Flexible association of preamble sets to synchronization signals

Abstract

Example embodiments of the present disclosure are directed to flexible association of preamble sets to synchronization signals. A method comprises receiving, from a second apparatus, information for associating a plurality of synchronization signals with a plurality of preamble sets, wherein a preamble set comprises at least one preamble, and the received information comprises at least one indicator indicating at least one of: a number of synchronization signals associated with a preamble set of the plurality of preamble sets, or a set of synchronization signals associated with a preamble set of the plurality of preamble sets; selecting a preamble set from the plurality of preamble sets based on the received information and a synchronization signal selected by the first apparatus; and transmitting, to the second apparatus, a random access preamble in the selected preamble set.

Description

FLEXIBLE ASSOCIATION OF PREAMBLE SETS TO SYNCHRONIZATION SIGNALSRELATED APPLICATION

[0001] This application claims priority to IN provisional Application No. 202441059991 filed August 8, 2024, which is incorporated herein by reference in its entirety.FIELD

[0002] Various example embodiments of the present disclosure generally relate to the field of telecommunication and in particular, to methods, devices, apparatuses and computer readable storage medium for flexible association of preamble sets to synchronization signals.BACKGROUND

[0003] In a wireless communication network, a user equipment (UE) may perform a random access (RA) procedure to establish a connection to a network. The UE may need to select one from multiple Random Access Channel (RACH) occasions to initiate the access process procedure. In another aspect, a mapping relation between Synchronization Signal (SS) and physical broadcast channel (PBCH) Blocks (SSBs) and ROs is defined, allowing the gNB to figure out which Tx beamforming UE prefers by detecting which RO and which PRACH preamble a UE uses. This capability enables the network to respond to the UE accordingly.SUMMARY

[0004] In a first aspect of the present disclosure, there is provided a first apparatus. The first apparatus comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first apparatus at least to: receive, from a second apparatus, information for associating a plurality of synchronization signals with a plurality of preamble sets, wherein a preamble set comprises at least one preamble, and the received information comprises at least one indicator indicating at least one of: a number of synchronization signals associated with a preamble set of the plurality of preamble sets, or a set of synchronization signals associated with a preamble set of the plurality of preamble sets; select a preamble setfrom the plurality of preamble sets based on the received information and a synchronization signal selected by the first apparatus; and transmit, to the second apparatus, a random access preamble in the selected preamble set.

[0005] In a second aspect of the present disclosure, there is provided a second apparatus. The second apparatus comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second apparatus at least to: transmit, to a first apparatus, information at least for associating a plurality of synchronization signals with a plurality of preamble sets, wherein a preamble set comprises at least one preamble, and the transmitted information comprises at least one indicator indicating at least one of: a number of synchronization signals associated with a preamble set of the plurality of preamble sets, or a set of synchronization signals associated with a preamble set of the plurality of preamble sets; and receive a random access preamble from the first apparatus.

[0006] In a third aspect of the present disclosure, there is provided a method. The method comprises: receiving, at a first apparatus from a second apparatus, information for associating a plurality of synchronization signals with a plurality of preamble sets, wherein a preamble set comprises at least one preamble, and the received information comprises at least one indicator indicating at least one of: a number of synchronization signals associated with a preamble set of the plurality of preamble sets, or a set of synchronization signals associated with a preamble set of the plurality of preamble sets; selecting a preamble set from the plurality of preamble sets based on the received information and a synchronization signal selected by the first apparatus; and transmitting, to the second apparatus, a random access preamble in the selected preamble set.

[0007] In a fourth aspect of the present disclosure, there is provided a method. The method comprises: transmitting, at a second apparatus to a first apparatus, information at least for associating a plurality of synchronization signals with a plurality of preamble sets, wherein a preamble set comprises at least one preamble, and the transmitted information comprises at least one indicator indicating at least one of: a number of synchronization signals associated with a preamble set of the plurality of preamble sets, or a set of synchronization signals associated with a preamble set of the plurality of preamble sets; and receiving a random access preamble from the first apparatus.

[0008] In a fifth aspect of the present disclosure, there is provided a first apparatus.The first apparatus comprises means for receiving, from a second apparatus, information for associating a plurality of synchronization signals with a plurality of preamble sets, wherein a preamble set comprises at least one preamble, and the received information comprises at least one indicator indicating at least one of: means for a number of synchronization signals associated with a preamble set of the plurality of preamble sets, or means for a set of synchronization signals associated with a preamble set of the plurality of preamble sets; means for selecting a preamble set from the plurality of preamble sets based on the received information and a synchronization signal selected by the first apparatus; and means for transmitting, to the second apparatus, a random access preamble in the selected preamble set.

[0009] In a sixth aspect of the present disclosure, there is provided a second apparatus. The second apparatus comprises means for transmitting, to a first apparatus, information at least for associating a plurality of synchronization signals with a plurality of preamble sets, wherein a preamble set comprises at least one preamble, and the transmitted information comprises at least one indicator indicating at least one of: means for a number of synchronization signals associated with a preamble set of the plurality of preamble sets, or means for a set of synchronization signals associated with a preamble set of the plurality of preamble sets; and means for receiving a random access preamble from the first apparatus.

[0010] In a seventh aspect of the present disclosure, there is provided a computer readable medium. The computer readable medium comprises instructions stored thereon for causing an apparatus to perform at least the method according to the third aspect.

[0011] In an eighth aspect of the present disclosure, there is provided a computer readable medium. The computer readable medium comprises instructions stored thereon for causing an apparatus to perform at least the method according to the fourth aspect.

[0012] It is to be understood that the Summary section is not intended to identify key or essential features of embodiments of the present disclosure, nor is it intended to be used to limit the scope of the present disclosure. Other features of the present disclosure will become easily comprehensible through the following description.BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Some example embodiments will now be described with reference to theaccompanying drawings, where:

[0014] FIG. 1 illustrates an example communication environment in which example embodiments of the present disclosure can be implemented;

[0015] FIG. 2 illustrates an example procedure for beam management for initial access;

[0016] FIG. 3 illustrates an example schematic of RACH preamble mapping;

[0017] FIG. 4 illustrates an example signaling flow for an initial access procedure in accordance with some example embodiments of the present disclosure;

[0018] FIG. 5A illustrates a schematic diagram of example mapping or association between SSBs and preamble sets in accordance with some example embodiments of the present disclosure;

[0019] FIG. 5B illustrates another schematic diagram of example mapping or association between SSBs and preamble sets in accordance with some example embodiments of the present disclosure

[0020] FIG. 6 illustrates a schematic diagram of example mapping or association between SSBs and preamble sets in accordance with some example embodiments of the present disclosure;

[0021] FIG. 7 illustrates a flowchart of a method implemented at a first apparatus in accordance with some example embodiments of the present disclosure;

[0022] FIG. 8 illustrates a flowchart of a method implemented at a second apparatus in accordance with some example embodiments of the present disclosure;

[0023] FIG. 9 illustrates a simplified block diagram of a device that is suitable for implementing example embodiments of the present disclosure; and

[0024] FIG. 10 illustrates a block diagram of an example computer readable medium in accordance with some example embodiments of the present disclosure.

