Random access channel transmissions for frame based equipment systems

Methods, systems, and devices for wireless communications are described. The method may include receiving, from a base station over an unlicensed radio frequency spectrum band, a broadcast message including system information, the system information indicating a LBT mode of the base station and a set of random access channel resources associated with a fixed frame period, monitoring a wireless channel of the unlicensed radio frequency spectrum band during the fixed frame period for control information from the base station based on the indicated LBT mode, determining, based on the monitoring, that the base station has access to the wireless channel during the fixed frame period, and performing, based on the determining, a random access channel transmission during the fixed frame period using the set of random access channel resources.

CROSS REFERENCE

The present application for patent claims the benefit of Indian Provisional Patent Application No. 2019/41028336 by SUN et al., entitled “RANDOM ACCESS CHANNEL TRANSMISSIONS FOR FRAME BASED EQUIPMENT SYSTEMS,” filed Jul. 15, 2019, assigned to the assignee hereof, and expressly incorporated by reference herein.

BACKGROUND

The following relates generally to wireless communications, specifically to random access channel transmissions for frame based equipment systems, and more specifically to random access channel transmission using resources associated with a fixed frame period.

In some wireless communications systems, a UE may use random access channel procedures to establish a connection with a base station

SUMMARY

The described techniques relate to improved methods, systems, devices, and apparatuses that support random access channel transmissions for frame based equipment systems. Generally, the described techniques provide for a UE in a mobile wireless network monitoring broadcast signaling (e.g., broadcast messages) from a base station. In some cases, the UE may receive an indication in broadcast signaling for a frame that indicates to the UE an operating mode of the base station. For example, the indication may indicate whether the base station is operating in a frame base equipment (FBE) mode or load base equipment (LBE) mode. In some cases, the UE may select a channel access procedure for transmissions related to a random access channel procedure based on the determined operating mode of the base station. A channel access procedure is a procedure based on sensing that evaluates the availability of a channel for performing transmissions, for example, random access channel transmissions.

A method of wireless communications by a first UE is described. The method may include receiving, from a base station over an unlicensed radio frequency spectrum band, a broadcast message including system information, the system information indicating a listen before talk (LBT) mode of the base station and a set of random access channel resources associated with a fixed frame period, monitoring a wireless channel of the unlicensed radio frequency spectrum band during the fixed frame period for control information from the base station based on the indicated LBT mode, determining, based on the monitoring, that the base station has access to the wireless channel during the fixed frame period, and performing, based on the determining, a random access channel transmission during the fixed frame period using the set of random access channel resources.

An apparatus for wireless communications by a first UE is described. The apparatus may include a processor, memory coupled with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to receive, from a base station over an unlicensed radio frequency spectrum band, a broadcast message including system information, the system information indicating a LBT mode of the base station and a set of random access channel resources associated with a fixed frame period, monitor a wireless channel of the unlicensed radio frequency spectrum band during the fixed frame period for control information from the base station based on the indicated LBT mode, determine, based on the monitoring, that the base station has access to the wireless channel during the fixed frame period, and perform, based on the determining, a random access channel transmission during the fixed frame period using the set of random access channel resources.

Another apparatus for wireless communications by a first UE is described. The apparatus may include means for receiving, from a base station over an unlicensed radio frequency spectrum band, a broadcast message including system information, the system information indicating a LBT mode of the base station and a set of random access channel resources associated with a fixed frame period, monitoring a wireless channel of the unlicensed radio frequency spectrum band during the fixed frame period for control information from the base station based on the indicated LBT mode, determining, based on the monitoring, that the base station has access to the wireless channel during the fixed frame period, and performing, based on the determining, a random access channel transmission during the fixed frame period using the set of random access channel resources.

A non-transitory computer-readable medium storing code for wireless communications by a first UE is described. The code may include instructions executable by a processor to receive, from a base station over an unlicensed radio frequency spectrum band, a broadcast message including system information, the system information indicating a LBT mode of the base station and a set of random access channel resources associated with a fixed frame period, monitor a wireless channel of the unlicensed radio frequency spectrum band during the fixed frame period for control information from the base station based on the indicated LBT mode, determine, based on the monitoring, that the base station has access to the wireless channel during the fixed frame period, and perform, based on the determining, a random access channel transmission during the fixed frame period using the set of random access channel resources.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving, based on the monitoring, a synchronization signal block transmission, where determining that the base station may have access to the wireless channel may be based on the synchronization signal block transmission.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining a signal strength of the synchronization signal block transmission, where performing the random access channel transmission may be based on the determined signal strength of the synchronization signal block transmission satisfying a threshold.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving, based on the monitoring, additional system information during the fixed frame period, where performing the random access channel transmission may be based on the additional system information.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving a downlink grant based on a system information radio network temporary identifier associated with the additional system information, where performing the random access channel transmission may be based on the downlink grant.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining whether a frame of the fixed frame period includes a paging message or a downlink control information including a paging radio network temporary identifier, where performing the random access channel transmission may be based on whether the frame includes the paging message or the downlink control information.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for identifying a paging window based on one or more of: an identifier of the UE or an identifier of the base station, where receiving the paging message or the downlink control information may be based on the paging window.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving, based on the monitoring, one or more of: a random access response or a downlink control information including a random access radio network temporary identifier, where determining that the base station may have access to the wireless channel may be based on the random access response or the downlink control information.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the random access response or the downlink control information may be directed to a recipient other than the UE.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining whether a frame of the fixed frame period includes a physical downlink control channel with a placeholder radio network temporary identifier, where performing the random access channel transmission may be based on whether the frame includes the physical downlink control channel with the placeholder radio network temporary identifier.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the monitoring further may include operations, features, means, or instructions for detecting the physical downlink control channel with the placeholder radio network temporary identifier in a search space of a frame of the fixed frame period, where the search space of the frame includes one or more of: a system information search space or a paging search space.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining whether the fixed frame period includes a demodulation reference signal, where performing the random access channel transmission may be based on whether the frame includes the demodulation reference signal.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining a signal strength of the demodulation reference signal, where performing the random access channel transmission may be based on the determined signal strength of the demodulation reference signal satisfying a threshold.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining a validity of resources associated with the random access channel transmission based on a duration associated with a frame of the fixed frame period.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for performing the random access channel transmission after the UE processes the broadcast message, where the broadcast message may be transmitted in a first slot, and where the UE processes the broadcast message in one or more slots subsequent to the first slot.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for selecting, via a media access control layer of the UE, resources available in a frame of the fixed frame period for the random access channel transmission, and indicating, via the media access control layer, the selected resources to a physical layer of the UE, where the UE detects the broadcast message via the physical layer.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining, via the physical layer, a validity of the selected resources, where performing the random access channel transmission may be based on the determined validity of the selected resources.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for indicating an LBT failure to the media access control layer when the selected resources are determined to be invalid.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining, based on the broadcast message and the fixed frame period or a frame of the fixed frame period, a validity of the random access channel resources, where performing the random access channel procedure may be based on the validity of the random access channel resources.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for sending an indication of the validity of the random access channel resources from a physical layer of the UE to a media access control layer of the UE.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for entering a low-power state or sleep state based on determining a frame of the fixed frame period does not include at least one broadcast signal, where the UE may treat resources available in the frame for the random access channel transmission as invalid based on determining the frame does not include the at least one broadcast message.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the system information includes a configuration to monitor a group common physical downlink control channel, and where determining the base station may be operating in the LBT mode may be based on the configuration to monitor the group common physical downlink control channel.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the system information includes a configuration to use a category-2 LBT for the random access channel transmission, where determining the base station may be operating in the LBT mode may be based on the configuration to use the category-2 LBT for the random access channel transmission.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the system information includes an indication that the base station may be operating in the LBT mode.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving an authentication management message associated with a registration procedure, where determining the base station may be operating in the LBT mode may be based at least in part the authentication management message.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the LBT mode includes a frame based equipment (FBE) LBT mode, and the system information includes a first list of cells operating in the FBE mode and a second list of cells operating in a load based equipment (LBE) mode.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for applying a cell reselection priority to camp either on the cells operating in FBE mode or on the cells operating in the LBE mode.

