Methods and apparatus for ue-initiated cot for fbe

Abstract

A user equipment (UE) in a frame-based equipment (FBE) mode can determine that a communication channel in an unlicensed frequency spectrum is available and transmit a transmission in the communication channel to a gNB within a fixed frame period (FFP) associated with the UE to initiate a channel occupancy time (COT) by the UE within the FFP. The transmission starts at a beginning of the FFP and ends before an idle period within the FFP. The gNB receives the transmission and determines, based on the transmission, that the UE has initiated the COT. The gNB can confirm or reject the initiation of the COT by the UE.

Description

[0001] CLAIM OF PRIORITY

[0002] This patent application claims priority to U.S. Provisional Application No. 63 / 062,193, entitled “Method and Apparatus for UE initiated channel occupation time for frame based equipment” and filed on August 6, 2020, and U.S. Provisional Patent Application No. 63 / 104,318, entitled “Method and Apparatus for UE initiated COT for FBE” and filed on October 22, 2020, the entire contents of both applications are incorporated herein by reference. TECHNICAL FIELD

[0003] The present disclosure relates generally to wireless communications, and in particular embodiments, to techniques and mechanisms for UE initiated channel occupancy time (COT) for frame based equipment (FBE). BACKGROUND

[0004] Recently, unlicensed spectrum (also referred to as non-licensed spectrum or shared spectrum) has attracted strong interest from cellular operators. Long Term Evolution Licensed Assisted Access (LTE-LAA) was specified in 3GPP LTE Releases (Rel) 13 and 14. More recently, in New Radio-Unlicensed (NR-U), operation in unlicensed (or shared) spectrum was specified in 3GPP New Radio (NR) Release 16 (3GPP TS 38.213, the entire contents of which are incorporated herein by reference).

[0005] 3GPP and IEEE technologies operating in unlicensed spectrum use listen before talk (LBT) channel access. In some regions, such as the European Union (EU) and Japan, LBT rules are typically enforced by the spectrum regulator to reduce the risk of interference and provide a more fair coexistence mechanism. LBT mechanisms require a transmitter to check if the channel is occupied by other occupants before transmission, and if the channel is occupied, to defer transmission.

[0006] In particular, as specified in the European Standard (EN) 301 893 by the European Telecommunications Standards Institute (ETSI) for the 5 GHz band, the LBT rules in the EU use a clear channel assessment (CCA) to determine whether a channel is available for transmission. The CCA checks whether the energy received on the channel is above a CCA threshold. If the detected energy exceeds the CCA threshold, the channel is considered in use (busy); otherwise, the channel is considered clear. If the channel is clear, the transmitter can transmit in at least a portion (e.g., 80%) of the total channel bandwidth for a duration of a channel occupancy time (COT). In ETSI EN 301 893 V2.1.1 (2017-05), which is incorporated herein by reference in its entirety, the maximum COT duration for a transmission burst is also specified. The maximum COT (MCOT) duration employed in 3GPP NR-U Rel 16 (TS 37.213, which is incorporated herein by reference in its entirety) is a function of the channel access priority class (CAPC). As defined in TS 37.213, for the determination of the COT, if the transmission gap (interval between consecutive transmissions) is less than or equal to 25 microseconds (μs), the transmission gap duration counts towards the COT. A transmission burst is defined as a set of transmissions with an interval (i.e., transmission gap) not greater than 16 μs, and if the interval is greater than 16 μs, the set of transmissions is considered separate.

[0007] 3GPP Rel 16 (TS 37.213) defines several channel access types for downlink (DL) and uplink (UL) in unlicensed spectrum.

[0008] In Type 1 DL channel access, after first sensing the channel to be clear for a sensing slot duration of T d sensing slot duration of 9 μs. Type 1 DL channel access is used before starting a new COT, where the COT duration can be up to 10 ms depending on the traffic priority.

[0009] Type 2 DL channel access includes a deterministic duration of channel sensing during which the channel needs to be sensed as idle. Type 2 DL channel access includes Type 2A, Type 2B and Type 2C channel access.

[0010] Type 2A channel access allows a transmission if the channel is sensed as idle for a sensing interval of at least 25 μs prior to the transmission.

[0011] Type 2B channel access allows a transmission if the channel is sensed as idle for a sensing interval of at least 16 μs prior to the transmission.

[0012] Type 2C channel access allows a transmission with a duration not exceeding 584 μs without requiring channel sensing prior to the transmission.

[0013] Type 2A DL channel access procedure is applicable in shared COT after a user equipment (UE) transmission and for transmissions including discovery bursts with a duration up to 1 ms and a duty cycle up to 1 / 20.

[0014] Type 2B or Type 2C DL channel access procedure is applicable in shared channel occupancy after a UE transmission for an interval of 16 μs or up to 16 μs, respectively.

[0015] Similar to DL channel access types, TS 37.213 defines UL channel access procedures, where Type 1 UL channel access is based on sensing the channel as idle for a fixed delay duration (Td) and then until a random backoff counter N decrements to 0 for each idle sensing slot, as in Type 1 DL channel access. Type 2 UL channel access requires the channel to be sensed as idle for a fixed (deterministic) duration prior to the transmission, where Type 2A UL channel access requires a channel idle duration of at least 25 μs prior to the transmission, while Type 2B UL channel access requires a channel idle duration of at least 16 μs prior to the transmission. Type 2C allows a transmission up to 584 μs long without requiring any channel sensing. SUMMARY

[0016] Embodiments of the present disclosure describe methods and apparatuses for receiver assisted transmissions in shared spectrum, technical advantages can generally be achieved by these embodiments.

[0017] According to an aspect of the present disclosure, a method is provided, the method comprising: determining, by a user equipment (UE) in a frame based equipment (FBE) mode, that a communication channel in an unlicensed spectrum is available; transmitting, by the UE, a first transmission in the communication channel within a fixed frame period (FFP) associated with the UE to a gNB to initiate, by the UE, a first channel occupancy time (COT) within the FFP, the first transmission starting at a beginning of the FFP and ending before an idle period within the FFP.

[0018] Optionally, in any of the above aspects, determining that the communication channel is available comprises: performing, by the UE, a clear channel assessment (CCA).

[0019] Optionally, in any of the above aspects, determining that the communication channel is available comprises: starting, by the UE, a backoff counter after a CCA succeeds; and determining, by the UE, that the communication channel is available when the backoff counter decrements to zero (0).

[0020] Optionally, in any of the above aspects, the first transmission comprises a physical uplink control channel (PUCCH), a physical uplink shared channel (PUSCH), channel state information (CSI), a scheduling request (SR), a random access preamble, or a sounding reference signal (SRS).

[0021] Optionally, in any of the above aspects, the first transmission occupies all or a portion of a frequency bandwidth of the communication channel.

[0022] Optionally, in any of the above aspects, the method further comprises: receiving, by the UE, information of a time interval (T UE COT) in which the UE is allowed to initiate a periodic COT, the time interval T UE COT comprising the FFP.

[0023] Optionally, in any of the above aspects, the first COT is a periodic COT initiated by the UE.

[0024] Optionally, in any of the above aspects, the method further comprises: receiving, by the UE, a configuration configuring the UE to initiate a semi-static COT in the communication channel.

[0025] Optionally, in any of the above aspects, the method further includes: the UE receiving configuration information of the first COT, the configuration information of the first COT including one or more of: a COT index of the first COT; a periodicity of the FFP; a maximum allowed COT (MCOT) duration within the FFP; a time offset of the FFP; a minimum idle duration within the FFP; a maximum idle duration within the FFP; an offset of the FFP; or a frequency resource for uplink transmission during the first COT.

[0026] Optionally, in any of the above aspects, the offset of the FFP or the starting position of the FFP is relative to a boundary of a radio frame with an even index number.

[0027] Optionally, in any of the above aspects, the periodicity of the FFP includes a value in {1, 2, 2.5, 4, 5, 10} in milliseconds (ms).

[0028] Optionally, in any of the above aspects, the periodicity of the FFP includes any value in {1, 2, 2.5, 4, 5, 10} in milliseconds (ms) or a subset of values in {1, 2, 2.5, 4, 5, 10} in milliseconds (ms) according to a capability of the UE to initiate the COT.

[0029] Optionally, in any of the above aspects, the periodicity ranges from 1 ms to 10 ms.

[0030] Optionally, in any of the above aspects, the configuration information is received through dedicated RRC signaling.

[0031] Optionally, in any of the above aspects, the method further includes: the UE receiving information of a listen before talk (LBT) type for listening to the communication channel.

[0032] Optionally, in any of the above aspects, the method further includes: in response to transmitting the first transmission, the UE receiving an indication from the gNB indicating whether the initiation of the first COT by the UE is confirmed or rejected.

[0033] Optionally, in any of the above aspects, the method further includes: the UE determining that the initiation of the first COT by the UE is confirmed when the UE receives a transmission from the gNB within a time period after transmitting the first transmission, or determining that the initiation of the first COT is rejected when no transmission is received from the gNB within the time period.

[0034] Optionally, in any of the above aspects, the method further comprises: when initiation of the first COT by the UE is confirmed, the UE performing the uplink transmission within the first COT.

[0035] Optionally, in any of the above aspects, the method further comprises: when initiation of the first COT by the UE is denied, the UE performing the uplink transmission within a second COT initiated by the gNB.

[0036] Optionally, in any of the above aspects, the method further comprises: the UE sending a request to the gNB requesting a new COT to be used by the UE, the new COT requested being a COT initiated by the UE.

[0037] Optionally, in any of the above aspects, the method further comprises: the UE starting a timer after sending the request; and, the UE receiving an indication from the gNB indicating that the request is accepted before the timer expires, and the UE performing the transmission within the new COT; or, when the request is not accepted by the gNB before the timer expires, the UE sending another request for a new COT to the gNB.

[0038] Optionally, in any of the above aspects, the request is sent in a third COT initiated by the gNB or initiated by the UE.

[0039] Optionally, in any of the above aspects, the request comprises parameters of the new COT.

[0040] Optionally, in any of the above aspects, the method further comprises: the UE receiving, within the first COT, signaling indicating that the UE switches from transmission according to the first COT to transmission according to a fourth COT.

[0041] Optionally, in any of the above aspects, the signaling comprises information of a remaining duration of the fourth COT.

[0042] Optionally, in any of the above aspects, the method further comprises: the UE starting a transition timer after receiving the signaling.

[0043] Optionally, in any of the above aspects, the method further comprises: in response to the fourth COT ending before the transition timer expires, the UE continuing to perform the transmission within the first COT.

[0044] Optionally, in any of the above aspects, the method further comprises: the UE switching to using the fourth COT for transmission after the transition timer expires.

[0045] Optionally, in any of the above aspects, the fourth COT is a COT initiated by the UE, and the method further comprises: the UE initiating the fourth COT within a next FFP.

[0046] Optionally, in any of the above aspects, the fourth COT is a gNB-initiated COT, and the method further includes the UE monitoring for and sharing the fourth COT within a next FFP.

[0047] Optionally, in any of the above aspects, the method further includes the UE transmitting capability information indicating a capability of the UE to initiate a COT.

[0048] According to another aspect of the disclosure, a method is provided that includes a gNB receiving a first transmission within a fixed frame period (FFP) from a user equipment (UE) in a communication channel of an unlicensed spectrum, wherein the UE is in a frame based equipment (FBE) mode; in response to the first transmission starting at a beginning of the FFP and ending before an idle period of the FFP, the gNB determining, based on the first transmission, that the UE initiated a first channel occupancy time (COT) within the FFP.

[0049] Optionally, in any of the above aspects, the first transmission includes a PUCCH, a configured grant based PUSCH, channel state information (CSI), a scheduling request (SR), a random access preamble, or a sounding reference signal (SRS).

[0050] Optionally, in any of the above aspects, the first transmission occupies all or a portion of a frequency bandwidth of the communication channel.

[0051] Optionally, in any of the above aspects, the method further includes the gNB transmitting, to the UE, information of a time interval (T UE COT) in which the UE is allowed to initiate a periodic COT, the time interval T UE COT comprising the FFP.

[0052] Optionally, in any of the above aspects, the method further includes the gNB transmitting, to the UE, a configuration configuring the UE to initiate a semi-static COT in the communication channel.

[0053] Optionally, in any of the above aspects, the method further includes the UE transmitting configuration information of the first COT, wherein the configuration information of the first COT includes one or more of: a COT index of the first COT; a periodicity of the FFP; a maximum allowed COT duration (MCOT) within the FFP; a time offset of the FFP; a minimum idle duration within the FFP; a maximum idle duration within the FFP; an offset of the FFP; or a frequency resource for uplink transmission during the first COT.

[0054] Optionally, in any of the above aspects, the offset of the FFP or a starting position of the FFP is relative to a boundary of a radio frame with an even index number.

[0055] Optionally, in any of the above aspects, the method further includes: in response to receiving the first transmission, the gNB transmitting, to the UE, an indication indicating whether the initiation of the first COT by the UE is confirmed or rejected.

[0056] Optionally, in any of the above aspects, the indication is carried in a PDCCH, a DCI, or a HARQ ACK.

[0057] Optionally, in any of the above aspects, the method further includes: in response to receiving the first transmission, the gNB transmitting, to the UE, a transmission within a time period to confirm the initiation of the first COT; or the gNB not performing a downlink transmission to the UE within the time period to indicate that the initiation of the first COT is rejected.

[0058] Optionally, in any of the above aspects, the method further includes: the gNB receiving, from the UE, a request requesting a new COT to be used by the UE, the requested new COT being a COT initiated by the UE.

[0059] Optionally, in any of the above aspects, the method further includes: the gNB indicating to the UE whether the request is accepted.

[0060] Optionally, in any of the above aspects, the request is received in a third COT that has been initiated by the gNB or has been initiated by the UE.

[0061] Optionally, in any of the above aspects, the request includes parameters of the new COT.

[0062] Optionally, in any of the above aspects, the method further includes: the gNB transmitting, to the UE within the first COT, signaling indicating that the UE switches from transmission according to the first COT to transmission according to a fourth COT.

[0063] Optionally, in any of the above aspects, the signaling includes information of a remaining duration of the fourth COT.

[0064] Optionally, in any of the above aspects, the fourth COT is a COT initiated by the gNB or a COT initiated by the UE.

[0065] Optionally, in any of the above aspects, the method further includes: the gNB receiving, from the UE, capability information indicating a capability of the UE to initiate a COT.

[0066] Optionally, in any of the above aspects, the method further comprises: the gNB receiving, from the plurality of UEs in the communication channel, a plurality of transmissions of the respective UEs within the FFP, each of the plurality of transmissions starting at the beginning of the FFP and ending before the idle period of the FFP; the gNB determining that each of the plurality of UEs initiates the first COT within the FFP; the gNB acknowledging the first COT initiated by the UE; and, the gNB rejecting the first COT initiated by the other UEs of the plurality of UEs.

[0067] Optionally, in any of the above aspects, the method further comprises: the gNB cancelling the first COT initiated by the UE within the FFP.

[0068] According to another embodiment of the disclosure, a system is provided, the system comprising: a user equipment (UE) in a frame based equipment (FBE) mode; and a gNB in communication with the UE. The UE is configured to perform: determining that a communication channel in an unlicensed spectrum is available; and transmitting, to the gNB in the communication channel, a first transmission within a fixed frame period (FFP) associated with the UE to initiate, by the UE, a first channel occupancy time (COT) within the FFP, the first transmission starting at a beginning of the FFP and ending before an idle period within the FFP. The gNB is configured to perform: receiving, from the UE in the communication channel of the unlicensed spectrum, the first transmission within the FFP; and determining, based on the first transmission, that the UE initiates the first COT within the FFP in response to the first transmission starting at the beginning of the FFP and ending before the idle period of the FFP.

[0069] According to another embodiment of the disclosure, an apparatus is provided, the apparatus comprising: a non-transitory memory storage comprising instructions; one or more processors in communication with the memory storage, wherein the instructions, when executed by the one or more processors, cause the apparatus to perform the method of any of the above aspects.

