Method of power saving for XR applications with non-integer traffic periodicity

Abstract

A power saving method implemented in a user equipment (UE) includes monitoring signaling according to a periodic schedule in which a monitoring period having a period length includes an on-duration period during which the UE monitors signaling between the UE and a radio access network (RAN), and an off-duration period during which the UE monitors signaling between the UE and the radio access network (RAN). Communicating a traffic with traffic periodicity with the RAN during the monitoring; and adjusting an alignment between the monitoring and the passing using a timer having a timer duration based on (i) a cycle length, (ii) a traffic periodicity, and (iii) an on-duration period.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of the filing date of Provisional U.S. Patent Application No. 63 / 396,598, entitled “Method of Conducting Power Saving for xR Applications with a Non-integer Traffic Periodicity,” filed on August 9, 2023. The entire contents of the provisional application are hereby expressly incorporated herein by reference. Technical Field

[0003] The present disclosure relates generally to wireless communications, and more particularly to supporting power saving such as discontinuous reception (DRX) when low-latency data such as extended reality (XR) arrives with non-integer periodicity. Background Art

[0004] This background description is provided for the purpose of generally presenting the context of the present disclosure. The work of the presently named inventors, to the extent that it is described in this background section, and aspects of the specification that otherwise may not be considered prior art at the time of filing, are neither explicitly nor implicitly admitted to be prior art to the present disclosure.

[0005] Discontinuous Reception (DRX) is a feature of IoT or MTC devices to reduce power consumption. With the DRX mechanism, a user device can enter a sleep mode for a certain period (e.g., an Off Duration period) and then wake up to monitor DL ​​signals from a base station after the Off Duration period (e.g., an On Duration period). The DRX cycle defines the time interval between two consecutive time periods when the UE is awake.

[0006] One of the main limitations of existing connected mode DRX (C-DRX) designs is that the C-DRX cycle is not aligned with a certain type of traffic (such as augmented reality (AR) / virtual reality (VR) or "extended reality") frame rate. These cycles are integer values, for example, long DRX cycles have durations of 10ms, 20ms, 32ms, 40ms, 60ms, 64ms, etc., and short DRX cycles have durations of 2ms, 3ms, 4ms, 5ms, 6ms, 7ms, 8ms, 10ms, 14ms, 16ms, etc. However, the 3rd Generation Partnership Project (3GPP) participants recently agreed that the packet arrival rate to be evaluated for XR is 30, 60, 90 or 120 frames per second (fps), and therefore the corresponding traffic periodicity for XR can be a non-integer value, such as 33.33ms, 16.67ms, 11.11ms or 8.33ms. For both the long cycle case and the short cycle case, there is a mismatch between the XR traffic arrival periodicity and the C-DRX cycle.

[0007] This misalignment causes a time drift between the arrival of the XR video frame and the start of the C-DRX cycle. The accumulation of time drift then causes the expected arrival time of the XR traffic to fall outside the C-DRX on-duration or the period of time when the receiver is awake and able to receive data. This misalignment causes greater latency in data scheduling and further reduces the XR / CG system capacity.

[0008] Existing methods to address misalignment have certain disadvantages due to additional signaling, frequent changes of DRX cycles, etc. Furthermore, these methods generally do not provide compatibility with devices supporting DRX with only integer periodicity. Summary of the invention

[0009] An example embodiment of the technology of the present disclosure is a power saving method implemented in a user equipment (UE). The method includes: monitoring signaling according to a periodic schedule, in which a monitoring cycle with a period length includes an on-duration period and an off-duration period, during which the UE monitors signaling between the UE and a radio access network (RAN); communicating traffic with traffic periodicity with the RAN during the monitoring period; and adjusting the alignment between monitoring and communicating using a timer with a timer duration, the timer duration being based on (i) the cycle length, (ii) the traffic periodicity, and (iii) the on-duration period.

[0010] Another example embodiment of these techniques is a configuration method implemented in a base station operating in a radio access network (RAN), the method comprising: sending a periodic schedule to a user equipment (UE), the periodic schedule comprising a monitoring period having a period length, the monitoring period having an on-duration period and an off-duration period, during which the UE monitors signaling between the UE and the radio access network (RAN); communicating traffic having traffic periodicity with the UE when the UE monitors the signaling according to the periodic schedule; and configuring the UE to adjust alignment between monitoring and communicating using a timer having a timer duration, the timer duration being based on (i) the period length, (ii) the traffic periodicity, and (iii) the on-duration period.

[0011] Another example embodiment of the techniques is an apparatus comprising a transceiver and a process configured to implement one of the above methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a block diagram of an example wireless communication system in which a device can align monitoring with communication periodicity to achieve power conservation;

[0013] Figure 2A An example DRX cycle is shown;

[0014] Figure 2B An example DRX cycle with a DRX offset is shown;

[0015] Figure 2C shows the misalignment due to non-integer traffic periodicity;

[0016] Figure 2D An example jitter distribution for video traffic is shown;

[0017] Figure 3 is a messaging diagram for an example scenario in which the network modifies the initial configuration of DRX and notifies the UE accordingly;

[0018] Figure 4A is a flow chart of an example network-side method for specifying a DRX cycle in units other than subframes (e.g., OFDM symbols);

[0019] Figure 4B is a flow chart of an example network-side method for providing a DRX configuration and an indication of a non-integer periodicity to a UE;

[0020] Figure 5 is a flow chart of an example network-side method for providing an indication to a UE that the UE should determine a start time of a new DRX cycle based on a time of receipt of the indication;

[0021] Figure 6 is a flow chart of an example network-side method for specifying a timer by which a UE applies adjustments to a DRX cycle.