DETAILED DESCRIPTION

The present techniques relate to random access channel transmissions for frame based equipment (FBE) systems, more specifically to random access channel transmissions using resources associated with a fixed frame period. FBE systems include wireless devices operating in an unlicensed radio frequency spectrum band in a FBE mode, for instance, a FBE base station. In some cases, a UE in a wireless cellular network may implement the present techniques to determine whether a serving cell base station has acquired access to a wireless channel of the unlicensed radio frequency spectrum band in a certain frame during a fixed frame period when operating in the FBE mode.

Wireless devices operating in unlicensed radio frequency spectrum band may support one or more of load based equipment (LBE) mode and FBE mode. In FBE systems, a timeline may be divided into frames of a certain duration (e.g., fixed frame period (FFP)). The FFP may be configured on a system level and can be, for instance, between 1 and 10 ms. Although advantageous for deployment reasons, presently there exists no system constraint requiring the duration of the fixed frame period (FFP) in a FBE system to correspond to the duration of a (radio) frame of the serving cell based station.

For example, in FBE systems, channel sensing may be performed by a FBE base station at fixed time instances, for instance before starting a transmission in the channel at the beginning of a FFP duration. When the channel is busy, the FBE base station may back-off for at least one FFP and attempt to sense the channel again after the at least one FFP lapses. In LBE systems, the channel sensing may be performed at any time instant and a random back-off may be used when the channel is busy. A serving cell base station may operate in the FBE mode in an unlicensed radio frequency spectrum band for use cases in which LBE systems are excluded such as, for instance, in a factory or private networks.

In some cases, a base station operating in an FBE mode may perform a category-2 (Cat-2) listen-before-talk (LBT) procedure before each frame to acquire a channel occupancy time (COT) for an FFP duration. A UE may be unable to connect to the base station via a random access channel transmission during a fixed fame period if the base station has not successfully acquired a COT for that fixed frame period. Accordingly, in some cases, a UE attempting to connect to a base station in an FBE system may first assess whether a frame is occupied by a serving cell or a neighbor cell before initiating the random access channel procedure during that (same) fixed frame period. Initiating the random access procedure may include the UE to perform a random access channel transmission, namely the transmission of RACH message 1 over the physical random access channel (PRACH) during the fixed frame period.

To make this determination, a UE may monitor downlink signals from the serving cell base station, such as a group common physical downlink control channel. In some examples, for monitoring a group common physical downlink control channel (GC-PDCCH), a UE may be configured in remaining minimum system information (RMSI) broadcast by the base station at regular intervals or through UE-specific radio resource control (RRC) signaling. In some cases, the RMSI may indicate a COT structure of the base station, assisting the UE to perform the random access procedure. The UE may monitor GC-PDCCH to determine whether a frame configured with random access channel resources is occupied by the serving cell base station.

As an addition or alternative to existing GC-PDCCH monitoring techniques, the techniques described herein may allow a UE detecting broadcast and other control signal transmissions in unlicensed radio frequency spectrum band from a base station to initiate a random access channel procedure. In some cases, with initial access the UE may not have the configuration to monitor broadcast signals the GC-PDCCH. Accordingly, the present techniques may include configuring random access channel (RACH) resources indicated via system information, the RACH resources being configured in the same fixed frame period in that a broadcast signal is transmitted by the serving cell base station.

In some cases, the present techniques may include configuring the RACH resources using an indication provided through system information of a broadcast message. In one example, the system information indicating RACH resources may be a minimum system information, such as the master information block (MIB). In some cases, the broadcast message may be periodically broadcast on a physical broadcast channel (PBCH), and may comprise physical layer information of the cell required for the UEs to receive additional system information, such as the remaining minimum system information (RMSI). In some cases, the master information block (MIB) includes a system frame number (SFN) parameter which may indicate the random access channel (RACH) resources.

In some cases, the present techniques may include the UE determining whether the serving cell base station is operating in FBE mode or LBE mode. In one example, the UE may determine the serving cell base station is operating in FBE mode when the serving cell base station requires GC-PDCCH monitoring to initiate a random access procedure. For example, the serving cell base station may require that the UE receive GC-PDCCH before initiating a random access procedure. In one example, the UE may determine the serving cell base station is operating in FBE mode when RMSI (e.g. SIB1) indicates the base station is a FBE base station. In some cases, the RMSI may indicate a configuration of the FFP. In some cases, for physical RACH (PRACH) transmissions in an FBE system, the UE may be configured to perform Cat-2 LBT (as opposed to Cat-4 LBT used in LBE systems). Accordingly, in one example the UE may determine the serving cell base station is operating in FBE mode when a random access channel (RACH) configuration indicates to use Cat-2 LBT. In some examples, the UE may determine the serving cell base station is operating in FBE mode based on information the UE receives from access management function (AMF) during a registration procedure.

