WO2023149825A1

WO2023149825A1 - Random access procedure

Info

Publication number: WO2023149825A1
Application number: PCT/SE2022/050123
Authority: WO
Inventors: Niklas JALDÉN; Peter ÖKVIST
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2022-02-04
Filing date: 2022-02-04
Publication date: 2023-08-10

Abstract

A method (200) performed by a UE (102). The method includes obtaining (s202) from a network node (104) configuration information identifying a random access, RA, resource. The method also includes storing (s204) the configuration information. The method also includes detecting (s206) an RA trigger, wherein the RA trigger is not a beam failure event. The method further includes after detecting the RA trigger, using (s208) the stored identified RA resource to perform an RA procedure to establish a logical connection with the network node.

Description

METHOD FOR PERFORMING A RANDOM ACCESS PROCEDURE USING A CONFIGURED RANDOM ACCESS RESOURCE ASSOCIATED WITH A PARTICULAR BEAM

TECHNICAL FIELD

[001] Disclosed are embodiments related to the random access (RA) procedure for establishing a connection with a network node (e.g., 5G base station (gNB)).

BACKGROUND

[002] 1. Initial Access

[003] Before a user equipment (UE) (i.e., a communication device capable of communicating wirelessly with a network node (e.g., a base station)) can properly communicate within another communication device (e.g., a server, another UE, etc), the UE must perform what is known as “cell search” to find, identify, and synchronize with a cell served by a network node. Then, the UE must acquire basic system information, and perform an access barring check to determine whether or not the UE is allowed to use the cell for network connectivity. If the access is allowed, the UE will then perform what is known as a random access (RA) procedure to establish a connection (e.g., a Radio Resource Control (RRC) connection) with the network node. Examples of UEs include: smartphones, sensors, appliances, meters, computers, servers, etc.

[004] 1.1. New Radio (NR) cell search and System Information Acquisition

[005] In NR, the combination of synchronization signals (SSs) and a physical broadcast channel (PBCH) is referred to as a SS/PBCH block (SSB). Similar to Long Term Evolution (LTE), a pair of synchronization signals (i.e., a primary synchronization signal (PSS) and secondary synchronization signal (SSS)) is periodically transmitted on downlink from each cell to allow a UE to initially access to the network. By detecting SS, a UE can obtain the physical cell identity, achieve downlink synchronization in both time and frequency, and acquire the timing for the Physical Broadcast Channel (PBCH).

[006] The PBCH carries the master information block (MIB), which contains system information that enables a UE to acquire System Information Block 1 (SIB 1). SIB1 carries system information that enables the UE to perform the random-access procedure.

[007] 1.2. A 4-step random access procedure [008] The 4-step random access produce is also referred to as the Type-1 random access procedure. In the first step of the 4-step RA procedure, a UE initiates the RA procedure by transmitting a RA preamble (RAP) (a.k.a., “Message 1” or “Msg 1”) on the Physical Random Access Channel (PRACH).

[009] In the second step, which occurs after the network node detects the Msgl, the network node (e.g., 5G base station (gNB)) responds by transmitting to the UE on the Physical Downlink Control Channel (PDCCH) Downlink Control Information (DCI) (e.g., DCI format 1 0) to prepare the UE to receive a random-access response (RAR) (a.k.a., “Message 2” or “Msg2”) and then sends the RAR on the Physical Downlink Shared Channel (PDSCH).

[0010] In the third step, after successfully decoding Msg2, the UE continues the procedure by transmitting a message (a.k.a., “Message 3” or “Msg3”) on the Physical Uplink Shared Channel (PUSCH). Msg3 is or contains an RRC connection establishment request.

[0011] In the fourth step of the procedure, the gNB transmits a message (a.k.a., “Message 4” or “Msg4”) on the Physical Downlink Shared Channel (PDSCH) for contention resolution.

