WO2021086466A1

WO2021086466A1 - Selecting random access preambles

Info

Publication number: WO2021086466A1
Application number: PCT/US2020/044710
Authority: WO
Inventors: Shiangrung YE
Original assignee: Google Llc
Priority date: 2019-10-30
Filing date: 2020-08-03
Publication date: 2021-05-06

Abstract

Techniques at a UE (110) for selecting random access preambles (200, 300, 400) include determining a candidate set of reference signals, from a multiplicity of reference signals generated by a base station (102), based on respective measurements of receive power and/or respective measurements of receive quality. The candidate set may include signals having respective receive power measurements above a receive-power threshold, and/or may include signals having respective receive quality measurements above a receive-quality threshold. When no reference signals meet the receive-power threshold, preference is given to a reference signal associated with dedicated preambles, thereby prioritizing contention-free random access over contention-based random access. In some embodiments, preference is additionally or alternatively given to a reference signal having a greatest receive-quality measurement and/or a greatest receive-power measurement among the candidate set. The UE (110) may provide, to the base station, downlink and/or reference signal characteristic information it observes during and/or upon completing random access procedures.

Description

SELECTING RANDOM ACCESS PREAMBLES

[0001] This disclosure relates to wireless communications and, more particularly, to systems and methods of selecting random access preambles for random access procedures based on dedicated preambles, receive power, and/or receive quality associated with reference signals.

BACKGROUND

[0002] The background description provided within this document is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.

[0003] A base station included in a wireless communication system configures a User Equipment (UE) with a set of non-dedicated preambles associated with a first set of SSBs (Synchronization Signal Blocks) or CSI-RSs (Channel Status Information-Reference Signals), referred to in this disclosure as “SSB/CSTRSs,” and configures the UE with a set of dedicated preambles associated with a second set of SSB/CSTRSs. During a random access procedure, which the UE can initiate during a beam failure recovery or a handover scenario, the UE selects a particular SSB/CSTRS that has a respective RSRP (Reference Signal Received Power) greater than a receive power threshold, and transmits a preamble associated with the selected SSB/CS-RS to the base station via a resource corresponding to the selected SSB/CS-RS, e.g., as part of the random access procedure. Specifically, when the preamble associated with the selected SSB/CSTRS is a non-dedicated preamble, the UE performs a contention-based random access procedure, and when the preamble associated with the selected SSB/CSTRS is a dedicated preamble, the UE performs a contention-free random access procedure.

[0004] When the UE does not find any SSB/CSTRS that has a respective RSRP above the receive power threshold (e.g., all SSB/CS-RSs are of low RSRP), the UE selects any SSB/CSTRS (e.g., any SSB/CSTRS which corresponds to a non-dedicated preamble) and performs the contention-based random access procedure using a resource corresponding to the selected SSB/CSTRS. [0005] However, the technique of selecting any SSB/CSI-RS and performing the contention-based random access procedure when all RSRPs are lower than the threshold suffers from several drawbacks. For example, some SSB/CSI-RSs are associated with both a dedicated preamble and a non-dedicated preamble. If the UE selects such an SSB/CSI-RS during low RSRP situations, the UE performs a contention-based random access procedure even though the selected SSB/CSI-RS and corresponding resources are able to support a contention-free random access procedure. As such, the needlessly performed contention- based random access procedure results in an increase of the load and the probability of collision on the PRACH (Physical Random Access CHannel), as well as results in an increase in the length of time needed to recover from the beam failure or to complete the handover (e.g., an increase in latency). Further, upon completion of a random access procedure after the selection of any SSB/CS-RS when RSRPs are low, the UE may encounter a radio link failure, for example, due to the downlink signal being of insufficient quality when transmitted over all (e.g., too many) of the downlinks being utilized by the base station.

SUMMARY

[0006] In a wireless communication system, such as in a 5G NR or later-generation wireless communication system, a UE begins performing a random access procedure with a base station, which may be a gNB (Next Generation Node B) or other suitable type of base station. Various events may trigger the UE to perform the random access procedure, such as when the UE takes steps to recover from a beam failure or when the UE receives a command to handover to the base station, for example. The UE attempts to select a reference signal (such as an SSB, a CSI-RS, a PSS (Primary Synchronization Signal), a SSS (Secondary Synchronization Signal), etc.) generated by the base station that has a receive power measurement above a pre-defined, receive-power threshold so that the UE may utilize the resource associated with the selected reference signal to perform the random access procedure with the base station. However, when the UE determines that none of the perceived reference signals has a respective receive power above the receive-power threshold, the UE selects a reference signal that is associated with a dedicated preamble, e.g., as configured at the UE by the base station, and initiates the contention-free random access procedure using the resource corresponding to the selected reference signal. Additionally, in some embodiments, during and/or upon completion of a random access procedure (whether contention-based or contention-free), the UE transmits an indication of the downlink beam status and optionally other information indicative of characteristics of the downlink beams to the base station for the base station to utilize in managing its downlink resources.

[0007] These techniques provide significant advantages over the other approaches to performing a random access procedure in the absence of strong downlink SSB/CSTRSs. For example, by prioritizing dedicated preambles and contention-free random access procedures over non-dedicated preambles and contention-based random access procedures, the UE exchanges fewer messages with the base station during random access procedures. Accordingly, the load on the Physical Random Access CHannel (PRACH) decreases. Additionally, the probability of collision on the PRACH decreases, thereby decreasing the utilization of resources needed to mitigate collisions. Moreover, the time required to set up the connection between the UE and the base station (e.g., the latency) is also decreased. Further, because the UE may utilize receive quality as a factor in selecting resources to utilize in random access procedures, the random access procedures themselves may increase in fidelity and become more efficient as well, thereby further reducing latency. Still further, as the UE may transmit downlink characteristic information to the base station, e.g., during and/or upon completion of random access procedures and, in particular, during scenarios in which the receive power of reference signals is low, the base station can utilize this information to make better decisions as to how to utilize its resources among the UEs that it services, thereby increasing the fidelity of connections between the base station and the UEs.

[0008] In an example embodiment, a method in a user equipment device (UE) includes determining, by processing hardware of the UE, that none of a plurality of reference signals generated by a base station and detected by the UE has a respective measurement of receive power greater than a threshold. The method also includes, based on the determination, selecting, from the plurality of reference signals, a reference signal that is associated with a set of dedicated preambles, and initiating, by the processing hardware of the UE, a contention-free random access procedure. The initiation of the contention-free random access procedure includes transmitting a dedicated preamble, of the set of dedicated preambles, to the base station via a resource corresponding to the selected reference signal.

[0009] In an example embodiment, a method in a user equipment (UE) includes determining, by processing hardware of the UE, a plurality of reference signals that are generated by a base station and that have respective measurements of receive power greater than a threshold. The method further includes selecting a reference signal from the plurality of reference signals based on respective measurements of receive quality of the plurality of reference signals. Additionally, the method includes initiating, by the processing hardware of the UE, a random access procedure, where the initiating of the random access procedure includes transmitting a preamble associated with the selected reference signal to the base station via a resource corresponding to the selected reference signal.

