SYSTEMS AND METHODS FOR TDMA RANDOM ACCESS IN AMBIENT INTERNET OF THINGS (IoT)

Abstract

In accordance with implementations, a wireless device (e.g., an AIoT device) selects a transmission occasion from a first transmission occasion and a second transmission occasion for transmission of a first message. A first transmission offset for the first transmission occasion equals a time offset. A second transmission offset for the second transmission occasion equals a sum of the time offset scaled by a first factor and a duration of the first message scaled by a second factor. The wireless device transmits the first message at a transmission offset after an end of a received message. The transmission offset is the second transmission offset in accordance to the transmission occasion being the second transmission occasion.

Description

Systems and Methods for TDMA Random Access in Ambient Internet of Things (IoT) CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This patent application claims priority to U.S. Provisional Application No. 63 / 703,050, filed on October 3, 2024, and entitled “Methods for TDMA Random Access in Ambient Internet of Things (IoT),” U.S. Provisional Application No.63 / 717,587, filed on November 7, 2024, and entitled “Methods for TDMA Random Access in Ambient Internet of Things (IoT),” and U.S. Provisional Application No.63 / 765,360, filed on February 28, 2025, and entitled “Methods for TDMA Random Access in Ambient Internet of Things (IoT),” applications of which are hereby incorporated by reference herein as if reproduced in their entireties. TECHNICAL FIELD

[0002] The present disclosure relates generally to wireless communications, and, in particular embodiments, to systems and methods for Ambient IoT random access. BACKGROUND

[0003] In the study for Ambient Internet of Things (AIoT), there are several use cases involving AIoT devices (e.g., devices supporting AIoT technology) and readers (e.g., devices that manage the AIoT devices). Readers can include gNBs or intermediate nodes, which can be UEs supporting the AIoT interface. Readers and AIoT devices were described in technical report (TR) 38.848, (Sep.2023 “Study on Ambient IoT (Internet of Things) in RAN (Release 18)”). Four topologies described are shown in FIGs.1A-1E. FIG.1A illustrates Topology 1. FIG.1B illustrates Topology 2. FIG.1C illustrates Topology 3 with downlink assist. FIG.1D illustrates Topology 3 with uplink assist. FIG.1E illustrates Topology 4. Uu can represent a cellular link in the figures.

[0004] In a deployment, there may be hundreds of AIoT devices present. Using the density of 1.5 devices per square meter mentioned in TR 38.848 as an example, in a circular region having a radius of 10 meters, there may be about 470 devices. The number of devices, plus the underlying intent of devices relying on energy harvesting and having poor quality clocks, presents design challenges. For example, inventorying the devices (e.g., identifying the devices) may require a significant amount of time given the number of devices and whether a device is available (e.g., having enough energy to communicate). FW 6000734PCT04 1

[0005] An example of an inventory procedure is shown in FIG.2, from the 3GPP contribution R2-2407985, “Report of [POST127]

[0033] [AIoT] Random Access,” “Figure 2.2.3-1 The overall framework example of slotted ALOHA random access.” In FIG.2, there is an AIoT paging message sent on a reader to device (R2D) link in a physical reader to device channel (PRDCH). An access round can start with an “R2D Round trigger” message sent on the PRDCH. There may be a trigger to start one or more access occasions (transmission occasion). The access occasions can be occasions both in time and / or frequency. A messaging sequence can be where a device selects a transmission occasion to send a first message (e.g., AIoT Msg-1) on the physical device to reader channel (PDRCH). A reader may respond by sending a second message (e.g., AIoT Msg- 2) on the PRDCH. A device may subsequently transmit a third message (e.g., AIoT Msg- 3) on the PDRCH.

[0006] With the large number of devices, eliminating some signaling overhead can reduce the amount of time a reader uses to complete the inventory. With time division multiple access (TDMA), there can be M transmission occasions in time after each R2D trigger. For generality, there may be N occasions in frequency for each transmission occasion in time. FIG.3 shows M=4 occasions starting from 0 to M-1, for example. The earliest in time transmission occasion is transmission occasion 0 while the latest is transmission occasion 3 (i.e., M-1). In many systems, a device can select (or be scheduled) a specific transmission occasion to transmit its message. The duration of the message Tmis generally shorter compared to the duration of the transmission occasion. The duration of the transmission occasion should be just large enough to have message transmissions in one transmission occasion (e.g., transmission occasion 0) not overlapping with message transmissions in the next transmission occasion (e.g., transmission occasion 1). SUMMARY

[0007] Technical advantages are generally achieved, by implementations of this disclosure which describe methods, apparatus, and system.

[0008] In accordance with implementations, a wireless device (e.g., an AIoT device) selects a transmission occasion from a first transmission occasion and a second transmission occasion for transmission of a first message. A first transmission offset for the first transmission occasion equals a time offset. A second transmission offset for the second transmission occasion equals a sum of the time offset scaled by a first factor and a duration of the first message scaled by a second factor. The wireless device transmits the first message at a transmission offset after an end of a received message. The FW 6000734PCT04 2transmission offset is the second transmission offset in accordance to the transmission occasion being the second transmission occasion.

[0009] In some implementations, a first sum of the time offset and the duration of the second transmission offset may equal a second sum scaled by the second factor. The second sum may be of the time offset and the duration of the first message.

[0010] In some implementations, the received message may be a reader to device (R2D) trigger message.

[0011] In some implementations, the wireless device may receive an indication of a number of transmission occasions available for transmission of the first message following the end of the received message. The wireless device selecting the transmission occasion may be in response to the number of transmission occasions being greater than one.

[0012] In some implementations, the wireless device may select the transmission occasion randomly based on the number of transmission occasions.

[0013] In some implementations, the received message may be an R2D trigger message. The R2D trigger message may include the indication of the number of transmission occasions.

[0014] In some implementations, the first factor may be greater than 1, and the second factor may be greater than 1.

[0015] In some implementations, the first factor and the second factor may be the same.

[0016] In some implementations, the second factor may be a first sum of 1 and a term related to a device type. The term may be 0.25 for a first device type when a number of transmission occasions is 2.

[0017] In some implementations, the first factor may be different from the second factor.

[0018] In some implementations, the transmission offset may be the first transmission offset in accordance to the transmission occasion being the first transmission occasion.

[0019] In some implementations, a first duration of the first transmission occasion may be the duration of the first message scaled by the second factor.

[0020] In some implementations, the wireless device may select the transmission occasion from the first transmission occasion, the second transmission occasion, and a FW 6000734PCT04 3third transmission occasion. A third duration of the third transmission occasion may be greater than a second duration of the second transmission occasion. The second duration may be greater than a first duration of the first transmission occasion.

[0021] In accordance with implementations, a reader device transmits a message to an AIoT device. The reader device monitors a first transmission occasion for a transmission of a first message from the AIoT device based on a time offset after an end of the message. The reader device monitors a second transmission occasion for the transmission of the first message from the AIoT device based on a sum of the time offset scaled by a first factor and a duration of the first message scaled by a second factor after the end of the message. In response to receiving the first message from the AIoT device, the reader device transmits to the AIoT device a second message after the second transmission occasion.

[0022] In some implementations, a first sum of the time offset and the duration of a second transmission offset may equal a second sum scaled by the second factor, the second sum being of the time offset and the duration of the first message.

[0023] In some implementations, the message may be a reader to device (R2D) trigger message.

[0024] In some implementations, the reader device may transmit to the AIoT device an indication of a number of transmission occasions available for transmission of the first message following the end of the message.

[0025] In some implementations, the message may be an R2D trigger message, and the R2D trigger message may include the indication of the number of transmission occasions.

[0026] In some implementations, the first factor may be greater than 1, and the second factor may be greater than 1.

[0027] In some implementations, the first factor and the second factor may be the same.

[0028] In some implementations, the second factor may be a first sum of 1 and a term related to a device type. The term may be 0.25 for a first device type when a number of transmission occasions is 2.

[0029] In some implementations, the first factor may be different from the second factor.

[0030] In some implementations, a first duration of the first transmission occasion may be the duration of the first message scaled by the second factor. FW 6000734PCT04 4

[0031] In some implementations, the reader device may monitor a third transmission occasion. A third duration of the third transmission occasion may be greater than a second duration of the second transmission occasion. The second duration may be greater than a first duration of the first transmission occasion.

[0032] This disclosure can provide technical solutions to address timing synchronization challenges in AIoT devices having poor clock accuracy due to high sampling frequency offset (SFO). The described technique can use unequal duration transmission occasions to prevent message collisions at the reader. Instead of fixed- duration time slots, the described technique can calculate progressively longer transmission occasion durations based on the cumulative timing errors from devices with fast and slow clocks. This technical solution can allow multiple AIoT devices to transmit after a trigger message while accounting for their clock drift, reducing signaling overhead compared to traditional one-transmission-per-trigger methods. The reader may provide timing parameters to the AIoT devices, enabling the devices to select appropriate transmission occasions and calculate precise transmission times despite the devices’ clock inaccuracies. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] For a more complete understanding of the present disclosure, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

[0034] FIGs.1A-1E illustrate topologies of Ambient IoT connectivity, in accordance with some implementations;

[0035] FIG.2 illustrates an example inventory procedure, in accordance with some implementations;

[0036] FIG.3 illustrates example time division multiplexed transmission occasions, in accordance with some implementations;

[0037] FIG.4 illustrates example time division multiplexed transmission occasions with guard time, in accordance with some implementations;

[0038] FIG.5 illustrates an example baseline case of a contention-based procedure, in accordance with some implementations;

[0039] FIG.6 illustrates an example case of equally spaced 4 transmission occasions per R2D Trigger Message, in accordance with some implementations; FW 6000734PCT04 5

[0040] FIG.7A shows the timing of the time division multiplexed Msg-2’s received at the reader using equal duration transmission occasion, in accordance with some implementations;

[0041] FIG.7B shows the timing of transmission occasion at device and reader, in accordance with some implementations;

[0042] FIG.8 shows additional time for M successive transmission occasions for different values of fe, in accordance with some implementations;

[0043] FIG.9 shows comparison of time per transmission occasion for the TDMA with equal duration transmission occasion case and the baseline case, in accordance with some implementations;

[0044] FIG.10 illustrates an example case of 4 unequal duration transmission occasions per R2D Trigger Message, in accordance with some implementations;

[0045] FIG.11 shows the timing of the time division multiplexed Msg-2’s received at the reader using unequal duration transmission occasion, in accordance with some implementations;

[0046] FIG.12 shows comparison of time per transmission occasion for the TDMA with unequal transmission occasions case and the baseline case, in accordance with some implementations;

[0047] FIG.13 illustrates an example contention procedure for a device, in accordance with some implementations;

[0048] FIG.14 illustrates an example contention procedure for a reader, in accordance with some implementations;

[0049] FIG.15 shows an example of scheduling a device for transmission, in accordance with some implementations;

[0050] FIG.16A shows an example of timing relationships, in accordance with some implementations;

[0051] FIG.16B shows examples of AIoT Msg-2 relationships, in accordance with some implementations;

[0052] FIG.16C shows examples of enabling different types of devices (X=1 only and X>1) to perform contention based access, in accordance with some implementations;

[0053] FIG.16D shows an example of timing at the reader, in accordance with some implementations; FW 6000734PCT04 6

[0054] FIG.17 shows an example timing diagram for multiple transmission occasions for Message 1 (Msg1) following an R2D message, in accordance with some implementations;

[0055] FIG.18 shows an example timing diagram at a reader for X>2 devices, in accordance with some implementations;

[0056] FIG.19A shows a flow chart of a method performed by an AIoT device, in accordance with some implementations;

[0057] FIG.19B shows a flow chart of a method performed by a reader device, in accordance with some implementations;

[0058] FIG.20 illustrates an example wireless communication system, in accordance with some implementations;

[0059] FIG.21 illustrates an example communication system, in accordance with some implementations;

[0060] FIGs.22A and 22B illustrate example devices, in accordance with some implementations; and

[0061] FIG.23 shows a block diagram of a computing system, in accordance with some implementations.

