Handling Persistently Occupied Channels within Unlicensed Radio Spectrum

This document describes techniques and devices for identifying and handling persistently occupied channels within unlicensed radio spectrum. In particular, a user equipment (UE) determines whether or not a channel that is associated with a particular bandwidth part or a sub-band of the bandwidth part is persistently occupied. The UE employs techniques that decrease sensitivity to uplink transmission timing or short-term channel congestion and enables the UE to efficiently identify persistently occupied channels. For example, the UE can use a first timer and a first counter to determine whether or not the channel is persistently occupied. The UE can recover from a situation in which the channel is persistently occupied and report information to a base station regarding the persistently occupied channel. In this way, the UE can utilize the unlicensed radio spectrum and re-establish communications responsive to the presence of one or more persistently occupied channels.

BACKGROUND

Licensed radio spectrum is limited and monetarily costly. Some Fifth Generation New Radio (5G-NR) techniques offload cellular traffic from the licensed radio spectrum to unlicensed radio spectrum. To utilize the unlicensed radio spectrum, 5G-capable devices operate under regulations that require access techniques to fairly share the unlicensed radio spectrum with other users. In contrast to the more-tightly-managed access to resources of the licensed radio spectrum, operations under spectrum-sharing regulations for the unlicensed radio spectrum can create uncertainty about when particular resources will be available or become unavailable. Consequently, a 5G-capable device may not be able to transmit on a desired channel in a timely fashion if that channel is in use by another wireless transmitting device. Delays caused by these transmission rules can make it challenging to perform time-sensitive or periodic transmissions.

SUMMARY

This document describes techniques and devices for identifying and handling persistently occupied channels within unlicensed radio spectrum. In particular, a clear-channel-assessment module of a user equipment (UE) determines whether or not a channel that is associated with a particular bandwidth part or a sub-band of the bandwidth part is persistently occupied. The clear-channel-assessment module employs techniques that decrease the clear-channel-assessment module's sensitivity to uplink transmission timing or short-term channel congestion and enables the clear-channel-assessment module to efficiently identify persistently occupied channels. Additionally, the clear-channel-assessment module determines whether or not multiple channels that are associated with different bandwidth parts or different sub-bands of a particular bandwidth part are persistently occupied. The clear-channel-assessment module enables the UE to recover from this situation and report information to a base station regarding the persistently occupied channels. In this way, the UE can utilize the unlicensed radio spectrum and re-establish communications responsive to the presence of one or more persistently occupied channels.

Aspects described below include a method performed by a user equipment for identifying persistently occupied channels within unlicensed radio spectrum. The method includes executing a first clear-channel-assessment procedure for a first channel. The method also includes determining that the first channel is occupied based on the first clear-channel-assessment procedure. Responsive to determining that the first channel is occupied, the method includes starting a first timer and initializing a first counter. The method includes executing subsequent clear-channel-assessment procedures for the first channel. The method also includes incrementing, within a duration of the first timer, the first counter to count a first quantity of the subsequent clear-channel-assessment procedures that determine that the first channel is occupied. Responsive to the first counter being greater than a first threshold, the method includes determining that the first channel is persistently occupied. The method may further include operations to handle a persistently occupied channel, when such a channel has been identified.

Aspects described below also include a user equipment with a radio-frequency transceiver. The user equipment also includes a processor and memory system configured to perform any of the methods described.

Aspects described below additionally include a processor-readable medium having instructions stored thereon that, when executed by a processor, cause the processor to perform any of the methods described.

Aspects described below further include a system with means for handling persistently occupied channels within unlicensed radio spectrum.

DETAILED DESCRIPTION

Overview

Licensed radio spectrum is limited and monetarily costly. Some Fifth Generation New Radio (5G-NR) techniques offload cellular traffic from the licensed radio spectrum to unlicensed radio spectrum. To utilize the unlicensed radio spectrum, 5G-capable devices operate under regulations that require access techniques to fairly share the unlicensed radio spectrum with other users. In contrast to the more-tightly-managed access to resources of the licensed radio spectrum, operations under spectrum-sharing regulations for the unlicensed radio spectrum can create uncertainty about when particular resources will be available or become unavailable. Consequently, a 5G-capable device may not be able to transmit on a desired channel in a timely fashion if that channel is in use by another wireless transmitting device. Delays caused by these transmission rules can make it challenging to perform time-sensitive or periodic transmissions.

To address this challenge, techniques and devices for handling persistently occupied channels within unlicensed radio spectrum are described. In particular, a clear-channel-assessment module of a user equipment (UE) determines whether or not a channel that is associated with a particular bandwidth part or a sub-band of the bandwidth part is persistently occupied. The clear-channel-assessment module employs techniques that decrease the clear-channel-assessment module's sensitivity to uplink transmission timing or short-term channel congestion and enables the clear-channel-assessment module to efficiently identify persistently occupied channels. Additionally, the clear-channel-assessment module determines whether or not multiple channels that are associated with different bandwidth parts or different sub-bands of a particular bandwidth part are persistently occupied. The clear-channel-assessment module enables the UE to recover from this situation and report information to a base station regarding the persistently occupied channels. In this way, the UE can utilize the unlicensed radio spectrum and re-establish communications responsive to the presence of one or more persistently occupied channels.

Example Environment

FIG. 1illustrates an example environment100that includes multiple UEs110, illustrated as UE111, UE112, and UE113. Each UE110can communicate with base stations120(illustrated as base stations121and122) through one or more wireless communication links130(wireless link130), illustrated as wireless links131and132. For simplicity, the UE110is implemented as a smartphone but may be implemented as any suitable computing or electronic device, such as a mobile communication device, modem, cellular phone, gaming device, navigation device, media device, laptop computer, desktop computer, tablet computer, smart appliance, vehicle-based communication system, or an Internet-of-Things (IoT) device such as a sensor or an actuator. The base stations120(e.g., a Next Generation Node B, gNode B, gNB, ng-eNB, or the like) may be implemented in a macrocell, microcell, small cell, picocell, distributed base station, or the like, or any combination or future evolution thereof.