[0010] In an example embodiment, a method at a User Equipment (UE) includes determining, by processing hardware of the UE, a candidate set of reference signals from a multiplicity of reference signals generated by a base station, where the determining is based on at least one of respective measurements of receive power or respective measurements of receive quality of the multiplicity of reference signals. The method further includes determining, by the processing hardware, whether or not the candidate set of reference signals includes any reference signals associated with a set of dedicated preambles. When the candidate set of reference signals includes at least one reference signal associated with the set of dedicated preambles, the method includes selecting a reference signal from the at least one reference signal associated with the set of dedicated preambles, and initiating a contention-free random access procedure using a dedicated preamble and a resource associated with the selected reference signal. On the other hand, when the candidate set of reference signals does not include any reference signal associated with the set of dedicated preambles, the method includes selecting, from the candidate set of reference signals, a reference signal associated with a set of non-dedicated preambles, and initiating a contention- based random access procedure using a non-dedicated preamble and a resource associated with the selected reference signal.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. 1 depicts an example wireless communication system in which devices such as base stations and User Equipments (UEs) communicate data, and that supports the selection of random access preambles in accordance with at least some of the principles and techniques disclosed in this document.

[0012] FIG. 2 depicts an example flow diagram of a method for selecting random access preambles for random access procedures based on the receive power of reference signals, in accordance with at least some of the principles and techniques disclosed within this document. [0013] FIG. 3 depicts an example flow diagram of a method for selecting random access preambles for random access procedures based on the receive power and the receive quality of reference signals in accordance with at least some of the principles and techniques disclosed within this document.

[0014] FIG. 4 depicts an example flow diagram of a method for selecting random access preambles for random access procedures based on the receive power, the receive quality, and/or dedicated preambles associated with reference signals, in accordance with at least some of the principles and techniques disclosed within this document.

DETAILED DESCRIPTION

[0015] The systems, methods, and techniques described within this document apply to the selection, by a User Equipment (UE), of a random access preamble for use in a random access procedure based on dedicated preambles, receive power measurements, and/or receive quality measurements corresponding to reference signals observed or detected by the UE. In a wireless communication system, such as in a 5G NR or later-generation wireless communication system, a UE begins performing a random access procedure with a base station, which may be a gNB (Next Generation Node B) or other suitable type of base station. Various events may trigger the UE to perform the random access procedure, such as when the UE takes steps to recover from a beam failure or when the UE receives a command to handover to the base station, for example. The UE selects a reference signal (such as an SSB, a CSI-RS, a PSS (Primary Synchronization Signal), a SSS (Secondary Synchronization Signal), etc.) from among a plurality of reference signals generated by the base station based on one or more criteria, such as whether or not the reference signals are associated with dedicated preambles, the receive power measurements of the reference signals, and/or the receive quality measurements of the reference signals. Subsequently, the UE performs either a contention-free random access procedure or a contention-based random access procedure in accordance with the selected random access preamble. Additionally, in some embodiments, during and/or upon completion of a random access procedure (whether contention-based or contention-free), the UE transmits, to the base station, an indication of one or more receive characteristics of one or more downlink beams and/or reference signals observed by the UE for the base station to utilize in managing its downlink resources.

[0016] FIG. 1 depicts an example wireless communication system 100 in which devices such as base stations and User Equipments (UEs) communicate data, and that supports the selection of random access preambles in accordance with at least some of the principles and techniques disclosed in this document. The wireless communication system 100 includes one or more base stations 102, which are depicted in FIG. 1 by a single base station representation and are discussed within this document using the singular tense for ease of discussion (and not for limitation purposes). The base station 102 supports a Radio Access Network (RAN) of a particular Radio Access Technology, such as NR. In an example configuration, the base station 102 supports an NR RAT and operates as a gNodeB (gNB). The base station 102 communicatively connects to one or more types of core networks (CNs) 105 (e.g., 5GC, EPC, etc.), which in turn communicatively connect to the Internet and/or any number of other networks 108, which may include one or more private and/or public networks 108. Similar to depiction of the base station 102, FIG. 1 depicts the one or more core networks 105 using a single core network representation, and this document discusses the one or more CNs 105 using the singular tense for ease of discussion (and not for limitation purposes).

[0017] A User Equipment (UE) 110, which can be any suitable device capable of wireless communications via one or more types of RANs, can communicatively connect with the wireless communication system 100 via the base station 102. The UE 110 includes processing hardware 112 that can include one or more processors (e.g., CPUs) 115 and one or more non-transitory, tangible, computer-readable memories 118 storing computer-executable instructions that the one or more processors 115 read and/or execute. Particularly, the instructions include preamble selector instructions 120 for selecting random access preambles in accordance with one or more of the methods, principles, and techniques disclosed in this document. The memories 118 can also store other instructions 122, in embodiments. In an example implementation of the UE 110, the one or more processors 115 execute the computer-executable instructions 120, 122 to perform any one or more of the portions of the described methods and/or techniques. In some implementations, the one or more processors 115 execute the computer-executable instructions 120, 122 to operate in conjunction with firmware and/or other portions of the processing hardware 112 to perform any one or more of the portions of the described methods and/or techniques.

[0018] Additionally, the memories 118 can store data that is utilized to perform any one or more of the portions of the methods and/or techniques described within this document. In particular, the memories 118 store preamble configuration data 125 for use in the described methods and/or techniques. The base station 102 or another base station of the system 100 (not shown) may provide the preamble configuration data 125 to the UE 110, for example. Of course, the memories 118 may store other data 128, in embodiments. The UE 110 may utilize the stored data 125, 128 while performing one or more of the portions of the described methods and/or techniques.

[0019] Further, the example processing hardware 112 includes one or more Radio Resource Control (RRC) controllers 130 which are used to communicate Radio Frequency (RF) signals with the system 100 via radios in accordance with one or more different types of RATs supported by the UE 110. The RF signals include payload data that is delivered between the UE 110 and the base station 102.

[0020] Generally, in the wireless communication system 100, the base station 102 provides (e.g., transmits) to the UE 110 a configuration that indicates respective associations of a plurality of reference signals to dedicated and/or non-dedicated random access preambles.

The set of reference signals may be a set of SSBs, a set of CSI-RSs, a set of PSSs, a set of SSSs, or any other suitable type of reference signal which is generated by the base station 102 and is detected or observed by the UE 110. Each reference signal may be associated with only a set of dedicated preambles, with only a set of non-dedicated preambles, or with both the dedicated and non-dedicated sets of preambles. The UE 110 stores the obtained configuration in its memories 118, e.g., as preamble configuration data 125.

