Method of random-access procedure in cellular networks

Abstract

The present invention discloses a method for random access procedure (RACH) in a wireless communication system The method comprises, receiving, by at least one first node, at least one of at least one synchronization signal block (SSB) index, and at least one RACH configuration, wherein the at least one SSB index represents at least one SSB of an SSB burst, wherein the at least one RACH configuration indicates plurality of RACH occasions (ROs), and wherein the plurality of ROs is available for a fixed time duration from a reference point. The method further comprises, mapping, by the at least one first node, the at least one SSB index to at least one valid RO from the plurality of ROs. The method further comprises, transmitting, by the at least one first node, a RACH preamble in a valid RO from the at least one valid RO.

Description

METHOD OF RANDOM-ACCESS PROCEDURE IN CELLULAR NETWORKS FIELD OF INVENTION

[0001] The present invention generally relates to cellular networks. More specifically, the present invention is related to method of random-access procedure in cellular networks. BACKGROUND OF THE INVENTION

[0002] The subject matter discussed in the background section should not be assumed to be prior art merely as a result of its mention in the background section. Similarly, a problem mentioned in the background section or associated with the subject matter of the background section should not be assumed to have been previously recognized in the prior art. The subject matter in the background section merely represents different approaches, which in and of themselves may also correspond to implementations of the claimed technology.

[0003] Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. These systems have developed through various generations to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example telecommunication standard is 5G New Radio (NR). A fifth generation (5G) wireless standard, referred to as New Radio (NR), enables higher data transfer speeds, greater numbers of connections, and better coverage, among other improvements.5G NR includes services associated with enhanced mobile broadband (eMBB), massive machine type communications (mMTC), and ultra-reliable low latency communications (URLLC). Some aspects of 5G NR may be based on the 4G Long Term Evolution (LTE) standard. There exists a need for further improvements in 5G NR technology.

[0004] Designing a sustainable future cellular technology is as important as expanding it across industries and geographical areas, providing more advanced services and applications. Certainly, the future cellular network become denser and more complex and employ a greater number of antennas, larger bandwidths and additional frequency bands to meet the requirements to support advanced features. However, the environmental impact of the cellular technology needs to stay under control, and novel solutions to improve energy efficiency of the network need to be developed for environmental sustainability and operational cost savings.Reducing or avoiding always on transmission, lean signal design, adaptation of various operations based on network conditions, etc. are important factors help reducing energy consumption. ON demand transmission of signals and channels, i.e., transmitting signals and channels based on request, is a major technique to avoid always on transmissions. Currently, the network performs various set of operations to establish and maintain connection with the UEs in the network, irrespective of load in the network. E.g., in fifth generation new radio (5G- NR) technology, the base station (BS) transmits synchronization signal block (SSB) and system information block 1 (SIB1) periodically, irrespective of whether the user is trying to connect to the network or not, to assist UE in initial access procedure. However, these signals are unused most of the time, especially in case of low load and low user arrival rate, leading to wastage of energy at the BS. Instead, the user equipment (UE) requesting the BS to initiate initial access procedure and BS transmitting SSB and SIB1 in response to the request can minimize transmissions from the BS and reduce energy consumption. Also, it ensures efficient utilization of the transmitted signal. Further, the transmission and reception from the BS should not only ensure reliable communication with the UEs, but it should be optimized for reliability and energy efficiency based on network condition, deployment scenario, etc. E.g., in 5G-NR, a set of SSBs, also known as SSB burst, is transmitted by the BS periodically to assist UE in measurements and initial access. These SSBs can be transmitted using different beams in different directions to cover the entire coverage region of the BS. Currently, the periodicity is defined per SSB burst, i.e., SSBs are transmitted with same periodicity in all directions of the intended coverage region. However, the utilization of the transmitted SSB depends on the UE arrival rate, which can vary across the coverage region. Therefore, it is beneficial to adapt the transmission of SSBs within an SSB burst, based on the characteristics of the coverage region, to minimize number of transmissions and to improve utilization of transmitted SSBs.

[0005] This invention describes the initial access procedure that supports various adaptation of SSB and SIB1. Invention details the configurations required and behaviour of various nodes in the network for efficient implementation of the procedure. SUMMARY OF THE INVENTION

[0006] In general, embodiments of the present disclosure herein provide methods of random-access procedure in cellular networks. Other implementations will be or will become, apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional implementations be included within thisdescription be within the scope of the disclosure and be protected within the scope of the following claims.

[0007] In one embodiment, the present disclosure provides a method for random access procedure (RACH) in a wireless communication system. The method comprises, receiving, by at least one first node, at least one of at least one synchronization signal block (SSB) index, and at least one RACH configuration, wherein the at least one SSB index represents at least one SSB of an SSB burst, wherein the at least one RACH configuration indicates plurality of RACH occasions (ROs), and wherein the plurality of ROs is available for a fixed time duration from a reference point. The method further comprises, mapping, by the at least one first node, the at least one SSB index to at least one valid RO from the plurality of ROs. The method further comprises, transmitting, by the at least one first node, a RACH preamble in a valid RO from the at least one valid RO.

[0008] In another embodiment, the present disclosure provides a method for random access procedure (RACH) in a wireless communication system. The method comprises, transmitting, by at least one second node, at least one of a synchronization signal block (SSB) burst and at least one system information block (SIB). The method further comprises, configuring, by the at least one second node, at least one first SSB index and at least one RACH configuration, wherein the at least one first SSB index represents at least one SSB of the SSB burst, wherein the at least one RACH configuration configures a plurality of RACH occasions (ROs), and wherein the plurality of ROs is available for a fixed time duration from a reference point. The method further comprises, receiving, by the at least one second node, at least one RACH preamble in at least one valid RO from a plurality of valid ROs.

[0009] The above summary is provided merely for the purpose of summarizing some exemplary embodiments to provide a basic understanding of some aspects of the present disclosure. Accordingly, it will be appreciated that the above-described embodiments are merely examples and should not be construed to narrow the scope or spirit of the present disclosure in any way. It will be appreciated that the scope of the present disclosure encompasses many potential embodiments in addition to those here summarized, some of which will be further described below. Other features, aspects, and advantages of the subject will become apparent from the description, the drawings, and the claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Having thus described the embodiments of the disclosure in general terms, reference now will be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

[0011] Fig. 1 illustrates a schematic overview of the wireless communication network according to the embodiments described herein;

[0012] Fig. 2 illustrates block diagram of the Time domain configuration of RACH occasions according to an embodiment of the present disclosure;

[0013] Fig.3 illustrates block diagram of the SSB-RO mapping in 5G-NR according to an embodiment of the present disclosure;

[0014] Fig. 4 illustrates block diagram of the RACH association period and the RACH association pattern period according to an embodiment of the present disclosure;

[0015] Fig.5 illustrates block diagram of the ON demand SSB / SIB1 for WUS Common for the burst according to an embodiment of the present disclosure;

[0016] Fig. 6 illustrates block diagram of the ON demand SSB / SIB1 for Beam specific WUS according to an embodiment of the present disclosure;

[0017] Fig. 7 illustrates block diagram of the Beam based periodicity for SSB / SIB1 according to an embodiment of the present disclosure;

[0018] Fig.8 illustrates block diagram of the impact of ON demand SSB / SIB1 on RACH according to an embodiment of the present disclosure;

[0019] Fig.9 illustrates block diagram of the valid duration for ROs in case of ON demand SSB / SIB1 according to an embodiment of the present disclosure;

[0020] Fig. 10 illustrates another block diagram of the valid duration for ROs in case of ON demand SSB / SIB1 according to an embodiment of the present disclosure;

[0021] Fig.11 illustrates block diagram of the impact of ON demand SSB / SIB1 with beam specific WUS on RACH according to an embodiment of the present disclosure;

[0022] Fig.12 illustrates another block diagram of the impact of ON demand SSB / SIB1 with beam specific WUS on RACH according to an embodiment of the present disclosure;

[0023] Fig.13 illustrates another block diagram of the impact of ON demand SSB / SIB1 with beam specific WUS on RACH according to an embodiment of the present disclosure;

[0024] Fig.14 illustrates another block diagram of the impact of ON demand SSB / SIB1 with beam specific WUS on RACH according to an embodiment of the present disclosure;

[0025] Fig.15 illustrates another block diagram of the impact of ON demand SSB / SIB1 with beam specific WUS on RACH according to an embodiment of the present disclosure;

[0026] Fig.16 illustrates the components that may be employed in a user equipment (UE), a base station respectively, and configured to support wireless communications in accordance with an embodiment of the present disclosure;

[0027] Fig. 17 illustrates a method of random-access procedure in wireless communication system in accordance with an embodiment of the present disclosure;

[0028] Fig. 18 illustrates another method of random-access procedure in wireless communication system in accordance with an embodiment of the present disclosure;

[0029] A more complete understanding of the present invention and its embodiments thereof may be acquired by referring to the following description and the accompanying drawings. DETAILED DESCRIPTION OF THE INVENTION

[0030] The detailed description set forth below in connection with the appended drawings is intended as a description of various embodiments of the present invention and is not intended to represent the only embodiments in which the present invention may be practiced. Each embodiment described in this invention is provided merely as an example or illustration of the present invention, and should not necessarily be construed as preferred or advantageous over other embodiments. The detailed description includes specific details for the purpose of providing a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details.

[0031] Some embodiments of the present disclosure now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all, embodiments of the disclosure are shown. Indeed, embodiments of the disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein, rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.

[0032] As used herein, the term “comprising” means including but not limited to and should be interpreted in the manner it is typically used in the patent context. Use of broader terms such as comprises, includes, and having should be understood to provide support for narrower terms such as consisting of, consisting essentially of, and comprised substantially of.

[0033] The phrases “in one embodiment,” “according to one embodiment,” “in some embodiments,” and the like generally mean that the particular feature, structure, or characteristic following the phrase may be included in at least one embodiment of the present disclosure, and may be included in more than one embodiment of the present disclosure (importantly, such phrases do not necessarily refer to the same embodiment).

[0034] The word “example” or “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other implementations.