[0012] 1.3. 2-step random access procedure

[0013] The 2-step random access produce is also referred to as the Type-2 random access procedure. In the first step, a UE sends on the PUSCH a first message (MsgA) that includes a random access preamble together with higher layer data such as an RRC connection request possibly with some small payload. In the second step, after detecting the MsgA, the network node sends to the UE DCI (e.g., DCI format 1 0) on the PDCCH and then sends an RAR (a.k.a., “MsgB”) which includes a UE identifier assignment, timing advance information, contention resolution message, etc.

[0014] The time and frequency resource on which a random-access preamble (Msg 1 or MsgA) is transmitted is defined as a RACH occasion or PRACH occasion.

[0015] When the RA procedure is successfully completed, the UE moves to a connected state (e.g., RRC connected). That is, the UE has formed a logical connection with the network node.

[0016] 2. Beam Selection [0017] During initial access, network node may know the best beam to use to communicate with the UE. This is done by linking each SSB time index to a specific beam and to a specific RACH resource (slot and/or preamble). When the UE uses a specific RACH resource, the network node will know which RACH resource was used and then use this information to determine the SSB time index to which the RACH resource is linked, and then the network node can determine the beam to which the determined SSB time index is linked.

[0018] That is, beam establishment during initial access may be enabled by associating different SSB time indices with different RACH occasions and/or different preamble sequences. As different SSB time indices may correspond to SSB transmissions in different downlink beams, the network (based on received preamble) may determine the downlink beam in which the corresponding UE is “located”.

[0019] This beam may then be used as an initial beam for subsequent downlink transmissions to the UE. With an association between SSB time index and RACH occasion is such that a given time-domain RACH occasion corresponds to one specific SSB time index, the network will know when in time a preamble transmission from UEs within a specific downlink beam will take place. Assuming UL/DL “beam correspondence,” the network may then focus the corresponding uplink receiver beam in the direction of the beamformed preamble reception.

[0020] 3. Radio Link Failures

[0021] In the context of beam management, there are also methods described how to mitigate impact of radio link failures in aspects of beam management. A UE’s Medium Access Control (MAC) entity may be configured by Radio Resource Control (RRC) with a beam failure recovery procedure which is used for indicating to the serving network node of a new SSB or CSI-RS when beam failure is detected on the serving SSB(s)/CSI-RS(s).

[0022] In that regard, a BeamFailureRecoveryConfig information element (IE) is used to configure the UE with RACH resources and candidate beams for beam failure recovery in case of beam failure detection (see 3GPP TS 38.331 V16.7.0, section 6.3.2 and 38.321, section 5.1.1.). The BeamFailureRecoveryConfig IE is shown in Table 1 below.

TABLE 1

[0023] The information elements contained within the BeamFailureRecoveryConfig

IE are described in Table 2 below.

TABLE 2

[0024] This feature enables faster setup/initiation of the beam search process to mitigate end-user delays., etc.

[0025] Beam Failure detection and recovery procedure can be summarized as:

[0026] Step 1 : UE detects beam failure;

[0027] Step 2: UE searches for another candidate beam with good quality;

[0028] Step 3: If a predefined number of Beam Failure is detected, the UE triggers beam failure recovery process with the candidate beam (PRACH) (UE send PRACH with the ID specified in BFR-SSB-Resource.ra-Preamblelndex);

[0029] Step 4: The network node replies to the Beam Failure Recovery request (RACH response (network node send DCI for msg2 via the search space specified by recoverySearchSpacelD), where

PRACH-ResourceDedi catedBFR : : = CHOICE { ssb BFR-SSB-Resource , csi -RS BFR-csiRS-Resource

I and furthermore, where:

BFR-SSB-Resource : : = SEQUENCE { ssb SSB-lndex , ra-Preambl eindex INTEGER (0. .63) ,

I

BFR-CSIRS-Resource : : = SEQUENCE { csi -RS NZP-csi-RS-Resourceid , ra-Occasi onLi st SEQUENCE (SlZEfl . . maxRA-Occasi onsPerCSlRS) )

OF INTEGER (0 . . maxRA-Occasi ons-1) OPTIONAL , -- Need R ra-Preambl eindex INTEGER (0. .63) OPTIONAL , -- Need R

[0030] By transmitting a preamble on the dedicated RA resources corresponding to selected CSI-RS/SSB, the UE not only informs the network node that it has detected beam failure but also indicates the identified beam. UE declares beam failure when the number of beam failure instance indications from the physical layer reaches a configured threshold before a configured timer expires.