[0062] Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated. The figures are drawn to clearly illustrate the relevant aspects of the embodiments and are not necessarily drawn to scale. DETAILED DESCRIPTION

[0063] With relatively poor clock accuracy (e.g., high sampling frequency offset (SFO)), the clock drifts in an AIoT device (also may be called a device in this disclosure). For example, for a frequency error (fe), which can be related to the SFO, the timing inaccuracy may be represented by t×fe after a duration of time t. There can be devices with slow clocks where the actual duration is t×(1+fe) when the device perceives that t seconds has elapsed, and there can be devices with fast clocks, where the actual duration is t×(1-fe) when the device perceives that t seconds has elapsed. Typical approaches of fixed duration transmission occasions can be used. But the technical problem is how to determine the duration of the transmission occasions to avoid collisions at the reader, where a collision is when the reception of a message from an transmission occasion overlaps with a message from an earlier or later transmission occasion. A common approach is to allocate guard time, as shown in FIG.4, which allows FW 6000734PCT04 7transmissions to exceed the boundary of the transmission occasion. This solution is typically used to address timing misalignment due to propagation delay (e.g. time alignment), not to address different clock rates.

[0065] Alternatively, new durations of transmission occasions can be considered, where the durations of each transmission occasion are not equal. This disclosure describes technical solutions to determine the durations as well as means to operate such a system.

[0066] In the example AIoT inventory use case, to initiate an inventory session, the reader sends out a paging command (e.g., AIoT paging in FIG.2 (“AIoT Msg-0”)), informing the devices to respond by transmitting an AIoT Msg-1 on one out of many possible transmission occasions using a contention-based procedure. In one embodiment, an AIoT Msg-0 may contain information such as a range of device IDs requested to participate in the contention procedure, an identification number for this particular paging round, and configurations such as the number of transmission occasions provisioned per R2D trigger message, parameters for calculating the duration of each transmission occasion, etc. In one example, during a contention-based procedure, a device ID can be a random integer. The number of transmission occasions may depend on the population of devices PT to be inventoried. In slotted-ALOHA, the highest throughput is achieved when the average message arrival rate for each slot is 1. This can be achieved by setting the probability for a device to transmit at a particular slot to be the inverse of the number of devices expected to transmit in the paging round, which can consist of Naccessaccess rounds. In one example, the first paging round is able to inventory P1 devices. In the next paging round may attempt to inventory PT-P1 devices. In one embodiment, the R2D Round Trigger Message may contains a number P, which can be an upper limit of a range from which a device selects a random number. P can represent the number of transmission occasions provisioned in this particular access round. For example, PT≤ Naccess×P. In another example, PT≥ Naccess×P. If P is a good estimate of the number of devices that will attempt to transmit in this particular access round, a high throughput could be achieved. In another implementation, the R2D Trigger Message may contain additional information such as the identification numbers for the paging round and the access round. An R2D Trigger Message initiates M time division multiplexed transmission occasions. Typically, M is much smaller than P, therefore, multiple (Ntrigger) R2D Trigger Messages are used per access round to complete the P transmission occasions provisioned for the access round. For example, P=M×Ntrigger. In one implementation, the size of the R2D Trigger Message is minimized to contain only information to identify itself as an R2D Trigger Message. In another FW 6000734PCT04 8embodiment, the R2D Trigger Message may include a sequence number identifying itself within the access round. In another implementation, it may also include a number identifying the access round it belongs to.

[0067] An additional benefit of TDMA is the opportunity to improve device availability. Since AIoT devices have limited energy storage, and the time to harvest energy from the environment (e.g., using photovoltaic cells, capturing kinetic energy, capturing radio frequency (RF) energy) can be on the order of tens of seconds for certain harvesting techniques, when a device is not scheduled to perform transmissions and receptions, the device can become unavailable and harvest energy. With TDMA, there can be short spans of time when a device should be unavailable. As an example, if PT= 1000 devices, the paging round can be divided into Naccess=10 access rounds of P=100 devices each. If a device is active in one access round, it can become unavailable for the nine other access rounds. Without TDMA, a device may monitor 100 R2D transmissions in an access round. It is possible that a device may not have enough energy to monitor 100 R2D transmissions. With TDMA, assuming M=5 transmission occasions in time after each R2D trigger, there are 20 R2D triggers in an access round. A device may monitor up to 20 R2D triggers (on average 10 triggers). Thus, instead of monitoring up to PT=1000 R2D transmissions, a device can monitor NaccessR2D round triggers and 20 R2D triggers (a total of 30 R2D transmissions). This approach can allow a device to be available for a short span of time and possibly harvest energy during the unavailable time. There may be other approaches to partition the transmission occasions (e.g., varying M, varying P) by the device type.

[0068] Implementations to support a 2-step contention-based procedure as well as a 3-step contention-based procedure are described in this disclosure.

[0069] In a two-step contention-based procedure, the first message, AIoT Msg-A, sent by the device contains information from the device requested by the reader for inventory purposes, such as the full device ID, not a random integer. After successful detection of the device’s AIoT Msg-A transmission, the reader sends out an AIoT Msg-B in response (such as an acknowledgement (ACK)).

[0070] For a 3-step contention-based procedure, an AIoT Msg-1 sent by the device may be minimal in size and may contain a random number that functions as a temporary ID. Upon successful detection of the device’s AIoT Msg-1, the reader sends out an AIoT Msg-2 that can include the temporary ID received from AIoT Msg-1. This message can indicate resources for the detected device to send further information for the inventory procedure, such as the full device ID. The detected device then responds with the requested information (e.g., AIoT Msg-3). FW 6000734PCT04 9

[0071] As a baseline, the case, where only one transmission occasion in time is provisioned for the R2D Trigger Message, is shown in FIG.5. The reader initiates one transmission occasion by transmitting an R2D Trigger message 500. If an AIoT Msg-1 501 is successfully detected, the reader transmits an AIoT Msg-2502 to request further information from the detected device. The detected device transmits the requested information in an AIoT Msg-3503. The reader may transmit an acknowledgement 504 of successful reception. The reader then sends out another R2D Trigger Message 510 to announce the next transmission occasion. If the reader failed to detect an AIoT Msg-1 511, the reader can send out another R2D Trigger Message 520 to announce the next transmission occasion. If after detecting successfully an AIoT Msg-1521 from a device and sending an AIoT Msg-2522 to request information from this device, the reader failed to receive an AIoT Msg-3523 containing the requested information, the reader can send another R2D Trigger Message 530 without sending an acknowledgement. This process can continue until all the transmission occasions provisioned for the access round are completed.

[0072] The total time spent for transmission of only R2D Trigger Messages and AIoT Msg-1’s can be determined. Assume overall P transmission occasions are used to inventory all the devices in the access round. Each transmission occasion involves transmission of one R2D Trigger Message and one AIoT Msg-1. Let the time for transmitting an R2D Trigger Message be ^^^, which includes the time to transmit the message and the transition time between an R2D Trigger Message and an AIoT Msg-1, for example, the time a device uses to process the R2D Trigger Message and to switch from receive to transmit. Note the minimum time is denoted as TR2D_min. Let the time for transmitting an AIoT Msg-1 be ^^^at the nominal clock rate of a device. However, the devices may generally have poor clock accuracy due to power and complexity constraints. The time for receiving an AIoT Msg-1 should accommodate the worst-case clock accuracy. Let the worst sampling clock offset (SFO) at the device be ^^, then themaximum time to transmit an AIoT Msg-1 should be at least ^^^^1 + ^^^. In the 3GPPAIoT discussions, the maximum SFO is about 105ppm, or ^^=0.1. Therefore, the timeper transmission occasion is ^^^^ = ^^^ + ^^^^1 + ^^^.

[0073] In another implementation, multiple transmission occasions in time are provisioned after each R2D Trigger Message transmission, the multiple transmissionoccasions have equal durations in time, and the duration is ^^ = ^^^^ + ∆^, as shown inFIG.6 for 4 transmission occasions per R2D Trigger Message. The value ∆ can be considered as a guard time. Due to the SFO, when a device’s clock is running faster than the nominal value, and its AIoT Msg-1 would arrive earlier than expected, while an AIoT FW 6000734PCT04 10Msg-1 from a device with slower clock would arrive later. The duration between the transmission occasions should be greater than ^^^to avoid collisions at the reader between AIoT Msg-1’s from different transmission occasions. As shown in FIG.6, the limiting factor is the collision between the earliest AIoT Msg-1 for the last transmission occasion and the latest AIoT Msg-1 for the second to last transmission occasion. Based on this observation, the following equations can be used to find the minimum value for ^^.

[0074] Let the number of transmission occasions per R2D Trigger Message be M, to avoid a collision between the earliest AIoT Msg-1 for the last transmission occasion and the latest AIoT Msg-1 for the second to last transmission occasion, the following equation can be satisfied: ^^ − 1^^^^1 − ^^^ ≥ ^^ − 2^^^^1 + ^^^ + ^^^^1 + ^^^

[0075] From which, the minimum transmission occasion duration is: ^^ ≥ ^^^− 2^^ ^^ −

[0076] Equivalently, inis 2^^ − 1^^∆≥ ^^1 + ^ ^ ^ ^ ^^^^ − 2 ^ − 1 ^^duration of a transmission occasion Ts, can provide the number of transmission occasions (M) after an R2D Trigger Message, and assumes a device transmits at the start of the transmission occasion. Alternatively, a reader can provide a list of M transmission occasion starting times. For example, if M=4, the following table indicates when an AIoT Msg-1 is received at the reader from a device with a fast clock and a device with a slow clock. The values in Table 1 assume the start time for the first occasion is 0. The equations can support a non-zero starting value, as described later. Table 1. Time when AIoT Msg-1 is received at reader with equal duration transmission occasions. Event Device with fast clock Device with slow clock 0FW 6000734PCT04 11End of 1st^^^^1 − ^^^ ^^^^1 + ^^^trans. ^^^

[0078] Table 2 provides a numeric evaluation of the formulas in Table 1. Table 2. Start of each transmission occasion at the reader for M=4. For the numeric values, it is assumed that Tm1=1 and fe=0.05, which results in Ts=1.4. Starting Device with Device withFW 6000734PCT04 123rd 2.66 2.94 trans.

[0079] FIG.7g n occasions. Regardless of the clock speed, a device transmits its message at a start of a transmission occasion (e.g., at any one of the four occasions). Since a reader has an accurate clock, a reader can know the starting time of each transmission occasion for devices with the fastest clock and the ending time of each transmission occasion for devices with the slowest clock. Note that the devices with frequency errors between –feand fecan be received without collisions at the reader. FIG.7A also shows each transmission occasion at a reader. In general, each transmission occasion begins with the expected start of a transmission from a device with a fast clock and ends with the expected end of a transmission from a device with a slow clock. There may be a span of time where no transmissions are expected (as indicated by the cross-hatched boxes). For the last transmission occasion, a reader may decide that the duration of the last transmission occasion is after the expected end of a transmission from a device with a slow clock. Alternatively, the reader may want a longer duration of the last transmission occasion. One example is the duration of the last transmission occasion is based on the expected end of the last transmission occasion for the device with a slow clock. The cross-hatched boxes can be considered guard time. At the reader, the duration of guard time becomes smaller. From a device perspective, the guard time is the same in each transmission occasion.

[0080] Fig.7B shows an alternate depiction of a transmission occasion of duration Ts at a device. The transmission occasion is partitioned into a duration of time Tm1for AIoT Msg-1 (e.g., a time domain resource) and a guard time of duration Tg. This guard time can be different for each transmission occasion or even zero. Fig.7B also shows a transmission occasion of duration Ts′ at a reader, where Ts′ ≥Ts. This transmission occasion consists of a window of time to receive AIoT Msg-1 from device with clock rate between the fastest clock and slowest clock. There may be a guard time (e.g., time gap) of duration Tg′, which can be different for each transmission occasion or even zero. The reader may not expect to receive signals from devices in this guard time. FW 6000734PCT04 13

[0081] When considering the time difference between M consecutive transmission occasions and M non-consecutive transmission occasions (the overhead of the R2D Trigger Message transmission between each transmission occasion is not considered), the difference is ^^ + ∆ ^1 + ^ ^ − ^ ^ 2^^^ ^^ ^ − 1 ^^^^ ^ ^^^^ 1 + ^^ = 2^ ^^^1 ^ ^^ − 1^

[0082] in FIG.8.

[0083] With a small value for fe (fe=0.01), for M=7, one additional time unit of Tm1 may be needed. As feincreases, the additional time rapidly increases for same values of M.