[0070] According to another embodiment of the disclosure, a non-transitory computer-readable medium storing computer instructions that, when executed by one or more processors of an apparatus, cause the apparatus to perform the method of any of the above aspects.

[0071] The above aspects of the disclosure facilitate communications in an unlicensed spectrum by a UE in an FBE mode while reducing transmission latency, overhead, and battery power consumption. BRIEF DESCRIPTION OF DRAWINGS

[0072] For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings in which:

[0073] Figure 1 is a schematic diagram of an embodiment wireless communication network;

[0074] Figure 2 is an example communication system, providing mathematical expressions for signals transmitted in the communication system;

[0075] Figure 3A and Figure 3B is a schematic diagram of a legacy system for analog beam steering and digital beamforming;

[0076] Figure 4 is a schematic diagram of example legacy transmission timing for frame based equipment (FBE) operation;

[0077] Figure 5 is a schematic diagram of a legacy carrier sense method;

[0078] Figure 6 is a schematic diagram of a legacy listen before talk method;

[0079] Figure 7 is a schematic diagram of an example legacy Wi-Fi channel access procedure;

[0080] Figure 8A is a schematic diagram of an example wide beam pattern;

[0081] Figure 8B is a schematic diagram of an example narrow beam pattern;

[0082] Figure 9 is a schematic diagram of example operation timing in a load based equipment (LBE) mode;

[0083] Figure 10 is a schematic diagram of example operation timing in an FBE mode;

[0084] Figure 11 is a schematic diagram of example UE operation timing, highlighting a CCA backoff procedure;

[0085] Figure 12 is a schematic diagram of example UE operation timing, highlighting a time interval T UE COT allocated for a group of UEs and confirmation of a UE initiated COT;

[0086] Figure 13 is a schematic diagram of example UE operation timing, highlighting a periodic COT allocated by a gNB;

[0087] Figure 14 is a schematic diagram of example gNB and UE operation timing, highlighting initiation of a COT by both the gNB and the UE;

[0088] Figure 15 is a flowchart of example UE operation for requesting a new UE COT;

[0089] Figure 16 is an embodiment semi-static channel access configuration information element (IE);

[0090] Figure 17 is a flowchart of embodiment UE and gNB operations for COT switching;

[0091] Figure 18 is a schematic diagram of embodiment gNB-initiated COT and UE-initiated COT, highlighting COT overlap;

[0092] Figure 19 is a flowchart of embodiment UE and gNB operations for channel access, highlighting dynamic COT change;

[0093] Figure 20 is a flowchart of embodiment UE and gNB operations for channel access, highlighting validation of UE COT initiation;

[0094] Figure 21 is a schematic diagram of embodiment gNB-initiated COT and UE-initiated COT, highlighting non-overlapping COTs occupying a channel;

[0095] Figure 22 is a flowchart of one embodiment method for UE COT initiation;

[0096] Figure 23 is a flowchart of another embodiment method for UE COT initiation;

[0097] Figure 24 is a schematic diagram of an embodiment processing system;

[0098] Figure 25 is a schematic diagram of an embodiment transceiver;

[0099] Figure 26 is a schematic diagram of embodiment gNB and UE operations.

[0100] Corresponding numbers and symbols in different figures generally refer to corresponding parts unless context dictates otherwise. The figures are drawn for clarity of understanding and can not be to scale. DETAILED DESCRIPTION

[0101] The making and using of the embodiments of the disclosure will now be discussed in detail. It should be understood, however, that the concepts disclosed herein can be embodied in many specific contexts and the specific embodiments discussed herein are merely illustrative and not used to limit the scope of the claims. Furthermore, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the disclosure as defined by the appended claims.

[0102] Communications in unlicensed spectrum use listen before talk (LBT) channel access. A transmitter performs a clear channel assessment (CCA) to determine if a channel is available for transmission. If the channel is assessed as available, the transmitter can transmit for the duration of a channel occupancy time (COT). A COT is a duration of time in which a communication device (e.g., a user equipment (UE) or a gNB) can transmit on a given channel without needing to reassess the availability of the channel. During a COT, a communication device can have multiple transmissions, and can allow other communication devices to share the COT (i.e., transmit during a shared COT). Traditionally, only a gNB can initiate a COT (i.e., the gNB is the first device to transmit within the COT), and the gNB can share the COT with UEs. A UE in a frame based equipment (FBE) mode of operation cannot initiate a COT, and needs to use a COT shared by a gNB for transmission. A gNB can schedule an uplink grant for a UE uplink transmission within a gNB initiated COT.

[0103] The restriction that only a gNB can initiate a COT can result in unnecessary delay and overhead for UL transmissions. As one example, a UE with UL data to transmit can have to wait until a gNB scheduled COT starts. When the UE has no data to transmit, the UE still needs to listen to every scheduled COT, which results in UE battery power and RF spectrum waste.

[0104] Various embodiments of the present disclosure provide a method for UE initiated COT in FBE mode of operation. In some embodiments, a UE in FBE mode can determine that a communication channel in unlicensed spectrum is available, and transmit a transmission to a gNB in the communication channel within a fixed frame period (FFP) associated with the UE to initiate a channel occupancy time (COT) by the UE within the FFP. The transmission starts at the beginning of the FFP and ends before an idle period within the FFP. The gNB receives the transmission and determines that the UE has initiated the COT based on the reception of the transmission. That is, the UE is the first device to transmit within the COT. The gNB can confirm or reject the initiation of the COT by the UE. If the gNB does not reject the initiation, the UE can continue to communicate with the gNB within the UE initiated COT. The UE does not need to reassess channel availability within the UE initiated COT. Thus, when the UE has uplink data to transmit, the UE does not need to wait for a shared gNB initiated COT to transmit the uplink data within the gNB initiated COT. The UE can initiate the COT by itself for transmitting the uplink data. These embodiments facilitate a UE in FBE mode to communicate in unlicensed spectrum while reducing latency, overhead, and battery power consumption.

[0105] Figure 1An example wireless communication system 100 is shown. The communication system 100 includes an access node 110 having a coverage area 111. The access node 110 serves a number of user equipments (UEs), including UE 120 and UE 122. Transmissions from the access node 110 to the UEs are called downlink (DL) transmissions and occur on the downlink channel (shown in solid lines with arrows in Figure 1 ); transmissions from the UEs to the access node 110 are called uplink (UL) transmissions and occur on the uplink channel (shown in dashed lines with arrows in Figure 1 ). Service can be provided to the UEs by a service provider connected to the access node 110 through a backhaul network 130 (e.g., the Internet). The wireless communication system 100 can include multiple distributed access nodes 110.

[0106] In a typical communication system, there are several modes of operation. In a cellular mode of operation, communications to and from multiple UEs go through the access node 110, while in a device-to-device mode of communication, such as in a proximity service (ProSe) mode of operation, UEs can communicate directly with each other. An access node can also be commonly referred to as a NodeB, an evolved Node B (eNB), a next generation (NG) Node B (gNB), a master eNB (MeNB), a secondary eNB (SeNB), a master gNB (MgNB), a secondary gNB (SgNB), a network controller, a controlling node, a base station, an access point, a transmission point (TP), a transmission-reception point (TRP), a cell, a carrier, a macro cell, a femto cell, a pico cell, a relay, a customer premises equipment (CPE), etc. A UE can also be commonly referred to as a mobile station, a mobile device, a terminal, a terminal device, a user, a subscriber, a station, a communication device, a CPE, a relay station, an Integrated Access and Backhaul (IAB) relay, etc. It should be noted that when relaying (based on a relay station, a pico base station, a CPE, etc.) is used, especially multi-hop relaying, the boundary between a controller and a node controlled by the controller can become blurred, and in a two-node (controller or node controlled by the controller) deployment, the first node that provides configuration or control information to the second node is considered the controller. Likewise, the concepts of UL and DL transmissions can also be extended.

[0107] A cell can include one or more bandwidth parts (BWPs) allocated for a UE for UL or DL. Each BWP can have its own BWP-specific system parameters and configurations. It should be noted that all BWPs do not need to be activated for a UE at the same time. A cell can correspond to one or more carriers. Typically, one cell (e.g., a primary cell (PCell) or a secondary cell (SCell)) is a component carrier (e.g., a primary component carrier (PCC) or a secondary CC (SCC)). For some cells, each cell can include multiple carriers in the UL, one carrier referred to as a UL carrier or a non-supplementary UL (non-SUL) carrier, which has an associated DL; while the other carriers are referred to as supplementary UL (SUL) carriers, which do not have an associated DL. A cell or carrier can be configured with a slot or subframe format consisting of DL and UL symbols, and the cell or carrier is considered to be operating in a time division duplexed (TDD) mode. Typically, for non-paired spectrum, a cell or carrier is in TDD mode, while for paired spectrum, a cell or carrier is in frequency division duplexed (FDD) mode. An access node can provide wireless access according to one or more wireless communication protocols, e.g., long term evolution (LTE), LTE Advanced (LTE-A), 5G, 5G LTE, 5G NR, High Speed Packet Access (HSPA), Wi-Fi 802.11a / b / g / n / ac, etc. While it can be understood that a communication system can employ multiple access nodes capable of communicating with multiple UEs, for simplicity, only one access node and two UEs are shown.

[0108] Figure 2 An example communication system 200 is shown, providing mathematical expressions for signals transmitted in the communication system 200. The communication system 200 includes an access node 205 in communication with a UE 210. As Figure 2As shown, the access node 205 uses a transmit filter v and the UE 210 uses a receive filter w. Both the access node 205 and the UE 210 use linear precoding or combining. Assume that the channel matrix (or channel model or channel response) H is an N rx x N tx matrix, i.e., there are N tx transmit antennas and N rx receive antennas. The transmit filter v is of dimension N tx x Ns, where Ns is the number of transmitted layers, ports, streams, symbols, pilots, messages, data, or known sequences. The receive filter w of a multi-antenna system is of dimension N rx x Ns, representing a combining matrix, which is usually applied to the received signal y according to w H y. The above description is for a transmission from the access node 205 to the UE 210, i.e., a DL transmission. Transmissions can also occur in the opposite direction (i.e., UL transmissions), for which, in the case of TDD, the channel matrix becomes H H (wherewith H is the Hermitian matrix of the channel model H), w can be seen as a transmit filter and v as a receiver filter. w for transmission and w for reception can be the same or different; the same is true for v.

[0109] The DL (or forward) channel 215 between the access node 205 and the UE 210 has a channel model or response H, while the UL (or reverse, or inverse) channel 220 between the UE 210 and the access node 205 has a channel model or response H H .(Another convention is that the UL channel is denoted as H T , H T being the transpose of the channel model H). Although Figure 2 only one access node and one UE are described, the communication system 200 is not limited to this case. Multiple UEs can be served by the access node on different time-frequency resources (such as in a frequency division multiplexed-time division multiplexed (FDM-TDM) communication system, as in a typical cellular system) or on the same time-frequency resources (such as in a multi-user MIMO (MU-MIMO) communication system, where multiple UEs are paired and the transmission to each UE is precoded individually). In paired UEs, there is intra-cell interference.

[0110] In addition, there can be multiple access nodes in the network, some of which can cooperatively serve UE 210 in a joint transmission manner (such as coherent joint transmission, non-coherent joint transmission, coordinated multipoint transmission, etc.), a dynamic point switching manner, etc. Some other access nodes can not serve UE 210, and their transmissions to their own UEs cause inter-cell interference to UE 210. The scenario of multiple access nodes and multiple UEs (in which access nodes cooperatively serve UEs and utilize MU-MIMO) is an example scenario considered herein.

[0111] One way to increase network resources can be to utilize more and more available spectrum resources, including not only licensed spectrum resources of the same type as macro, but also licensed spectrum resources of different types than macro (e.g., macro is an FDD cell, but small cells can use FDD and TDD carriers simultaneously), as well as unlicensed spectrum and shared licensed spectrum; and, some spectrum resources can be located in high frequency bands, such as 6 GHz to 60 GHz. Unlicensed spectrum is generally available for use by any user, but subject to regulatory requirements. Shared licensed spectrum can also not be exclusive to an operator. Traditionally, cellular networks do not use unlicensed spectrum because quality of service (QoS) requirements are generally difficult to guarantee. Operating on unlicensed spectrum is primarily done by wireless local area networks (WLANs), such as Wi-Fi networks. Due to the fact that licensed spectrum is generally scarce and expensive, cellular operators can consider using unlicensed spectrum. It should be noted that on high frequency bands and unlicensed / shared licensed bands, TDD is generally used, so channel reciprocity can be utilized for communication.

[0112] On unlicensed spectrum, there is generally no pre-coordination between multiple nodes operating on the same frequency resource. Therefore, a contention-based protocol (CBP) can be used. According to Section 90.7 of Part 90 (Section 58) of the Federal Communication Commission (FCC), CBP is defined as:

[0113] “A protocol that allows multiple users to share the same spectrum by defining the events that must occur when two or more transmitters attempt to access the same channel at the same time, and establishing rules for transmitters to provide reasonable operating opportunities for other transmitters. Such a protocol can include procedures for initiating new transmissions, procedures for determining the status of a channel (available or unavailable), and procedures for managing retransmissions in the case of a busy channel.”

[0114] It should be noted that the channel busy state can also be referred to as channel not available, channel not idle, channel occupied, etc., and the channel idle state can also be referred to as channel available, channel idle, channel not occupied, etc.

[0115] One of the most commonly used CBPs is the "Listen Before Talk" (LBT) operating procedure in IEEE 802.11 or Wi-Fi (e.g., found in "Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications," IEEE Std 802.11-2007 (revision of IEEE Std 802.11-1999), which is incorporated by reference herein in its entirety). One method of implementing Listen Before Talk (LBT) is to use the carrier sense multiple access with collision avoidance (CSMA / CA) protocol. According to the CSMA / CA protocol, carrier sensing is performed prior to any transmission attempt, and transmission is only made if the carrier is sensed to be idle; otherwise, if the carrier is busy, a random back-off time is applied for the next sensing. Carrier sensing is usually done through a CCA procedure to determine whether the power within the channel is below a given threshold.

[0116] ETSI EN 301 893 V2.1.1 (incorporated by reference herein in its entirety), clause 4.9.2, describes two (2) types of adaptive devices: frame-based devices and load-based devices, where the following is specified (quoted from clause 4.9.2 of ETSI EN 301 893 V2.1.1).

[0117] "A frame-based device shall comply with the following requirements:

[0118] 1) Before starting a transmission on the operating channel, the device shall perform a clear channel assessment (CCA) check using "energy detection". The device shall observe the operating channel for the duration of the CCA observation time, which shall be no less than 20 μβ. The CCA observation time used by the device shall be declared by the manufacturer. The operating channel is considered occupied if the energy level in the channel exceeds the threshold corresponding to the power level given in point 5 below. If the device finds the operating channel to be idle, it can immediately proceed with the transmission (see point 3 below).

[0119] 2) If the device finds the operating channel to be occupied, it shall not transmit on that channel during the next fixed frame period.

[0120] NOTE 1: A device is allowed to continue short control signaling transmission on the channel, provided it meets the requirements in clause 4.9.2.3.

[0121] NOTE 2: For devices transmitting simultaneously on multiple (adjacent or non-adjacent) operating channels, the device is allowed to continue transmission on the other operating channels as long as CCA check does not detect any signal on those channels.

[0122] 3) The total time during which a device transmits on a given channel without re-evaluating the availability of the channel is defined as channel occupancy time. Channel occupancy time shall be in the range of 1 ms to 10 ms, and the minimum idle period shall be at least 5% of the channel occupancy time used by the device for the current fixed frame period. At the end of the idle period, the device shall perform a new CCA as described in point 1 above.

[0123] 4) A device can skip CCA and immediately (see NOTE 3) continue transmission of management and control frames (e.g., ACK and Block ACK frames) upon correct reception of a data packet addressed to the device. The consecutive sequence of such transmissions by a device without performing a new CCA shall not exceed the maximum channel occupancy time as defined in point 3 above.

