WO2021093200A1

WO2021093200A1 - Contention and priority based channel access in wireless communication networks

Info

Publication number: WO2021093200A1
Application number: PCT/CN2020/075062
Authority: WO
Inventors: Jing Shi; Peng Hao; Xing Liu; Wei Gou; Shuaihua KOU; Kai Xiao
Original assignee: Zte Corporation
Priority date: 2020-02-13
Filing date: 2020-02-13
Publication date: 2021-05-20
Also published as: CN114788389A

Abstract

This disclosure relates to contention based channel access to wireless channels in a shared-spectrum. Methods and systems are disclosed to incorporate a priority as a factor in a contention based channel access procedure. The priority is incorporates such that a service having higher priority may be provided a higher probability in successfully contenting for a channel in the shared-spectrum via the contention based channel access procedure.

Description

Contention and Priority Based Channel Access in Wireless Communication Networks

TECHNICAL FIELD

This disclosure is directed to contention and priority based channel access of shared channels in wireless communication networks.

BACKGROUND

Radio communication resources may be provided in a wireless access communication network for uplink and downlink transmission of data and control information. Such radio communication resources may be organized as wireless channels encompassing radio frequency resources and time slots. Such wireless channels may be shared by multiple wireless network devices and communication services therein. Each of these wireless network devices may contend with one another for the shared channels for its data and control information transmission corresponding to the various communication services. These communication services may be associated with different levels of service priorities.

SUMMARY

This disclosure relates to methods, systems, and devices for contention and priority based channel access of shared channels in wireless communication networks.

In some exemplary implementations, a method for wireless channel access is disclosed. The method may include determining a channel access priority class for a channel; obtaining a priority indicator for the channel; and performing a channel access procedure for transmission (s) comprising the channel based on the channel access priority class and the priority indicator.

In some other implementations, another method for wireless channel access is disclosed. The method includes determining a channel access priority class for a channel; obtaining a priority indicator for the channel; determining a set of allowed contention window sizes between a minimum contention window size and a maximum contention window size; and adjusting a contention window size to one of the set of allowed contention window sizes based on the priority indicator for use in a channel access procedure for transmission (s) comprising the channel.

In some other implementations, a network device is disclosed. The network device main include one or more processors and one or more memories, wherein the one or more processors are configured to read computer code from the one or more memories to implement any one of the methods above.

In yet some other implementations, a computer program product is disclosed. The computer program product may include a non-transitory computer-readable program medium with computer code stored thereupon, the computer code, when executed by one or more processors, causing the one or more processors to implement any one of the methods above.

The above embodiments and other aspects and alternatives of their implementations are explained in greater detail in the drawings, the descriptions, and the claims below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a wireless access network with an exemplary uplink, downlink, and control channel configuration.

FIG. 2 shows an exemplary mechanism for channel access of shared-spectrum uplink channels in a wireless access network.

FIG. 3 shows a logic flow for an exemplary contention based channel access procedure of a shared-spectrum uplink channel in a wireless access network.

FIG. 4 shows a logic flow for an exemplary contention window adjustment procedure for contention based channel access of a shared-spectrum uplink channel in a wireless access network.

DETAILED DESCRIPTION

A wireless communication network may include a radio access network for providing network access to wireless terminal devices, and a core network for routing data between the access networks or between the wireless network and other types of data networks. In a wireless access network, radio resources are provided for allocation and used for transmitting data and control information. FIG. 1 shows an exemplary wireless access network 100 including a wireless access network node or wireless base station 102 (herein referred to as wireless base station, or base station) and wireless terminal devices or user equipment (UE) 104 (herein referred to as user equipment or UE) that communicate with one another via over-the-air (OTA) radio communication resources 106. The wireless access network 100 may be implemented as, as for example, a 2G, 3G, 4G/LTE, or 5G cellular radio access network. Correspondingly, the base station 102 may be implemented as a 2G base station, a 3G node B, an LTE eNB, or a 5G New Radio (NR) gNB. The user equipment 104 may be implemented as mobile or fixed communication devices installed with mobile identity modules for accessing the base station 102. The user equipment 104 may include but is not limited to mobile phones, laptop computers, tablets, personal digital assistants, wearable devices, distributed remote sensor devices, and desktop computers. Alternatively, the wireless access network 100 may be implemented as other types of radio access networks, such as Wi-Fi, Bluetooth, ZigBee, and WiMax networks.