SUMMARY

[0031] Certain challenges presently exist. For instance, in some scenarios, such as fixed-wireless-access solutions where a stationary UE (e.g., a customer premise equipment (CPE)) is providing connectivity to a building, many mobility -catering solutions may be less important for proper operation. For example, it seems less relevant having a beam sweeping solution (e.g. wide SSB beam to narrow traffic beam) to improve mobility robustness and blocking recovery when it is known that the UE always will be “stationary” (i.e., within the coverage of a particular beam). From measurements it has been observed that the main propagation paths remain constant for long period of times (read days/weeks/months) as these depend on fixed structures in the environment such as reflections on larger buildings.

[0032] Accordingly, in one aspect there is provided a method performed by a UE. The method includes obtaining from a network node configuration information identifying a RA resource. The method also includes storing the configuration information. The method also includes detecting an RA trigger, wherein the RA trigger is not a beam failure event. The method further includes after detecting the RA trigger, using the stored identified RA resource to perform an RA procedure to establish a logical connection with the network node.

[0033] In another aspect there is provided a computer program comprising instructions which when executed by processing circuitry of a UE, causes the UE to perform the above described UE method. In another aspect there is provided a carrier containing the computer program, wherein the carrier is one of an electronic signal, an optical signal, a radio signal, and a computer readable storage medium.

[0034] In another aspect there is provided a UE where the UE is configured to perform the UE methods disclosed herein. In some embodiments, the UE includes processing circuitry and a memory containing instructions executable by the processing circuitry, whereby the UE is configured to perform the UE methods disclosed herein.

[0035] In another aspect there is provided a method performed by a network node. The method includes associating a random access, RA, resource with a particular beam. The also method includes obtaining information indicating that a particular user equipment, UE (102), over a given period of time, is likely to be within the coverage of the particular beam. The method further includes providing to the UE configuration information identifying the RA resource so that the UE will use the RA resource to perform an RA procedure for establishing a logical connection with the network node

[0036] In another aspect there is provided a computer program comprising instructions which when executed by processing circuitry of a network node, causes the network node to perform the above described network node method. In another aspect there is provided a carrier containing the computer program, wherein the carrier is one of an electronic signal, an optical signal, a radio signal, and a computer readable storage medium.

[0037] In another aspect there is provided a network node where the network node is configured to perform the network node methods disclosed herein. In some embodiments, the network node includes processing circuitry and a memory containing instructions executable by the processing circuitry, whereby the network node is configured to perform the network node methods disclosed herein.

[0038] The embodiments are advantageous in that they provide a stationary UE with means to (re-)connect to its serving cell without having to go through ordinary beam management (search) procedures, which may improve connection setup time as beam search time consuming procedures for RACH (etc.) is avoided.

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate various embodiments.

[0040] FIG. 1 illustrates a 4-step random access produce.

[0041] FIG. 2 is a flowchart illustrating a process according to some embodiments.

[0042] FIG. 3 is a flowchart illustrating a process according to some embodiments.

[0043] FIG. 4 illustrates a network node according to some embodiments.

[0044] FIG. 5 illustrates a UE according to some embodiments.

DETAILED DESCRIPTION

[0045] Embodiments are described wherein a network node (for example an base station and/or a management node) obtains statistics relating to transmit (Tx) and/or receive (Rx) beams used to communicate with a UE. Based on the statistics, the network node may provide the UE with configuration information to be used at later points in time when the UE needs to reconnect to the network. For example, there is provided a method where a UE reconnects to the network using the configuration information and thereby avoids beam search time consuming procedures for RACH (etc.). In some embodiments, the network node first determines whether UE is stationary (i.e., likely to be within the coverage of a particular beam) and provides the configuration information to the UE as a result of determining that the UE is stationary.