[0124] NOTE 3: For the purpose of multicasting, ACK transmissions by individual devices (associated with the same data packet) are allowed in sequence.

[0125] 5) The energy detection threshold of CCA shall be proportional to the maximum transmit power (PH) of the transmitter: for a 23 dBm effective isotropically radiated power (e.i.r.p.) transmitter, the CCA threshold level (TL) shall be equal to or lower than –73 dBm / MHz at the input of the receiver (assuming 0 dBi receive antenna). For other transmit power levels, the CCA threshold level TL shall be calculated using the following formula: TL = –73 dBm / MHz + 23 – PH (assuming zero (0) dBi receive antenna and PH e.i.r.p. specified in dBm).”

[0126] “Load-based devices can implement the LBT-based spectrum sharing mechanism using the “energy detection” idle channel assessment (CCA) mode, as specified in clauses 9 and 17 of IEEE 802.11 TM -2007 [9], and clauses 9 and 17 of IEEE 802.11n TM- Clauses 9, 11 and 20 of IEEE Std 802.11-2016

[10] as described but with the compliance requirements mentioned in Clause 4.9.3 (see Note 1) to be respected (all these Clauses and requirements are incorporated herein by reference).

[0127] Note 1 : When such devices are available, it is also desirable to allow the use of an "energy detection" based Clear Channel Assessment (CCA) mode implementation as detailed in IEEE 802.11ac TM [i.2] Clauses 8, 9, 10 and 22 of IEEE Std 802.11-2016

[10] (these Clauses are incorporated herein by reference).

[0128] Load based devices not using any of the above mechanisms shall comply with the following set of minimum requirements:

[0129] (1) Before starting a transmission or a burst of transmissions on the operating channel, the device shall perform a Clear Channel Assessment (CCA) check using "energy detection". The device shall observe the operating channel for the duration of the CCA observation time, which shall be no less than 20 μβ. The CCA observation time used by the device shall be declared by the manufacturer. The operating channel is considered to be occupied if the energy level in the channel exceeds the threshold corresponding to the power level given in point 5 below. If the device finds the channel to be idle, it can proceed immediately to transmission (see point 3 below).

[0130] (2) If the device finds the operating channel to be occupied, it shall not proceed to transmission on that channel. The device shall perform an Extended CCA check in which the operating channel is observed for the duration of the CCA observation time multiplied by a random factor N. N defines the number of idle slots resulting in the total idle period to be observed before initiating a transmission. Whenever an Extended CCA is required, the value of N shall be randomly selected in the range 1... q and this value is stored in a counter. The value of q is selected by the manufacturer in the range 4... 32. This value shall be declared by the manufacturer (see Clause 5.3.1 q)). The counter is decremented each time a CCA slot is considered "unoccupied". When the counter reaches 0, the device can proceed to transmission.

[0131] Note 2: The device is allowed to continue a short control signaling transmission on that channel provided it complies with the requirements in Clause 4.9.2.3.

[0132] Note 3: For devices transmitting simultaneously on multiple (adjacent or non-adjacent) operating channels, the device is allowed to continue transmission on the other operating channels provided that the CCA check does not detect any signal on those channels.

[0133] 3) The total time the device uses the working channel is the maximum channel occupancy time, which should be less than (13 / 32)×q ms, where q is defined in point 2 above. After this time, the device should execute the extended CCA described in point 2 above.

[0134] 4) When a device correctly receives a data packet destined for it, it may skip the CCA and immediately (see Note 4) continue transmitting management and control frames (e.g., ACK and block ACK frames). Without executing a new CCA, the consecutive sequence of transmissions performed by the device should not exceed the maximum channel occupancy time defined in point 3 above.

[0135] Note 4: For multicast purposes, ACK transmissions (associated with the same data packet) from each device are allowed to occur sequentially.

[0136] 5) The CCA energy detection threshold should be proportional to the transmitter's maximum transmit power (PH): For a 23 dBm.irp transmitter, the CCA threshold level (TL) should be equal to or lower than –73 dBm / MHz at the receiver input (assuming a 0 dBi receiver antenna). For other transmit power levels, the CCA threshold level TL should be calculated using the following formula: TL = –73 dBm / MHz + 23 – PH (assuming a 0 dBi receiver antenna and PH eirp specified in dBm).

[0137] The above content is quoted from Clause 4.9.2 of ETSI EN 301 893 V2.1.1.

[0138] Figure 3A and Figure 3B These are block diagrams of conventional systems 300 and 350 used for analog beam control and digital beamforming. Figure 3A The system 300 shown includes a baseband assembly 302 for digital processing, multiple RF chain assemblies 304, multiple phase shifters 306, multiple combiners 308, and multiple antennas 310. The system 300 can be used for transmission or reception. For simplicity, Figure 3A The transmission is illustrated as an example; reception can be understood similarly. Each RF chain 304 receives weighting factors (or weights, p1...p1) from the baseband component 302. m ,like Figure 3A (As shown). The set of weighting factors forms the digital precoding vector, precoding matrix, beamforming vector, or beamforming matrix used for transmission. For example, the precoding vector could be [p1...p... m]. When multiple layers / streams are transmitted, the baseband component 302 can use a precoding matrix to generate the weighting factors, where each column (or row) of the matrix is applied to a layer / stream of the transmission. Each RF chain 304 is coupled to a number of phase shifters 306. In theory, the phase shifters 306 can apply any phase shift value, but in practice, typically only a few possible phase shift values are applied, e.g., 16 or 32 values. Each RF chain 304 generates a narrow beam 312, directed in a direction determined by the settings on the phase shifters 306 and the combiner 308. If the phase shifters 306 can apply any phase shift value, the beam can be pointed in any direction; however, if only a few phase shift values can be used, the beam can be one of a few possibilities (e.g., in Figure 3A In the middle, a narrow beam is selected by setting a particular phase shift value in the RF chain 304 (solid line), and this beam is among all possible narrow beams (shown in solid and dashed lines, corresponding to all possible phase shift values). Each RF chain selects such a narrow beam, and all the narrow beams selected by all the RF chains (RF chain 1-N) will be further superimposed. How the superimposition is done is based on the digital weighting factors. The weighting factors can make the beam from an RF chain stronger or weaker, and thus, a different set of factors can produce different superimpositions in the spatial domain; in Figure 3A In the middle, a narrow beam is selected by setting a particular phase shift value in the RF chain 304 (solid line), and this beam is among all possible narrow beams (shown in solid and dashed lines, corresponding to all possible phase shift values). Each RF chain selects such a narrow beam, and all the narrow beams selected by all the RF chains (RF chain 1-N) will be further superimposed. How the superimposition is done is based on the digital weighting factors. The weighting factors can make the beam from an RF chain stronger or weaker, and thus, a different set of factors can produce different superimpositions in the spatial domain; in

[0139] Figure 3B The illustrated system 350 is similar to the system 300 illustrated in Figure 3A except that the corresponding combiners 308 in each RF chain 304 are connected to each other.

[0140] An example of timing 400 for transmission by a frame-based device is illustrated in Figure 4 The device, e.g., a unit under test (UUT), performs CCA on the channel before transmission, and when the channel is free (or available, unoccupied), the device transmits during a channel occupancy time and enters an idle state for an idle period. During the idle period, the device performs CCA to determine whether the channel is available.

[0141] Figure 5 An example of a flowchart of an embodiment method 500 for carrier sensing is illustrated in Figure 5Method 500, as shown, begins at block 502, where the communication controller receives waveform signals from the UE. In block 504, the communication controller processes the signals and generates a decision variable X. The signal processing described herein is typically performed in the digital domain, usually in baseband, and may include sampling, analog-to-digital (A / D) conversion, pre-coding weighted digital combination by the receiver, etc. The decision variable X is used to determine whether the carrier channel is idle or busy. In block 506, the communication controller determines that the decision variable is less than a threshold T. This threshold can be a standardized value or a value derived according to a standard or some specification, and can be device-type specific, space-specific, etc. It may also be allowed that the threshold varies within a specified range based on traffic load, interference conditions, etc. If, in block 506, the communication controller determines that the value of the decision variable X is less than the threshold T, method 500 proceeds to block 508, where the communication controller determines that the carrier channel is idle, and then method 500 ends. If, in box 506, the communication controller determines that the value of decision variable X is not less than threshold T, then method 500 proceeds to box 510, where the communication controller determines that the carrier channel is busy, and then method 500 ends.

[0142] Figure 6 The diagram shows a flowchart of an embodiment method 600 for a traditional listen-before-speak mechanism. Figure 6 Method 600 begins at block 602, where the communication controller assembles frames. At block 604, the communication controller performs carrier sensing, as described in the reference above. Figure 5 The described carrier sensing is used to determine if the channel is idle. If, at box 604, the communication controller determines that the channel is not idle but busy, then method 600 proceeds to box 606, where the communication controller stops transmitting frames and waits for a random backoff timer to expire, and then method 600 returns to box 604. If, at box 604, the communication controller determines that the channel is idle, then method 600 proceeds to box 608, where the communication controller transmits frames, and then method 600 terminates.

[0143] Wi-Fi is a typical example of an application of the listen-before-talk mechanism. Wi-Fi uses 802.11 standard technology, such as air interface (including physical (PHY) and MAC layer). In 802.11, the communication channel (or called wireless channel) is shared by stations under a mechanism called distributed channel access, which has a function called DCF (distributed coordination function) that uses CSMA / CA. DCF uses physical and virtual carrier sensing functions to determine the status of the medium (i.e., the communication channel). Physical carrier sensing resides in the PHY and uses energy detection and preamble detection with frame length delay to determine when the medium is busy. Virtual carrier sensing resides in the MAC and uses reservation information carried in the Duration field of the MAC header that announces the blocking of the use of the wireless channel. The virtual carrier sensing mechanism is called network allocation vector (NAV). Only when both the physical and virtual carrier sensing mechanisms indicate that the wireless channel is idle, the wireless channel is determined to be idle. A station (e.g., STA1) with a data frame for transmission first performs CCA by listening to the wireless channel for a fixed duration (i.e., DCF inter-frame space (DIFS)). If the wireless channel is busy, the station waits until the channel becomes idle, defers DIFS, and then waits for a further random back-off period (by setting a back-off timer with an integer number of slots). For each idle slot, the back-off timer decreases by 1, and upon sensing that the channel is busy, the back-off timer freezes. When the back-off timer reaches 0, the station starts data transmission. Figure 7 The Wi-Fi channel access procedure 700 as described above is shown in FIG. 7.

[0144] To meet regulatory requirements for operating in unlicensed spectrum and coexistence with other radio access technologies (RATs) such as Wi-Fi, transmissions on unlicensed spectrum cannot be continuous or persistent in time. Instead, an on / off mechanism, or opportunistic transmission and measurement on demand, can be employed.

[0145] Furthermore, for operation typically in high frequency bands belonging to the mmWave regime (especially in the frequency bands of 28 GHz to 60 GHz), communications have very different propagation characteristics than communications in microwave frequency bands (typically below 6 GHz). For example, in terms of distance, mmWave experiences higher path loss than microwave. As a result, high frequency bands are more suitable for small cell operation than macro cell operation, and they typically rely on beamforming using a large number of antennas (e.g., more than 16 antennas, sometimes even several hundreds of antennas) for efficient transmission. It should be noted that at high frequencies, the wavelength, antenna size, and antenna spacing can all be smaller than at low frequencies, making it possible to equip nodes with a large number of antennas. As such, beams formed by a large number of antennas can be very narrow, e.g., with beam widths of 10 degrees or even less. In sharp contrast, in traditional wireless communications, beam widths are typically much wider, such as tens of degrees. Figure 8A A schematic diagram showing a wider beam pattern 802 using a small number of antennas in low frequencies is shown. Figure 8B A schematic diagram showing a narrow beam pattern 804 using a large number of antennas in high frequencies is shown. It is generally considered that narrow beams are a major new feature of mmWave. As a general rule of thumb, the beamforming gain obtained by a large MIMO can be roughly estimated by N x K, where N is the number of transmit antennas and K is the number of receive antennas. This is because the 2-norm of the channel matrix H roughly scales by (N x K) 1 / 2 ; thus, if the precoding vector of the transmitting node is p and the combining vector of the receiving node is w, the composite channel is w'Hp, and by choosing w and p appropriately, the composite channel energy gain can reach N x K, which is much higher than the case using fewer antennas.

[0146] The NR standard does not specify autonomous UE-triggered COT (i.e., not COT scheduled by gNB). The NR standard specifies gNB-initiated COT. During gNB-initiated COT, the UE can be allowed to transmit as a shared COT device (i.e., the UE shares the gNB-initiated COT for transmission). The gNB can configure the UE transmission including indicating the LBT type that the UE needs to use as a COT shared device during the gNB-initiated COT. The type of UL channel access (e.g., LBT) can be indicated by the gNB in the UL grant scheduling.

[0147] The LTE LAA and NR-U specifications define two types of operation for unlicensed channel access based on channel access timing synchronization, i.e., a Load Based Equipment (LBE) mode of operation and a Frame Based Equipment (FBE) mode of operation.

[0148] In the LBE mode of operation, unlicensed channel access is not synchronized to an external clock, and COT is initiated upon a successful CCA procedure. Figure 9A diagram showing example operation timing 900 in LBE mode is shown. After each COT 910 within a fixed frame period (FFP) 930, the gNB performs channel sensing (e.g., CCA) on a sensing slot 920 and, when the channel being sensed is perceived to be idle, the gNB starts a random backoff counter. The random backoff counter decrements for each sensing slot 922 when the channel is found to be idle. If during sensing, the channel is busy (e.g., in sensing slot 924), i.e., CCA fails, the backoff counter decrement is stopped.

[0149] Figure 10 A diagram showing operation timing 1000 in FBE mode according to TS 37.213 is shown. In FBE operation mode, the gNB performs LBT operation (e.g., extended CCA) on the channel (e.g., during an idle period) every time interval T (period). If the channel is found to be idle according to the LBT operation, the gNB can initiate a COT 1010 with duration Ty, which is a fraction of the repetition period (T). That is, the gNB is the device that first uses the COT for transmission. The COT 1010 is periodically initiated every fixed frame period (FFP) T in two consecutive radio frames, starting from the even indexed radio frame at x T, with maximum channel occupancy time Ty = 0.95 * T, where T is the FFP in ms, which is also referred to as frame and is a higher layer parameter, and x is an integer representing the number of periods (i.e., the number of FFPs). This type of access is referred to as semi-static channel occupancy in TS 37.213. Only the gNB can initiate a COT in FBE mode. As shown, each FFP includes a COT 1010 starting at the beginning of the FFP, followed by an idle period. The gNB performs CCA before the start of the next FFP, e.g., within the idle period of the current FFP. If the channel is found to be available (not occupied, or idle) based on the CCA, the gNB can initiate a COT 1010 within the next FFP. Figure 10

[0150] ​In FBE operation mode, information about FFP, such as the starting position of FFP and the duration of FFP, is provided to the UE by the gNB. If one or more DL signals / channels (e.g., physical downlink control channel (PDCCH), synchronization signal block (SSB), physical broadcast channel (PBCH), remaining minimum system information (RMSI), or configured grant (CG)-PDCCH) within the FFP are detected, UE transmission can be made within the FFP.

[0151] TS 37.213 defines a periodic COT (with periodicity T = FFP) triggered (initiated) by a gNB (as described above), and such periodic COT can be referred to herein as a first type of periodic COT. A COT can be referred to as a duration during which a channel is “owned” by an initiator that initiates the COT. During the COT, the initiator can have multiple transmissions, and can allow other devices (such as receivers) to share the COT, in a sense that the receivers can also make some transmissions. The initiator of a COT can be understood as the one that first starts transmission at the start of the FFP associated with the COT after verifying that the channel is idle, and the other devices sharing the COT can only make transmissions after the initiator initiates the COT and provides a grant for sharing the COT. In NR specifications Rel16 or earlier, a UE cannot be an initiator, and only a gNB can initiate a COT. That is, only after a COT is initiated by a gNB (the gNB starts transmission within the COT) and the gNB grants a UE permission to share the COT, the UE can use the COT. For example, a gNB can initiate a COT, perform a DL transmission, and schedule a UE to share the COT. The UE detects the DL transmission, and thereafter can perform UL transmission within the COT according to the schedule. During the COT, the LBT procedure performed can be different from the one performed outside the COT, and more specifically, LBT during the COT can be very short, and can use a deterministic periodicity to perform CCA, or no CCA (LBT) is needed if the interval between consecutive transmissions is shorter than a pre-set period (e.g., 16 µs).

