Patent Description:
"<NPL> discusses a non-homogeneous per-slot Markov chain model to represent the state of each priority class during and after AIFS, and analyzes the channel access probability, successful transmission probability and average throughput of each class. 3GPP Draft R1-<NUM> "Channel access procedures for NR-U", Samsung, discusses design considerations for sub-<NUM> NR-U channel access, including the baseline channel access framework, no-LBT option, LBT for wide-band operations, LBT with handshake mechanism, LBT for SS/PBCH blocks and random access, and LBT for FBE-based BR-U.

A UE may be a cellular phone (e.g., a smart phone), a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, a tablet, a camera, a gaming device, a netbook, a smartbook, an ultrabook, a medical device or equipment, a biometric sensor or device, a wearable device (smart watches, smart clothing, smart glasses, smart wrist bands, smart jewelry (e.g., smart ring, smart bracelet)), an entertainment device (e.g., a music or video device, or a satellite radio), a vehicular component or sensor, smart meters/sensors, industrial manufacturing equipment, a global positioning system device, or any other suitable device that is configured to communicate via a wireless or wired medium.

Controller/processor <NUM> of base station <NUM>, controller/processor <NUM> of UE <NUM>, and/or any other component(s) of <FIG> may perform one or more techniques associated with a prioritization scheme for a decentralized channel access mechanism, as described in more detail elsewhere herein. For example, controller/processor <NUM> of base station <NUM>, controller/processor <NUM> of UE <NUM>, and/or any other component(s) of <FIG> may perform or direct operations of, for example, process <NUM> of <FIG> and/or other processes as described herein. Memories <NUM> and <NUM> may store data and program codes for base station <NUM> and UE <NUM>, respectively.

In some aspects, UE <NUM> may include means for determining a window in which a communication is to be transmitted, wherein the communication is associated with a priority level; means for determining an earliest slot, of the window, in which the wireless communication device is permitted to transmit the communication, wherein the earliest slot is determined based at least in part on the priority level; means for mapping the communication to a resource based at least in part on the earliest slot and based at least in part on which resources, of the earliest slot, are occupied resources associated with another communication having a higher priority level; means for identifying the occupied resources based at least in part on the other communication, wherein the other communication at least partially occurs in an earlier slot or window than the earliest slot or the window; means for transmitting the communication on the resource; and/or the like. In some aspects, such means may include one or more components of UE <NUM> described in connection with <FIG>.

Some network deployments may use a distributed channel access mechanism, wherein a central scheduler does not perform scheduling for a channel. Examples of distributed channel access mechanisms include random resource selection, listen-before-talk (LBT) based resource selection, request-response based resource selection (e.g., with transmit/receive yielding based at least in part on a request and a corresponding response), long-term sensing-based resource selection, and/or the like. These distributed channel access mechanisms may provide mechanisms for channel access within a slot, and are therefore referred to herein as slot-based distributed channel access mechanisms.

Each distributed channel access mechanism may have a chance of collision between two or more transmissions. The probability of a collision may depend on the channel access mechanism. For example, random resource selection may result in the highest collision probability of the above distributed channel access mechanisms, but may be associated with less overhead than the other distributed channel access mechanisms (e.g., due to the lack of contention communications). As another example, an LBT-based access mechanism may create guard zones around transmitters, so for a typical receiver, the probability of collision is less than that of a random resource selection mechanism.

Different distributed channel access network deployments, or even UEs within a distributed channel access network deployment, may use different channel access mechanisms (e.g., random resource selection, LBT, request-response, and/or the like). Furthermore, some priority systems for communication in a distributed channel access network deployment focus on ensuring that latency requirements are met. However, in some cases, reliability may be more important than latency, such as when a latency in a mechanical reaction to a communication is larger than a latency in the communication.