The base stations120communicate with the UE110using the wireless links131and132, which may be implemented as any suitable type of wireless link. The wireless links131and132include control and data communication, such as downlink of data and control information communicated from the base stations120to the UE110, uplink of other data and control information communicated from the UE110to the base stations120, or both. The wireless links130include one or more wireless links (e.g., radio links) or bearers implemented using any suitable communication protocol or standard, or combination of communication protocols or standards, such as 5thGeneration New Radio (5G NR). Multiple wireless links130can be aggregated using carrier aggregation or multi-connectivity to provide a higher data rate for the UE110. Multiple wireless links130from multiple base stations120can be configured for Coordinated Multipoint (CoMP) communication with the UE110.

The base stations120are collectively a Radio Access Network140(e.g., RAN, 5G NR RAN, or NR RAN). The base stations121and122in the RAN140are connected to a core network150. The base stations121and122connect, at102and104respectively, to the core network150through an NG2 interface for control-plane signaling and through an NG3 interface for user-plane data communications when connecting to a 5G core network. In addition to connections to the core network150, the base stations120can communicate with each other. For example, the base stations121and122communicate using an Xn Application Protocol (XnAP) through an Xn interface, at103, to exchange user-plane and control-plane data. The UE110connects, through the core network150, to public networks, such as the Internet160to interact with a remote service170.

The UEs110can also connect to the Internet160using a WLAN connection133to a WLAN access point180, which is connected to the Internet160. The WLAN access point180may be located in a user's home, an office, an airport, a coffee shop, and so forth. The WLAN access point180may be independently operated, such as in a user's home or office, may be part of an enterprise network, or may be operated as part of a public network of WLAN access points operated by a wireless network operator. The WLAN wireless network operator may be the same or different than the operator of the RAN140.

In the example environment100, two or more of the UEs110use the unlicensed radio spectrum. Sometimes a conflict occurs while, for instance, the UE111transmits a first uplink signal to the WLAN access point180using a first channel and the UE112attempts to transmit a second uplink signal to the base station121using the same first channel. Because the first channel is currently occupied by the UE111, however, the UE112is unable to transmit on the first channel without interfering with the UE111's transmission. Consequently, transmission of the second uplink signal is delayed.

If the conflict continues to occur due to the UE111or another UE110(e.g., the UE113) transmitting additional uplink signals using the first channel, the UE112may be prevented from performing time-sensitive or periodic procedures. This situation can occur, for instance, when a large quantity of UEs110use the unlicensed radio spectrum and are within close proximity to one another. In this case, the first channel is considered to be persistently occupied.

To handle this situation, the UE112determines that the first channel is persistently occupied and switches over to using a different channel within the unlicensed radio spectrum. If the UE112determines that one or more channels are persistently occupied, the UE112executes a recovery procedure to re-establish communication with the base station120and report information regarding the persistently occupied channels, as further described below with respect toFIG. 2.

Example Device

FIG. 2illustrates an example device diagram200of the UE110. The UE110can include additional functions and interfaces that are omitted fromFIG. 2for the sake of clarity. In the depicted configuration, the UE110includes antennas202, a radio-frequency (RF) front end204(RF front end204), a radio-frequency transceiver, including, for example, a 5G NR transceiver206for communicating with one or more base stations120in the RAN140. The RF front end204couples or connects the 5G NR transceiver206to the antennas202to facilitate various types of wireless communication. The antennas202can include an array of multiple antennas that are configured similar to or differently from each other. The antennas202and the RF front end204are tuned to one or more transmission frequency bands defined by the 5G NR communication standards and implemented by the 5G NR transceiver206. These transmission frequency bands include those within unlicensed radio spectrum.

The UE110also includes one or more processors208and memory system including, for example, computer-readable storage media210(CRM210). The processor208can be a single core processor or a multiple core processor composed of a variety of materials, such as silicon, polysilicon, high-K dielectric, copper, and so on. The CRM210excludes propagating signals and includes any suitable memory or storage device, such as random-access memory (RAM), static RAM (SRAM), dynamic RAM (DRAM), non-volatile RAM (NVRAM), read-only memory (ROM), or Flash memory useable to store device data212of the UE110. The device data212includes user data, multimedia data, beamforming codebooks, applications, and/or an operating system of the UE110, which are executable by the processor208to enable user-plane communication, control-plane signaling, and user interaction with the UE110.

The CRM210also includes a clear-channel-assessment (CCA) module214. Alternatively or additionally, the clear-channel-assessment module214can be implemented in whole or part as hardware logic or circuitry integrated with or separate from other components of the UE110. The clear-channel-assessment module214handles detection of and recovery from persistently occupied channels within unlicensed radio spectrum. In particular, the clear-channel-assessment module214determines whether or not one or more channels within the unlicensed radio spectrum are persistently occupied. If multiple channels are persistently occupied, the clear-channel-assessment module214further executes a recovery procedure that enables the UE110to establish communications with a base station120and report information regarding the persistently occupied channels.

To determine whether or not a channel is persistently occupied, the clear-channel-assessment module214executes a clear-channel-assessment procedure prior to transmitting an uplink signal. In some cases, the clear-channel-assessment procedure is performed as part of a listen-before-talk (LBT) procedure. During the clear-channel-assessment procedure, the clear-channel-assessment module214measures an amount of energy that is detected within the channel and compares the detected energy to a threshold. If the detected energy is less than or equal to the threshold, the clear-channel-assessment module214determines that the channel is unoccupied and transmits the uplink signal. Alternatively, if the detected energy is above the threshold, the clear-channel-assessment module214determines that another device is transmitting on the channel. In other words, the clear-channel-assessment module214determines that the channel is occupied. Consequently, the clear-channel-assessment module214postpones transmitting on the channel and transmission of the uplink signal is delayed.