[0152] Before initiating a COT in FBE mode, according to TS 37.213, the gNB must perform an extended CCA procedure, referred to as basic LBT in 3GPP, of category 4 LBT. This basic LBT procedure includes a truncated exponential backoff based on energy detection (ED). In this procedure, the gNB listens to the channel and, if the channel is detected as idle (i.e., low energy is detected on the channel), the gNB starts a random backoff counter, which is decremented each time the channel is detected as idle in a listening slot. When the random backoff counter reaches 0, the gNB can proceed and initiate the COT; otherwise, if the random backoff counter does not reach 0 before the COT expires, the gNB must skip the current transmission opportunity (i.e., current FFP) and wait for the next period to initiate the COT for transmission. The terms “transmission opportunity” and “opportunity” are used interchangeably throughout this disclosure.

[0153] As mentioned above, the restriction that only the gNB can initiate an FBE COT can result in unnecessary UL transmission delay or overhead. For example, if the UE is a security camera, where UL transmission is triggered by movement detection, the UE traffic in UL can be delayed by one FFP in the best case. In this case, the gNB can schedule a periodic COT and schedule UL grant to the UE even if the UE has no data transmission, if the channel is idle. This results in UE battery power and RF spectrum waste, since the UE needs to listen to every periodic COT.

[0154] If the UE can initiate an FBE COT, the above-mentioned problem can be avoided. Using the example above, if the UE camera can initiate an FBE COT, the UE camera can trigger a periodic COT immediately upon detecting movement and cancel the periodic COT when the video transmission ends or stops.

[0155] Various embodiments of the present disclosure provide a method for UE-initiated FBE COT that will reduce latency and overhead. When a UE has data to transmit, the UE does not need to wait until a gNB initiates a COT of a FFP and schedules / grants the UE to share the gNB-initiated COT, and then the UE transmits within the shared gNB-initiated COT. Instead, the UE can initiate a COT of a FFP by itself in order to transmit within the UE-initiated COT. In other words, the UE can detect whether a channel is idle before a FFP, and if the channel is idle, the UE can start transmitting at the beginning of the FFP to initiate a COT of the FFP. The UE is the first device to start transmitting within the FFP. The proposed embodiments define an additional type of periodic COT (semi-static channel access) initiated by a UE. In embodiments, a UE can be able to periodically initiate a COT associated with a FBE operating mode. For a COT initiated by a UE, the UE can be referred to as the initiator and owner of the COT, and only this initiating UE can grant transmissions during the UE COT. The UE can share the COT with other devices such as a gNB or another UE. A periodic COT is a COT that can be initiated periodically, e.g., every FFP within a configured time interval. In various embodiments of the present disclosure, a UE can initiate a single COT or a periodic COT.

[0156] In some embodiments, a second type of periodic COT initiated by a UE is provided. Within this type of COT, the gNB can provide a time interval T_UE_COT to the UE via a starting position and possibly an ending position when the UE can initiate a periodic COT. The time interval T_UE_COT indicates an interval during which the UE is allowed to initiate a COT or a periodic COT. The time interval T_UE_COT can be indicated using a starting position of the time interval and an ending position of the time interval or other ways. For example, the starting position and the ending position of the time interval can be represented or indicated in frame index or via signaling in number of frames. The gNB can also provide a configuration of the FFP (also referred to as FFP configuration) to the UE initiating the COT. The FFP can also be referred to as “period” throughout this disclosure. The FFP configuration can include a FFP value, e.g., indicating a length (duration) of the FFP. If no FFP value is provided, the UE can consider, for example, the last FFP value used by the serving cell / gNB. There is an opportunity for the UE to initiate a COT at the start of each FFP. This opportunity is referred to herein as a COT opportunity, or, for a periodic COT, a periodic COT opportunity. If the UE does not take the opportunity to initiate a COT, the UE misses the COT opportunity and needs to wait for the next COT opportunity to initiate a COT. As will be discussed below, a UE initiating a COT of a current FFP can perform an uplink transmission in the COT opportunity of the current FFP, i.e., at the start of the current FFP. The UE can then own the COT of the current FFP and perform transmissions within the COT of the current FFP initiated by the UE. If the UE does not initiate the COT of the current FFP, the UE can use the same mechanism to initiate a COT for the next FFP or another FFP in the future.

[0157] These embodiments are different from a buffer status report (BSR) where the UE sends a scheduling request (SR) and the gNB allocates resources for UL transmission. For a BSR, a transmission opportunity needs to be scheduled within a COT that should be initiated by the gNB, and the UE never has the “ownership” of the COT. In embodiments, the gNB does not need to initiate a COT. For example, the UE can initiate and own a COT that can be shared with the gNB.

[0158] Various embodiments of the present disclosure also provide a scheme that allows multiple UEs to contend and initiate a COT during FBE operation. The gNB can confirm a “winner” of the contending UEs as the owner of the COT.

[0159] In some embodiments, the gNB can allocate a time interval T_UE_COT for UE initiated COT to a single UE or a group of UEs (as Figure 12The time interval T UE COT for UE initiated COT can be assigned to a single UE. During this time interval T UE COT, the UE can initiate a periodic COT immediately after a successful extended CCA (e.g., LBT Category 4) procedure. The periodicity (FFP) of the periodic COT can be provided by the gNB. The LBT type of the LBT to be performed by the UE can be provided by the gNB, or, for example, the UE can use a Type 1 LBT by default, or use a short time deterministic LBT for channel sensing. In different embodiments, the LBT type and periodicity (FFP) can be obtained by the UE from higher layer configuration.

[0160] The periodicity (FFP) of the UE initiated COT can be configured or preconfigured. The periodicity (FFP) of the UE initiated COT can be provided by the gNB. The possible values of the FFP can be the same or different from the FFP (periodicity) of the gNB (initiated) COT. In some embodiments, a FFP value can be provided for a single COT, which can correspond to an equivalent infinite periodic duration. LBT can still be required or performed within the infinite periodic duration of the transmission. In another embodiment, the FFP configuration can indicate that only a short COT for short control signal transmission can be initiated. A short COT would not require LBT in accordance with the short control signal transmission specified in the ETSI specification (e.g., ETSI EN 301 893 V2.1.1 (2017-05)). In some embodiments, the periodicity of the UE initiated COT can be the same as the DL FFP for the gNB, or always the same periodicity for a single COT, or a fixed value whether as a desired operation or before providing RRC. The configured periodicity of the UE initiated COT or the periodicity known by other means can be overwritten by the UE informing a “skip” or a “new periodicity” where the “new periodicity” value is for one or more initiated COTs or some small or limited number of allowed or configured values. The transmission made within the COT can be considered as a buffer status report from the UE, but at a more physical level.

[0161] By default, the FFP value can be different (e.g., single or infinite periodicity) for certain traffic types (e.g., infrequent alarms). The FFP configuration can also indicate that the UE works in the gNB initiated COT mode, where the UE has to use the gNB FFP configuration. That is, the UE can use the gNB initiated COT for transmission according to the corresponding gNB FFP configuration. In some embodiments, the UE can be instructed to switch between transmission using the UE initiated COT and transmission using the gNB initiated COT.

[0162] In some embodiments, the time interval T UE COT can be divided into periods (FFP), and these periods can be determined (configured) by the gNB or higher layers. For example, the time interval T UE COT can include a number of FFPs, and the number of FFPs can be determined by the network. At the start of each period, the UE can choose to trigger or choose not to trigger the FFP’s COT or periodic COT. To choose to trigger (i.e., determine to trigger or initiate a UE COT or UE periodic COT during the FFP), the UE will first do LBT, and if LBT is successful, the UE will do its transmission within the COT of the FFP. To choose not to trigger, the UE can skip LBT and do a very short UL transmission to inform it will skip the opportunity to initiate a COT or periodic COT. The short UL transmission can be a UL skip message, which can be simply a predefined simple sequence for more robustness.

[0163] If the UE skips an opportunity in the time interval T UE COT, it can use the next opportunity to initiate a COT within the time interval T UE COT, unless the gNB disallows the UE to do so, e.g., through a specific message. In this case, the gNB can take over the remaining T UE COT.

[0164] Once the UE does an UL transmission (e.g., PUCCH, PUSCH, SR, or SRS) after a successful LBT procedure, the COT can be a UE-initiated COT, where the LBT procedure is successful before the start of the FFP. That is, when the UE performs an UL transmission within the FFP associated with the COT, the UE can initiate the COT. The UL transmission can start at the start of the FFP (or at the start of the COT opportunity within the FFP) and end before the idle period of the FFP. The UL transmission of the UE that transmits in the uplink for initiating the COT can be referred to as the first transmission of the UE in the COT (opportunity). Other transmissions in the COT will be after the first transmission and end before the idle period of the FFP. A gNB that detects the first transmission can determine that the UE initiates the COT of the FFP. The frequency resources for the UL transmission can be provided by the gNB in advance, or the gNB can detect the cyclic shift in the RACH detection. The UL transmission can include, for example, PUCCH, PUSCH, scheduling request (SR), sounding reference signal (SRS), or channel state information (CSI) such as channel quality indicator (CQI). The UL transmission can be sent in some predetermined resources. In one embodiment, the UE can use the entire channel or a subset of the carrier to initiate the COT. If a subset of the carrier is used, the gNB can need to perform scheduling for the UE so that the minimum channel bandwidth occupancy requirement is met.

[0165] In one embodiment, the UE can inform the gNB whether it is ready to use the next FFP or skip the next FFP. For example, the UE can be allowed to initiate a number of COTs within the T_UE_COT time interval. The UE can inform the gNB that it will skip a certain number or all of the COT opportunities in T_UE_COT or initiate some or all of the COTs within the T_UE_COT interval. This information enables the gNB to reuse the unused UE-initiated COT opportunities, which can be allocated to another UE or used for a different type of traffic.

[0166] In some embodiments, the gNB can allocate a time interval T_UE_COT to a group of UEs. In this case, T_UE_COT is a time interval during which the group of UEs is allowed to initiate COTs. In this case, the group of UEs compete to initiate COTs within the FFP. To avoid collisions among multiple UEs that have passed the successful LBT category 4 (extended CCA) before the periodic COT opportunity, an additional backoff procedure is performed immediately after the initial LBT as part of the COT start (initiation) procedure. That is, each UE performs a COT initiation procedure in the periodic COT opportunity within T_UE_COT. In the COT initiation procedure, each UE performs a CCA to detect whether the channel is idle. If the channel is idle, the UE can immediately perform an additional backoff procedure. In this additional backoff procedure (also referred to as a CCA post-backoff procedure), each UE that has passed the LBT generates a random backoff counter R and continues to listen to the channel. The backoff counter is decremented at each listening slot when the channel listening is idle. When R = 0, the UE can initiate the COT. The initial value of the backoff counter R for each UE can be provided by the gNB, configured by higher layers, or a pre-defined default number. In one example, the backoff initial value for the backoff counter R for each UE can be proportional to the number of UEs in the group in order to reduce the collision opportunity.

[0167] It should be noted that in Internet of things (IoT) applications, the UL traffic can be uneven and triggered by on-site events or measurements. In this case, the additional backoff period at the start of the COT opportunity (start of the FFP), which can last for a few symbols, is not expected to impact the throughput during the COT, which can be a few milliseconds.

[0168] In one embodiment, the gNB can provide a random counter initial range (e.g., contention window, CW) for each UE while some UEs can be given more priority (shorter CW). For example, each of the group of UEs can be configured with a CW. One or more UEs can have higher priority (e.g., with shorter CW) than other UEs (with longer CW). In different embodiments, each UE can use a backoff counter initial range based on its traffic priority. For example, each UE can be configured with a backoff counter initial range based on its traffic priority.

[0169] Figure 11 A diagram illustrating an embodiment UE operation timing 1100 highlighting a CCA backoff procedure is shown. In this example, a group of UEs is configured to initiate periodic COTs for each COT opportunity using the CCA backoff procedure. The UEs in the group can perform transmissions for a first COT opportunity within a UE-initiated COT 1102. After the COT 1102 expires, the UEs can enter an idle period 1104 and then perform a CCA (in time region 1106) before the start of the next (second) COT opportunity. When the CCA is successful, the UEs can start an additional backoff procedure and continue to listen to the channel. The random backoff counter starts from an initial value. If the channel is listened to as idle during the additional backoff procedure, i.e., the random backoff counter decreases to 0 (in time region 1108), the UEs can initiate a COT 1110 for the second COT opportunity, e.g., by transmitting UL transmissions in the second COT opportunity, and continue to perform transmissions within the initiated COT 1110. The UEs stop their transmissions when they enter an idle period 1112 after the end of the COT 1110 and perform a CCA in time region 1114 to determine whether they can initiate a COT 1116 for the next (third) COT opportunity. If the CCA fails, the UEs can cancel the third COT opportunity. That is, the UEs skip the third COT opportunity for transmissions. The UEs can perform a CCA before the next (fourth) COT opportunity (in time region 1118) and the CCA can be successful. In this case, the UEs can start an additional backoff procedure and continue to listen to the channel in time region 1120. If the channel is listened to as busy in the listening slot during the additional backoff procedure, the additional backoff procedure fails. In this case, the UEs will not be able to initiate a COT 1122 in the fourth COT opportunity, thus canceling the fourth COT opportunity. The above operations can be performed by each UE in the group.

[0170] In some embodiments, after a successful UL transmission from a UE that initiates a COT, the COT that has been started or initiated can be acknowledged (ACKed) by the gNB via a DL transmission (e.g., a PDCCH scheduling a UL grant for the UE, or a hybrid automatic repeat request acknowledgement (HARQ ACK) to the first UL transmission). For example, a UE can send a UL transmission to the gNB to initiate a COT within a FFP. The gNB can successfully receive the UL transmission and send a DL transmission to the UE to acknowledge or confirm the initiation of the COT by the UE. It should be noted that if multiple UEs are allowed to contend to initiate a COT, each UE can have a different time advance (TA) for the UL transmission, while still being synchronized to the gNB via the gNB’s primary synchronization signal / secondary synchronization signal (PSS / SSS).

[0171] In another embodiment, the first transmission by each UE (i.e., the UL transmission to initiate or start a COT) can be scrambled with a UE-specific code, such that if two or more UEs send UL transmissions at the same time, the UL transmissions can be decoded by the gNB. In one embodiment, only one UE COT can be retained and ACKed by the gNB. That is, the gNB can select one of the UEs that sent a UL transmission as the owner of the COT, and ACK or acknowledge the selected UE initiating the COT. The ACK can be unicast to the single UE, or it can be multicast, e.g., identifying the UE COT owner via a sequence. In the case of unicast, downlink control information (DCI) scrambled with a radio network temporary identifier (RNTI) can be used. In the case of multicast, DCI scrambled with a group RNTI or group common DCI can be used, and the content of the DCI includes the identification of the UE COT owner, e.g., through a sequence encoded in a field of the DCI.

[0172] In some embodiments, multiple UEs can share one COT initiated by the multiple UEs. The gNB can ACK the shared COT to the multiple UEs, and provide resource allocation for their transmissions in the feedback to each UE.