[0022] Figure 7 is a flow chart of an example UE-side method for receiving an indication of a DRX cycle in units other than subframes (e.g., OFDM symbols);

[0023] Figure 8 is a flow chart of an example UE-side method for determining a start time of a new DRX cycle based on a time at which the UE receives an appropriate indication from a base station;

[0024] Fig. 9 is a flow chart of an example UE-side method for using a timer that may be specified by the network to apply adjustments to a DRX cycle;

[0025] Fig.10 is a flow chart of an example UE-side method for receiving a DRX configuration and an indication of a non-integer periodicity and calculating a timer for adjusting the DRX cycle;

[0026] Fig.11 It is shown that according to Figure 4A and Figure 7 Adjustment of DRX by the method;

[0027] Fig.12 It is shown that according to Figure 6 and Fig. 9 Adjustment of DRX by the method of

[0028] Fig.13 Shows Figure 1 Example techniques for managing jitter that a device may implement.

[0029] Description of the drawings

[0030] A user equipment (UE) and / or a network element such as a base station implements one or more of the techniques discussed below to align the DRX cycle with periodic traffic, thereby allowing the UE to save power. These techniques address the misalignment issue discussed above while reducing signaling between the UE and the network, thereby minimizing the forward or backward shift of the C-DRX cycle relative to the arrival of traffic, which can trade off latency or power consumption, thereby avoiding frequent changes in the offset of the DRX cycle within a frame, and not requiring synchronization between multiple C-DRX configurations.

[0031] As described below, in some implementations, the network sends a DRX offset and an indication of time to the UE, and the UE uses the offset and indication to determine the start of the next DRX cycle. The indication of time uses units other than subframes, such as OFDM symbols. In another implementation, the network sends a message to the UE in a subframe / time slot / symbol, and the UE then changes the start of the DRX cycle based on the frame, subframe, time slot, or symbol in which the UE receives the message. According to this solution, the UE uses the reception time of the message instead of using the offset given by the network to determine the start of the next DRX cycle.

[0032] In yet another implementation, the network configures a timer for the UE, or the UE configures the timer in view of parameters provided by the network to the UE. When the timer expires, the UE updates the start of the next DRX cycle. The network and the UE can use the timer to track when the nominal start of the xR traffic period falls completely outside the DRX on duration period. When the timer expires, the UE autonomously (without commands from the network) changes the start of the next DRX cycle to align with the XR traffic period. In yet another implementation, the UE adjusts the drift every fixed number of C-DRX cycles and applies a fixed offset for each adjustment. In another implementation, the UE further takes into account the C-DRX on duration. As long as the traffic arrival time is still within the on duration, the UE does not correct the drift between the XR traffic arrival and the C-DRX cycle.

[0033] Next reference Figure 1 Example communications systems in which these techniques may be implemented are discussed.

[0034] The example wireless communication system 100 includes a user equipment (UE) 102 and a base station 104 connected to a radio access network (RAN) 105 of a core network (CN) 110. In other implementations or scenarios, the wireless communication system 100 includes more Figure 1 More or fewer UEs, and / or more or fewer base stations are shown in . Base station 103 can be any suitable type of base station, such as, for example, an evolved Node B (eNB), a next generation eNB (ng-eNB), or a 5G Node B (gNB). Base station 104 supports a cell in which base station 104 communicates with UE 102 via a radio access technology such as new radio (NR). For example, although the examples below specifically relate to specific CN types (EPC, 5GC) and RAT types (5G NR and EUTRA), in general, the technology of the present disclosure may also be applicable to other suitable radio access technologies and / or core network technologies, such as sixth generation (6G) radio access and / or 6G core network or 5G NR-6G DC.

[0035] The base station 104 includes a transceiver (not shown) and processing hardware 130, which may include one or more general-purpose processors (e.g., central processing units (CPUs)) and computer-readable memory storing machine-readable instructions executable on the one or more general-purpose processors, and / or special-purpose processing units. Figure 1 The processing hardware 130 in an example implementation of includes an XR timing controller 132 configured to manage, control, or facilitate control of downlink (DL) XR traffic 134 or other low-latency downlink and / or uplink traffic at the UE 102. The XR traffic 134 can be periodic or quasi-periodic.

[0036] UE 102 includes processing hardware 140, which in some implementations includes one or more general-purpose processors (eg, CPUs) and computer-readable memory storing machine-readable instructions executable on the general-purpose processors, and / or special-purpose processing units. Figure 1 The processing hardware 140 in the example implementation of includes a DRX controller 144 that is configured to manage DRX cycles and alignment between the DRX cycles and the traffic 134 .

[0037] The CN 110 may be connected to a streaming server 160 via a wide area network 150 such as the Internet. In some implementations, the CN 110 is an evolved packet core (EPC) or a fifth generation core (5GC). Depending on the implementation, the base station 104 is an eNB supporting an S1 interface for communicating with the EPC, an ng-eNB supporting an NG interface for communicating with the 5GC, or a gNB supporting an NR radio interface and an NG interface for communicating with the 5GC. The RAN 105 is typically a plurality of base stations, and at least some of the base stations may be interconnected via an X2 or Xn interface. The RAN 105 and the CN 110 are collectively referred to as the "network" 108 hereinafter.

[0038] Among other components, the EPC may include a serving gateway (SGW), a mobility management entity (MME), and a packet data network gateway (PGW). The SGW is generally configured to transmit user plane packets related to audio calls, video calls, Internet traffic, etc., and the MME is configured to manage authentication, registration, paging, and other related functions. The PGW provides a connection from a UE (e.g., UE 102) to one or more external packet data networks (e.g., an Internet network and / or an Internet Protocol (IP) Multimedia Subsystem (IMS) network). The 5GC includes a user plane function (UPF) and an access and mobility management (AMF) 164, and / or a session management function (SMF). The UPF is generally configured to transmit user plane packets related to audio calls, video calls, Internet traffic, etc., the AMF is generally configured to manage authentication, registration, paging, and other related functions, and the SMF is generally configured to manage PDU sessions.