In some cases, each cell of a given network (e.g., public land mobile network (PLMN)) may operate in unlicensed radio frequency spectrum band in either LBE mode or FBE mode. When each cell of a PLMN may be either FBE or LBE based cell, the network may specify a first set of UEs to camp on FBE based cells and a second set of UEs to camp on LBE based cells. In one example, UEs configured for industrial Internet-of-things (IoT) may be assigned to camp on FBE based cells. In one example, one or more base stations or all base stations of a PLMN may broadcast neighbor cell information that includes a first list of cells in the PLMN operating in FBE mode and a second list of cells in the PLMN operating in LBE mode. Based on the received neighbor cell information, a UE may apply cell reselection priority to camp either on FBE based cells or LBE based cells.

Aspects of the disclosure are initially described in the context of a wireless communications system. Aspects of the disclosure are also described in the context of wireless communication subsystems and a timeline associated with wireless communications systems. Aspects of the disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts that relate to random access channel transmissions for frame based equipment systems, more specifically to random access channel transmissions using resources associated with a fixed frame period.

FIG.1illustrates an example of a wireless communications system100that supports random access channel transmissions using resources associated with a fixed frame period in accordance with aspects of the present disclosure. The wireless communications system100includes base stations105, UEs115, and a core network130. In some examples, the wireless communications system100may be a Long Term Evolution (LTE) network, an LTE-Advanced (LTE-A) network, an LTE-A Pro network, or a New Radio (NR) network. In some cases, wireless communications system100may support enhanced broadband communications, ultra-reliable (e.g., mission critical) communications, low latency communications, or communications with low-cost and low-complexity devices.

In one example, a device (e.g., UE115or base station105) may receive a broadcast message that includes system information. In some cases, the broadcast message may be received over an unlicensed radio frequency spectrum band. In some cases, the system information may indicate a listen-before-talk (LBT) mode of a base station. In some examples, the LBT mode may be or include a FBE mode or semi-static channel access mode. In some cases, the system information may indicate a set of random access channel resources associated with a fixed frame period. In some examples, the device may monitor, during a particular fixed frame period, a wireless channel of the unlicensed radio frequency spectrum band for control information from the base station based at least in part on the indicated LBT mode. In some cases, the device may determine, based on the monitoring, that the base station has access to the wireless channel during the fixed frame period. In some examples, the device may perform, based at least in part on the determining, a random access channel transmission during the fixed frame period using the set of random access channel resources.

The present techniques provide several advantages over conventional systems. For example, by enabling a UE to determine when a base station has acquired access to a certain frame, the present techniques enable faster connection attempts to the base station compared to conventional systems at initial access because these techniques enable the UE to determine when precisely to attempt performing a random access channel transmission. Also, the present techniques provide an improved conservation of resources compared to conventional systems because the present techniques enable the UE to determine a set of random access channel resources associated with a specific frame or a specific fixed frame period of a frame to which the base station has acquired access.

FIG.2illustrates an example of a wireless communication subsystem200that supports random access channel transmissions using resources associated with a fixed frame period in accordance with aspects of the present disclosure. In some examples, wireless communication subsystem200may implement aspects of wireless communication system100. In some examples, the wireless communications subsystem200may include a mobile services network. In some cases, wireless communications subsystem200may coexist with a fixed services network.

As illustrated, wireless communications subsystem200may include UE115-aand base station105-ain a geographic coverage area110-a, which may be examples of a UE115or a base station105or geographic coverage area110, as described herein with reference toFIG.1. Wireless communications subsystem200may also include downlink205and uplink210. Base station105-amay use downlink205to convey control and/or data information to UE115-a. And UE115-amay use uplink210to convey control and/or data information to base station105-a. In some cases, downlink205may use different time and/or frequency resources than uplink210.

In some examples, base station105-amay generate a message that includes system information. In some cases, base station105-amay transmit the generated message to UE115-a(e.g., via downlink205). In some cases, base station105-amay transmit the message over an unlicensed radio frequency spectrum band. In some cases, base station105-amay broadcast the message. In one example, base station105-amay broadcast the message over an unlicensed radio frequency spectrum band.

In some examples, UE115-amay receive the message from base station105-a. In some cases, UE115-amay receive the message over an unlicensed radio frequency spectrum band. In some cases, UE115-amay identify system information in the message. In some cases, the system information may indicate a listen-before-talk (LBT) mode of base station105-a. In some examples, the LBT mode may be or include a FBE mode or semi-static channel access mode. In some cases, the system information may indicate a set of random access channel resources associated with a fixed frame period.

In some cases, UE115-amay monitor a wireless channel of the unlicensed radio frequency spectrum band during the fixed frame period for control information from the base station105-abased at least in part on the indicated LBT mode.

In some cases, UE115-amay determine, based on the monitoring, whether base station105-ahas access to the wireless channel during the fixed frame period. In some cases, UE115-amay receive an indication from base station105-athat indicates base station105-ahas access to the wireless channel during the fixed frame period. In one example, UE115-amay receive a synchronization signal block (SSB) transmission and determine that the base station105-ahas access to the wireless channel during the fixed frame period based at least in part on receiving the SSB.

In one example, UE115-amay receive additional system information and determine that the base station105-ahas access to the wireless channel during the fixed frame period based at least in part on receiving the additional system information from base station105-a. Examples of additional system information may include remaining minimum system information (RMSI) or a system information block (SIB) received by UE115-aduring the fixed frame period in which UE115-areceives the message from base station105-a.

In one example, UE115-amay receive downlink control information (DCI) that includes a system information radio network temporary identifier (SI-RNTI) and determine that the base station105-ahas access to the wireless channel during the fixed frame period based at least in part on receiving the DCI that includes SI-RNTI from base station105-a. For example, the DCI may carry a downlink grant and include a CRC field which is scrambled with the SI-RNTI. In some cases, the downlink grant may schedule a broadcast signal transmission of other system information, such as a system information block (SIB) not included in the RMSI (e.g., not SIB1).

In one example, UE115-amay receive a paging message and determine that the base station105-ahas access to the wireless channel during the fixed frame period based at least in part on receiving the paging message from base station105-a. In some cases, the paging message may include one or more of: a physical downlink control channel (PDCCH) paging message or a physical downlink shared channel (PDSCH) paging message.