[0173] Figure 12A diagram illustrating an embodiment UE operation timing 1200 highlighting a time interval T UE COT allocated for a group of UEs and the acknowledgement of UE initiated COTs. In this example, the group of UEs is configured to be able to initiate periodic COTs for each COT opportunity during the time interval T UE COT. The UE can start performing an additional backoff procedure (in time region 1202) after CCA success and from the start of the COT opportunity (FFP start). If the channel is sensed to be idle during the additional backoff procedure, the UE can initiate a COT for the COT opportunity, e.g., by sending an UL transmission to the gNB in the COT opportunity (at the start of the FFP). However, unlike Figure 11 the example, the UE will wait for a response from the gNB after sending the UL transmission to the gNB, where the response from the gNB can acknowledge (acknowledge) or reject the UE initiated COT. In this example, the UE receives an acknowledgement (ACK) from the gNB acknowledging the initiation of the COT by the UE (in time region 1204). Thus, the UE becomes the owner of the COT and performs UL transmissions within the COT.

[0174] In another embodiment, when the gNB acknowledges the periodic UE initiated COT, the gNB can allocate several periodic COTs to the specific UE. In this case, the UE can not be required to start a backoff period after LBT success and the UE can start UL traffic in the pre-allocated resources immediately after the start of the COT. Figure 13 An example of this case is shown. Figure 13 A diagram illustrating an embodiment UE operation timing 1300 highlighting a periodic COT allocated by the gNB. The UE starts an additional backoff procedure as discussed above and initiates a COT 1304 upon success of this additional backoff procedure. The gNB acknowledges the initiation of the COT 1304 by the UE and also allocates periodic COTs 1306, 1308, and 1310 to the UE (in time region 1302). The UE receives an ACK from the gNB and performs UL transmissions within the COT 1304. After the ownership period of the COT 1304 expires, the UE can initiate the periodic COTs 1306, 1308, and 1310 as indicated by the gNB. For the COTs 1306, 1308, and 1310, the UE can only need to perform CCA before each COT. If the CCA before the COT is successful, the UE performs transmissions within the COT without the need to perform an additional backoff procedure.

[0175] In some embodiments, a third type of periodic COT is provided. Within the third type of periodic COT, both the UE and the gNB can initiate the COT. In one embodiment, prior to the COT, the idle and CCA periods can be mandatory as specified by the specification and described above. The gNB can have a higher priority to initiate the COT, and if the channel is found to be idle, the gNB can initiate the COT immediately after the CCA period. The UE can have a lower priority to initiate the COT, and thus can continue to perform the backoff procedure during which a random counter is decremented for each listening slot when the channel is idle. To ensure no collision between the gNB transmission and the UE transmission, a UE contention window (CW) can be configured and can have a minimum value greater than 0. The third type of periodic COT can be initiated during a time period (e.g., T UE COT) and can be pre-configured by the gNB so that the UE or subset of UEs that can initiate the periodic COT know the time period in advance.

[0176] Figure 14 A diagram illustrating an embodiment gNB and UE operation timing 1400 is shown, highlighting the initiation of the COT by both the gNB and the UE. Figure 14 An embodiment for initiating the third type of COT is shown, where the gNB has a higher priority to initiate the COT than the UE. In this example, the UE and the gNB compete to periodically initiate the COT within a time interval T UE COT. Both the UE and the gNB can perform CCA prior to the COT 1404 (in time region 1402). When the UE’s CCA is successful, the UE can perform a backoff procedure, similar to the additional backoff procedure discussed above. If the UE’s backoff procedure fails, i.e., the channel is heard to be busy in a listening slot and the random counter has not reached 0, the gNB can initiate the COT 1404 (e.g., by sending a DL transmission) and become the owner of the COT 1404. In this case, the COT 1404 is a gNB initiated COT. Prior to the next COT 1412, both the UE and the gNB perform CCA (in time region 1406). The UE can have a successful CCA and backoff procedure (1408) and then send a UL transmission to the gNB to initiate the COT 1412. Once the UE receives an ACK (1410) from the gNB acknowledging the initiation of the COT 1412 by the UE, the UE becomes the owner of the COT 1412 and the COT 1412 is a UE initiated COT. If the gNB rejects the initiation of the COT 1412 by the UE, the gNB can own the COT 1412.

[0177] In one embodiment, the gNB can allow the UE to have zero backoff duration before starting the COT. The gNB can confirm the UE transmission and the COT, for example, using a HARQ-ACK message to the UE, or can cancel the UE COT transmission via a HARQ-NACK message, and take over the COT ownership.

[0178] In some embodiments, within all UE-initiated COTs, the gNB can take over any periodic COT, cancel any periodic COT, or change any periodic COT from UE-initiated to gNB-initiated COT. The gNB can also change the periodicity and duration of the COT, for example, by sending control signaling to the UE. To achieve this, the gNB can request COT interruption or cancellation or change in various ways, for example, by adding a field to the HARQ ACK-NACK message, or adding a field in the DCI. The gNB that requests COT interruption or cancellation or change can also do so in a slower way through a MAC CE or RRC message.

[0179] In some embodiments, the gNB can specify a subset of time intervals (e.g., a pattern) or a pattern of opportunities for the UE to initiate or trigger a COT. For example, the UE can be allowed to initiate a COT only in odd / even frames (FFP), UL / DL transmission periods, or within UL transmission periods. The time opportunities to initiate a COT or a periodic COT can be provided by the base station, configured by higher layers, or predefined. For example, the opportunities can be assigned to the UE based on the UE category or UE capability. By assigning a pattern of opportunities within T_UE_COT, the gNB can allow multiple UEs to share (i.e., initiate / trigger COT) within the same T_UE_COT duration.

[0180] In some embodiments, the configuration of COT or periodic COT for a UE can also be referred to as FFP configuration in this disclosure, can be performed by a gNB and transmitted to a UE, or can be pre-configured to a UE and reconfigurable. The FFP configuration for UE-initiated COT can be different or the same as the FFP configuration for gNB-initiated COT. As one example, a gNB communicates with a set of UEs configured by the gNB for COT initiation. A UE can first perform CCA-based channel sensing, and after CCA success, the UE can transmit (UL transmission) to the gNB in uplink to initiate a COT based on the configuration of uplink transmission from the gNB and the configuration of the COT. After detecting the corresponding uplink transmission from the UE, the gNB can determine that the COT is a UE-initiated COT and determine the follow-up / next action it is to take based on the detected UE-initiated COT and its own status. The action to be taken by the gNB can include confirming the COT initiated by the UE, or indicating to the UE to share within a gNB-initiated COT, or indicating to the UE to share within a different UE-initiated COT. The corresponding indication from the gNB can be sent in downlink control information (DCI) in PDCCH. The indication can include information of the COT (also referred to as COT information, COT parameters, or COT parameters for FFP), such as periodicity of the FFP (also periodicity of the COT opportunity), MCOT within the FFP, time offset of the FFP, minimum idle duration within the FFP, maximum idle duration within the FFP, channel, bandwidth, or a combination thereof. FFP is the length (or duration, or periodicity) of the fixed frame period, MCOT is the maximum allowed COT duration within the periodicity (FFP), minimum and maximum idle durations are the minimum and maximum durations of idle period (no transmission) within the FFP, respectively, and channel and bandwidth represent the frequency resources for transmission within the COT. The configuration of COT or periodic COT that can be initiated by a UE or a gNB can include the COT parameters as described above. A UE can receive the configuration of the COT from a gNB.

[0181] In some embodiments, after CCA succeeds, the UE can transmit a channel or a signal in the uplink (referred to as uplink transmission) to initiate the COT. The uplink transmission by the UE can be a PUSCH based on a configured grant (CG). Or, the uplink transmission can be a PUCCH based on gNB’s radio resource control (RRC) configuration and CSI (channel state information) such as CQI, rank indicator (RI), precoding matrix indicator (PMI). In one example, the uplink transmission is a PUCCH (HARQ) or a SR (scheduling request) or both sent in a PUCCH. In another example, the uplink transmission can be a physical random access channel (PRACH) preamble sent by the UE. The PRACH opportunity (in terms of time and frequency resources) and the preamble sequence of the PRACH preamble can be configured by the gNB. In yet another example, the uplink transmission can be a SRS (sounding reference signal) transmitted to the gNB in a SRS resource (in terms of time and frequency resources, comb location, sequence, etc.) configured by the gNB.

[0182] In some embodiments, after CCA succeeds, the UE can send a COT grant request to the gNB in the uplink to request the gNB to initiate the COT. The COT grant request can be sent in a PUCCH resource or a PDSCH resource based on a CG. The COT grant request can include information of one or more of the following: a SR (scheduling request), a BSR (buffer status report) at the UE, or a CSI.

[0183] The gNB detects possible uplink transmissions from the UE initiating or requesting COT on the channels and signals configured to the UE for COT initiation. For example, when the gNB is transmitting within a COT initiated by the gNB, the gNB can not be able to perform detection at the uplink. In addition, the gNB can not be able to detect the uplink transmission due to interference, low signal level, etc. Thus, the uplink transmission from the UE initiating or requesting COT can be missed by the gNB. In addition, multiple UEs can transmit in the uplink, roughly simultaneously, initiating or requesting COT. Thus, several cases can occur. In one case, the UE is the only UE initiating or requesting COT at a point in time, so there is no conflict / overlap. In another case, both the UE and the gNB initiate COT, and the gNB misses the UE uplink transmission, so is not aware of the UE’s initiation or request of COT. In yet another case, the gNB also initiates COT (after CCA succeeds), and the gNB detects the UE uplink transmission, so is aware of the UE’s initiation or request of COT. In yet another case, another UE (or multiple UEs) can also initiate or request COT, and the gNB detects the COT initiation or request of multiple UEs.

[0184] After the UE transmits the uplink transmission initiating or requesting permission to initiate COT, the UE can wait for a response from the gNB. One reason for the UE waiting for the response of the gNB is to resolve conflicts and overlaps between COT initiated by the gNB and the UE or initiated by multiple UEs. The UE can not be aware of such conflicts or overlaps, and can take some time to realize this. Thus, the gNB can act as an arbitrator to resolve the conflicts and send a response to the UE indicating information of COT for the UE to use. As one example, the response from the gNB can include information indicating that the gNB acknowledges (or validates as valid or acknowledges) the COT initiated or requested by the UE. As another example, the gNB can validate that the COT initiated by the UE is invalid or reject the COT initiated by the UE. As yet another example, the gNB can inform the UE to use or share the COT initiated by the gNB. As yet another example, the gNB can inform the UE to use or share the COT initiated or requested by another UE. As yet another example, the gNB can determine and initiate a COT and send relevant information to the UE for the UE to share the COT. In the response, the gNB can acknowledge (acknowledge) or reject the COT initiated by the UE or the permission request of the UE to initiate COT, or indicate a type of COT that the UE can use, where the indicated COT can be initiated by the UE, another UE, or the gNB.

[0185] The gNB's response or indication of the COT type for the UE to use can be implicitly sent. That is, the gNB can implicitly indicate its response to the UE. For example, after the UE sends an uplink transmission to initiate or request a COT, the UE can perform detection on a downlink transmission from the gNB. If any downlink transmission from the gNB to the UE is detected within a certain time window, the UE can consider that the COT it requested or initiated is granted and can continue its uplink transmission, e.g., using the COT and based on the parameters configured for the COT initiated for the UE, such as the periodicity (or FFP associated with the COT), COT duration, idle time of the periodicity, and offset of the periodicity with respect to the frame number. Although such implicit reply by the gNB can be applicable in relatively simple cases without considering collision of COTs, there can be ambiguity, e.g., when the gNB sends a downlink transmission to the UE using a different COT.

[0186] In some embodiments, the gNB's response or indication of the COT to use can be explicitly sent. For example, after the UE sends an uplink transmission to initiate or request a COT, the UE can perform detection on a downlink control information (DCI). The gNB can send COT information in the DCI. The COT information can include a COT configuration index that identifies a COT configuration. Multiple COT configurations (each including a periodicity (e.g., FFP) associated with the COT, COT duration, idle time of the periodicity, and / or offset of the periodicity with respect to the frame number) can be configured to the UE, e.g., via RRC, and each COT configuration can be assigned an index value. Each COT configuration defines and corresponds to one COT. By sending the index of the COT configuration to the UE, the UE is informed of the corresponding COT to use. In one example, the COT information sent in the DCI can include a set of parameters (e.g., COT parameters) necessary for the UE to correctly use or share the COT, and the set of parameters includes the periodicity associated with the COT, COT duration, idle time of the periodicity, and offset of the periodicity with respect to the frame number. The DCI used to send the COT information to the UE can be UE-specific. Alternatively, the COT information can be sent to a group of UEs using a group-common DCI. The COT information can also be sent in a medium access control element (MAC CE). After the UE detects the gNB's response and obtains the information of the COT to use or share, the UE transmits in the uplink within the COT according to the COT information or parameters indicated to the UE.

[0187] In one embodiment, the gNB can indicate to the UE that no COT will be used. As one example, after transmitting in uplink to the gNB to initiate or request a COT, the UE can consider the COT initiation to fail or the requested COT to be rejected when the UE does not detect any validation valid / ACK message from the gNB within a time window indicating a COT to be used. In this case, the UE can perform sensing for downlink transmissions in order to share the gNB indicated COT, or the UE can perform CCA to initiate or request a COT again.

[0188] In one embodiment, after transmitting in uplink to the gNB to initiate or request a COT, the UE can consider the COT initiation or request to be granted when the UE does not detect any validation valid / ACK message from the gNB within a time window indicating a COT to be used, and does not detect other downlink transmissions. The UE can then perform transmissions within the initiated or requested COT.

[0189] Figure 15 A flowchart showing an embodiment operation 1500 of a UE to request a new UE COT for FFP is shown. The UE sends a UL request to the gNB requesting a new UE initiated COT for FFP (step 1502). The requested new UE COT can have different parameters than a COT already used by the UE. The UE then starts a timer to wait for a response from the gNB in response to sending the UL request (step 1504). If the UE does not detect a response from the gNB (step 1506) and the timer does not expire (step 1508), the UE returns to step 1506 to continue listening for a response from the gNB. If the timer expires and the UE does not receive a response from the gNB (step 1508), the UE does not change the COT for FFP used by the UE (step 1510). If the UE detects a response from the gNB (step 1506), the UE determines whether the response indicates that the request is accepted by the gNB (step 1512). If the request is not accepted by the gNB, the UE proceeds to step 1510. If the request is accepted by the gNB, the UE can perform transmissions within the new UE COT. The response can indicate parameters of the requested new COT, such as a location of the FFP, a duration of the COT within the FFP, an idle period within the FFP, etc., as described above. The UE can wait for an offset duration of the FFP indicated by the response, perform CCA before the FFP, and initiate the COT after the CCA is successful.

[0190] The UE can send the UL request in various ways, requesting permission to initiate a COT for a FFP. In one embodiment, the UE can send the request while sharing a gNB initiated COT. That is, the request is sent using a gNB initiated COT. In another embodiment, the UE can send the UL request while sharing a gNB initiated COT. That is, the request is sent using a gNB initiated COT. In another embodiment, the UE can send the request while inside its own initiated COT that is shared with a gNB. That is, the request is sent using a UE initiated COT that is shared with a gNB. In yet another embodiment, the UE can send the request while inside its own initiated COT for a FFP, and the UE wishes to change the parameters of the ongoing FFP to different parameters of a FFP. That is, the UE sends the request inside a UE initiated COT within an ongoing FFP, and the UE requests a new FFP and / or a new COT within the new FFP. In this request, the UE can provide the gNB with parameters for a new COT of the new FFP, including but not limited to periodicity, channel or channel bandwidth, maximum idle duration, MCOT, and offset of the start of the new FFP period. The gNB can accept the request and the parameters requested in the request, or it can overwrite the requested parameters with a new set of parameters, e.g., the gNB can provide a different periodicity, or different frequency resources (channel) or different offset of the start of the new FFP. The gNB can also reject the request. If the request is rejected, the UE cannot start a new COT for the new FFP with the requested parameters. If the UE has been configured with a COT for a FFP, the UE can only be able to initiate a COT based on the existing configuration, or the UE can share a gNB initiated COT for a FFP, or the UE can only initiate or share a dynamic COT. If the request is accepted by the gNB, the UE can start initiating a COT after the offset duration. The acceptance or rejection by the gNB can be implemented in various ways, e.g., by adding a field to the HARQ ACK-NACK message, or adding a field in the DCI. The acceptance or rejection can also be done in a slower way by a MAC CE or RRC message. In some embodiments, the UE can assume acceptance (or rejection) unless the gNB rejects (accepts) the request.