[0025] Throughout the drawings, the same or similar reference numerals represent the same or similar element.DETAILED DESCRIPTION

[0026] Principle of the present disclosure will now be described with reference to someexample embodiments. It is to be understood that these embodiments are described only for the purpose of illustration and help those skilled in the art to understand and implement the present disclosure, without suggesting any limitation as to the scope of the disclosure. Embodiments described herein can be implemented in various manners other than the ones described below.

[0027] In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skills in the art to which this disclosure belongs.

[0028] References in the present disclosure to “one embodiment,” “an embodiment,” “an example embodiment,” and the like indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0029] It shall be understood that although the terms “first,” “second,”..., etc. in front of noun(s) and the like may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another and they do not limit the order of the noun(s). For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and / or” includes any and all combinations of one or more of the listed terms.

[0030] As used herein, “at least one of the following: ” and “at least one of ” and similar wording, where the list of two or more elements are joined by “and” or “or”, mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

[0031] As used herein, unless stated explicitly, performing a step “in response to A” does not indicate that the step is performed immediately after “A” occurs and one or more intervening steps may be included.

[0032] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “has”, “having”, “includes” and / or “including”, when used herein, specify the presence of stated features, elements, and / or components etc., but do not preclude the presence or addition of one or more other features, elements, components and / or combinations thereof.

[0033] As used in this application, the term “circuitry” may refer to one or more or all of the following:(a) hardware-only circuit implementations (such as implementations in only analog and / or digital circuitry) and(b) combinations of hardware circuits and software, such as (as applicable):(i) a combination of analog and / or digital hardware circuit(s) with software / firmware and(ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and(c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

[0034] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[0035] As used herein, the term “communication network” refers to a network following any suitable communication standards, such as New Radio (NR), Long Term Evolution (LTE), LTE-Advanced (LTE-A), Wideband Code Division Multiple Access (WCDMA), High-Speed Packet Access (HSPA), Narrow Band Internet of Things (NB-IoT) and so on. Furthermore, the communications between a terminal device and a network device in the communication network may be performed according to any suitable generation communication protocols, including, but not limited to, the first generation (1G), the second generation (2G), 2.5G, 2.75G, the third generation (3G), the fourth generation (4G), 4.5G, the fifth generation (5G), 5.5G, the sixth generation (6G) communication protocols, and / or any other protocols either currently known or to be developed in the future. Embodiments of the present disclosure may be applied in various communication systems. Given the rapid development in communications, there will of course also be future type communication technologies and systems with which the present disclosure may be embodied. It should not be seen as limiting the scope of the present disclosure to only the aforementioned system.

[0036] As used herein, the term “network device” refers to a node in a communication network via which a terminal device accesses the network and receives services therefrom. The network device may refer to a base station (BS) or an access point (AP), for example, a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), an NR NB (also referred to as a gNB), a Remote Radio Unit (RRU), a radio header (RH), a remote radio head (RRH), a relay, an Integrated Access and Backhaul (IAB) node, a low power node such as a femto, a pico, a non-terrestrial network (NTN) or non-ground network device such as a satellite network device, a low earth orbit (LEO) satellite and a geosynchronous earth orbit (GEO) satellite, an aircraft network device, and so forth, depending on the applied terminology and technology. In some example embodiments, radio access network (RAN) split architecture comprises a Centralized Unit (CU) and a Distributed Unit (DU) at an IAB donor node. An IAB node comprises a Mobile Terminal (IAB-MT) part that behaves like a UE toward the parent node, and a DU part of an IAB node behaves like a base station toward the next-hop IAB node.

[0037] The term “terminal device” refers to any end device that may be capable of wireless communication. By way of example rather than limitation, a terminal device may also be referred to as a communication device, user equipment (UE), a Subscriber Station (SS), a Portable Subscriber Station, a Mobile Station (MS), or an Access Terminal (AT).The terminal device may include, but not limited to, a mobile phone, a cellular phone, a smart phone, voice over IP (VoIP) phones, wireless local loop phones, a tablet, a wearable terminal device, a personal digital assistant (PDA), portable computers, desktop computer, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, vehicle-mounted wireless terminal devices, wireless endpoints, mobile stations, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), USB dongles, smart devices, wireless customer-premises equipment (CPE), an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and applications (e.g., remote surgery), an industrial device and applications (e.g., a robot and / or other wireless devices operating in an industrial and / or an automated processing chain contexts), a consumer electronics device, a device operating on commercial and / or industrial wireless networks, and the like. The terminal device may also correspond to a Mobile Termination (MT) part of an IAB node (e.g., a relay node). In the following description, the terms “terminal device”, “communication device”, “terminal”, “user equipment” and “UE” may be used interchangeably.

[0038] As used herein, the term “resource,” “transmission resource,” “resource block,” “physical resource block” (PRB), “uplink resource,” or “downlink resource” may refer to any resource for performing a communication, for example, a communication between a terminal device and a network device, such as a resource in time domain, a resource in frequency domain, a resource in space domain, a resource in code domain, or any other combination of the time, frequency, space and / or code domain resource enabling a communication, and the like. In the following, unless explicitly stated, a resource in both frequency domain and time domain will be used as an example of a transmission resource for describing some example embodiments of the present disclosure. It is noted that example embodiments of the present disclosure are equally applicable to other resources in other domains.

[0039] FIG. 1 illustrates an example communication environment 100 in which example embodiments of the present disclosure can be implemented. In the communication environment 100, a plurality of communication devices, including a first apparatus 110 and a second apparatus 120, can communicate with each other. In the example of FIG. 1, the first apparatus 110 may comprise a terminal device (for example, a UE), and the second apparatus 120 may comprise a network device (for example, a gNB). The servingarea of the second apparatus 120 may be called a cell 102.

[0040] It is to be understood that the number of first apparatus 110, second apparatus 120 shown in FIG. 1 is given for the purpose of illustration without suggesting any limitations. The communication environment 100 may include any suitable number of devices configured to implementing example embodiments of the present disclosure. Although not shown, it would be appreciated that one or more additional devices may be located in the cell 102, and one or more additional cells may be deployed in the communication environment 100. It is noted that although illustrated as a network device, the second apparatus 120 may be a device other than a network device. Although illustrated as a terminal device, the first apparatus 110 may be a device other than a terminal device.