In some cases, the clear-channel-assessment module214performs a back-off procedure and maintains a back-off or contention timer responsive to determining that the channel is occupied. For subsequent attempts to transmit, the clear-channel-assessment module214determines the channel to be occupied until an expiration of the back-off timer.

The CRM210additionally stores a persistently-occupied-channel array216, one or more timers220(e.g., a first timer221and a second timer222), one or more counters (e.g., a first counter231and a second counter232), one or more thresholds240(e.g., a first threshold241and a second threshold242), or combinations thereof. One or more of these entities are modified and used by the clear-channel-assessment module214to determine whether or not the channel is persistently occupied.

Generally speaking, the timer220specifies a duration for which the clear-channel-assessment module214determines whether or not the channel is persistently occupied. In some implementations, the clear-channel-assessment module214also determines that the channel is persistently occupied responsive to the timer220expiring. As an example, a duration of the timer220is based on a predetermined value that is stored in the CRM210. In another example, the UE110receives a message from a base station120that specifies the duration of the timer220. In either example, the duration of the timer220can be based on a first quantity of periodic or predefined uplink transmissions, such as those associated with a random-access (RA) procedure, a sounding reference signal (SRS) procedure, channel-quality-indicator (CQI) reporting, or channel-state-information (CSI) reporting. In other words, the duration of the timer220can be greater than or equal to a duration of the random-access procedure, the sounding reference signal procedure, the channel-quality-indicator reporting, or the channel-state-information reporting. In general, the duration of the timer220enables the clear-channel-assessment module214to evaluate at least a particular quantity of subsequent clear-channel-assessment procedures prior to determining that the channel is persistently occupied.

In various implementations, the clear-channel-assessment module214uses one or more counters230to count a quantity of clear-channel-assessment procedures that are performed during at least a portion of the duration of the timer220, a quantity of clear-channel-assessment procedures that determine that the channel is occupied, and/or a quantity of consecutive clear-channel-assessment procedures that determine that the channel is occupied. In some cases, the clear-channel-assessment module214compares the counter230to an associated threshold240to determine whether or not the channel is persistently occupied. In other cases, a comparison of the counter230to the threshold240triggers a procedure that determines whether or not the channel is persistently occupied. Similar to the duration of the timer220, a value of the threshold240can be stored in the CRM210or received from the base station120. Adjusting the value of the threshold240can increase or decrease a likelihood that the clear-channel-assessment module214determines that the channel is persistently occupied.

Responsive to determining that the channel is persistently occupied, the clear-channel-assessment module214can continually evaluate other channels to identify a channel that is not persistently occupied. If one or more channels are persistently occupied, the clear-channel-assessment module214can initiate a radio-link failure procedure or trigger the UE110to re-establish a connection with the base station120.

The clear-channel-assessment module214uses the persistently-occupied-channel array216to keep track of the types of channels that have been evaluated and whether or not the channel is persistently occupied. The persistently-occupied channel array216can include, for instance, an array of elements that are associated with different channels, respectively. As an example, the clear-channel-assessment module214sets a value of each one of the elements to indicate that the channel has not been evaluated, was evaluated and determined to be persistently occupied, or was evaluated and determined to not be persistently occupied. The clear-channel-assessment module214can, at least partially, handle the detection of and recovery from persistently occupied channels within the unlicensed radio spectrum, as described with respect toFIGS. 3-9.

Example Methods for Detecting a Persistently Occupied Channel

FIGS. 3-8depict example methods300-800for detecting a persistently occupied channel within the unlicensed radio spectrum. Methods300-800are shown as a set of operations (or acts) performed but not necessarily limited to the order or combinations in which the operations are illustrated. Further, any of one or more of the operations may be repeated, combined, reorganized, skipped, or linked to provide a wide array of additional and/or alternate methods. In portions of the following discussion, reference may be made to environment100ofFIG. 1and entities detailed inFIG. 2, reference to which is made for example only. The techniques are not limited to performance by one entity or multiple entities operating on one device.

FIG. 3illustrates an example method300for detecting a persistently occupied channel within the unlicensed radio spectrum using the first timer221. In the method300, the UE110relies on an expiration of the first timer221to determine whether or not a channel is persistently occupied. In particular, the UE110determines that the channel is persistently occupied if none of the clear-channel-assessment procedures performed during a duration of the first timer221determined that the channel was unoccupied. Responsive to one of the clear-channel-assessment procedures determining that the channel is unoccupied, the UE110stops or resets the first timer221. In this way, the UE110avoids determining that the channel is persistently occupied if the channel is unoccupied at least once during the duration of the first timer221. Relying on the first timer221instead of a counter enables the UE110to detect instances in which the channel becomes unoccupied, even for short durations, and postpone determining that the channel is persistently occupied. Hence, the clear-channel-assessment procedure is less sensitive to the timing of uplink transmissions by other users of the unlicensed spectrum, and is less sensitive to short-term channel congestion.

At302, the UE110executes a first clear-channel-assessment procedure. For example the UE110executes a first clear-channel-assessment procedure for a first channel within the unlicensed radio spectrum before attempting to transmit a first uplink signal.

At304, the UE determines that the channel is occupied. For example, the UE110determines that the first channel is occupied based on a comparison of the detected energy measured within the first channel to a threshold indicating that the detected energy is greater than the threshold, as described above with respect toFIG. 2.

At306, the UE starts a first timer. For example, the UE110starts the first timer221ofFIG. 2with a specified duration, as described above with respect toFIG. 2.