In one example, UE115-amay receive downlink control information (DCI) that includes a paging radio network temporary identifier (P-RNTI) and determine that the base station105-ahas access to the wireless channel during the fixed frame period based at least in part on receiving the P-RNTI from base station105-a. For example, the DCI may carry a downlink grant and include a CRC field which is scrambled with the P-RNTI. In some cases, the downlink grant may schedule a paging message for paging plural UEs.

In one example, UE115-amay receive a random access response (RAR) and determine that the base station105-ahas access to the wireless channel during the fixed frame period based at least in part on receiving the random access response from base station105-a.

In one example, UE115-amay receive from base station105-aa downlink control information (DCI) that includes a random access radio network temporary identifier (RA-RNTI) and determine that the base station105-ahas access to the wireless channel during the fixed frame period based at least in part on receiving the DCI that includes the RA-RNTI. For example, the DCI may carry a downlink grant and include a CRC field which is scrambled with the RA-RNTI. In some cases, the downlink grant may schedule a downlink shared channel transmission of a random access response (RA message 2).

In one example, UE115-amay receive placeholder physical downlink control channel (PDCCH) from base station105-aand determine that the base station105-ahas access to the wireless channel during the fixed frame period based at least in part on receiving the placeholder PDCCH. Examples of the placeholder PDCCH may include an empty PDCCH or “dummy” PDCCH, or an empty RNTI message. A placeholder PDCCH message may include a PDCCH with minimal information (e.g., a PDCCH without explicit configuration for a PDCCH search space). In one example, the placeholder PDCCH may indicate coarse structure indication of the channel occupancy time. In some cases, the placeholder PDCCH may use the same search space as used, for example, by a RMSI transmissions or a paging transmissions, and base station105-amay not provide additional search space configuration for the placeholder PDCCH.

Accordingly, UE115-amay determine that the base station has access to the wireless channel during the fixed frame period based at least in part on receiving system information from the base station. In one example, UE115-amay perform, based on the determining, a random access channel transmission during the fixed frame period. In some cases, UE115-aperforming the random access channel transmission during the fixed frame period may include UE115-ausing the set of random access channel resources associated with the fixed frame period and indicated in the system information in the message received from base station105-a.

FIG.3illustrates an example of a timeline300that supports random access channel transmissions using resources associated with a fixed frame period in accordance with aspects of the present disclosure. In some examples, timeline300may implement aspects of wireless communication system100or wireless communications subsystem200.

In FBE systems, a timeline may be divided into frames of a fixed duration or fixed frame period (FFP). In one example, timeline300is an example of a timeline associated with an FBE system. As shown, timeline300includes frames305,310, and315. In some cases, any one of frames305,310, or315may be frames of an FBE system (e.g., frames associated with a serving base station operating in an FBE mode). In some cases, a duration of any one of frame305, frame310, or frame315may be an FFP duration. In one example, frame310is an example of a frame acquired by a serving base station (e.g., base station105ofFIG.1orFIG.2), while frames305and315may be examples of frames not acquired by the serving base station.

In some examples, a base station (e.g. base station105) may broadcast over an unlicensed radio frequency spectrum band, in a frame other than frames305,310, and315shown inFIG.3, a broadcast message comprising system information. In one example, a UE (e.g., a UE115) may receive this system information. From the system information, the UE may infer a LBT-mode which the base station may use for acquiring channel access. In one example, the indicated LBT mode may correspond to a category-2 (Cat-2) LBT. The system information may also indicate to the UE a set of random access channel resources for uplink transmissions. In one example, the indicated RACH resources may be associated with one or more fixed frame periods, for example, frames305and310(e.g. RACH occasions320,330and340). The system information broadcast message may indicate RACH resources independent of whether the base station successfully acquires the channel during the associated one or more fixed frame periods.

In some examples, the base station may perform a category-2 (Cat-2) listen before talk (LBT) before at least one, preferably each of frames305,310, or315. In one example, the UE may monitor a downlink signal received from a base station in at least one frame (e.g., frame305, or frame310, or frame315) to initiate an uplink transmission in that particular frame. In some cases, a frame may not include any downlink signal from the base station, for example, a scheduled broadcast signal transmission of additional system information. In some cases, the UE may determine that the base station does not have access to the wireless channel, when a frame with configured RACH resources does not include a broadcast signal. Then, the UE may bypass performing a RACH transmission. In some cases, the UE may enter a low-power state or sleep state when the UE determines that a frame with configured RACH resources does not include a broadcast signal.

As shown, frame305may include random access channel resources configured by the network (e.g., RACH occasion320). However, as shown frame305may not include a broadcast signal from a base station that is scheduled for transmission during frame305. Accordingly, a UE may treat the resources of frame305as invalid. In some cases, a UE may treat RACH occasion320in frame305as an invalid RACH occasion because the UE did not receive any broadcast signal from a base station during frame305. In some cases, when a UE determines frame305does not include a broadcast signal, to save power the UE may be configured to go to sleep at least until the end of frame305. In some cases, when a frame does not include a downlink signal (e.g., frame305), then the configuration of the UE may not permit the UE to perform a random access channel transmission.

As shown, frame310may include RACH resources in RACH occasion330and RACH occasion340. When RACH resources are available in a particular frame (e.g., frame310), then a base station may transmit a downlink signal at least at the beginning of that frame. As shown, a base station may transmit a broadcast signal325. However, in the illustrated example the UE may fail to receive the broadcast signal325. As a result, the UE may not be permitted to use RACH resources associated with RACH occasion330. However, in the illustrated example the UE may receive the broadcast signal335. As a result, the UE may be permitted to use RACH resources associated with RACH occasion340. In some cases, the UE may use the RACH resources associated with RACH occasion340to perform a random access channel transmission as part of a random access procedure.

Accordingly, in the illustrated example the UE may select RACH resources of RACH occasion340in conjunction with initiating an uplink transmission in frame310. When the UE detects broadcast signal335from a serving base station, the UE may process broadcast signal335(e.g., processing information in broadcast signal335). In some cases, the UE may determine that frame310is occupied by the serving base station based on the processing of broadcast signal335. In some cases, the UE may determine the duration of the frame310based on the processing of broadcast signal335. For example, the duration of frame310may be indicated by a RMSI in broadcast signal335. In some cases, the UE may determine, based on the processing of broadcast signal335, whether there are any RACH resources available in frame310(e.g., RACH resources in RACH occasion340).