[0021] The UE 110 may detect or observe a plurality of reference signals generated by the base station 102, e.g., which may be SSBs, CSI-RSs, PSSs, SSSs, etc. Upon detecting or observing the reference signals, the UE 110 may measure or determine respective receive power and respective receive quality of each of the observed or detected reference signals. Additionally or alternatively, the UE 110 may determine or measure receive power measurements and/or receive quality measurements of observed or detected reference signals continuously, periodically, and/or when triggered to do so by the occurrence of various events, such as when the UE 110 is triggered to perform a random access procedure. The receive power measurements may be, for example, values of a Reference Signal Received Quality (RSRQ) parameter, or some other suitable receive power measurement. The received quality measurements may be, for example, values of a Reference Signal Receive Quality (RSRQ) parameter, values of a Signal-to-Interference-Plus-Noise-Ratio (SINR) parameter, or some other suitable receive quality measurement.

[0022] When the UE 110 is triggered to perform a random access procedure, the UE 110 executes the preamble selector instructions 120 to select a reference signal, from the plurality of reference signals that the UE 110 observes or detects, in accordance with the methods and techniques described within this document. As previously discussed, various events may trigger the UE 110 to perform random access procedures, such as when the UE 110 takes steps to recover from a beam failure, when the UE 110 receives a command to handover to the base station 102, and/or other events. Selection of a reference signal may be based on the received power measurements of the plurality of reference signals, the receive quality measurements of the plurality of reference signals, associations of the reference signals with dedicated preambles, and/or other criteria. In some embodiments, the selection of a reference signal includes determining and/or measuring respective levels of receive power and/or receive quality of the plurality of reference signals. Embodiments of selecting a reference signal are described in more detail in other sections of this document.

[0023] Upon selecting a reference signal, the UE 110 initiates, e.g., via executing the other instructions 122, a random access procedure utilizing a random access preamble and resource (e.g., a RAN resource) that are associated with the selected reference signal. For example, when the selected reference signal is associated with the set of dedicated preambles, the UE 110 initiates a contention-free random access procedure utilizing a dedicated preamble and a resource corresponding to the selected reference signal, and when the selected reference signal is not associated with the set of dedicated preambles, the UE 110 initiates a contention- based random access procedure utilizing a non-dedicated preamble and a resource corresponding to the selected reference signal.

[0024] FIG. 2 depicts an example message flow diagram of a method 200, at a UE, for selecting random access preambles for random access procedures based on the receive power of reference signals, in accordance with at least some of the principles and techniques disclosed within this document. In an example implementation, the UE is the UE 110 of FIG.

1, and UE 110 performs the method 200 by executing the preamble selector instructions 120 and optionally other instructions 122. In some embodiments, at least a portion of the method 200 may be executed in conjunction with at least portions of one or more other methods described within this document, in some embodiments. In some embodiments, the method 200 includes one or more alternate and/or additional actions other than those shown in FIG.

2.

[0025] At a block 202, the method 200 includes determining, by processing hardware of the UE, that none of a plurality of reference signals generated by a base station has a respective measurement of receive power greater than a threshold, e.g., a receive power threshold. That is, the method 200 includes the UE determining that all of the reference signals that are generated by the base station and detected or observed by the UE have receive power levels equal to or lower than their respective receive power threshold. In an embodiment, each of the plurality of reference signals is evaluated against a single (e.g., the same) receive power threshold. In other embodiments, different reference signals may be evaluated against different, respective receive power thresholds. The base station may be one of a plurality of base stations included in a wireless communication system (such as the wireless communication system 100 of FIG. 1), and the receive power threshold(s) may be pre-determined threshold(s), which may be adjustable or configurable. In an example, the base station may have provided the receive power threshold(s) to the UE a priori , e.g., in a configuration.

[0026] At a block 205, the method 200 includes selecting, by the UE from the plurality of reference signals, a reference signal that is associated with a set of dedicated preambles based on the determination of block 202. Generally, any reference signal that is included in the plurality of reference signals and that is associated with dedicated preambles is a candidate for selection at block 205, irrespective of whether the reference signal is or is not associated with non-dedicated preambles. In an example, the base station may have provided indications of respective associations of reference signals with dedicated preambles and/or with non-dedicated preambles a priori, e.g., during configuration of the UE with respect to the base station.

[0027] In an embodiment, block 205 includes first selecting any reference signal, among the plurality of reference signals having respective receive power levels equal to or lower than the receive power threshold, to be a candidate reference signal, and then determining whether or not the candidate reference signal is associated with the set of dedicated preambles. If the candidate reference signal is associated with dedicated preambles, block 205 utilizes the candidate reference signal as the selected reference signal corresponding to the random access procedure. If the candidate reference signal is not associated with dedicated preambles, though, block 205 selects another reference signal, among the plurality of reference signals having respective receive power levels equal to or lower than the receive power threshold, to be a new candidate reference signal, and determines whether or not the new candidate reference signal is associated with dedicated preambles. In this embodiment, block 205 continues in this manner until the UE selects a reference signal associated with dedicated preambles.

[0028] In another embodiment, block 205 includes first determining one or more reference signals, among the plurality of reference signals having respective receive power levels equal to or lower than the receive power threshold that are associated with dedicated preambles. Subsequently, in this embodiment, block 205 selects any reference signal among the reference signals associated with the set of dedicated preambles. Alternatively in this embodiment, when block 205 determines that more than one reference signal among the plurality of reference signals is associated with dedicated preambles, block 205 selects a reference signal that has a largest receive power level or measurement among the more than one reference signal associated with dedicated preambles.

[0029] At a block 208, the method 200 includes initiating, by the processing hardware of the UE, a contention-free random access procedure including transmitting a dedicated preamble, of the set of dedicated preambles, to the base station via a resource (e.g., a RAN resource) corresponding to the selected reference signal.

[0030] In some scenarios (not shown in FIG. 2), subsequent to transmitting the dedicated preamble to the base station, and prior to completing the contention-free random access procedure initiated at block 208, the UE may determine that a new set of reference signals has respective receive power measurements that are above the receive power threshold. The UE may be configured to continuously and/or periodically obtain receive power measurements of observed or detected reference signals. As such, in an example, the UE may determine a new set of one or more reference signals that have respective receive power measurements above the receive power threshold while the UE awaits a response, from the base station, to the dedicated preamble transmitted by the UE at block 208. In another example, the UE detects a failure of the random access procedure initiated at block 208, and the UE may determine the new set of reference signals having respective receive power measurements above the receive power threshold in response to the detected failure. At any rate, in these and other scenarios, the method 200 may include selecting, by the UE, a new reference signal from the new set of reference signals having respective receive power measurements above the receive power threshold, and initiating another contention-free random access procedure that includes transmitting a dedicated preamble to the base station via a resource corresponding to the selected, new reference signal. Accordingly, the method 200 may prioritize reference signals that have respective receive power measurements greater than the receive power threshold over reference signals that have respective receive power measurements less than or equal to the receive power threshold.