[0041] In the following, for the purpose of illustration, some example embodiments are described with the first apparatus 110 operating as a terminal device and the second apparatus 120 operating as a network device. However, in some example embodiments, operations described in connection with a terminal device may be implemented at a network device or other device, and operations described in connection with a network device may be implemented at a terminal device or other device.

[0042] In some example embodiments, if the first apparatus 110 is a terminal device or included in a terminal device and the second apparatus 120 is a network device or is included in a network device, a link from the second apparatus 120 to the first apparatus 110 is referred to as a downlink (DL), and a link from the first apparatus 110 to the second apparatus 120 is referred to as an uplink (UL). In DL, the second apparatus 120 is a transmitting (TX) device (or a transmitter) and the first apparatus 110 is a receiving (RX) device (or a receiver). In UL, the first apparatus 110 is a TX device (or a transmitter) and the second apparatus 120 is a RX device (or a receiver).

[0043] In communication, an SSB may be allocated with random access resources. The second apparatus 120 may select an SSB from a plurality of SSBs for example based on signal qualities of different SSBs. Then, PRACH transmission is performed using the random access resource associated with the selected SSB.

[0044] Communications in the communication environment 100 may be implemented according to any proper communication protocol(s), comprising, but not limited to, cellular communication protocols of the first generation (1G), the second generation (2G),the third generation (3G), the fourth generation (4G), the fifth generation (5G), 5.5G, the sixth generation (6G), and the like, wireless local network communication protocols such as Institute for Electrical and Electronics Engineers (IEEE) 802.11 and the like, and / or any other protocols currently known or to be developed in the future. Moreover, the communication may utilize any proper wireless communication technology, comprising but not limited to: Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Frequency Division Duplex (FDD), Time Division Duplex (TDD), Multiple-Input Multiple-Output (MIMO), Orthogonal Frequency Division Multiple (OFDM), Discrete Fourier Transform spread OFDM (DFT-s-OFDM) and / or any other technologies currently known or to be developed in the future.

[0045] The beam management for an initial access procedure for NR has been specified as shown in FIG. 2. The gNB for example via a cell with a multiple transmission and reception points (TRPs) may transmit 202 SSBs to the UE by using different beams. Association may be defined between SS / PBCH blocks (e.g., up to 64 SS / PBCH blocks) and a combination of RACH occasions and PRACH preambles within the occasions.

[0046] UE selects SS / PBCH block for PRACH preamble selection among the ones that are above given threshold. If no SS / PBCH block above threshold, UE may choose any SS / PBCH block for association.

[0047] Then, UE may transmit 210 a PRACH preamble to the gNB. Both the transmitted PRACH preamble and ROs over which the preamble is transmitted indicate the gNB the SS / PBCH block beam which one to use for a second message (Msg2), a third message (Msg3) retransmission scheduling and a fourth message (Msg4).

[0048] UE is expected to use the same TX beam for the PRACH preamble and for Msg4 Hybrid Automatic Repeat Request (HARQ)-Acknowledgement (ACK) on physical uplink control channel (PUCCH). The gNB may use the indicated SS / PBCH beam as RX beam for the reception. TX beam to use for Msg3 transmission is up to UE’s implementation.

[0049] As part of this procedure, the UE indicates the selected SSB via the transmission of the selected PRACH preamble over the selected RO (i.e., the preamble is associated to the certain SSB in that specific RO) for the PRACH transmission. The UE assumes further that the gNB would use the same transmit beam for the Msg2 and Msg4 transmissions.

[0050] Currently, the preamble sets are assigned uniquely for each SSB in each RO over which the SSB is mapped, to allow the gNB to identify the SSB selected by the UE at the time of initial access. This information is used by the gNB for sending physical downlink control channel (PDCCH) for random access response (RAR) using the quasi-colocation (QCL) relationship linked to SSBs. The RACH configuration for contention based initial access and its mapping to SSBs in RRC specification and the illustration of RACH preamble mapping is provided in FIG. 3 and Table 1. In the example of FIG. 3, there are 48 preambles in total. For contention based (CB) initial access, 3 preambles are associated with or mapped to each SSB, or in other words 3 preambles for each SSB.Table 1

[0051] As can be seen from the above, in the current solution, no preamble set is shared across SSBs in the same RO. The contention based (CB) preambles are staticallypartitioned across all SSBs.

[0052] When the base station (BS) receivers implement digital beam forming for RACH Reception, the number of RX beams that can be used to process and detect the RACH preamble may not need to be limited to the RX beams associated with the beam directions of the SSBs mapped to the RO over which the RACH preamble has been transmitted by UE. In this case, BS may detect the preambles transmitted from UE in different SSB coverage areas simultaneously, based on the RX beam signal strength over single RACH occasion itself. Hence the preamble set configuration does not need to be unique for each SSB when the BS has this receiver capability.

[0053] Moreover, the initial access load from different SSB regions may vary significantly. In such cases configuration of same number of RACH preambles per SSB beams is not resource efficient. RACH preambles sharing across SSB beams based on the initial access load estimation can improve BS preamble detection. Reducing the number of RACH occasions for preamble detection during initial access can also improve the initial access latency to some extent.

[0054] With 6G system operating over higher frequency ranges, the number of SSB beams is expected to increase, i.e., two-fold or more. If the SSB to preamble-set mapping or association used in NR is reused as is, it may not be resource efficient and also increase the access delay associated with preamble detection.

[0055] In accordance with some example embodiments of the present disclosure, there is provided a solution for flexible association of preamble sets to synchronization signals. For example, a gNB may transmit to a UE information for associating a plurality of synchronization signals with a plurality of preamble sets. The synchronization signals may include for example SSBs, primary synchronization signals (PSS), or secondary synchronization signals (SSS). A preamble set comprises at least one preamble, and the received information has an indicator which enables one or more synchronization signals to be mapped to or associated with a preamble set. For example, the received information may include at least one indicator indicating a number of synchronization signals associated with a preamble set of the plurality of preamble sets. Alternatively, or in addition, the at least one indicator may indicate a set of synchronization signals associated with a preamble set of the plurality of preamble sets. The UE may select a preamble set from the plurality of preamble sets based on the received information and asynchronization signal selected by the UE. Then, the UE may transmit, to the gNB, a random access preamble in the selected preamble set.

[0056] In embodiments of the present disclosure, flexible mapping between synchronization signals (for example, SSBs) to a preamble-set can be achieved. For example, a preamble set can be mapped with or associated with a plurality of SSBs. The flexible mapping or association may be based on a capability of the gNB for multi-RX reception for RACH preambles.

[0057] Example embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0058] FIG. 4 illustrates an example signaling flow 400 for an initial access procedure in accordance with some example embodiments of the present disclosure. As shown in FIG. 4, the signaling chart 400 involves the first apparatus 110 and the second apparatus 120.