[0084] One benefit of TDMA is the overhead for the R2D Trigger Message can be reduced. For example, assume the duration for the R2D Trigger Message is Tm1 for the non-TDMA case and is 2Tm1 for the TDMA case. With M transmission occasions, a duration MTm1may be needed for the R2D Trigger Message for the non-TDMA case, resulting in a time savings of (M-2)Tm1 for the R2D Trigger Message. Further analysis, such as the average time, and possible values for R2D Trigger Message durations can be considered.

[0085] Then the minimum average time per transmission occasion for the TDM case is ^^^ + ^^ − 1^^^^1 + ^^^ + ^^^^1 + ^ ^^ = ^^^^ ^^^

[0086] case with the baseline case, the ratio^^ !vers^#"^^ "us M for a few different values of^#!and ^^=0.1 or 510 ppm is shown inis the same for the baseline case and the TDMA case. With this ratio of time per transmission occasion between TDMA and baseline case, a lower value is better. As shown in FIG.9, the gainfrom multiplexing more transmission occasions per AIoT Msg-0 depends on the value of^#"^#!, the longer the duration of the trigger message is relative to AIoT Msg-1, the greaterthe gain. At^#" = 0.5, the best performance is obtained for M=2 at ^^ ! ^#"^^ " =92%, at ^#! =FW 6000734PCT04 141, for M=2 at ^^ !^^ " = 82% and at ^#"^#! = 2, for M=3 at ^^ !^^ "=71%. The performanceoccasion is not 0, at least a time ^^'(_^*+after the reception of the R2D message. This time allows for the processing of the R2D message, preparation of the AIoT Msg-1, and potentially the provisioning of the external carrier wave (CW) signal (e.g., if the CW is radiated by an CW node, the CW node transmits the CW at the appropriate time without interfering with the reception of R2D message). In this case, to avoid collision between the earliest AIoT Msg-1 for the last transmission occasion and the latest AIoT Msg-1 for the second to last transmission occasion, the following equation can be satisfied: (note for generality,Tmin is used and is at least ^^'(_^*+).^^ − 1^^ ^1 − ^^^ + ^^ ^^^ ≥ ^^ − 2^^^^1 + ^^^ + ^^^^1 + ^^^ + ^^*+^1 + ^^

[0088] From the above equation, the minimum transmission occasion duration is the following. ^1 + ^ ^^ ^ ^^^ + 2^^^^*+^ ≥1 − ^2^ − 3^^^

[0089] Equivalently, in terms of ∆, its minimum value is the following. 2^^ − 1^^^^^ + 2^ ^∆≥ ^ ^ ^*+1 − ^2^ − 3^^^

[0090] So compared tooccasion starting at 0, the first transmission occasion now starts at ^^*+, and the duration of the transmission occasions is increased by an additional amount of',-^#. / ^0^'102^,-.

[0091] An alternate approach using anthe starting times of each transmission occasion using the design guidelines is presented below. It is assumed that Tmin represents a minimum time from the end of the R2D transmission and the start of the first transmission occasion. The guard time is given by ∆. In this example, a reader can provide to the device, Tminand the start of each transmission occasion. For the reader, let sfc(k) and efc(k) represent the starting and ending times of the kth transmission occasion for a device with a fast clock (fc), k≥0. Then, the following algorithm can be used. The guard time ∆ can be different for each transmission occasion, which can make the durations of the transmission occasions unequal at the device. sfc(0) = Tmin*(1 - fe) efc(k) = (1 - fe)*Tm1+sfc(k), (k≥0) FW 6000734PCT04 15sfc(k) = efc(k-1) + ∆*(1 - fe), (k>0)

[0092] Similarly, let ssc(k) and esc(k) represent the starting and ending times of the kth transmission occasion for a device with a slow clock (sc). Then, the reader can determine the times for the slow clock as: ssc(0) = Tmin*(1 + fe) esc(k) = (1 + fe)*Tm1+ssc(k), (k≥0) ssc(k) = esc(k-1) + ∆*(1 + fe), (k>0)

[0093] For the device, the timing is Tmin, Tmin+Ts, Tmin+2*Ts, …, Tmin+(M-1)*Ts. For M transmission occasions per trigger message, to avoid a collision between AIoT Msg-1 in the Mth slot from a device with a fast clock and AIoT Msg-1 in the (M-1)th slot from a device with a slow clock, sfc(M) ≥ esc(M-1), which leads to an expression for the minimumvalue of ∆. It can be shown that this minimum guard gap value is ∆≥ '^10^^,-^#!3',-^#. / ^0^'102^,- .

[0094] In another implementation, the performance for theimproved by considering unequal duration transmission occasions. As shown in FIG.10, the duration between the earlier transmission occasions can be shortened compared to the equal duration case to reduce the time per transmission occasion further. For each occasion, its duration to the previous transmission occasion is such that the earliest arriving AIoT Msg-1 does not collide with the latest arriving AIoT Msg-1 of the previous transmission occasion.

[0095] Based on such a constraint, the following equations to obtain the durations^^^4^, 4 = 1,2, … , ^ − 1 can be used. Let the time of each transmission occasion be^7^4^, 4 = 1,2, … , ^, ^^^4^ = ^7^4 + 1^ − ^7^4^. Both ^^^4^ and ^7^4^ are timing from thedevice’sThe actual transmit time of the device depends on the SFO of the device. To avoid a collision between the earliest AIoT Msg-1 for the current transmission occasion and the latest AIoT Msg-1 for the previous transmission occasion can be the following. ^7^4^^1 − ^^^ ≥ ^7^4 − 1^^1 + ^^^ + ^^^^1 + ^^^

[0096] Therefore, the minimum duration for the kthoccasion can be the following. 1+^ ^4^ = ^ ^ ^ ^ ^ ^^ ^ ^^^ 7 4 + 1 − ^7 4 = ^ 4 − 11 − ^^

[0097] If the starting time for the first transmission occasion is 0, i.e., ^7^1^ = 0, then^ ^3,-7^2^^1 − ^^^ ≥ ^^^^1 + ^^^, or ^^^1^ = ^7^2^ = ^^^.FW 6000734PCT04 16

[0098] The time for M transmission occasions is presented in Table 3, which indicates when an AIoT Msg-1 is received at the reader from a device with a fast clock and a device with a slow clock. The values in Table 3 assume the starting time for the first occasion is 0. If it is a non-zero value, then the values will be shifted. The equations can support a non-zero value. Table 3. Time when AIoT Msg-1 is received at reader with unequal duration transmission occasions EventDevice with fast clock Device with slow Delta clock ^'^^2

[0099] FIG.11 shows the timing at a reader for M=4 transmission occasions. Regardless of the clock speed, a device transmits its message at a start of a transmission occasion (e.g., at any one of the four occasions). Since a reader has an accurate clock, a reader can know the starting time of each transmission occasion for devices with the fastest clock and the ending time of each transmission occasion for devices with the FW 6000734PCT04 17slowest clock. The devices with sampling frequency errors between –fe and fe can be received. At the reader, the duration of transmission occasion increases, but there is no minimum guard time (it can be added). However, the minimum guard time from the device’s perspective increases (it is not-decreasing)

[0100] For this formulation, from the perspective of the device, the separation between successive transmission occasions increases exponentially with the index of transmission occasions. Let ^7^1^ = 0, then ^^^1^ = ^^^1 + ^^^, the minimum averagetime per occasion is the following. ^+ ^ ^^ + 1^ ^ ^ 1 − ^ 1 + ^ 1^ = ^^ 7 ^^ ^^ ^ ^ ^ ^^^' ^ =^ +^ 1 + ^^ ^2^ ^ ^^1 − ^ ^ − 1^^ ^

[0101] occasions case with the baseline case, the ratio^^ 8^^ "versus M for a few different assumptions on the value of^#"^#!and ^^=0.1 ppm is shown in FIG.12, assumingthat the R2D Trigger Message duration is the same for the baseline case and the TDMAcase. As shown in FIG.12, gain from multiplexing more transmission occasions per R2D Trigger Message is much improved compared to the case of TDMA with equal duration transmission occasion. The performance still depends on the value of^#"^#!, the longer an AIoT Msg-0 is relative to AIoT Msg-1, the greater the gain. At^#"^#! = 0.5, thebest performance is obtained for M=2 at^^ 8^^ " = 92%, at ^#"^#! = 1, forat ^^ 8^^ " = 81%^#" ^^ 8itsequal duration transmission occasions case.

[0102] Typically, the transmit time for the first transmission occasion is not 0, rather atime ^^*+ after the reception of the R2D message. In this case, ^7^1^ = ^^*+ ≥ ^^'(_^*+,according to the previous equation, ^7^2^^1 − ^^^ ≥ ^7^1^^1 + ^^^ + ^^^^1 + ^^^.Therefore, ^^1^ = ^ ^2^ ^ ^ ^3,- ',-9 7 − ^7 1 = ^0,- ^^^ + ^0,- ^^*+.

[0103] Based onas below. ^^3, '7^2^ = - ^^^ + ,- ^^*++ ^7^1^= ^3,- ^ ',- ^3,-^^ + + 1; ^^*+ = ^^^*+ + ^^^^0, the first transmission occasion now starts at ^^*+, the duration of the first transmission FW 6000734PCT04 18occasion is increased by the amount',-^0,-^^*+. The duration of subsequent occasions stillgrows exponentially according to equation: ^^^4^ = ^^^4 − 1^ ^3,-^0,-.

[0105] An alternate approach using an algorithm to time ofeach transmission occasion using the design guidelines is It is assumed that Tmin represents a minimum time from the end of the R2D transmission and the start of the first transmission occasion. For the device, let sdev(k) and edev(k) represent the starting and ending time of the kth transmission of AIoT Msg-1. For the reader, let sfc(k) and efc(k) represent the starting and ending times for a device with a fast clock (fc), k≥0. Similarly, let ssc(k) and esc(k) represent the starting and ending times for a device with a slow clock (sc). The guard time from the device’s perspective for each transmission occasion is given by d(k). Compared to the case of equal transmission occasion duration where there is a constant guard time ∆, the guard time here could be different for each transmission occasion.

[0106] Then, the time at the device can be expressed as the following. sdev(0) = Tmin edev(k) = Tm1+sdev(k), (k≥0) sdev(k) = edev(k-1) + d(k-1), (k>0)

[0107] And the time at the reader for both types of clocks can be expressed as the following. sfc(0) = Tmin*(1 - fe) ssc(0) = Tmin*(1 + fe) efc(k) = (1 - fe)*Tm1+sfc(k), (k≥0) esc(k) = (1 + fe)*Tm1+ssc(k), (k≥0) sfc(k) = efc(k-1) + d(k-1)*(1 - fe), (k>0) ssc(k) = esc(k-1) + d(k-1)*(1 + fe), (k>0)

[0108] To avoid a collision in each transmission occasion, sfc(k)≥ esc(k-1), which leads to an expression for the minimum value of d(k). 2^<^4^ ≥ ^ ^=>^?^4^ + ^^^^, 4 ≥ 0.

[0109] For example,(1)≥ esc(0), leads to aminimum value for <^0^ ≥ ',-^0,- ^^^*+ + ^^^^.FW 6000734PCT04 19

[0110] In this formulation, the guard time <^4^ can be chosen to be any value no smaller than its corresponding minimum value. If the minimum value is chosen for each transmission occasion, the formula derived in the previous approach is obtained.

[0111] In addition to reducing the amount of time for an R2D Trigger Message and an AIoT Msg-1 transmission, time multiplexing multiple transmission occasions per R2D Trigger Message transmission also has the benefit of reducing the number of R2D Trigger Messages the device monitors and decodes, which could have the benefit of conserving energy or equivalently improving device availability. This benefit increases with M, the number of transmission occasions multiplexed. It is observed that in the case of TDMA with unequal duration transmission occasions, higher values of M can be used without significantly degrading the time resource efficiency.

[0112] The contention-based procedure for a device being inventoried in one implementation is shown in FIG.13. At the operation 1301, the device receives at least one message with configuration information which can include M, the number of transmission occasions provisioned per R2D Trigger Message transmission. It is possible the number of transmission occasions after the trigger message is the same or can be different for each trigger message. For the latter, the device can be provided with the number of transmission occasions corresponding to the trigger message. The configuration information can include a starting time for each transmission occasion, or durations of each transmission occasion. Alternatively, parameters to compute the starting time for each transmission occasion can be provided. In some implementations, the start time of the first transmission occasion may be a non-zero value ^^*+or ^^*+=0.