[0031] The new set of reference signals may not include any of the plurality of reference signals of block 202, or the new set of reference signals may include some or all of the plurality of reference signals of block 202. In situations in which the new set of reference signals includes the reference signal selected at block 205, e.g., the new set of reference signals includes the “first” reference signal, the method 200 may include determining whether or not a current value of a preamble transmit power corresponding to the UE is less than or equal to a maximum preamble transmit power. The base station may have provided an indication of the maximum preamble transmit power limit to the UE a priori , e.g., during configuration of the UE, for example. When the current value of the preamble transmit power is less than or equal to the maximum preamble transmit power, the method 200 includes selecting the first reference signal to be the new reference signal, e.g., now that the first reference signal has a sufficient receive power measurement. On the other hand, when the current value of the preamble transmit power is greater than the maximum preamble transmit power, the method 200 includes selecting, from the new set of reference signals, a reference signal other than the first reference signal to be the new reference signal. Selecting the new reference signal based on a current value of preamble transmit power corresponding to the UE enables a faster completion of a random access procedure between the UE and the base station (e.g., less latency), at least because the UE does not need (e.g., is not required) to increase preamble transmit power when the UE selects a different reference signal for random access purposes.

[0032] In some embodiments of the method 200 (not shown), sometime after completion of the random access procedure initiated at block 208, the method 200 includes again executing block 202 thereby determining, by the UE, that none of a second plurality of reference signals has a respective receive power above the receive power threshold. The second plurality of reference signals may have been generated by the base station associated with block 208, or the second plurality of reference signals may have been generated by another base station of the wireless communication system. In these embodiments, however, the method 200 includes determining, by the UE, that none of the second plurality of reference signals is associated with dedicated preambles. Accordingly, the method 200 includes selecting, by the UE, one of the second plurality of reference signals and initiating a corresponding contention-based random access procedure, including transmitting a non- dedicated preamble, via a resource corresponding to the selected new reference signal, to the base station that generated the second plurality of reference signals. Selecting the one of the second plurality of reference signals may include selecting any one of the second plurality of reference signals, or selecting the one of the second plurality of reference signals may include selecting a reference signal having a largest receive power measurement among the second plurality of reference signals.

[0033] Returning to FIG. 2, at an optional block 210, the method 200 includes transmitting, by the UE to the base station, information indicative of one or more characteristics of one or more downlink beams and/or reference signals generated by the base station and observed or detected by the UE, e.g., one or more receive characteristics. The receive characteristics of the downlink beams/reference signals may be indicative of observed receive power levels of reference signals, such as a respective measurement of receive power of the selected reference signal, a largest receive power measurement among the plurality of reference signals detected by the UE, respective receive power measurements of more than one of the plurality of reference signals detected by the UE, and/or respective receive power measurements of all reference signals detected by the UE. Additionally or alternatively, the receive characteristics of the downlink beams/reference signals may be indicative of receive quality levels, such as a respective measurement of receive quality of the selected reference signal, a largest quality power measurement among the plurality of reference signals detected by the UE, respective receive quality measurements of more than one of the plurality of reference signals detected by the UE, and/or respective receive quality measurements of all reference signals detected by the UE. Still additionally or alternatively, in some embodiments of block 210, the information indicative of the one or more receive characteristics of the downlink beams/reference signals may correspond to various layers of the Radio Access Network. For example, the information indicative of the one or more receive characteristics may include information indicative of one or more Radio Resource Control or (RRC) measurements, a MAC (Medium Access Control) control element (such as a logical channel identifier), a channel quality of a physical layer, a channel status of a physical layer, and/or the like.

[0034] The UE may transmit the indication(s) of the downlink beam or reference signal characteristic(s) to the base station as desired, e.g., continuously or periodically, upon initiation of a random access procedure, during a random access procedure (e.g., after initiation and prior to completion), upon completion of a random access procedure, etc. The base station may utilize the received downlink and/or reference signal characteristic information to manage the connection of the UE with the wireless communication system.

For example, the base station may instruct the UE to handover to another base station based on the received characteristic information. As such, block 210 allows for greater fidelity of the connection between the UE and the wireless communication system.

[0035] FIG. 3 depicts an example message flow diagram of a method 300, at a UE, for selecting random access preambles for random access procedures based on the receive power and the receive quality of reference signals in accordance with at least some of the principles and techniques disclosed within this document. In an example implementation, the UE is the UE 110 of FIG. 1, and UE 110 performs the method 300 by executing the preamble selector instructions 120 and optionally other instructions 122. In some embodiments, at least a portion of the method 300 may be executed in conjunction with at least portions of one or more other methods described within this document, in some embodiments. For example, the block 210 of the method 300 may execute in conjunction with the method 300. In some embodiments, the method 300 includes one or more alternate and/or additional actions other than those shown in FIG. 3.

[0036] At a block 302, the method 300 includes determining, by processing hardware of the UE, a plurality of reference signals generated by a base station and observed or detected by the UE that have respective measurements of receive power greater than a threshold, e.g., a receive power threshold. That is, the method 300 includes the UE determining that all of the reference signals that are generated by the base station and detected or observed by the UE have receive power levels equal to or lower than their respective receive power threshold. In an embodiment, each of the plurality of reference signals is evaluated against a single (e.g., a same) receive power threshold. In other embodiments, different reference signals may be evaluated against different, respective receive power thresholds. The base station may be one of a plurality of base stations included in a wireless communication system (such as the wireless communication system 100 of FIG. 1), and the receive power threshold(s) may be pre-determined threshold(s), which may be adjustable or configurable. In an example, the base station may have provided the receive power threshold(s) to the UE a priori , e.g., in a configuration. In some implementations, the receive power threshold(s) associated with the method 300 are the receive power threshold(s) associated with the method 200. [0037] At a block 305, the method 300 includes selecting a reference signal from the plurality of reference signals having respective receive power measurements greater than the receive power threshold, where the selecting is based on receive quality measurements of the reference signals. In an embodiment, block 305 may include selecting any reference signal from the output of block 302 that has a respective receive quality measurement greater than a threshold, e.g., a receive quality threshold. The receive quality threshold may be a pre determined threshold, and may be adjustable or configurable. In an example, the base station may have provided the receive quality threshold to the UE a priori , e.g., during configuration.

[0038] Additionally or alternatively, block 305 may include selecting the reference signal that has a largest respective receive quality measurement among a set of candidate reference signals. The candidate set of reference signals may be the entirety of the plurality of reference signals having respective receive power measurements greater than the receive power threshold, the candidate set of reference signals may be a subset of the plurality of reference signals having respective receive power measurements greater than the receive power threshold, or the candidate set of reference signals may be a subset of the plurality of reference signals determined based on a combination of criteria. For example, the subset may include only those reference signals that have respective receive power measurements greater than receive power threshold and that have respective receive quality measurements greater than the receive quality threshold.