[0191] Various embodiments of the present disclosure can allow alternating periods of dynamic COT and semi-static COT (with FFP) on both gNB and UE sides. The gNB can configure the time periods that allow dynamic or semi-static channel access.

[0192] For channel access for semi-static channel occupancy, as defined in TS 37.213, the gNB provides the UE with the higher layer parameter ChannelAccessMode-r16 ='semi static' through SIB1, or provides the UE with a dedicated configuration provided in SemiStaticChannelAccessConfig (indicating channel access parameters, e.g., periodicity of semi-static channel access mode). In Frame Based Operation (FBE) mode in unlicensed / shared spectrum, a device can transmit a maximum occupancy time (MCOT) in every fixed frame period (FFP). The MCOT can be up to 95% of the FFP. The FFP, MCOT duration within each FFP, and idle period are parameters (or configurations) that characterize the gNB- or UE-initiated COT of each FFP.

[0193] Similarly, there is a need to provide the UE with the associated parameters necessary for UE-initiated COT of the FFP by the gNB. The parameters of the UE FFP (COT opportunity), such as the periodicity of the FFP, MCOT, time offset (e.g., relative to even frame or frame number 0) can be different from the parameters of the gNB-initiated COT of the FFP. The higher layer parameters for providing channel access parameters as defined in TS 37.213 can be extended to provide the parameters associated with the UE-initiated COT. For example, the higher layer parameters can be extended as shown in Figure 16 Figure 16 ​An example of a semi-static channel access configuration information element (IE) 1600 usable for embodiments of the present disclosure is shown. As shown, the semi-static channel access configuration IE 1600 includes parameters for UE-initiated COT, such as offset, periodicity, MCOT, etc. The value set for the periodicity, offset, and MCOT of UE-initiated COT can be the same as that of gNB-initiated COT, and the values provided to the UE can be the same or different from those configured for gNB-initiated COT. The periodicity of a COT or COT opportunity can also be referred to as the periodicity of the FFP associated with the COT. The periodicity of gNB-initiated COT can be from the following value set in ms: {1, 2, 2.5, 4, 5, 10}. The offset of gNB-initiated COT can be from the following value set in ms: {1, 2, 2.5, 4, 5, 10}. The MCOT of gNB-initiated COT can be from the following value set in %: {80, 85, 90, 95}. The periodicity of UE-initiated COT can be from the following value set in ms: {1, 2, 2.5, 4, 5, 10}. The offset of UE-initiated COT can be from the following value set in ms: {1, 2, 2.5, 4, 5, 10}. The MCOT of UE-initiated COT can be from the following value set in %: {80, 85, 90, 95}. In one embodiment, the values provided to the UE can be configured independently from those configured for gNB-initiated COT, and any value from the set can be taken, whether the set is the same or different from that configured for gNB-initiated COT. In another embodiment, for the periodicity, the values provided to the UE can depend on those configured for gNB-initiated COT, where only a subset of values can be provided to the UE, such as values that are multiples of each other. As one example of this embodiment, if the gNB-configured COT has a periodicity of 2 ms, then the UE can be provided a periodicity of 1, 2, 4, or 10, but not 2.5 or 5. The capability information can indicate the UE’s capability to initiate COT, including the capability to take any value from the value set {1, 2, 2.5, 4, 5, 10} in ms for the periodicity of UE-initiated COT independently from the values configured for the periodicity of gNB-initiated COT.

[0194] One or more such configurations can be provided to the UE. When the UE receives a switching command to switch from an ongoing COT to a new COT, the UE can stop using the configuration of the ongoing COT and start using the configuration of the new COT. For example, the UE stops sharing the ongoing COT and instead shares the new COT. The dynamic indication of the new COT can require the gNB to provide the UE with the remaining duration of the new COT. From the indication of the new COT parameters of the new COT from the gNB, the UE can be configured to follow the silent (idle) period associated with the new COT parameters. The remaining COT duration of the new COT can be provided, for example, in DCI format 2 0 as specified in TS 38.212.

[0195] In some embodiments, the DCI format 2 0 can be extended to send FFP configuration (or COT configuration) parameter switching or FFP configuration parameter indication by indicating SemiStaticAccessConfig-ID. The DCI format 2 0 can be extended to indicate to the UE a target FFP (e.g., by indicating the FFP configuration or FFP configuration parameters of the target FFP or target COT (UE initiated COT or gNB initiated COT)) for the UE to switch to the target FFP configuration or use the target COT (UE initiated COT or gNB initiated FFP). The UE can use or switch to the indicated target COT and start sharing after the N COT switch slot (switching time). Until this time, the transmission from the UE is considered within the ongoing UE COT. Before the end of the switching time, the UE performs transmission within its ongoing COT. After the end of the switching time, the UE starts using the target COT. If the target COT expires before N COT switch, the UE can not switch to the target COT and the UE can complete the ongoing COT of the FFP. If the target FFP configuration of the FFP corresponds to one of the possible configurations of the UE (e.g., based on SemiStaticChannelAccessConfig_UE_List), the UE can initiate a new COT with new COT parameters. The new COT parameters are the parameters of the target COT. If the COT parameters of the target COT belong to SemiStaticChannelAccessConfig_gNB_List, the UE can listen to the gNB for a gNB initiated COT and can share that COT.

[0196] Figure 17A flow diagram of embodiment UE and gNB operations 1700 for switching COT of a UE is shown. In this example, a gNB can instruct a UE to switch transmissions from using a current COT to using a target COT. The gNB can initiate the COT switch via a DCI command (step 1702). Upon receiving the command, the UE can start a transition timer (TT) to transition from the current COT to the target COT (step 1704). The UE can determine whether the TT will expire earlier than the target COT duration (step 1706). For example, the UE can determine whether the TT will end before the target COT ends. If the UE determines that the TT will expire before the target COT ends, the UE switches to the target COT after the TT expires (step 1708). The UE can switch to using COT parameters corresponding to the target COT. If the UE determines that the TT will expire after the target COT ends, the UE can continue to use the current COT for transmissions until the current COT ends (step 1710), and then the UE switches to the target COT (step 1708). The UE can determine whether the target COT is a UE-initiated COT (step 1712). If the target COT is a UE-initiated COT, the UE can initiate a COT in the next opportunity (step 1714). The COT is initiated with the COT parameters of the target COT. If the target COT is not a UE-initiated COT, the UE can listen for a gNB-initiated COT for sharing (step 1716).

[0197] The gNB can provide the UE with configurations of gNB-initiated COTs for FFPs and / or UE-initiated COTs for FFPs. These configurations can be different.

[0198] A UE-initiated COT for FFP is triggered by an UL burst from the UE at the start of the UE FFP, as required by the spectral regulations according to ETSI EN 301 893 V2.1.1 (2017-05). The transmission is made after a sensing duration of at least 9 μβ of channel sensing, during which the channel must be found idle.

[0199] When a gNB-initiated COT for FFP and a UE-initiated COT for FFP overlap in time, their FFP periods and idle periods can be misaligned as shown. Figure 18 Figure 18 ​A diagram 1800 showing gNB-initiated COT 1810 and UE-initiated COT 1820 that are not aligned with each other is shown. The devices (UE and gNB) need to follow the transmission period and idle period associated with its own COT. In other words, the gNB and UE use a specific set of parameters (e.g., FFP periodicity, idle duration period, offset of FFP) associated with its own COT, respectively. At the same time, the gNB and UE can share the same COT (as specified in TS 37.213). The concept of sharing COT needs to be revised and clearly defined. If the UE transmits within the UE-initiated COT and the gNB transmits within the gNB-initiated COT, and these two COTs overlap in time, as shown in Figure 18 , then a problem can arise, e.g., whether these two COTs can be shared between the gNB and the UE. In some embodiments, to clarify these cases, when two devices transmit using a same set of COT parameters for FFP, they can share the COT for FFP. That is, if two devices transmit using a same set of COT parameters for FFP, then they share the COT for FFP.

[0200] In some embodiments, when the UE transmits during a COT for FFP that overlaps with another COT, the gNB should explicitly identify which COT the UE transmission belongs to. The gNB needs to determine whether the COT used by the UE for the UE transmission belongs to the UE-initiated COT or the gNB-initiated COT. In one embodiment, the gNB can decode a UE transmission burst that starts at the beginning of a UE FFP opportunity and interpret it as a UE COT initialization. That is, when the gNB receives a UE transmission burst that starts at the beginning of a UE FFP opportunity, the gNB can determine that the UE initiated a COT. However, it cannot be explicitly determined based on a simple UE transmission whether the UE initiated its own COT or the UE just shared the gNB’s COT. To solve this dilemma, the UE can explicitly indicate to the gNB that the UE initiated its own COT. For example, the UE’s UL transmission can have an additional field that identifies or indicates the UE-initiated COT or the gNB-initiated COT. Such signaling can help the gNB determine that the UE transmission belongs to the UE-initiated COT for FFP, but does not explicitly indicate the COT for further UE transmissions during the overlapping COT.

[0201] To address these issues, in one embodiment, the proposed scheme requires that the transmission from the UE should belong to the same (single) COT until the end of that COT unless the gNB indicates otherwise. This requires that once the UE initiates a COT for FFP, the UE remains within the same COT for transmission, i.e., the UE cannot switch back and forth between its own initiated COT and gNB initiated COT. However, if necessary, the gNB can instruct the UE to change to a different COT. For example, the UE can decide to initiate its own COT during which the gNB instructs the UE to switch to a gNB initiated COT and share that COT. Thus, the gNB can dynamically instruct the UE which set of COT parameters to use. The COT configuration change can be done via dynamic control information (e.g., DCI) or via RRC configuration. A set of UE initiated COT parameters for FFP can be dynamically configured by the gNB. UL scheduling grants can specify the resources and opportunities for UE initiated COT for FFP. For Internet of Things (IoT) applications, the UL transmission can be triggered by an external event that forces the UE to initiate a COT at the nearest opportunity time.

[0202] Figure 19 A flow diagram illustrating embodiment UE and gNB operations 1900 for channel access is shown, highlighting dynamic COT change. The gNB can configure parameters for UE initiated COT and gNB initiated COT (step 1902). The gNB can also allocate UL grants, e.g., resources, for specific types of traffic and specific COT (step 1904). The UE can initiate a COT for FFP via a UL burst (step 1906). The UL burst can start at the beginning of the FFP associated with the COT, which indicates that the UE initiates the COT. For example, based on the UL burst received by the gNB, the gNB determines that the UE has initiated the COT (step 1908). The UE can determine whether the gNB dynamically instructs the UE to change to a new COT (step 1910). If the gNB does not instruct the UE to change to a new COT, the UE can continue to use its initiated COT (step 1912). If the gNB instructs the UE to change to a new COT, the gNB can provide the remaining duration of the new COT and trigger the COT switch (step 1914). The gNB can instruct and trigger the COT switch by sending a DCI to the UE. The DCI can include information about the remaining COT duration of the new COT. The UE can start using the new COT (step 1916).

[0203] In some embodiments, after the UE initiates its own COT, the UE can start a timer and wait for a verification from the gNB of the UE initiated COT. This verification can be any DL transmission that does not require the UE to switch to a different set of COT parameters (i.e., a different COT). If the UE receives such a switch command before the timer expires, the UE can switch to a different COT, using a different set of COT parameters. If the UE does not receive such a switch command before the timer expires, and the UE does not receive other DL transmissions before the timer expires, the UE can automatically fall back to sharing the gNB initiated COT.

[0204] For a UE that indicates (e.g., in a capability indication) support for UE initiated COT in FBE mode of operation, when scheduling a UL grant, the gNB can indicate whether the UL transmission from the UE should be performed within the gNB initiated COT using the gNB FFP configuration or within the UE initiated COT using the UE FFP configuration. For example, the indication can be made using a DCI field, and the presence of the DCI field indicates the type of FFP used for UL transmission scheduling. This field is always present during FBE operation when the gNB schedules a UE UL transmission. This indication will avoid the need for additional rules to handle cases when the field is missing. One example of such a case is when there is a gNB initiated COT and a UE initiated COT that overlap each other. The presence of the DCI field indicating the COT UL transmission type will allow the gNB to respond with low latency to certain IIoT / URLLC operation events. In one embodiment, for example, it can be specified in the standard that in FBE mode of operation, there is no field in the DCI that determines whether the scheduled UL transmission is based on the UE initiated COT or the shared gNB initiated COT.

[0205] According to ETSI requirements, the UE initiated COT starts from a UL transmission. An example of such a UL transmission that can initiate a COT can be a configured grant periodic / semi-persistent transmission. However, there are cases where aperiodic / persistent transmission can be needed. For example, the gNB can need to schedule the UE to transmit aperiodic SRS or aperiodic CSI-RS report. If this happens at the end of a COT, the gNB can need to wait for the next COT and then transmit a DCI with a scheduling grant. Thus, an additional delay will be added. However, if the gNB is able to schedule a UL grant at the end of a COT after the start of the next COT, the response time can be greatly improved.

[0206] In another example, the UE can transmit a request, such as a scheduling request (SR), at the end of a COT. If the gNB can transmit a DCI with an allocation that spans COTs, the delay of the UL transmission can be reduced.

[0207] In another example, the DCI scheduling the aperiodic transmission has an indication indicating that the aperiodic transmission will be performed within a UE-initiated COT (FFP) of the next UE FFP cycle, which can be used for a one-off UE-initiated COT for low latency aperiodic applications.

[0208] There can be multiple ways to indicate the scheduling time of the UL transmission, e.g.,

[0209] DCI with a transmission time scheduled by the DCI that is greater than the current COT

[0210] DCI with FFP index indication (0 means current) and UL transmission time within that FFP (less than COT duration)

[0211] When the scheduling time of the UL transmission is later than the COT end time of the current FFP, the UE can determine the FFP (during which the UL transmission will be performed) by calculating the difference between the scheduling time and the COT end time of the current FFP and dividing the difference by the FFP duration, as shown in Figure 26 Figure 26 A diagram illustrating an embodiment operation 2600 between a gNB and a UE is shown. The gNB sends a DCI 2602 at the end of the COT of the current FFP 2604 to schedule an UL transmission 2606.

[0212] It is possible that a situation occurs where the gNB or the UE cannot initiate the next FFP due to LBT failure. In this case, the device (gNB or UE) needs to wait for another FFP cycle before attempting to initiate a new COT. If the UL transmission is scheduled within the failed FFP, the UE needs to delay the scheduled transmission to the next FFP. Thus, when an UL transmission is scheduled for a future FFP (within a gNB-FFP or a UE-FFP) and the FFP (COT of the FFP) cannot be initiated, the UL transmission is delayed to the next FFP that can be initiated (e.g., by the gNB or the UE). Examples of such transmissions can include CSI-RS reporting, SRS, data, etc.

[0213] Another problem to be solved is the type of FFP configuration used for delaying the transmission.

[0214] ​If the scheduling DCI indicates that the UL transmission scheduled after the end of the current COT should be completed within a gNB-initiated COT or a UE-initiated COT, the UE can wait for the corresponding gNB-initiated COT or UE-initiated COT for the transmission. That is, if the COT initiation fails, the UE will wait until the corresponding (necessary) COT is initiated. To calculate the time or slot index for the UL transmission, the UE can stop the slot counter at the end of the COT (where the scheduling DCI is located) and continue to increment the slot counter at the start of the corresponding initiated COT.

[0215] In one embodiment, a default timer that starts when the cross-COT scheduling DCI is received can be considered. If the timer expires before the COT (indicated in the scheduling DCI) can be initiated, the UE can cancel its transmission and request new resources.