[0113] As described above, the device may receive a list (or equivalently a table of entries) that indicates the starting time of each transmission occasion (or equivalently the starting time for each AIoT Msg-1 transmission after an R2D trigger). For example, the list can be {Tmin, TB[2], TB[3], …, TB[M], Tnext_R2D}. The value Tnext_R2D can indicate when the corresponding AIoT Msg-2 is expected and may not be provided. There is an agreement to define TD2R_max which is a maximum time between an AIoT Msg-1 and a corresponding AIoT Msg-2. A device may determine an expected starting time for AIoT Msg-2 using the sum of TB[M], TD2R_max, an expected duration of AIoT Msg-1, and an expected guard time. Since the durations of transmission occasions are generally non- decreasing, the difference between TB[M] and TB[M-1] includes the expected duration of AIoT Msg-1 and the last guard time, and may be used in the determination. Using a list allows a reader to generalize the durations of transmission occasions. For example, the first M-1 transmission occasion can be equal in duration while the last transmission FW 6000734PCT04 20occasion can be larger. In another example, each duration can differ based on other criteria (e.g., linear).

[0114] There may be multiple lists based on the device types, the value M (e.g., there are 3 transmission occasions for one R2D trigger, and 4 transmission occasions for a different trigger), D2R chip rate, etc. There may also be a smaller set of lists where a multiplicative factor can be used to generate the appropriate time values. A D2R chip rate can indicate the clock rate for the D2R transmission (e.g., AIoT Msg-1). A high chip rate means that the duration of AIoT Msg-1 is shorter. As described in the examples with equal and unequal duration transmission occasions, the duration of the transmission occasion is proportional to the duration of AIoT Msg-1. Hence, a multiple factor related to the chip rate can be applied to a list to determine the starting times for the chip rate.

[0115] At the operation 1302, after the device receives an R2D trigger message, the device may decide to transmit an AIoT Msg-1. There may be criteria for the transmission such as whether a device has a temporary ID within a range.

[0116] At the operation 1303, the device determines a number R which can correspond to one of the transmission occasions. For example, 0 ≤ R < M or 1 ≤ R ≤ M. The value R can be determined from a random number generator, based on the temporary ID (e.g., R=temporary ID mod M), or other means.

[0117] At the operation 1304, the device transmits the AIoT Msg-1 in the Rthtransmission occasion (i.e., start of the occasion). The start of the Rthtransmission occasion can be provided from the M starting times, which can be provided in theconfiguration message. Alternatively, when the durations of each transmission occasion^^^4^, for k=1, …, M, are provided, the start of the kth occasion TB(k) can be ^7^4^ =^7^4 − 1^ +1^, for k=1,…,M, ^^^0^ = 0, and ^7^0^ = ^^*+. The device may also

[0118] At the operation 1305, the device monitors the PRDCH for the AIoT Msg-2 for a response to the device’s AIoT Msg-1. If a response is received, then the device proceeds to transmit the AIoT Msg-3; otherwise, it waits for the next access round (or trigger round). The time when the AIoT Msg-2 can be expected can be related to the transmission occasion selected. For example, if the duration of all the transmission occasions is D (TNext_R2D), a device may wait for D-TB(R).

[0119] Inthe transmission time for a transmission occasion after receiving an R2D Trigger Message is calculated based on additional parameters in the configuration. In operation 1301 of FIG.13, additional parameters ^^^1^ and ^ are received. ^^^1^ is the duration of the first transmission occasion, and ^ is a multiplicative FW 6000734PCT04 21incremental factor related to the maximum SFO ^^of the device determined by thestandards through the formula ^ = ',-^0,-. The multiplicative incremental factor ^ may be apredefined constant (e.g., the standards and hard-coded in the AIoTdevice). Thus, receiving the multiplicative incremental factor ^ may be implemented by retrieving the hard-coded predefined constant for ^ stored in the AIoT device. In operation 1304, the following recursive formula can be used to calculate the starting time of the kthtransmission occasion ^7^4^.a. Let transmission occasion duration be ^^^4^, starting time be ^7^4^, 4 = 1,2, … , ^b. ^7^1^ and ^^^1^ are known constants.c. ^7^4^ = ^7^4 − 1^ + ^^^4 − 1^d. ^^^4^ = ^1 + ^^ × ^^^4 − 1^

[0120] To simplify the calculation for a device with a limited processing capability, a multiplicative factor ^ can be chosen such that the multiplication can be accomplished bysimple shift+add. For example, ^ = ^ can accomm ^A odate fe up to 0.11, ^ = B canaccommodate fe up to 0.059.

[0121] The procedure at a reader (e.g., gNB, scheduling entity) is shown in FIG.14. At the operation 1401, the reader transmits at least one message with configuration information which can include M, the number of transmission occasions provisioned per R2D Trigger Message transmission. It is possible the number of transmission occasions after the trigger message is the same or can be different for each trigger message. For the latter, the device could be provided the number of transmission occasions corresponding to the trigger message. The configuration information can include a starting time for each transmission occasion, or durations of each transmission occasion. Alternatively, parameters to compute the starting time for each transmission occasion can be provided.In some instances, the start of the first transmission occasion may be a non-zero value^^*+ or ^^*+=0. In general, in the operation 1401, a reader provides the configurationinformation about when a device(s) can transmit.

[0122] At the operation 1402, the reader sends a signal / message. For example, the message can be a trigger message. In another message, the reader sends a message providing scheduling information for one or more of the transmission occasions. The scheduling information can be for one or more devices. A device can be scheduled to transmit on more than one transmission occasion. It is possible that a reader indicates the number of transmission occasions following the signal / message. FW 6000734PCT04 22

[0123] At the operation 1403, the reader receives no, one, or possibly overlapping transmissions on each transmission occasion. For example, with overlapping transmissions, a reader may be unable to successfully receive (process) the messages. In one example, with the contention-based access, two or more devices are transmitting their AIoT Msg-1 in the same transmission occasion. Even with different clocks, the two or more AIoT Msg-1 interfere (collide) at the receiver of the reader. With the contention- based access, it is possible that no device transmits on a particular transmission occasion. With scheduling, it is possible not to schedule any device to transmit on a particular transmission occasion. In such situations, it may be possible to reduce the number of transmission occasions that follow the signal / message. Likewise, due to the timing errors, the later transmission occasions may not be scheduled.

[0124] At the operation 1304, the reader processes signals in each of transmission occasions. For each transmission occasion, the reader may be able to successfully decode (receive) the signal. The reader may decide to respond to the successfully received signal with another transmission. For the contention-based access, a reader may receive an AIoT Msg-1. The reader may obtain the contents of AIoT Msg-1 (or even associate the particular transmission occasion with a device or the contents). The reader may decide to transmit an AIoT Msg-2 that includes the contents and possibly provide scheduling information for an AIoT Msg-3. The processing of transmission occasion k-1 can occur while the reader is receiving transmission occasion k.

[0125] The duration of a transmission occasion or a start of a transmission occasion can be an integer representing a number of clock samples. For example, in Table 2, the duration of transmission occasion is 1.4 Tm1. Assuming the reference clock is a sampling rate of 1 / 3,072,000 seconds and Tm1is one millisecond (ms) for a certain D2R chip rate, a transmission occasion is 1.4 ms. This corresponds to 4,300 clock samples. There may be quantization effects (rounding / truncations). A reader may provide the integer 4,300 or a fraction representing 4,300, such as 430x, where x represents 10 clock samples.

[0126] The implementations are applicable to systems supporting slotted ALOHA with devices having large timing errors (e.g., due to high SFO) and any time division multiplexing system (e.g., slots) with devices having large timing errors. The system may comprise at least one wireless transmit / receive unit (WTRU) and at least one device. The implementations show that the network side (e.g., reader or WTRU) can provide parameter(s) describing the duration of each transmission occasion (e.g., slot) so that a device can be scheduled to transmit in a particular slot or select a slot among a group / plurality of slots to transmit. FW 6000734PCT04 23

[0127] FIG.15 shows an example where the first receive slot provides scheduling parameter to a device when to transmit. There can be a first switch time to switch from receive to transmit at a device. Likewise, the first switch time can allow the scheduling entity to switch from transmit to receive. Similarly, before the next receive occasion, there can be a second switch time to switch from receive to transmit at the scheduling entity. Likewise, the second switch time can allow the device to switch from transmit to receive.

[0128] The device may have high timing errors, possibly due to an SFO for the device’s clock. A device may be instructed to transmit message in slot 2. Due to the timing errors, the duration of each slot is larger than the duration of the transmitted message. The difference between the duration of the slot and the duration of the transmitted message can be considered guard time. Because the scheduling entity (e.g., reader, base station) is unaware whether the device has a fast clock or a slow clock resulting from the SFO, the duration of each slot is such that transmissions from a device in a first slot do not overlap with transmissions from a second device in the following slot at the scheduling entity. The implementations of this disclosure provide how to determine the duration of each slot and how to signal the starting time / duration of each slot. A device could know which slot to transmit from the scheduling.

[0129] After transmitting AIoT Msg-1, the device is expected to monitor the R2D link for the AIoT Msg-2. Instead of starting to monitor immediately after finishing transmitting AIoT Msg-1, if the device is informed when AIoT Msg-2 transmission is expected, the device can take measures to improve its availability, e.g., saving its energy by turning off its receiver or performing energy harvesting, while waiting. In addition, if the reader does not successfully receive any AIoT Msg-1, the reader could proceed to send the next trigger message instead of the AIoT Msg-2. Alternatively, a reader can still transmit AIoT Msg-2 regardless.

[0130] In one implementation, the time for AIoT Msg-2 or next trigger message transmission by the reader may be indicated by the trigger message as ^C^DE_^'(, which is defined as a time period after the ending of the trigger message, similar to the transmit times for the multiple transmission occasions indicated by the trigger message. Forexample, the trigger message may contain a list of times as the following: Tmin, ^7^2^,…,^7^^^, ^C^DE_^'(, as illustrated in FIG. 16A, Tmin≥TR2D_min. The actual transmission timeof AIoT Msg-2 or the next trigger message by the reader could include the processing time for receiving the last AIoT Msg-1 and the SFO of the devices. The latest time that thelast AIoT Msg-1 finishes transmission by the device with slow clock is ^7^^ + 1^^1 − ^^^.Assuming the reader uses ^^^F>^G_HGIJto process the last AIoT Msg-1 and prepare AIoT FW 6000734PCT04 24Msg-2, the earliest time that the reader can transmit AIoT Msg-2 is ^7^^ + 1^^1 − ^^^ +^^^F>^G_HGIJ. However, in order for a device with the slow clock not to miss the beginningof the AIoT Msg-2, the time indicated by the trigger message could be advanced, i.e.,^ ^K^13^^^^0,-^3^^-LM-N_ONPQC^DE_^'( = ^3,- .the parameters for calculating the timing of the AIoT Msg-2 or next trigger message timing may bemessage or a configuration message, and the actual timings are calculated by the device based on those parameters. In operation 1301 of FIG. 13, additional parameters ^^*+, ^^^1^, ^, and ^RGIJ are received. ^^*+ is the start time, and^^^1^ is the duration of the first transmission occasion, ^ is a multiplicative incrementalfactor related to the maximum SFO ^^of the device determined by the standards through the formula ^ = ',-^0,-, and ^RGIJ is the necessary processing time by the reader. Inoperations FIG.13, the following recursive formula can be used to calculate thestarting time of kthtransmission occasion ^7^4^. a. Let transmission occasion duration be ^^^4^, start time be ^7^4^, 4 = 1,2, … , ^b. ^7^1^ = ^^*+ and ^^^1^ are known.c. ^7^4^ = ^7^4 − 1^ + ^^^4 − 1^d. ^^^4^ = ^1 + ^^ × ^^^4 − 1^e. ^C^DE_^'( = ^7^^ + 1^^1 − ^^ + ^RGIJ

[0132] To simplify the calculation for a device with limited capability, the multiplicative factor ^ can be chosen such that the multiplication can be accomplished by simple shift+add. For example, ^ = ^ can accommodate S ^A FO up to 0.11, ^ = B canaccommodate SFO up to 0.059.