The radio communication resources 106 may include portions of licensed radio frequency bands, portions of unlicensed ration frequency bands, or portions of a mix of both licensed and unlicensed radio frequency bands. The radio communication resources 106 available for carrying the wireless communication signals between the base station 102 and user equipment 104 may be further divided into physical downlink channels 110 for transmitting wireless signals from the base station 102 to the user equipment 104 and physical uplink channels 120 for transmitting wireless signals from the user equipment 104 to the base station 102. The physical downlink channels 110 may further include physical downlink control channels (PDCCHs) 112 and physical downlink shared channels (PDSCHs) 114. Likewise, the physical uplink channels 120 may further include physical uplink control channels (PUCCHs) 122 and physical uplink shared channels (PUSCHs) 124. For simplification, other types of downlink and uplink channels are not shown in Figure 1 but are within the scope of the current disclosure. The control channels PDCCHs 112 and PUCCHs 122 may be used for carrying control information in the form of

control messages

116 and 126. The shared channels (shared between data and control information) PDSCHs 114 and PUSCHs 124 may be allocated and used for communicating downlink data transmissions 118 and uplink data transmissions 128 between the base station 102 and the user equipment 104.

In communications involving shared-spectrum (e.g., unlicensed frequency bands) , various devices (e.g., different UEs) and various communication services within each device may compete or contend for wireless channels within the shared-spectrum for data or control information transmission following a predefined contention based channel access procedure. The various implementations of this disclosure below provide a priority based contention mechanism for wireless channel access in a shared-spectrum. This mechanism, for example, may be applied to networks including but not limited to 4G LTE or 5G cellular networks for channel access of shared-spectrum in the context of license assisted access (LAA) .

Such a contention mechanism increases probabilities for communication services having higher priority to obtain channel access of the shared-spectrum during a channel access contention procedure. While the implementations below are mainly described in the context of contention based access of uplink channels, the underlying principles are not so limited and are applicable to contention based access of downlink channels. Such a contention mechanism is applicable to both control channels for transmission of control information and data channels for transmission of data. The word “shared” in the term “shared-spectrum” is used to refer to sharing of a same radio resource by different wireless devices or services via access contention, whereas the word “shared” in the term “shared channel” is used to refer to a channel for transmission of data information. As such, a channel in the shared-spectrum may be contended for by various wireless devices or communication services for use as either a control channel or a data channel for each of the contending wireless devices or services.

FIG. 2 illustrates an exemplary contention based channel access mechanism 200 for uplink channel access in a shared-spectrum in a wireless access network. As shown in FIG. 2, an uplink control channel such as a PUCCH 122 and/or an uplink shared channel such as PUSCH 124 may be contended for by various user equipment 104 supporting various communication services. A channel access by each of these services may be associated with a channel access priority class (CAPC) 202 and a priority indicator 204. Channel access in the contention based channel access mechanism 200 may be controlled by an interplay between the CAPC 202 and the priority indicator 204 for the underlying communication services needing access to

channels

122 or 124 in the shared-spectrum.

The contention based channel access mechanism described herein for the communication service may be performed at the level of data flows within a particular communication service. Such data flows within a communication service may be characterized by different transmission quality of service (QoS) requirements, as described in further detail below. While the description herein may referred to channel access by a particular communication service, the underlying principles apply to channel access at the data flow level. As such, the term “communication service” may be replaced by “communication service or data flow. ”

Continuing with FIG. 2, the CAPC 202 for a particular communication service may be determined based on various factors for channel access purposes. For example, the CAPC 202 may include one of a predetermined number of priority classes which may be correlated with quality-of-service (QoS) requirements for the communication service. In some implementations, as eluded to above, a communication service may be provided via multiple data flows with each data flow associated with a set of QoS requirements. Such data flows within a communication service may be referred to as QoS flows. In some exemplary implementations, the QoS requirements for each of the QoS flows may be associated with one of a predetermined number of QoS profiles. Each of these QoS profiles may be identified by a QoS profile identifier (QFI) . A QFI may be associated with a QoS class identifier (QCI) . The QCI may be specified by an upper layer. As such, the CAPC 202 for the communication service or data flow may be derived based on the QCI information and the correlation between QCI and the CAPC classes. Alternatively, the CAPC 202 may be indicated by downlink control signaling such as in a downlink control information (DCI) message from the base station.

The determination of the CAPC 202 among the predetermined number priority classes may additionally be based on other factors. For example, in some implementations, access to a channel in the shared-spectrum as a control channel, e.g., PUCCH, may always be assigned with a particular, e.g., the highest CAPC priority class of CAPC =1, irrespective of the nature of the underlying communication service or data flow. As such, the CAPC 202 for a communication service or data flow may be assigned to represent a mix of QoS requirements and other channel access and data characteristics of the communication services or data flow.

The priority indicator 204 for a particular communication service or data flow may be used to indicate the nature of the communication service in terms of its priority. For example, a communication service may belong to an ultra-reliable low latency communication (URLLC) service, an enhanced mobile broadband (eMBB) service, and the like. In some implementations, the priority indicator 204 may be specified as either being a high priority or a low priority. For example, URLLC service may be assigned with a priority indicator of high priority whereas services other than a URLLC service including an eMBB service may be assigned with a priority indicator of low priority. In other alternative implementations, more than one priority levels may be specified. The priority indicator 204 for the particular communication service or data flow may be specified in the DCI message from the base station and used together with the CAPC 202 for controlling the contention based channel access for the particular communication service or data flow.