Some techniques and apparatuses described herein provide a reliability-focused priority system for a distributed channel access mechanism. For example, some techniques and apparatuses described herein may use a priority contention window that includes a plurality of slots that are each associated with a respective priority level. In some aspects, the priority level may be in descending order starting with a first slot of the plurality of slots. A UE may determine an earliest slot in which a communication can be transmitted based at least in part on a priority level of the communication. The UE may then identify resources of the earliest slot that are unavailable for various reasons, as described in more detail below. The UE may map the communication to a resource of the earliest slot (when sufficient resources are available) or to a later slot (when sufficient resources of the earliest slot are not available, or when a collision with a lower-priority communication is acceptable). This priority system may be compatible with, and/or may be applied in conjunction with, the slot-based distributed channel access mechanisms described above (e.g., LBT, request-response, random resource selection, and/or the like). In this way, reliability requirements for communications may be satisfied while allowing slot-based distributed channel access mechanisms to be performed. For example, using an approach wherein a communication can be mapped to an earliest permitted slot, or to a later slot, may increase the likelihood that a suitable slot can be found for the communication, thereby improving reliability of the communication.

<FIG> is a diagram illustrating an example <NUM> of a set of priority contention windows for a reliability-focused priority system for a distributed channel access mechanism, in accordance with various aspects of the present disclosure. As shown in <FIG>, and by reference number <NUM>, a set of slots may be included in a priority contention window. In some cases, a priority contention window may be referred to herein as a window. Each slot may include a set of time resources (e.g., symbols) and a set of frequency resources (e.g., tones, subcarriers, bandwidth parts, and/or the like). As one example, each slot may include <NUM> symbols. In some aspects, a resource may be referred to as a time-frequency resource (TF resource), which may refer to a particular symbol or set of symbols and a particular frequency or set of frequencies. In example <NUM>, there are N slots, corresponding to N possible priority levels for communications to be transmitted using the distributed channel access mechanism.

In some aspects, a slot may be associated with multiple priority levels. For example, a first slot may be associated with a priority level of <NUM>, and a second slot may be associated with priority levels of <NUM> and <NUM>. In some aspects, different contention windows may have slots with different combinations of priority levels. For example, a first priority contention window may include even priority level slots, and a second priority contention window may include odd priority level slots. As another example, all priority contention windows of a set of priority contention windows may include a highest priority level slot, and a lower priority level slot may be included in less than all priority contention windows of the set of priority contention windows.

To transmit a communication in accordance with the priority system, a wireless communication device (e.g., UE <NUM>, BS <NUM>, and/or the like) may determine a priority level of the communication. The wireless communication device may determine a priority contention window within which the wireless communication device is to transmit the communication. For example, the wireless communication device may determine the priority contention window as a current priority contention window (e.g., when a slot corresponding to the priority level of the communication has not yet occurred), as a next priority contention window (e.g., when a slot corresponding to the priority level of the communication has already occurred) or as another priority contention window (e.g., based at least in part on traffic conditions, channel conditions, and/or the like).

The wireless communication device may determine an earliest slot, within the priority contention window, in which the wireless communication device is permitted to transmit the communication. For example, the wireless communication device may identify an earliest slot corresponding to the priority level of the communication. As a more particular example, if the communication is associated with a priority level of <NUM>, the wireless communication device may identify the slot in the priority contention window that has the priority level of <NUM> as the earliest slot.

The wireless communication device may identify resources (e.g., time resources, frequency resources, or TF resources) in the earliest time slot that are occupied resources. An occupied resource may be a resource that is reserved for another communication or that is expected to be reserved for another communication. In some aspects, the wireless communication device may identify a resource of an earliest slot as an occupied resource when the resource is used by a higher-priority communication in an earlier slot than the earliest slot (e.g., an earlier slot in the priority contention window). In some aspects, the wireless communication device may identify a resource of an earliest slot as an occupied resource when the resource is used by a communication (e.g., a higher-priority communication) in a previous priority contention window.

In some aspects, the wireless communication device may identify an occupied resource based at least in part on decoding a control transmission. For example, the wireless communication device may identify a number of slots and a resource block allocation of a communication using the control transmission. In some aspects, the wireless communication device may identify an occupied resource based at least in part on a channel measurement. For example, the wireless communication device may identify an occupied resource based at least in part on a reference signal received power (RSRP) value or another channel measurement value satisfying a threshold, indicating that the occupied resource is in use for another communication.