[0133] In another implementation, the parameter ^RGIJmay be omitted, and ^C^DE_^'( may be calculated as ^7^^ + 1^. This improves the efficiencies of the operationon the device, and the reader can ensure that the beginning of the AIoT Msg-2 will not be missed by the device with the slow clock. Therefore, the reader may transmit the AIoT Msg-2 or the next trigger message at ^7^^ + 1^^1 + ^^^ after the end of the triggermessage, which would guarantee that the device with the slow clock could catch the beginning of the AIoT Msg2.

[0134] For an implementation where the timing of the transmission occasions are pre- configured in the device (e.g., as a lookup table (LUT)), how the same table can be used FW 6000734PCT04 25for various D2R data rates that can be supported by the device could be considered. There are at least 3 options below for the contents of the LUT.1) A list of starting time of the transmission occasions: ^7^4^, where 4 = 1,2, … , S,and S is the size of the LUT. A device knowing index T of transmission occasion it has chosen and the number of transmission occasions ^ provisioned by the trigger message,can look up ^7^T^ as its transmission time after the ending of the trigger message, and^7^^^ as the time to start monitoring for the AIoT Msg-2 on the R2D link.2) A list of the starting time of the first transmission occasion and the durations ofthe transmission occasions: ^^'(_^*+, ^9^4^, where 4 = 1,2, … , S − 1, and S is the size ofthe LUT. A device knowing index T of transmission occasion it has chosen and the number of transmission occasions ^ provisioned by the trigger message, can accumulate the first T entries of the LUT as its transmission time after the ending of the trigger message, and accumulate the first ^ entries of the LUT as the time to start monitoring for Msg2 on the R2D link. 3) A list of the starting time of the first transmission occasion and the guard timebetween the transmission occasions: ^^'(_^*+, <^4^, where 4 = 1,2, … , S − 1, and S is thesize of the LUT. A device knowing index T of transmission occasion it has chosen and the number of transmission occasions ^ provisioned by the trigger message, can accumulatethe first T entries of the LUT plus the transmission time for T − 1 AIoT Msg-1’s as itstransmission time after the ending of the trigger message, and accumulate the first ^ entries of the LUT plus the transmission time for ^ AIoT Msg-1’s as the time to start monitoring for Msg2 on the R2D link.

[0135] To maintain the highest precision, the values in the LUT may be the number of ticks of the sampling clock rate of the device for the highest supported D2R data rate. The values are scaled for the actual D2R data rate by multiplying them with the ratio between the highest supported D2R data rate and the actual D2R data rate.

[0136] A device expects to receive an AIoT Msg-2 after the transmission of the AIoT Msg-1 within a maximum time TD2R_max. A device may implement a state machine based on events such as waiting for trigger, transmission of AIoT Msg-1, reception of AIoT Msg- 2, transmission of AIoT Msg-3. A failure to receive the AIoT Msg-2 can cause the state machine to revert to the waiting for trigger state. With TDMA of AIoT Msg-1, the maximum time TD2R_max used for M=1 (no TDMA) may be insufficient. In FIG.16A, M=3, if a device transmits AIoT Msg-1 in the first transmission occasion, when the device could expect AIoT Msg-2 and what the device could do in that time until the expected AIoT Msg-2 transmission are described in this disclosure. As described above, a device can estimate an offset for TD2R_maxbased on the transmission occasion selected. For the FW 6000734PCT04 26example in Table 4, an uniform 1.24 ms transmission occasion separation includes a 1 ms duration AIoT Msg-1. This means that a device can expect an AIoT Msg-2 approximately 3.6 ms (two 1.24 ms transmission occasions + 1 ms duration AIoT Msg-1+ 0.1 ms Tmin) after the end of the R2D transmission (e.g., R2D trigger). Based on this, an offset can be the difference between the estimated (or signaled) value of TNext_R2Dand the starting time of the Rth transmission occasion (or even the (R+1)th transmission occasion). While the device waits, the device may become unavailable for a duration of time. Table 4. Start of each transmission occasion at the device (“perceived time”) and reader (“actual time”) for M=3 with equal time slots. For the numeric values, it is assumed that Tm1=1 ms and fe=0.05, which results in Ts=1.24 ms. Event Device Actual time for Actual time for perceived device with fast device with slow

[0137] FIG.16B shows three possible message sequencing for M=3 when considering AIoT Msg-1, Msg-2, and Msg-3. In option a) of FIG.16B, a device can determine an expected time when to receive AIoT Msg-2. In this example, AIoT Msg-2 can contain up to three scheduling information for AIoT Msg-3 (A, B, C). For instance, if a reader receives an AIoT Msg-1 transmission from a device which used transmission occasion 0, the reader can schedule the corresponding AIoT Msg-3 in instance “A.” If a reader receives an AIoT Msg-1 transmission from a device which used transmission occasion 2, the reader can schedule corresponding AIoT Msg-3 in instance “A.” While there are FW 6000734PCT04 27scheduling benefits and possibly some device unavailability benefits, there are some possible limitations, such as the size of AIoT Msg-2 can become large as it contains scheduling information for up to M AIoT Msg-3. In addition, for a device scheduled to transmit in instance “C,” the effects of the SFO can be become large and affect the timing.

[0138] In option b) of FIG.16B, each AIoT Msg-2 contains scheduling information for one AIoT Msg-3. A device can determine an expected time when to receive the device’s corresponding AIoT Msg-2. There may be several times a device can check the AIoT Msg-2. In this example, if the reader receives an AIoT Msg-1 transmission from the device which used transmission occasion 2, the reader can schedule the corresponding AIoT Msg-3 in instance “A”, “B”, or “C,” depending on whether reception(s) of IoT Msg-1 transmission from other transmission occasions are successful. Some benefits include keeping the size of AIoT Msg-2 small, allowing the device to re-adjust the device’s timing after each R2D (i.e., AIoT Msg-2) transmission, and allowing devices to become unavailable for spans of time. One possible drawback is that the device may have to monitor AIoT Msg-2 to see whether the device’s AIoT Msg-1 transmission has been successfully received.

[0139] In option c) of FIG.16B, each AIoT Msg-2 contains scheduling information for one AIoT Msg-3. There may be an AIoT Msg-2 indicator that can provide a status of whether an AIoT Msg-1 transmission has been successfully received in transmission occasion. For example, an M-bit flag may be used. The first bit of the flag can correspond to transmission occasion 0 and can be “1” if an AIoT Msg-1 transmission has been successfully received in that transmission occasion; otherwise the first bit of the flag is “0.” Since a device is aware which transmission occasion it used, the indicator informs the device whether the device could monitor subsequent AIoT Msg-2. Further, the flag can indicate the number of AIoT Msg-2 and Msg-3 expected and the relative timing. For example, if the flag is “001,” the device that transmitted on transmission occasion 2 (zero-based) can expect AIoT Msg-2 and Msg-3 next. It may be possible to combine the scheduling information for AIoT Msg-3 with the flag when one device is scheduled. For example, if the flag is “101,” a device that transmits on transmission occasion 0 can expect AIoT Msg-2 and Msg-3 next, and a device that transmitted on transmission occasion 2 can expect AIoT Msg-2 and Msg-3 afterwards. One benefit is for device availability. A device whose AIoT Msg-1 was not successfully received can become unavailable. For M=1, the AIoT Msg-2 indicator may not be transmitted.

[0140] In another implementation, the AIoT Msg-2 indicator may contain anindication for the timing of the next R2D Trigger Message. This timing may be defined as^+^DE_^'(_^G*U_^*+, the minimum time from the ending of the AIoT Msg-2 indicator to theFW 6000734PCT04 28device starting to monitor for the next R2D Trigger Message. It can be calculated as:^+^DE_^'(_^G*U_^*+ = V^3,- W^^' + ^^'(_^*+ + ^^2 + ^('^_^*+X, where Y is the number ofthe contention, ^^'respectively, ^^'(_^*+is the minimum time between the ending of the R2D message and the beginning of the corresponding D2R message, and ^('^_^*+is the minimum time between the ending ofthe D2R message and the of the corresponding R2D message. The factor of^^3,- is applied to accommodatewith a slow clock, such that they would notmiss the beginning of the next R2D Trigger Message. Devices not expecting to receive an Msg-2 during this period may become unavailable for a period of ^+^DE_^'(_^G*U_^*+.

[0141] Alternatively, without an explicit indication of ^+^DE_^'(_^G*U_^*+in the AIoT Msg-2 Indicator, the device may carry out the calculation on its own based on the information in the AIoT Msg-2 indicator and other system parameters. However, this may only be practical for devices more capable than Device 1.

[0142] Referring to FIG.15B, to reduce the number of R2D Trigger messages a device has to monitor before arriving at the access round in which the device is expected to be inventoried, in one implementation, each R2D Round Trigger message may contain anexplicit indication of the minimum duration for the current access round,^^JJ^^^_^IZ+>_^*+. A device not expected to be inventoried during the current access roundmay become unavailable for a period of ^^JJ^^^_^IZ+>_^*+. Due to the statistical nature of the random access procedure, the reader does not know ahead of time the actual duration of the current access round. However, this parameter can be chosen by the reader as a trade-off between time resource efficiency and device energy efficiency. If the actual duration of the access round is shorter than ^^JJ^^^_^IZ+>_^*+, the reader could wait till at least ^^JJ^^^_^IZ+>_^*+before starting the next access round, therefore, wastingsome time resource. If the actual duration of the access round is longer than^^JJ^^^_^IZ+>_^*+, devices not expected to be inventoried during the current access roundmay waste some energy monitoring some of the R2D Trigger Messages in the current access round transmitted beyond ^^JJ^^^_^IZ+>_^*+.

[0143] All devices can support TDMA with one transmission occasion (X=1). This disclosure provides a deployment where one group of devices can support TDMA with more than one transmission occasion and another group of devices that only support TDMA with one transmission occasion. In some implementations, it may be assumed that all devices support TDMA with more than one transmission occasion (X>1). It may FW 6000734PCT04 29be possible that some devices can only support one transmission occasion (X=1). Since a reader is unaware of the device characteristics (supporting only X=1 or supporting X>1) during contention based access, some implementations to enable both types of devices (X=1 only and X>1) to perform contention based access are provided.

[0144] In one implementation, both devices can transmit within the same X=1 resource, as shown using three transmission occasions as an example in option a) of FIG. 16C. In another implementation, an X>1 device can transmit on transmission occasions other than immediately after the R2D transmission, as shown in option b) of FIG.16C. In this case, there are two transmission occasions. In this example, the time between the end of the R2D transmission and the beginning of the multiple transmission occasions is used for AIoT Msg1 transmission for the X=1 only device. In FIG.16C, the durations of transmission occasions c12, c14, c16 can be equal or vary, such as increasing (or non- decreasing) with the duration of c12 ≤ the duration of c14 ≤ the duration of c16; the duration of c12 > the duration of c14 and the duration of c14 ≤ the duration of c16.

[0145] From an X=1 only device perspective, the device is able to start transmitting AIoT Msg1 in a window bounded by the minimum time (e.g., TD2R_min) and maximum time (e.g., TD2R_max). One of the design constraints may be that the ending time for the X=1 only device, (Tm1+TD2R_max) occurs before the transmission occasion c22 (X=2 in option a) of FIG.16C and X=1 in option b) of FIG.16C). The following relation can be used to determine the offset ∆, where fe is related to the SFO. W^^^ + ^('^_^FDX × ^1 + ^^^ ≤ ^1 − ^^^∆Simplifying to1+ ^∆≥ W^ ^^^ + ^('^_^FDX ×− ^^

[0146] The end ofthe device with the slowest clock. In this example, ^',^ = ∆ × ^1 + ^^^ + ^^^ × ^1 + ^^^

[0147] There may be several approaches for a reader to signal the timing. For example, in option a) of FIG.16C, a list of time domain resource allocations (TDRAs) can be provided, {TD2R_max, ∆, …}. A device supporting X>1 transmission occasions can begin transmitting at TD2R_max if it selects the first transmission occasion, ∆ if the device selects the second transmission occasion, etc. A device only supporting X=1 transmission occasions can interpret TD2R_maxas the maximum time. Alternatively, the value TD2R_maxcan be provided separately or specified in the standards. An X=1 only device can FW 6000734PCT04 30disregard the list. The selection of the transmission occasion can be random among the set of transmission occasions. Considering option a) of FIG.16C, it may be possible that the X>1 devices could select the first transmission occasion with lower probability and the remaining transmission occasions with equal probability. For example, if X=3. then the probabilities can be {1 / 3, 1 / 3, 1 / 3}, or {1 / 5, 2 / 5, 2 / 5} or {0, 1 / 2, 1 / 2} (which is option b) of FIG.16C).