As shown in further detail below, the combination of CAPC 202 and the priority indicator 204 in FIG. 2 for controlling channel access contention may enable improved probability of successful channel contention by communication services or data flows with higher priority (as indicated by the priority indicator) among services or data flows having a same CAPC. For example, PUCCH access for all communication services or data flows including URLLC and eMBB services/data flows may be assigned the same highest CAPC while it may be desired to provide better channel access success probabilities in a PUCCH contention process for a URLLC service/data flow than an eMBB service/data flow. Likewise, PUSCH access of a URLLC service/data flow may be assigned a same CAPC as an eMBB service while it may be desired to provide a better channel access success probability in a PUSCH contention process for the URLLC service/data flow than for the eMBB service/data flow. Making the channel contention process depend on the additional priority indicator that, for example, gives the URLLC service/data flow a high priority status and the eMBB service/data flow a low priority status would enable the URLLC service/data flow to have a better chance against the eMBB service/data flow in the channel access contention process.

The CAPC may include a predetermined number of classes. Merely as an example, the CAPC classes are predefined as four classes, represented in descending channel access priority from p =1, 2, 3, and 4. As described above, the p value for channel access of a communication service or data flow may be assigned/determined according rules involving QCI corresponding to the communication service or data flow and other channel access characteristics. For example, access to PUCCH may always be assigned p =1 (highest channel access priority class) . For another example in 5G wireless communication systems, PUSCH channel access for communication service/data flow with a first set of QCIs (e.g., QCIs of 1, 3, 5, 65-67, 69, 70, 79, 80, and 82-85) may be assigned with p =1, whereas PUSCH channel access for communication service/data flow with a second set of QCIs (e.g., QCIs of 2, and 7) may be assigned with p =2, and PUSCH channel access for communication service/data flow with a third set of QCIs (e.g., QCIs of 4, 6, 8, and 9) may be assigned with p =3. For another example, PUSCH channel access for URLLC service/data flow may be more likely to be assigned with p =1 whereas PUSCH channel access for eMBB service/data flow may be assigned with p =1, 2, 3, or 4.

FIG. 2 further shows that the contention based channel access mechanism 200 may include a contention based channel access procedure 210 executed by a user equipment when contending for channel access for a communication service or data flow. The channel contention procedure for a particular communication service or data flow may be executed according to a set of predefined channel access contention parameters corresponding to the CAPC (p value) of channel access for the communication service or data flow as modified or adjusted according to the priority indicator of the communication service/data flow.

Table 1 below shows an exemplary base set of channel access contention parameters for each of exemplary set of CAPC classes. For each CAPC p value, these channel access contention parameters may include but not limited to CW _p, CW _min, p, CW _max, p, and m _p. CW _p, represents a contention window selected from a predetermined set of contention window values between CW _min, p (minimum contention window for CAPC with p value) and CW _max, p (maximum contention window for CAPC with p value) . The exemplary allowed set of contention window values between the CW _min, p, CW _max, p for each p value are shown in Table 1 in the column labeled as “allowed CW _p sizes” . In some implementations, the allowed CW _p sizes for a higher channel access priority class (lower p value) may not be larger than the allowed CW _p sizes for a lower channel access priority class (higher p value) , as shown in Table 1. The defer parameter m _p may be used for determining a length of a time delay that a communication service or data flow may be allowed to obtain channel access for transmission.

Table 1

CAPC (p)	m _p	CW _min, p	CW _max, p	Allowed CW _p sizes
1	2	3	7	{3, 7}
2	2	7	15	{7, 15}
3	3	15	1023	{15, 31, 63, 127, 255, 511, 1023}
4	7	15	1023	{15, 31, 63, 127, 255, 511, 1023}

The exemplary principles underlying the contention based channel access procedure 210 are described are as follows. Essentially, a UE that begins contending access to an uplink channel (either PUCCH or PUSCH in the shared-spectrum) for a communication service or data flow with channel access priority class p may not obtain access. Rather, the UE may be forced to go through N time periods of lengths depending on the channel status (e.g., idle or busy) until access can be granted and transmission can be made. The number N may be set as a random number between 0 and CW _p (which may be one of set of allowed CW _p sizes between CW _min, p and CW _max, p) , the determination of which is described in more detail below in relation to FIG. 4. As the CW _p for a communication service or data flow having a lower p value (higher priority class) may not be larger than a communication service or data flow having a higher p value (lower priority class) , the higher CAPC class communication service or data flow may be provided a higher probability of having a lower N number and thus a higher probability of successfully contention and gaining earlier channel access.

Additionally, the contention based channel access procedure 210 incorporates priority (as reflected in the priority indicator) of the communication service or data flow such that within contending communication services or data flows having a same CAPC class p value, the one with higher priority would have higher probability of successful contention and earlier access to the shared channel for transmission.