In some cases, after the UE detects broadcast signal335there may be a certain processing delay for the UE to process broadcast signal335. In one example, broadcast signal335may be transmitted in a first slot of frame310(e.g., the first slot of frame310, the second slot of frame310, etc.). The UE may then process broadcast signal335in one or more slots subsequent to the first slot.

In some cases, broadcast signal335may include a primary synchronization signal (PSS) or secondary synchronization signal (SSS). In one example, if a PSS or SSS is transmitted in slot 1 of frame310, then the UE may use one or more subsequent slots (e.g., at least slot 2) to process the PSS/SSS and determine that the detection of broadcast signal335is successful. Thus, in some cases the UE may initiate acquiring RACH resources in slot 3 or slot 4 of frame310. The processing time may be different for different wireless channels. Accordingly, the UE may initiate a RACH transmission as part of a random access process after processing broadcast signal335and before the end of frame310.

In some cases, the UE may use a physical layer (PHY) to detect broadcast signal335from a serving base station. In some examples, there may be no interaction between the PHY and media access control (MAC) layer of the UE. The PHY may detect broadcast signal335, but may not indicate to the MAC whether frame310is available. In some cases, the MAC may select RACH resources of RACH occasion340based on an algorithm of the MAC. In some cases, the MAC may not wait for acknowledgment from the PHY whether frame310is available or not. In one example, after selecting RACH resources of RACH occasion340, the MAC may indicate the selected RACH resources to the PHY for PRACH transmission. After selecting RACH resources of RACH occasion340or indicating the selected RACH resources to the PHY, the PHY may validate whether frame310is available for transmission or not (e.g., validate the RACH resources provided by the MAC) based on information in broadcast signal335. In some cases, if frame310is available, then the PHY may transmit on PRACH. However, if frame310is not available, then the PHY may treat the unavailability of resources as a listen before talk (LBT) uplink failure. In some cases, the PHY may monitor for downlink signals (e.g., broadcast signal335). When the PHY detects broadcast signal335in frame310, the PHY may indicate broadcast signal335to the MAC layer. Based on this indication, the MAC layer may select the RACH resources of RACH occasion340within frame310and the MAC may indicate the selected RACH resources to the PHY for PRACH transmission.

FIG.4illustrates an example of a wireless communication subsystem400that supports random access channel transmissions using resources associated with a fixed frame period in accordance with aspects of the present disclosure. In some examples, wireless communication subsystem400may implement aspects of wireless communication system100.

At405, base station105-bmay broadcast system information in a broadcast message. At410, base station105-bmay transmit, and UE115-bmay receive, the system information broadcast by base station105-bat405. In some cases, base station105-bmay transmit the system information in a broadcast message over an unlicensed radio frequency spectrum band.

At415, UE115-bmay monitor a wireless channel of the unlicensed radio frequency spectrum band. At420, UE115-bmay receive an indication based on the monitoring at415that base station105-bhas access to the wireless channel monitored by UE115-b. Examples of UE115-breceiving the indication at420may include any combination of UE115-breceiving an synchronization signal block (SSB) at420-1, UE115-breceiving additional system information at420-2(e.g., RMSI, SIB), UE115-breceiving a paging message (e.g., PDCCH paging message, PDSCH paging message) at420-3, UE115-breceiving a random access response at420-4, UE115-breceiving a DCI that includes RNTI (P-RNTI, RA-RNTI, system information RNTI (SI-RNTI)) at420-5, or UE115-breceiving a placeholder PDCCH at420-6, or any combination thereof.

In some cases, if the frame acquired by base station105-bincludes an SSB transmission (e.g.,420-1), then UE115-bmay attempt to detect the SSB (e.g. detect PSS/SSS detection or physical broadcast channel (PBCH) demodulation reference signal (DMRS)) to initiate a RACH transmission within the frame or during a fixed frame period of the frame. In some cases, UE115-bmay acquire SSB signal strength before initiating a random access channel procedure by performing a RACH transmission. In some cases, a signal strength threshold may be defined which UE115-bmay use to determine whether a detected signal (e.g., system information message at410, system information message in a broadcast, etc.) can be safely assumed to belong to base station105-b.

In some cases, when a frame includes RMSI or another SIB transmission (e.g.,420-2), UE115-bmay attempt to receive PDCCH identified by SI-RNTI for initiation of the random access procedure by performing a RACH transmission within the frame.

In some cases, a random access procedure may be initiated during a fixed frame period of the frame based on UE115-bdetecting a PDCCH and/or PDSCH paging message (e.g.,420-3) within the frame. In some cases, UE115-bmay trigger PRACH (for connection setup) after UE115-breceives a paging message with its own identity. In some cases, UE115-bmay listen for PDCCH on a paging window of UE115-bor another paging window (e.g., a paging window of a different UE).

In one example, UE115-bmay receive placeholder physical downlink control channel (PDCCH) from base station105-band determine that the base station105-bhas access to the wireless channel during the fixed frame period based at least in part on receiving the placeholder PDCCH. Examples of the placeholder PDCCH may include an empty PDCCH or “dummy” PDCCH, or an empty RNTI message. In some cases, UE115-bmay monitor for control messages that are meant for UE115-bor control message that are meant for UEs other than UE115-b. In some cases, UE115-bmay decode these control messages to determine whether base station105-bhas gained access to a wireless channel for a particular frame. For example, UE115-bmay decode PDCCH transmissions. In some cases, UE115-bmay know where to look for PDCCH transmissions based on search space for system information broadcasted by base station105-b(e.g., the system information message UE115-breceives at410). In some cases, UE115-bmay determine where the PDCCH search space should be based on the system information received at410. In some cases, UE115-bmay search this search space to determine whether a transmission from base station105-bindicates that base station105-bhas gained access to a particular frame. Accordingly, UE115-bmay determine whether UE115-bis enabled to use certain resources (e.g., resources defined by the system information message at410) during this particular fixed frame period to perform a random access channel procedure.

In some cases, UE115-bmay determine where paging PDCCH search space should be based on system information from base station105-b(e.g., system information message broadcasted at410). In some cases, UE115-bmay search this search space to determine whether a transmission from base station105-bindicates that base station105-bhas gained access to a particular frame. Accordingly, UE115-bdetermines it can use other resources (e.g., resources defined by system information message at410) during this particular frame to perform a random access channel procedure.