[0039] Next, Figure 2A An example DRX cycle 200 is shown that includes an on-duration period 202 and an off-duration period 204, which the UE 102 may use to enter a sleep state, or in any case operate at a reduced power level. The on-duration period 202 and the off-duration period 204 add up to a total length 205 of the DRC cycle 200. For example, the UE 102 may monitor signaling from the base station 104 during the period 202, and generally not monitor signaling from the RAN 105 at all during the period 204, specifically not monitor signaling from the base station 104, or reduce monitoring of signaling. Specifically, during the on-duration period 202, the UE 102 may monitor a physical downlink control channel (PDCCH).

[0040] Figure 2B An example DRX cycle 200 is shown with a DRX offset 206. Figure 3 As discussed, the network 108 may indicate a combination of a length 205 of the DRX cycle 200 and an offset 206. The nominal start of the first DRX cycle 200 is at the first OFDM symbol of the first slot of the first subframe of the first frame. Thus, the offset 206 is the delay between the start of the nominal DRX cycle and the start of the actual DRX cycle, such as Figure 2B shown.

[0041] Figure 2CThe misalignment of the nominal DRX cycle due to non-integer traffic periodicity with the periodic or quasi-periodic traffic 220 is shown. In this example, the bursts 220A, 220B, etc. have a periodicity of approximately 16.67 ms, while the DRX cycle has a period of 16 ms, with an on-duration period of 2 ms. Therefore, the bursts 220A-D fall within the corresponding on-duration periods, while the burst 220E falls outside the on-duration period.

[0042] Figure 2D An example jitter distribution 250 for video traffic is shown. In general, XR and media traffic arrives at the RAN 105 from the CN 110 with jitter. The main source of jitter is the video encoder during the video encoding process, which takes different durations to encode a video frame depending on the frame type, content and size. As a result, the traffic arrival is no longer periodic, but quasi-periodic with random jitter. If the data arrives before the DRX On Duration start time, the jitter causes additional delay to the XR traffic; if the data arrives after the DRX On Duration start time, the jitter causes additional power consumption.

[0043] XR traffic has been modeled using a statistical approach. Specifically, jitter has been modeled as a truncated Gaussian distribution with a 2ms standard deviation and a + / -4ms range, as Figure 2D shown.

[0044] Figure 3 An example scenario 300 is shown in which the network 108 (eg, base station 104 and / or CN 110) modifies the initial configuration of DRX and notifies the UE accordingly.

[0045] The network 108 sends 310 the DRX configuration in a first message, which may be, for example, RRCReconfiguration, RRCSetup, RRCReestablishment, RRCReestablishment, RRCResume, etc. The first message may include a length of the DRX cycle and a first offset used by the UE 102 to determine the start of the DRX cycle. In some implementations, the network 108 sends 310 an indicator indicating a combination of the length of the DRX cycle and the offset such that the nominal start of the first DRX cycle is at the first OFDM symbol of the first slot of the first subframe of the first frame, and the offset is a delay between the start of the nominal DRX cycle and the start of the actual DRX cycle (see Figure 2B ). Figure 4A To Figure B, Figure 7 and Figures 9 and 10 Example information sent by network 108 is discussed.

[0046] UE 102 processes 320 the first message and starts monitoring signaling according to the configuration. For example, UE 102 calculates the start time of the DRX cycle. In one implementation, the start of the short DRX cycle is given by

[0047] [(SFN×10)+subframe number]modulo(drx-ShortCycle)=(final_offset)modulo(drx-ShortCycle) (Equation 1),

[0048] And the starting position of the long DRX cycle is

[0049] [(SFN×10)+subframe number]modulo(drx-LongCycle)=final_offset (Equation 2),

[0050] Wherein, final_offset is the first offset value, SFN is the current system frame number, and subframe number is the current subframe number (ie, 0-9).

[0051] The network 108 sends 330 the DL data traffic to the UE 102. At some point, the network 108 may also send 340 a modification to the DRX configuration in a "second" message. In one implementation, the second message is a MAC PDU. In some implementations, the network 108 sends the second message on a PDCCH addressed to a dedicated RNTI. The UE 102 uses the dedicated RNTI to identify the second message.

[0052] The UE 102 sends 360 a "third" message to acknowledge receipt of the second message. The third message may be a HARQ ACK or a MAC PDU with a field / indicator in a MAC CE or subheader.

[0053] If the network 108 does not receive the third message, it will resend the second message to the UE 102.

[0054] refer to Figure 4A , the network 108 may implement an example method 400A for specifying a DRX cycle in units other than subframes (e.g., OFDM symbols). In general, according to this method, the network 108 sends a DRX offset and a time unit to the UE 102, and the UE 102 uses the offset and the time unit to determine the start of the next DRX cycle. The UE 102 then uses this information to determine the start of the DRX cycle.

[0055] At block 412, the network 108 sends the DRX configuration and an indication of a time unit other than a subframe to the UE 102 in a (first) message. The first message also includes the first time unit or an indicator of the first time unit. Rather than specifying only subframes, the network 108 may use different time units such as one or more of frames, time slots, OFDM symbols, etc., in order to provide better granularity. For example, if the first offset is 10 and the first time unit is one OFDM symbol, the offset is 10 OFDM symbols.

[0056] At block 430 , the network 108 transmits data traffic having a non-integer periodicity, such as, for example, XR traffic.

[0057] Optionally, at block 440, the network 108 sends a command to modify the DRX configuration. For example, the second message may include a second offset or an indicator of the second offset. In another implementation, the second offset is a difference value added to or subtracted from a current offset value. For example, if the current offset is 10 OFDM symbols and the second offset is 5, the final offset is 10+5 symbols.

[0058] The second message may include an indicator indicating whether the second offset is a delta difference or an absolute offset.If the second message does not include the second offset, the UE 102 may use the first offset instead.