[0059] In operation, the second apparatus 120 may transmit 402, to the first apparatus 110, information for associating a plurality of synchronization signals with a plurality of preamble sets. Correspondingly, the first apparatus 110 may receive 404 the information from the second apparatus 120. A preamble set comprises at least one preamble, and the information may include at least one indicator. The at least one indicator enables one or more synchronization signals to be mapped to or associated with a preamble set, in particular, enables a plurality of synchronization signals to be mapped to or associated with a preamble set. For example, the received information may include RACH configuration information, for example, the information element (IE) RACH- ConfigCommon.

[0060] In some example embodiments, two or more synchronization signals may be associated with a same preamble set of the plurality of preamble sets based on the received information. For example, more than one SSBs may be mapped to the same preamble set. In some example embodiments, the respective transmitting beams of the two or more synchronization signals are orthogonal to each other. For example, the gNb may configure SSBs that are spatially separated (orthogonal beams) associated to the same preamble set. In this way, collision of contention based random access between different UEs may be alleviated.

[0061] The at least one indicator may be of any suitable types to indicate the mapping between the synchronization signals and the preamble sets. In some example embodiments, the at least one indicator may indicate a number of synchronization signals associated with a preamble set of the plurality of preamble sets. For example, the information may include an IE which indicates the number of synchronization signals mapped to each preamble set of the plurality of preamble sets. In the following, such a configuration may be also referred to as “Configuration 1” merely for purpose of discussion without any limitation.

[0062] In an example, a parameter or IE “SSB-Per-Preamble-set” may be introduced (it is to be noted that the name of the parameter or IE may be different, if its role is the same). This parameter indicates the number of SSBs mapped to one preamble set, whereby more than one preamble set can be configured by the BS if needed using legacy signalling. In other words, and differently from NR operations, the BS would be able to map more than one SSB to one preamble-set and realize a preamble-set sharing across SSBs which correspond to different beams. Based on the number indicated by this parameter, the UE may select the preamble-set for its selected SSB for random selection of preamble for Msgl transmission. The Contention-based (CB)-preamble configuration will remain same as NR in this case.

[0063] In some example embodiments, the second apparatus 120 may determine the number of synchronization signals associated with the preamble set of the plurality of preamble sets based on a capability of the second apparatus 120 in beam detection over different beams. For example, the value of the parameter “SSB-Per-Preamble-set” may be based on the RX reception and preamble detection capability of the BS over multiple beams.

[0064] Alternatively, or in addition, in some example embodiments, the at least one indicator may indicate a set of synchronization signals associated with a preamble set of the plurality of preamble sets. For example, for a preamble set, the information may include a list of indices of synchronization signals, such as a list of SSB indices. In the following, such a configuration may be also referred to as “Configuration 2” merely for purpose of discussion without any limitation.

[0065] In an example, multiple preamble sets may be configured and each preamble set may be also configured with explicit mapping of SSB indices. This Configuration 2requires a slightly higher number of additional signaling bits to be configured via for example, radio resource control (RRC) signaling, but allows flexible grouping of SSBs and the number of preambles based on initial access configuration in addition to the benefits of the Configuration 1.

[0066] Continuing with flow 400, the first apparatus 110 may select a synchronization signal for example based on measurements on the plurality of synchronization signals. Then, the first apparatus 110 may select a preamble set from the plurality of preamble sets based on the received information and the selected synchronization signal. For example, an SSB may be selected based on measurements on a plurality of SSBs, and a preamble set may be determined based on the selected SSB and the RACH configuration information.

[0067] In some example embodiments, the at least one indicator may indicate the number of synchronization signals associated with the preamble set of the plurality of preamble sets (for example in the case of Configuration 1) and may further indicate a number of preamble sets associated with an RO. In such example embodiments, the first apparatus 110 may determine one or more preambles sets associated with the selected synchronization signal based on the number of synchronization signals, the number of preamble sets associated with the RO and a predefined rule. Then, the first apparatus 110 may select the preamble set from the one or more preambles sets. For example, in the case of Configuration 1, more than one SSBs may be mapped to a single preamble set, and the RACH configuration may indicate the number of preamble sets mapped to each RO. UE may determine whether a selected SSB is mapped to a preamble set based on the RACH configuration and a predefined rule (for example, as defined in a technical specification). Then, the UE may select one preamble set based on the selected SSB is mapped to the preamble set.

[0068] In an example, a new IE shown in Table 2 may be introduced in the IE RACH- ConfigCommon. The behavior of the UE may depend on the value of the parameter “SSB- Per-Preamble-set”. More specifically, the way how the UE may interpret the IE in Table 1 may depend on the value of the parameter “SSB-Per-Preamble-set”.Table 2

[0069] In some example embodiments, the first apparatus 110 may determine at least one RO. For each RO of the at least one RO, the first apparatus 110 may determine at least one preamble set mapped to the RO based on the number of preamble sets associated with the RO. The first apparatus 110 may allocate the plurality of synchronization signals to the at least one preamble set determined for the at least one RO based on respective indices of the plurality of synchronization signals. The first apparatus 110 may determine the one or more preamble sets associated with the selected synchronization signal based on the allocation of the selected synchronization signal.

[0070] To better understand such example embodiments, two example cases are described now. In a first example case, the value of the parameter “SSB-Per-Preamble- set” is larger than 1. The UE may interpret the IE ssb-perRACH-OccasionAndCB- PreamblesPerSSB as shown in Table 1 as providing at least the number of SSB beams per RO, i.e., the “ssb-perRACH-Occasion” part of the IE, while the parameter “SSB-Per- Preamble-set” provides the number of SSBs that will be mapped to each preamble-set stemming from the IE ssb-perRACH-OccasionAndCB-PreamblesPerSSB configuration.

[0071] Table 3 shows an example.Table 3

[0072] In the example shown in Table 3, UE may determine that there are 3ROs, and for each RO, there are two preamble sets. As such, UE determines that the first two sets (set #0 and #1) mapped to RO #0, the next two sets mapped to RO#1, and so on. FIG. 5A shows an example mapping or association between SSBs and preamble sets in this example.

[0073] In a second example case, the value of the parameter “SSB-Per-Preamble-set” is equal to 1. The UE may interpret the IE ssb-perRACH-OccasionAndCB- PreamblesPerSSB as shown in Table 1 as per legacy NR operations. Table 4 shows an example in this case.Table 4

[0074] In the example shown in Table 4, UE may determine that there are 3ROs, and for each RO, there are two preamble sets. As such, UE determines that the first two sets (set #0 and #1) mapped to RO #0, the next two preamble sets mapped to RO#1, and so on. FIG. 5B shows an example mapping or association between SSBs and preamble sets in this example.

