Random access

Abstract

Embodiments of the present disclosure disclose devices, methods and apparatuses for the random access. In the embodiments, a terminal device receives, from a network device, configuration information comprising multiple formats or multiple cyclic prefix (CP) durations for a physical random access channel (PRACH). The multiple formats are different with each other at least in a CP duration. The terminal device selects, based on a predefined or configured criterion, a format from the multiple formats or a CP duration from the multiple CP durations. Then, the terminal device performs, to the network device, a PRACH transmission based on the selected format or the selected CP duration.

Description

RANDOM ACCESSCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority from, and the benefit of, US Provisional Application No. 63 / 741239, filed January 2, 2025, which is hereby incorporated by reference in its entirety.FIELD

[0002] Various example embodiments relate to the field of communications and in particular, to devices, methods, apparatuses and a computer readable storage medium for random access, for example, in a low power wide area (LPWA) network.BACKGROUND

[0003] A communication network can be seen as a facility that enables communications between two or more communication devices, or provides communication devices access to a data network. A mobile or wireless communication network is one example of a communication network.

[0004] Such communication networks operate in accordance with standards, such as those promulgated by 3GPP (Third Generation Partnership Project) or ETSI (European Telecommunications Standards Institute). Examples of such standards include the so-called 5G (5th Generation) standard or other standards promulgated by 3GPP.SUMMARY

[0005] In general, example embodiments of the present disclosure provide a solution for random access, for instance, in the low power wide area (LPWA) network.

[0006] In a first aspect, there is provided a terminal device. The terminal device comprises at least one processor and at least one memory including computer program codes. The at least one memory and the computer program codes are configured to, with the at least one processor, cause the terminal device to: receive, from a network device, configuration information comprising multiple formats or multiple cyclic prefix (CP) durations for a physical random access channel (PRACH). The multiple formats are different with each other at least in a CP duration. The terminal device is further caused to select, based on a predefined or a configured criterion, a format from the multiple formats or a CP duration from the multiple CP durations. The terminal device is further caused to perform, to the network device, a PRACH transmission based on the selected format or the selected CP duration.

[0007] In a second aspect, there is provided a network device. The network device comprises at least one processor and at least one memory including computer program codes. The at least one memory and the computer program codes are configured to, with the at least one processor, cause the network device to: transmit, to a terminal device, configuration information comprising multiple formats or multiple cyclic prefixes (CP) durations for a physical random access channel (PRACH). The multiple formats are different witheach other at least in a CP duration. The network device is further caused to transmit, to the terminal device, a predefined or a configured criterion. The network device is further caused to perform, from the terminal device, a reception of a PRACH transmission that is based on a format of the multiple formats or a CP duration of the multiple CP durations.

[0008] In a third aspect, there is provided a terminal device. The terminal device comprises at least one processor and at least one memory including computer program codes. The at least one memory and the computer program codes are configured to, with the at least one processor, cause the terminal device to: receive, from a network device, configuration information comprising multiple formats or multiple cyclic prefixes (CP) durations for a physical random access channel (PRACH). The multiple formats are different with each other at least in a CP duration. The terminal device is further caused to transmit, to the network device, a request for validating whether the terminal device is allowed to use a first format of the multiple formats or a first cyclic prefix (CP) duration of the multiple CP durations. The terminal device is further caused to receive an indication of a validation result from the network device. The terminal device is further caused to select, based on the validation result, a format from the multiple formats or a CP duration from the multiple CP durations; and perform, to the network device, a PRACH transmission using the selected format or selected CP duration.

[0009] In a fourth aspect, there is provided a network device. The network device comprises at least one processor and at least one memory including computer program codes. The at least one memory and the computer program codes are configured to, with the at least one processor, cause the network device to: transmit, to a terminal device, configuration information comprising multiple formats or multiple cyclic prefixes (CP) durations for a physical random access channel (PRACH). The multiple formats are different with each other at least in a CP duration. The network device is further caused to receive, from the terminal device, a request for validating whether a first format of the multiple formats or a first cyclic prefix (CP) duration of the multiple CP durations can be used. The network device is further caused to transmit an indication of a validation result to the terminal device. The network device is further caused to receive, from the terminal device, a PRACH transmission using a format or CP duration that is selected from the multiple formats or multiple CP durations based on the validation result.

[0010] In a fifth aspect, there is provided a terminal device. The terminal device comprises at least one processor and at least one memory including computer program codes. The at least one memory and the computer program codes are configured to, with the at least one processor, cause the terminal device to: receive, from a network device, configuration information comprising a set of preambles associated with a timing adjustment. The terminal device is further caused to determine whether a criterion related to usage of the set of preambles and a set of timing offsets is satisfied. The terminal device is further caused to, based on determining that the criterion is satisfied, determine a preamble among the set of preambles. The terminal device is further caused to select a first timing offset from the set of timing offsets. The terminaldevice is further caused to perform, to the network device, a physical random access channel (PRACH) transmission comprising the preamble by applying a timing advance (TA) of the terminal device and the first timing offset.

[0011] In a sixth aspect, there is provided a network device. The network device comprises at least one processor and at least one memory including computer program codes. The at least one memory and the computer program codes are configured to, with the at least one processor, cause the network device to: transmit, to a terminal device, configuration information comprising a set of preambles associated with a timing adjustment. The network device is further caused to transmit, to the terminal device, a criterion related to usage of the set of preambles and a set of timing offsets. The network device is further caused to receive, from the terminal device, a physical random access channel (PRACH) transmission comprising a preamble among the set of preambles. The PRACH transmission is adjusted based on a timing advance (TA) of the terminal device and a first timing offset selected from the set of timing offset.

[0012] In a seventh aspect, there is provided a terminal device. The terminal device comprises at least one processor and at least one memory including computer program codes. The at least one memory and the computer program codes are configured to, with the at least one processor, cause the terminal device to: receive, from a network device, configuration information comprising a set of preambles associated with a timing adjustment. The terminal device is further caused to transmit, to the network device, a request for validating whether the terminal device is allowed to use the set of preambles. The terminal device is further caused to receive an indication of a validation result from the network device.

[0013] In an eighth aspect, there is provided a network device. The network device comprises at least one processor and at least one memory including computer program codes. The at least one memory and the computer program codes are configured to, with the at least one processor, cause the network device to: transmit, to a terminal device, configuration information comprising a set of preambles associated with a timing adjustment. The network device is further caused to receive, from the terminal device, a request for validating whether the terminal device is allowed to use the set of preambles. The network device is further caused to transmit an indication of a validation result to the terminal device.

[0014] In a ninth aspect, there is provided a method implemented at a terminal device. The method comprises: receiving, from a network device, configuration information comprising multiple formats or multiple cyclic prefix (CP) durations for a physical random access channel (PRACH). The multiple formats are different with each other at least in a CP duration. The method further comprises: selecting based on a predefined or a configured criterion, a format from the multiple formats or a CP duration from the multiple CP durations; and performing, to the network device, a PRACH transmission based on the selected format or the selected CP duration.