Optionally at308, the UE initiates a random-access procedure. For example, the UE110initiates the random-access procedure using the first channel. The random-access procedure provides the UE110an opportunity to execute additional clear-channel-assessment procedures for determining whether the first channel is persistently occupied. In this way, the random-access procedure increases reliability for assessing whether the first channel is persistently occupied by enabling the clear-channel-assessment module214to evaluate at least a minimum quantity of subsequent clear-channel-assessment procedures prior to determining that the channel is persistently occupied.

At310, the UE executes a subsequent clear-channel-assessment procedure. For example, the UE110executes a second clear-channel-assessment procedure prior to transmitting a second uplink signal. In some cases, the second uplink signal includes a random-access channel (RACH) signal associated with the random-access procedure initiated at308. In other cases, the second uplink signal includes another type of uplink signal, such as a sounding reference (SR) signal or a physical uplink control channel (PUCCH) signal.

At312, the UE determines whether or not the channel is occupied based on the subsequent clear-channel-assessment procedure at310. For example, the UE110determines whether or not the first channel is occupied (e.g., busy) based on the second clear-channel-assessment procedure performed at310. As another example, the UE110performs a back-off procedure and determines whether or not the first channel is occupied based on an expiration of a back-off or contention timer. If the UE110determines that the first channel is occupied, the operations proceed from312to314. Alternatively, if the UE110determines that the first channel is unoccupied, the operations proceed from312to316.

At316, the UE stops the first timer responsive to the UE determining that the channel is unoccupied at312. For example, the UE110stops the first timer221responsive to the UE110determining that the first channel is unoccupied based on the second clear-channel-assessment procedure. Additionally, the UE110determines that the first channel is not persistently occupied (e.g., the first channel is unoccupied) and updates the persistently-occupied-channel array216accordingly. The process can repeat at302for a next clear-channel-assessment procedure that evaluates the same channel (e.g., the first channel) or a different channel (e.g., a second channel) that uses a different bandwidth part or a different sub-band of a same bandwidth part.

At314, the UE determines whether or not the first timer expired. For example, the UE110determines whether or not the first timer221expired. If the UE110determines that the first timer221has not expired, the operations proceed from314to310and the UE110continues to execute additional clear-channel-assessment procedures (e.g., a third clear-channel assessment procedure). Alternatively, if the UE110determines that the first timer221expired, the operations proceed from314to318.

At318, the UE110determines that the channel is persistently occupied. For example, the UE110determines that the first channel is persistently occupied and updates the persistently-occupied-channel array216accordingly. The process can repeat at302for a next clear-channel-assessment procedure that evaluates a different channel.

FIG. 4illustrates an example method400for detecting a persistently occupied channel within the unlicensed radio spectrum using the first timer221, the first counter231, and the second counter232. In the method400, the UE110relies on the first counter231to count a total quantity of clear-channel-assessment procedures that determine that the channel is occupied within a duration of the first timer221. The UE110also relies on the second counter232to count a quantity of consecutive clear-channel-assessment procedures that determine that the channel is occupied within the duration of the first timer221. The UE110determines whether or not the channel is persistently occupied based on the first counter or the second counter232exceeding an associated threshold before the first timer221expires. This enables the UE110to appropriately categorize the channel as persistently occupied even if there is an occasional instance in which the channel is unoccupied. Hence, the clear-channel-assessment procedure is less sensitive to the timing of uplink transmissions by other users of the unlicensed spectrum, and is less sensitive to short-term channel congestion.

At402and404, the UE performs similar operations as described above with respect toFIG. 3at302and304, respectively. Although not shown, the UE110can additionally initiate the random-access procedure, as described above inFIG. 3at308.

At406, the UE starts a first timer and sets (e.g., initializes) both a first counter and a second counter. For example, the UE110starts the first timer221with a specified duration, as described above with respect toFIG. 2. The UE110also sets both the first counter231and the second counter232equal to a predetermined value, such as zero.

At408, the UE executes a subsequent clear-channel-assessment procedure, as described above with respect toFIG. 3at310.

At410, the UE determines whether or not the channel is occupied based on the subsequent clear-channel-assessment procedure at408, as described above with respect toFIG. 3at312. If the UE110determines that the channel is occupied, the operations proceed from410to412. Alternatively, if the UE110determines that the channel is unoccupied, the operations proceed from410to414.

At414, the UE resets the second counter. For example, the UE110resets the second counter232equal to zero. The process proceeds to424.

At412, the UE determines whether or not the channel was previously occupied based on a previous clear-channel-assessment procedure. For example, the UE110determines whether or not the first channel was previously occupied based on a previous clear-channel-assessment procedure. The UE110makes this determination based on, for instance, a value of the second counter232. If the value of the second counter232is greater than zero, then the channel was previously determined to be occupied. In contrast, the channel was previously determined to be unoccupied if the value of the second counter232is equal to zero. Responsive to the UE110determining that the channel was previously occupied, the operations proceed from412to416. Otherwise, the operations proceed from412to418.

At416, the UE increments both the first counter and the second counter. For example, the UE110increments both the first counter231and the second counter232by one.

At418, the UE increments the first counter. For example, the UE110increments the first counter231by one. In this case, a value of the second counter232remains unchanged.

At420, the UE compares the first counter to a first threshold and compares the second counter to a second threshold. For example, the UE110compares the first counter231to the first threshold241and compares the second counter232to the second threshold242. If the first counter231is greater than the first threshold241or the second counter232is greater than the second threshold242, the operations proceed from420to422. Otherwise, the operations proceed from420to424.

At422, the UE determines that the channel is persistently occupied, as described above with respect toFIG. 3at318. The process can repeat at402for a next clear-channel-assessment procedure that evaluates a different channel (e.g., the second channel).

At424, the UE determines whether or not the first timer expired. For example, the UE110determines whether or not the first timer221expired. If the first timer221has not expired, the operations proceed from424to408. If the first timer221expired, the UE110determines that the first channel is not persistently occupied (e.g., the first channel is unoccupied) and updates the persistently-occupied-channel array216accordingly. The process can repeat at402for a next clear-channel-assessment procedure that evaluates the same channel or a different channel.