[0148] For example, in option b) of FIG.16C, if the value TD2R_maxcan be provided separately or specified in the standards, an X=1 only device can disregard a TDRA list of {∆, …}. A device supporting X>1 transmission occasions can transmit on the first transmission occasion starting at ∆.

[0149] Alternatively, a flag indicating that an X>1 device can use the first entry in the list {TD2R_max, ∆, …} can be provided.

[0150] In yet another implementation, option c) of FIG.16C shows an example of a deployment with X=1 only and X>1 devices. In the example, a reader indicates the starting time of the first transmission occasion c32. A possible benefit is that the X=1 only device uses the time resources c34 while the X>1 devices use the first transmission occasion c32.

[0151] The FIG.16D captures timing at the reader, a device with a slow clock, and a device with a fast clock. In this example, fe=0.1, Tm1=1 ms, TD2R_max=0.25 ms, and TD2R_min=0.1 ms. In this example, ∆=1.52 ms. A X=1 only device transmits with 1.52 ms of the R2D transmission. FIG.16D shows the earliest and latest times forby the X=1 only device. There are advantages of TDMA: 1.5 ms extra guard time for each trigger with 3 transmission occasions.

[0152] In FIG.16D, for the X=1 only device, the reader may assume that the device may not be able to count time. A reader may schedule X>1 devices after one trigger message, and then X=1 only devices after a different trigger message.

[0153] FIG.17 shows an example timing diagram for multiple transmission occasions for Message 1 (Msg1) following an R2D message. There is a first timing offset (Toffset1), and a first transmission occasion (Toffset2) with a duration that is the sum ofof Msg1 (Tmsg1) and additional guard time (no expected transmission from a device) from the end of Msg1 transmission to the start of the second transmission occasion. The start of the second transmission occasion from the end of the R2D msg is given by Toffset3, which is the sum of Toffset1and Toffset2. The start of the third transmissionfrom the end of the R2D msg is given by Toffset5, which is the sum of Toffset3 and Toffset4. The duration of the second transmission occasion (Toffset4) is the sum of Tmsg1and additional FW 6000734PCT04 31guard time (no expected transmission from a device) from the end of Msg1 transmission in the second transmission occasion to the start of the third transmission occasion.

[0154] For Rel-20 Ambient IoT devices, there may be a possibility of supporting X=3 (or higher number of) transmission occasions. From the Rel-19 standards, an ambient IoT device (Device 1) can only support X=2 transmission occasions. A Rel-20 device (Device 2) may be able to support X>2 transmission occasions. Another capability for a device supporting more than two transmission occasions is that this device may have a smaller value for the SFO ~104.

[0155] There may be two cases of deployments with devices supporting two transmission occasions and more than two transmission occasions. This disclosure describes how contention based random access is configured when devices with differing number of supported transmission occasions. In Case 1, where contention based random access when both X=2 supporting and X>2 supporting devices are present, both devices can use the first two transmission occasions. • One implication is that the X>2 device uses the same timing for the first two transmission occasions as the X=2 device. For the third and number of greater transmission occasions, the timing can be based on the SFO requirements for the X>2 device. • An X>2 device can access all 3 occasions. The timing constraint for the third occasion may be different than the second occasion. • This disclosure describes how the smaller value of the SFO affects the start time for the third transmission occasion.

[0156] The second case of deployment is where the transmission occasions for Device 1 and the transmission occasions of Device 2 are separate. Given the development of the Rel-19 standards timing, the timing values for Device 2 are described.

[0157] In Table 5, a general timing expression is provided for the same value of the SFO, expressed as a timing error te, for three transmission occasions. Table 5. Timing for Toffset1 and Toffset2 FW 6000734PCT04 32wn in Equation (1). 2^offset1\^ + ^m ^1 + \ ^ 2\ 1 + \ (1)^ sg1 ^ ^ ^offset2 ≥1 − \ = ^offset1 + ^msg1^ 1 − \^ 1 − \^

[0159] 2\ 2\^ ≥ ^ ^ (2)offset2 1 − ^offset1 + ^1 +1 − ^ ^msg1^ ^

[0160] For the onthe following relationship. W^offset1 + ^offset2 + ^offset4X^1 − \^^ ≥ W^offset1 + ^offset2 + ^msg1X^1 + \^^ (3)

[0161] Simplifying Equation (3) produces Equation (4) below. 2\ 2\ 2\^ 4 ≥ ^ ^ ^ (4)offset − ^offset1 +− ^offset2 + ^1 +− ^ ^msg1

[0162] Equation (5). 2\ 2\ 2\ ' (5)≥ ^ ^1 + ^ ^ + ^1 + ^ ^

[0163] Alternatively, the smallest value for Toffset5is shown in Equation (6). FW 6000734PCT04 332\ '^ 2\^ 2\ (6)^offset5 ≥ ^1 +1 − \ ^ ^offset1 + ^2 + ^ ^1 + ^ ^ ^msg1^ 1 − \^ 1 − \^

[0164] ^2\^⁄ 1 − \^ ^, specifically shown in Equations (7) and (8).^^offset2 = _'^offset1 + ^1 + _'^^msg1 (7)(8)

[0165] The use of

[0166] For \^ = 0.1, ^2\^⁄ 1 − \^ ^ = 0.22, _' = 0.25. _' to an power oftwo may facilitate implementation of clock dividers.

[0167] Equations (9)-(11) below show the specified value of ^o^ffset3. ^^offset3 = ^ ^offset1 + ^offset2 (9)

[0168] error can be smaller than the timing error for Device 1 (e.g., \^A^^ ≤. The expression todetermine the start of the third transmission occasion may have include both timing errors. Since a Device 1 can use transmit in the second transmission occasion, the third transmission occasion could account for the timing of AIoT Msg-1 with the timing error of Device 1. FIG.18 shows the timing at the reader when both Device 1 and Device 2 are present. Table 6. Timing for X=3, different SFO FW 6000734PCT04 34[01ng error \^^A^when the timing of the first two transmission occasions are determined by a first SFO. The expressions for ^o^ffset4and ^o^ffset5are shown in Equations (12) and (13) below. The reason for the max function is that the reader expects the third transmission occasion to start after the device with the slow clock finishes transmission in the second transmission occasion. W^^offset3 + ^^offset4 X :1 − \^A^^ ; ≥ W^^offset3 + ^msg1X :1 + max :\ ^A^^, \^ ;; (12)

[0170] Assuming \^A^^ ≤ \^, Equation (13) shows the following.W^^+ ^^ ^A^offset4 X :1 − \^ ; ≥ W^^offset3 + ^msg1X^1 + \^^ (13)

[0171] The expression in Equation (13) has both timing errors. Since a Device 1 can transmit in the second transmission occasion, the third transmission occasion could account for the timing of Msg1 with the timing error of Device 1. ^^ 1 + \^(14) ^≥ W^ + ^ h i − ^^

[0172] With simplifying, Equation (15) shows the following. 1+ \ \ ^A^ +(15) ^^ ^ ^ ^^ ^ \^FW 6000734PCT04 35

[0173] For notation purposes, let j^A^ = E^k^- 3E-^0E^k^-

[0174] Since ^^ ^ ^ ^ ^offset5 ≥ ^offset1 + ^offset2 + ^offset4 = ^offset3 + ^offset4 , Equation (16)shows the following. ^^offset5 ≥ ^^offset3 + ^lmmmmmmmm^msg1W1 + j An^Xm +mm ^^omffmsemt3m jm^oA^ (16)^^offset5 ≥ ^^offset3 W1 + j^A^X + ^ ^msg1W1 + j A^X = W1 + j^A^XW^^offset3 + ^msg1X (17)

[0176] Expanding the above, Equation (18) shows the following. ^^offset5 ≥ ^1 + _'^W^ ^offset1 + ^msg1XW1 + j A^X + ^ ^msg1W1 + j A^X (18)

[0177] Grouping terms, Equation (19) shows the following. ^^offset5 ≥ W1 + j^A^X^1 + _'^^offset1 + W1 + j^A^X^2 + _'^^msg1 (19)

[0178] There is similarity between Equation (19) and Equation (6). The termW1 + j^A^X can be quantized, or the terms W1 + j^A^X^1 + _'^ and W1 + j^A^X^2 + _'^ couldbe quantized to simple numbers.

[0179] In this case, a device supporting X>2 uses separate occasions than a device supporting X=2. The network can signal that. Since all the devices have the same smaller SFO of \^^A^, then following the derivation in Equations (1)-(6), the minimum timing for the 2nd and 3rd transmission occasions is: 2\^A^^A^(20) ≥^ 2\^ ^ + h1 + ^ iFW 6000734PCT04 362\^A^^A^ ^A^ ' (22)^≥ ^ h1 + 2\^ i ^ + h 2\^offset4\ offse 1 + i ^1 − ^A^ ^A^ t1 ^A^ msg1^ 1 − \^ 1 − \^

[0180] Following the definition in standards, Equation (24) defines the following. ^k^_ = 0Hk ^0E- (24)A 2 with TA = plog' ^'E^k^ ^q-

[0181] The timing for the 2nd and 3rd transmission occasions can be defined as follows. ^^offset2 = _A^offset1 + ^1 + _A^^msg1 (25)

[0182] Equations (27) and (28) show the iterative relationship. This relationship applies to the general case of kthtransmission occasion, with its start time as ^offset^'r0^^and its duration as ^offset^'r^: ^^fset 'r = ^1 + ^ ^of ^ ^ _A ^offset^'r0'^FW 6000734PCT04 37^^offset^'r0^^ = ^1 + _A^^^offset^'r02^ + ^1 + _A^^msg1 (30)

[0183] Or,msg1equations. r0^^^offset^'r0^^ = ^1 + _A^r0^^offset^ + s^1 + _A^t ^msg1Equations (31) and (32) can be derived from above. ^^offset^'r^ = _A^1 + _A^r0^^offset^ + ^1 + _A^r^msg1 (31)

[0184] Alternatively, if \^^A^is sufficiently small (such as 104), it may be simpler to use an equal duration foroccasion. This transmission duration could include a guard time that guarantees that the transmission of the last occasion by a device with fast clock do not overlap with the transmission of the second last occasion by a device with slow clock.

[0185] Suppose the total number of transmission occasions is S, and the first occasion starts at time ^offset^, and the duration of all transmission occasions is ^offset',the start time of occasion 4 ≤ S is shown in Equation (33) below.^offset^'r0^^ = ^offset^ + ^4 − 1^^offset2 (33)

[0186] To avoid collision, the following equation could be satisfied. ^offset^'C0^^ :1 − \^A^^ ; ≥ :1 + \^A^^ ; W^offset^'C02^ + ^msg1X (34)FW 6000734PCT04 38

[0187] Inserting (33) into (34), Equation (35) can be derived. ^^offset^ + ^S − 1^^offset2^ :1 − \^A^^ ;(35) ^A^ ^ ^ ^ ^

[0188] canoffset2. 2\^A^^A^ (36) ^^ 1 + \^offset2 ≥ ^offset^ + ^1 − ^A^^ ^ + 1^ 1 − ^A^ msg1^ ^ + 1^

[0189] Equation (37) defines the following. ^offset2 = v^offset^ + w^msg1 (37)

[0190] The minimum value for v and w for various value of N is shown in the tablebelow assuming \^A^^ = 0.01.N α β

[0191] For ease of c ers can be quantized as thefollowing. N α βFW 6000734PCT04 391 1 / 32 11 / 8 2 1 / 32 11 / 8

[0192] FIG.19A shows a flow chart of a method 1900 performed by a wireless device (e.g., an AIoT device), in accordance with some implementations. The wireless device may include computer-readable code or instructions executing on one or more processors of the wireless device. Coding of the software for carrying out or performing the method 1900 is well within the scope of a person of ordinary skill in the art having regard to the present disclosure. The method 1900 may include additional or fewer operations than those shown and described and may be carried out or performed in a different order. Computer-readable code or instructions of the software executable by the one or more processors may be stored on at least one non-transitory computer-readable medium, such as for example, at least one memory of the wireless device. In some embodiments, the method 1900 may be performed by one or more of units or modules (e.g., an integrated circuit) of the wireless device, such as field programmable gate arrays (FPGAs) or application-specific integrated circuits (ASICs).