[0216] The scheduling within the next FFP can depend on the type of UL transmission, such as data, SRS, or CSI. Furthermore, the delay of data can also depend on the type of transmission and / or its priority. For example, any transmission can be allowed within the next FFP, but further delay can be allowed only for A-SRS or A-CSI reporting.

[0217] In industrial Internet of things (IIoT) and URLLC applications, there are transmissions triggered by periodic events such as measurements and reporting, and transmissions triggered by non-planned events such as alarms. To handle unexpected / non-planned cases, and to schedule some transmissions with higher priority than already scheduled periodic / semi-persistent transmissions, the gNB should be able to cancel upcoming transmissions, including those that can initiate a COT. One possible solution is to use the activation / deactivation of CG Type 2 PUSCH. Additional cancellation modes can also be considered.

[0218] The gNB can cancel UL transmissions occurring within future FFPs, including, for example, by canceling UL transmissions that initiate a COT, canceling future UE-initiated COTs within future FFPs.

[0219] Examples of cancellation signaling can include a transmission DCI (e.g., in DCI 2_0), RRC, MAC CE, or the cancellation can be implemented via a timer expiration. Another way to cancel UE-initiated COTs in the future can be for the gNB to change the symbol configuration from UL symbols to DL symbols.

[0220] To accommodate multiple UEs independently initiating overlapping COTs, the gNB can request these UEs to switch to a different FFP configuration. For example, the gNB can instruct these UEs to switch to a gNB FFP configuration and a gNB initiated COT, which can synchronize these UEs. The gNB can instruct the UE to switch between FFP configurations, e.g., from a UE FFP to a gNB FFP within the current UE initiated FFP or at a future FFP boundary. An example of signaling for such switching can be performed via DCI, RRC, MAC CE associated with the expiration of some timer for switching the deadline.

[0221] In one embodiment, in case of link failure, the UE can switch to a gNB FFP configuration, i.e., wait for a gNB initiated COT. In another embodiment, in case of link failure, the UE can be configured to initiate a COT within a UE FFP and transmit a UL broadcast (e.g., a distress signal or beacon). In this scheme, if the UE losing connectivity is surrounded by multiple receivers, such as gNBs, then the UE can be discovered faster.

[0222] In another embodiment, a default FFP can be configured by the gNB. If there is a link failure, the UE switches to the default FFP configuration. In another embodiment, the UE FFP configuration can fall back to a default configuration after multiple FFP failures due to LBT failure (i.e., consistent LBT failure, which can be different from link failure).

[0223] Further, UL scheduling grants for various types of traffic can specify the respective groups of COT parameters for FFPs to be used. In this way, different types of UL traffic can be configured to be transmitted within different COTs. For example, some emergency or low latency indicated transmissions can be allowed within a UE initiated COT, while other UL traffic can only be allowed within a gNB initiated COT. Thus, different types of traffic can only be allowed in specific types of COT initialization.

[0224] In some embodiments, if the UE determines that the link between the UE and the gNB is lost, the UE can return or fall back to a gNB initiated COT for FFP and perform transmissions using a set of parameters of the gNB initiated COT.

[0225] Figure 20A flow diagram illustrating embodiment UE and gNB operations 2000 for channel access, highlighting verification of UE COT initiation, is shown. The gNB can configure parameters for UE initiated COT and gNB initiated COT (step 2002). The gNB can also allocate UL grants, e.g., resources, for specific types of traffic and specific COT (step 2004). The UE can initiate a COT for an FFP via a UL burst and start a timer for gNB verification (step 2006). The UE can wait for gNB verification of the UE initiated COT before the timer expires. The UL burst can start at the beginning of the FFP associated with the COT, which indicates that the UE initiated the COT. The UE can determine whether the gNB verified that the UE initiated COT is valid (step 2008). If the UE determines that the gNB verified that the UE initiated COT is valid, the UE can continue to use its initiated COT (step 2010). If the UE determines that the gNB did not verify that the UE initiated COT is valid, the UE determines whether it receives an instruction to switch to and share a new COT (step 2012). If the UE receives the instruction, i.e., the gNB sends the instruction to the UE, this means that the gNB verified that the UE initiated COT is not valid, the gNB can provide the UE with information of the remaining duration of the new COT and trigger the switch (step 2014). The UE can start using (sharing) the new COT (step 2016). If the UE does not receive the instruction and the timer for gNB verification expires, the UE can start using the gNB initiated COT (step 2018).

[0226] Corresponding resources for UE COT initiation for an FFP can be configured, e.g., by CG Type 2, which is configured by RRC and activated by PDCCH scrambled with configured scheduling (CS)-RNTI prior to UE COT utilization. In this way, the gNB can directly control whether the UE can initiate a COT within the next FFP. The UE can be configured with the necessary resources for UE COT initiation for an FFP via CG Type 2.

[0227] Challenging scenarios can occur when a gNB serves many UEs that are capable of independently initiating COT. IoT applications are likely to see such cases. In this case, since the gNB cannot predict when which UE (e.g., IoT device) can initiate COT, and multiple UE initiated COTs can overlap in time, the control of UE initiated COT can become quite complex. One possible solution to handle a large number of UE devices is that UE devices can be divided into multiple groups, and (re)configuration (e.g., COT configuration) can be based on group via group common control. In one embodiment, UE group based dynamic (re)configuration of UE initiated COT for FFP can be supported, such as group based COT parameter dynamic (re)configuration.

[0228] As shown in Figure 21 there is a possibility that gNB and UE can alternate their COTs, where the duty cycle of gNB and UE occupying the whole channel can be greater than the duty cycle allowed by the regulator (>95%). In other words, while gNB and UE follow their own idle periods, they overall occupy the channel more than 95%. Figure 21 A schematic diagram 2100 showing embodiments of COTs of gNB and UE is shown, highlighting non-overlapping COTs of gNB and UE occupying the channel. In one embodiment, this can be avoided when UE and gNB share the same COT for FFP. Thus, gNB and UE will follow the idle time for the corresponding FFP and avoid capturing the channel.

[0229] Certain types of UEs can be capable of or allowed to initiate COT, and certain types of UEs can not be capable of or allowed to initiate COT. For example, regular UEs can not be able to initiate COT for FFP, while new URLLC UEs can be able to initiate COT for FFP. In this case, if a UE is able to initiate COT with RACH transmission, the UE can inform the gNB of its capability to initiate COT. For example, the UE can use a specific PRACH sequence to indicate its capability, or indicate its capability via message 3 (MSG3) if the UE receives a message 2 (MSG2) that allows the UE to initiate COT for FFP. The UE should support capability signaling to inform the gNB of its ability to initiate COT for FFP. The signaling can be provided during random access or via PUCCH or PUSCH.

[0230] Embodiments of the present disclosure provide the following:

[0231] A method for UE to initiate periodic COT, which can or can not be confirmed by gNB. A method for a group of UEs to contend to initiate aperiodic COT, which can be confirmed by gNB.

[0232] A method for UE and gNB contention initiation of periodic COT. This provides an opportunity for flexible UL and DL transmission when gNB has priority to initiate periodic COT. UE can wait for a random time period.

[0233] A method for gNB to communicate with a UE that wins a contention for periodic COT. For a number of periods, the UE is the owner of the periodic COT. Owner means that the UE is the only device that can trigger COT for a number of periods.

[0234] A method for specifying different traffic types allowed in certain COT initiation, e.g., emergency traffic is allowed within UE initiated COT and gNB initiated COT, and some traffic with low priority can be allowed only within gNB initiated COT, etc.

[0235] Group (re)configuration of COT parameters for FFP. Dynamic change of UE COT parameters for FFP, which validates ongoing COT as valid or invalid.

[0236] Capability signaling to support UE initiated COT.

[0237] UE fallback to share gNB initiated COT after link failure or validation invalidation from gNB.

[0238] Figure 22 A flow diagram illustrating an embodiment method 2200 for UE COT initiation is shown. The method 2200 can indicate operations of a UE operating in FBE mode. As shown, the UE can determine that a communication channel in an unlicensed spectrum is available (step 2210). The UE can transmit, in the communication channel, a first transmission to a gNB within a fixed frame period (FFP) associated with the UE to initiate, by the UE, a channel occupancy time (COT) within the FFP. The first transmission starts at a beginning of the FFP and ends before an idle period within the FFP (step 2220).

[0239] Figure 23 A flow diagram illustrating another embodiment method 2300 for UE COT initiation is shown. The method 2300 can indicate operations of a gNB in communication with a UE operating in FBE mode. The gNB can receive, from the UE, a first transmission within a fixed frame period (FFP) in a communication channel of an unlicensed spectrum (step 2310). The first transmission can start at a beginning of the FFP and end before an idle period of the FFP. The gNB can determine, upon receiving the first transmission, that the UE initiates a channel occupancy time (COT) within the FFP (step 2320).

[0240] It should be understood that one or more steps of the methods provided in the embodiments herein can be performed by corresponding units or modules. For example, a signal can be transmitted by a transmitting unit or transmitting module. A signal can be received by a receiving unit or receiving module. A signal can be processed by a processing unit or processing module. Other steps can be performed by a determining unit / module, a detecting unit / module, a COT switching unit / module, an instruction unit / module, a timer starting unit / module, an allocation unit / module, a configuration unit / module, a signaling unit / module, an indication unit / module, a verification unit / module, a COT response / non-response / rejection unit / module, a COT initiation unit / module, a COT monitoring unit / module, a COT sharing unit / module, and / or a request unit / module. Each unit or module can be hardware, software, or a combination thereof. For example, one or more units / modules can be integrated circuits, such as field-programmable gate arrays (FPGAs) or application-specific integrated circuits (ASICs).

[0241] The various embodiments of this disclosure can be implemented as computer-based methods. These embodiments can be executed by a processing system. Figure 24 A block diagram of an embodiment of a processing system 2400 for performing the methods described herein, which can be installed in a host device, is shown. As shown, the processing system 2400 includes a processor 2404, a memory 2406, and interfaces 2410 to 2414, which may (or may not) be configured as follows: Figure 24 As shown. Processor 2404 can be any component or set of components adapted to perform computational and / or other processing-related tasks, and memory 2406 can be any component or set of components adapted to store programs and / or instructions executed by processor 2404. In one embodiment, memory 2406 includes a non-transitory computer-readable medium. Interfaces 2410, 2412, and 2414 can be any component or set of components that allow processing system 2400 to communicate with other devices / components and / or users. For example, one or more interfaces of 2410, 2412, and 2414 can be adapted to communicate data, control, or management messages from processor 2404 to applications installed on host devices and / or remote devices. As another example, one or more interfaces of 2410, 2412, and 2414 can be adapted to allow a user or user device (e.g., a personal computer (PC)) to interact / communicate with processing system 2400. Processing system 2400 may include Figure 24 Other components not described herein, such as long-term memory (e.g., non-volatile memory, etc.).

[0242] In some embodiments, the processing system 2400 is included in a network device that accesses or otherwise is part of a telecommunication network. In one example, the processing system 2400 is in a network-side device in a wireless or wireline telecommunication network, such as a base station, a relay station, a scheduler, a controller, a gateway, a router, an application server, or any other device in the telecommunication network. In other embodiments, the processing system 2400 is in a user-side device that accesses a wireless or wireline telecommunication network, such as a mobile station, user equipment (UE), a personal computer (PC), a tablet computer, a wearable communication device (e.g., a smart watch, etc.), or any other device adapted to access the telecommunication network.

[0243] In some embodiments, one or more of the interfaces 2410, 2412, 2414 connect the processing system 2400 to a transceiver adapted to send and receive signaling over a telecommunication network. Figure 25 A block diagram of a transceiver 2500 adapted to send and receive signaling over a telecommunication network is shown. The transceiver 2500 can be installed in a host device. As shown, the transceiver 2500 includes a network-side interface 2502, a coupler 2504, a transmitter 2506, a receiver 2508, a signal processor 2510, and a device-side interface 2512. The network-side interface 2502 can include any component or collection of components adapted to send or receive signaling over a wireless or wireline telecommunication network. The coupler 2504 can include any component or collection of components adapted to facilitate bi-directional communication over the network-side interface 2502. The transmitter 2506 can include any component or collection of components adapted to convert baseband signals into modulated carrier signals suitable for transmission over the network-side interface 2502 (e.g., an up-converter, a power amplifier, etc.). The receiver 2508 can include any component or collection of components adapted to convert carrier signals received by the network-side interface 2502 into baseband signals (e.g., a low-noise amplifier, a down-converter, etc.). The signal processor 2510 can include any component or collection of components adapted to convert the baseband signals into data signals suitable for communication by or among one or more device-side interfaces 2512, or to perform an inverse conversion. The one or more device-side interfaces 2512 can include any component or collection of components adapted to communicate data signals between the signal processor 2510 and components within the host device (e.g., the processing system 2400, a local area network (LAN) port, etc.).

[0244] The transceiver 2500 can transmit and receive signaling over any type of communication medium. In some embodiments, the transceiver 2500 transmits and receives signaling over a wireless medium. For example, the transceiver 2500 can be a wireless transceiver adapted to communicate according to a wireless telecommunication protocol, such as a cellular protocol (e.g., long-term evolution (LTE), etc.), a wireless local area network (WLAN) protocol (e.g., Wi-Fi, etc.), or any other type of wireless protocol (e.g., Bluetooth, near field communication (NFC), etc.). In these embodiments, the network-side interface 2502 includes one or more antennas / radiating elements. For example, the network-side interface 2502 can include a single antenna, a plurality of separate antennas, or a multiple antenna array for multiple layer communication, such as single-input multiple-output (SIMO), multiple-input single-output (MISO), multiple-input multiple-output (MIMO), etc. In other embodiments, the transceiver 2500 transmits and receives signaling over a wired medium, such as a twisted pair of wires, a coaxial cable, a fiber optic cable, etc. Particular treatment systems and / or transceivers can utilize all of the components shown, or only a subset of these components, and levels of integration can vary from device to device.

[0245] The following references are related to the subject matter of the present application. The entire contents of each reference are incorporated herein by reference.

[0246] 3GPP TS 38.213, V16.5.0 (2021-03), “3rd Generation Partnership Project; Technical Specification Group Radio Access Network; NR; Physical Layer Procedures for Control (Release 16)”; and

[0247] 3GPP TS 37.213, V16.3.0 (2020-09), “3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Physical Layer Procedures for Shared Spectrum Channel Access (Release 16)”; and

[0248] ETSI EN 301 893 V2.1.1 (2017-05), “5 GHz RLAN; Harmonised Standard covering the essential requirements of article 3.2 of the New Approach Directive 2014 / 53 / EU”; and

[0249] Although described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the disclosure as defined by the appended claims. Moreover, the scope of the disclosure is not intended to be limited to the particular embodiments described herein, but rather, are as set forth in the appended claims, and include processes, machines, manufacture, compositions of matter, means, methods or steps similar or equivalent to those described in which the essential characteristics of the application are maintained. Accordingly, the appended claims are intended to cover all such processes, machines, manufacture, compositions of matter, means, methods or steps.

Claims

1. A method for a user equipment, UE, initiated channel occupancy time, COT, of a frame based equipment, FBE, characterized in that, Comprising: A user equipment in a frame-based equipment mode determines a communication channel in an unlicensed spectrum is available; And The UE transmits a first transmission in the communication channel to a gNB within a fixed frame period (FFP) associated with the UE to initiate a first channel occupancy time (COT) by the UE within the FFP, the first transmission starts at the beginning of the FFP and ends before an idle period within the FFP; The method further comprises: the UE receives information of a time interval (T_UE_COT) during which the UE is allowed to initiate a periodic COT, the time interval (T_UE_COT) comprises the FFP; The method further comprises: The UE receives an indication from the gNB within a preset time period after transmitting the first transmission, the indication indicates that the initiation of the first COT by the UE is confirmed or rejected, the indication is carried in a physical downlink control channel (PDCCH), a downlink control information (DCI) or a hybrid automatic repeat request acknowledgement (HARQ_ACK); or The UE determines that the initiation of the first COT by the UE is confirmed when a downlink transmission is received from the gNB within the time period after transmitting the first transmission, or determines that the initiation of the first COT is rejected when no downlink transmission is received from the gNB within the time period.