[0039] Indeed, in an embodiment, block 305 includes selecting the reference signal from the plurality of reference signals further based on the respective receive power measurements of the plurality of reference signals. For example, block 305 may select a reference signal that has a largest receive power measurement among a set of candidate reference signals that have been screened or otherwise selected from the plurality of reference signals based on their respective receive quality measurements, e.g., in a manner as described above.

[0040] In an embodiment, block 305 includes selecting the reference signal from the plurality of reference signals further based respective associations of the plurality of reference signals with dedicated preambles. For example, block 305 may select a reference signal, from a set of candidate reference signals that have been screened or otherwise selected from the plurality of reference signals based on their respective receive quality measurements, that is associated with a set of dedicated preambles, irrespective of whether or not the reference signal is also associated with the set of non-dedicated preambles. In an example, the base station may have provided indications of respective associations of reference signals with dedicated preambles and/or with non-dedicated preambles a priori, e.g., during configuration of the UE with respect to the base station.

[0041] At a block 308, the method 300 includes initiating, by the processing hardware of the UE, a random access procedure including transmitting a preamble associated with the selected reference signal to the base station via a resource (e.g., a RAN resource) corresponding to the selected reference signal. For example, when the selected reference signal is associated with the set of dedicated preambles, the UE initiates a contention-free random access procedure utilizing a dedicated preamble and a resource corresponding to the selected reference signal, and when the selected reference signal is not associated with the set of dedicated preambles, the UE initiates a contention-based random access procedure utilizing a non-dedicated preamble and a resource corresponding to the selected reference signal.

[0042] FIG. 4 depicts an example message flow diagram of a method 400, at a UE, for selecting random access preambles for random access procedures based on receive power, receive quality, and/or dedicated preambles associated with detected or observed reference signals generated by a base station, in accordance with at least some of the principles and techniques disclosed within this document. In an example implementation, the UE is the UE 110 of FIG. 1, and UE 110 performs the method 400 by executing the preamble selector instructions 120 and optionally other instructions 122. In some embodiments, at least a portion of the method 400 may be executed in conjunction with at least portions of one or more other methods described within this document. For example, the method 400 may be executed in conjunction with block 210 of the method 200. In some embodiments, the method 400 includes one or more alternate and/or additional actions other than those shown in FIG. 4. For ease of discussion, and not for limitation purposes, the method 400 is discussed with simultaneous reference to the wireless communication system 100 of FIG. 1, although the method 400 may execute in other wireless communication systems.

[0043] At a block 402, the method 400 may include determining, by processing hardware 112 of a UE 110, a candidate set of reference signals from a multiplicity of reference signals that are generated by a base station 102 and detected or observed by the UE 110, where the determining 402 is based on respective measurements of receive power and/or respective measurements of receive quality of the detected or observed multiplicity of reference signals. The base station 102 may be one of a plurality of base stations included in a wireless communication system, such as the wireless communication system 100 of FIG. 1.

[0044] As illustrated in FIG. 4, determining 402 the candidate set of reference signals includes determining whether or not any reference signals of the multiplicity of reference signals has a respective receive quality measurement greater than a first threshold (block 405). The first threshold may be, for example, the receive quality threshold of FIG. 3, or may be another pre-defined receive quality threshold. The receive quality threshold may be adjustable or configurable. In an example, the base station 102 may have provided the receive quality threshold to the UE 110 a priori , e.g., during configuration of the UE 110 by the base station 102, and the UE 110 may have stored the receive quality threshold in its memories 118, e.g., as other data 128.

[0045] At block 405, when the method 400 determines that at least some of the multiplicity of reference signals have respective receive quality measurements greater than the first threshold (e.g., the “yes” leg of block 405), the method 400 includes determining the candidate reference signals to be the set of reference signals, of the multiplicity of reference signals, having respective receive quality measurements greater than the first threshold (block 408). On the other hand, when, at block 405, the method 400 determines that none of the multiplicity of reference signals has a respective receive quality measurement greater than the first threshold (e.g., the “no” leg of block 405), the method 400 proceeds to block 410.

[0046] At block 410, the method 400 includes determining, by the processing hardware 112 of the UE 110, whether or not any reference signals of the observed or detected multiplicity of reference signals has a respective receive power measurement greater than a second threshold. The second threshold may be, for example, the receive power threshold of FIGS. 2 and 3, or may be another predefined receive power threshold. In an example, the base station 102 may have provided the receive power threshold to the UE a priori , e.g., in a configuration, and the UE 110 may have stored the receive power threshold in its memories 118, e.g., as other data 128. When, at block 410, the method 400 determines that at least some of the multiplicity of reference signals have respective receive power measurements greater than the second threshold (e.g., the “yes” leg of block 410), the method 400 includes determining the candidate reference signals to be the set of reference signals, of the multiplicity of reference signals, having respective receive power measurements greater than the second threshold (block 412). On the other hand, when, at block 410, the method 400 determines that none of the multiplicity of reference signals has a respective receive power measurement greater than the second threshold (e.g., the “no” leg of block 410), the method 400 includes determining the candidate reference signals to be the entirety of the observed or detected multiplicity of reference signals having both respective receive quality measurements below the receive quality threshold and respective receive power measurements below the receive power threshold (block 415).

[0047] Generally, the candidate set of reference signals includes one or more of the multiplicity of reference signals that are observed or detected by the UE 110. In some scenarios, the candidate set of reference signals includes only one reference signal of the multiplicity of reference signals. In some scenarios, the candidate set of reference signals includes more than one reference signal of the multiplicity of reference signals.

[0048] Upon determining 402 the candidate set of reference signals, the method 400 includes determining, by the processing hardware 112 of the UE 110, whether or not any of the candidate set of reference signals is associated with the set of dedicated preambles (block 418). Indications of associations of reference signals to the set of dedicated preambles and/or to a set of non-dedicated set of preambles may have been provided a priori to the UE 110, e.g., by the base station 102 or by another base station of the wireless communication system 100, and the UE 110 may have stored indications of the associations in its memories 118, e.g., as preamble configuration data 125. At block 418, when the candidate set of reference signals includes at least one candidate reference signal associated with the set of dedicated preambles (e.g., the “yes” leg of block 418), the method 400 includes selecting a reference signal from the at least one candidate reference signal associated with the set of dedicated preambles (block 420), and initiating a contention-free random access procedure using a dedicated preamble and a resource (e.g., a RAN resource) associated with the selected reference signal (block 422). On the other hand, when the candidate set of reference signals does not include any reference signal associated with the set of dedicated preambles (e.g., the “no” leg of block 418), the method 400 includes selecting, from the candidate set of reference signals, a reference signal associated with a set of non-dedicated preambles (block 425), and initiating a contention-based random access procedure using a non-dedicated preamble and a resource (e.g., a RAN resource) associated with the selected reference signal (block 428). [0049] In some embodiments, selecting 420 the reference signal from the at least one candidate reference signal associated with the set of dedicated preambles includes selecting any candidate reference signal from the at least one candidate reference signal. In some embodiments, selecting 420 the reference signal from the at least one candidate reference signal associated with the set of dedicated preambles includes selecting a candidate reference signal having a largest respective receive quality power measurement, a largest receive power measurement among the at least one candidate reference signal associated with the set of dedicated preambles, and/or other criteria.