[0015] In a tenth aspect, there is provided a method implemented at a network device. The method comprises: transmitting, to a terminal device, configuration information comprising multiple formats or multiplecyclic prefixes (CP) durations for a physical random access channel (PRACH). The multiple formats are different with each other at least in a CP duration. The method further comprises: transmitting, to the terminal device, a predefined or a configured criterion; and performing, from the terminal device, a reception of a PRACH transmission that is based on a format of the multiple formats or a CP duration of the multiple CP durations.

[0016] In an eleventh aspect, there is provided a method implemented at a terminal device. The method comprises: receiving, from a network device, configuration information comprising multiple formats or multiple cyclic prefixes (CP) durations for a physical random access channel (PRACH). The multiple formats are different with each other at least in a CP duration. The method further comprises: transmitting, to the network device, a request for validating whether the terminal device is allowed to use a first format of the multiple formats or a first cyclic prefix (CP) duration of the multiple CP durations; and receiving an indication of a validation result from the network device. The method further comprises selecting, based on the validation result, a format from the multiple formats or a CP duration from the multiple CP durations; and performing, to the network device, a PRACH transmission using the selected format or selected CP duration.

[0017] In a twelfth aspect, there is provided a method implemented at a network device. The method comprises: transmitting, to a terminal device, configuration information comprising multiple formats or multiple cyclic prefixes (CP) durations for a physical random access channel (PRACH). The multiple formats are different with each other at least in a CP duration. The method further comprises: receiving, from the terminal device, a request for validating whether a first format of the multiple formats or a first cyclic prefix (CP) duration of the multiple CP durations can be used; and transmitting an indication of a validation result to the terminal device. The method further comprises: receiving, from the terminal device, a PRACH transmission using a format or CP duration that is selected from the multiple formats or multiple CP durations based on the validation result.

[0018] In a thirteenth aspect, there is provided a method implemented at a terminal device. The method comprises: receiving, from a network device, configuration information comprising a set of preambles associated with a timing adjustment; determining whether a criterion related to usage of the set of preambles and a set of timing offsets is satisfied; based on determining that the criterion is satisfied, selecting a preamble from the set of preambles; selecting a first timing offset from the set of timing offsets; and performing, to the network device, a physical random access channel (PRACH) transmission comprising the preamble by applying a timing advance (TA) of the terminal device and the first timing offset.

[0019] In a fourteenth aspect, there is provided a method implemented at a network device. The method comprises: transmitting, to a terminal device, configuration information comprising a set of preambles associated with a timing adjustment; transmitting, to the terminal device, a criterion related to usage of the set of preambles and a set of timing offsets; receiving, from the terminal device, a physical random access channel (PRACH) transmission comprising a preamble among the set of preambles. The PRACHtransmission is adjusted based on a timing advance (TA) of the terminal device and a first timing offset selected from the set of timing offset.

[0020] In a fifteenth aspect, there is provided a method implemented at a terminal device. The method comprises: receiving, from a network device, configuration information comprising a set of preambles associated with a timing adjustment; transmitting, to the network device, a request for validating whether the terminal device is allowed to use the set of preambles; and receiving an indication of a validation result from the network device.

[0021] In a sixteenth aspect, there is provided a method implemented at a network device. The method comprises: transmitting, to a terminal device, configuration information comprising a set of preambles associated with a timing adjustment; receiving, from the terminal device, a request for validating whether the terminal device is allowed to use the set of preambles; and transmitting an indication of a validation result to the terminal device.

[0022] In a seventeenth aspect, there is provided an apparatus comprising: means for receiving, from a network device, configuration information comprising multiple formats or multiple cyclic prefix (CP) durations for a physical random access channel (PRACH), wherein multiple formats are different with each other at least in a CP duration; means for selecting based on a predefined or a configured criterion, a format from the multiple formats or a CP duration from the multiple CP durations; and means for performing, to the network device, a PRACH transmission based on the selected format or the selected CP duration.

[0023] In an eighteenth aspect, there is provided an apparatus comprising: means for transmitting, to a terminal device, configuration information comprising multiple formats or multiple cyclic prefixes (CP) durations for a physical random access channel (PRACH), wherein multiple formats are different with each other at least in a CP duration; means for transmitting, to the terminal device, a predefined or a configured criterion; and means for performing, from the terminal device, a reception of a PRACH transmission that is based on a format of the multiple formats or a CP duration of the multiple CP durations.

[0024] In a nineteenth aspect, there is provided an apparatus comprising: means for receiving, from a network device, configuration information comprising multiple formats or multiple cyclic prefixes (CP) durations for a physical random access channel (PRACH), wherein multiple formats are different with each other at least in a CP duration; means for transmitting, to the network device, a request for validating whether the terminal device is allowed to use a first format of the multiple formats or a first cyclic prefix (CP) duration of the multiple CP durations; means for receiving an indication of a validation result from the network device; means for selecting, based on the validation result, a format from the multiple formats or a CP duration from the multiple CP durations; and means for performing, to the network device, a PRACH transmission using the selected format or selected CP duration.

[0025] In a twentieth aspect, there is provided an apparatus comprising: means for transmitting, to a terminal device, configuration information comprising multiple formats or multiple cyclic prefixes (CP)durations for a physical random access channel (PRACH), wherein the multiple formats are different with each other at least in a CP duration; means for receiving, from the terminal device, a request for validating whether a first format of the multiple formats or a first cyclic prefix (CP) duration of the multiple CP durations can be used; and means for transmitting an indication of a validation result to the terminal device; and means for receiving, from the terminal device, a PRACH transmission using a format or CP duration that is selected from the multiple formats or multiple CP durations based on the validation result.

[0026] In a twenty first aspect, there is provided an apparatus comprising: means for receiving, from a network device, configuration information comprising a set of preambles associated with a timing adjustment; means for determining whether a criterion related to usage of the set of preambles and a set of timing offsets is satisfied; means for based on determining that the criterion is satisfied, selecting a preamble from the set of preambles; means for selecting a first timing offset from the set of timing offsets; and means for performing, to the network device, a physical random access channel (PRACH) transmission comprising the preamble by applying a timing advance (TA) of the terminal device and the first timing offset.

[0027] In a twenty second aspect, there is provided an apparatus comprising: means for transmitting, to a terminal device, configuration information comprising a set of preambles associated with a timing adjustment; means for transmitting, to the terminal device, a criterion related to usage of the set of preambles and a set of timing offsets; means for receiving, from the terminal device, a physical random access channel (PRACH) transmission comprising a preamble among the set of preambles, wherein PRACH transmission is adjusted based on a timing advance (TA) of the terminal device and a first timing offset selected from the set of timing offset.

[0028] In a twenty third aspect, there is provided an apparatus comprising: means for receiving, from a network device, configuration information comprising a set of preambles associated with a timing adjustment; means for transmitting, to the network device, a request for validating whether the terminal device is allowed to use the set of preambles; and means for receiving an indication of a validation result from the network device.

[0029] In a twenty fourth aspect, there is provided an apparatus comprising: means for transmitting, to a terminal device, configuration information comprising a set of preambles associated with a timing adjustment; means for receiving, from the terminal device, a request for validating whether the terminal device is allowed to use the set of preambles; and means for transmitting an indication of a validation result to the terminal device.