[0035] Embodiments herein are described within the context of 5G NR radio technology. It is to be appreciated that the problems and solutions mentioned herein apply equally to wireless access networks and UEs that use different access technologies and standards. NR is used as an example technology where embodiments are appropriate, and include NR in the description is therefore very valuable for understanding the problem and finding solutions to it. In particular, embodiments are equally applicable to 3GPP LTE, or 3GPP LTE plus NR integration.

[0036] Further, many aspects are described in terms of sequences of actions to be performed by, for example, elements of a computing device. It will be recognized that various actions described herein can be performed by specific circuits (e.g., application specific integrated circuits (ASICs)), by program instructions being executed by one or more processors, or by a combination of both. Additionally, the sequence(s) of actions described herein can be considered to be embodied entirely within any form of non- transitory computer-readable storage medium having stored therein a corresponding set of computer instructions that, upon execution, would cause or instruct an associated processor of a device to perform the functionality described herein. Thus, the various aspects of the disclosure may be embodied in a number of different forms, all of which have been contemplated to be within the scope of the claimed subject matter.

[0037] As used herein, the terms “user equipment” (UE) and “base station” are not intended to be specific or otherwise limited to any particular radio access technology (RAT), unless otherwise noted. In general, a UE may be any wireless communication device (e.g., a mobile phone, router, tablet computer, laptop computer, tracking device, wearable (e.g., smartwatch, glasses, augmented reality (AR) / virtual reality (VR) headset, etc.), vehicle (e.g., automobile, motorcycle, bicycle, etc.), Internet of Things (IoT) device, etc.) used by a user to communicate over a wireless communications network. A UE may be mobile or may (e.g., at certain times) be stationary, and may communicate with a radio access network (RAN). Generally, UEs can communicate with a core network via a RAN, and through the core network the UEs can be connected with external networks such as the Internet and with other UEs. Of course, other mechanisms of connecting to the core network and / or the Internet are also possible for the UEs, such as over wired access networks, wireless local area network (WLAN) networks (e.g., based on IEEE 802.11, etc.) and so on.

[0038] A base station may operate according to one of several RATs in communication with UEs depending on the network in which it is deployed, and may be alternatively referred to as an access point (AP), a network node, a NodeB, an evolved NodeB (eNB), a New Radio (NR) Node B (also referred to as a gNB or gNodeB), etc.

[0039] The detailed description includes specific details for the purpose of providing a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details.

[0040] Fig.1 is a schematic overview illustrating a wireless communication network (100) in accordance with an embodiment of the present disclosure. The wireless communication network (100) comprises one or more Radio Access Networks (RANs) and one or more Core Networks (CNs). A single core network (106) is illustrated in Fig. 1 for the purpose of simplicity and as an example. The wireless communication network (100) may implement one or more of different technologies, such as W-Fi, LTE, LTE-Advanced, FifthGeneration (5G), WCDMA, Global System for Mobile communications / Enhanced Data rate for GSM Evolution (GSM / EDGE), Worldwide Interoperability for Microwave Access (WiMAX), or Ultra Mobile Broadband (UMB). The following embodiments pertain to current technological advances that are especially relevant in the context of 5G, but they may also be used to further the advancement of currently in use wireless communication systems like WCDMA and LTE.

[0041] In the wireless communication network (100) as illustrated in Fig. 1, wireless devices e.g. a UE (102a-102d) such as a mobile station, a non-access point (non-AP) STA, a STA, a user equipment (UE) and / or a wireless terminal, communicate via one or more Access Networks (AN), e.g. RANs, to one or more CNs. It is to be understood that “UE” is a non- limiting term which means any terminal, wireless communication terminal, user equipment, Machine Type Communication (MTC) device, Device to Device (D2D) terminal, or node e.g. smart phone, laptop, mobile phone, sensor, relay, mobile tablets or even a small base station capable of communicating using radio communication with a network node within the geographical area (1, 2, 3) served by one or more base station (BS) (104a-104c).

[0042] In an embodiment, the wireless communication network (100) comprises one or more radio network nodes (RAN) (104a-104c) providing coverage over geographical areas (1, 2 and 3) of a RAT, such as NR, LTE, WiMAX or the like. The radio network nodes or the base stations (104a-104c) may be a transmission and reception point e.g. a radio network node such as a Wireless Local Area Network (WLAN) access point or an Access Point Station (AP STA), an access node, an access controller, a base station, e.g. a radio base station such as a NodeB, an evolved Node B (eNB, eNode B), a gNodeB (gNB), a base transceiver station, a radio remote unit, an Access Point Base Station, a base station router, a transmission arrangement of a radio base station, a stand-alone access point or any other network unit or node capable of communicating with a UE within the area served by the network nodes depending e.g. on the RAT and terminology used. The radio network nodes communicate with the UE in form of downlink (DL) transmissions to the one or more UEs and Uplink (UL) transmissions from the one or more UE.

[0043] The present disclosure describes the initial access procedure that supports various adaptation of SSB and SIB1. The present disclosure details the configurations required and behaviour of various nodes in the network for efficient implementation of the procedure.

[0044] Initial Access procedure is a sequence of processes by which a UE establishes a connection with the BS and the network. The procedure enables UE to acquire downlink (DL) and uplink (UL) synchronization and obtain essential information (also known as system information) to establish and maintain connection with network

[0045] The Synchronization Signal Block (SSB) is a periodic message broadcasted by the BS to enable the UEs to acquire DL synchronization and to convey first set of system information to the UE. The UE, when needed, searches for SSB transmitted in a predefined time and frequency locations (also known as synchronization raster). The SSB comprises of primary synchronization signal (PSS), secondary synchronization signal (SSS) and physical broadcast channel (PBCH) comprising of the master information block (MIB). The PSS and SSS signals are used by the UE to obtain the cell identity, obtain the frame boundary and also can be used to measure information about the channel, whereas the MIB is used by the UE to obtain crucial initial broadcast information like the frame information, the scheduling information for control information, etc. The BS broadcasts control information within the scheduled set of resources (also known as CORESET0) and it provides scheduling information for system information block 1 (SIB1), which provides essential information about the cell and necessary configurations to perform various operations to latch on to the cell. E.g., information about the set of SSB associated with the cell, information about other system information blocks transmitted in the cell, configuration to perform random access channel (RACH) procedure, the DL / UL transmission pattern of the cell, etc.

[0046] RACH procedure is an essential part of wireless communication systems, and it plays a significant role in acquiring UL synchronization with the network, obtain specified ID for the radio access communication, etc. The RACH procedure is the first point of contact or the front door for the UE to access the network when it is powered on or after a period of inactivity. Further, the UE initiate the RACH procedure for beam failure recovery (BFR), to demand other system information blocks, handover, etc.

[0047] The RACH procedure in 5G NR is broadly classified into two types: contention- based RACH procedure (CB-RACH) and contention free RACH procedure (CF-RACH). In CB-RACH, the UE randomly selects a random-access preamble from a pool of preambles configured and transmit the selected preamble to the BS in certain time frequency resources. The pool of preambles and the time frequency resources are determined by the UE based on RACH configuration provided in SIB1 and the measurement of SSBs by the UE. The timefrequency resource for transmitting RACH preamble is also known as RACH occasions (RO). The pool of preambles is common for a set of UEs and can lead to contention if multiple UEs select the same preamble from the pool and transmit in same RO. Hence the procedure is termed CB-RACH. Using the RO in which the physical random-access channel (PRACH) is received, the BS determines information about the SSB beam selected by the UE, the propagation delay with the UE, timing misalignment at the UE, etc. and sends a response called MSG2, also known as random access response (RAR). The MSG2 consists of several critical information, such as the time advance (TA) command for timing adjustment, the RAPID (random access preamble ID) matching the preamble sent by the UE, an initial UL grant for the UE, a temporary radio network identifier called random access radio network temporary identifier (RA-RNTI) to the UE, etc.

[0048] All the UEs that have transmitted a preamble will wait for MSG2 in a preconfigured set of resources, where the configuration for RAR window is provided to UE in SIB1. After receiving MSG2 and performing the required timing adjustment, the UE transmits MSG3 using the UL grant received in MSG2. The MSG3 is transmitted after applying TA and in physical UL shared channel (PUSCH). The MSG3 contains the UE identity, C-RNTI if the UE was previously connected in the network or identity provided by the core network. In the case of contention, multiple UE transmit MSG3 in same resource. However, the BS decode only one MSG3 and sends MSG4 for contention resolution along with the identity of the UE contained in decoded MSG3. The UE compare identity received in MSG4 with identity transmitted in MSG3 and report RACH success only when a match is found. E.g., if UE has transmitted C- RNTI in MSG3 and received MSG4 on control channel addressed by C-RNTI. Since C-RNTI is unique, only intended UE will decode MSG4.

[0049] In NR, the SSB is transmitted in multiple beams known as SSB burst set. In frequency range 1 (FR1), the SSB burst set can have a maximum of 8 beams, whereas in frequency range 2 (FR2), the SSB burst set can have up to 64 beams. The actual SSBs transmitted in an SSB burst set is indicated to the UE using information element (IE) in SIB1. ssb-PositionsInburst indicate the time domain position of transmitted SSB in an SSB burst set. The ssb-PositionsInburst has following fields: groupPresence and inOneGroup.

[0050] In NR, the SSBs can be grouped into 8 groups and each group can have 8 SSBs each. groupPresence bit string of length 8 indicates which groups of SSBs are present out of 8 groups. Value 0 in the bitmap indicates that the corresponding SS / PBCH group is not presentwhile value 1 indicates that the corresponding SS / PBCH group is present. This bit of string is present only in the case of FR2, where the total number of SSBs is larger than 8. inOneGroup bit string of length 8 indicates which SSBs are present within a group. Value 0 in the bitmap indicates that the corresponding SS / PBCH block is not transmitted while value 1 indicates that the corresponding SS / PBCH block is transmitted. Further, the first / leftmost bit corresponds to SS / PBCH block index 0, the second bit corresponds to SS / PBCH block index 1, and so on.

[0051] The UE measure multiple beams in the SSB burst set, and identifies the best beam based on the measurement. Further, the UE determines the RACH preamble and RO corresponding to the best beam. The configuration to select the best beam, determine RO and map SSB with the RO are provided to UE in SIB1, using IE RACH-ConfigCommon. The RACH-ConfigCommon use the fields rsrp-thresholdSSB, totalNumberOfRA-Preambles and ssb-perRACH-OccasionAndCB-PreamblesPerSSB to select the best beam, determine RO and map SSB with the RO.