[0075] In these examples, according to Configuration 1, at least one SSB is mapped to each RO and at least one SSB is mapped to each preamble set within each RO. It is worth observing that the UE could still select the RACH occasion based on the legacy procedure and only the preamble selection would be affected in this case.

[0076] In some example embodiments, for example, in the case of Configuration 2, the received information or the at least one indicator may include an identification of at least one preamble set of the plurality of preamble sets, and respective indexes of the set of synchronization signals associated with each preamble set of the at least one preamble set. For example, the gNB may dynamically configure which one or more preamble sets are mapped with more than one SSB. In such example embodiments, the first apparatus 110 may select, from the at least one preamble set, the preamble set associated with an index of the selected synchronization signal.

[0077] Table 5 shows an example configuration. In the example, the parameter“cbPreambleToRemoveList” may be used to indicate the at least one preamble set to which more than one SSBs are mapped. The parameter “ssb-List” may include indices of SSBs mapped to each of the at least one preamble set.Table 5

[0078] In this configuration, multiple preamble sets with each preamble set mapping to list of SSBs as dynamic configuration list using Add / Mod / Release. This dynamic list configuration allows the network to modify the SSB-Grouping and also re-arranging the groups based on system capability and access load situation. The network should ensure that all the SSBs are mapped to one entry in this list.

[0079] FIG. 6 illustrates example mapping or association in this configuration. In the example, there are 8 SSBs per cell and two CB preamble sets are configured in two ROs. Each preamble set is mapped to a different list of SSBs. As shown in FIG. 6, SSBs 1 to 5 are mapped to preamble set 1, and SSBs 6 to 8 are mapped to preamble set 2.

[0080] Reference is now made back to FIG. 4. After selecting 406 the preamble set, the first apparatus 110 may transmit 408, to the second apparatus 120, a random access preamble in the selected preamble set. In some example embodiments, the random access preamble may be transmitted using a beam corresponding to the selected synchronization signal. For example, a preamble in the selected preamble set may be transmitted using a beam corresponding to the selected SSB.

[0081] Correspondingly, the second apparatus 120 may receive 410 the random access preamble from the first apparatus 110. To receive the random access preamble, the second apparatus 120 may detect the random access preamble using a plurality of beamscorresponding to the plurality of synchronization signals. In some example embodiments, the second apparatus 120 may select 412 at least one beam from the plurality of beams based on the detection. In some example embodiments, the at least one beam may be selected based on a received signal strength over the plurality of beams. Then, the second apparatus 120 may transmit 414, to the first apparatus 110, at least one random access response (RAR) using the at least one beam respectively.

[0082] In an example, the BS may receive the preamble using all RX beams based on SSB mapping and determine the best beam based on RX processing for RACH. Then, the BS may send RAR using a QCL beam of the best beam.

[0083] In some example embodiments, the same random access preamble may be detected on more than one beam. If the received signal strengths over these beams are similar (for example, difference among them is below a threshold), the second apparatus 110 may transmit separate RARs using these beams. For example, if the same random access preamble is detected on two or more beams, and a difference between received signal strengths over the two or more beams is below the threshold, the second apparatus 120 may transmit RARs using the two or more beams. In this way, collision of the preamble across different beams can be handled.

[0084] In the following procedure, the first apparatus 110 may receive 416, from the second apparatus 120, the RAR using a beam corresponding to the selected synchronization signal. For example, the UE may receive the Msg2 using the beam corresponding to the selected SSB.

[0085] In response to the RAR, the first apparatus 110 may transmit 418, to the second apparatus, a RRC request using the beam corresponding to the selected synchronization signal. For example, the UE may transmit the Msg3 to the BS using the beam corresponding to the selected SSB.

[0086] The second apparatus 120 may receive 420, from the first apparatus 110, the RRC request using the at least one selected beam. For example, the BS may receive the Msg3 from the UE using the best beam. In response to the RRC request, the second apparatus 120 may transmit 422, to the first apparatus 110, a contention resolution message using the at least one selected beam. For example, the BS may transmit the Msg4 to the UE using the at least one selected beam.

[0087] The first apparatus 110 may receive 424, from the second apparatus 120, the contention resolution message using the beam corresponding to the selected synchronization signal. For example, the UE may receive the Msg4 using the beam corresponding to the selected SSB.

[0088] In some example embodiments, if the same random access preamble is detected on different beams as described above, the second apparatus 120 may transmit a contention resolution message indicating contention resolution for these beams. For example, if the same preamble is detected on a beam corresponding to SSB1 and a beam corresponding to SSB2, the contention resolution message may include contention resolution identifiers for both the beams or in other words for both the SSB1 and SSB2.

[0089] In an example, the BS may configure SSBs that are spatially separated (orthogonal beams) associated to the same preamble set. That would allow potentially transmitting e.g. Msg2 in MU-MIMO style as well as Msg3 and Msg4 for the UEs that are under different SSBs. The UE may use the selected SSB as the QCL source for reception of downlink channels (for example, Msg2 and Msg4) and for transmission of uplink channels (for example, Msg3, Msg4, and HARQ-ACK). The BS forms reception and transmission beams based on received PRACH preambles. The BS may be able to estimate UE’s preferred SSB beam based on spatial domain PRACH detection.

[0090] In present disclosure, a solution is proposed for initial access where the preamble selection for initial access is modified. In this way, the network configuration of mapping of multiple SSBs to the same preamble set is allowed, so as to improve resource efficiency.

[0091] FIG. 7 shows a flowchart of an example method 700 implemented at a first apparatus in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 700 will be described from the perspective of the terminal device 110 in FIG. 1.

[0092] At block 710, the first apparatus 110 receives, from a second apparatus, information for associating a plurality of synchronization signals with a plurality of preamble sets. A preamble set comprises at least one preamble, and the received information comprises at least one indicator indicating at least one of: a number of synchronization signals associated with a preamble set of the plurality of preamble sets, or a set of synchronization signals associated with a preamble set of the plurality of preamble sets.

[0093] At block 720, the first apparatus 110 select a preamble set from the plurality of preamble sets based on the received information and a synchronization signal selected by the first apparatus.

[0094] At block 730, the first apparatus 110 transmit, to the second apparatus, a random access preamble in the selected preamble set.

[0095] In some example embodiments, the first apparatus 110 may determine one or more preambles sets associated with the selected synchronization signal based on the number of synchronization signals, the number of preamble sets and a predefined rule; and select the preamble set from the one or more preambles sets.

[0096] In some example embodiments, the first apparatus 110 may determine at least one random access occasion; for each random access occasion of the at least one random access occasion, determine at least one preamble set mapped to the random access occasion based on the number of preamble sets associated with the random access occasion; allocate the plurality of synchronization signals to the at least one preamble set determined for the at least one random access occasion based on respective indices of the plurality of synchronization signals; and determining the one or more preambles sets associated with the selected synchronization signal based on the allocation of the selected synchronization signal.