[0059] The second message may include a second time unit or an indicator of the second time unit. Similar to the first time unit, the second time unit may be one or more of a frame, a subframe, a time slot, an OFDM symbol, etc. For example, the second time unit may be 2 time slots. The UE applies the second time unit to the second offset. If the second message does not include the second time unit, the UE uses the first time unit instead.

[0060] The second message may include a first field / indicator that instructs UE 102 to use a second offset and / or a second time unit to calculate the start of the DRX cycle. For example, if the first field / indicator is set to a predefined value, UE 102 uses the second offset and / or the second time unit to calculate the start of the DRX cycle.

[0061] In one implementation, the second message is a MAC PDU including a MAC subheader. According to the NR MAC specification, the MAC PDU may include a single MAC subheader or a pair of MAC subheaders and a MAC CE. The MAC subheader also includes a logical channel ID that distinguishes it from other MAC subheaders. The MAC subheader may include a dedicated logical channel ID that distinguishes it from other MAC subheaders. The MAC subheader includes a first field / indicator. A MAC CE associated with the MAC subheader in the same MAC PDU may include a second offset and a second time unit.

[0062] Figure 4B is a flow chart of an example network-side method for providing a DRX configuration and an indication of a non-integer periodicity to a UE;

[0063] Next, Figure 5 An example 500 method for providing an indication to a UE that the UE should determine the start time of a new DRX cycle based on the time of receipt of the indication is shown. The method 500 may also be implemented in the network 108. Generally speaking, the method involves the network sending a message to the UE in a subframe / time slot / symbol, and then the UE changes the start of the DRX cycle based on the frame / subframe / time slot / symbol in which the UE receives the message. In this solution, the UE uses the reception time of the message instead of using an offset given by the network to determine the start of the next DRX cycle.

[0064] Figure 6 An example method 600 is shown for specifying a timer by which a UE applies adjustments to a DRX cycle, which method may also be implemented in the network 108. The method generally requires the network to configure a timer for the UE. When the timer expires, the UE autonomously changes the start of the next DRX cycle. The timer tracks when the nominal start of the xR traffic period falls completely outside the DRX On Duration period. When the timer expires, the UE autonomously changes the start of the next DRX cycle to align with the xR traffic period.

[0065] At block 602, the network 108 calculates a timer value, which may be a multiple of an XR traffic period. Optionally, the network 108 associates the timer value with one or more channels and / or one or more bearers. At block 614, the network 108 then sends a message ("first message") to the UE 102 and includes the DRX configuration and the timer value in the message. At block 630, the network 108 sends or forwards traffic with a non-integer periodicity to the UE 102.

[0066] The first message may include a first length value of the first timer or an indicator of the first length of the first timer. When the timer expires, the UE 102 may change the start of the next DRX cycle to align with the xR traffic period. Otherwise, the next nominal xR period falls outside the DRX on duration, such as Figure 2C shown.

[0067] In one example implementation, the length of the first timer is one or more XR traffic periods. For example, if the nominal start of the 4th XR traffic period falls outside the DRX on duration, the length of the first timer may be 3 times the XR traffic periodicity. When the first timer expires, the UE 102 changes the start of the next DRX cycle.

[0068] As described above, the first timer may be associated with a channel (eg, a logical channel or a radio bearer) or a group of channels.

[0069] In another implementation, the first message includes a first periodicity (e.g., 16.67 ms, 11.11 ms, 8.33 ms) of the data traffic (or an indicator / index associated with the first periodicity). Using the first periodicity and the DRX configuration (i.e., DRX cycle length, on-duration length) included in the first message, the UE 102 can derive a first length value.

[0070] Specifically, if nx(periodity-DRX-cycle-length)>=(on-duration-time-length-diff), the first length value will be nx period, where n is the smallest integer that satisfies the equation. The difference may be a constant given in the first message or may be predefined. For example, the difference may be the jitter of the XR traffic arrival time. In another implementation, n is the smallest integer that satisfies the inequality minus a predefined integer value. In yet another implementation, the network 108 indicates the value of n in the first message.

[0071] The product (n xperiodicity) may not correspond to an integer number of subframes, but in most systems the on-duration period always starts at the beginning of a subframe.Thus, the first length value may be an upper or lower bound on the product (n xperiodicity).

[0072] In another implementation, the first length value is set to (n x drx-cycle-length) instead of the product (n x period). Since drx-cycle-length is an integer number of subframes, the product (n x drx-cycle-length) is also an integer number of subframes. The UE 102 can use a second counter to count time / subframes.

[0073] For example, see Fig.12 , the DRX cycle length (DRX-cycle-length) in scenario 1200 is 6; the on-duration-time-length (on-duration-time-length) is 2; and the XR data periodicity is 7. Therefore, n=2, because 2x 6+2<=2x 7, and 2 is the smallest integer that satisfies the above inequality. Therefore, the first length value will be 2x 7=14.

[0074] Furthermore, the first message may include a time unit or an indicator of a time unit.The time unit may be applied to the first length value.

[0075] In some implementations, the network 108 sends a second message to the UE 102. Specifically, the network 108 may change the length of the first timer by including a second length value (or an indicator of the second length value) in the second message. The second message may also include a time unit of the second length value (or an indicator of the time unit). The UE 102 may (re)start the first timer having a length derived from the second length value and / or the time unit. In other implementations, the network 108 changes the periodicity of the data traffic.

[0076] In another embodiment, the UE 102 receives the second message at time t. The second message contains a command requiring the UE to (re)start the On-Duration at time t or time t+N, where N is predefined or included in the first message.

[0077] In another embodiment, the second message includes a third field / indicator, which instructs UE102 to restart / stop the first timer. For example, if the third field / indicator is set to a predefined value, UE102 restarts / stops the first timer.