[0052] rsrp-thresholdSSB field configures the minimum reference signal received power (RSRP) value that an SSB beam should have. The UE determine RSRP value corresponding to multiple SSB beams received, compare the RSRP values with the threshold configured and select the SSB beam with RSRP value crossing threshold as the best beam. If none of the SSB beam crosses the threshold configured, then the UE select randomly one beam from the burst set.

[0053] totalNumberOfRA-Preambles field indicate the total number of preambles per PRACH occasion which are available for both the CB-RACH and CF-RACH. In NR, a maximum of 64 preambles can be configured per RO and these preambles are divided into three groups: for CB-RACH, for CF-RACH and for other purpose. The other purpose include preamble for requesting other system information blocks. E.g., if totalNumberOfRA- Preambles=50 then out of 64 preambles, 50 are available for CB-RACH and CF-RACH.

[0054] ssb-perRACH-OccasionAndCB-PreamblesPerSSB field conveys two parameters. The first parameter indicates the number of SSBs sharing a RO. E.g., value of oneEighth corresponds to one SSB associated with 8 RACH occasions, value Four corresponds to 4 SSBs sharing a RACH occasion and so on. The second parameter indicates the number of contention based preambles per SSB per valid RACH occasion. E.g. value n4 corresponds to 4 contentionbased preambles per SSB in a RO, value n8 corresponds to 8 contention based preambles per SSB in a RO, and so on.

[0055] Using the values indicated by totalNumberOfRA-Preambles and ssb-perRACH- OccasionAndCB-PreamblesPerSSB the number of CB preambles per RO and number of CF preambles can be computed. E.g., if ssb-perRACH-Occasion = 1 / 2 and CB-PreamblesPerSSB = 40 then each SSB beam span across 2 RO and 40 CB preambles are available to an SSB beam in a valid RO. Therefore, a total of 80 contention based preambles available to each SSB beam. Further, in a RO the difference between value indicated by totalNumberOfRA-Preambles and number of preambles available for CB-RACH gives the number of preambles available for CF- RACH. E.g., if totalNumberOfRA-Preambles=50 and 40 preambles are for CB-RACH then remaining 10 preambles for CF-RACH. In another e.g., if totalNumberOfRA-Preambles=50 and ssb-perRACH-OccasionAndCB-PreamblesPer SSB = (2, n24) then, a total of 50 preambles are available for RACH, two SSBs will share a RO and n24 implies 24 preambles / SSB in a RO. Therefore, total number of CB preambles in a RO = 2 SSB / RO×24 preambles / SSB=48 Preambles. Remaining 2 preambles, out of total 50, are for contention free RACH. In general, the total number of CB preambles per RO is given by ^^^^^^^^^^^^^^^^^^^^^^ / ^^^^ = (^^^^^^^^^^^^^^^^^^^^^^ / ^^^^^^).^^^^^^(1, ^^^^^^ / ^^^^)

[0056] Fig.2 illustrates a block diagram of the time domain allocation of RACH occasions in accordance with an embodiment of the present disclosure. prach-Configurationindex field indicate the time domain position of the ROs. The indicated value points to a row in one of predefined look up tables. The table is selected based on the frequency range and paring of spectrum. The indicated row in the selected table provides information such as preamble format to use (e.g., short or long preamble), the frame in which RO is present (i.e., even frame or odd frame), subframe / slots in which RO is present, the number of slots having RO in a subframe, number of RO within each slot, starting symbol of RO and duration of RO. E.g., prach- Configuration / index indicates the following values: x = 2, y = 1, subframe number = (4, 9), PRACH slots within subframe = 2, PRACH occasion within PRACH slot = 3, PRACH duration = 4, and starting symbol = 0. System frame number satisfying condition, n_SFN mod x = y, only has RO. Applying x and y in formula only odd frames will have ROs. Field subframe number = (4, 9) implies subframes 4 and 9 within odd frame has RO. Further, each subframe has 2 slots, each slot has 3 ROs starting from symbol 0 and each RO is of duration 4 symbols. msg1-FDM specifies the number of ROs which are multiplexed in the frequency domain. E.g.,msg1-FDM=4 implies 4 ROs are multiplexed in the frequency domain. msg1-FrequencyStart indicate the frequency domain position of the ROs. The field indicate the position of the lowest PRB belonging to the first RO. The indication is using a frequency offset with respect to starting PRB of the channel bandwidth. The number of PRBs in a RO depends on sub carrier spacing (SCS) of PUSCH, SCS of PRACH and length of the RACH preamble. E.g., For RACH SCS = 15 KHz and short preamble of 139 subcarriers, the preamble occupied BW = 2085 KHz. For SCS of PUSCH = 30 KHz, number of PRBs occupied by preamble = 2085 KHz / (12×30 KHz) = 6 PRBs.

[0057] NR RACH preamble sequence is based on Zadoff Chu sequence. The reason for choosing Zadoff Chu is due to its favourable properties, including constant amplitude before and after DFT operation, zero cyclic autocorrelation and low cross correlation. The configuration for generating RACH preamble in the ROs is given by RACH-ConfigCommon. prach-RootSequenceIndex field configure the length of the preamble (L=839 or 139 or 571 or 1151) and the logical index of the root sequence to the UE. The value of L depends on the coverage of the cell. E.g., L=139 for smaller coverage and L=839 for large coverage. The range of the logical index depends on the value of L (0 to L-2). Mapping from logical index to sequence number is predefined in standards. restrictedSetConfig field mitigate the impact of Doppler frequency offset in the case of high mobility scenario. The restricted set configures higher value of cyclic shift for generating the RACH preamble from the root sequence, there by skipping some of the possible options for RACH preamble. Therefore, restrictedSetConfig increases the separation between preambles and hence more resistance to frequency offsets. For FR1 (frequency <6GHz), there are three types of restricted sets: Unrestricted set, restricted set type A and restricted set type B. Unrestricted sets are intended to use with frequency offset which do not exceed half of SCS. Restricted sets type A are intended to use with frequency offset which do not exceed the SCS. Restricted sets type B are intended to use with frequency offset which do not exceed twice of the SCS. For FR2, there are no restricted sets because FR2 uses short preamble formats and restricted sets are applicable for long preamble format only.

[0058] zeroCorrelationZoneConfig field configure the value of cyclic shift, to apply on a root sequence, for the restricted set configured by restrictedSetConfig. The value of cyclic shift corresponding to the value indicated by zeroCorrelationZoneConfig for each restricted set type is predefined in the standard. In general, the cyclic shift increases with high value of zeroCorrelationZoneConfig. Similarly, for the same value of zeroCorrelationZoneConfig, thevalue of cyclic shift is smaller for unrestricted set and increases for restricted sets type A, followed by restricted sets type B.

[0059] The UE generates the RACH preamble by applying a cyclic shift to the root sequence, indicated by prach-RootSequenceIndex, where the cyclic shift is a function of PRACH preamble index, prach-RootSequencelndex, zeroCorrelationZoneConfig and restrictedSetConfig. The UE generate 64 preambles in each RO. If 64 preambles cannot be generated from the root sequence, indicated, then the UE increment the sequence number to obtain new root sequence and cyclic shift is applied to the new root sequence until getting 64 preambles. Same set of root sequences and cyclic shift apply for all ROs in a cell. Therefore, the 64 preambles remain the same for all ROs across time and frequency domains in a cell. Neighbouring cell will be assigned a different root sequence.

[0060] Fig.3 illustrates block diagram of the SSB-RO mapping in 5G-NR according to an embodiment of the present disclosure. Once the UE has information about the SSBs present in a burst, the set of RACH preambles and information about the ROs, the next step is to identify the RO corresponding to the SSB beams measured and determine the RO corresponding to the selected SSB beam. The SS / PBCH block indices provided by ssb-PositionsInBurst are mapped to valid ROs in the following order: • First, in increasing order of preamble indices within a single RO • Second, in increasing order of frequency resource indices for frequency multiplexed ROs • Third, in increasing order of time resource indices for time multiplexed ROs within a RACH slot • Fourth, in increasing order of indexes for PRACH slots.

[0061] As illustrated in Fig.3, the SSB burst comprises a total of 4 SSB beams of which 3 SSBs are active. Therefore, the ssb-PositionsInBurst indicate a bit map “1101” indicating SSB index 3 is not active. The SIB1 is transmitted only for active SSB beams and is transmitted using the same beam used for transmission of corresponding SSB. Fig.3 also illustrate the set of ROs configured by RACH-Configcommon in SIB1 and mapping of the active SSB beamswith the configured ROs. In figure, msg1-FDM=2 so that 2 ROs are FDMed in frequency and SSB per RO is ½ so that each SSB occupies 2 ROs.

[0062] Fig.4 illustrates a block diagram of the RACH association period and the RACH association pattern period according to an embodiment of the present disclosure. The timing relations has been defined in NR for RACH configuration and associated procedures. RACH configuration period is the time duration for which time domain configuration provided for RACH, in prach-Configuration / index, get repeated. E.g., if x and y provided in prach- Configurationindex is 2 and 1, respectively, then only odd system frames have ROs. Therefore, the RACH configuration period is 20 ms. The RACH association period is the time duration for mapping SS / PBCH block indexes to ROs is the smallest number of RACH configuration period, from a predefined set, such that all SSB indices, provided in ssb-PositionsInburst, are mapped at least once to the PRACH occasions. The possible number of PRACH configuration periods that can be counted in RACH association period is predefined in NR standards and is given in Table 1, below. RACH Configuration RACH Association Period (In Period (ms) terms of number of PRACH Configuration Periods) 10 {1,2,4,8,16} 20 {1,2,4,8} 40 {1,2,4} 80 {1,2} 160 {1} Table 1: Possible set of values for RACH association period

[0063] In an example, if there are 32 SSB beams, SSB / RO = 2 and 48 ROs within a 20 ms PRACH configuration period, then a total of 16 ROs are needed to cover all the SSBs. Since a single RACH configuration period has 48 ROs, each SSB can be mapped 3 times within a RACH configuration period. Therefore, RACH association period is 1 in this case.