[0050] In some embodiments, selecting 425 the reference signal from the set of candidate reference signals that are not associated with set of dedicated preambles includes selecting any candidate reference signal from the set of candidate reference signals. In some embodiments, selecting 420 the reference signal from the set of candidate reference signals includes selecting a candidate reference signal having a largest respective receive quality power measurement, a largest receive power measurement among the set of candidate reference signals, and/or other criteria.

[0051] FIG. 4 depicts only one of many possible embodiments of the method 400. For example, in some embodiments (not shown), the method 400 omits blocks 405 and 408. In some embodiments, the method 400 operates in conjunction with embodiments of the method 200 of FIG. 2. For example, the method 400 may include determining that none of the multiplicity of reference signals generated by the base station 102 and observed or detected by the UE 110 has a respective receive power measurement above the receive power threshold (e.g., the “no” leg of block 410), and determining that at least one candidate reference signal is associated with dedicated preambles (e.g., the “yes” leg of block 418). In this example, the method 400 may execute blocks 420 and 422 in conjunction with one or more blocks of embodiments of the method 200.

[0052] In some embodiments, the method 400 operates in conjunction with embodiments of the method 300 of FIG. 3. For example, the method 400 may include determining that two or more reference signals, from the multiplicity of reference signals generated by the base station 102 and observed or detected by the UE 110, have respective receive power measurements greater than the receive power threshold (e.g., the “yes” leg of block 410), and the method 400 may execute at least some of blocks 412-428 in conjunction with one or more blocks of embodiments of the method 300. [0053] Accordingly, as demonstrated above, the methods and techniques disclosed within this document provide significant advantages over known techniques for performing random access preamble selection. For example, by prioritizing dedicated preambles and contention- free random access procedures over non-dedicated preambles and contention-based random access procedures, a UE exchanges fewer messages with a base station during random access procedures in comparison to known preamble selection techniques. Accordingly, the load on the Physical Random Access CHannel (PRACH) decreases. Additionally, the probability of collision on the PRACH decreases, thereby decreasing the utilization of RAN and other resources needed to mitigate collisions. Moreover, the time required to set up the connection between the UE and the base station (e.g., the latency) is also decreased in comparison with known preamble selection techniques and resulting random access procedures. Further, because the UE may utilize receive quality as a factor in selecting resources to utilize in random access procedures, the random access procedures themselves may increase in fidelity and become more efficient over known random access procedures as well, thereby further reducing latency. Still further, as the UE may transmit downlink characteristic information (e.g., receive characteristic information) to the base station, e.g., during and/or upon completion of random access procedures and, in particular, during scenarios in which the receive power of reference signals is low, the base station can utilize this information to make better decisions as to how to utilize its resources among the UEs that it services, thereby increasing the fidelity of connections between the base station and the UEs.

[0054] The following additional considerations apply to the foregoing discussion.

[0055] A user device or User Equipment (UE) in which the techniques of this disclosure can be implemented (e.g., the UE 110) can be any suitable device capable of wireless communications such as a smartphone, a tablet computer, a laptop computer, a mobile gaming console, a point-of-sale (POS) terminal, a health monitoring device, a drone, a camera, a media-streaming dongle or another personal media device, a wearable device such as a smartwatch, a wireless hotspot, a femtocell, or a broadband router. Further, the user device in some cases may be embedded in an electronic system such as the head unit of a vehicle or an advanced driver assistance system (ADAS). Still further, the user device can operate as an intemet-of-things (IoT) device or a mobile-internet device (MID). Depending on the type, the user device can include one or more general-purpose processors, a computer- readable memory, a user interface, one or more network interfaces, one or more sensors, etc. [0056] Certain embodiments are described in this disclosure as including logic or a number of components or modules. Modules may can be software modules (e.g., code stored on non- transitory machine-readable medium) or hardware modules. A hardware module is a tangible unit capable of performing certain operations and may be configured or arranged in a certain manner. A hardware module can include dedicated circuitry or logic that is permanently configured (e.g., as a special-purpose processor, such as a field programmable gate array (FPGA) or an application- specific integrated circuit (ASIC)) to perform certain operations. A hardware module may also include programmable logic or circuitry (e.g., as encompassed within a general-purpose processor or other programmable processor) that is temporarily configured by software to perform certain operations. The decision to implement a hardware module in dedicated and permanently configured circuitry, or in temporarily configured circuitry (e.g., configured by software) may be driven by cost and time considerations.

[0057] When implemented in software, the techniques can be provided as part of the operating system, a library used by multiple applications, a particular software application, etc. The software can be executed by one or more general-purpose processors or one or more special-purpose processors.

[0058] Upon reading this disclosure, those of skill in the art will appreciate still additional alternative structural and functional designs for enhancing the handling of user equipment in a radio resource control inactive state through the principles disclosed in this disclosure.

Thus, while this document illustrates and describes particular embodiments and applications, the disclosed embodiments are not limited to the precise construction and components disclosed. Various modifications, changes and variations, which will be apparent to those of ordinary skill in the art, may be made in the disclosed arrangement, operation and details of the method, and apparatus without departing from the spirit and scope defined in the appended claims.

Claims

What is claimed is:

1. A method in a user equipment device (UE), the method comprising: determining, by processing hardware of the UE, that none of a plurality of reference signals generated by a base station has a respective measurement of receive power greater than a threshold; selecting, from the plurality of reference signals based on the determination, a reference signal that is associated with a set of dedicated preambles; initiating, by the processing hardware, a contention-free random access procedure including transmitting a dedicated preamble, of the set of dedicated preambles, to the base station via a resource corresponding to the selected reference signal.

2. The method of claim 1, wherein the selected reference signal is associated with both the set of dedicated preambles and a set of non-dedicated preambles.

3. The method of claim 2, further comprising: receiving, by the processing hardware from the base station, a configuration indicating the set of non-dedicated preambles associated with a first set of reference signals included in the plurality of reference signals and the set of dedicated preambles associated with a second set of reference signals included in the plurality of reference signals, the first set of reference signals and the second set of reference signals being intersecting sets, and the intersection includes the selected reference signal.

4. The method of any one of the preceding claims, wherein the plurality of reference signals includes: a plurality of SSBs (Synchronization Signal Blocks); a plurality of CSI-RSs (Channel Status Information-Reference Signals); a plurality of PSSs (Primary Synchronization Signals); a plurality of SSSs (Secondary Synchronization Signals); or a plurality of another type of reference signal generated by the base station.