FIG. 5illustrates an example method500for initiating a random-access procedure for detecting a persistently occupied channel within unlicensed radio spectrum using the first timer221and the first counter231. In the method500, the UE110determines that the channel is occupied for a particular duration of time prior to initiating a procedure to determine whether or not the channel is persistently occupied. In this way, the UE110avoids incorrectly identifying the channel as persistently occupied for short durations during which the channel is occupied. Hence, the clear-channel-assessment procedure is less sensitive to the timing of uplink transmissions by other users of the unlicensed spectrum, and is less sensitive to short-term channel congestion.

In this example, the UE110uses the first counter231to count a consecutive quantity of clear-channel assessment procedures that determine that the channel is occupied. If the first counter231exceeds the first threshold241, the UE110initiates a random-access procedure.

At502and504, the UE performs similar operations as described above with respect toFIG. 3at302and304, respectively.

At506, the UE starts a first timer and sets a first counter. For example, the UE110starts the first timer221with a specified duration, as described above with respect toFIG. 2. The UE110also sets the first counter231equal to a predetermined value, such as zero. The first counter231counts a quantity of clear-channel-assessment procedures that determine that the first channel is occupied.

At508, the UE executes a subsequent clear-channel-assessment procedure, as described above with respect toFIG. 3at310.

At510, the UE determines whether or not the first timer expired. For example, the UE110determines whether or not the first timer221expired. If the first timer221has not expired, the operations proceed from510to512. If the first timer221expired, the operations proceed from510to502. The process can repeat at502for a next clear-channel-assessment procedure that evaluates the same channel (e.g., the first channel) or a different channel (e.g., the second channel).

At512, the UE determines whether or not the channel is occupied based on the subsequent clear-channel-assessment procedure, as described above with respect toFIG. 3at312. If the UE110determines that the first channel is occupied, the operations proceed from512to514. Alternatively, if the UE110determines that the channel is unoccupied, the operations proceed from512to516.

At516, the UE stops the first timer. For example, the UE110stops the first timer221. Additionally, the UE110determines that the first channel is not persistently occupied (e.g., the first channel is unoccupied) and updates the persistently-occupied-channel array216accordingly. The process can repeat at502for a next clear-channel-assessment procedure that evaluates the same channel (e.g., the first channel) or a different channel (e.g., a second channel).

At514, the UE increments the first counter. For example, the UE110increments the first counter231by one. Due to the stopping of the first timer221at516and the transition from516to502responsive to the UE110determining the channel is unoccupied, the first counter231maintains a count of a quantity of consecutive clear-channel-assessment procedures that determine that the channel is occupied.

At518, the UE compares the first counter to a first threshold. For example, the UE110compares the first counter231to the first threshold241. If the first counter231is greater than the first threshold241, the operations proceed from518to520to initiation a procedure that determines whether or not the first channel is persistently occupied. Otherwise, the operations proceed from518to508.

At520, the UE initiates a random-access procedure, as described above with respect toFIG. 3at308. The random-access procedure provides the UE110opportunities to execute additional clear-channel-assessment procedures for determining whether the first channel is persistently occupied. During520, the base station120broadcasts a random-access preamble to the UE110using a system information message. The UE110uses the preamble to perform the random-access procedure.

The UE110can perform the random-access procedure with a primary cell (PCell) or a secondary cell (SCell). As an example, the UE110performs the two-step random-access procedure or the four-step random-access procedure with the PCell if the channel is associated with a special cell (SpCell) (e.g., the PCell of a master cell group (MCG) or a primary SCell of a secondary cell group (SCG)).

In another example, the UE110performs the two-step random-access procedure with the SCell if the channel is associated with the SCell. The SCell configures and broadcasts a preamble index for the UE110to perform the two-step random-access procedure. In some cases, the SCell configures the physical-random-access channel (PRACH) for the UE110to transmit the preamble for the random-access procedure. The operations proceed from520to either602ofFIG. 6 or 702ofFIG. 7, which are further described below.

FIG. 6illustrates an example method600for detecting a persistently occupied channel within the unlicensed radio spectrum using a random-access procedure, the first timer221, and the first counter231. This method describes additional operations that are performed responsive to the initialization of the random-access procedure at520ofFIG. 5.

At602, the UE sets a first counter. For example, the UE110sets the first counter231equal to a predetermined value, such as zero. Although shown as occurring after520, the operation at602can alternatively occur before or as part of the operation at520.

At602, the UE executes a subsequent clear-channel-assessment procedure, as described above with respect toFIG. 3at310.

At604, the UE determines whether or not the channel is occupied. If the channel is occupied, the operations proceed from604to606. Otherwise, the operations proceed from604to608.

At608, the UE stops the first timer221. For example, the UE110stops the first timer221. Additionally or alternatively, the UE110resets the first counter231. The UE110also determines that the first channel is not persistently occupied (e.g., the first channel is unoccupied) and updates the persistently-occupied-channel array216accordingly. The process can repeat at502for the same channel or a different channel.

At606, the UE increments the first counter responsive to determining that the channel is occupied at604. For example, the UE increments the first counter231by one. Due to the stopping of the first timer221at608and the transition from608to502responsive to the UE110determining the channel is unoccupied, the first counter231maintains a count of a quantity of consecutive clear-channel-assessment procedures that determine that the channel. This count includes the subsequent clear-channel-assessment procedures508performed at508and evaluated at512prior to the initiation of the random-access procedure at520.

At610, the UE determines whether or not the first timer expired. For example, the UE110determines whether or not the first timer221expired. If the first timer221has not expired, the operations proceed from610to602. Alternatively, if the first timer221expired, the operations proceed from610to612.