[0097] In some example embodiments, the received information comprises: an identification of at least one preamble set of the plurality of preamble sets, and respective indexes of the set of synchronization signals associated with each preamble set of the at least one preamble set.

[0098] In some example embodiments, the first apparatus 110 may select, from the at least one preamble set, the preamble set associated with an index of the selected synchronization signal.

[0099] In some example embodiments, two or more synchronization signals are associated with a same preamble set of the plurality of preamble sets based on the received information.

[0100] In some example embodiments, respective transmitting beams of the two or more synchronization signals are orthogonal to each other.

[0101] In some example embodiments, the random access preamble is transmitted usinga beam corresponding to the selected synchronization signal.

[0102] In some example embodiments, the first apparatus 110 may receive, from the second apparatus, a random access response using a beam corresponding to the selected synchronization signal.

[0103] In some example embodiments, the first apparatus 110 may in response to the random access response, transmit to the second apparatus, a radio resource control request using the beam corresponding to the selected synchronization signal; and receive, from the second apparatus, a contention resolution message using the beam corresponding to the selected synchronization signal.

[0104] In some example embodiments, the first apparatus is or is comprised in a terminal device, and the second apparatus is or is comprised in a network device.

[0105] FIG. 8 shows a flowchart of an example method 800 implemented at a second apparatus in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 800 will be described from the perspective of the terminal device 110 in FIG. 1.

[0106] At block 810, the second apparatus 120 transmits, to a first apparatus, information at least for associating a plurality of synchronization signals with a plurality of preamble sets. A preamble set comprises at least one preamble, and the transmitted information comprises at least one indicator indicating at least one of: a number of synchronization signals associated with a preamble set of the plurality of preamble sets, or a set of synchronization signals associated with a preamble set of the plurality of preamble sets.

[0107] At block 840, the second apparatus 120 receives a random access preamble from the first apparatus.

[0108] In some example embodiments, the second apparatus 120 may detect the random access preamble using a plurality of beams corresponding to the plurality of synchronization signals; select at least one beam from the plurality of beams based on the detection; and transmit, to the first apparatus, at least one random access response using the at least one beam respectively.

[0109] In some example embodiments, the at least one beam is selected based on a received signal strength of the random access preamble over the plurality of beams.

[0110] In some example embodiments, two or more beams are selected based on that a difference between received signal strengths of the random access preamble over the two or more beams is below a threshold.

[0111] In some example embodiments, the second apparatus 120 may determine the number of synchronization signals associated with the preamble set of the plurality of preamble sets based on a capability of the second apparatus in beam detection over different beams.

[0112] In some example embodiments, the second apparatus 120 may determine the set of synchronization signals associated with the preamble set of the plurality of preamble sets based on at least one of: a capability of the second apparatus in beam detection over different beams, or a random access load at the second apparatus.

[0113] In some example embodiments, the transmitted information comprises: an identification of at least one preamble set of the plurality of preamble sets, and respective indexes of the set of synchronization signals associated with each preamble set of the at least one preamble set.

[0114] In some example embodiments, two or more synchronization signals are associated with a same preamble set of the plurality of preamble sets based on the received information.

[0115] In some example embodiments, respective transmitting beams of the two or more synchronization signals are orthogonal to each other.

[0116] In some example embodiments, the second apparatus 120 may receive, from the first apparatus, a radio resource control request using the at least one beam; and in response to the radio resource control request, transmit to the first apparatus, a contention resolution message using the at least one beam.

[0117] In some example embodiments, the second apparatus may transmit a contention resolution message indicating contention resolution for the two or more beams.

[0118] In some example embodiments, the first apparatus is or is comprised in a terminal device, and the second apparatus is or is comprised in a network device.

[0119] In some example embodiments, a first apparatus capable of performing any of the method 700 may comprise means for performing the respective operations of themethod 700. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

[0120] In some example embodiments, the first apparatus comprises means for receiving, from a second apparatus, information for associating a plurality of synchronization signals with a plurality of preamble sets, wherein a preamble set comprises at least one preamble, and the received information comprises at least one indicator indicating at least one of: means for a number of synchronization signals associated with a preamble set of the plurality of preamble sets, or means for a set of synchronization signals associated with a preamble set of the plurality of preamble sets; means for selecting a preamble set from the plurality of preamble sets based on the received information and a synchronization signal selected by the first apparatus; and means for transmitting, to the second apparatus, a random access preamble in the selected preamble set.

[0121] In some example embodiments, the first apparatus further comprises: means for determining one or more preambles sets associated with the selected synchronization signal based on the number of synchronization signals, the number of preamble sets and a predefined rule; and means for selecting the preamble set from the one or more preambles sets.

[0122] In some example embodiments, the first apparatus further comprises: means for determining at least one random access occasion; means for for each random access occasion of the at least one random access occasion, determining at least one preamble set mapped to the random access occasion based on the number of preamble sets associated with the random access occasion; means for allocating the plurality of synchronization signals to the at least one preamble set determined for the at least one random access occasion based on respective indices of the plurality of synchronization signals; and means for determining the one or more preambles sets associated with the selected synchronization signal based on the allocation of the selected synchronization signal.

[0123] In some example embodiments, the received information comprises: an identification of at least one preamble set of the plurality of preamble sets, and respective indexes of the set of synchronization signals associated with each preamble set of the at least one preamble set.

[0124] In some example embodiments, the first apparatus further comprises: means forselecting, from the at least one preamble set, the preamble set associated with an index of the selected synchronization signal.

[0125] In some example embodiments, two or more synchronization signals are associated with a same preamble set of the plurality of preamble sets based on the received information.

[0126] In some example embodiments, respective transmitting beams of the two or more synchronization signals are orthogonal to each other.

[0127] In some example embodiments, the random access preamble is transmitted using a beam corresponding to the selected synchronization signal.

[0128] In some example embodiments, the first apparatus further comprises: means for receiving, from the second apparatus, a random access response using a beam corresponding to the selected synchronization signal.

[0129] In some example embodiments, the first apparatus further comprises: means for in response to the random access response, transmitting to the second apparatus, a radio resource control request using the beam corresponding to the selected synchronization signal; and means for receiving, from the second apparatus, a contention resolution message using the beam corresponding to the selected synchronization signal.

[0130] In some example embodiments, the first apparatus is or is comprised in a terminal device, and the second apparatus is or is comprised in a network device.