[0030] In a twenty fifth aspect, there is provided a non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the method according to any one of the above ninth to sixteenth aspects.

[0031] In a twenty sixth aspect, there is provided a computer program comprising instructions, which, when executed by an apparatus, cause the apparatus at least to: receive, from a network device,configuration information comprising multiple formats or multiple cyclic prefix (CP) durations for a physical random access channel (PRACH). The multiple formats are different with each other at least in a CP duration. The apparatus is further caused to select, based on a predefined or a configured criterion, a format from the multiple formats or a CP duration from the multiple CP durations. The apparatus is further caused to perform, to the network device, a PRACH transmission based on the selected format or the selected CP duration.

[0032] In a twenty seventh aspect, there is provided a computer program comprising instructions, which, when executed by an apparatus, cause the apparatus at least to: transmit, to a terminal device, configuration information comprising multiple formats or multiple cyclic prefixes (CP) durations for a physical random access channel (PRACH). The multiple formats are different with each other at least in a CP duration. The apparatus is further caused to transmit, to the terminal device, a predefined or a configured criterion. The apparatus is further caused to perform, from the terminal device, a reception of a PRACH transmission that is based on a format of the multiple formats or a CP duration of the multiple CP durations.

[0033] In a twenty eighth aspect, there is provided a computer program comprising instructions, which, when executed by an apparatus, cause the apparatus at least to: receive, from a network device, configuration information comprising multiple formats or multiple cyclic prefixes (CP) durations for a physical random access channel (PRACH). The multiple formats are different with each other at least in a CP duration. The apparatus is further caused to transmit, to the network device, a request for validating whether the terminal device is allowed to use a first format of the multiple formats or a first cyclic prefix (CP) duration of the multiple CP durations. The apparatus is further caused to receive an indication of a validation result from the network device. The apparatus is further caused to select, based on the validation result, a format from the multiple formats or a CP duration from the multiple CP durations; and perform, to the network device, a PRACH transmission using the selected format or selected CP duration.

[0034] In a twenty ninth aspect, there is provided a computer program comprising instructions, which, when executed by an apparatus, cause the apparatus at least to: transmit, to a terminal device, configuration information comprising multiple formats or multiple cyclic prefixes (CP) durations for a physical random access channel (PRACH). The multiple formats are different with each other at least in a CP duration. The apparatus is further caused to receive, from the terminal device, a request for validating whether a first format of the multiple formats or a first cyclic prefix (CP) duration of the multiple CP durations can be used. The apparatus is further caused to transmit an indication of a validation result to the terminal device. The apparatus is further caused to receive, from the terminal device, a PRACH transmission using a format or CP duration that is selected from the multiple formats or multiple CP durations based on the validation result.

[0035] In a thirtieth aspect, there is provided a computer program comprising instructions, which, when executed by an apparatus, cause the apparatus at least to: receive, from a network device, configuration information comprising a set of preambles associated with a timing adjustment. The apparatus is furthercaused to determine whether a criterion related to usage of the set of preambles and a set of timing offsets is satisfied. The apparatus is further caused to, based on determining that the criterion is satisfied, select a preamble from the set of preambles; and select a first timing offset from the set of timing offsets. The apparatus is further caused to perform, to the network device, a physical random access channel (PRACH) transmission comprising the preamble by applying a timing advance (TA) of the terminal device and the first timing offset.

[0036] In a thirty first aspect, there is provided a computer program comprising instructions, which, when executed by an apparatus, cause the apparatus at least to: transmit, to a terminal device, configuration information comprising a set of preambles associated with a timing adjustment. The apparatus is further caused to transmit, to the terminal device, a criterion related to usage of the set of preambles and a set of timing offsets. The apparatus is further caused to receive, from the terminal device, a physical random access channel (PRACH) transmission comprising a preamble among the set of preambles. The PRACH transmission is adjusted based on a timing advance (TA) of the terminal device and a first timing offset selected from the set of timing offset.

[0037] In a thirty second aspect, there is provided a computer program comprising instructions, which, when executed by an apparatus, cause the apparatus at least to: receive, from a network device, configuration information comprising a set of preambles associated with a timing adjustment. The apparatus is further caused to transmit, to the network device, a request for validating whether the terminal device is allowed to use the set of preambles. The apparatus is further caused to receive an indication of a validation result from the network device.

[0038] In a thirty third aspect, there is provided a computer program comprising instructions, which, when executed by an apparatus, cause the apparatus at least to: transmit, to a terminal device, configuration information comprising a set of preambles associated with a timing adjustment. The apparatus is further caused to receive, from the terminal device, a request for validating whether the terminal device is allowed to use the set of preambles. The apparatus is further caused to transmit an indication of a validation result to the terminal device.

[0039] In a thirty fourth aspect, there is provided a terminal device. The terminal device comprises: receiving circuitry configured to receive, from a network device, configuration information comprising multiple formats or multiple cyclic prefix (CP) durations for a physical random access channel (PRACH), wherein multiple formats are different with each other at least in a CP duration; a selecting circuitry configured to select, based on a predefined or a configured criterion, a format from the multiple formats or a CP duration from the multiple CP durations; and a performing circuitry configured to perform, to the network device, a PRACH transmission based on the selected format or the selected CP duration.

[0040] In a thirty fifth aspect, there is provided a network device. The network device comprises: first transmitting circuitry configured to transmit, to a terminal device, configuration information comprising multipleformats or multiple cyclic prefixes (CP) durations for a physical random access channel (PRACH), wherein multiple formats are different with each other at least in a CP duration; second transmitting circuitry configured to transmit, to the terminal device, a predefined or a configured criterion; and performing circuitry configured to perform, from the terminal device, a reception of a PRACH transmission that is based on a format of the multiple formats or a CP duration of the multiple CP durations.

[0041] In a thirty sixth aspect, there is provided a terminal device. The terminal device comprises: first receiving circuitry configured to receive, from a network device, configuration information comprising multiple formats or multiple cyclic prefixes (CP) durations for a physical random access channel (PRACH), wherein multiple formats are different with each other at least in a CP duration; transmitting circuitry configured to transmit, to the network device, a request for validating whether the terminal device is allowed to use a first format of the multiple formats or a first cyclic prefix (CP) duration of the multiple CP durations; second receiving circuitry configured to receiving an indication of a validation result from the network device; selecting circuitry configured to select, based on the validation result, a format from the multiple formats or a CP duration from the multiple CP durations; and performing circuitry configured to perform, to the network device, a PRACH transmission using the selected format or selected CP duration.

[0042] In a thirty seventh aspect, there is provided a network device. The network device comprises: first transmitting circuitry configured to transmit, to a terminal device, configuration information comprising multiple formats or multiple cyclic prefixes (CP) durations for a physical random access channel (PRACH), wherein the multiple formats are different with each other at least in a CP duration; first receiving circuitry configured to receive, from the terminal device, a request for validating whether a first format of the multiple formats or a first cyclic prefix (CP) duration of the multiple CP durations can be used; second transmitting circuitry configured to transmit an indication of a validation result to the terminal device; and second receiving circuitry configured to receive, from the terminal device, a PRACH transmission using a format or CP duration that is selected from the multiple formats or multiple CP durations based on the validation result.