[0078] In some implementations, the second message is a MAC PDU including a MAC subheader. The MAC subheader may contain a logical channel ID that distinguishes it from other MAC subheaders in the same MAC PDU.

[0079] In one implementation, the MAC subheader includes a third field / indicator. In one implementation, a MAC CE associated with a MAC subheader in the same MAC PDU includes a second length value and its time unit. In another implementation, the second message is a DCI addressed to a unique RNTI. The RNTI may be provided in the first message.

[0080] Figure 7 An example method 700 is shown for receiving an indication of a DRX cycle in units other than subframes (eg, OFDM symbols). The method 700 may be implemented in the UE 102 or another suitable UE.

[0081] At block 710, the UE 102 receives the DRC configuration and an indication of the time unit. At block 722, the UE 102 uses the indication to configure the DRX cycle. In one implementation, the UE 102 uses equations (1) and (2) above for the time unit of slots, OFDM symbols, etc. by converting subframes into slots or OFDM symbols. For example, for the time slot time unit, equation (1) becomes [(SFN×10+subframe number)×number_of_slots_per_subframe]modulo(drx-ShortCycle×number_of_slots_per_subframe)=(final_offset×number_of_slots_per_subframe)modulo(drx-Short Cycle×number_of_slots_per_subframe), and the start of the long DRX cycle is given by [(SFN×10+subframe number)×number_of_slots_per_subframe]modulo(drx-LongCycle×number_of_slots_per_subframe)=final_offset×number_of_slots_per_subframe, where final_offset is the first / second offset value.

[0082] At block 730, the UE receives traffic according to the DRX cycle.

[0083] Optionally, at block 740, the UE receives a modification to the DRX configuration, including a new offset and / or a new time unit. At block 750, the UE applies the received modification. The UE 102 uses the second offset and the second time unit to determine the start of the DRX cycle. For example, the UE 102 performs step 320 (see Figure 3) to calculate the start of the next DRX cycle.

[0084] Figure 8 is a flow chart of an example UE-side method for determining a start time of a new DRX cycle based on the time at which the UE receives an appropriate indication from a base station.

[0085] Here, at block 842, UE 102 receives a "second" message containing a second field / indicator (see Figure 3 ), the second field / indicator instructs UE 102 to use the reception time of the second message to calculate the start of the DRX cycle. For example, if the second field / indicator is set to a predefined value, UE 102 should change the start of the DRX cycle based on the reception time of the second message.

[0086] In one implementation, the second message is a MAC PDU including a MAC subheader. The MAC subheader may include a logical channel ID that distinguishes it from other MAC subheaders. The MAC subheader may include a second field / indicator. In an implementation, a MAC CE associated with a MAC subheader in the same MAC PDU includes an offset and a time unit. The UE 102 uses the reception time, the offset, and the time unit to calculate the start of the DRX cycle.

[0087] The UE may use the time at which it receives the second message to obtain the start time of the next DRX cycle. The network 108 may configure an offset for the UE 102. For example, the start of the next DRX cycle is the Pth subframe / time slot / symbol after the end of reception of the second message, where P is predetermined or given in the first message (i.e., semi-static) or the second message (i.e., dynamic). The P value included in the second message overrides the P value in the first message.

[0088] Fig. 9 9 is a flow chart of an example method 900 for using a (first) timer that may be specified by the network to apply an adjustment to a DRX cycle. The method 900 may be implemented, for example, in a UE 102. The method 900 begins at block 912, where the UE 102 receives a DRX configuration and a timer value. At block 915, the UE 102 starts a timer at the beginning of the DRX cycle. At block 930, the UE 102 receives traffic according to the DRX cycle. At block 950, when the timer expires, the UE 102 applies the adjustment to the DRX cycle. The UE 102 may also restart the timer, and the flow may return to block 930.

[0089] Specifically, after UE 102 receives the first message, UE 102 may restart the first timer. For example, if UE 102 receives the first message at time t, UE 102 starts the first timer at the start of the next DRX cycle after time t. UE 102 may derive the start of the next DRX cycle from the first offset included in the first message. In another embodiment, UE 102 starts the first timer at time t.

[0090] When the first timer (or counter) expires, the UE 102 changes the start of the next DRX cycle. For example, if the first timer expires in subframe / time slot / symbol M, the UE changes the start of the next DRX cycle to subframe / time slot / symbol M+N, where N is predetermined (e.g., N=0) or given in the first message. The UE 102 then calculates a new DRX offset. For example, the new DRX offset is the difference between the start of the nominal DRX cycle and the new start of the next DRX cycle. The UE 102 uses this new DRX offset to determine the start of the remaining DRX cycles.

[0091] In another implementation, the first message includes a first increment value (or an indicator of the first increment value). The first increment value is associated with a first length value. When the first timer expires, the UE 102 uses the first increment value to calculate a new DRX offset. For example, the UE 102 adds the first increment value to the current DRX offset and then uses the new DRX offset to determine the start of the remaining DRX cycles. In another implementation, the first increment value is derived from a first periodicity given in the first message. The first increment value may be given by ((periodicity–drx-cycle-length)*n).

[0092] Reference again Fig.12 , the length of the DRX cycle is 6, and the length of the on-duration is 2. The length of the periodicity of the xR traffic is 7. The first DRX offset is 0, and the first increment value is 2. When the first timer expires, the UE 102 calculates a new DRX offset using the first increment value. The new DRX offset is the current DRX offset plus the increment value, so the new DRX offset is therefore 0+2. The UE 102 uses this new DRX offset value to determine the start of the next DRX cycle. Similarly, after the first timer expires again, the UE 102 calculates a new DRX offset, which is 2+2.