Furthermore, the contention based channel access mechanism 200 may include a contention window adjustment procedure 220 for the UE 104 to determine and adjust in time the contention window CW _p among the allowed CW _p sizes for each of the CAPC classes (p values) . As described in more detail in relation to FIG. 4, the contention window adjustment procedure 220 may depend on priority indicator for each CAPC class. As such, contention window adjustment procedure 220 may be designed such that it generate adjusted CW _p in a manner that benefits channel access contention for communication services or data flows having higher priority (as indicated by its priority indicator) in a particular CAPC class.

Moving on from FIG. 2, FIG. 3 shows an exemplary logic flow for the contention based channel access procedure 210 of FIG. 2 for a communication service or data flow having a CAPC value of p and a priority indicator being of either a high priority or a low priority. The priority indicator may be indicated from the base station via a DCI. For example, in a 5G wireless communication system, an indication of a PUSCH access being given a high priority may be provided by the base station via DCI format 0_1/0_2 whereas an indication of a PDSCH/PUCCH access being given a high priority may be provided by the base station via DCI format 1_1/1_2.

In the contention based channel access procedure 210 of FIG. 2, a counter N is initiated to a random number between 0 and the contention window CW _p, and is counted down iteratively after the UE determines that the channel is idle for some time duration in each iteration. The UE may gain access to the channel for transmission after the counter N counts down to 0. Various alternatives for incorporating the priority information into the contention based channel access procedure 210 (such as shown in

steps

301, 302, 308, 310, and 314) may promote channel access contention for communication services or data flows having higher priority as indicated by the priority indicator.

As shown in step 301 of FIG. 3, the UE may first sense the channel until the channel is idle for a period of time before step 302. The length of the time period and the sensing of the channel state may be configured in any manner, such as the manner described below with respect to steps 314. As shown in step 302, the UE sets a counter N to N _init, where N _init is set to a random number between 0 and contention window CW _p. The CW _p may be selected from the allowed CW _p sizes in the base Table 1 for CAPC class p. The larger the CW _p size, the higher probability that random N _init is a larger number and the less favored is the communication service or data flow during the channel contention process.

In some implementations of the step 301, the CW _p selection may be made dependent on the priority indicator. For example, the CW _min, p or CW _max, p values in the base Table 1 may be adjusted based on the priority indicator. Specifically, CW _min, p for higher priority within the same p class may be adjusted to a smaller value. Additionally or alternatively, CW _min, p for lower priority within the same p class may be adjusted to a larger value, as illustrated in Tables 2 and 3 below. Additionally or alternatively, the CW _max, p for higher priority within the same p class may be adjusted to a smaller value. Additionally or alternatively, CW _max, p for lower priority within the same p class may be adjusted to a larger value, as illustrated in Tables 4 and 5 below. The allowable CWp sizes in Tables 2-5 may be correspondingly modified according to the modifications of CW _min, p and/or CW _max, p. The downward modification of the CW _min, p and/or CW _max, p for higher priority and/or the upward modification of the CW _min, p and/or CW _max, p for lower priority may promote channel access contention by services or data flows having higher priority because the random N _init generated in step 302 and under these modifications may have a higher probability of being a smaller number for services or data flows having higher priority.

In the Tables 2-5, the priority consideration is only applied to CAPC with p=1 as examples. However, the underlying principle of adjusting the CW _min, p and CW _max, p parameter away from its base value to depend on priority indicator can be extended to other p classes. Further, the priority indicator may not necessarily be limited to binary values (high level priority or low level priority) . The priority may contain more than two levels and the CW _min, p and CW _max, p values for each of the more than two priority levels within a CAPC class may be modified accordingly to achieve lower N _init for higher priority.

Table 2

Table 3

Table 4

Table 5

At Step 304, the UE determines whether the counter N is 0. If UE determines that the counter N is 0, then the contention based channel access procedure 210 for the communication service/data flow stops and the UE is allowed to transmit over the channel, as shown by step 306. Otherwise, the UE counts down the counter N by 1 or alternatively, by a step size dependent on the priority indicator, as shown in 308. For example, the countdown step size for the counter N may be set at a larger value for higher priority and a smaller value for lower priority as indicated by the priority indicator. In a specific example, the countdown step size may be set to 1 for lower priority indicator priority and 2 for higher priority indicator priority. Other countdown step sizes for the counter N may be used. By setting the countdown step size for the counter N depending on the priority indicator, the counter N may reaches 0 in fewer iterations in the contention based channel access procedure 210 and thus the UE has a higher probability for obtaining earlier channel access for communication service or data flow of higher priority.