[0043] In a thirty eighth aspect, there is provided a terminal device. The terminal device comprises: receiving circuitry configured to receive, from a network device, configuration information comprising a set of preambles associated with a timing adjustment; first determining circuitry configured to determine whether a criterion related to usage of the set of preambles and a set of timing offsets is satisfied; first selecting circuitry configured to based on determining that the criterion is satisfied, determine a preamble among the set of preambles; second selecting circuitry configured to select first timing offset from the set of timing offsets; and performing circuitry configured to perform, to the network device, a physical random access channel (PRACH) transmission comprising the preamble by applying a timing advance (TA) of the terminal device and the first timing offset.

[0044] In a thirty ninth aspect, there is provided a network device. The network device comprises: first transmitting circuitry configured to transmit, to a terminal device, configuration information comprising a setof preambles associated with a timing adjustment; second transmitting circuitry configured to transmit, to the terminal device, a criterion related to usage of the set of preambles and a set of timing offsets; receiving circuitry configured to receive, from the terminal device, a physical random access channel (PRACH) transmission comprising a preamble among the set of preambles, wherein PRACH transmission is adjusted based on a timing advance (TA) of the terminal device and a first timing offset selected from the set of timing offset.

[0045] In a fortieth aspect, there is provided a terminal device. The terminal device comprises: receiving circuitry configured to receive, from a network device, configuration information comprising a set of preambles associated with a timing adjustment; transmitting circuitry configured to transmit, to the network device, a request for validating whether the terminal device is allowed to use the set of preambles; and receiving circuitry configured to receive an indication of a validation result from the network device.

[0046] In a forty first aspect, there is provided a network device. The network device comprises: transmitting circuitry configured to transmit, to a terminal device, configuration information comprising a set of preambles associated with a timing adjustment; receiving circuitry configured to receive, from the terminal device, a request for validating whether the terminal device is allowed to use the set of preambles; and transmitting circuitry configured to transmit an indication of a validation result to the terminal device.

[0047] It is to be understood that the summary section is not intended to identify key or essential features of embodiments of the present disclosure, nor is it intended to be used to limit the scope of the present disclosure. Other features of the present disclosure will become easily comprehensible through the following description.BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Some example embodiments will now be described with reference to the accompanying drawings, in which:

[0049] FIG. 1A illustrates an example communication network in which embodiments of the present disclosure may be implemented;

[0050] FIG. 1B illustrates an example of a carrier for Enhanced Mobile Broadband (eMBB) network and low power wide area (LPWA) network frequency subband deployed in the carrier;

[0051] FIG. 1C illustrates examples of physical random access channel (PRACH) reception at the network device from terminal devices at different locations in the cell;

[0052] FIG. 1 D illustrates an example of a contention-based four-step random access procedure;

[0053] FIG. 2 illustrates a first example signaling process for random access in the LPWA network according to example embodiments of the present disclosure;

[0054] FIG. 3 illustrates example normal and lean PRACH formats supported in a cell, according to example embodiments of the present disclosure;

[0055] FIG. 4 illustrates a second example signaling process for random access in the LPWA network according to example embodiments of the present disclosure;

[0056] FIG. 5 illustrates a third example signaling process for random access in the LPWA network according to example embodiments of the present disclosure;

[0057] FIG. 6 illustrates a fourth example signaling process for random access in the LPWA network according to example embodiments of the present disclosure;

[0058] FIG. 7 illustrates a fifth example signaling process for random access in the LPWA network according to example embodiments of the present disclosure;

[0059] FIG. 8A illustrates PRACH reception at the network device for terminal devices that know TAs and use the same preamble and apply the TAs;

[0060] FIG. 8B illustrates PRACH reception at the network device for terminal devices that know TAs, use the same preamble and apply both the TAs and a timing offset according to example embodiments of the present disclosure;

[0061] FIG. 9 illustrates an example of a portion of a random access response (RAR) according to example embodiments of the present disclosure;

[0062] FIG. 10 illustrates a sixth example signaling process for random access in the LPWA network according to example embodiments of the present disclosure;

[0063] FIG. 11 illustrates a seventh example signaling process for random access in the LPWA network according to example embodiments of the present disclosure;

[0064] FIG. 12 illustrates a flowchart of a method implemented at a terminal device according to some embodiments of the present disclosure;

[0065] FIG. 13 illustrates a flowchart of a method implemented at a network device according to some embodiments of the present disclosure;

[0066] FIG. 14 illustrates a flowchart of a method implemented at a terminal device according to some embodiments of the present disclosure;

[0067] FIG. 15 illustrates a flowchart of a method implemented at a network device according to some embodiments of the present disclosure;

[0068] FIG. 16 illustrates a flowchart of a method implemented at a terminal device according to some embodiments of the present disclosure;

[0069] FIG. 17 illustrates a flowchart of a method implemented at a network device according to some embodiments of the present disclosure;

[0070] FIG. 18 illustrates a flowchart of a method implemented at a terminal device according to some embodiments of the present disclosure;

[0071] FIG. 19 illustrates a flowchart of a method implemented at a network device according to some embodiments of the present disclosure;

[0072] FIG. 20 illustrates a simplified block diagram of an apparatus that is suitable for implementing embodiments of the present disclosure; and

[0073] FIG. 21 illustrates a block diagram of an example computer readable medium in accordance with some embodiments of the present disclosure.

[0074] Throughout the drawings, the same or similar reference numerals represent the same or similar element.DETAILED DESCRIPTION

[0075] Principles of the present disclosure will now be described with reference to some example embodiments. It is to be understood that these embodiments are described only for the purpose of illustration and help those skilled in the art to understand and implement the present disclosure, without suggesting any limitation as to the scope of the disclosure. The disclosure described herein can be implemented in various manners other than the ones described below.

[0076] In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skills in the art to which this disclosure belongs.

[0077] References in the present disclosure to “one embodiment,” “an embodiment,” “an example embodiment,” and the like indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0078] It shall be understood that although the terms “first” and “second” etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and / or” includes any and all combinations of one or more of the listed terms.

[0079] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “has”, “having”, “includes” and / or “including”, when used herein, specify the presence of stated features, elements, and / or components etc., but do not preclude the presence or addition of one or more other features, elements, components and / or combinations thereof. Asused herein, “at least one of the following: ” and “at least one of ” and similar wording, where the list of two or more elements are joined by “and” or “or”, mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

[0080] As used in this application, the term “circuitry” may refer to one or more or all of the following: (a) hardware-only circuit implementations (such as implementations in only analog and / or digital circuitry) and (b) combinations of hardware circuits and software, such as (as applicable): (i) a combination of analog and / or digital hardware circuit(s) with software / firmware and (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and (c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

[0081] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[0082] As used herein, the term “communication network” refers to a network following any suitable communication standards, such as 5G New Radio (NR), Long Term Evolution (LTE), LTE-Advanced (LTE-A), Wideband Code Division Multiple Access (WCDMA), High-Speed Packet Access (HSPA), Narrow Band Internet of Things (NB-loT) and so on. Furthermore, the communications between a terminal device and a network device in the communication network may be performed according to any suitable generation communication protocols, including, but not limited to, the first generation (1G), the second generation (2G), 2.5G, 2.75G, the third generation (3G), the fourth generation (4G), 4.5G, the future fifth generation (5G) communication protocols, and / or any other protocols either currently known or to be developed in the future. Embodiments of the present disclosure may be applied in various communication systems. Given the rapid development in communications, there will of course also be future type communication technologies and systems with which the present disclosure may be embodied. It should not be seen as limiting the scope of the present disclosure to only the aforementioned systems.