In some aspects, the wireless communication device may select a resource based at least in part on the earliest time slot. For example, the wireless communication device may select a resource in the earliest time slot when available resources (e.g., resources of the earliest slot other than the occupied resources of the earliest time slot) are sufficient for the communication, or may select a resource in a later time slot. In some aspects, the wireless communication device may select the resource in the later time slot when available resources of the earliest time slot are insufficient for the communication. In some aspects, the wireless communication device may select the resource in the later time slot when a collision with a lower-priority communication is acceptable (for example, when latency requirements can no longer be met if the device waits until the next priority contention window). For example, another wireless communication device that transmits the lower-priority communication may not know that the wireless communication device has selected the resource in the later time slot, since the wireless communication device did not transmit in the earliest slot. Therefore, a collision may be possible.

In some aspects, the wireless communication device may select a resource based at least in part on a slot-level decentralized channel access mechanism. For example, the wireless communication device may select a resource within a slot (e.g., the earliest slot or a later slot) based at least in part on the slot-level decentralized access mechanism. As a particular example, the wireless communication device may select the resource based at least in part on a random resource allocation technique or a pseudorandom resource allocation technique. As another example, the wireless communication device may select the resource based at least in part on an LBT technique or a request-response technique. Thus, slot-level decentralized channel access mechanisms may be used to select resources within a slot for a communication, while the reliability-focused priority system may be used to select a slot for the communication.

For a more detailed example of selecting resources for communications of different priority levels by a plurality of wireless communication devices, refer to the description accompanying <FIG>.

<FIG> is a diagram illustrating an example <NUM> of selecting resources for a set of communications based at least in part on a reliability-focused priority system for a distributed channel access mechanism, in accordance with various aspects of the present disclosure. As shown, example <NUM> includes a priority contention window that includes <NUM> slots. Each slot is associated with a respective priority level, from Priority <NUM> (a highest priority level) to Priority <NUM> (a lowest priority level). The vertical axis represents frequency and the horizontal access represents time. As shown by reference number <NUM>, a set of UEs (e.g., UE-<NUM>, UE-<NUM>, UE-<NUM>, and UE-<NUM>) (not shown in <FIG>) may transmit communications associated with respective priority levels. Here, UE-<NUM>'s communication is associated with a priority level of <NUM>, UE-<NUM>'s communication is associated with a priority level of <NUM>, UE-<NUM>'s communication is associated with a priority level of <NUM>, and UE-<NUM>'s communication is associated with a priority level of <NUM>. While the operations described in connection with <FIG> are described as being performed by UEs, these operations may be performed by any wireless communication device.

Each UE may select resources for the corresponding communication in accordance with the procedure described in connection with <FIG>. The selection of the resources is described in turn for each UE below.

As indicated above, UE-<NUM>'s communication is associated with a priority level of <NUM>. Therefore, the earliest slot in which UE-<NUM> is permitted to transmit is the first slot (e.g., Priority <NUM>). Therefore, UE-<NUM> may select a resource <NUM> in the first slot for UE-<NUM>'s communication. Here, UE-<NUM>'s communication extends into the second slot (e.g., Priority <NUM>).

As indicated above, UE-<NUM>'s communication is associated with a priority level of <NUM>. Therefore, the earliest slot in which UE-<NUM> is permitted to transmit is the second slot. UE-<NUM> may listen on one or more previous slots (e.g., the first slot and/or a slot associated with a previous priority contention window), may identify occupied resources of the second slot (e.g., the time/frequency resources used by UE-<NUM>'s communication), and may select a resource <NUM> other than the occupied resource. Here, UE-<NUM>'s communication extends to the sixth slot (e.g., Priority <NUM>).

As indicated above, UE-<NUM>'s communication is associated with a priority level of <NUM>. Therefore, the earliest slot in which UE-<NUM> is permitted to transmit is the fifth slot. UE-<NUM> may listen on one or more previous slots (e.g., the first slot through the fourth slot and/or a slot associated with a previous priority contention window), may identify occupied resources of the fifth slot (e.g., the time/frequency resources used by UE-<NUM>'s communication, since UE-<NUM>'s communication has ended), and may select a resource <NUM> other than the occupied resource. Here, UE-<NUM>'s communication extends to the seventh slot (e.g., Priority <NUM>).