In some cases, instead of looking in the resources where UE115-bknows paging PDCCH search space would be, UE115-bmay instead analyze the resources indicated in the system information message at410that indicate where the RACH resources should be, or where a random access response (RAR) should be, or where PDCCH with a RAR or with RA-RNTI (e.g., DCI with RA-RNTI) should be. Based on this determination, UE115-bmay look there and the UE may decode the RAR (e.g.,420-4), PDCCH with RAR, PDCCH with RA-RNTI, DCI with RA-RNTI (e.g.,420-5). Based on the decoded information, UE115-bmay use the RACH resources within that same frame that the UE knows are dedicated for uplink RACH transmissions to transmit a RACH request (e.g., RACH message1).

In some cases, the PBCH DMRS may include a cell-specific DMRS signal. In some cases, when UE115-bdetects a DMRS signal from base station105-bin a frame, then UE115-bmay determine that this frame is occupied by base station105-b. In some cases, UE115-bmay determine whether a signal strength of the DMRS signal is greater than a predetermined threshold to determine whether the DMRS signal is from base station105-b.

At425, UE115-bmay determine that base station105-bhas access to the wireless channel during the fixed frame period the system information message is sent at405.

At430, UE115-bmay perform a random access channel (RACH) transmission as part of the random access procedure with base station105-b. In some cases, UE115-bmay perform the RACH transmission based at least in part on at least one indication received by UE115-bat420.

At435, UE115-bmay establish a connection with base station105-bbased on the RACH procedure of430.

FIG.5shows a block diagram500of a device505that supports random access channel transmissions using resources associated with a fixed frame period in accordance with aspects of the present disclosure. The device505may be an example of aspects of a UE115as described herein. The device505may include a receiver510, a communications manager515, and a transmitter520. The device505may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses).

The receiver510may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to random access channel transmissions for frame based equipment systems, etc.). Information may be passed on to other components of the device505. The receiver510may be an example of aspects of the transceiver820described with reference toFIG.8. The receiver510may utilize a single antenna or a set of antennas.

The communications manager515may receive, from a base station over an unlicensed radio frequency spectrum band, a broadcast message including system information, the system information indicating a LBT mode of the base station and a set of random access channel resources associated with a fixed frame period, monitor a wireless channel of the unlicensed radio frequency spectrum band during the fixed frame period for control information from the base station based on the indicated LBT mode, determine, based on the monitoring, that the base station has access to the wireless channel during the fixed frame period, and perform, based on the determining, a random access channel transmission as part of a random access procedure during the fixed frame period using the set of random access channel resources. The communications manager515may be an example of aspects of the communications manager810described herein.

In some cases, the communications manager515may be implemented by a chipset of a wireless modem, and the receiver510and the transmitter520may be implemented by analog or mixed signal components (e.g., antennas, amplifiers, filters, phase shifters, analog to digital converters, digital to analog converters, etc.) connected to the wireless modem. The communications manager515may therefore generate messages and output the messages over a transmit interface to the transmitter520for transmission. Similarly, the communications manager515may obtain received signals from the receiver510over a receive interface, and decode and interpret the received signals. The present techniques provide several advantages over conventional systems. For example, the present techniques enable a chipset of a wireless modem to determine when a base station has acquired access to a certain frame. The present techniques enable faster connection attempt to the base station compared to conventional systems at initial access because these techniques enable the chipset of the wireless modem to determine when precisely to attempt performing a random access channel transmission. Also, the present techniques enable the chipset of the wireless modem to improve the conservation of resources compared to conventional systems because the present techniques enable the chipset of the wireless modem to identify a set of random access channel resources associated with a specific frame or a fixed frame period of the frame to which the base station has acquired access and use the identified random access channel resources to perform a random access channel transmission.

FIG.6shows a block diagram600of a device605that supports random access channel transmissions using resources associated with a fixed frame period in accordance with aspects of the present disclosure. The device605may be an example of aspects of a device505, or a UE115as described herein. The device605may include a receiver610, a communications manager615, and a transmitter640. The device605may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses).

The receiver610may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to random access channel transmissions for frame based equipment systems, etc.). Information may be passed on to other components of the device605. The receiver610may be an example of aspects of the transceiver820described with reference toFIG.8. The receiver610may utilize a single antenna or a set of antennas.

The communications manager615may be an example of aspects of the communications manager515as described herein. The communications manager615may include a system information manager620, a monitoring manager625, an analysis manager630, and a random access manager635. The communications manager615may be an example of aspects of the communications manager810described herein.

The system information manager620may receive, from a base station over an unlicensed radio frequency spectrum band, a broadcast message including system information, the system information indicating a LBT mode of the base station and a set of random access channel resources associated with a fixed frame period. In some examples, the LBT mode may be or include a FBE mode or semi-static channel access mode.

The monitoring manager625may monitor a wireless channel of the unlicensed radio frequency spectrum band during the fixed frame period for control information from the base station based on the indicated LBT mode.

The analysis manager630may determine, based on the monitoring, that the base station has access to the wireless channel during the fixed frame period. The random access manager635may perform, based on the determining, a random access channel transmission as part of a random access procedure during the fixed frame period using the set of random access channel resources.

The transmitter640may transmit signals generated by other components of the device605. In some examples, the transmitter640may be collocated with a receiver610in a transceiver module. For example, the transmitter640may be an example of aspects of the transceiver820described with reference toFIG.8. The transmitter640may utilize a single antenna or a set of antennas.

FIG.7shows a block diagram700of a communications manager705that supports random access channel transmissions using resources associated with a fixed frame period in accordance with aspects of the present disclosure. The communications manager705may be an example of aspects of a communications manager515, a communications manager615, or a communications manager810described herein. The communications manager705may include a system information manager710, a monitoring manager715, an analysis manager720, a random access manager725, an indication manager730, a downlink manager735, a paging manager740, a validation manager745, a resource manager750, a power state manager755, and a priority manager760. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses).

The system information manager710may receive, from a base station over an unlicensed radio frequency spectrum band, a broadcast message including system information, the system information indicating a LBT mode of the base station and a set of random access channel resources associated with a fixed frame period. In some examples, the LBT mode may be or include a FBE mode or semi-static channel access mode.

The monitoring manager715may monitor a wireless channel of the unlicensed radio frequency spectrum band during the fixed frame period for control information from the base station based on the indicated LBT mode.

In some cases, the system information includes a configuration to monitor a group common physical downlink control channel, and where determining the base station is operating in the LBT mode is based on the configuration to monitor the group common physical downlink control channel.

