication of a time offset for an uplink transmission, and an indication of resources used for the uplink transmission; as well as receiving the downlink transmission based on the starting symbol timing and the number of symbols indicated in the DCI; as well as The transmitter and the processor are configured to send the uplink transmission using the time offset and the resources indicated by the DCI.

16. The WTRU of claim 15, wherein the uplink transmission comprises hybrid automatic repeat request (HARQ) information.

17. The WTRU of claim 15, wherein the uplink transmission comprises uplink control information (UCI).

18. The WTRU of claim 15, wherein the receiver and the processor are further configured to receive configuration information indicating a set of resources to be used for uplink control information (UCI).

19. The WTRU of claim 15, wherein the processor and the transmitter are further configured to interrupt the uplink transmission so that the uplink transmission does not occur in a symbol indicated by the start symbol timing and the number of symbols for a resource set indicated in the DCI.

20. The WTRU of claim 15, wherein: The DCI in the PDCCH transmission includes a first DCI; The receiver and the processor are further configured to receive a second DCI; as well as The processor is further configured to decode the second DCI based on at least one of the first DCI: the indication of the start symbol timing for the downlink transmission, the indication of the number of symbols for the downlink transmission, the indication of the time offset for the uplink transmission, and the indication of resources for the uplink transmission.

21. The WTRU of claim 15 wherein the DCI in the PDCCH transmission comprises a first DCI, and in, The processor and the receiver are further configured to receive a second DCI in at least one symbol of the number of symbols used for the downlink transmission.

22. The WTRU of claim 21, wherein the second DCI includes information indicating resources used for the uplink transmission, a starting symbol for the uplink transmission, and a number of symbols corresponding to a duration of the uplink transmission.

23. The WTRU of claim 21 , wherein the second DCI indicates a subcarrier spacing to be used for the uplink transmission.

24. The WTRU of claim 21 , wherein the processor and the receiver are further configured to: receiving a third DCI including an indication regarding a second set of one or more downlink symbols and an indication regarding a second set of one or more uplink symbols; receiving a fourth DCI received in at least one of the second set of one or more downlink symbols, the fourth DCI including information indicating resources used for a downlink transmission, a starting symbol for the downlink transmission, and a number of symbols corresponding to a duration of the downlink transmission; as well as The downlink transmission is received according to the resource, the starting symbol, and the number of symbols indicated by the fourth DCI.

25. The WTRU of claim 24, wherein the fourth DCI indicates timing information for transmission of hybrid automatic repeat request (HARQ) ACK / NACK information for the downlink transmission.

26. The WTRU of claim 25, wherein the timing information is indicated as an offset value.

27. The WTRU of claim 25, wherein the fourth DCI indicates resources used to transmit the HARQ ACK / NACK information for the downlink transmission.

28. The WTRU of claim 21 , wherein the first DCI indicates a switching gap between one or more downlink symbols and one or more uplink symbols.

29. A base station, comprising: Receiver; transmitter; as well as processor, The transmitter and the processor are configured to: sending downlink control information (DCI) in a physical downlink control channel (PDCCH) transmission, the DCI including an indication of a starting symbol timing for a downlink transmission, an indication of a number of symbols used for the downlink transmission, an indication of a time offset for an uplink transmission, and an indication of resources used for the uplink transmission; as well as transmitting the downlink transmission based on the starting symbol timing and the number of symbols indicated in the DCI; as well as The receiver and the processor are configured to receive the uplink transmission using the time offset and the resources indicated by the DCI.

30. The base station according to claim 29, wherein The uplink transmission includes hybrid automatic repeat request (HARQ) information.

31. The base station according to claim 29, wherein The uplink transmission includes uplink control information (UCI).

32. The base station according to claim 29, wherein The transmitter and the processor are further configured to transmit configuration information indicating a set of resources for uplink control information (UCI).

33. The base station of claim 29, wherein the processor and the receiver are further configured to interrupt reception of the uplink transmission such that the uplink transmission does not occur in a symbol indicated by the start symbol timing and the number of symbols for a resource set indicated in the DCI.

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