At612, the UE compares the first counter to a first threshold. For example, the UE110compares the first counter231to the first threshold241. The first threshold241at612can be similar to or different from the first threshold241at518. If the first counter231is greater than the first threshold241, the operations proceed from612to614. Otherwise, the UE110determines that the first channel is not persistently occupied (e.g., the first channel is unoccupied) and updates the persistently-occupied-channel array216accordingly. The process can then repeat at502for the same channel or a different channel.

At614, the UE determines that the channel is persistently occupied, as described above with respect toFIG. 3at318. The process can repeat at502for a next clear-channel-assessment procedure that evaluates a different channel.

FIG. 7illustrates an example method700for detecting a persistently occupied channel using a random-access procedure, the first timer221, and a second timer222. This method describes additional operations that are performed responsive to the initialization of the random-access procedure at520ofFIG. 5. Instead of maintaining and comparing the first counter231to the first threshold241, as described above with respect toFIG. 6, the method ofFIG. 7detects an expiration of the second timer222to determine that the channel is persistently occupied. Similar to the first counter231inFIG. 6, the second timer222enables the UE110to recognize that consecutive clear-channel-assessment procedures determine that the channel is occupied.

At702, the UE starts a second timer. For example, the UE110starts the second timer222with a specified duration, as described above with respect toFIG. 2. A duration of the second timer222can be similar to or different from the duration of the first timer221.

At704, the UE executes a subsequent clear-channel-assessment procedure, as described above with respect toFIG. 3at310.

At706, the UE determines whether or not the second timer expired. For example, the UE110determine whether or not the second timer222expired. If the second timer222expired, the operations proceed from706to710. Otherwise, the operations proceed from706to708.

At710, the UE determines that the channel is persistently occupied, as described above with respectFIG. 3at318. The process can repeat at502for a next clear-channel-assessment procedure that evaluates a different channel.

At708, the UE determines whether or not the channel is occupied responsive to the second timer not expiring. If the channel is occupied, the operations proceed from708to704. Otherwise, the operations proceed from708to712.

At712, the UE stops the second timer. For example, the UE110stops the second timer222, and the operations proceed from712to502. The UE110additionally determines that the first channel is not persistently occupied (e.g., the first channel is unoccupied) and updates the persistently-occupied-channel array216responsive to stopping the second timer222at712.

In another implementation not shown, the operations described above at702,706, and712can apply to the first timer221instead of the second timer222. In this way, the first timer221can be re-used for determining whether or not the first channel is persistently occupied.

FIG. 8illustrates another example method800for detecting a persistently occupied channel within the unlicensed radio spectrum using a window-based detection scheme. In this example, the UE110uses the first counter231, the second counter232, the first threshold241, and the second threshold242. The first counter231represents a total quantity of clear-channel-assessment procedures performed within the past M subframes, where M is a positive integer. The second counter232represents a total quantity of clear-channel-assessment procedures that determine that the channel is occupied within the past M subframes. In some implementations, the first counter231and the second counter232include an array of values that are specific to each channel so that the counters231and232can be appropriately updated if the UE110switches between different types of channels.

The UE110determines whether or not the channel is persistently occupied based on a ratio of the second counter232and the first counter231exceeding the first threshold241, and based on the first counter231exceeding the second threshold242. In this way, the UE110uses recent information (e.g., information from the last M subframes) to make this determination and considers both the quantity of clear-channel-assessment procedures performed and the percentage of time the channel was occupied within a moving window of time.

At802, the UE executes a clear-channel-assessment procedure and updates a first counter based on the past M subframes. For example, the UE110executes a first clear-channel-assessment procedure and updates the first counter231based on the past M subframes. Although not shown, the UE110can additionally initiate the random-access procedure, as described above inFIG. 3at308.

At804, the UE determines whether or not the channel is occupied, as described above with respect toFIG. 3at304. If the channel is occupied, the operations proceed from804to806. Otherwise, the operations proceed from804to802.

At806, the UE updates a second counter based on the past M subframes. For example, the UE110updates the second counter232based on the past M subframes. In a particular instance, the UE110increments the second counter232to account for the channel being occupied at804and to account for the channel not being occupied during the past M+1 subframe. In another instance, the UE110does not change the second counter232to account for the channel being occupied at804and to account for the channel being occupied during the past M+1 subframe. In this case, the second counter232remains the same.

At808, the UE compares a ratio of the second counter and the first counter to a first threshold and compares the first counter to a second threshold. For example, the UE110compares the ratio of the second counter232and the first counter231to the first threshold241. The UE110also compares the first counter231to the second threshold242. If the ratio is greater than the first threshold241and the first counter231is greater than the second threshold242, the operations proceed from808to810. Otherwise, the operations proceed from808to802and the UE110determines that the first channel is not persistently occupied (e.g., the first channel is unoccupied) and updates the persistently-occupied-channel array216accordingly.

At810, the UE determines that the channel is persistently occupied, as described above with respect toFIG. 3at318. The process can repeat at802for a next clear-channel-assessment procedure that evaluates a different channel.

Example Methods for Recovering from Multiple Persistently Occupied Channels

As described above, the methods of300-800can repeat such that the UE110determines whether or not channels that are associated with different bandwidth parts or different sub-bands within a particular bandwidth part are persistently occupied.

FIG. 9depicts an example method900for recovering from multiple persistently occupied channels. Method900is shown as a set of operations (or acts) performed but not necessarily limited to the order or combinations in which the operations are illustrated. Further, any of one or more of the operations may be repeated, combined, reorganized, skipped, or linked to provide a wide array of additional and/or alternate methods. In portions of the following discussion, reference may be made to environment100ofFIG. 1and entities detailed inFIG. 2, reference to which is made for example only. The techniques are not limited to performance by one entity or multiple entities operating on one device.