[0083] As used herein, the term “network device” refers to a node in a communication network via which a terminal device accesses the network and receives services therefrom. The network device may refer to a base station (BS) or an access point (AP), for example, a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), a NR NB (also referred to as a gNB, a base station of a 5G system), a Remote Radio Unit (RRU),a radio header (RH), a remote radio head (RRH), a relay, a low power node such as a femto, a pico, and so forth, depending on the applied terminology and technology.

[0084] The term “terminal device” refers to any end device that may be capable of wireless communication. By way of example rather than limitation, a terminal device may also be referred to as a communication device, user equipment (UE), a Subscriber Station (SS), a Portable Subscriber Station, a Mobile Station (MS), or an Access Terminal (AT). The terminal device may include, but not limited to, a mobile phone, a cellular phone, a smart phone, voice over IP (VoIP) phones, wireless local loop phones, a tablet, a wearable terminal device, a personal digital assistant (PDA), portable computers, desktop computer, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, vehiclemounted wireless terminal devices, wireless endpoints, mobile stations, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), USB dongles, smart devices, wireless customer-premises equipment (CPE), an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and applications (e.g., remote surgery), an industrial device and applications (e.g., a robot and / or other wireless devices operating in an industrial and / or an automated processing chain contexts), a consumer electronics device, a device operating on commercial and / or industrial wireless networks, and the like. In the following description, the terms “terminal device”, “communication device”, “terminal”, “user equipment” and “UE” may be used interchangeably.

[0085] In recent years, loT has attracted much attention in the wireless communication technical field. More ‘things’ are expected to be interconnected for improving productivity efficiency and increasing comforts of life. Most of the existing wireless loT devices are powered by battery that need to be replaced or recharged manually. Moreover, more and more devices are capable of accessing the network. Thus, how to improve power consumption, device complexity and the number of devices supported in the loT network is focused on.

[0086] The Low Power Wide Area (LPWA) network has been introduced targeted to the above considerations. The LPWA network at least has the following characteristics: low device complexity / cost; low device power consumption enabling long battery life of greater than 10 years; enhanced coverage compared to broadband services (up to 20-25 dB enhanced coverage); support for massive number of devices; delay tolerant data transmission (up to 10 seconds to transmit a data packet); and infrequent data transmissions.

[0087] LPWA network was introduced based on Narrowband Internet of things (NB-loT) and Long Term Evolution-Machine-to Machine (LTE-M) technologies. Since the NB-loT and LTE-M frameworks are agreed to support for massive loT use cases, no new technology is further evolved currently.

[0088] With the continuous iteration of communication technology, LPWA network will be evolved accordingly. Some motivation for evolving LPWA may include: sunset of the previous generation of communication, and replacement technology will be needed when the respective carriers are no longersupported; further improve on the previous / current solution by introducing a simple lightweight radio protocol with essential features all in the same release; and a single solution to address massive loT use cases.

[0089] A common deployment scenario for LPWA network is to deploy it in-band to Enhanced Mobile Broadband (eMBB) carrier (an example of the deployment is shown in FIG. 1 B). This allows for efficient spectral usage, especially in the early LPWA deployment stage where there might not be large number of LPWA devices (loT UEs) in the system. Compared to the eMBB carrier, LPWA carrier can have significantly enhanced coverage (up to 20 - 25 dB greater coverage). To efficiently support UEs at various radio link coverage conditions, the LPWA cell is able to support multiple Coverage Enhancement (CE) levels. This then allows the UE to access the cell at the suitable coverage enhancement level.

[0090] Furthermore, LPWA is designed to cover a large cell size (e.g. NB-loT supports cell radius of up to 120 km). In turn, the LPWA network would need to support a PRACH format with large cyclic prefix (CP) and guard time (GT) to account for the long propagation delay from users at the cell edge. It is to be understood that the physical random access channel (PRACH) comprising preambles (which may be also referred to as “Msg1” in a random access procedure) transmitted by UEs at different locations in the cell will arrive at the gNB at different times (FIG. 1C schematically shows an example of the PRACHs arriving at different time).

[0091] The functionality of the CP and GT may include accounting for or reconciling the propagation delay difference among UEs, such that the processing of uplink transmission at gNB may be done in one-shot. Furthermore, the gNB can determine the time of arrival of the different UEs and then send a timing advance (TA) command in the random access response (Msg2). The UE will then adjust the timing of its uplink transmission. For example, UE at a greater distance will transmit its uplink transmission earlier than another UE near to the gNB. In this way, subsequent uplink transmissions (Msg3 and beyond) from the UEs arrive at the gNB at approximately the same time (i.e. time-synchronized in the uplink).

[0092] In LPWA, however, the UE may already know its TA or can determine its TA prior to initiating random access procedure. This can be due to, for example, UE is stationary which means it can use stored TA from past attempts. Stationary UE is common for many LPWA use cases (e.g. metering, sensors, alarms, etc.). UE that is confined to limited locations (e.g. robot vacuum in a home) may also use stored TA. In addition, UE having GNSS capability and / or being aware of gNB location (e.g. in NTN) may determine TA by itself. In addition, UE may also calculate TA using propagation delay determined from a reference time broadcast by the gNB (e.g. SIB9) and GNSS clock.

[0093] Additionally, in LPWA or possibly e.g. eMBB network, when the TA is “partially” known, e.g., based on some “partial” AI / ML estimate or can be determined by the UE to be within some smaller bound, UE may adjust its PRACH preamble transmission timing such that the preamble will arrive more, but not fully, time-aligned at the gNB. This may similarly reduce the need for such a large CP and GT for the preamble. That is, the CP would only need to account for the channel delay profile and the remaining uncertainty in thepartially known TA, but the CP would not need to account for rest of the known portion of the propagation delay.

[0094] In the case that the TA is (partially) known or can be determined by the UE, UE can adjust its PRACH preamble transmission timing such that the preamble will arrive time-aligned at the gNB. This may actually eliminate the need for large CP and GT for the preamble (i.e. CP would only need to account for or accommodate the channel delay profile but not the propagation delay).

[0095] The evolved LPWA network (which may be also referred to as “6G LPWA network”) is expected to support massive number of loT devices (e.g., 107devices per km2). In order for the I oT device(s) to access the network, it needs to perform a random access procedure. For discussion simplicity, an example of a random access procedure is shown in FIG. 1D. In general, for the massive loT devices covered in the same cell, contention or collision may occur when multiple devices attempt to access the network using the same preamble in Msg1. Although in the contention solution, contention may be resolved in Msg4, contention still wastes network resource and increases access latency.