5. The method of any one of the preceding claims, further comprising: detecting, by the processing hardware of the UE, an occurrence of a beam failure; and determining the respective measurements of receive power of the plurality of reference signals in response to the detection of the occurrence.

6. The method of any one of the preceding claims, further comprising: receiving, by the processing hardware from the base station, an instruction to perform a handover; and determining the respective measurements of receive power of the plurality of reference signals in response to the received instruction.

7. The method of any one of the preceding claims, further comprising, subsequent to transmitting the dedicated preamble to the base station and prior to completing the contention-free random access procedure: selecting, by the processing hardware, a new reference signal from a new set of reference signals having respective measurements of receive power greater than the threshold; and initiating, by the processing hardware, a second contention-free random access procedure including transmitting, to the base station, a second dedicated preamble, of the set of dedicated preambles, via a resource corresponding to the new reference signal.

8. The method of claim 7, wherein: the selected reference signal is a first reference signal; subsequent to the transmitting of the dedicated preamble corresponding to the first reference signal to the base station, the new set of reference signals includes the first reference signal; selecting the new reference signal from the new set of reference signals comprises selecting the first reference signal to be the new reference signal when a current value of a preamble transmit power corresponding to the UE is less than or equal to a maximum preamble transmit power; and selecting the new reference signal from the new set of reference signals comprises selecting, from the new set of reference signals, a reference signal other than the first reference signal when the current value of the preamble transmit power corresponding to the UE is greater than the maximum preamble transmit power.

9. The method of claim 8, further comprising receiving, by the processing hardware of the UE from the base station, a value of the maximum preamble transmit power.

10. The method of any one of claims 7-9, further comprising determining that each reference signal of the new set of reference signals has a respective measurement of receive power greater than the threshold while the UE awaits a response, from the base station, to the transmission of the dedicated preamble.

11. The method of any one of claims 7-10, wherein the method further comprises, subsequent to transmitting the dedicated preamble to the base station and prior to completing the contention-free random access procedure: detecting, by the processing hardware of the UE, a failure of the contention-free random access procedure; and selecting the new reference signal from the new set of reference signals is in response to the detection of the failure.

12. The method of any one of the preceding claims, further comprising transmitting, by the UE to the base station, information indicative of a receive characteristic of one or more downlink beams generated by the base station.

13. The method of claim 12, wherein transmitting the information indicative of the receive characteristic of the one or more downlink beams generated by the base station comprises transmitting an indication of the respective measurement of receive power corresponding to the selected reference signal.

14. The method of any one of claims 12-13, wherein transmitting the information indicative of the receive characteristic of the one or more downlink beams generated by the base station comprises transmitting an indication of a largest measurement of receive power among the respective measurements of receive power of the plurality of reference signals.

15. The method of any one of claims 12-14, wherein transmitting the information indicative of the receive characteristic of the one or more downlink beams generated by the base station comprises transmitting respective indications of respective measurements of receive power of more than one reference signal included in the plurality of reference signals.

16. The method of any one of claims 12-15, wherein transmitting the information indicative of the receive characteristic of the one or more downlink beams generated by the base station occurs after a respective initiation of and prior to a respective completion of each of one or more random access procedures.

17. The method of the preceding claim, wherein transmitting the information indicative of the receive characteristic of the one or more downlink beams generated by the base station after the respective initiation of and prior to the respective completion of each of one or more random access procedures occurs after an initiation of and prior to a completion of the contention-free access procedure corresponding to the selected reference signal.

18. The method of any one of claims 12-15, wherein transmitting the information indicative of the receive characteristic of the one or more downlink beams generated by the base station occurs upon a completion of the contention-free random access procedure corresponding to the selected reference signal.

19. The method of any one of claims 12-18, wherein transmitting the information indicative of the receive characteristic of the one or more downlink beams generated by the base station comprises transmitting information indicative of one or more Radio Resource Controller (RRC) measurements.

20. The method of any one of claims 12-19 wherein transmitting the information indicative of the receive characteristic of the one or more downlink beams generated by the base station comprises transmitting a MAC (Medium Access Control) control element, the MAC control element including a logical channel identifier.

21. The method of any one of claims 12-20, wherein transmitting the information indicative of the receive characteristic of the one or more downlink beams generated by the base station comprises transmitting information corresponding to at least one of a channel quality or a channel status of a physical layer.

22. The method of any one of claims 12-21, further comprising, subsequent to transmitting the information indicative of the receive characteristic of one or more downlink beams generated by the base station, receiving, by the processing hardware of the UE from the base station, an instruction to perform a handover.

23. The method of any one of the preceding claims, wherein selecting the reference signal associated with the set of dedicated preambles comprises: selecting any reference signal from the plurality of reference signals; determining an existence of an association between the selected, any reference signal and the set of dedicated preambles; and determining the selected, any reference signal to be the selected, reference signal in response to the determined existence of the association.

24. The method of any one of claims 1-22, wherein: at least two reference signals of the plurality of reference signals are associated with the set of dedicated preambles; and selecting the reference signal associated with the set of dedicated preambles from the plurality of reference signals comprises selecting, from the at least two reference signals, a reference signal having a largest respective measurement of receive power among the at least two reference signals.

25. The method of any one of the preceding claims, further comprising: determining, by the processing hardware of the UE, that none of a second plurality of reference signals generated by the first base station or by a second base station has a respective measurement of receive power greater than the threshold, and that none of the second plurality of reference signals has a respective association with a corresponding set of dedicated preambles; selecting, by the processing hardware, one of the second plurality of reference signals in response to the determination corresponding to the second plurality of reference signals; and initiating, by the processing hardware, a contention-based random access procedure including transmitting a non-dedicated preamble, of a corresponding set of non-dedicated preambles, to the first or the second base station via a resource corresponding to the selected one of the second plurality of reference signals.

26. The method of claim 25, wherein selecting the one of the second plurality of reference signals comprises selecting a reference signal that has a largest measurement of receive power among the respective measurements of receive power of the second plurality of reference signals.

27. A method in a user equipment (UE), the method comprising: determining, by processing hardware of the UE, a plurality of reference signals generated by a base station that have respective measurements of receive power greater than a threshold; selecting a reference signal from the plurality of reference signals based on respective measurements of receive quality of the plurality of reference signals; initiating, by the processing hardware of the UE, a random access procedure including transmitting a preamble associated with the selected reference signal to the base station via a resource corresponding to the selected reference signal.

28. The method of claim 27, wherein selecting the reference signal from the plurality of reference signals based on the respective measurements of receive quality comprises selecting, from the plurality of reference signals, any reference signal having a respective measurement of receive quality greater than a receive quality threshold.

29. The method of any one of claims 27-28, wherein selecting the reference signal from the plurality of reference signals based on the respective measurements of receive quality comprises selecting, from the plurality of reference signals, a reference signal having a largest respective measurement of receive quality among the plurality of reference signals.