Following step 308 of FIG. 3, the UE senses the channel state for an additional sensing time slot duration T _sl to determine whether the channel is idle, as shown by step 310. The sensing time slot duration T _sl may be predefined at any suitable time length. For example, T _sl may be predefined as 9 μs. During a sensing time slot duration T _sl, the UE measures a time varying energy level in the channel and compare the measurement with a predetermined energy threshold E _t to determine whether the channel is considered idle during the sensing time slot duration. In some implementations, a time period T _le within a sensing time slot duration may be predefined. If the measured energy level is below the E _t for at least the time period T _le within T _sl, the UE may determine that the channel is idle for the sensing time slot duration. Otherwise, the UE may determine that the channel is busy during the sensing time slot duration T _sl. Alternatively, the UE may compare a time-average of the measured energy level during the sensing time slot duration with the E _t, and determines that the channel is idle when the time-average is below or equal to the E _t and that the channel is busy when the time-average is above the E _t.

As further shown in step 310 of FIG. 3, the priority information may be incorporated into step 310 to facilitate more favored channel access contention for communication services or data flows having higher priority. For example, the channel detection energy threshold E _t may be set at a higher value when the priority indicator indicates a high priority whereas the E _t may be set at a lower value when the priority indicator indicates a low priority. Such implementations favor channel access contention by a communication service or data flow having a high priority by increasing the probability that the UE that contends for channel access for the communication service or data flow having high priority would detect an idle channel compared with another UE that contends for channel access for a communication service or data flow having low priority.

At step 312 of FIG. 3, if the UE detects that the channel is idle in step 310 during the sensing time slot duration, then the UE iterates back to step 304. Otherwise, the UE proceeds to step 314 for additional channel state detection. As shown by step 314 in Figure 3, the UE may further sense the state of the channel for a defer time duration T _d. The sensing may be performed with a time granularity of the sensing time slot duration T _sl described in step 308. Again, during each sensing time slot duration T _sl within T _d, the UE measures the time-varying energy level in the channel and compare the measurement with the predetermined energy threshold E _t to determine whether the channel is idle during the sensing time slot duration T _sl. For example, if an accumulative time for the measured energy level below the predetermined energy threshold E _r is at least the time period T _le, the UE may determine that the channel is idle. Otherwise, the UE may determine that the channel is busy during the sensing time slot duration T _sl. Alternatively, the UE may compare a time-average of the measured energy level during the sensing time slot duration with the E _t, and determines that the channel is idle when the time-average is below or equal to the E _t and that the channel is busy when the time-average is above the E _t. The defer time period T _d may be generally determined as T _d = T _f + m _p *T _sl, where T _f may be a predetermined time length (e.g., 16 μs) and a base m _p may be predetermined by, for example, Table I according to the CAPC p class value. As such, the defer time duration T _d contains multiple sensing time slot durations. In the exemplary step 314, the UE senses the channel until either (1) a busy sensing time slot duration for the channel is detected, or (2) the channel is detected as being idle for all sensing time slot durations within T _d.

As further shown in step 314 of FIG. 3, the priority information may be incorporated into step 314 to facilitate more favored channel access contention for communication service or data flow having higher priority in at least two different manners. In a first manner that is similar to that describe above in step 310, the channel detection energy threshold the E _t may be set at a higher value when the priority indicator indicates a high priority whereas the E _t may be set at a lower value when the priority indicator indicates a low priority. Such implementations favor channel access contention by a communication service or data flow having a high priority by increasing the probability that the UE that contends for channel access for the communication service or data flow having high priority would detect an idle channel for all sensing time slot durations during the defer time duration T _d compared with another UE that contends for channel access for a communication service or data flow having low priority.

In a second manner, the base m _p in Table 1 may be adjusted based on the priority indicator such that the defer time duration T _d is shorter (containing less number of sensing time slot durations) for channel access contention for a communication service or data flow having higher priority than for a communication service or data flow having lower priority, thereby promoting channel access contention by the communication service or data flow having higher priority. Tables 6 and 7 below illustrates an effective channel access parameters (m _p, in particular) to this effect. The examples of the effective tables in Tables 6 and 7 are based on the base Table 1 with the base m _p parameter being modified to depend on the priority indicator. Particularly in the exemplary Table 6, the m _p value for the p=1 is maintained at the base value of 2 (Table 1) for low priority whereas the m _p value for p=1 is down adjusted to 1 from the base value of 2 for high priority. In the exemplary Table 7, the m _p value for the p=1 is maintained at the base value of 2 (Table 1) for high priority whereas the m _p value for p=1 is up adjusted to 3 from the base value of 2 for low priority. In the Tables 6 and 7, priority consideration is only applied to CAPC with p=1 as examples. However, the underlying principle of adjusting the m _p parameter away from its base values to depend on priority indicator can be extended to other p classes. Further, the priority indicator may not necessarily be limited to binary values (high or low service priorities) . The priority may contain more than two levels and the m _p values for each of the more than two priority levels within a CAPC class may be adjusted accordingly to achieve lower m _p for higher priority.