[0046] FIG. 1 is a message flow diagram illustrating a process according to one embodiment. This process results in a UE 102 establishing a logical connection (e.g., a Radio Resource Control (RRC) connection) with a network node 104, which may comprise or consist of a base station (e.g., 4G base station (eNB) or a 5G base station (gNB)).

[0047] In a first step, network node 104 determines that UE 102 is stationary. In some embodiments, determining whether UE 102 is stationary can be based on statistics of beams used to serve UE 102, statistics of the channel information, out-of-band application layer information (e.g., such as a GNSS/GPS signal indicating no mobility), or extracted from UE type (or UE class) by means of IMEI numbers or other.

[0048] In a next step, network node 104, as a result of determining that UE 102 is stationary, determines, based on, for example, historical information, a preferred beam for use in communicating with UE 102. For instance, the historical information may include beam data gathered over a long period of time (weeks, months, etc.) or it may include beam gathered over a shorter period of time (hours, days, etc.) where the beam data identifies beams used by network node 104 to communicate with UE 101. The preferred beam is the beam that is used most often by network node 104 to communicate with UE 101.

[0049] After selecting at least a preferred beam, network node 104 associates (e.g., links) an RA resource with the preferred beam. For example, network node 104 may associate the RA resource with any one or more of the following: set of transmission coefficients (i.e., phase and amplitude relations between antenna elements) corresponding to the beam, a spatial filter corresponding to the beam; a set of beamforming weights corresponding to the beam; a precoding matrix corresponding to the beam; or a beam index pointing to any of the above. In one embodiment, the RA resource consists of or comprises the beam index.

[0050] In a next step, network node provides to UE 102 configuration information (CI) identifying the RA resource (the configuration may be provided in an RRC message transmitted to UE 102). For example, during a period of time during which UE 102 is in an RRC connected state with network node 104, network node 104 may transmit to UE 102 a message containing a BeamFastSetupConfig IE containing the configuration information. In one embodiment, the configuration information comprises: 1) candidate beam resource and 2) for each candidate beam resource, an associated RA resource (reference signal Resource ID, Preamble ID, RACH occasion, etc.). For instance, the configuration information included in the BeamFastSetupConfig IE may comprise or consist of a candidateBeamRSList IE defined above. Accordingly, the BeamFastSetupConfig IE is similar in function to the BeamFailureRecoveryConfig IE but the purpose of the BeamFastSetupConfig IE is to configure a stationary UE to skip the ordinary RA procedure to do a quick-simplified one rather than recover from a beam failure. Thus, there may be one set of “resources, beams etc.” associated with beam failure recovery (i.e., BeamFalureRecovery Config) and a potential other set of “resources, beams etc.” associated with the beam fast setup approach (i.e., BeamFastSetupConfig).

[0051] The UE will then store the configuration information for later use when the UE needs to re-establish a connection with network node 104. The BeamFastSetupConfig message may also contain an indicator that the configuration information is for use in a feat beam set up and should only be used by the UE if the UE is still within the coverage of the preferred beam (e.g., the UE has not moved (or moved very little) since obtaining the configuration information).