[0131] In some example embodiments, a second apparatus capable of performing any of the method 800 may comprise means for performing the respective operations of the method 800. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

[0132] In some example embodiments, the second apparatus comprises means for transmitting, to a first apparatus, information at least for associating a plurality of synchronization signals with a plurality of preamble sets, wherein a preamble set comprises at least one preamble, and the transmitted information comprises at least one indicator indicating at least one of: a number of synchronization signals associated with a preamble set of the plurality of preamble sets, or a set of synchronization signals associated with a preamble set of the plurality of preamble sets; and means for receiving a random access preamble from the first apparatus.

[0133] In some example embodiments, the second apparatus further comprises: means for detecting the random access preamble using a plurality of beams corresponding to the plurality of synchronization signals; means for selecting at least one beam from the plurality of beams based on the detection; and means for transmitting, to the first apparatus, at least one random access response using the at least one beam respectively .

[0134] In some example embodiments, the at least one beam is selected based on a received signal strength of the random access preamble over the plurality of beams.

[0135] In some example embodiments, two or more beams are selected based on that a difference between received signal strengths of the random access preamble over the two or more beams is below a threshold.

[0136] In some example embodiments, the second apparatus further comprises: means for determining the number of synchronization signals associated with the preamble set of the plurality of preamble sets based on a capability of the second apparatus in beam detection over different beams.

[0137] In some example embodiments, the second apparatus further comprises: means for determining the set of synchronization signals associated with the preamble set of the plurality of preamble sets based on at least one of: a capability of the second apparatus in beam detection over different beams, or a random access load at the second apparatus.

[0138] In some example embodiments, the transmitted information comprises: an identification of at least one preamble set of the plurality of preamble sets, and respective indexes of the set of synchronization signals associated with each preamble set of the at least one preamble set.

[0139] In some example embodiments, two or more synchronization signals are associated with a same preamble set of the plurality of preamble sets based on the received information.

[0140] In some example embodiments, respective transmitting beams of the two or more synchronization signals are orthogonal to each other.

[0141] In some example embodiments, the second apparatus further comprises: means for receiving, from the first apparatus, a radio resource control request using the at least one beam; and means for in response to the radio resource control request, transmitting to the first apparatus, a contention resolution message using the at least one beam.

[0142] In some example embodiments, the second apparatus may comprise means for transmitting a contention resolution message indicating contention resolution for the two or more beams.

[0143] In some example embodiments, the first apparatus is or is comprised in a terminal device, and the second apparatus is or is comprised in a network device.

[0144] FIG. 9 is a simplified block diagram of a device 900 that is suitable for implementing example embodiments of the present disclosure. The device 900 may be provided to implement a communication device, for example, the first apparatus 110 or the second apparatus 120 as shown in FIG. 1. As shown, the device 900 includes one or more processors 910, one or more memories 920 coupled to the processor 910, and one or more communication modules 940 coupled to the processor 910.

[0145] The communication module 940 is for bidirectional communications. The communication module 940 has one or more communication interfaces to facilitate communication with one or more other modules or devices. The communication interfaces may represent any interface that is necessary for communication with other network elements. In some example embodiments, the communication module 940 may include at least one antenna.

[0146] The processor 910 may be of any type suitable to the local technical network and may include one or more of the following: general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 900 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

[0147] The memory 920 may include one or more non-volatile memories and one or more volatile memories. Examples of the non-volatile memories include, but are not limited to, a Read Only Memory (ROM) 924, an electrically programmable read only memory (EPROM), a flash memory, a hard disk, a compact disc (CD), a digital video disk (DVD), an optical disk, a laser disk, and other magnetic storage and / or optical storage. Examples of the volatile memories include, but are not limited to, a randomaccess memory (RAM) 922 and other volatile memories that will not last in the powerdown duration.

[0148] A computer program 930 includes computer executable instructions that are executed by the associated processor 910. The instructions of the program 930 may include instructions for performing operations / acts of some example embodiments of the present disclosure. The program 930 may be stored in the memory, e.g., the ROM 924. The processor 910 may perform any suitable actions and processing by loading the program 930 into the RAM 922.

[0149] The example embodiments of the present disclosure may be implemented by means of the program 930 so that the device 900 may perform any process of the disclosure as discussed with reference to FIG. 2 to FIG. 7. The example embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

[0150] In some example embodiments, the program 930 may be tangibly contained in a computer readable medium which may be included in the device 900 (such as in the memory 920) or other storage devices that are accessible by the device 900. The device 900 may load the program 930 from the computer readable medium to the RAM 922 for execution. In some example embodiments, the computer readable medium may include any types of non-transitory storage medium, such as ROM, EPROM, a flash memory, a hard disk, CD, DVD, and the like. The term “non-transitory,” as used herein, is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM).

[0151] FIG. 10 shows an example of the computer readable medium 1000 which may be in form of CD, DVD or other optical storage disk. The computer readable medium 1000 has the program 930 stored thereon.

[0152] Generally, various embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, and other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. Although various aspects of embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representations, it is to be understood that the block, apparatus, system, technique or method described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware orcontroller or other computing devices, or some combination thereof.

[0153] Some example embodiments of the present disclosure also provide at least one computer program product tangibly stored on a computer readable medium, such as a non-transitory computer readable medium. The computer program product includes computer-executable instructions, such as those included in program modules, being executed in a device on a target physical or virtual processor, to carry out any of the methods as described above. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various embodiments. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

[0154] Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. The program code may be provided to a processor or controller of a general-purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program code, when executed by the processor or controller, cause the functions / operations specified in the flowcharts and / or block diagrams to be implemented. The program code may execute entirely on a machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

[0155] In the context of the present disclosure, the computer program code or related data may be carried by any suitable carrier to enable the device, apparatus or processor to perform various processes and operations as described above. Examples of the carrier include a signal, computer readable medium, and the like.

[0156] The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable medium may include but not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of the computer readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random-access memory (RAM), a read-only memory (ROM), an erasable programmable readonly memory (EPROM or Flash memory), an optical fiber, a portable compact disc readonly memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0157] Further, although operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Eikewise, although several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular embodiments. Unless explicitly stated, certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, unless explicitly stated, various features that are described in the context of a single embodiment may also be implemented in a plurality of embodiments separately or in any suitable sub-combination.

[0158] Although the present disclosure has been described in languages specific to structural features and / or methodological acts, it is to be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

WHAT IS CLAIMED IS:

1. A first apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first apparatus at least to: receive, from a second apparatus, information for associating a plurality of synchronization signals with a plurality of preamble sets, wherein a preamble set comprises at least one preamble, and the received information comprises at least one indicator indicating at least one of: a number of synchronization signals associated with a preamble set of the plurality of preamble sets, or a set of synchronization signals associated with a preamble set of the plurality of preamble sets; select a preamble set from the plurality of preamble sets based on the received information and a synchronization signal selected by the first apparatus; and transmit, to the second apparatus, a random access preamble in the selected preamble set.