[0064] In another example, if there are 64 SSB beams, 1 SSB / RO and 24 ROs within a 20 ms RACH Configuration Period then, a total of 64 ROs are needed to map all SSBs at least once. Therefore, 3 RACH configuration periods are needed to get the 64 ROs. However, the predefined set of values for association period does not include 3. Therefore, association period is considered as 4 RACH configuration periods, having a total of 96 ROs. Since there are 64 SSB beams, 64 ROs are used by SSB beams, out of 96 ROs, and the remaining 32 are unused.

[0065] The number of ROs in a RACH configuration period varies depending on the configuration of high priority signals and channels. E.g., if a configuration for SSB overlaps with RACH configuration period, then ROs within that period are not counted as valid ROs. Similarly, if at least one symbol of a RO is configured as DL by configuration, then the RO is not considered as valid. Therefore, the number of configuration periods within a RACH association period keeps on varying.

[0066] The RACH association pattern period is the time duration that includes one or more association periods and is determined so that a pattern between ROs and SSB indices repeats at most every 160 msec. The ROs that are not associated with SSB indices after an integer number of association periods, if any, are not used for RACH transmissions. E.g., if there are 8 SSB beams and 1 SSB / RO, then association period should have 8 ROs. Further, RACH configuration period is assumed to be 10 ms and SSB periodicity is assumed to be 80 ms. Due to configuration for high priority signals and DL pattern the number of RO varies across RACH configuration period as: no valid RACH occasions are assumed in a frame having SSBs, 8 ROs in an even numbered frame and 6 ROs in an odd numbered frame. The first RACH association period comprises of 4 RACH configuration periods with 20 ROs, where each SSB is mapped twice (8 × 2 = 16 ROs) and the remaining 4 ROs are wasted. The second RACH association period indicated comprises 1 RACH configuration period with 8 ROs, where each SSB is mapped once. The mapping continues in a similar manner. The last association period comprises 14 ROs and each of 8 SSBs is mapped once (8 × 1 = 8 ROs) and the remaining 6 ROs are wasted. Similarly, the last RACH configuration period in 160 ms window has 6 ROsand it cannot be mapped to 8 SSBs. Therefore, ROs in the last RACH configuration period remain unused.

[0067] The adaptation of always ON signals (E.g., SSB / SIB1) contributes significantly to network energy saving. Currently in NR, the SSB is transmitted periodically, with periodicity value chosen from a set of predefined values in the range 5 ms to 160 ms. Further, the SIB1 is transmitted with same periodicity as SSB and the BS start monitoring for RACH in the ROs configured by SIB1. Currently, these set of procedures is mandatory at BS irrespective of the fact whether that UE is performing measurement and trying to connect to network or not. However, these sets of procedures are required only when a UE is trying to connect to the network. Further, a higher value of periodicity is preferred from energy saving perspective so that the BS need to transmit SSB less frequently. However, in case of higher value of periodicity, the UE must wait longer to get an SSB leading to an increase in latency in accessing the network. Further, the actual value of periodicity required depends on UE arrival rate, which is random. Therefore, following methods can be used to save energy at BS and ensure efficient utilization of the transmitted signal.

[0068] In one method, the BS transmits SSB periodically and start monitoring for wake- up signal (WUS) from the UE. Here, the SIB1 transmission and monitoring ROs for PRACH are performed only after getting a request signal from the UE. The UE, trying to connect to the network, monitor for SSB, receive SSB, and measure SSB. In one option, the UE transmits the WUS directly after measurement, whereas in another option the UE transmits the WUS only if the parameter measured using SSB is greater than a certain threshold. In this method, the configuration for WUS can be either predefined or given in SSB.

[0069] In another method, the BS monitor for the WUS and transmit SSB only if a WUS is received. Here the configuration for the WUS can be predefined or given by the BS. In the latter case, the BS can give the WUS configuration using another cell in which the UE is connected or transmits the WUS configuration periodically. In case of periodic transmission of the WUS configuration, the UE has to blindly monitor for the WUS configuration. In case of predefined WUS configuration, the UE can transmit a predefined sequence, as request for SSB / SIB1, and the BS can perform blind monitoring for the sequence.

[0070] Fig.5 illustrates block diagram of the ON demand SSB / SIB1 for WUS Common for the burst according to an embodiment of the present disclosure. The BS receive the WUSand transmit the entire burst of SSB or SIB1, where SSB indices 1, 2 and 4 are active within the SSB burst and the entire SSB burst is transmitted in response to reception of a WUS. Here, the WUS is a request for transmission of SSB / SIB1 burst.

[0071] Fig. 6 illustrates block diagram of the ON demand SSB / SIB1 for Beam specific WUS according to an embodiment of the present disclosure. In this method, the BS receives a WUS, determine the content of the SSB / SIB1 burst (i.e., SSB / SIB1 indices to be included in the burst) and transmits SSB / SIB1 burst. Here, the WUS can request SSB / SIB1 transmission in specific beam or the BS can derive the content based on the reception of the WUS (E.g., angle of reception of WUS), where the BS receives a WUS in the first instant, determine the content of the SSB burst as SSB index1 and transmits SSB burst. In the second instant the BS determine the content of SSB burst as SSB index 1 and SSB index 4. Therefore, the SSBs / SIB1s within the burst can change every time in this method. However, the advantage is that the BS utilizes the information from the WUS to avoid unnecessary broadcasting of SSB / SIB1.

[0072] The parameters used for transmission of SSB / SIB1 can be adapted based on network conditions to reduce the number of transmissions and to improve utilization of the transmitted SSB / SIB1. The utilization of the transmitted SSB is dependent on user arrival rate, which can vary across the region of coverage of the BS. Transmitting SSB / SIB1 at same periodicity in all directions, irrespective of the characteristic of the region, is suboptimal and can lead to non-utilization of the transmitted SSB / SIB1s.

[0073] Fig. 7 illustrates block diagram of the Beam based periodicity for SSB / SIB1 according to an embodiment of the present disclosure. In beam based periodicity for SSB / SIB1, separate periodicity can be configured for each SSB within a burst or for group of SSBs within burst to improve utilization. E.g., lower periodicity can be configured for an SSB beam pointing towards a mall or stadium during active hours compared to an SSB beam pointing to lake / highway. As illustrated in Fig.7, where an SSB burst comprises 4 beams, of which SSB indices 1 and 4 are present in every SSB burst, whereas SSB indices 2 and 3 are transmitted in alternate SSB bursts. Therefore, SSB indices 2 and 3 are transmitted with periodicity which is twice the periodicity of transmission of SSB indices 1 and 4.

[0074] In Adaptation of SSBs within a burst, the active SSB / SIB1s within an SSB / SIB1 burst can change across bursts. In one option more than one pattern for active SSB / SIB1s in aburst can be configured to the UE, of which one active pattern can be indicated explicitly. In another option the active SSB / SIB1s in the burst can be configured to the UE in SIB1.

[0075] The adaptation of the common signals / channels as detailed above however impacts the SSB RO mapping. The present disclosure details below the impacts and proposes various solutions to overcome the impacts.

[0076] Fig.8 illustrates block diagram of the impact of ON demand SSB / SIB1 on RACH according to an embodiment of the present disclosure. In 5G-NR, the RACH configuration provides a set of ROs which repeat periodically based on RACH configuration period and are mapped to periodically transmitted SSBs based on SSB-RO mapping rule. However, in case of ON demand SSB / SIB1, the SSB / SIB1 is transmitted only when WUS is received by the BS. Therefore, RACH occasions are needed and valid only when SSB and SIB1 transmission occurs. As illustrated in Fig. 8, where SSB indices 1, 2 and 4 are active in an SSB burst and full burst is transmitted once BS receives a WUS. The Fig. 8 also illustrates the mapping of SSBs in the burst to configured ROs in case of SSB / RO=1 / 2 (Each SSB is mapped to 2 ROs). In Fig. 8, the transmission of SSB and SIB1 occurs only in second SSB Burst transmission occasion and is skipped in first and third transmission occasions because of the absence of WUS. Therefore, the ROs associated with SSB burst on the second transmission occasion need to be active and remaining ROs can be considered inactive by both UE and BS. The BS can skip monitoring the inactive ROs for PRACH. Also, the UE will not map SSBs to inactive ROs and skip transmitting PRACH in inactive ROs.

[0077] In one method in determining the active ROs in case of ON demand SSB / SIB1, all the ROs configured are considered as active and legacy SSB-RO mapping is followed. In another method, ROs are valid until fixed duration and remaining ROs are considered inactive. In one option the fixed duration can be counted from start or end of the last SSB / SIB1 burst transmitted. In another option the fixed duration can be counted from the time instant in which WUS is transmitted. The duration can be an association period or integer multiple of association period or a time value or number of slots / symbols or number of repetitions of the RACH configuration period. E.g., along with x and y in PRACHConfigurationIndex, indicate number of repetitions or number of SFNs the configuration is valid. The duration can be predefined or indicated by the BS. In case of receiving another WUS within the valid duration, the duration gets extended.

[0078] Fig.9 illustrates block diagram of the valid duration for ROs in case of ON demand SSB / SIB1 according to an embodiment of the present disclosure, where an association period is considered as the valid duration for ROs. As shown in Fig.9, if a second WUS is received within valid duration of the RO corresponding to a first WUS, then the ROs in next valid duration is considered as valid. In Fig.9, a WUS2 is received in third transmission occasions, which is in between the valid duration corresponding to WUS1. Therefore, the valid duration is elongated by one association period or the ROs in next association period is also treated as active and the BS monitor them.