At902, the UE determines that multiple channels associated with different transmission frequency bands are persistently occupied. For example, the UE110determines that a first channel associated with a first transmission frequency band and a second channel associated with a second transmission frequency band are both persistently occupied. The first transmission frequency band and the second transmission frequency band can be associated with different bandwidth parts, different sub-bands of a same bandwidth part, different sub-bands associated with different bandwidth parts, or a combination thereof.

Alternatively, at904, the UE uses a set of sub-bands associated with a particular bandwidth part and determines that the multiple channels associated with each sub-band within the set of sub-bands are persistently occupied. For example, the UE110determines that a first channel associated with a first sub-band of a bandwidth part and a second channel associated with a second sub-band of the bandwidth part are both persistently occupied. In some cases, this can occur responsive to all channels associated with each of the sub-bands within the bandwidth part determined to be persistently occupied.

Alternatively, at906, the UE uses a set of bandwidth parts and determines that the multiple channels associated with each bandwidth part within the set of bandwidth parts are persistently occupied. For example, the UE110determines that a first channel associated with a first bandwidth part and a second channel associated with a second bandwidth part are both persistently occupied.

At908, the UE initiates a radio-link failure procedure based on the occurrence of902,904, or906. For example, the UE110initiates the radio-link failure procedure responsive to either the operations at902occurring for a configured bandwidth part of a PCell, the operations at904occurring for the PCell, or the operations at906occurring for a MCG. The radio-link failure procedure causes the UE110to attempt to re-establish communication with the base station120.

Additionally or alternatively, the UE generates a report at910. For example, the UE110generates the report, which can include information regarding any of the parameters used to determine that the multiple channels are persistently occupied (e.g., values of respective first timers221, respective second timers222, respective first counters231, respective second counters232, respective first thresholds241, and/or respective second thresholds242), the types of uplink transmissions (e.g., SR, PUCCH, or RACH) that occurred, the types of clear-channel-assessment procedures (e.g., a type1 listen-before talk or a type 2 listen-before talk), the type of channel access priority class (CAPC), and so forth.

Consider an example in which the UE110uses carrier aggregation. Responsive to902or904occurring for a SCell, the UE either sends the report to the SCell using a different bandwidth part that is not persistently occupied (e.g., based on the persistently-occupied-channel array216) or sends the report to the PCell. Responsive to receiving the report, the PCell releases the SCell.

Consider another example in which the UE110is configured with multi-node connectivity (e.g., dual connectivity). Responsive to902,904, or906occurring for the PCell in the SCG (e.g., the PsCell), the UE110sends the report to the PCell. In this case, the report represents an extended SCG failure report. The report can additionally include information associated with the availability of other SCells within the SCG. Responsive to receiving the report, the PCell releases the secondary cell group (SCG) or configures a different SCG. In the examples described above, the PCell and the SCell can use the licensed radio spectrum, the unlicensed radio spectrum, or a combination thereof.

Example Method for Handling a Persistently Occupied Channel

FIG. 10depicts an example method1000for handling a persistently occupied channel. Method1000is shown as a set of operations (or acts) performed but not necessarily limited to the order or combinations in which the operations are illustrated. Further, any of one or more of the operations may be repeated, combined, reorganized, skipped, or linked to provide a wide array of additional and/or alternate methods. In portions of the following discussion, reference may be made to environment100ofFIG. 1and entities detailed inFIG. 2, reference to which is made for example only. The techniques are not limited to performance by one entity or multiple entities operating on one device.

At1002, a wireless transmitting device executes a first clear-channel-assessment procedure for a first channel. For example, the user equipment110executes the first clear-channel-assessment procedure, as shown at302inFIG. 3, at402inFIG. 4, or at502inFIG. 5. The first channel is associated with the unlicensed radio spectrum.

At1004, the wireless transmitting device determines that the first channel is occupied based on the first clear-channel-assessment procedure. For example, the UE110determines that the first channel is occupied based on the first clear-channel-assessment procedure, as shown at304inFIG. 3, at404inFIG. 4, or at504inFIG. 5.

At1006, the wireless transmitting device starts a first timer and initializes a first counter responsive to determining that the first channel is occupied. For example, the UE110starts a timer220(e.g., the first timer221ofFIG. 2) and initializes a counter230(e.g., the first counter231or the second counter232ofFIG. 2) responsive to determining that the first channel is occupied at1004. For example, the UE110can start the first timer221responsive to determining that the first channel is occupied, as shown at306inFIG. 3, at406inFIG. 4, or at506inFIG. 5. Additionally, the UE110can initialize the first counter231and/or the second counter232responsive to determining that the first channel is occupied, as shown at406inFIG. 4, or at506inFIG. 5.

The timer220can specify a duration for which the UE110determines whether or not the first channel is persistently occupied. In some implementations, an expiration of the timer220can indicate that the channel is persistently occupied, as shown at318inFIG. 3and at424inFIG. 4. In some cases, a duration of the timer220is associated with a duration of at least one of the following operations: a random-access procedure, a sounding reference signal procedure, channel-quality-indicator reporting, or channel-state-information reporting.

The counter230can count a total quantity or a consecutive quantity of clear-channel-assessment procedures that determine that the first channel is occupied. In some cases, the UE110uses the counter230to determine whether or not the first channel is persistently occupied.

At1008, the wireless transmitting device executes subsequent clear-channel-assessment procedures for the first channel. For example, the UE110executes subsequent clear-channel-assessment procedures for the first channel, as shown at310inFIG. 3, at408inFIG. 4, at508inFIG. 5, at602inFIG. 6, at704inFIG. 7, and at802inFIG. 8. In some situations, these subsequent clear-channel-assessment procedures occur after a random-access procedure is initiated, as shown at308inFIG. 3and at520inFIG. 5.