2. The first apparatus of claim 1, wherein the received information further indicates a number of preamble sets associated with a random access occasion, and the first apparatus is caused to: determine one or more preambles sets associated with the selected synchronization signal based on the number of synchronization signals, the number of preamble sets and a predefined rule; and select the preamble set from the one or more preambles sets.

3. The first apparatus of claim 2, wherein the first apparatus is caused to: determine at least one random access occasion; for each random access occasion of the at least one random access occasion, determine at least one preamble set mapped to the random access occasion based on the number of preamble sets associated with the random access occasion;allocate the plurality of synchronization signals to the at least one preamble set determined for the at least one random access occasion based on respective indices of the plurality of synchronization signals; and determine the one or more preambles sets associated with the selected synchronization signal based on the allocation of the selected synchronization signal.

4. The first apparatus of claim 1, wherein the received information comprises: an identification of at least one preamble set of the plurality of preamble sets, and respective indexes of the set of synchronization signals associated with each preamble set of the at least one preamble set.

5. The first apparatus of claim 4, wherein the first apparatus is caused to: select, from the at least one preamble set, the preamble set associated with an index of the selected synchronization signal.

6. The first apparatus of claim 1, wherein two or more synchronization signals are associated with a same preamble set of the plurality of preamble sets based on the received information.

7. The first apparatus of claim 6, wherein respective transmitting beams of the two or more synchronization signals are orthogonal to each other.

8. The first apparatus of claim 1, wherein the random access preamble is transmitted using a beam corresponding to the selected synchronization signal.

9. The first apparatus of claim 1, wherein the first apparatus is further caused to: receive, from the second apparatus, a random access response using a beam corresponding to the selected synchronization signal.

10. The first apparatus of claim 9, wherein the first apparatus is further caused to: in response to the random access response, transmit, to the second apparatus, a radio resource control request using the beam corresponding to the selected synchronization signal; and receive, from the second apparatus, a contention resolution message using the beamcorresponding to the selected synchronization signal.

11. The first apparatus of any of claims 1 to 10, wherein the first apparatus is or is comprised in a terminal device, and the second apparatus is or is comprised in a network device.

12. A second apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second apparatus at least to: transmit, to a first apparatus, information for associating a plurality of synchronization signals with a plurality of preamble sets, wherein a preamble set comprises at least one preamble, and the transmitted information comprises at least one indicator indicating at least one of: a number of synchronization signals associated with a preamble set of the plurality of preamble sets, or a set of synchronization signals associated with a preamble set of the plurality of preamble sets; and receive a random access preamble from the first apparatus.

13. The second apparatus of claim 12, wherein the second apparatus is further caused to: detect the random access preamble using a plurality of beams corresponding to the plurality of synchronization signals; select at least one beam from the plurality of beams based on the detection; and transmit, to the first apparatus, at least one random access response using the at least one beam respectively.

14. The second apparatus of claim 13, wherein the at least one beam is selected based on a received signal strength of the random access preamble over the plurality of beams.

15. The second apparatus of claim 13, wherein two or more beams are selected based on that a difference between received signal strengths of the random access preamble over the two or more beams is below a threshold.

16. The second apparatus of claim 12, wherein the second apparatus is caused to: determine the number of synchronization signals associated with the preamble set of the plurality of preamble sets based on a capability of the second apparatus in beam detection over different beams.

17. The second apparatus of claim 12, wherein the second apparatus is caused to: determine the set of synchronization signals associated with the preamble set of the plurality of preamble sets based on at least one of: a capability of the second apparatus in beam detection over different beams, or a random access load at the second apparatus.

18. The second apparatus of claim 12, wherein the transmitted information comprises: an identification of at least one preamble set of the plurality of preamble sets, and respective indexes of the set of synchronization signals associated with each preamble set of the at least one preamble set.

19. The second apparatus of claim 12, wherein two or more synchronization signals are associated with a same preamble set of the plurality of preamble sets based on the received information.

20. The second apparatus of claim 19, wherein respective transmitting beams of the two or more synchronization signals are orthogonal to each other.

21. The second apparatus of claim 13, wherein the second apparatus is further caused to: receive, from the first apparatus, a radio resource control request using the at least one beam; and in response to the radio resource control request, transmit, to the first apparatus, a contention resolution message using the at least one beam.

22. The second apparatus of claim 15, wherein the second apparatus is further caused to: transmit a contention resolution message indicating contention resolution for the two or more beams.

23. The second apparatus of any of claims 12 to 22, wherein the first apparatus is or is comprised in a terminal device, and the second apparatus is or is comprised in a network device.

24. A method comprising: receiving, at a first apparatus from a second apparatus, information for associating a plurality of synchronization signals with a plurality of preamble sets, wherein a preamble set comprises at least one preamble, and the received information comprises at least one indicator indicating at least one of: a number of synchronization signals associated with a preamble set of the plurality of preamble sets, or a set of synchronization signals associated with a preamble set of the plurality of preamble sets; selecting a preamble set from the plurality of preamble sets based on the received information and a synchronization signal selected by the first apparatus; and transmitting, to the second apparatus, a random access preamble in the selected preamble set.

25. A method comprising: transmitting, at a second apparatus to a first apparatus, information at least for associating a plurality of synchronization signals with a plurality of preamble sets, wherein a preamble set comprises at least one preamble, and the transmitted information comprises at least one indicator indicating at least one of: a number of synchronization signals associated with a preamble set of the plurality of preamble sets, or a set of synchronization signals associated with a preamble set of the plurality of preamble set; and receiving a random access preamble from the first apparatus.

26. A first apparatus comprising: means for receiving, from a second apparatus, information for associating a plurality of synchronization signals with a plurality of preamble sets, wherein a preamble set comprises at least one preamble, and the received information comprises at least one indicator indicatingat least one of: a number of synchronization signals associated with a preamble set of the plurality of preamble sets, or a set of synchronization signals associated with a preamble set of the plurality of preamble sets; means for selecting a preamble set from the plurality of preamble sets based on the received information and a synchronization signal selected by the first apparatus; and means for transmitting, to the second apparatus, a random access preamble in the selected preamble set.

27. A second apparatus comprising: means for transmitting, to a first apparatus, information at least for associating a plurality of synchronization signals with a plurality of preamble sets, wherein a preamble set comprises at least one preamble, and the transmitted information comprises at least one indicator indicating at least one of: a number of synchronization signals associated with a preamble set of the plurality of preamble sets, or a set of synchronization signals associated with a preamble set of the plurality of preamble sets; and means for receiving a random access preamble from the first apparatus.

28. A computer readable medium comprising instructions stored thereon for causing an apparatus at least to perform the method of claim 24 or the method of claim 25.

Images