[0079] Fig. 10 illustrates another block diagram of the valid duration for ROs in case of ON demand SSB / SIB1 according to an embodiment of the present disclosure, where valid duration gets extended so that all SSBs are mapped. As shown in Fig.10, if a second WUS is received within valid duration of the RO corresponding to a first WUS, then the valid duration of ROs is extended such that all SSBs / SIB1s associated with second transmission occasion get enough active ROs to map. As illustrated in Fig.10, where WUS 2 is received in between the valid duration for WUS1. Here, the UE start SSB-RO mapping based on the immediate RO and its order within an association period. For the SSB burst corresponding to WUS1, the immediate RO is at the start of the association period. Therefore, the SSB-RO mapping follows the order {SSB index1, SSB index 2, SSB index 3 and SSB index 4}. i.e., SSB index1 is mapped followed by SSB index 2, SSB index 3 and so on. However, for the SSB burst corresponding to WUS2, the first RO is in the middle of association period, and it maps to SSB index 3. Therefore, SSB-RO mapping follows the order {SSB index 3, SSB index 4, SSB index 1, SSB index 2}, of which SSB index 3 and SSB index 4 are mapped to ROs within the valid duration and additional ROs are introduced to map SSB index 1 and SSB index 2.

[0080] In case of PRACH failure or not receiving RACH response in the configured monitoring period, the UE keeps retransmitting the PRACH with increased transmit power until RACH response is received successfully or a maximum retransmission attempt configured by the BS is reached. Defining valid duration for ROs can impact the PRACH retransmission, if the duration of active ROs is lesser than the RACH repetition duration or enough active ROs are not available for retransmission.

[0081] In one method, the BS configures the valid duration such that enough active ROs for PRACH retransmission is available. i.e., valid duration is determined based on number ofRACH repetition configured to the UE. In another method, if valid ROs are not available for retransmission then the UE retransmits WUS and reinitiates the initial access procedure.

[0082] In case of ON demand SSB / SIB1, the BS receive the WUS before transmission. Therefore, based on the number of WUS received, the BS knows the number of UEs trying to connect to the network or requesting for SSB / SIB1. Therefore, if BS receives number of PRACH preambles equal to number of WUS received, then the BS can treat the remaining ROs as invalid and skip monitoring those ROs for PRACH.

[0083] In another method, the BS provide RACH configuration dedicated for the received WUS. E.g., on receiving WUS1, the BS transmit SSB / SIB1 and configure a dedicated set of preambles in RACH configuration within SIB1. The UE, which transmitted the WUS1, will receive the RACH configuration and perform SSB-RO mapping based on the configuration. In case of receiving WUS2, the BS configures a second set of preambles, which are orthogonal to the one configured for WUS1.Therefore, the SSB-RO mapping is WUS specific and independent. The BS identify the mapping based on the preamble received.

[0084] In case of ON demand SSB / SIB1 with beam specific WUS, the BS determines the subset of SSB / SIB1 within the burst and transmit only those subsets. Therefore, the number of SSB / SIB1s and SSB / SIB1 indices present in the transmitted burst can change every time. The change in the pattern of SSB / SIB1 within the burst will impact the RACH process, especially the SSB RO mapping. The position and number of active ROs can change depending on the content of the SSB / SIB1 burst and can create discrepancies between BS and UE.

[0085] Fig.11 illustrates block diagram of the impact of ON demand SSB / SIB1 with beam specific WUS on RACH according to an embodiment of the present disclosure. As illustrated in Fig.11, the BS and UE assumes all or subset of SSBs / SIBs within the burst are present and map the SSBs to ROs. The UE determines the RO corresponding to the best SSB and transmit PRACH. The BS treat only those ROs which are mapped to active SSB / SIB1 in the burst as active and monitors only active ROs for PRACH. Here, the subset of the SSBs can be indicated to the UEs using ssb-PositionsInburst parameter in SIB1. The actual pattern of SSB / SIB1 within the burst (after adaptation) can be different from the parameter assumed for mapping. The advantage with this method is that the legacy parameters can be reused and frequent update in SIB1 content, to update the adapted pattern in burst, is not required. Fig. 11 illustrates the method, where the active SSB / SIB1 within the burst changes from time to time, however, theSSB-RO mapping assumes all SSB / SIB1 active in the burst. Also, SSB / RO=1 / 2 assumed in the mapping.

[0086] Fig.12 illustrates another block diagram of the impact of ON demand SSB / SIB1 with beam specific WUS on RACH according to an embodiment of the present disclosure. As illustrated in Fig.12, the BS indicate the pattern of SSB / SIB1 within the burst to the UE. E.g. update the parameter SSB-positionInburst in SIB1 for indicating the pattern. The ROs available until certain duration, which can be predefined or configured, (e.g., until the next SSB burst transmission occasion) is divided among the active SSB / SIB1 within the burst. The BS should ensure enough ROs within the duration to map the active SSBs in the burst. The division of ROs can be equal or unequal among the SSBs. The BS can configure how the ROs or preambles should be divided among the active SSB / SIB1. In one option, the BS indicate the preamble per SSB, and the UE calculate the total number of preambles in all the ROs for the duration and map it to active SSBs accordingly. In another option, the BS indicate the preamble per SSB, and the UE divides preamble in each RO among active SSBs based on the indication. The advantage with this method is that the active ROs are continuous, which increases the sleep time or inactivity period of the BS. Also, it reduces the delay at UE side in getting RO for the SSB. An e.g., is illustrated in Fig.12, where the duration is SSB periodicity. In the Fig 12, the first SSB burst has SSB index 1 and 4 actives. Also, two ROs are available between first and second SSB bursts. Therefore, the first available RO is mapped to SSB index1 and second RO is mapped to SSB index2.

[0087] Fig.13 illustrates another block diagram of the impact of ON demand SSB / SIB1 with beam specific WUS on RACH according to an embodiment of the present disclosure. As illustrated in Fig.13, the BS indicate the pattern of SSB / SIB1 within the burst to the UE along with order / priority with which it has to be mapped to ROs. As illustrated in Fig.13, where the first SSB burst contains only SSB index 2 and priority is 1. Therefore, BS indicate SSB- PositioninBurst=0100 and priority=0100. The UE maps the immediate RO available to SSB index 2. The second SSB burst has 2 SSBs, SSB index 1 and SSB index 4, of which SSB index 1 is mapped to immediate RO, whereas the SSB index 4 is mapped to an RO occurring after the third burst. In third burst, the SSB-PositioninBurst=1011, however, the priority is more for SSB index 4 as mapping for SSB index 4 in SSB burst 2 is pending. Therefore, in SSB burst 3 the priority=2-0-3-1. Therefore, the UE receiving SSB burst 3 maps SSB index 4 first followed by SSB index 1 and SSB index 3. The number of bits needed for indicating priorityis given by N*log2(M), where N is active SSBs in the burst and M is total number of SSBs in the burst. The advantage with this method is that the active ROs are continuous, which increases the sleep time or inactivity period of the BS. Also, it reduces the delay at UE side in getting RO for mapping to the SSB.

[0088] Fig.14 illustrates another block diagram of the impact of ON demand SSB / SIB1 with beam specific WUS on RACH according to an embodiment of the present disclosure. As illustrated in Fig. 14, the BS indicate the pattern of SSB / SIB1 within the burst and the SSBs for which RO mapping is pending from previous burst. As illustrated in Fig. 14, where SSB burst 1 has SSB index 1 and SSB index 4, of which SSB index 1 is mapped to the immediate RO and SSB index 4 is mapped to RO occurring after SSB burst 2. Therefore, the one SSB from SSB burst 1 is pending at the time of transmission of SSB burst 2. Therefore, the BS indicate SSB-Position-pending =0001 for the UEs receiving SSB burst 2, along with SSB- positionInburst=1011. The UE, receiving SSB burst 2, start SSB-RO mapping from SSB index 4, since SSB-Position-pending indicated 0001. For SSB burst 3, the SSB-positionInburst=1100 and SSB-Position-pending =1010, as SSB index 1 and SSB index 3 from SSB burst 2 is yet to be mapped. Therefore, the UE, receiving the SSB burst 3, starts SSB-RO mapping in the order of SSB index 1, SSB index 3 and SSB index 2. The number of bits needed for indicating pending SSB is M, where M is the total number of SSBs possible in the burst. Therefore, the number of additional bits needed here is less than the method 3. However, the the active ROs are continuous, which increases the sleep time or inactivity period of the BS. Also, it reduces the delay at UE side in getting RO for the SSB.

[0089] Fig.15 illustrates another block diagram of the impact of ON demand SSB / SIB1 with beam specific WUS on RACH according to an embodiment of the present disclosure. As illustrated in Fig.15, the BS indicate the pattern of SSB / SIB1 within the burst and an offset, where the offset indicates the number of ROs the UE has to skip before starting SSB-RO mapping. As illustrated in Fig. 15, where SSB burst 1 has SSB-positioninburst=1001 and offset=0, therefore, the UE start mapping for SSB index 1 in very first RO available followed by SSB index 4. For the SSB burst 2, SSB-positioninburst=1011 and offset=1, as one SSB from SSB burst 1 is yet to be mapped to RO. Therefore, the UE, receiving SSB burst 2, waits for one mapping occasion to start mapping SSBs in SSB burst 2. Similarly, for SSB burst 3, SSB- positioninburst=1100 and offset=3. Therefore, the UE receiving the SSB burst 3 waits for 3 mapping occasions to start SSB-RO mapping. The number of bits needed to indicate the offsetis log2(M), where M is the total number of SSBs possible in the burst. Therefore, the additional bits needed for indication is less compared to the method 3 and 4. The ROs are continuous in this method, but more ROs are needed for completing the mapping as mapping is done independently for each burst.

[0090] In yet another method of SSB-RO mapping in case of change in content of SSB / SIB1 burst, the RACH configuration can be specific for a received WUS or each SSB / SIB1 beam. E.g., separate preambles can be configured for each WUS occasion so that the UE can perform SSB-RO mapping independently for each SSB / SIB1 and the BS can identify the SSB-RO mapping based on the preamble. In one option, the BS can configure separate root sequence and cyclic shift to assign separate preambles. In another option, the BS can reuse the existing configuration for preambles, mentioned in section 2.2.1, and additionally indicate starting index of preamble and the number of preambles that are active. In that case, the UE generate the set of active preambles depending on WUS occasion or SSB index and select randomly one preamble from the set for transmitting PRACH. For e.g., on receiving a beam specific WUS1 for SSB index 1, the BS transmit the corresponding SSB with index 1 and configure a dedicated set of preambles in RACH configuration within SIB1. The UE, which transmitted WUS1 will receive the RACH configuration indicating a subset of the preambles for the SSB and select randomly one preamble from the subset for transmitting PRACH. In case of receiving WUS2, the BS configures a second set of preambles, which are orthogonal to the one configured for WUS1. Therefore, the SSB-RO mapping is per SSB / SIB1 or WUS and independent. Here, the number of preambles per SSB / SIB1 or WUS is reduced, which increases probability of contention. However, the SSB can be mapped to all ROs, as UE uses different preambles, which increases the number of ROs and reduces the contention probability. Further, the BS can compute the number of UEs trying to connect to network using the number of WUS received and can assign enough preambles so that probability of contention reduces.