[0052] At some later point in time (e.g., after the UE has transitioned from a connected state to an idle state) UE 102 detects an RA trigger. The RA trigger may be: a page message address to UE 102; that UE 102 has received a message (e.g., received via a wireless local area network) that UE 102 needs to relay to network node 104; or expiration of a timer. After detecting the RA trigger, UE 102 uses the stored RA resource to perform an RA procedure to re-establish a logical connection with the network node. In one embodiment, after detecting the RA trigger and before using the stored RA resource to perform the RA procedure, UE 102 determines whether or not it should use the stored RA resource to perform the RA procedure. For example, UE 102 should only use the stored RA resource to perform the RA procedure if the UE is still within (or likely still within) the coverage of the beam with which the RA resource is associated. The UE can determine this based on its current position. For instance, if the UE has not moved (or moved only very little) during a given period of time, then the UE is likely to be within the coverage of the beam. [0053] For example, UE 102 may perform the 2-step or 4-step RA procedure (the 4- step procedure is shown in FIG. 1). As shown in FIG. 1, in a first step of the RA procedure, UE 102 initiates the RA procedure by transmitting a random access preamble (RAP) (a.k.a., “Message 1” or “Msg 1”) on the Physical Random Access Channel (PRACH). The RAP selected by UE 102 may be a RAP identified in the configuration information and/or the time/frequency resource used to transmit the RAP (i.e., RACH occasion) may be a RACH occasion identified in the configuration information). After detecting the Msgl, the network node 104 responds by transmitting to the UE on the Physical Downlink Control Channel (PDCCH) Downlink Control Information (DCI) (e.g., DCI format 1 0) to prepare the UE to receive a random-access response (RAR) (a.k.a., “Message 2” or “Msg2”) and then sends the RAR on the Physical Downlink Shared Channel (PDSCH). In the third step, after successfully decoding Msg2, the UE 102 continues the procedure by transmitting a message (a.k.a., “Message 3” or “Msg3”) on the Physical Uplink Shared Channel (PUSCH). Msg3 is or contains an RRC connection establishment request. In embodiments where the RA resource comprises a beam index, Msg3 may include the beam index (or MsgA may include the beam index when UE 102 uses the 2-step procedure). In the last step of the 4-step procedure, the gNB transmits a message (a.k.a., “Message 4” or “Msg4”) on the Physical Downlink Shared Channel (PDSCH) for contention resolution.

[0054] The network node 104 will detect that the UE has used the RA resource to perform the RA procedure, and, as a result of the detecting, the network node uses the beam with which the RA resource is associated to communicate with the UE.

[0055] Further embodiments

[0056] In the data collection step (i.e. the step of collecting data about used Rx/Tx beam (index, weights, precoders, etc.) over weekday, day hours, etc.) additional information may be collected and used to determine a preferred beam. Such additional information may include: service characteristics (e.g., E2E SLA fulfilment, Quality-of-Service (QoS), delay, aggregated UL/DL bitrates, etc.); current weather conditions (e.g., rain, snow, etc); road traffic (in terms of vehicles) and infrastructure information (if relevant for the considered nodes’ deployment); detected anomalies; and back-end service usage (e.g. number of people in served building(s), associated service types (such as streaming/interactive video, speech)). The served peoples’ schedules, etc., may be managed by an application server in conjunction with the network node. In the scenario UE acting as a WiFi-cellular bridge or similar, the network node may itself (or via previously provided calendar information obtained from a cloud server related to at least one relevant person) determine relevant operation hours, etc.

[0057] Using the gathered information, a model describing beam usage as a statistics function of combinations of above may be considered as input to what beam-index associated preamble that should be used given a later context. In a further aspect a statistical model may include a Machine Learning (ML) model such as recurrent neural network (RNN) with features extracted corresponding to an access network key performance indicators (KPIs), end-user QoS metric, connection establishment delay, and environment/weather conditions, etc. The output of the ML model may be a preferred beam index (SSB, CSI-RS) or an associated preamble to be used in a next RACH given current conditions.

[0058] FIG. 2 is a flowchart illustrating a process 200 according to an embodiment that is performed by UE 102. Process 200 may begin in step s202. Step s202 comprises obtaining from network node 104 configuration information identifying a RA resource. In some embodiments, the configuration information comprises: a preamble identifier, ID, identifying a preamble, a reference signal resource ID identifying a reference signal resource, and/or information identifying Random Access Channel, RACH, occasion.