[0193] The method 1900 starts at the operation 1902, where the wireless device selects a transmission occasion from a first transmission occasion and a second transmission occasion for transmission of a first message. A first transmission offset for the first transmission occasion equals a time offset. A second transmission offset for the second transmission occasion equals a sum of the time offset scaled by a first factor and a duration of the first message scaled by a second factor. At the operation 1904, the wireless device transmits the first message at a transmission offset after an end of a received message. The transmission offset is the second transmission offset in accordance to the transmission occasion being the second transmission occasion. FW 6000734PCT04 40

[0194] In some implementations, a first sum of the time offset and the duration of the second transmission offset may equal a second sum scaled by the second factor. The second sum may be of the time offset and the duration of the first message.

[0195] In some implementations, the received message may be a reader to device (R2D) trigger message.

[0196] In some implementations, the wireless device may receive an indication of a number of transmission occasions available for transmission of the first message following the end of the received message. The wireless device selecting the transmission occasion may be in response to the number of transmission occasions being greater than one.

[0197] In some implementations, the wireless device may select the transmission occasion randomly based on the number of transmission occasions.

[0198] In some implementations, the received message may be an R2D trigger message. The R2D trigger message may include the indication of the number of transmission occasions.

[0199] In some implementations, the first factor may be greater than 1, and the second factor may be greater than 1.

[0200] In some implementations, the first factor and the second factor may be the same.

[0201] In some implementations, the second factor may be a first sum of 1 and a term related to a device type. The term may be 0.25 for a first device type when a number of transmission occasions is 2.

[0202] In some implementations, the first factor may be different from the second factor.

[0203] In some implementations, the transmission offset may be the first transmission offset in accordance to the transmission occasion being the first transmission occasion.

[0204] In some implementations, a first duration of the first transmission occasion may be the duration of the first message scaled by the second factor.

[0205] In some implementations, the wireless device may select the transmission occasion from the first transmission occasion, the second transmission occasion, and a third transmission occasion. A third duration of the third transmission occasion may be greater than a second duration of the second transmission occasion. The second duration may be greater than a first duration of the first transmission occasion. FW 6000734PCT04 41

[0206] FIG.19B shows a flow chart of a method 1950 performed by a reader device, in accordance with some implementations. The reader device may include computer- readable code or instructions executing on one or more processors of the reader device. Coding of the software for carrying out or performing the method 1950 is well within the scope of a person of ordinary skill in the art having regard to the present disclosure. The method 1950 may include additional or fewer operations than those shown and described and may be carried out or performed in a different order. Computer-readable code or instructions of the software executable by the one or more processors may be stored on at least one non-transitory computer-readable medium, such as for example, at least one memory of the reader device. In some embodiments, the method 1950 may be performed by one or more of units or modules (e.g., an integrated circuit) of the reader device, such as field programmable gate arrays (FPGAs) or application-specific integrated circuits (ASICs).

[0207] The method 1950 starts at the operation 1952, where the reader device transmits a message to an AIoT device. At the operation 1954, the reader device monitors a first transmission occasion for a transmission of a first message from the AIoT device based on a time offset after an end of the message. At the operation 1956, the reader device monitors a second transmission occasion for the transmission of the first message from the AIoT device based on a sum of the time offset scaled by a first factor and a duration of the first message scaled by a second factor after the end of the message. At the operation 1958, in response to receiving the first message from the AIoT device, the reader device transmits to the AIoT device a second message after the second transmission occasion.

[0208] In some implementations, a first sum of the time offset and the duration of a second transmission offset may equal a second sum scaled by the second factor, the second sum being of the time offset and the duration of the first message.

[0209] In some implementations, the message may be a reader to device (R2D) trigger message.

[0210] In some implementations, the reader device may transmit to the AIoT device an indication of a number of transmission occasions available for transmission of the first message following the end of the message.

[0211] In some implementations, the message may be an R2D trigger message, and the R2D trigger message may include the indication of the number of transmission occasions. FW 6000734PCT04 42

[0212] In some implementations, the first factor may be greater than 1, and the second factor may be greater than 1.

[0213] In some implementations, the first factor and the second factor may be the same.

[0214] In some implementations, the second factor may be a first sum of 1 and a term related to a device type. The term may be 0.25 for a first device type when a number of transmission occasions is 2.

[0215] In some implementations, the first factor may be different from the second factor.

[0216] In some implementations, a first duration of the first transmission occasion may be the duration of the first message scaled by the second factor.

[0217] In some implementations, the reader device may monitor a third transmission occasion. A third duration of the third transmission occasion may be greater than a second duration of the second transmission occasion. The second duration may be greater than a first duration of the first transmission occasion.

[0218] FIG.20 illustrates an example communications system 2000. Communications system 2000 includes an access node 2010 serving user equipments (UEs) with coverage 2001, such as UEs 2020. In a first operating mode, communications to and from a UE passes through access node 2010 with a coverage area 2001. The access node 2010 is connected to a backhaul network 2015 for connecting to the Internet, operations and management, and so forth. In a second operating mode, communications to and from a UE do not pass through access node 2010, however, access node 2010 typically allocates resources used by the UE to communicate when specific conditions are met. Communications between a pair of UEs 2020 can use a sidelink connection (shown as two separate one-way connections 2025). In FIG.20, the sidelink communication is occurring between two UEs operating inside of coverage area 2001. However, sidelink communications, in general, can occur when UEs 2020 are both outside coverage area 2001, both inside coverage area 2001, or one inside and the other outside coverage area 2001. Communication between a UE and access node pair occur over uni-directional communication links, where the communication links between the UE and the access node are referred to as uplinks 2030, and the communication links between the access node and UE is referred to as downlinks 2035.

[0219] Access nodes may also be commonly referred to as Node Bs, evolved Node Bs (eNBs), next generation (NG) Node Bs (gNBs), master eNBs (MeNBs), secondary eNBs (SeNBs), master gNBs (MgNBs), secondary gNBs (SgNBs), network controllers, control FW 6000734PCT04 43nodes, base stations, access points, transmission points (TPs), transmission-reception points (TRPs), cells, carriers, macro cells, femtocells, pico cells, and so on, while UEs may also be commonly referred to as mobile stations, mobiles, terminals, users, subscribers, stations, and the like. Access nodes may provide wireless access in accordance with one or more wireless communication protocols, e.g., the Third Generation Partnership Project (3GPP) long term evolution (LTE), LTE advanced (LTE- A), 5G, 5G LTE, 5G NR, sixth generation (6G), High Speed Packet Access (HSPA), the IEEE 802.11 family of standards, such as 802.11a / b / g / n / ac / ad / ax / ay / be, etc. While it is understood that communications systems may employ multiple access nodes capable of communicating with a number of UEs, only one access node and two UEs are illustrated for simplicity.

[0220] FIG.21 illustrates an example communication system 2100. In general, the system 2100 enables multiple wireless or wired users to transmit and receive data and other content. The system 2100 may implement one or more channel access methods, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), or non-orthogonal multiple access (NOMA).

[0221] In this example, the communication system 2100 includes electronic devices (ED) 2110a-2110c, radio access networks (RANs) 2120a-2120b, a core network 2130, a public switched telephone network (PSTN) 2140, the Internet 2150, and other networks 2160. While certain numbers of these components or elements are shown in FIG.21, any number of these components or elements may be included in the system 2100.

[0222] The EDs 2110a-2110c are configured to operate or communicate in the system 2100. For example, the EDs 2110a-2110c are configured to transmit or receive via wireless or wired communication channels. Each ED 2110a-2110c represents any suitable end user device and may include such devices (or may be referred to) as a user equipment or device (UE), wireless transmit or receive unit (WTRU), mobile station, fixed or mobile subscriber unit, cellular telephone, personal digital assistant (PDA), smartphone, laptop, computer, touchpad, wireless sensor, AIoT device (e.g., for asset management), or consumer electronics device.

[0223] The RANs 2120a-2120b here include base stations 2170a-2170b, respectively. Each base station 2170a-2170b is configured to wirelessly interface with one or more of the EDs 2110a-2110c to enable access to the core network 2130, the PSTN 2140, the Internet 2150, or the other networks 2160. For example, the base stations 2170a-2170b may include (or be) one or more of several well-known devices, such as a base transceiver station (BTS), a Node-B (NodeB), an evolved NodeB (eNB), a Next Generation (NG) FW 6000734PCT04 44NodeB (gNB), a gNB centralized unit (gNB-CU), a gNB distributed unit (gNB-DU), a Home NodeB, a Home eNodeB, a site controller, an access point (AP), or a wireless router. The EDs 2110a-2110c are configured to interface and communicate with the Internet 2150 and may access the core network 2130, the PSTN 2140, or the other networks 2160.

[0224] In the embodiment shown in FIG.21, the base station 2170a forms part of the RAN 2120a, which may include other base stations, elements, or devices. Also, the base station 2170b forms part of the RAN 2120b, which may include other base stations, elements, or devices. Each base station 2170a-2170b operates to transmit or receive wireless signals within a particular geographic region or area, sometimes referred to as a “cell.” In some embodiments, multiple-input multiple-output (MIMO) technology may be employed having multiple transceivers for each cell.

[0225] The base stations 2170a-2170b communicate with one or more of the EDs 2110a-2110c over one or more air interfaces 2190 using wireless communication links. The air interfaces 2190 may utilize any suitable radio access technology.

[0226] It is contemplated that the system 2100 may use multiple channel access functionality, including such schemes as described above. In particular embodiments, the base stations and EDs implement 5G New Radio (NR), LTE, LTE-A, or LTE-B. Of course, other multiple access schemes and wireless protocols may be utilized.

[0227] The RANs 2120a-2120b are in communication with the core network 2130 to provide the EDs 2110a-2110c with voice, data, application, Voice over Internet Protocol (VoIP), or other services. Understandably, the RANs 2120a-2120b or the core network 2130 may be in direct or indirect communication with one or more other RANs (not shown). The core network 2130 may also serve as a gateway access for other networks (such as the PSTN 2140, the Internet 2150, and the other networks 2160). In addition, some or all of the EDs 2110a-2110c may include functionality for communicating with different wireless networks over different wireless links using different wireless technologies or protocols. Instead of wireless communication (or in addition thereto), the EDs may communicate via wired communication channels to a service provider or switch (not shown), and to the Internet 2150.

[0228] Although FIG.21 illustrates one example of a communication system, various changes may be made to FIG.21. For example, the communication system 2100 could include any number of EDs, base stations, networks, or other components in any suitable configuration. FW 6000734PCT04 45

[0229] FIGs.22A and 22B illustrate example devices that may implement the methods and teachings according to this disclosure. In particular, FIG.22A illustrates an example ED 2210, and FIG.22B illustrates an example base station 2270. The ED 2210 and the base station 2270 may communicate over the air interface 2290. These components could be used in the system 2100 or in any other suitable system.

[0230] As shown in FIG.22A, the ED 2210 includes at least one processing unit 2200. The processing unit 2200 implements various processing operations of the ED 2210. For example, the processing unit 2200 could perform signal coding, data processing, power control, input / output processing, or any other functionality enabling the ED 2210 to operate in the system 2100. The processing unit 2200 also supports the methods and teachings described in more detail above. Each processing unit 2200 includes any suitable processing or computing device configured to perform one or more operations. Each processing unit 2200 could, for example, include a microprocessor, microcontroller, digital signal processor, field programmable gate array, or application specific integrated circuit.