In some cases, the system information includes a configuration to use a category-2 LBT for the random access channel transmission as part of a random access procedure, where determining the base station is operating in the LBT mode is based on the configuration to use category-2 LBT for the random access procedure.

In some cases, the system information includes an indication that the base station is operating in the LBT mode. In some cases, the LBT mode includes a frame based equipment (FBE) LBT mode, and the system information includes a first list of cells operating in the FBE mode and a second list of cells operating in a load based equipment (LBE) mode.

The analysis manager720may determine, based on the monitoring, that the base station has access to the wireless channel during the fixed frame period. In some examples, the analysis manager720may determine a signal strength of the synchronization signal block transmission, where performing the random access channel transmission is based on the determined signal strength of the synchronization signal block transmission satisfying a threshold.

In some examples, the analysis manager720may determine a signal strength of the demodulation reference signal, where performing the random access channel transmission as part of a random access procedure is based on the determined signal strength of the demodulation reference signal satisfying a threshold.

The random access manager725may perform, based on the determining, a random access channel transmission as part of a random access procedure during the fixed frame period using the set of random access channel resources.

In some examples, the random access manager725may perform the random access channel transmission after the UE processes the broadcast message, where the broadcast message is transmitted in a first slot, and where the UE processes the broadcast message in one or more slots subsequent to the first slot.

The indication manager730may receive, based on the monitoring, a synchronization signal block transmission, where determining that the base station has access to the wireless channel is based on the synchronization signal block.

In some examples, the indication manager730may receive, based on the monitoring, additional system information during the fixed frame period, where performing the random access channel transmission is based on the additional system information.

In some examples, the indication manager730may determine whether the frame of the fixed frame period includes a paging message or a downlink control information including a paging radio network temporary identifier, where performing the random access channel transmission is based on whether the frame includes the paging message or the downlink control information.

In some examples, the indication manager730may receive, based on the monitoring, one or more of: a random access response or a downlink control information including a random access radio network temporary identifier, where determining that the base station has access to the wireless channel is based on the random access response or the downlink control information. In some cases, the random access response or the downlink control information is directed to a recipient other than the UE.

In some examples, the indication manager730may determine whether the frame of the fixed frame period includes a physical downlink control channel with a placeholder radio network temporary identifier, where performing the random access channel transmission is based on whether the frame includes the physical downlink control channel with the placeholder radio network temporary identifier.

In some examples, the indication manager730may detect the physical downlink control channel with the placeholder radio network temporary identifier in a search space of the frame, where the search space of the frame is associated with one or more of: system information or paging.

In some examples, the indication manager730may determine whether the frame of the fixed frame period includes a demodulation reference signal, where performing the random access channel transmission is based on whether the frame includes the demodulation reference signal.

In some examples, the indication manager730may receive an authentication management message associated with a registration procedure, where determining the base station is operating in the LBT mode is based at least in part the authentication management message.

The downlink manager735may receive a downlink grant based on a system information radio network temporary identifier associated with the additional system information, where performing the random access channel transmission is based on the downlink grant.

The paging manager740may identify a paging window based on one or more of: an identifier of the UE or an identifier of the base station, where receiving the paging message or the downlink control information is based on the paging window.

The validation manager745may determine a validity of resources associated with the random access channel transmission based on a duration associated with the fixed frame period. In some examples, the validation manager745may determine, via the physical layer, a validity of the selected resources, where performing the random access channel transmission is based on the determined validity of the selected resources.

In some examples, the validation manager745may indicate an LBT failure to the media access control layer when the selected resources are determined to be invalid. In some examples, the validation manager745may determine, based on the broadcast message and the fixed frame period, a validity of the random access channel resources, where performing the random access channel procedure is based on the validity of the random access channel resources. In some examples, the validation manager745may send an indication of the validity of the random access channel resources from a physical layer of the UE to a media access control layer of the UE.

The resource manager750may select, via a media access control layer of the UE, resources available in the fixed frame period for the random access channel transmission. In some examples, the resource manager750may indicate, via the media access control layer, the selected resources to a physical layer of the UE, where the UE detects the broadcast message via the physical layer.

The power state manager755may enter a low-power state or sleep state based on determining a fixed frame period does not include at least one broadcast message, where the UE treats resources available in the fixed frame period for the random access channel transmission as invalid based on determining the fixed frame period does not include the at least one broadcast message.

The priority manager760may apply a cell reselection priority to camp either on the cells operating in FBE mode or on the cells operating in the LBE mode.

The communications manager810may receive, from a base station over an unlicensed radio frequency spectrum band, a broadcast message including system information, the system information indicating a LBT mode of the base station and a set of random access channel resources associated with a fixed frame period, monitor a wireless channel of the unlicensed radio frequency spectrum band during the fixed frame period for control information from the base station based on the indicated LBT mode, determine, based on the monitoring, that the base station has access to the wireless channel during the fixed frame period, and perform, based on the determining, a random access channel transmission as part of a random access procedure during the fixed frame period using the set of random access channel resources.

The memory830may include RAM and ROM. The memory830may store computer-readable, computer-executable code835including instructions that, when executed, cause the processor to perform various functions described herein. In some cases, the memory830may contain, among other things, a BIOS which may control basic hardware or software operation such as the interaction with peripheral components or devices.

The code835may include instructions to implement aspects of the present disclosure, including instructions to support wireless communications. The code835may be stored in a non-transitory computer-readable medium such as system memory or other type of memory. In some cases, the code835may not be directly executable by the processor840but may cause a computer (e.g., when compiled and executed) to perform functions described herein. The present techniques provide several advantages over conventional systems. For example, by enabling a UE to determine when a base station has acquired access to a certain frame, the present techniques enable improved battery life for a UE compared to conventional systems because these techniques enable the UE to determine when precisely to attempt performing a random access channel transmission. Also, the present techniques provide an improved user experience compared to conventional systems because the present techniques enable the UE to determine a set of random access channel resources associated with a specific frame or a specific fixed frame period of a frame to which the base station has acquired access and use the resources to establish a quicker connection compared to conventional systems.

FIG.9shows a flowchart illustrating a method900that supports random access channel transmissions using resources associated with a fixed frame period in accordance with aspects of the present disclosure. The operations of method900may be implemented by a UE115or its components as described herein. For example, the operations of method900may be performed by a communications manager as described with reference toFIGS.5through8. In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the functions described herein. Additionally or alternatively, a UE may perform aspects of the functions described herein using special-purpose hardware.