[0059] Step s204 comprises storing the configuration information. Step s206 comprises detecting an RA trigger, wherein the RA trigger is not a beam failure event. Step s208 comprises, after detecting the RA trigger, using the stored identified RA resource to perform an RA procedure to establish a logical connection with the network node.

[001] In some embodiments, the process also includes, after detecting the RA trigger and before using stored identified RA resource to perform the RA procedure, determining, based on location information, whether or not to use the stored configuration information. In some embodiments, the location information indicates whether or not the UE is likely within the coverage of a particular beam used by the network node. In some embodiments, the UE uses the stored identified RA resource to perform the RA procedure as a result of determining, based on the location information, that the UE is likely within the coverage of the particular beam.

[002] In some embodiments, the UE does not have a logical connection with the network node at the time the UE detects the RA trigger. In some embodiments, the UE is in an idle state at the time the UE detects the RA trigger. In some embodiments, the UE receives the configuration information in a period of time during which the UE has an active logical connection with the network node.

[003] In some embodiments, detecting the RA trigger comprises: detecting a page message addressed to the UE; detecting that the UE needs to forward a received message to a network node; or detecting that at least a certain amount of time has elapsed from a prior point in time.

[004] In some embodiments, the identified RA resource is a preamble, and using the identified RA resource to perform the RA procedure comprises transmitting the preamble to the network node.

[005] FIG. 3 is a flowchart illustrating a process 300 according to an embodiment that is performed by a network node (e.g., network node 104). Process 300 may begin in step s302.

[006] Step s302 comprises associating a random access, RA, resource with a particular beam.

[007] Step s304 comprises obtaining information indicating that a particular UE (e.g. UE 102), over a given period of time, is likely to be within the coverage of the particular beam. In some embodiments, the information comprises statistics associated with the particular beam and the particular UE. In some embodiments, the statistics indicate a degree to which the particular beam was used to communicate with the UE over a particular period of time. In some embodiments, obtaining the information comprises obtaining the information from a ML model. In some embodiments, the information obtained from the ML model comprises a preamble ID identifying the particular beam. In some embodiments the process also includes, prior to obtaining the information from the ML model, obtaining information pertaining to the UE, the information pertaining to the UE comprising: current weather conditions experienced by the UE, service characteristics of services used by, or expected to be used by, the UE, or road traffic information.

[008] Step s306 comprises providing to the UE configuration information identifying the RA resource so that the UE will use the RA resource to perform an RA procedure for establishing a logical connection with the network node.

[009] In some embodiments the process also includes detecting that the UE has used the RA resource to perform the RA procedure, and, as a result of the detecting, using the beam with which the RA resource is associated to communicate with the UE. [0010] FIG. 4 is a block diagram of network node 104, according to some embodiments, for performing network node methods disclosed herein. As shown in FIG. 4, network node 104 may comprise: processing circuitry (PC) 402, which may include one or more processors (P) 455 (e.g., one or more general purpose microprocessors and/or one or more other processors, such as an application specific integrated circuit (ASIC), field- programmable gate arrays (FPGAs), and the like), which processors may be co-located in a single housing or in a single data center or may be geographically distributed (i.e., network node 104 may be a distributed computing apparatus where some function are performed in one location and other functions performed in another location); at least one network interface 468 comprising a transmitter (Tx) 465 and a receiver (Rx) 467 for enabling network node 104 to transmit data to and receive data from other nodes connected to a network 110 (e.g., an Internet Protocol (IP) network) to which network interface 468 is connected; communication circuitry 448, which is coupled to an antenna arrangement 449 comprising one or more antennas and which comprises a transmitter (Tx) 445 and a receiver (Rx) 447 for enabling network node 104 to transmit data and receive data (e.g., wirelessly transmit/receive data); and a local storage unit (a.k.a., “data storage system”) 408, which may include one or more non-volatile storage devices and/or one or more volatile storage devices. In embodiments where PC 402 includes a programmable processor, a computer program product (CPP) 441 may be provided. CPP 441 includes a computer readable medium (CRM) 442 storing a computer program (CP) 443 comprising computer readable instructions (CRI) 444. CRM 442 may be a non-transitory computer readable medium, such as, magnetic media (e.g., a hard disk), optical media, memory devices (e.g., random access memory, flash memory), and the like. In some embodiments, the CRI 444 of computer program 443 is configured such that when executed by PC 402, the CRI causes network node 104 to perform steps described herein (e.g., steps described herein with reference to the flow charts). In other embodiments, network node 104 may be configured to perform steps described herein without the need for code. That is, for example, PC 402 may consist merely of one or more ASICs. Hence, the features of the embodiments described herein may be implemented in hardware and/or software.