[0093] For example, the UE 102 may use the following formula to determine when to start the on-duration timer:

[0094] [(SFN×10)+subframe number]modulo(drxCycle)=(DRXOffset+(m×delta)-const)modulo(drxCycle) (Equation 3),

[0095] Wherein, whenever the first timer expires, m is increased by 1, and const can be used to cover jitter. Const can be predefined or provided in the first message. In another implementation, at the end of the nth DRX cycle, in response, UE 102 increases m by 1 every n DRX cycles.

[0096] If delta(Δ) is a non-integer, take the upper limit of (m*delta) or lower limit The equation accordingly becomes:

[0097] [(SFN×10)+subframe number]modulo(drx-Cycle)=(drx-StartOffset+floor(m×delta))modulo(drx-Cycle) (Equation 4)

[0098] In addition, the UE 102 can solve the SFN cycle wrapping problem by modifying the equation to the following:

[0099] [(sfc×10)+subframe number]modulo(drx-Cycle)=((drx-StartOffset)+ceiling(m×delta))modulo(drx-Cycle)) (Equation 5)

[0100] Among them, sfc (system frame counter) is set to the current SFN when DRX is configured, and then increases by 1 whenever the SFN changes.

[0101] In another implementation, the UE 102 derives the first increment value from the first periodicity. Specifically, the first increment value is (first periodicity-DRX cycle length) xn. Fig.12 In the example of , the first increment value is (7-6)x 2=2.

[0102] When the first timer expires, the UE 102 (re)starts the first timer. The expiration of the first timer serves as a trigger to regularly adjust the start of the DRX cycle.

[0103] Furthermore, when the first timer expires, the UE 102 (re)starts the drx-onDurationTimer. The UE 102 uses the drx-onDurationTimer timer to determine the "on-duration" of the DRX cycle, during which time it should monitor the PDCCH for downlink allocations or uplink grants.

[0104] In another implementation, the UE 102 is configured with a first DRX configuration and a second DRX configuration. When the first DRX configuration is activated, i.e., the UE 102 is using the first DRX configuration, and when the first timer expires, the UE 102 activates the second DRX configuration, i.e., the UE 102 switches to the second DRX configuration. The on-duration of the second DRX configuration covers the nominal start of the XR traffic.

[0105] After UE 102 receives the second message, UE 102 also (re)starts the first timer. For example, UE (re)starts the first timer with a timer length derived from the second length value and its time unit given in the second message.

[0106] After the UE receives 102 the second message, the UE changes the start of the next DRX cycle.

[0107] In one embodiment, if UE 102 receives the second message in subframe / time slot / symbol M, the UE changes the start of the next DRX cycle to subframe / time slot / symbol M+N, where N is predetermined or given in the first message or the second message. Then, UE 102 calculates a new DRX offset. For example, the new DRX offset is the difference between the start of the current nominal DRX cycle described in item 1.1.2 and the new start of the next DRX cycle described in this item. UE 102 uses this new DRX offset to determine the start of the remaining DRX cycles.

[0108] In another embodiment, the second message includes a second offset (or an indicator associated with the second offset) used by the UE to determine the start of the next DRX cycle. The second message may include the time unit of the second offset. The UE uses the second offset to calculate the start of the remaining DRX cycles.

[0109] After UE 102 receives the second message, the UE starts the first timer at the beginning of the next DRX cycle.

[0110] When the first timer expires, the UE 102 (re)starts the first timer. The expiration of the first timer serves as a trigger to regularly adjust the start of the DRX cycle.

[0111] In the second message, the network 108 includes a second increment value. The second increment value is associated with the second length value. If the first timer expires, the UE 102 uses the second increment value to calculate a new DRX offset. For example, the UE 102 adds the first increment value to the current DRX offset and then uses the new DRX offset to determine the start of the remaining DRX cycles.

[0112] In another embodiment, the network 108 sends the second increment value in the first message. The network 108 then sends an indicator of the second length value. When the UE 102 receives the indicator of the second length value, the UE 102 uses the second increment value to calculate a new DRX offset.

[0113] Further discussion

[0114] ● Option 1:

[0115] In this option, the system adjusts for drift every fixed number of C-DRX cycles and uses a fixed offset for the adjustment. For example, for frame rate = 30fps (33.33ms periodicity) and drx-Cycle = 32, the adjustment will be made every 3 cycles with an offset equal to 4.

[0116] It is proposed to introduce three new parameters:

[0117] ○drx-CyclesAdjust: The number of cycles to apply the correction shift

[0118] ○drx-CyclesOffset: offset value applied every drx-CyclesAdjust cycle

[0119] ○drx-CorrectionCounter: counter used to apply the offset

[0120] And apply the following algorithm:

[0121] 1. Increment the counter:

[0122] drx-CorrectionCounter=0;

[0123] if(([(SFN×10)+subframe number]modulo[(drx-CorrectionCounter+1)×drx-CyclesAdjust×drx-Cycle]=drx-CorrectionCounter×drx-CyclesOffset)&&[(SFN×10)+subframe number-drx-StartOffset>0])

[0124] drx-CorrectionCounter=drx-CorrectionCounter+1;

[0125] 2. Start of the opening duration:

[0126] [(SFN×10)+subframe number]modulo(drx-Cycle)=(drx-StartOffset+[drx-CorrectionCounter×drx-CyclesOffset])modulo(drx-Cycle), where SFN is the current system frame number and subframe number is the current subframe number.

[0127] This formula is evaluated as Case 1 and Case 2 in Appendix B-1.

[0128] Introducing drx-Cycle=33 can further reduce the residual error, as shown as Case 3 in Appendix B-1.

[0129] The gNB can use the frame rate irreducible fraction to determine drx-CyclesAdjust and drx-CyclesOffset.