[0096] To reduce the number of contentions (or collisions) low, a large number of preambles need to be configured. The preamble collision probability is approximately given by P=1 -exp(-y / L), where L is the total number of random access opportunities per second and y is the number of attempts per second. For example, targeting 1% collision probability, we need around 6000 random access opportunities per second to support a load of 60 attempts per second.

[0097] Furthermore, in cells supporting both LPWA and eMBB services, PRACH preambles will be partitioned for use by many features (examples from NR include SDT, coverage enhancement, Reduced Capability-RedCap, on-demand SIB, etc.), which further limit the number of preambles available for LPWA.

[0098] As a result, a very large number of random access opportunities need to be configured by the network. This results in high overhead for the PRACH and a corresponding reduction in uplink capacity for data transmission.

[0099] In view of these analyses and considerations, several aspects are proposed in some embodiments of the disclosure for, at least, increasing PRACH capacity in LPWA network without increasing PRACH overhead.

[0100] In a first aspect, a lean PRACH format may be used by UE that meets certain criteria (e.g. if UE can (mostly or) completely determine its own TA). This lean format may include a significantly shorter cyclic prefix (CP) and potentially eliminates the guard time (GT). As such, more PRACH opportunities may be obtained in a certain time period. Specifically, a terminal device receives, from a network device, configuration information comprising multiple formats or multiple cyclic prefix (CP) durations for a physical random access channel (PRACH). The multiple formats are different with each other at least in a CP duration. Based on a predefined or configured criterion, the terminal device selects a format from the multiple formats or a CP duration from the multiple CP durations. In an example, if the terminal device maydetermine its TA correctly, the terminal device may select the so-called lean PRACH format to reduce the occupied communication resources. Then, the terminal device may transmit the PRACH transmission based on the selected format or selected CP duration.

[0101] In this way, the time duration of some PRACH transmissions may be reduced significantly, and therefore more PRACH opportunities can be supported for the same overhead (i.e. time-frequency resource).

[0102] In a second aspect, whether the lean PRACH format or lean CP duration is allowed to be used can be validated at first. For example, when the terminal device accesses the cell for the first time or the terminal device moves to another location after the previous access procedure, the terminal device may validate with the network device whether the lean format is allowed to be used, since the TA of the terminal device may be changed. Specifically, a terminal device receives, from a network device, configuration information comprising multiple formats or multiple cyclic prefix (CP) durations for a physical random access channel (PRACH). The multiple formats are different with each other at least in a CP duration. The terminal device transmits, to the network device, a request for validating whether the terminal device is allowed to use a first format of the multiple formats or a first cyclic prefix (CP) duration of the multiple CP durations. Then, the terminal device receives an indication of a validation result from the network device.

[0103] In this way, the terminal device determines whether the lean format is allowed to be used based on the validation result. As such, if the lean format is allowed to be used (e.g., the determined TA is validated as correct), the terminal device may directly use the lean format. Otherwise, the terminal device may transmit the PRACH based on the normal format (i.e., having a longer CP) without wasting the resources for the failed attempts based on the lean format.

[0104] In a third aspect, the terminal devices may apply a further timing offset in addition to their respective obtained TAs. This means that the PRACH transmission will arrive synchronized in the uplink, except for the selected timing offset by the terminal device. By analyzing the timing offset, the network device can distinguish between multiple UEs transmitting using the same preamble. Specifically, a terminal device receives, from a network device, configuration information comprising a set of preambles associated with a timing adjustment. The terminal device determines whether a criterion related to usage of the set of preambles is satisfied (for example, whether the terminal device is able to obtain its TA). Based on determining that the criterion is satisfied, the terminal device determines a preamble among the set of preambles, and a first timing offset for the timing adjustment. Then, the terminal device performs, to the network device, a physical random access channel (PRACH) transmission comprising the preamble, by applying a timing advance (TA) of the terminal device and the first timing offset.

[0105] In this way, there may be a reserved preamble group associated with a timing adjustment, and the terminal devices capable of using the reserved preamble group or partition may apply a further timing offset in addition to the TA. As such, the network device may distinguish different terminal devices using the samepreamble of the reserved preamble group based on the different timing offsets. The UL capacity may be enhanced accordingly.

[0106] In a fourth aspect, as similar to the second aspect, whether the set of preambles is allowed to be used may be validated at first. As such, if the set of preambles is allowed to be used (e.g., the determined TA is validated as correct), the terminal device may directly use a preamble from the set of preambles, so that the UL capacity can be enhanced. Otherwise, the terminal device may transmit the PRACH based on a preamble selected from a normal preamble set, without wasting the resources for the failed attempts based on the lean format.

[0107] Principles and embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. Reference is first made to FIG. 1 A, which illustrates an example communication system 100 (or referred to as communication network) in which embodiments of the present disclosure may be implemented. The system 100, for example, a communication network, includes a terminal device 110 and a network device 120. In some embodiments, the network device 120 may provide the LPWA network coverage for a plurality of terminal devices comprising the terminal device 110. In some other embodiments, the network device 120 may also provide other types of network coverage, without any limitation. It is to be understood that the number of network devices and terminal devices is only for the purpose of illustration without suggesting any limitations. The system 100 may include any suitable number of network devices and terminal devices adapted for implementing embodiments of the present disclosure.

[0108] Communications in the communication system 100 may be implemented according to any proper communication protocol(s), comprising, but not limited to, cellular communication protocols of the first generation (1 G), the second generation (2G), the third generation (3G), the fourth generation (4G) and the fifth generation (5G) and on the like, wireless local network communication protocols such as Institute for Electrical and Electronics Engineers (IEEE) 802.11 and the like, and / or any other protocols currently known or to be developed in the future. Moreover, the communication may utilize any proper wireless communication technology, comprising but not limited to: Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Frequency Division Duplex (FDD), Time Division Duplex (TDD), Multiple-Input Multiple-Output (MIMO), Orthogonal Frequency Division Multiple (OFDM), Discrete Fourier Transform spread OFDM (DFT-s-OFDM) and / or any other technologies currently known or to be developed in the future.

[0109] FIG. 1B illustrates an example of a carrier for Enhanced Mobile Broadband (eMBB) network and low power wide area (LPWA) network frequency subband deployed in the carrier. As mentioned above, the carrier 130 for the LPWA may be to deploy it in-band to Enhanced Mobile Broadband (eMBB) carrier, which allows for efficient spectral usage.

[0110] FIG. 1C illustrates examples of physical random access channel (PRACH) reception at the network device from terminal devices at different locations in the cell. As shown in FIG. 1 C, since the terminaldevices may be at different locations, the propagation delays between different terminal devices and the network device may be different accordingly. Thus, the UL transmission (e.g., PRACH transmission) from different terminal devices may arrive at the network device at different timing. Regarding this, CP and GT duration are added to the payload of the UL transmission (e.g., at the head and tail of the transmission) to accommodate the different timing of the PRACH transmissions. In turn, if different terminal devices are synchronized with the network device accurately, the long CP and GT may be not needed any more.[OOlll] FIG. 1 D illustrates an example of a contention-based four-step random access procedure.