[0091] Fig. 16 illustrates a block diagram depicting the components of a wireless communication system 1600 in accordance with an embodiment of the present disclosure. As shown in Fig.16, the UE 1602 may comprise a processor 1614, memory storing instructions 1612 and a transceiver circuitry comprising a transmitter 1616 and receiver 1618 configured to perform the methods herein. As shown in Fig.16, the BS 1604 may comprise a processor 1624,memory storing instructions 1622 and a transceiver circuitry comprising a transmitter 1626 and receiver 1628 configured to perform the methods herein.

[0092] Fig.16 in accordance with an embodiment of the present disclosure illustrates only one memory and processor. It is apparent to a skilled person in the art that a UE and BS may include one or more processors and one or more memories. The memory may also be referred to as a storage medium, a storage device, or the like. The memory may be disposed independent of the processor, or may be integrated with the processor. This is not to be accorded as a limitation of the embodiment described in this disclosure.

[0093] In an embodiment of this disclosure, an antenna (1610a-n, 1620a-n) and a radio frequency circuit that have a receiving and sending function may be considered as a transceiver unit of the terminal. The transceiver unit may also be referred to as a transceiver (including a transmitter and / or a receiver), a transceiver machine, a transceiver apparatus, or the like. The processing unit may also be referred to as a processor, a processing module, a processing apparatus, or the like. Optionally, a component configured to implement a receiving function in the transceiver unit may be considered as a receiving unit, and a component configured to implement a sending function in the transceiver unit may be considered as a transmitting unit. In other words, the transceiver unit includes the receiving unit and the transmitting unit. This is not to be accorded as a limitation of the embodiment described in this disclosure.

[0094] In some embodiments, the transceiver unit and the processing unit may be integrated together or may be disposed independently. In addition, all functions of the processing unit may be integrated into one chip for implementation. Alternatively, some functions may be integrated into one chip for implementation and some other functions are integrated into one or more other chips for implementation.

[0095] It should be understood that division of the modules of the foregoing apparatus is merely division of logical functions, and in actual implementation, all or some modules may be integrated into one physical entity, or may be physically separated. In addition, all of these modules may be implemented in a form of invoking software by a processor element, or all of these modules may be implemented in a form of hardware, or some modules are implemented in a form of invoking software by a processor element, and some modules are implemented in a form of hardware. For example, the receiving module may be a separately disposed processor element, or may be integrated into a chip of the foregoing apparatus for implementation. Inaddition, the receiving module may alternatively be stored in a memory of the foregoing apparatus in a form of program code, and a processor element of the foregoing apparatus invokes and executes a function of the foregoing receiving module. Implementation of other modules is similar to that of the receiving module. In addition, all or some of these modules may be integrated together, or may be implemented separately. The processor element described herein may be an integrated circuit and has a signal processing capability. In an implementation process, steps in the foregoing methods or the foregoing modules can be implemented by using a hardware integrated logical circuit in the processor element, or by using instructions in a form of software.

[0096] For example, the foregoing modules may be one or more integrated circuits configured to implement the foregoing method, for example, one or more application-specific integrated circuits (ASIC), or one or more microprocessors (DSP), or one or more field programmable gate arrays (FPGA), or the like. In another example, when one of the foregoing modules is implemented in a form of invoking program code by a processor element, the processor element may be a general-purpose processor, for example, a central processing unit (CPU) or another processor that can invoke the program code. For another example, the modules may be integrated together and implemented in a form of a system-on-a-chip (SOC).

[0097] All or some of the foregoing embodiments may be implemented by using software, hardware, firmware, or any combination thereof. When software is used to implement the embodiments, all or some of the embodiments may be implemented in a form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the procedures or functions according to embodiments of this application are all or partially generated. The computer may be a general-purpose computer, a dedicated computer, a computer network, or another programmable apparatus. The computer instructions may be stored in a computer-readable storage medium or may be transmitted from a computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions may be transmitted from a website, computer, server, or data center to another website, computer, server, or data center in a wired (for example, a coaxial cable, an optical fiber, or a digital subscriber line (DSL)) or wireless (for example, infrared, radio, or microwave) manner. The computer-readable storage medium may be any usable medium accessible by the computer, or a data storage device, for example, a server or a data center,integrating one or more usable media. The usable medium may be a magnetic medium (for example, a floppy disk, a hard disk, or a magnetic tape), an optical medium (for example, a DVD), a semiconductor medium (for example, a solid-state drive (SSD)), or the like.

[0098] Fig. 17 illustrates a method for random access procedure (RACH) in a wireless communication system in accordance with an embodiment of the present disclosure. The operations of method 1000 presented below are intended to be illustrative. In some implementations, method 1700 may be accomplished with one or more additional operations not described, and / or without one or more of the operations discussed. Additionally, the order in which the operations of method 1700 are illustrated in Fig. 17 and described below is not intended to be limiting.

[0099] According to an embodiment, the method 1700 may be implemented by one or more processors or modules illustrated and explained through Figs.1 and 16, therefore detailed explanation of the same is omitted here for the sake of brevity.

[0100] Step 1702 may include receiving, by at least one first node, at least one of at least one synchronization signal block (SSB) index, and at least one RACH configuration, wherein the at least one SSB index represents at least one SSB of an SSB burst, wherein the at least one RACH configuration indicates plurality of RACH occasions (ROs), and wherein the plurality of ROs is available for a fixed time duration from a reference point.

[0101] Step 1704 may include mapping, by the at least one first node, the at least one SSB index to at least one valid RO from the plurality of ROs.

[0102] Step 1706 may include transmitting, by the at least one first node, a RACH preamble in a valid RO from the at least one valid RO.

[0103] In an embodiment, receiving by the at least one first node is performed after transmitting a wake up signal (WUS).

[0104] In an embodiment, the configuration for transmitting the WUS is predefined in standards or preconfigured at the time of deployment.

[0105] In an embodiment, the at least one SSB index is determined based on at least one of: measurements on the WUS transmitted by the at least one first node; and content of the WUS.

[0106] In an embodiment, receiving by the at least one node further comprises receiving at least one of: at least one system information block (SIB); at least one SSB of the SSB burst; configuration for transmitting the WUS; active SSB indices of the SSB burst; periodicity of at least one SSB of the SSB burst; priority of each SSB index in the at least one SSB index; indication of availability of the plurality of ROs from the reference point for the fixed time duration; order of mapping each SSB index in the at least one SSB index; an SSB index from the at least one SSB index to start mapping; index of at least one second SSB for which the mapping is pending; number of at least one second SSB for which the mapping is pending; and start of the at least one valid RO.

[0107] In an embodiment, the start of the at least one valid RO comprises at least one of: the number of ROs from the plurality of ROs; and the number of time resources to skip before starting mapping for the at least one SSB index.

[0108] In an embodiment, the at least one RACH configuration further comprises: scheduling information of the plurality of ROs; minimum reference signal received power (RSRP) value for an SSB; total number of preambles for RACH; number of SSBs sharing an RO; number of preambles per SSB; number of ROs multiplexed in the frequency domain; at least one index from a predefined table; length of RACH preamble; at least one root sequence to generate the RACH preamble; and at least one cyclic shift to generate the RACH preamble.

[0109] In an embodiment, the active SSB indices within the SSB burst is dedicated for the WUS.

[0110] In an embodiment, the reference point is one of: start of the SSB burst; end of the SSB burst; start of at least one SIB; end of at least one SIB; start of first frame of a SIB modification period; and time instant of transmitting a WUS.

[0111] In an embodiment, the method further comprises: monitoring of RACH response in a window.

[0112] In an embodiment, the further comprises transmitting the RACH preamble in a second valid RO from the at least one valid RO, when the RACH response is not received within the window; and value of retransmission counter is less than maximum retransmission attempts.

[0113] In an embodiment, transmitting the RACH preamble in a second valid RO further comprises incrementing the retransmission counter.

[0114] In an embodiment, the window and the maximum retransmission attempts are received by the at least one first node.

[0115] In an embodiment, the method further comprises transmitting a WUS, when the at least one valid RO is not available.

[0116] In an embodiment, the valid RO corresponds to the best SSB.

[0117] In an embodiment, receiving the at least one SSB further comprises: computing the RSRP values corresponding to the at least one SSB; comparing the RSRP values with a minimum RSRP value configured; and selecting the best SSB with the RSRP value crossing the minimum RSRP value.

[0118] In an embodiment, mapping comprises at least one of: dividing one of the number of preambles and number of the at least one valid RO within the fixed time duration of the at least one first SSB index; and dividing the number of preambles in each RO from the at least one valid RO of the at least one first SSB index.

[0119] In an embodiment, the division is one of: equal; and based on at least one parameter configured by the at least one RACH configuration.

[0120] In an embodiment, receiving the index of the at least one second SSB for which the mapping is pending further comprises: determining at least one third SSB index, from the at least one SSB index, that matches with the index of at least one second SSB; and start mapping from the at least one third SSB index.

[0121] In an embodiment, receiving the number of at least one second SSB for which the mapping is pending further comprises: skipping or delaying the mapping for a number of ROs mapping to the at least one second SSB.

[0122] In an embodiment, mapping is in the order of at least one of: priority of each SSB index in the at least one SSB index; and increasing order of index of each SSB index in the at least one SSB index.

[0123] In an embodiment, receiving comprises at least one of: monitoring, by the at least one first node, for a predefined pattern and sequence; and transmitting one of a predefined pattern and a predefined sequence.

[0124] In an embodiment, the sequence is one of: primary synchronization sequence (PSS); and secondary synchronization sequence (SSS).

[0125] In an embodiment, receiving is performed in at least one of: at least one SIB; a connected cell; a primary cell; and an anchor cell.