[0130] For example, if frame rate = 30fps and drx-Cycle = 32:

[0131] ○

[0132] ○drx-CyclesAdjust=3

[0133] ○drx-CyclesOffset=100-drx-CyclesAdjust×drx-Cycle=4

[0134] ● Option 2:

[0135] In this option, it is suggested to consider the C-DRX On-Duration and there is no need to correct the drift between XR traffic arrival and C-DRX cycle as long as the traffic arrival time is still within the On-Duration.

[0136] A timer is introduced, and when the timer expires, the system applies the correction for the drift. The timer duration is t = (n × periodicity), where n is the smallest integer that satisfies the following inequality: (n × drx-Cycle + On-Duration) ≤ (n × periodicity)

[0137] Therefore, the formula can be written as:

[0138] [(SFN×10)+subframe number]modulo(drx-Cycle)=((drx-StartOffset)+ceiling(m×Δ))modulo(drx-Cycle))

[0139] Where Δ = n × (periodicity-drx-Cycle), and m is incremented every n drx-Cycles.

[0140] This formula is evaluated as Case 4 in Appendix B-1.

[0141] NOTE 1: A new C-DRX cycle is defined for XR traffic.

[0142] ●FFS: 9ms, 11ms, 17ms, 33ms, 34ms.

[0143] FFS: Round XR traffic periodically up or down to the nearest integer (if not already supported)

[0144] NOTE 2: Equation 38.321 is reused with some modifications for the start of the on-duration timer.

[0145] NOTE 3: For the start of the on-duration timer, one of the following two recommended formulas is used:

[0146] ● Option 1:

[0147] 1. Increment the counter:

[0148] drx-CorrectionCounter=0;

[0149] if(([(SFN×10)+subframe number]modulo[(drx-Correction Counter+1)×drx-CyclesAdjust×drx-Cycle]=drx-CorrectionCounter×drx-CyclesOffset)&&[(SFN×10)+subframe number-drx-StartOffset>0])

[0150] drx-CorrectionCounter=drx-CorrectionCounter+1;

[0151] 2. Start of the opening duration:

[0152] [(SFN×10)+subframe number]modulo(drx-Cycle)=(drx-StartOffset+[drx-CorrectionCounter×drx-CyclesOffset])modulo(drx-Cycle), where SFN is the current system frame number and subframe number is the current subframe number.

[0153] ● Option 2:

[0154] 1. Update the timer and increment the counter:

[0155] ■t = (n × periodicity), where n is the smallest integer that satisfies the following inequality:

[0156] (n×drx-Cycle+On-Duration)≤(n×periodicity)

[0157] ■Δ=n×(periodicity-drx-Cycle), and every n drx-Cycles, m is incremented

[0158] 2. Start of the opening duration:

[0159] [(SFN×10)+subframe number]modulo(drx-Cycle)=((drx-StartOffset)+ceiling(m×Δ))modulo(drx-Cycle))

[0160] NOTE 1: A two-stage C-DRX configuration is used to handle jitter.

[0161] NOTE 2: If coarse C-DRX cycle and fine C-DRX cycle are used for jitter, a non-uniform on-duration pattern is adopted for the fine C-DRX cycle to match the jitter distribution.

[0162] ● Adjust the C-DRX On Duration based on traffic arrival. The adjustment can be an extension, e.g. if no data is received during the On Duration, PDCCH monitoring is performed for an additional duration after the On Duration ends

[10] . The adjustment can also be an early termination, e.g. stopping the On Duration at the first data arrival and then relying on an inactivity timer [9].

[0163] ● Implicit SSSG switching based on data reception: After data arrival, the UE can implicitly switch from sparse PDCCH monitoring to dense PDCCH monitoring within the DRX on duration [3][8].

[0164] C-DRX enhancements for multiple XR traffic flows

[0165] XR traffic consists of multiple data streams such as video, audio, gesture / control information, haptics, etc. These streams have different traffic characteristics (periodicity, offset, packet size, etc.) and different QoS requirements.

[0166] The use of multiple simultaneously active C-DRX configurations to support multi-stream XR traffic has been discussed in RAN1#109e

[11] . The main motivation is to reduce UE power consumption by having a dedicated and optimized C-DRX configuration per XR traffic flow. For example, different C-DRX configurations can be configured for video streams, audio streams, and haptic streams. Even further, different C-DRX configurations can be used for I frames and P frames.

[0167] Dynamic Adaptation of C-DRX Configuration

[0168] Dynamic adaptation of C-DRX configuration parameters (on-duration, inactivity timer, start offset) has been mentioned in RAN1#109e

[11] .

[0169] While this technique can help address jitter and periodic alignment issues, it requires the network to have prior knowledge about the jitter of the traffic burst arriving in the next C-DRX opportunity. This requires the network to obtain instant information about jitter from the XR server / video codec or the network to make jitter predictions.

[0170] Summary of options:

[0171] Note 1: A new C-DRX cycle is defined for XR traffic:

[0172] ●FFS: 9ms, 11ms, 17ms, 33ms, 34ms.

[0173] FFS: Includes rounding XR traffic periodically up or down to the nearest integer (if not already supported)

[0174] NOTE 2: Equation 38.321 is reused with some modifications for the start of the on-duration timer.

[0175] NOTE 3: For the start of the on-duration timer, one of the following two recommended formulas is used:

[0176] ● Method 1:

[0177] 1. Increment the counter:

[0178] drx-CorrectionCounter=0;

[0179] if(([(SFN×10)+subframe number]modulo[(drx-Correction Counter+1)×drx-CyclesAdjust×drx-Cycle]=drx-CorrectionCounter×drx-CyclesOffset)&&[(SFN×10)+subframe number-drx-StartOffset>0])

[0180] drx-CorrectionCounter=drx-CorrectionCounter+1;

[0181] 2. Start of the opening duration:

[0182] [(SFN×10)+subframe number]modulo(drx-Cycle)=(drx-StartOffset+[drx-CorrectionCounter×drx-CyclesOffset])modulo(drx-Cycle), where SFN is the current system frame number and subframe number is the current subframe number.