[0112] In some example embodiments of the disclosure, the term “random access procedure” refers to a sequence of signaling steps between a terminal device and a network device for the terminal device to acquire uplink synchronization and obtain specified identity (ID) for the radio access communication.

[0113] Before initiating the random access procedure, the terminal device may obtain the basic information from the system information message broadcast by the network device in the cell. For example, the terminal device may receive the synchronization signal block (SSB) to determine channel quality information, in order to determine the random access opportunity (RO) mapped to the selected SSB and spatial beam information. The terminal device receives configuration information for performing the random access procedure in the system information block 1 (SIB 1) from the network device. The configuration information may include, e.g., the preamble resource pool for the PRACH transmission. Based on the configuration information, the terminal device may perform the random access procedure.

[0114] Only for discussion purposes without any limitation, the 4-step random access includes four signaling steps. In the first step, the terminal device transmits a message 1 (Msg1) including random access preambles (which is transmitted on the physical random access channel, PRACH) to a network device to initiate the random access. In the second step, in response to receiving Msg1, the network device transmits a random access response (RAR), i.e., message 2 (Msg2), for the random access preambles to the terminal device. In the third step, once receiving the RAR, the terminal device transmits a message 3 (Msg3) using the resources allocated in the RAR to the network device. In the fourth step, after receiving the Msg3, the network device transmits a message 4 (Msg4) 160 to the terminal device. In some situations, the Msg 3 and Msg 4 may be used for the contention-based solution. Without any limitation, the random access procedure may be also contention-free.

[0001] Reference is now made to FIG. 2, which illustrates a first example signaling process for random access in a low power wide area (LPWA) network according to example embodiments of the present disclosure. For the purpose of discussions, the signaling process 200 will be described with reference to FIG. 1A. It would be appreciated that although the signaling process 200 has been described in the communication environment 100 of FIG. 1A, this signaling process 200 may be likewise applied to other communication scenarios.

[0002] In the signaling process 200, the network device 120 transmits (210) configuration information 215 including multiple formats or multiple cyclic prefixes (CP) durations for a physical random access channel (PRACH). The multiple formats are different with each other at least in a CP duration.

[0003] In some embodiments, the multiple formats may include two or more formats. For example, the multiple formats may include at least a lean format having a short CP duration and a normal format having a normal CP duration longer than the short CP duration. In addition, the preamble sequence length or duration may be the same for the multiple formats. The normal CP duration may be the same as the CP discussed with reference to FIG. 1C which is used in the LPWA network currently.

[0004] For discussion clarity, an example of the lean format and the normal format are further discussed with reference to FIG. 3. FIG. 3 illustrates example normal and lean PRACH formats supported in a cell, according to example embodiments of the present disclosure. The “SEQ” in FIG. 3 represents a preamble sequence.

[0005] As shown in FIG. 3, compared to the normal format, the lean format features a significantly shorter cyclic prefix (CP) 310 and potentially eliminates the guard time (GT). As a result, the time duration of the lean format is much shorter and therefore more PRACH opportunities can be supported for the same overhead.

[0006] Referring back to FIG. 2, in addition, in some embodiment, the multiple formats may further include a partially lean format including a medium CP duration, and the medium CP duration is longer than the short CP duration and is shorter than the normal CP duration. In addition, in some embodiments, at least one of the lean format and the partially lean format may comprise no guard period (GP) as shown in FIG. 3. For example, the lean format may omit its GP. In another example, the partially format may omit its GP. In a further example, both the lean format and partially lean format may omit their GPs.

[0007] In addition or alternatively, in some embodiments, the configuration information may comprise multiple CP durations, e.g., instead of a new PRACH format (i.e., lean or partially lean PRACH). Similarly, the multiple CP durations may include two or more CP durations. As an example, the multiple CP durations may include a lean CP duration, a partially lean CP duration longer than the lean CP duration, and a normal CP duration longer than the partially lean CP duration. The normal CP duration may be the same as the CP discussed with reference to FIG. 1C which is used in the LPWA network currently.

[0008] In some embodiments, the network device 120 may determine the configuration information based on a size of cell, one or more coverage enhancement levels supported by the cell or a load status of the cell, or both of them. For example, if the cell size is small, then the CP and GT needed for the normal format may be small. In this case, the lean format or lean CP duration may be not required, and the multiple formats may include only the normal format. In another example, if the load of the cell is low, there may be no requirement for the enhancement of UL capacity. In this case, the lean format or lean CP duration may be not required similarly.

[0009] Still referring to FIG. 2, the terminal device 110 receives (220) the configuration information 215 accordingly. Once that the terminal device is to initiate a random access procedure, the terminal device 110 selects a format from the multiple formats or a CP duration from the multiple CP durations based on a predefined or configured criterion.

[0010] In some embodiments, the terminal device 110 may determine whether the predefined or configured criterion is satisfied. If determining that the predefined or configured criterion is satisfied, the terminal device 110 may select a first format or first CP duration (for example, the lean or partially lean formation, or the lean or partially lean CP duration) as the selected format or selected CP duration. Otherwise, the terminal device 110 may select a second format or second CP duration (for example, the normal format or normal CP duration) as the selected format or selected CP duration. Moreover, in the case that the configuration information comprises the multiple formats, a CP duration of the first format (which is selected based on satisfying the criterion) is shorter than a CP duration of the second format. In the case that the configuration comprises the multiple CP durations, the first CP duration is shorter than the second CP duration. In other words, a new PRACH format (i.e., lean format or partially lean format) or new CP (lean CP duration or partially lean CP duration) is defined for using by the terminal device(s) satisfying certain criteria for random access procedure.

[0011] In some embodiments, the predefined or configured criterion may include a TA determination capability. In an example, the predefined or configured criterion may require that the terminal device can (mostly or) completely determine its TA. This may be e.g., based on capability of the terminal device and network support (and minimum timing advance accuracy). As an example, if the terminal device 110 may obtain the corresponding TA (value) in advance, the terminal device 110 may determine that the criterion is satisfied. As mentioned above, the terminal devices in the LPWA network may obtain its TA before the random access procedure, for example, the terminal device is stationary, is limited in a confined space, is configured to store a previous TA and so on. These terminal devices may determine that the criterion is satisfied.

[0012] In addition, in some embodiments, the predefined or configured criterion may include one or more accuracy level thresholds for a TA determination of the terminal device. As mentioned above, the terminal device in LPWA network may completely or partially determine its TA. As an example, when the TA is “partially” known, e.g., based on some “partial” AI / ML estimate or can be determined by the terminal device 110 to be within some smaller bound, the terminal device 110 may adjust its PRACH preamble transmission timing such that the preamble will arrive more, but not fully, time-aligned at the gNB.