[0126] In an embodiment, the at least one RACH configuration is dedicated for a WUS transmitted by the at least one first node.

[0127] In an embodiment, the fixed time duration is at least one of: predefined; and received by the at least one first node through signalling.

[0128] In an embodiment, the fixed time duration is one of: a portion of the RACH association period, wherein the portion is one of the first half of the RACH association period, first quarter of the RACH association period, first eighth of the RACH association period, or first sixteenth of the RACH association period; an integer multiple of the RACH association period; an integer multiple of RACH configuration period; and the time gap between two consecutive SSB bursts.

[0129] In an embodiment, the fixed time duration is within integer multiple of one of: RACH association period; and RACH association pattern period.

[0130] In an embodiment, the at least one valid RO is at least one of: non-overlapping with DL time resource; and non-overlapping with time resource configured for SSB.

[0131] Fig. 18 illustrates a method for random access procedure (RACH) in a wireless communication system in accordance with an embodiment of the present disclosure. The operations of method 1800 presented below are intended to be illustrative. In some implementations, method 1800 may be accomplished with one or more additional operations not described, and / or without one or more of the operations discussed. Additionally, the order in which the operations of method 1800 are illustrated in Fig. 18 and described below is not intended to be limiting.

[0132] According to an embodiment, the method 1800 may be implemented by one or more processors or modules illustrated and explained through Figs.1 and 16, therefore detailed explanation of the same is omitted here for the sake of brevity.

[0133] Step 1802 may include transmitting, by at least one second node, at least one of a synchronization signal block (SSB) burst and at least one system information block (SIB).

[0134] Step 1804 may include configuring, by the at least one second node, at least one first SSB index and at least one RACH configuration, wherein the at least one first SSB index represents at least one SSB of the SSB burst, wherein the at least one RACH configuration configures a plurality of RACH occasions (ROs), and wherein the plurality of ROs is available for a fixed time duration from a reference point.

[0135] Step 1806 may include receiving, by the at least one second node, at least one RACH preamble in at least one valid RO from a plurality of valid ROs.

[0136] In an embodiment, transmitting is performed after receiving at least one wake up signal (WUS).

[0137] In an embodiment, the configuration for the WUS is predefined in standards or preconfigured at the time of deployment.

[0138] In an embodiment, the at least one first SSB index is determined based on at least one of: at least one parameter measured on the WUS received; and content of the WUS received.

[0139] In an embodiment, the method further comprises: identifying, by the at least one second node, at least one second SSB index from the at least one first SSB index based on the at least one RACH preamble and the at least one valid RO.

[0140] In an embodiment, identifying the at least one second SSB index comprises: mapping the at least one first SSB index to the plurality of valid ROs; and identifying the SSB indices corresponding to the at least one valid RO.

[0141] In an embodiment, the reference point is one of: start of the SSB burst; end of the SSB burst; start of the at least one SIB; end of the at least one SIB; start of first frame of a SIB modification period; and time instant of transmitting a WUS.

[0142] In an embodiment, the fixed time duration is at least one of: predefined; configured by the at least one second node; portion of the RACH association period; an integer multiple of the RACH association period; an integer multiple of RACH configuration period; and the time gap between two consecutive SSB bursts.

[0143] In an embodiment, the portion is one of the first half of the RACH association period, first quarter of the RACH association period, first eighth of the RACH association period, or first sixteenth of the RACH association period.

[0144] In an embodiment, the fixed time duration is within integer multiple of one of: RACH association period; and RACH association pattern period.

[0145] In an embodiment, the plurality of valid ROs is at least one of: non-overlapping with DL time resource; and non-overlapping with time resource configured for SSB.

[0146] In an embodiment, the at least one second SSB index corresponds to the best SSB beam for the at least one first node.

[0147] In an embodiment, the method further comprises: receiving the WUS within the fixed time duration; and extending the fixed time duration.

[0148] In an embodiment, the method further comprises transmitting at least one of a second SSB burst and at least one second SIB.

[0149] In an embodiment, extending the fixed time duration is by one of: fraction of the fixed time duration; an integer multiple of the fixed time duration; integer multiple of an association period; and a second fixed time duration.

[0150] In an embodiment, the association period corresponds to active SSB indices in a second SSB burst.

[0151] In an embodiment, the fixed time duration comprises enough valid ROs for mapping the at least one first SSB index; and RACH repetition configured in the at least one RACH configuration.

[0152] In an embodiment, the at least one RACH configuration comprises: scheduling information of the plurality of ROs; minimum reference signal received power (RSRP) value for an SSB beam in the SSB burst; total number of preambles for RACH; number of SSBs sharing an RO; number of preambles per SSB; number of ROs multiplexed in the frequency domain; an at least one index from a predefined table; length of RACH preamble; at least one root sequence to generate the RACH preamble; and at least one cyclic shift to generate the RACH preamble.

[0153] In an embodiment, the at least one RACH configuration is dedicated for a WUS received by the at least one second node.

[0154] In an embodiment, the at least one RACH configuration configures a dedicated set of RACH preambles.

[0155] In an embodiment, the at least one parameter is at least one of: direction of arrival of the WUS; location of the at least one first node; and position of the at least one first node.

[0156] In an embodiment, the method further comprises transmitting at least one of: the WUS configuration; one of predefined pattern and a predefined sequence; active SSB indices of the SSB burst; periodicity of at least one SSB of the SSB burst; maximum RACH retransmission attempts; power incremental factor for RACH retransmission; priority of each SSB index from the at least one SSB index; order of mapping each SSB index from the at least one first SSB index; an SSB index from the at least one first SSB index to start mapping; index of at least one second SSB for which the mapping is pending; number of at least one second SSB for which the mapping is pending; start of at least one valid RO; and RACH response message.

[0157] In an embodiment, SSB-RO mapping for the at least one first SSB index starts from the at least one valid RO.

[0158] In an embodiment, transmitting is in at least one of: the at least one SIB; a connected cell; a primary cell; and an anchor cell.

[0159] In an embodiment, the mapping comprises at least one of: dividing one of the number of preambles and number of the plurality of valid ROs among the at least one first SSBindex; and dividing the number of preambles in each RO from the plurality of valid ROs among the at least one first SSB index.

[0160] In an embodiment, the division is one of: equal; and based on at least one parameter configured by the at least one RACH configuration.

[0161] In an embodiment, the mapping is in the order of at least one of: priority of each SSB index in the at least one first SSB index; and increasing order of index of each SSB index in the at least one first SSB index.

[0162] In an embodiment, transmitting one of predefined pattern and a predefined sequence indicate one of: start of the WUS occasion; and reference time for determining the WUS occasion.

[0163] In an embodiment, receiving the WUS comprises: monitoring, by the at least one first node, for one of a predefined pattern and a predefined sequence; and receiving one of a predefined pattern and a predefined sequence.

[0164] In an embodiment, the predefined sequence is one of: primary synchronization sequence (PSS); and secondary synchronization sequence (SSS).

[0165] In an embodiment, configuring comprises: indicating availability of the plurality of ROs from the reference point for a fixed duration.

[0166] In an embodiment, indicating is using dynamic control information (DCI).

[0167] The figures of the disclosure are provided to illustrate some examples of the invention described. The figures are not to limit the scope of the depicted embodiments of the appended claims. Aspects of the disclosure are described herein with reference to the invention to example embodiments for illustration. It should be understood that specific details, relationships, and method are set forth to provide a full understanding of the example embodiments. One of ordinary skill in the art recognize the example embodiments can be practiced without one or more specific details and / or with other methods.

[0168] Similarly, while operations are depicted in the drawings 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 desirableresults. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products.

[0169] While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any disclosures or of what may be claimed, but rather as descriptions of features specific to particular embodiments of particular disclosures. Certain features that are described herein in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable sub combination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a sub combination or variation of a sub combination.

[0170] Thus, particular embodiments of the subject matter have been described. Other embodiments are within the scope of the following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve desirable results. In addition, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In certain implementations, multitasking and parallel processing may be advantageous.

[0171] It is to be understood that the disclosure is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation, unless described otherwise.

Claims

WE CLAIM:

1. A method for random access procedure (RACH) in a wireless communication system, the method comprising: receiving, by at least one first node, at least one of at least one synchronization signal block (SSB) index, and at least one RACH configuration, wherein the at least one SSB index represents at least one SSB of an SSB burst, wherein the at least one RACH configuration indicates plurality of RACH occasions (ROs), and wherein the plurality of ROs is available for a fixed time duration from a reference point; mapping, by the at least one first node, the at least one SSB index to at least one valid RO from the plurality of ROs; and transmitting, by the at least one first node, a RACH preamble in a valid RO from the at least one valid RO.

2. The method as claimed in claim 1, wherein receiving by the at least one first node is performed after transmitting a wake up signal (WUS).

3. The method as claimed in claim 2, wherein the configuration for transmitting the WUS is predefined in standards or preconfigured at the time of deployment.

4. The method as claimed in claim 1, wherein the at least one SSB index is determined based on at least one of: measurements on the WUS transmitted by the at least one first node; and content of the WUS.

5. The method as claimed in claim 1, wherein receiving further comprises receiving at least one of: a. at least one system information block (SIB);b. at least one SSB of the SSB burst; c. configuration for transmitting the WUS; d. active SSB indices of the SSB burst; e. periodicity of at least one SSB of the SSB burst; f. priority of each SSB index in the at least one SSB index; g. indication of availability of the plurality of ROs from the reference point for the fixed time duration; h. order of mapping each SSB index in the at least one SSB index; i. an SSB index from the at least one SSB index to start mapping; j. index of at least one second SSB for which the mapping is pending; k. number of at least one second SSB for which the mapping is pending; and l. start of the at least one valid RO.

6. The method as claimed in claim 5, wherein the start of the at least one valid RO comprises at least one of: the number of ROs from the plurality of ROs; and the number of time resources to skip before starting mapping for the at least one SSB index.

7. The method as claimed in claim 1, wherein the at least one RACH configuration further comprises: a. scheduling information of the plurality of ROs; b. minimum reference signal received power (RSRP) value for an SSB; c. total number of preambles for RACH; d. number of SSBs sharing an RO;e. number of preambles per SSB; f. number of ROs multiplexed in the frequency domain; g. at least one index from a predefined table; h. length of RACH preamble; i. at least one root sequence to generate the RACH preamble; and j. at least one cyclic shift to generate the RACH preamble.