Table 6

Table 7

Continuing with FIG. 3 and in step 316, if the UE detects that the channel is idle in all sensing time slot durations during the additional defer time period T _d, it completes the current iteration of counting down the counter N and returns to step 304 for the next iteration. However, if the UE detects a busy sensing time slot duration in step 314 for the channel, the UE repeats step 314 for another additional defer time period T _d until all sensing time slot durations during the T _d are idle for the channel.

Turning to the contention window adjustment procedure 220 of FIG. 2 and as described above with respect to step 302 of FIG. 3, the contention window CW _p plays a critical role in the contention based channel access procedure 210 in that CW _p is essentially used by the UE to specify the N _init value above as a random number between 0 and CW _p. The parameter CW _p may be any one of the allowed CW _p sizes between CW _min, p and CW _max, p, as shown, for example, in the base channel access contention parameter Table 1. CW _p, for example, may be implemented as a single parameter maintained by a UE for channel access contention procedures for all communication services or data flows from the UE having the same p class. In other words, each of the UEs 104 in FIG. 2 may main a single CW _p for each of the CAPC classes. The CW _p is a time-dependent contention window size that may be adjusted using the contention window adjustment procedure 220 of FIG. 2.

For each CAPC class p, the CW _p may be initialized to the smallest value in the allowed CW _p sizes of the base Table 1, which may be, for example, the minimum contention window CW _min, p. The purpose of adjusting the CW _p is to prevent channel contention congestion and deadlock based on retransmission and retransmission acknowledgement information particularly by stretching out CW _p to result in larger N _init and thus longer channel contention time for each contention based channel access procedure (FIG. 3) in the CAPC class by the UE. The contention window adjustment procedure 220 in FIG. 2 may incorporate priority information such that channel access contention by communication services or data flows having higher priority (as indicated by its priority indicator) may be favored during the contention based channel access procedure 210.

FIG. 4 shows an exemplary logic flow for the contention window adjustment procedure 220 of FIG. 2. At step 402, the contention window for each CAPC class p is set to CW _min, p. At step 404, the UE determines whether there is any retransmission feedback for communication services or data flows of the CAPC class since the previous CW _p update. If retransmission acknowledgement (s) has been received since the previous CW _p update, the UE determines whether there are sufficient acknowledgement for successful retransmission (referred to as ACK) at step 408. For example, the UE may determine whether the acknowledgement of successful retransmission is over some predetermined ACK threshold. In some exemplary implementations, the UE may determine whether ACK is over the ACK threshold by determining whether ACK for PUSCH (s) with transport block (TB) based transmission is received or at least 10% (merely as an exemplary percentage) of HARQ (hybrid automatic repeat request) feedbacks are ACK for PUSCH (s) with code block group (CBG) based transmission. If the received ACK is over the ACK threshold, the UE maintains the CW _p at CW _min, p, as shown by branching arrow 409. Otherwise, the UE proceed to step 412.

If retransmission acknowledgement (s) has been received since the previous CW _p update as determined in step 404, the UE determines at step 406 whether the reason that retransmission ACK is not received is because either that retransmission has not been performed since the previous CW _p update or that there have been retransmissions but there has not be sufficient time to receive any feedback. If the UE determines and confirms either of these two reasons, it maintains the current CW _p size, as shown by 410 and branching arrow 407. Otherwise, when retransmissions have been performed and sufficient time has lapsed since the retransmissions and feedback is expected but there has been no feedback, the UE increase CW _p to the next higher value in the allowed CW _p sizes in the base Table 1 for the CAPC class, as shown by 414 and the branching arrow 413.

After the UE determines that retransmission feedback has been received after previous CW _p update (step 404) and that the received amount of ACK is not over the ACK threshold (step 408) , the UE may determine the priority for the current communication service or data flow of CAPC class p participating in the channel contention, as shown in step 412. If the UE determines that the current priority indicator indicates low priority, it increases the CW _p to the next higher size among the allowed CW _p sizes in the base Table 1, as shown by 414 and the branching arrow 431. However, if the UE determines that the current priority indicator is of high priority, the UE may be provided with three options for adjusting the CW _p. In a first option, as shown by the branching arrow 432, the UE may reset the CW _p size to CW _min, p. In a second option, as shown by the branching

arrow

430 and 410, the UE may maintain the current CW _p size. In a third option, as shown by the branching

arrow

434 and 416, 410, and 418, the UE may maintain CW _p at CW _min, p if CW _p is already at CW _min, p or decrease CW _p to the next smaller value in the allowed CW _p sizes in the base Table 1.

As such, the contention window adjustment procedure 220 in FIG. 4 facilitates adjustment of CW _p during channel access contention by communication services or data flows having higher priority (as indicated by their SPIs) to smaller sizes within the allowed CW _p sizes in situation where channel access is congested into, e.g., contention deadlocks.