[0011] FIG. 5 is a block diagram of UE 102, according to some embodiments. As shown in FIG. 5, UE 102 may comprise: processing circuitry (PC) 502, which may include one or more processors (P) 555 (e.g., one or more general purpose microprocessors and/or one or more other processors, such as an application specific integrated circuit (ASIC), field- programmable gate arrays (FPGAs), and the like); communication circuitry 548, which is coupled to an antenna arrangement 549 comprising one or more antennas and which comprises a transmitter (Tx) 545 and a receiver (Rx) 547 for enabling UE 102 to transmit data and receive data (e.g., wirelessly transmit/receive data); and a local storage unit (a.k.a., “data storage system”) 508, which may include one or more non-volatile storage devices and/or one or more volatile storage devices. In embodiments where PC 502 includes a programmable processor, a computer program product (CPP) 541 may be provided. CPP 541 includes a computer readable medium (CRM) 542 storing a computer program (CP) 543 comprising computer readable instructions (CRI) 544. CRM 542 may be a non-transitory computer readable medium, such as, magnetic media (e.g., a hard disk), optical media, memory devices (e.g., random access memory, flash memory), and the like. In some embodiments, the CRI 544 of computer program 543 is configured such that when executed by PC 502, the CRI causes UE 102 to perform steps described herein (e.g., steps described herein with reference to the flow charts). In other embodiments, UE 102 may be configured to perform steps described herein without the need for code. That is, for example, PC 502 may consist merely of one or more ASICs. Hence, the features of the embodiments described herein may be implemented in hardware and/or software.

[0012] Conclusion

[0013] In summary, there are provided embodiments that enable a stationary UE to connect to a serving cell without having to go through ordinary beam management procedures, but rather, based on obtained configuration information, select an RA resource (e.g., preamble) corresponding to a specific (e.g., preferred SSB/CSI-RS) beam in accordance to which the network node may establish an associated downlink beam.

[0014] While various embodiments are described herein, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of this disclosure should not be limited by any of the above-described exemplary embodiments. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.

[0015] Additionally, while the processes described above and illustrated in the drawings are shown as a sequence of steps, this was done solely for the sake of illustration. Accordingly, it is contemplated that some steps may be added, some steps may be omitted, the order of the steps may be re-arranged, and some steps may be performed in parallel.

Claims

CLAIMS:

1. A method (200) performed by a user equipment, UE (102), the method comprising: obtaining (s202) from a network node (104) configuration information identifying a random access, RA, resource; storing (s204) the configuration information; detecting (s206) an RA trigger, wherein the RA trigger is not a beam failure event; and after detecting the RA trigger, using (s208) the stored identified RA resource to perform an RA procedure to establish a logical connection with the network node.

2. The method of claim 1, further comprising: after detecting the RA trigger and before using stored identified RA resource to perform the RA procedure, determining, based on location information, whether or not to use the stored configuration information.

3. The method of claim 2, wherein the location information indicates whether or not the UE is likely within the coverage of a particular beam used by the network node.

4. The method of claim 3, wherein the UE uses the stored identified RA resource to perform the RA procedure as a result of determining, based on the location information, that the UE is likely within the coverage of the particular beam.

5. The method of any one of claims 1-4, wherein the UE does not have a logical connection with the network node at the time the UE detects the RA trigger.