8. The method as claimed in claim 5, wherein the active SSB indices within the SSB burst is dedicated for the WUS.

9. The method as claimed in claim 1, wherein the reference point is one of: a. start of the SSB burst; b. end of the SSB burst; c. start of at least one SIB; d. end of at least one SIB; e. start of first frame of a SIB modification period; and f. time instant of transmitting a WUS.

10. The method as claimed in claim 1, further comprises: monitoring of RACH response in a window.

11. The method as claimed in claim 10, further comprises transmitting the RACH preamble in a second valid RO from the at least one valid RO, when the RACH response is not received within the window; and value of retransmission counter is less than maximum retransmission attempts.

12. The method as claimed in claim 11, wherein transmitting the RACH preamble in a second valid RO further comprises incrementing the retransmission counter.

13. The method as claimed in claim 11, wherein the window and the maximum retransmission attempts are received by the at least one first node.

14. The method as claimed in claim 10, further comprises transmitting a WUS, when the at least one valid RO is not available.

15. The method as claimed in claim 1, wherein the valid RO corresponds to the best SSB.

16. The method as claimed in claim 5, wherein receiving the at least one SSB further comprises: computing the RSRP values corresponding to the at least one SSB; comparing the RSRP values with a minimum RSRP value configured; and selecting the best SSB with the RSRP value crossing the minimum RSRP value.

17. The method as claimed in claim 1, wherein mapping comprises at least one of: dividing one of the number of preambles and number of the at least one valid RO within the fixed time duration of the at least one first SSB index; and dividing the number of preambles in each RO from the at least one valid RO of the at least one first SSB index.

18. The method as claimed in claim 17, wherein the division is one of: equal; and based on at least one parameter configured by the at least one RACH configuration.

19. The method as claimed in claim 5, wherein receiving the index of the at least one second SSB for which the mapping is pending further comprises: determining at least one third SSB index, from the at least one SSB index, that matches with the index of at least one second SSB; and start mapping from the at least one third SSB index.

20. The method as claimed in claim 5, wherein receiving the number of at least one second SSB for which the mapping is pending further comprises: skipping or delaying the mapping for a number of ROs mapping to the at least one second SSB.

21. The method as claimed in claim 1, wherein mapping is in the order of at least one of: priority of each SSB index in the at least one SSB index; andincreasing order of index of each SSB index in the at least one SSB index.

22. The method as claimed in claim 1, wherein receiving comprises at least one of: monitoring, by the at least one first node, for a predefined pattern and sequence; and transmitting one of a predefined pattern and a predefined sequence.

23. The method as claimed in claim 22, wherein the sequence is one of: primary synchronization sequence (PSS); and secondary synchronization sequence (SSS).

24. The method as claimed in claim 1, wherein receiving is performed in at least one of: at least one SIB; a connected cell; a primary cell; and an anchor cell.

25. The method as claimed in claim 1, wherein the at least one RACH configuration is dedicated for a WUS transmitted by the at least one first node.

26. The method as claimed in claim 1, wherein the fixed time duration is at least one of: predefined; and received by the at least one first node through signalling.

27. The method as claimed in claim 1, wherein the fixed time duration is one of: a. a portion of the RACH association period, wherein the portion is one of the first half of the RACH association period, first quarter of the RACH association period, first eighth of the RACH association period, or first sixteenth of the RACH association period; b. an integer multiple of the RACH association period;c. an integer multiple of RACH configuration period; and d. the time gap between two consecutive SSB bursts.

28. The method as claimed in claim 1, wherein the fixed time duration is within integer multiple of one of: RACH association period; and RACH association pattern period.

29. The method as claimed in claim 1, wherein the at least one valid RO is at least one of: non-overlapping with DL time resource; and non-overlapping with time resource configured for SSB.

30. A method for random access procedure (RACH) in a wireless communication system, the method comprising: transmitting, by at least one second node, at least one of a synchronization signal block (SSB) burst and at least one system information block (SIB); configuring, by the at least one second node, at least one first SSB index and at least one RACH configuration, wherein the at least one first SSB index represents at least one SSB of the SSB burst, wherein the at least one RACH configuration configures a plurality of RACH occasions (ROs), and wherein the plurality of ROs is available for a fixed time duration from a reference point; and receiving, by the at least one second node, at least one RACH preamble in at least one valid RO from a plurality of valid ROs.

31. The method as claimed in claim 30, wherein transmitting is performed after receiving at least one wake up signal (WUS).

32. The method as claimed in claim 31, wherein the configuration for the WUS is predefined in standards or preconfigured at the time of deployment.

33. The method as claimed in claim 30, wherein the at least one first SSB index is determined based on at least one of: at least one parameter measured on the WUS received; and content of the WUS received.

34. The method as claimed in claim 30, further comprises: identifying, by the at least one second node, at least one second SSB index from the at least one first SSB index based on the at least one RACH preamble and the at least one valid RO.

35. The method as claimed in claim 34, wherein identifying the at least one second SSB index comprises: mapping the at least one first SSB index to the plurality of valid ROs; and identifying the SSB indices corresponding to the at least one valid RO.

36. The method as claimed in claim 30, wherein the reference point is one of: a. start of the SSB burst; b. end of the SSB burst; c. start of the at least one SIB; d. end of the at least one SIB; e. start of first frame of a SIB modification period; and f. time instant of transmitting a WUS.

37. The method as claimed in claim 30, wherein the fixed time duration is at least one of: a. predefined; b. configured by the at least one second node;c. portion of the RACH association period; d. an integer multiple of the RACH association period; e. an integer multiple of RACH configuration period; and f. the time gap between two consecutive SSB bursts.

38. The method as claimed in claim 37, wherein the portion is one of the first half of the RACH association period, first quarter of the RACH association period, first eighth of the RACH association period, or first sixteenth of the RACH association period.

39. The method as claimed in claim 30, wherein the fixed time duration is within integer multiple of one of: RACH association period; and RACH association pattern period.

40. The method as claimed in claim 30, wherein the plurality of valid ROs is at least one of: non-overlapping with DL time resource; and non-overlapping with time resource configured for SSB.

41. The method as claimed in claim 34, wherein the at least one second SSB index corresponds to the best SSB beam for the at least one first node.

42. The method as claimed in claim 30, further comprises: receiving the WUS within the fixed time duration; and extending the fixed time duration.

43. The method as claimed in claim 42, comprises transmitting at least one of a second SSB burst and at least one second SIB.

44. The method as claimed in claim 42, wherein extending the fixed time duration is by one of: a. fraction of the fixed time duration;b. an integer multiple of the fixed time duration; c. integer multiple of an association period; and d. a second fixed time duration.

45. The method as claimed in claim 44, wherein the association period corresponds to active SSB indices in a second SSB burst.

46. The method as claimed in claim 30, wherein the fixed time duration comprises enough valid ROs for mapping the at least one first SSB index; and RACH repetition configured in the at least one RACH configuration.

47. The method as claimed in claim 30, wherein the at least one RACH configuration comprises: a. scheduling information of the plurality of ROs; b. minimum reference signal received power (RSRP) value for an SSB beam in the SSB burst; c. total number of preambles for RACH; d. number of SSBs sharing an RO; e. number of preambles per SSB; f. number of ROs multiplexed in the frequency domain; g. an at least one index from a predefined table; h. length of RACH preamble; i. at least one root sequence to generate the RACH preamble; and j. at least one cyclic shift to generate the RACH preamble.

48. The method as claimed in claim 30, wherein the at least one RACH configuration is dedicated for a WUS received by the at least one second node.

49. The method as claimed in claim 48, wherein the at least one RACH configuration configures a dedicated set of RACH preambles.

50. The method as claimed in claim 33, wherein the at least one parameter is at least one of:direction of arrival of the WUS; location of the at least one first node; and position of the at least one first node.

51. The method as claimed in claim 30, further comprises transmitting at least one of: a. the WUS configuration; b. one of predefined pattern and a predefined sequence; c. active SSB indices of the SSB burst; d. periodicity of at least one SSB of the SSB burst; e. maximum RACH retransmission attempts; f. power incremental factor for RACH retransmission; g. priority of each SSB index from the at least one SSB index; h. order of mapping each SSB index from the at least one first SSB index; i. an SSB index from the at least one first SSB index to start mapping; j. index of at least one second SSB for which the mapping is pending; k. number of at least one second SSB for which the mapping is pending; l. start of at least one valid RO; and m. RACH response message.

52. The method as claimed in claim 51, wherein SSB-RO mapping for the at least one first SSB index starts from the at least one valid RO.

53. The method as claimed in claim 51, wherein transmitting is in at least one of: the at least one SIB; a connected cell; a primary cell; andan anchor cell.

54. The method as claimed in claim 35, wherein mapping comprises at least one of: dividing one of the number of preambles and number of the plurality of valid ROs among the at least one first SSB index; and dividing the number of preambles in each RO from the plurality of valid ROs among the at least one first SSB index.

55. The method as claimed in claim 54, wherein the division is one of: equal; and based on at least one parameter configured by the at least one RACH configuration.

56. The method as claimed in claim 35, wherein mapping is in the order of at least one of: priority of each SSB index in the at least one first SSB index; and increasing order of index of each SSB index in the at least one first SSB index.

57. The method as claimed in claim 51, wherein transmitting one of predefined pattern and a predefined sequence indicate one of: start of the WUS occasion; and reference time for determining the WUS occasion.

58. The method as claimed in claim 31, wherein receiving the WUS comprises: monitoring, by the at least one first node, for one of a predefined pattern and a predefined sequence; and receiving one of a predefined pattern and a predefined sequence.

60. The method as claimed in at least one of claim 51 or 58, wherein the predefined sequence is one of: primary synchronization sequence (PSS); and secondary synchronization sequence (SSS).

61. The method as claimed in claim 30, wherein configuring comprises:indicating availability of the plurality of ROs from the reference point for a fixed duration.

62. The method as claimed in claim 60, wherein indicating is using dynamic control information (DCI).

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