As indicated above, UE-<NUM>'s communication is associated with a priority level of <NUM>. Therefore, the earliest slot in which UE-<NUM> is permitted to transmit is the sixth slot. However, UE-<NUM>'s communication, shown by the dashed rectangle in the last slot, occupies too many resources to be transmitted using a contiguous resource allocation in the sixth slot. For example, UE-<NUM> may determine that UE-<NUM>'s communication cannot be transmitted in the sixth slot based at least in part on listening to the first slot through the fifth slot and determining occupied resources associated with UE-<NUM>, UE-<NUM>, and UE-<NUM>. In this case, UE-<NUM> may determine to transmit on the seventh slot instead of the sixth slot (as shown by the dashed rectangle indicated by reference number <NUM>), although this may lead to a collision with a communication of priority level <NUM> (since a UE transmitting the communication of priority level <NUM> would not know that UE-<NUM>'s communication will be transmitted in the seventh frame by listening to the sixth frame). In some aspects, UE-<NUM> may drop UE-<NUM>'s communication or may postpone UE-<NUM>'s communication to a next priority contention window. For example, UE-<NUM> may postpone UE-<NUM>'s communication if postponing UE-<NUM>'s communication would not cause the violation of a latency requirement of UE-<NUM>'s communication.

Thus, a reliability-focused priority system may allocate slots and/or resources for communications of different priority levels, irrespective of the slot-level decentralized channel access mechanisms used for the communications.

<FIG> is a diagram illustrating an example process <NUM> performed, for example, by a wireless communication device, in accordance with various aspects of the present disclosure. Example process <NUM> is an example where a wireless communication device (e.g., UE <NUM>, BS <NUM>, and/or the like) performs prioritization for a decentralized channel access mechanism.

As shown in <FIG>, process <NUM> may include determining a window in which a communication is to be transmitted, wherein the communication is associated with a priority level (block <NUM>). For example, the wireless communication device (e.g., using controller/processor <NUM>, controller/processor <NUM> and/or the like) may determine a window (e.g., a priority contention window) in which a communication is to be transmitted (e.g., by the wireless communication device). The communication may be associated with a priority level. For example, the wireless communication device may determine the priority level (e.g., based at least in part on metadata of the communication, a header of the communication, a priority level of the wireless communication device, content of the communication, and/or the like).

As shown in <FIG>, process <NUM> includes determining an earliest slot, of the window, in which the wireless communication device is permitted to transmit the communication, wherein the earliest slot is determined based at least in part on the priority level (block <NUM>). For example, the wireless communication device (e.g., using controller/processor <NUM>, controller/processor <NUM>, and/or the like) may determine an earliest slot, of the window, in which the wireless communication device is permitted to transmit the communication. The earliest slot is determined based at least in part on the priority level.

As shown in <FIG>, process <NUM> includes mapping the communication to a resource based at least in part on the earliest slot and based at least in part on which resources, of the earliest slot, are occupied resources associated with another communication having a higher priority level than the communication (block <NUM>). For example, the wireless communication device (e.g., using controller/processor <NUM>, transmit processor <NUM>, TX MIMO processor <NUM>, MOD <NUM>, antenna <NUM>, and/or the like) may map the communication to a resource. The wireless communication device may map the communication to the resource based at least in part on the earliest slot (e.g., the communication may or may not be mapped to the earliest slot). The wireless communication device may map the communication based at least in part on which resource, of the earliest slot, are occupied resources associated with another communication having a higher priority level.

Claim 1:
A method (<NUM>) of wireless communication performed by a wireless communication device, comprising:
determining (<NUM>) an earliest slot, of a window in which a communication is to be transmitted, in which the wireless communication device is permitted to transmit the communication,
wherein the earliest slot is determined based at least in part on a priority level of the communication; and
characterized by mapping (<NUM>) the communication to a resource in the earliest slot or a slot after the earliest slot based at least in part on the earliest slot and based at least in part on which resources, of the earliest slot, are occupied resources associated with another communication having a higher priority level than the communication.