30. The method of any one of claims 27-29, wherein selecting the reference signal from the plurality of reference signals further comprises selecting, from the plurality of reference signals, a reference signal having a largest respective measurement of receive power among the plurality of reference signals.

31. The method of any one of claims 27-30, wherein: the respective measurements of receive power correspond to respective values of a Reference Signal Receive Power (RSRP) parameter; and the respective measurements of receive quality correspond to at least one of: respective values of a Reference Signal Receive Quality (RSRQ) parameter, or respective values of a Signal-to-Interference-Plus-Noise-Ratio (SINR) parameter.

32. The method of any one of claims 27-31, wherein the plurality of reference signals includes: a plurality of SSBs (Synchronization Signal Blocks); a plurality of CSI-RSs (Channel Status Information-Reference Signals); a plurality of PSSs (Primary Synchronization Signals); a plurality of SSSs (Secondary Synchronization Signals); or a plurality of another type of reference signal generated by the base station.

33. The method of any one of claims 27-32, wherein the base station is a gNb.

34. The method of any one of claims 27-33, wherein: the method further comprises receiving, via the processing hardware of the UE from the base station, a configuration indicating a set of non-dedicated preambles associated with a first set of reference signals and a set of dedicated preambles associated with a second set of reference signals; and transmitting the preamble associated with the selected reference signal comprises transmitting a dedicated preamble of the set of dedicated preambles or a non-dedicated preamble of the set of non-dedicated preambles.

35. The method of claim 34, wherein: the plurality of reference signals includes at least one reference signal of the second set of reference signals associated with the set of dedicated preambles; selecting the reference signal from the plurality of reference signals comprises selecting the reference signal from the at least one reference signal of the second set of reference signals; and initiating the random access procedure including transmitting the preamble associated with the selected reference signal comprises initiating a contention-free random access procedure including transmitting the dedicated preamble of the set of dedicated preambles.

36. The method of claim 34, wherein: the plurality of reference signals does not include any reference signal of the second set of reference signals associated with the set of dedicated preambles: selecting the reference signal comprises selecting the reference signal from the first set of reference signals associated with the set of non-dedicated preambles; and initiating the random access procedure including transmitting the preamble associated with the selected reference signal comprises initiating a contention-based random access procedure including transmitting the non-dedicated preamble of the set of non-dedicated preambles.

37. A method at a User Equipment device (UE), the method comprising: determining, by processing hardware of the UE, a candidate set of reference signals from a multiplicity of reference signals generated by a base station, the determining based on at least one of respective measurements of receive power or respective measurements of receive quality of the multiplicity of reference signals; determining, by the processing hardware, whether or not the candidate set of reference signals includes any reference signals associated with a set of dedicated preambles; when the candidate set of reference signals includes at least one reference signal associated with the set of dedicated preambles, selecting a reference signal from the at least one reference signal associated with the set of dedicated preambles, and initiating a contention-free random access procedure using a dedicated preamble and a resource associated with the selected reference signal; and when the candidate set of reference signals does not include any reference signal associated with the set of dedicated preambles, selecting, from the candidate set of reference signals, a reference signal associated with a set of non-dedicated preambles, and initiating a contention-based random access procedure using a non-dedicated preamble and a resource associated with the selected reference signal.

38. The method of claim 37, wherein determining the candidate set of reference signals from the multiplicity of reference signals comprises: determining a set of reference signals, of the multiplicity of reference signals, having respective measurements of receive quality greater than a receive quality threshold to be the candidate set of reference signals.

39. The method of the preceding claim, wherein selecting the reference signal from the candidate set of reference signals comprises selecting a reference signal having a largest respective measurement of receive quality among the candidate set of reference signals.

40. The method of claim 37, wherein determining the candidate set of reference signals from the multiplicity of reference signals comprises: first determining that none of the multiplicity of reference signals has a respective measurement of receive quality greater than a receive quality threshold; and in response to the first determination, determining a set of reference signals, of the multiplicity of reference signals, having respective measurements of receive power greater than a receive power threshold to be the candidate set of reference signals.

41. The method of the preceding claim, wherein selecting the reference signal from the candidate set of reference signals comprises selecting a reference signal having a largest respective measurement of receive power among the candidate set of reference signals.

42. The method of claim 37, wherein determining the candidate set of reference signals from the multiplicity of reference signals comprises: first determining that none of the multiplicity of reference signals has a respective measurement of receive quality greater than a receive quality threshold and that none of the multiplicity of reference signals has a respective measurement of receive power greater than a receive power threshold; and in response to the first determination, determining the multiplicity of reference signals to be the candidate set of reference signals.

43. The method of any one of claims 37-42, wherein the candidate set of reference signals includes only one reference signal.

44. The method of any one of claims 37-43, wherein the base station is a gNb.

45. The method of any one of claims 37-44, wherein the multiplicity of reference signals includes: a multiplicity of SSBs (Synchronization Signal Blocks); a multiplicity of CSI-RSs (Channel Status Information-Reference Signals); a multiplicity of PSSs (Primary Synchronization Signals); a multiplicity of SSSs (Secondary Synchronization Signals); or a multiplicity of another type of reference signal generated by the base station.

46. The method of any one of claims 37-45, wherein: the respective measurements of receive power correspond to respective values of a Reference Signal Receive Power (RSRP) parameter; and the respective measurements of receive quality correspond to at least one of: respective values of a Reference Signal Receive Quality (RSRQ) parameter, or respective values of a Signal-to-Interference-Plus-Noise-Ratio (SINR) parameter.

47. The method of any one of claims 37-46, further comprising receiving, via the processing hardware of the UE from the base station, a configuration indicating a set of non-dedicated preambles associated with a first set of reference signals and a set of dedicated preambles associated with a second set of reference signals; and wherein selecting the reference signal from the candidate set of reference signals includes selecting the reference signal from the candidate set of reference signals based on the configuration.

48. The method of the preceding claim, wherein the first set of reference signals intersects with the second set of reference signals.

49. The method of claim 37, wherein: determining the candidate set of reference signals from the multiplicity of reference signals comprises determining that none of the multiplicity of reference signals has a respective measurement of receive power greater than a receive power threshold and, in response, determining the multiplicity of reference signals to be the candidate set of reference signals; the method includes determining that the candidate set of reference signals includes at least one reference signal associated with the set of dedicated preambles; and the method comprises at least a portion of the method of any one of claims 1-26, wherein the candidate set of reference signals is the plurality of reference signals of the method of any one of claims 1-26.

50. The method of claim 37, wherein: determining the candidate set of reference signals from the multiplicity of reference signals comprises determining two or more reference signals, from the multiplicity of reference signals, having respective measurements of receive power greater than a receive power threshold and, in response, determining the two or more reference signals to be the candidate set of reference signals; the method comprises at least a portion of the method of any one of claims 27-36, wherein the candidate set of reference signals is the plurality of reference signals of any one of claims 27-36.

51. A User Equipment (UE) configured to perform the method of any one of claims 1-50.