As described above with respect to FIGs. 2-4, a priority indicator is introduced in downlink control signaling. Further, a contention based channel access procedure and a contention window adjustment procedure incorporate various exemplary alternatives that take the priority indicator of a contending communication service or data flow into consideration such that services or data flows of higher priority is provided with relatively higher probability in successfully obtaining earlier access to the contended channel. Any number of these options may be incorporated in the procedures above and may be combined in any manner.

Finally, returning to FIG. 3 and Tables 2-5 above, the step 302 of the contention based channel access procedure 210 is implement by explicitly introducing priority levels into the set of CAPC classes. Such a step may alternatively be implemented by modifying the number of the CAPC classes and their channel access contention parameters of the base Table 1 and/or the assignment of CAPC classes to implicitly incorporate the priority designation for services or data flows.

For example, in assigning a CAPC class, the highest CAPC class of p=1 may be exclusively assigned to channel access (either PUSCH or PUCCH) for services/data flows having high priority. URLLC services may then be generally associated with high priority and as such, would be assigned p=1. Channel access (including PUCCH and PUSCH channel access) by services such as eMBB services that do not have a high priority designation may be assigned to lower CAPC classes. In such a manner, URLLC services would gain advantage during a channel access contention.

In some implementations, the CAPC classes may be expanded to more than 4. For example, the CAPC classes may be expanded to include p = {1, 2, 3, 4, 5} , with p=1 reserved for high priority. Within channel access for services or data flows not having high priority designation, PUCCH access, for example, may be associated with p=2 (the highest CAPC classes not assigned to high priority) . Likewise, the CAPC classes may be expanded to more than 5, with the highest class reserved to high priority services and data flows.

In yet some other implementations, a mapping may be provided between the CAPC classes (expanded or no expanded) and the priority. Out of an exemplary CAPC set of p= {1, 2, 3, 4} , a subset of p may be mapped to high priory and another subset of p may be mapped to low priority. For example, {1} may be mapped to high priority whereas {3, 4} may be mapped to low priority (in this case, {2} would be assigned to services or data flows having no priority designation) . For another example, {1, 2} may be mapped to high priority whereas {4} may be mapped to low priority (in this case, {3} would be assigned to services or data flows having no priority designation) . Any other combination of CAPC mappings to high priority and low priority may be used. In some exemplary mappings, a union of the high priority CAPC class subset and the low priority CAPC class subset may encompass the entire CAPC class set. For example, {1} may be mapped to high priority whereas {2, 3, 4} may be mapped to low priority. For another example, {1, 2} may be mapped to high priority whereas {2, 3, 4} may be mapped to low priority. In other words, the subsets may overlap.

The description and accompanying drawings above provide specific example embodiments and implementations. The described subject matter may, however, be embodied in a variety of different forms and, therefore, covered or claimed subject matter is intended to be construed as not being limited to any example embodiments set forth herein. A reasonably broad scope for claimed or covered subject matter is intended. Among other things, for example, subject matter may be embodied as methods, devices, components, systems, or non-transitory computer-readable media for storing computer codes. Accordingly, embodiments may, for example, take the form of hardware, software, firmware, storage media or any combination thereof. For example, the method embodiments described above may be implemented by components, devices, or systems including memory and processors by executing computer codes stored in the memory.

Throughout the specification and claims, terms may have nuanced meanings suggested or implied in context beyond an explicitly stated meaning. Likewise, the phrase “in one embodiment/implementation” as used herein does not necessarily refer to the same embodiment and the phrase “in another embodiment/implementation” as used herein does not necessarily refer to a different embodiment. It is intended, for example, that claimed subject matter includes combinations of example embodiments in whole or in part.

In general, terminology may be understood at least in part from usage in context. For example, terms, such as “and” , “or” , or “and/or, ” as used herein may include a variety of meanings that may depend at least in part on the context in which such terms are used. Typically, “or” if used to associate a list, such as A, B or C, is intended to mean A, B, and C, here used in the inclusive sense, as well as A, B or C, here used in the exclusive sense. In addition, the term “one or more” as used herein, depending at least in part upon context, may be used to describe any feature, structure, or characteristic in a singular sense or may be used to describe combinations of features, structures or characteristics in a plural sense. Similarly, terms, such as “a, ” “an, ” or “the, ” may be understood to convey a singular usage or to convey a plural usage, depending at least in part upon context. In addition, the term “based on” may be understood as not necessarily intended to convey an exclusive set of factors and may, instead, allow for existence of additional factors not necessarily expressly described, again, depending at least in part on context.

Reference throughout this specification to features, advantages, or similar language does not imply that all of the features and advantages that may be realized with the present solution should be or are included in any single implementation thereof. Rather, language referring to the features and advantages is understood to mean that a specific feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the present solution. Thus, discussions of the features and advantages, and similar language, throughout the specification may, but do not necessarily, refer to the same embodiment.

Furthermore, the described features, advantages and characteristics of the present solution may be combined in any suitable manner in one or more embodiments. One of ordinary skill in the relevant art will recognize, in light of the description herein, that the present solution can be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments of the present solution.