At1010, the wireless transmitting device increments the first counter within a duration of the first timer to count a first quantity of the subsequent clear-channel-assessment procedures that determine that the first channel is occupied. For example, the UE110increments, within a duration of the timer220, the counter230to count a quantity of the subsequent clear-channel-assessment procedures that determine that the first channel is occupied. In an example implementation, the UE110increments the first counter231while the first timer221is active (e.g., has not expired) to count the total quantity of the subsequent clear-channel-assessment procedures that determine that the first channel is occupied, as shown at418inFIG. 4and at514inFIG. 5. In another example implementation, the UE110increments the first counter231while the first timer221is active to count a quantity of consecutive subsequent clear-channel-assessment procedures that determine that the first channel is occupied, as shown at606inFIG. 6.

At1012, the wireless transmitting device determines the first channel to be persistently occupied responsive to the first counter being greater than a first threshold. For example, the UE110determines that the first channel is persistently occupied responsive to the counter230being greater than a threshold240(e.g., the first threshold241or the second threshold242ofFIG. 2). In an example implementation, the first counter231is compared to the first threshold241at420inFIG. 4and at612inFIG. 6. If the first counter231is greater than the first threshold241, the UE110determines the first channel is occupied, as shown at422inFIG. 4and at614inFIG. 6.

Alternatively, the UE110can initiate a procedure that determines whether or not the first channel is persistently occupied responsive to the first counter231being greater than the first threshold221. As an example, the UE110can perform the operations starting at520inFIG. 5. InFIG. 6, these operations further rely on the first timer221and the first counter231to determine whether or not the first channel is persistently occupied. InFIG. 7, these operations rely on the second timer222to determine whether or not the first channels is persistently occupied.

Although the method1000is described with respect to a first channel, these operations can be repeated for evaluating other channels within the unlicensed radio spectrum. If the UE110determines that multiple channels are persistently occupied, the UE110can recover from the situation by initiating a radio-link failure procedure908, as shown inFIG. 9. In general, any combination of the operations described in the methods300-1000can be integrated together or executed in parallel to enable the UE110to handle persistently occupied channels within the unlicensed radio spectrum.

CONCLUSION

Although techniques for handling persistently occupied channels within unlicensed radio spectrum have been described in language specific to features and/or methods, it is to be understood that the subject of the appended claims is not necessarily limited to the specific features or methods described. Rather, the specific features and methods are disclosed as example implementations of handling persistently occupied channels within unlicensed radio spectrum.

Some examples are described below.

A method for a user equipment comprising:

executing a first clear-channel-assessment procedure for a first channel;

determining that the first channel is occupied based on the first clear-channel-assessment procedure;

starting a first timer and initializing a first counter responsive to determining that the first channel is occupied;

executing subsequent clear-channel-assessment procedures for the first channel;

incrementing, within a duration of the first timer, the first counter to count a first quantity of the subsequent clear-channel-assessment procedures that determine that the first channel is occupied; and

determining that the first channel is persistently occupied responsive to the first counter being greater than a first threshold.

The method of example 1, wherein the first channel is within unlicensed radio spectrum.

The method of example 1 or 2, further comprising: determining that the first channel is persistently occupied responsive to the first timer expiring.

The method of any preceding example, further comprising:

determining that the first channel is unoccupied according to one of the subsequent clear-channel-assessment procedures; and

responsive to determining that the first channel is unoccupied, stopping the first timer and determining that the first channel is not persistently occupied.

The method of any preceding example, further comprising: initiating a radio-link failure procedure responsive to determining that the first channel is persistently occupied.

The method of example 5, further comprising:

determining that a second channel is persistently occupied; and

initiating the radio-link failure procedure responsive to determining that both the first channel and the second channel are persistently occupied.

The method of example 6, wherein the first channel and the second channel are associated with:

different bandwidth parts; or

different sub-bands of a same bandwidth part.

The method of any of examples 5-7, further comprising:

responsive to initiating the radio-link failure procedure, generating a report comprising at least one of the following:

a value of the first counter;

a value of the first threshold; or

a value of the first timer.

The method of any preceding example, further comprising:

initializing a second counter responsive to determining that the first channel is occupied based on the first clear-channel-assessment procedure;

incrementing, within the duration of the first timer, the second counter to count a second quantity of subsequent clear-channel assessment procedures that consecutively determine that the first channel is occupied; and

determining that the first channel is persistently occupied responsive to the second counter being greater than a second threshold.

The method of example 9, further comprising:

determining that the first channel is not persistently occupied responsive to the first timer expiring, the first counter being less than the first threshold, and the second counter being less than the second threshold.

The method of any preceding example, wherein a duration of the first timer is associated with a duration of at least one of the following operations:

a sounding reference signal procedure;

The method of any preceding example, further comprising:

initiating a random-access procedure responsive to the first counter being greater than the first threshold.

The method of any preceding example, further comprising:

updating a third counter to represent a total quantity of the subsequent clear-channel-assessment procedures executed within a particular quantity of subframes;

comparing a ratio of the first counter and the third counter to a third threshold; and

determining that the first channel is persistently occupied responsive to the ratio being greater than the third threshold and the first counter being greater than the first threshold.

The method of any preceding example, further comprising:

maintaining a persistently-occupied-channel array comprising elements associated with different channels, wherein:

the different channels include the first channel; and

a value of each element within the persistently-occupied-channel array indicates whether or not a corresponding channel of the different channels is persistently occupied or unoccupied.

A user equipment comprising:

a radio-frequency transceiver; and

a processor and memory system configured to perform the method of any of examples 1-14.

The user equipment of example 15, wherein the user equipment is configured to:

initiate a radio-link failure procedure responsive to determining that a channel is persistently occupied.

A processor-readable medium having instructions stored thereon that, when executed by a processor, cause the processor to perform the method of any of examples 1-11.

The processor-readable medium of example 17, wherein the instructions, when executed by the processor, cause the processor to:

initiate a radio-link failure procedure responsive to determining that a channel is persistently occupied.