[0183] ● Method 2:

[0184] 1. Update the timer and increment the counter:

[0185] ■t = (n × periodicity), where n is the smallest integer that satisfies the following inequality:

[0186] (n×drx-Cycle+On-Duration)≤(n×periodicity)

[0187] ■Δ=n×(periodicity-drx-Cycle), and every n drx-Cycles, m is incremented

[0188] 2. Start of the opening duration:

[0189] [(SFN×10)+subframe number]modulo(drx-Cycle)=((drx-StartOffset)+ceiling(m×Δ))modulo(drx-Cycle))

[0190] NOTE 4: A two-stage C-DRX configuration is used to handle jitter.

[0191] NOTE 5: If coarse C-DRX cycle and fine C-DRX cycle are used for jitter, a non-uniform on-duration pattern is adopted for the fine C-DRX cycle to match the jitter distribution.

[0192] The following description can be applied to the above description.

[0193] The user device (e.g., UE 102) in which the technology of the present disclosure can be implemented can be any suitable device capable of wireless communication, such as a smart phone, a tablet computer, a laptop computer, a mobile game console, a point of sale (POS) terminal, a health monitoring device, a drone, a camera, a media streaming dongle or another personal media device, a wearable device such as a smart watch, a wireless hotspot, a femtocell or a broadband router. Further, in some cases, the user device can be embedded in an electronic system, such as a head unit (headunit) or an advanced driver assistance system (ADAS) of a vehicle. Further, the user device can be operated as an Internet of Things (IoT) device or a mobile Internet device (MID). Depending on the type, the user device may include one or more general-purpose processors, a computer-readable memory, a user interface, one or more network interfaces, one or more sensors, etc.

[0194] Certain embodiments are described in the present disclosure as including logic or multiple components or modules. A module may be a software module (e.g., a code or machine-readable instruction stored on a non-temporary machine-readable medium) or a hardware module. A hardware module is a tangible unit that is capable of performing certain operations and can be configured or arranged in a particular manner. A hardware module may include a dedicated circuit system (circuitry) or logic that is permanently configured to perform certain operations (e.g., as a dedicated processor, such as a field programmable gate array (FPGA) or an application-specific integrated circuit (ASIC), a digital signal processor (DSP), etc.). A hardware module may also include programmable logic or circuit systems (e.g., as contained in a general-purpose processor or other programmable processor) that are temporarily configured by software to perform certain operations. The decision to implement a hardware module with a dedicated and permanently configured circuit system or with a temporarily configured circuit system (e.g., configured by software) can be driven by cost and time considerations.

[0195] When implemented in software, the techniques may be provided as part of an operating system, a library used by multiple applications, a specific software application, etc. The software may be executed by one or more general-purpose processors or one or more special-purpose processors.

Claims

1. A power saving method implemented in a user equipment (UE), the method comprising: monitoring signaling according to a periodic schedule, wherein a monitoring cycle having a cycle length comprises an on-duration period and an off-duration period, during which the UE monitors signaling between the UE and a radio access network (RAN); communicating traffic having traffic periodicity with the RAN during the monitoring period; and Alignment between the monitoring and the delivering is adjusted using a timer having a timer duration based on (i) the cycle length, (ii) the flow periodicity, and (iii) the on-duration period.

2. The method of claim 1, wherein: The adjusting of the alignment comprises: When the start of the monitoring period coincides with the start of the flow period, starting a timer; and In response to expiration of the timer, a correction is applied to realign the monitoring period with the period of the traffic.

3. The method of claim 2, further comprising: The correction is received from the RAN.

4. The method of claim 3, wherein: The correction is received together with a configuration for the monitoring of the signaling.

5. The method of claim 3, wherein: Said correction is received in a dedicated message after receiving a configuration for said monitoring of said signalling.

6. The method according to any one of the preceding claims, further comprising: The timer duration is set to an integer multiple of the traffic periodicity.

7. The method of claim 6, wherein: The setting of the timer duration comprises setting n to a minimum integer value satisfying the following: (n*drx_Cycle+On-Duration)≤(n*t_periodicity), in, The timer duration is t, The integer multiple is n, The on-duration is On-Duration. The cycle length is drx_Cycle, and The traffic periodicity is t_periodicity.

8. The method of claim 7, further comprising: The correction (Δ) is determined according to: in, The system frame number is SFN. The subframe number is SF_num, The monitoring period is offset by drx_startOffset, and The counter incremented every n instances of the monitoring cycle is m.

9. A method as claimed in any one of the preceding claims, wherein: The monitoring and the communicating correspond to connected mode discontinuous reception (C-DRX).

10. The method of any one of the preceding claims, further comprising: The timer duration is received from the RAN.

11. A configuration method implemented in a base station operating in a radio access network (RAN), the method comprising: sending a periodic schedule to a user equipment (UE), the periodic schedule comprising a monitoring period having a period length, the monitoring period having an on-duration period and an off-duration period, during which the UE monitors signaling between the UE and the radio access network (RAN); communicating traffic having traffic periodicity with the UE when the UE monitors the signaling according to the periodic scheduling; as well as The UE is configured to adjust the alignment between the monitoring and the delivering using a timer having a timer duration based on (i) the cycle length, (ii) the traffic periodicity, and (iii) the on-Duration period.

12. The method of claim 11, wherein: The configuration includes: At least one of: (i) the timer duration or (ii) a correction to realign the monitoring period with a period of the traffic is sent to the UE.

13. The method of claim 12, wherein: The at least one of the timer duration and the correction is sent with the periodic schedule.

14. The method of claim 12, wherein: The at least one of the timer duration and the correction is sent in a dedicated message subsequent to the sending of the periodic schedule.

15. A device comprising: Transceiver; as well as Processing hardware configured to implement a method according to any one of the preceding claims.

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