Claims

A method for wireless channel access for a communication node, comprising:

determining a channel access priority class for a channel;

obtaining a priority indicator for the channel; and

performing a channel access procedure for transmission (s) comprising the channel based on the channel access priority class and the priority indicator.
The method of claim 1, wherein performing the channel access procedure comprises:

determining a set of channel access contention parameters according to the channel access priority class and the priority indicator; and

performing the channel access procedure based on the set of channel access contention parameters.
The method of claim 2, wherein:

the set of channel access contention parameters comprise a maximum contention window size and a minimum contention window size; and

determining the set of channel access contention parameters comprises determining at least one of the maximum contention window size and the minimum contention window size according to the priority indicator in addition to the channel access priority class.
The method of claim 3, wherein determining the maximum contention window size further comprises determining the maximum contention window size according the priority indicator in a manner such that the determined maximum contention window size is not larger than another maximum contention window size that would have be determined for the same channel access priority class but a priority level lower than that indicated by the priority indicator.
The method of claim 3, wherein determining the minimum contention window size further comprises determining the minimum contention window size according the priority indicator in a manner such that the determined minimum contention window size is not larger than another minimum contention window size that would have be determined for the same channel access priority class but a priority level lower than that indicated by the priority indicator.
The method of claim 3, wherein:

preforming the channel access procedure depends on a contention window size; and

the contention window size is selected from a set of allowed contention window sizes between the minimum contention window size and the maximum contention window size inclusive.
The method of claim 2, wherein:

the set of channel access contention parameters comprise a channel access contention time factor; and

determining the set of channel access contention parameters comprises determining the channel access contention time factor according to the priority indicator in addition to the channel access priority class.
The method of claim 7, wherein determining the channel access contention time factor further comprises determining the channel access contention time factor according the priority indicator in a manner such that the determined channel access contention time factor is not larger than another channel access contention time factor that would have be determined for the same channel access priority class but a priority level lower than that indicated by the priority indicator.
The method of claim 8, wherein the channel access contention time factor controls a time length of a channel contention process in the channel access procedure.
The method of claim 2, wherein:

the set of channel access contention parameters comprise a channel energy level threshold for determining whether the channel is active or idle at a particular time; and

determining the set of channel access contention parameters comprises determining the channel energy level threshold according to the priority indicator in addition to the channel access priority class.
The method of claim 1, wherein:

performing the channel access procedure based on the channel access priority class and the priority indicator comprises an iterative countdown of a counter with a countdown step size until the counter reaches zero.
Method of claim 11, wherein the countdown step size is larger when the priority indicator indicates a high priority than when the priority indicator indicates a low priority.
The method of claim 11, wherein each iteration during the iterative countdown of the counter in the channel access procedure comprises detecting an idle status of the channel for a contention time iteration duration.
The method of claim 13, wherein detecting the idle status of the channel for a contention time iteration duration is based on a contention energy threshold for energy detected in the channel.
The method of claim 14, wherein the contention energy threshold is higher when the priority indicator indicates a high priority than when the priority indicator indicates a low priority.
A method for wireless channel access, comprising:

determining a channel access priority class for a channel

obtaining a priority indicator for the channel;

determining a set of allowed contention window sizes between a minimum contention window size and a maximum contention window size; and

adjusting a contention window size to one of the set of allowed contention window sizes based on the priority indicator for use in a channel access procedure for transmission (s) comprising the channel.
The method of claim 16, wherein adjusting the contention window size comprises maintaining a previous contention window size, resetting the previous contention window size to the minimum contention window size, or modifying the contention window size from the previous contention window size to an adjacent contention window size among the set of allowed contention window sizes.
The method of claim 17, wherein modifying the contention window size comprises decreasing the previous contention window size to the adjacent contention window size among the set of allowed contention window sizes when the priority indicator indicates a high priority.
The method of claim 16, wherein adjusting the contention window size to one of the set of allowed contention window sizes based on the priority indicator comprises at least one of:

when the priority indicator indicates a high priority and retransmission feedback received since a previous adjustment of the contention window size indicates that acknowledgement of successful retransmission is below a predetermined acknowledgement threshold, maintaining a previous contention window size, resetting to or continuing to use the minimum contention window size, or decreasing from the previous contention window size; or

when the priority indicator indicates a low priority and retransmission feedback received since a previous adjustment of the contention window size indicates that acknowledgement of successful retransmission is below the predetermined acknowledgement threshold, increasing from the previous contention window size.
A wireless network device comprising one or more processors and memories for storing computer instructions, wherein the one or more processors, when executing the computer instructions, are configured to cause the wireless network device to implement a method of any one of claims 1 to 19.
A computer program product comprising a non-transitory computer-readable program medium with computer code stored thereupon, the computer code, when executed by one or more processors, causing the one or more processors to implement a method of any one of claims 1 to 19.