[0231] The ED 2210 also includes at least one transceiver 2202. The transceiver 2202 is configured to modulate data or other content for transmission by at least one antenna or NIC (Network Interface Controller) 22229004. The transceiver 2202 is also configured to demodulate data or other content received by the at least one antenna 2204. Each transceiver 2202 includes any suitable structure for generating signals for wireless or wired transmission or processing signals received wirelessly or by wire. Each antenna 2204 includes any suitable structure for transmitting or receiving wireless or wired signals. One or multiple transceivers 2202 could be used in the ED 2210, and one or multiple antennas 2204 could be used in the ED 2210. Although shown as a single functional unit, a transceiver 2202 could also be implemented using at least one transmitter and at least one separate receiver.

[0232] The ED 2210 further includes one or more input / output devices 2206 or interfaces (such as a wired interface to the Internet 2150). The input / output devices 2206 facilitate interaction with a user or other devices (network communications) in the network. Each input / output device 2206 includes any suitable structure for providing information to or receiving information from a user, such as a speaker, microphone, keypad, keyboard, display, or touch screen, including network interface communications.

[0233] In addition, the ED 2210 includes at least one memory 2208. The memory 2208 stores instructions and data used, generated, or collected by the ED 2210. For example, the memory 2208 could store software or firmware instructions executed by the processing unit(s) 2200 and data used to reduce or eliminate interference in incoming FW 6000734PCT04 46signals. Each memory 2208 includes any suitable volatile or non-volatile storage and retrieval device(s). Any suitable type of memory may be used, such as random access memory (RAM), read only memory (ROM), hard disk, optical disc, subscriber identity module (SIM) card, memory stick, secure digital (SD) memory card, and the like.

[0234] As shown in FIG.22B, the base station 2270 includes at least one processing unit 2250, at least one transceiver 2252, which includes functionality for a transmitter and a receiver, one or more antennas 2256, at least one memory 2258, and one or more input / output devices or interfaces 2266. A scheduler, which would be understood by one skilled in the art, is coupled to the processing unit 2250. The scheduler could be included within or operated separately from the base station 2270. The processing unit 2250 implements various processing operations of the base station 2270, such as signal coding, data processing, power control, input / output processing, or any other functionality. The processing unit 2250 can also support the methods and teachings described in more detail above. Each processing unit 2250 includes any suitable processing or computing device configured to perform one or more operations. Each processing unit 2250 could, for example, include a microprocessor, microcontroller, digital signal processor, field programmable gate array, or application specific integrated circuit.

[0235] Each transceiver 2252 includes any suitable structure for generating signals for wireless or wired transmission to one or more EDs or other devices. Each transceiver 2252 further includes any suitable structure for processing signals received wirelessly or by wire from one or more EDs or other devices. Although shown combined as a transceiver 2252, a transmitter and a receiver could be separate components. Each antenna 2256 includes any suitable structure for transmitting or receiving wireless or wired signals. While a common antenna 2256 is shown here as being coupled to the transceiver 2252, one or more antennas 2256 could be coupled to the transceiver(s) 2252, allowing separate antennas 2256 to be coupled to the transmitter and the receiver if equipped as separate components. Each memory 2258 includes any suitable volatile or non-volatile storage and retrieval device(s). Each input / output device 2266 facilitates interaction with a user or other devices (network communications) in the network. Each input / output device 2266 includes any suitable structure for providing information to or receiving / providing information from a user, including network interface communications.

[0236] FIG.23 is a block diagram of a computing system 2300 that may be used for implementing the devices and methods disclosed herein. For example, the computing system can be any entity of UE, access network (AN), mobility management (MM), FW 6000734PCT04 47session management (SM), user plane gateway (UPGW), or access stratum (AS). Specific devices may utilize all of the components shown or only a subset of the components, and levels of integration may vary from device to device. Furthermore, a device may contain multiple instances of a component, such as multiple processing units, processors, memories, transmitters, receivers, etc. The computing system 2300 includes a processing unit 2302. The processing unit includes a central processing unit (CPU) 2314, memory 2308, and may further include a mass storage device 2304, a video adapter 2310, and an I / O interface 2312 connected to a bus 2320.

[0237] The bus 2320 may be one or more of any type of several bus architectures including a memory bus or memory controller, a peripheral bus, or a video bus. The CPU 2314 may comprise any type of electronic data processor. The memory 2308 may comprise any type of non-transitory system memory such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous DRAM (SDRAM), read-only memory (ROM), or a combination thereof. In an embodiment, the memory 2308 may include ROM for use at boot-up, and DRAM for program and data storage for use while executing programs.

[0238] The mass storage 2304 may comprise any type of non-transitory storage device configured to store data, programs, and other information and to make the data, programs, and other information accessible via the bus 2320. The mass storage 2304 may comprise, for example, one or more of a solid state drive, hard disk drive, a magnetic disk drive, or an optical disk drive.

[0239] The video adapter 2310 and the I / O interface 2312 provide interfaces to couple external input and output devices to the processing unit 2302. As illustrated, examples of input and output devices include a display 2318 coupled to the video adapter 2310 and a mouse, keyboard, or printer 2316 coupled to the I / O interface 2312. Other devices may be coupled to the processing unit 2302, and additional or fewer interface cards may be utilized. For example, a serial interface such as Universal Serial Bus (USB) (not shown) may be used to provide an interface for an external device.

[0240] The processing unit 2302 also includes one or more network interfaces 2306, which may comprise wired links, such as an Ethernet cable, or wireless links to access nodes or different networks. The network interfaces 2306 allow the processing unit 2302 to communicate with remote units via the networks. For example, the network interfaces 2306 may provide wireless communication via one or more transmitters / transmit antennas and one or more receivers / receive antennas. In an embodiment, the processing unit 2302 is coupled to a local-area network 2322 or a wide-area network for data FW 6000734PCT04 48processing and communications with remote devices, such as other processing units, the Internet, or remote storage facilities.

[0241] It should be appreciated that not all components in the devices described in FIGs.20-23 are required. In a non-limiting example, the ED 2210 may be implemented as an AIoT device 2210. But, the AIoT device 2210 may not include an input / output devices 2206 for providing information to or receiving information from a user, such as a speaker, microphone, keypad, keyboard, display, or touch screen. The transceiver 2202 of the AIoT device 2210 may be capable of transmitting by backscattering a radio wave received, instead of by generating the radio wave, for wireless communication purpose. In another non-limiting example, the system 2300 may be implemented as an AIoT device 2300 that does not include or use the mass storage device 2304, the video adapter 2310, the mouse, keyboard, or printer 2316, or the display 2318.

[0242] It should be appreciated that one or more steps of the embodiment methods provided herein may be performed by corresponding units or modules. For example, a signal may be transmitted by a transmitting unit or a transmitting module. A signal may be received by a receiving unit or a receiving module. A signal may be processed by a processing unit or a processing module. Other steps may be performed by a performing unit or module, a generating unit or module, an obtaining unit or module, a setting unit or module, an adjusting unit or module, an increasing unit or module, a decreasing unit or module, a determining unit or module, a modifying unit or module, a reducing unit or module, a removing unit or module, or a selecting unit or module. The respective units or modules may be hardware, software, or a combination thereof. For instance, one or more of the units or modules may be an integrated circuit, such as field programmable gate arrays (FPGAs) or application-specific integrated circuits (ASICs).

[0243] Although the description has been described in detail, it should be understood that various changes, substitutions and alterations can be made without departing from the spirit and scope of this 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, as one of ordinary skill in the art will readily appreciate from this disclosure that processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, may perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps. FW 6000734PCT04 49

Claims

What Is Claimed Is:

1. A method, comprising: selecting, by an ambient Internet of Things (AIoT) device, a transmission occasion from a first transmission occasion and a second transmission occasion for transmission of a first message, wherein a first transmission offset for the first transmission occasion equals a time offset, and wherein a second transmission offset for the second transmission occasion equals a sum of the time offset scaled by a first factor and a duration of the first message scaled by a second factor; and transmitting, by the AIoT device, the first message at a transmission offset after an end of a received message, wherein the transmission offset is the second transmission offset in accordance to the transmission occasion being the second transmission occasion.

2. The method of claim 1, wherein a first sum of the time offset and the duration of the second transmission offset equals a second sum scaled by the second factor, the second sum being of the time offset and the duration of the first message.

3. The method of any of claims 1-2, wherein the received message is a reader to device (R2D) trigger message.

4. The method of any of claims 1-3, further comprising: receiving, by the AIoT device from a reader device, an indication of a number of transmission occasions available for transmission of the first message following the end of the received message, wherein the selecting the transmission occasion is in response to the number of transmission occasions being greater than one.

5. The method of claim 4, the selecting comprising: selecting, by the AIoT device, the transmission occasion randomly based on the number of transmission occasions.

6. The method of claim 4, wherein the received message is an R2D trigger message, and wherein the R2D trigger message includes the indication of the number of transmission occasions.

7. The method of any of claims 1-6, wherein the first factor is greater than 1, and the second factor is greater than 1. FW 6000734PCT04 508. The method of any of claims 1-7, wherein the first factor and the second factor are the same.

9. The method of claim 8, wherein the second factor is a first sum of 1 and a term related to a device type, and wherein the term is 0.25 for a first device type when a number of transmission occasions is 2.

10. The method of any of claims 1-9, wherein the first factor is different from the second factor.

11. The method of any of claims 1-10, wherein the transmission offset is the first transmission offset in accordance to the transmission occasion being the first transmission occasion.

12. The method of any of claims 1-11, wherein a first duration of the first transmission occasion is the duration of the first message scaled by the second factor.

13. The method of any of claims 1-12, the selecting comprising: selecting, by the AIoT device, the transmission occasion from the first transmission occasion, the second transmission occasion, and a third transmission occasion, wherein a third duration of the third transmission occasion is greater than a second duration of the second transmission occasion, and wherein the second duration is greater than a first duration of the first transmission occasion.

14. A method, comprising: transmitting, by a reader device to an ambient Internet of Things (AIoT) device, a message; monitoring, by the reader device, a first transmission occasion for a transmission of a first message from the AIoT device based on a time offset after an end of the message; monitoring, by the reader device, a second transmission occasion for the transmission of the first message from the AIoT device based on a sum of the time offset scaled by a first factor and a duration of the first message scaled by a second factor after the end of the message; and in response to receiving the first message from the AIoT device, transmitting, by the reader device to the AIoT device, a second message after the second transmission occasion. FW 6000734PCT04 5115. The method of claim 14, wherein a first sum of the time offset and the duration of a second transmission offset equals a second sum scaled by the second factor, the second sum being of the time offset and the duration of the first message.

16. The method of any of claims 14-15, wherein the message is a reader to device (R2D) trigger message.

17. The method of any of claims 14-16, further comprising: transmitting, by the reader device to the AIoT device, an indication of a number of transmission occasions available for transmission of the first message following the end of the message.

18. The method of claim 17, wherein the message is an R2D trigger message, and wherein the R2D trigger message includes the indication of the number of transmission occasions.

19. The method of any of claims 14-18, wherein the first factor is greater than 1, and the second factor is greater than 1.

20. The method of claim any of claims 14-19, wherein the first factor and the second factor are the same.

21. The method of claim 20, wherein the second factor is a first sum of 1 and a term related to a device type, and wherein the term is 0.25 for a first device type when a number of transmission occasions is 2.

22. The method of any of claims 14-21, wherein the first factor is different from the second factor.

23. The method of any of claims 14-22, wherein a first duration of the first transmission occasion is the duration of the first message scaled by the second factor.

24. The method of any of claims 14-23, further comprising: monitoring, by the reader device, a third transmission occasion, wherein a third duration of the third transmission occasion is greater than a second duration of the second transmission occasion, and wherein the second duration is greater than a first duration of the first transmission occasion.

25. An ambient Internet of Things (AIoT) device, comprising: at least one processor; and a non-transitory computer readable storage medium storing programming, the FW 6000734PCT04 52programming including instructions that, when executed by the at least one processor, cause the AIoT device to perform a method according to any of claims 1-13.

26. A reader device, comprising: at least one processor; and a non-transitory computer readable storage medium storing programming, the programming including instructions that, when executed by the at least one processor, cause the reader device to perform a method according to any of claims 14-24.

27. A non-transitory computer-readable medium having instructions stored thereon that, when executed by an ambient Internet of Things (AIoT) device, cause the AIoT device to perform a method according to any of claims 1-13.

28. A non-transitory computer-readable medium having instructions stored thereon that, when executed by a reader device, cause the reader device to perform a method according to any of claims 14-24. FW 6000734PCT04 53

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