6. The method of claim 5, wherein the UE is in an idle state at the time the UE detects the RA trigger.

7. The method of claim 5 or 6, the UE receives the configuration information in a period of time during which the UE has an active logical connection with the network node.

8. The method of any one of claims 1-7, wherein detecting the RA trigger comprises: detecting a page message addressed to the UE; detecting that the UE needs to forward a received message to a network node; or detecting that at least a certain amount of time has elapsed from a prior point in time.

9. The method of any one of claims 1-8, wherein the configuration information comprises: a preamble identifier, ID, identifying a preamble, a reference signal resource ID identifying a reference signal resource, and/or information identifying Random Access Channel, RACH, occasion.

10. The method of any one of claims 1 -9, wherein the identified RA resource is a preamble, and using the identified RA resource to perform the RA procedure comprises transmitting the preamble to the network node.

11. A method (300) performed by network node (104), the method comprising: associating (s302) a random access, RA, resource with a particular beam; obtaining (s304) information indicating that a particular user equipment, UE (102), over a given period of time, is likely to be within the coverage of the particular beam; and providing (s306) to the UE configuration information identifying the RA resource so that the UE will use the RA resource to perform an RA procedure for establishing a logical connection with the network node.

12. The method of claim 11, wherein the information comprises statistics associated with the particular beam and the particular UE.

13. The method of claim 12, wherein the statistics indicate a degree to which the particular beam was used to communicate with the UE over a particular period of time.

14. The method of claim 11, wherein obtaining the information comprises obtaining the information from a machine learning, ML, model.

15. The method of claim 14, wherein the information obtained from the ML model comprises a preamble identifier, ID, identifying the particular beam.

16. The method of claim 14 or 15, further comprising, prior to obtaining the information from the ML model, obtaining information pertaining to the UE, the information pertaining to the UE comprising: current weather conditions experienced by the UE, service characteristics of services used by, or expected to be used by, the UE, or road traffic information.

17. The method of any one of claims 11-16, further comprising detecting that the UE has used the RA resource to perform the RA procedure; and as a result of the detecting, using the beam with which the RA resource is associated to communicate with the UE.

18. A computer program (543) comprising instructions (544) which when executed by processing circuitry (502) of a UE (102) causes the UE to perform the method of any one of claims 1-10.

19. A computer program (443) comprising instructions (444) which when executed by processing circuitry (402) of a network node (104) causes the network node to perform the method of any one of claims 11-17.

20. A carrier containing the computer program of claim 18 or 19, wherein the carrier is one of an electronic signal, an optical signal, a radio signal, and a computer readable storage medium (442, 542).

21. A user equipment, UE (102), the UE (102) being configured to: obtain from a network node (104) configuration information identifying a random access, RA, resource; store the configuration information; detect an RA trigger, wherein the RA trigger is not a beam failure event; and after detecting the RA trigger, use the stored identified RA resource to perform an RA procedure to establish a logical connection with the network node.

22. The UE of claim 21, wherein the UE is further configured to perform the method of any one of claims 2-10.

23. A user equipment, UE (102), the UE (102) comprising: processing circuitry (502); and a memory (542), the memory containing instructions (544) executable by the processing circuitry, whereby the UE is operative to perform the method of any one of claims 1-10.

24. A network node (104), the network node (104) being configured to: associate a random access, RA, resource with a particular beam; obtain information indicating that a particular user equipment, UE (102), over a given period of time, is likely to be within the coverage of the particular beam; and provide to the UE configuration information identifying the RA resource so that the UE will use the RA resource to perform an RA procedure for establishing a logical connection with the network node.

25. The network node of claim 24, wherein the network node is further configured to perform the method of any one of claims 12-17.

26. A network node (104), the network node (104) comprising: processing circuitry (502); and a memory (542), the memory containing instructions (544) executable by the processing circuitry, whereby the network node is operative to perform the method of any one of claims 11-17.