At905, the UE may receive, from a base station over an unlicensed radio frequency spectrum band, a broadcast message including system information, the system information indicating a LBT mode of the base station and a set of random access channel resources associated with a fixed frame period. The operations of905may be performed according to the methods described herein. In some examples, aspects of the operations of905may be performed by a system information manager as described with reference toFIGS.5through8.

At910, the UE may monitor a wireless channel of the unlicensed radio frequency spectrum band during the fixed frame period for control information from the base station based on the indicated LBT mode. The operations of910may be performed according to the methods described herein. In some examples, aspects of the operations of910may be performed by a monitoring manager as described with reference toFIGS.5through8.

At915, the UE may determine, based on the monitoring, that the base station has access to the wireless channel during the fixed frame period. The operations of915may be performed according to the methods described herein. In some examples, aspects of the operations of915may be performed by an analysis manager as described with reference toFIGS.5through8.

At920, the UE may perform, based on the determining, a random access channel transmission during the fixed frame period using the set of random access channel resources. The operations of920may be performed according to the methods described herein. In some examples, aspects of the operations of920may be performed by a random access manager as described with reference toFIGS.5through8.

FIG.10shows a flowchart illustrating a method1000that supports random access channel transmissions using resources associated with a fixed frame period in accordance with aspects of the present disclosure. The operations of method1000may be implemented by a UE115or its components as described herein. For example, the operations of method1000may be performed by a communications manager as described with reference toFIGS.5through8. In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the functions described herein. Additionally or alternatively, a UE may perform aspects of the functions described herein using special-purpose hardware.

At1005, the UE may receive, from a base station over an unlicensed radio frequency spectrum band, a broadcast message including system information, the system information indicating a LBT mode of the base station and a set of random access channel resources associated with a fixed frame period. The operations of1005may be performed according to the methods described herein. In some examples, aspects of the operations of1005may be performed by a system information manager as described with reference toFIGS.5through8.

At1010, the UE may monitor a wireless channel of the unlicensed radio frequency spectrum band during the fixed frame period for control information from the base station based on the indicated LBT mode. The operations of1010may be performed according to the methods described herein. In some examples, aspects of the operations of1010may be performed by a monitoring manager as described with reference toFIGS.5through8.

At1015, the UE may receive, based on the monitoring, a synchronization signal block transmission. In some cases, determining that the base station has access to the wireless channel is based on the synchronization signal block (SSB). The operations of1015may be performed according to the methods described herein. In some examples, aspects of the operations of1015may be performed by an indication manager as described with reference toFIGS.5through8.

At1020, the UE may determine a signal strength of the synchronization signal block transmission and determine that the determined signal strength of the synchronization signal block transmission satisfies a threshold. In some cases, performing the random access channel transmission as part of a random access procedure is based on the determined signal strength of the synchronization signal block transmission satisfying the threshold. The operations of1020may be performed according to the methods described herein. In some examples, aspects of the operations of1020may be performed by an analysis manager as described with reference toFIGS.5through8.

At1025, the UE may determine, based on the monitoring and the determined signal strength satisfying the threshold, that the base station has access to the wireless channel during the fixed frame period. The operations of1025may be performed according to the methods described herein. In some examples, aspects of the operations of1025may be performed by an analysis manager as described with reference toFIGS.5through8.

At1030, the UE may perform, based on the determining the base station has access to the wireless channel, a random access channel transmission as part of a random access procedure during the fixed frame period using the set of random access channel resources. The operations of1030may be performed according to the methods described herein. In some examples, aspects of the operations of1030may be performed by a random access manager as described with reference toFIGS.5through8.

FIG.11shows a flowchart illustrating a method1100that supports random access channel transmissions for fixed frame period based equipment systems in accordance with aspects of the present disclosure. The operations of method1100may be implemented by a UE115or its components as described herein. For example, the operations of method1100may be performed by a communications manager as described with reference toFIGS.5through8. In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the functions described herein. Additionally or alternatively, a UE may perform aspects of the functions described herein using special-purpose hardware.

At1105, the UE may receive, from a base station over an unlicensed radio frequency spectrum band, a broadcast message including system information, the system information indicating a LBT mode of the base station and a set of random access channel resources associated with a fixed frame period. In some examples, the LBT mode may be or include a FBE mode or semi-static channel access mode. The operations of1105may be performed according to the methods described herein. In some examples, aspects of the operations of1105may be performed by a system information manager as described with reference toFIGS.5through8.

At1110, the UE may monitor a wireless channel of the unlicensed radio frequency spectrum band during the fixed frame period for control information from the base station based on the indicated LBT mode. The operations of1110may be performed according to the methods described herein. In some examples, aspects of the operations of1110may be performed by a monitoring manager as described with reference toFIGS.5through8.

At1115, the UE may receive, based on the monitoring, additional system information (e.g., remaining minimum system information (RMSI) or other system information blocks (SIBs)) during the fixed frame period, where performing the random access channel transmission is based on the additional system information. The operations of1115may be performed according to the methods described herein. In some examples, aspects of the operations of1115may be performed by an indication manager as described with reference toFIGS.5through8.

At1120, the UE may receive a downlink grant based on a system information radio network temporary identifier (SI-RNTI) associated with the additional system information For example, the UE may receive the downlink grant from the base station in form of downlink control information (DCI) including a CRC field which is scrambled with the associated SI-RNTI. The downlink grant may schedule a broadcast signal transmission of other system information, such as a system information block (SIB) not included in the RMSI (e.g., not SIB1). In some cases, performing the random access channel transmission as part of a random access procedure is based on the downlink grant. The operations of1120may be performed according to the methods described herein. In some examples, aspects of the operations of1120may be performed by a downlink manager as described with reference toFIGS.5through8.

At1125, the UE may determine, based on the monitoring and receiving the downlink grant, that the base station has access to the wireless channel during the fixed frame period. The operations of1125may be performed according to the methods described herein. In some examples, aspects of the operations of1125may be performed by an analysis manager as described with reference toFIGS.5through8.

At1130, the UE may perform, based on the determining the base station has access to the wireless channel, a random access channel transmission as part of a random access procedure during the fixed frame period using the set of random access channel resources. The operations of1130may be performed according to the methods described herein. In some examples, aspects of the operations of1130may be performed by a random access manager as described with reference toFIGS.5through8.