2. The method of claim 1, wherein, Determining that the communication channel is available comprises: The UE performs a clear channel assessment (CCA).

3. The method of claim 2, wherein, Determining that the communication channel is available comprises: The UE starts a backoff counter after the CCA is successful; and The UE determines that the communication channel is available when the backoff counter decrements to zero (0).

4. The method according to any one of claims 1 to 3, characterized in that, The first transmission comprises a physical uplink control channel (PUCCH), a physical uplink shared channel (PUSCH), channel state information (CSI), a scheduling request (SR), a random access preamble or a sounding reference signal (SRS).

5. The method according to any one of claims 1 to 3, characterized in that, The first transmission occupies all or part of a frequency bandwidth of the communication channel.

6. The method according to any one of claims 1 to 3, characterized in that, The first COT is a periodic COT initiated by the UE.

7. The method according to any one of claims 1 to 3, characterized in that, Further comprising: The UE receives configuration information that configures the UE to initiate a semi-static COT in the communication channel.

8. The method according to any one of claims 1 to 3, characterized in that, Further comprising: The UE receives configuration information of the first COT, the configuration information of the first COT comprises one or more of: A COT index of the first COT; A periodicity of the FFP; A maximum allowed COT duration (MCOT) within the FFP; A time offset of the FFP; A minimum idle duration within the FFP; A maximum idle duration within the FFP; An offset of the FFP; or Frequency resources for uplink transmission during the first COT.

9. The method of claim 8, wherein, The offset of the FFP or a starting position of the FFP is relative to a boundary of a radio frame with an even index number.

10. The method of claim 8, wherein, The periodicity of the FFP comprises a value in {1, 2, 2.5, 4, 5, 10} in milliseconds (ms).

11. The method of claim 8, wherein, The periodicity of the FFP comprises any value in {1, 2, 2.5, 4, 5, 10} in milliseconds (ms), or a subset of values in {1, 2, 2.5, 4, 5, 10}, based on a capability of the UE to initiate a COT.

12. The method of claim 8, wherein, The periodicity ranges from 1 ms to 10 ms.

13. The method of claim 7, wherein, The configuration information is received through dedicated radio resource control (RRC) signaling.

14. The method of any one of claims 1 to 3, wherein, Further comprising: The UE receives listen-before-talk (LBT) type information for listening to the communication channel.

15. The method of claim 1, wherein, Further comprising: The UE performs uplink transmission within the first COT of the UE when initiation of the first COT of the UE is confirmed.

16. The method of claim 1, wherein, Further comprising: The UE performs uplink transmission within a second COT initiated by the gNB when initiation of the first COT of the UE is denied.

17. The method of any one of claims 1 to 3, wherein, Further comprising: The UE transmits a request to the gNB for a new COT to be used by the UE, the new COT requested being a UE-initiated COT.

18. The method of claim 17, wherein, Further comprising: The UE starts a timer after transmitting the request; And The UE receives an indication from the gNB indicating that the request is accepted before the timer expires, and the UE performs transmission within the new COT; or, when the request is not accepted by the gNB before the timer expires, the UE transmits another request for the new COT to the gNB.

19. The method of claim 17, wherein, The request is transmitted in a third COT that has been initiated by the gNB or has been initiated by the UE.

20. The method of claim 17, wherein, The request includes parameters of the new COT.

21. The method of any one of claims 1 to 3, wherein, Further comprising: The UE receives signaling during the first COT indicating that the UE switches from transmission according to the first COT to transmission according to a fourth COT.

22. The method of claim 21, wherein, The signaling includes information of a remaining duration of the fourth COT.

23. The method of claim 21, wherein, Further comprising: The UE starts a transition timer after receiving the signaling.

24. The method of claim 23, wherein, Further comprising: In response to the fourth COT ending before the transition timer expires, the UE continues to perform transmission within the first COT.

25. The method of claim 23, wherein, Further comprising: The UE switches to using the fourth COT for transmission after the transition timer expires.

26. The method of claim 25, wherein, The fourth COT is a UE-initiated COT, and the method further comprises: The UE initiates the fourth COT within a next FFP.

27. The method of claim 25, wherein, The fourth COT is a gNB-initiated COT, and the method further comprises: The UE listens for and shares the fourth COT within a next FFP.

28. The method of any one of claims 1 to 3, wherein, Further comprising: The UE transmits capability information, the capability information indicating a capability of the UE to initiate a COT.

29. A method for channel occupancy time, COT, initiated by a user equipment, UE, of a frame based equipment, FBE, comprising: 30 Comprising: A gNB receives a first transmission from a user equipment (UE) within a fixed frame period (FFP) in a communication channel of an unlicensed spectrum, the UE being in a frame-based equipment (FB) mode; And In response to the first transmission starting at a beginning of the FFP and ending before an idle period of the FFP, the gNB determines, based on the first transmission, that the UE initiates a first channel occupancy time (COT) within the FFP; The method further includes: transmitting, by the gNB, information of a time interval T_UE_COT to the UE, wherein the UE is allowed to initiate a periodic COT during the time interval, and the time interval T_UE_COT comprises the FFP; The method further includes: In response to receiving the first transmission, the gNB sends an indication to the UE within a preset time period indicating that the initiation of the first COT of the UE is confirmed or rejected, the indication being carried in a physical downlink control channel (PDCCH), downlink control information (DCI), or a hybrid automatic repeat request acknowledgement (HARQ_ACK); or In response to receiving the first transmission, the gNB performs downlink transmission to the UE within the time period to confirm the initiation of the first COT, or the gNB does not perform downlink transmission to the UE within the time period to indicate that the initiation of the first COT is rejected.

30. The method of claim 29, wherein, The first transmission includes a PUCCH, a PUSCH based on a configured grant, channel state information (CSI), a scheduling request (SR), a random access preamble, or a sounding reference signal (SRS).

31. The method of claim 29 or 30, wherein, The first transmission occupies all or part of the frequency bandwidth of the communication channel.

32. The method of claim 29 or 30, wherein, Further comprising: The gNB transmits configuration information to the UE to configure the UE to initiate a semi-static COT in the communication channel.

33. The method of claim 29 or 30, wherein, Further comprising: The UE transmits configuration information of the first COT, the configuration information of the first COT including one or more of: a COT index of the first COT; a periodicity of the FFP; a maximum allowed COT duration (MCOT) within the FFP; a time offset of the FFP; a minimum idle duration within the FFP; a maximum idle duration within the FFP; an offset of the FFP; or a frequency resource for uplink transmission during the first COT.

34. The method of claim 33, wherein, The offset of the FFP or the starting position of the FFP is relative to the boundary of a radio frame with an even index number.

35. The method of claim 29 or 30, wherein, Further comprising: The gNB receives a request from the UE requesting a new COT to be used by the UE, the requested new COT being a UE-initiated COT.

36. The method of claim 35, wherein, Further comprising: The gNB indicates to the UE whether the request is accepted.

37. The method of claim 35, wherein, The request is received in a third COT that has been initiated by the gNB or has been initiated by the UE.

38. The method of claim 35, wherein, The request includes parameters of the new COT.

39. The method of claim 29 or 30, wherein, Further comprising: The gNB transmits signaling to the UE during the first COT indicating that the UE switches from transmission according to the first COT to transmission according to a fourth COT.

40. The method of claim 39, wherein, The signaling includes information of a remaining duration of the fourth COT.

41. The method of claim 39, wherein, The fourth COT is a gNB-initiated COT or a UE-initiated COT.

42. The method of claim 29 or 30, wherein, Further comprising: The gNB receives capability information from the UE, the capability information indicating the capability of the UE to initiate a COT.

43. The method of claim 29 or 30, wherein, Further comprising: the gNB receives, in the communication channel, a plurality of transmissions from a plurality of UEs for respective UEs within the FFP, each of the plurality of transmissions starting at a beginning of the FFP and ending before an idle period of the FFP; the gNB determines that each of the plurality of UEs initiates the first COT within the FFP; the gNB confirms the first COT initiated by the UE; and the gNB denies the first COT initiated by other UEs of the plurality of UEs.

44. The method of claim 29 or 30, wherein, Further comprising: the gNB cancels the first COT initiated by the UE within the FFP.

45. An apparatus for user equipment (UE) initiated channel occupancy time (COT) of a frame based equipment (FBE), the apparatus comprising: means for determining a COT request; and means for transmitting the COT request to a base station (BS) in a first frame of a COT window. Comprising: a non-transitory memory storage comprising instructions; and one or more processors in communication with the memory storage, wherein the instructions, when executed by the one or more processors, cause the apparatus to perform: determining that a communication channel in unlicensed spectrum is available, wherein the apparatus is in a frame-based equipment mode; transmitting, in the communication channel, a first transmission within a fixed frame period (FFP) associated with the apparatus to a gNB to initiate a first channel occupancy time (COT) by the apparatus within the FFP, the first transmission starting at a beginning of the FFP and ending before an idle period within the FFP; the instructions, when executed by the one or more processors, further cause the apparatus to perform: receiving information of a time interval (T UE COT) during which the apparatus is allowed to initiate a periodic COT, the time interval (T UE COT) comprising the FFP; the instructions, when executed by the one or more processors, further cause the apparatus to perform: receiving, from the gNB within a predetermined time period after transmitting the first transmission, an indication indicating that the initiation of the first COT by the UE is confirmed or denied, the indication being carried in a physical downlink control channel (PDCCH), a downlink control information (DCI), or a hybrid automatic repeat request acknowledgement (HARQ ACK); or determining that the initiation of the first COT by the UE is confirmed when a downlink transmission is received from the gNB within the time period after transmitting the first transmission, or determining that the initiation of the first COT is denied when no downlink transmission is received from the gNB within the time period.

46. An apparatus for user equipment (UE) initiated channel occupancy time (COT) of a frame based equipment (FBE), the apparatus comprising: means for determining a COT request; and means for transmitting the COT request to a base station (BS) in a first frame of a COT period. Comprising: a non-transitory memory storage comprising instructions; and one or more processors in communication with the memory storage, wherein the instructions, when executed by the one or more processors, cause the apparatus to perform: receiving, in a communication channel of an unlicensed spectrum, a first transmission within a fixed frame period (FFP) from a user equipment, the UE being in a frame-based equipment mode; and in response to the first transmission starting at a beginning of the FFP and ending before an idle period of the FFP, determining, based on the first transmission, that the UE initiates a first channel occupancy time (COT) within the FFP; the instructions, when executed by the one or more processors, further cause the apparatus to perform: transmitting, to the UE, information of a time interval T UE COT during which the UE is allowed to initiate a periodic COT, the time interval T UE COT including the FFP; the instructions, when executed by the one or more processors, further cause the apparatus to perform: in response to receiving the first transmission, sending, to the UE within a preset time period, an indication indicating that initiation of the first COT by the UE is confirmed or rejected, the indication being carried in a physical downlink control channel (PDCCH), a downlink control information (DCI), or a hybrid automatic repeat request acknowledgement (HARQ ACK); or 47. A non-transitory computer readable medium storing computer instructions, wherein, in response to receiving the first transmission, performing, to the UE within the time period, a downlink transmission to confirm initiation of the first COT, or not performing, to the UE within the time period, a downlink transmission to indicate that initiation of the first COT is rejected. the computer instructions, when executed by one or more processors of an apparatus, cause the apparatus to perform: determining that a communication channel in an unlicensed spectrum is available, wherein the apparatus is in a frame based equipment (FBE) mode; and sending, to a gNB in the communication channel within a fixed frame period (FFP) associated with the apparatus, a first transmission to initiate, by the apparatus, a first channel occupancy time (COT) within the FFP, the first transmission starting at a beginning of the FFP and ending before an idle period within the FFP; the computer instructions, when executed by one or more processors of an apparatus, further cause the apparatus to perform: receiving information of a time interval T UE COT during which the apparatus is allowed to initiate a periodic COT, the time interval T UE COT including the FFP; the computer instructions, when executed by one or more processors of an apparatus, further cause the apparatus to perform: after sending the first transmission, receiving, from the gNB within a preset time period, an indication indicating that initiation of the first COT by the UE is confirmed or rejected, the indication being carried in a physical downlink control channel (PDCCH), a downlink control information (DCI), or a hybrid automatic repeat request acknowledgement (HARQ ACK); or 48. A non-transitory computer readable medium storing computer instructions, wherein, after sending the first transmission, determining that initiation of the first COT by the UE is confirmed when a downlink transmission is received from the gNB within the time period, or determining that initiation of the first COT is rejected when no downlink transmission is received from the gNB within the time period. the computer instructions, when executed by one or more processors of an apparatus, cause the apparatus to perform: receiving, from a user equipment (UE) in a communication channel of an unlicensed spectrum, a first transmission within a fixed frame period (FFP), the UE being in a frame based equipment (FBE) mode; and in response to the first transmission starting at a beginning of the FFP and ending before an idle period of the FFP, determining, based on the first transmission, that the UE initiates a first channel occupancy time (COT) within the FFP; The computer instructions, when executed by the one or more processors of the apparatus, further cause the apparatus to perform: transmitting, to the UE, information of a time interval T_UE_COT during which the UE is allowed to initiate a periodic COT, the time interval T_UE_COT including the FFP; The computer instructions, when executed by the one or more processors of the apparatus, further cause the apparatus to perform: in response to receiving the first transmission, sending, to the UE within a preset time period, an indication indicating that initiation of the first COT by the UE is confirmed or rejected, the indication being carried in a physical downlink control channel (PDCCH), a downlink control information (DCI), or a hybrid automatic repeat request acknowledgement (HARQ_ACK); or 49. A system, comprising: in response to receiving the first transmission, performing, to the UE within the time period, a downlink transmission to confirm initiation of the first COT, or not performing, to the UE within the time period, a downlink transmission to indicate that initiation of the first COT is rejected. comprise: a user equipment (UE) in a frame based equipment (FBE) mode; and a gNB in communication with the UE, wherein the UE is configured to perform: determining that a communication channel in an unlicensed spectrum is available; and sending, to the gNB in the communication channel within a fixed frame period (FFP) associated with the UE, a first transmission to initiate a first channel occupancy time (COT) by the UE within the FFP, the first transmission starting at a beginning of the FFP and ending before an idle period within the FFP; the UE is further configured to perform: receiving information of a time interval T_UE_COT during which the UE is allowed to initiate a periodic COT, the time interval T_UE_COT including the FFP; the UE is further configured to perform: after sending the first transmission, receiving, from the gNB within a preset time period, an indication indicating that initiation of the first COT by the UE is confirmed or rejected, the indication being carried in a physical downlink control channel (PDCCH), a downlink control information (DCI), or a hybrid automatic repeat request acknowledgement (HARQ_ACK); or after sending the first transmission, determining that initiation of the first COT by the UE is confirmed when a downlink transmission is received from the gNB within the time period, or determining that initiation of the first COT is rejected when no downlink transmission is received from the gNB within the time period; and wherein the gNB is configured to perform: receiving, from the UE in the communication channel of the unlicensed spectrum, the first transmission within the FFP; and in response to the first transmission starting at the beginning of the FFP and ending before the idle period of the FFP, determining, based on the first transmission, that the UE initiates the first COT within the FFP. The gNB is further configured to perform: transmitting, to the UE, information of a time interval T UE COT during which the UE is allowed to initiate a periodic COT, the time interval T UE COT comprising the FFP; The gNB is further configured to perform: in response to receiving the first transmission, sending, to the UE within the time period, the indication indicating that the initiation of the first COT by the UE is confirmed or rejected; or in response to receiving the first transmission, performing, within the time period, a downlink transmission to the UE to confirm the initiation of the first COT, or not performing, within the time period, a downlink transmission to the UE to indicate that the initiation of the first COT is rejected.

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