[0013] In this case, if the terminal device 110 is capable of completely determining the TA (which may be also referred to as “the highest degree of accuracy / confidence of TA determination”), the terminal device 110 may select the lean format. As shown in FIG. 3, three lean PRACH occasions may be fitted in one slot (compared to the normal PRACH which only one can be fitted in one slot), such that triples the number ofPRACH opportunities per slot. Alternatively, if the terminal device 110 is capable of determining TA but the TA is partially determined (which may be also referred to as “a medium degree of accuracy / confidence”), the terminal device 110 may select the partially lean format. In an example, two partially lean PRACH occasions may be fitted in one slot (compared to the normal PRACH which only one can be fitted in one slot), such that doubles the number of PRACH opportunities per slot.

[0014] In addition or alternatively, in some embodiments, the predefined or configured criterion may include that the terminal device is configured to use a stored TA. For example, for stationary terminal device that is known to the network (e.g. via service subscription), the network may configure this terminal to use last stored TA and lean PRACH during random access procedure.

[0015] In addition or alternatively, in some embodiments, the predefined or configured criterion may include one or more power thresholds for a received power at the terminal device. In an example, if a reference signal received power (RSRP) which is measured by the terminal device on a reference signal of the serving cell is above or equal to a respective power threshold, the terminal device 110 may determine that that the predefined or configured criterion is satisfied. The reason is that if the RSRP is high, the distance between the terminal device 110 and the network device 120 may be short. In this case, the required TA may be small and the long CP duration is also not required.

[0016] Similarly, in some embodiments, the predefined or configured criterion may include one or more accuracy levels of propagation delay between the terminal device and the network device, which also characterizes the distance information related to the terminal device and the network device.

[0017] In addition or alternatively, to provide additional check to exclude the terminal device that have a good LOS connection with the network device 120 or using some antenna / beamforming gains while being far from the network device 120, the predefined or configured criterion may include one or more power thresholds associated with a neighboring cell. For example, if the received power of a signal from the neighboring cell is below the another respective threshold, the terminal device 110 may determine that the predefined or configured criterion is satisfied.

[0018] In addition or alternatively, in some embodiments, the predefined or configured criterion may include a distance between the terminal device and a reference location. For example, the coverage quality at certain reference location may be high or low, the criterion may require that the terminal device is adjacent to the reference location or far away from the reference signal by a distance.

[0019] Moreover, it is to be understood that the above predefined or configured criterion in this disclosure may include one of the above conditions or any combination of these conditions.

[0020] Regarding the predefined or configured criterion, in some embodiments, the network device 120 may configure this criterion to the terminal device 110. Alternatively, this criterion may be predefined for the terminal device 110 and the network device 120. That is, the above predefined or configured criterion may be configured by the network or predefined in specification.

[0021] Still referring to FIG. 2, the terminal device 110 transmits (260) to the network device 120 a PRACH transmission 265 based on the selected format or the selected CP duration. In some embodiments, if the selected format is the lean format or the selected CP duration is the lean CP duration, the terminal device 110 may transmit the PRACH transmission in a time unit configured for the lean format. In some embodiments, the network device 120 may estimate a percentage of PRACH attempts using at least one or more of a lean format, a partially lean format, a lean CP duration or a partially lean CP duration in a cell. Then, the network device 120 may determine, based on the percentage, a set of time units supporting the at least one or more of a lean format, a partially lean format, a lean CP duration or a partially lean CP duration.

[0022] As an example, the network may estimate that approximately 30% of PRACH attempts at a given cell come from LPWA devices with sufficiently good knowledge of their TA. To estimate this percentage, the network may calculate the number of validated lean PRACH attempts (the embodiments regarding the validation of whether the lean format is allowed to be used will be described with reference to FIG. 5 in the following), and normalizes this number over the estimated total number of PRACH attempts. The volume of (partially-) lean PRACH formats may be configured in an iterative fashion, such that the network initially starts with 100% normal PRACH formats and gradually decrease / increase the percentage of normal / lean PRACH formats, based on the volume of validated UEs that can use lean PRACH. Then, the network device 120 may partition the slots supporting normal and lean PRACH formats based on the above estimated number. In the above example, the network may configure 30% of the slots to support lean PRACH format, and the remaining slots to support normal PRACH format. Then, the network device 120 receives (270) the PRACH transmission 265 based on the selected format or selected CP duration accordingly.

[0023] In addition, in some embodiments, a fall back mechanism may be introduced for the (partially) lean format or (partially)lean CP duration. In an example, there may be a failure number threshold. The terminal device 110 may determine that a number of failed random access attempts exceeds a failure number threshold. In this case, the terminal device 110 will not use the lean format, partially lean format, lean CP duration and / or partially lean CP duration (which may be collectively referred to as “a first format / CP duration” in some embodiments) any more even if the criterion is satisfied. For the next random access attempt, the terminal device 110 may select the normal format or normal CP duration.

[0024] Alternatively, in some embodiments, the network device 120 may indicate the terminal device 110 to use the normal format or normal CP duration (which may be referred to as “a second format / CP duration” in some embodiments). For example, the network device 120 may transmit an instruction to fall back to a normal format or a normal CP duration. In this case, the terminal device 110 may select the normal format or normal CP duration for the next PRACH transmission.

[0025] Only for discussion purposes, another example of signaling process associated with the above embodiments is shown in FIG. 4. FIG. 4 illustrates a second example signaling process 400 for random access in the LPWA network according to example embodiments of the present disclosure.

[0026] In the signaling process 400, at 410, the terminal device 110 may receive SSB from the network device 120. At 420, the terminal device 110 may receive system information block 1 (SIB1) including normal PRACH configuration (e.g., the normal format), lean PRACH configuration (e.g., the lean format) and criterion for the selection of PRACH format (e.g., the criterion mentioned above). At 430, the terminal device 110 may determine the PRACH type or format based on the criterion. Then, if the lean PRACH configuration is selected, at 440, the terminal device 110 may transmit Msg 1 using the lean PRACH format.

[0027] In view of the above, a lean PRACH format is proposed for UE that meets certain criteria (e.g. if UE can (mostly or) completely determine its own TA). This lean format features a significantly shorter cyclic prefix (CP) and potentially eliminates the guard time (GT). As a result, its time duration is much shorter and therefore more PRACH opportunities can be supported for the same network overhead.

[0028] As mentioned above, in a second aspect, whether the lean PRACH format or lean CP duration is allowed to be used can be validated at first. For example, when the terminal device accesses to the cell for the first time or the terminal device moves to another location after the previous access procedure, the terminal device may validate with the network device whether the lean format is allowed to be used, since the TA of the terminal device may be changed. That is, the terminal device can first validate with the network prior to using the lean PRACH format.

[0029] FIG. 5 illustrates a third example signaling process 500 for random access in the LPWA network according to example embodiments of the present disclosure. For the purpose of discussions, the signaling process 500 will be described with reference to FIG. 1 A. It would be appreciated that although the signaling process 500 has been described in the communication environment 100 of FIG. 1A, this signaling process 500 may be likewise applied to other communication scenarios.

[0030] In the signaling process 500, the network device 120 transmits (510) configuration information 215 including multiple formats or multiple cyclic prefixes (CP) durations for a physical random access channel (PRACH). The multiple formats are different with each other at least in a CP duration. In some embodiments, the configuration information 515 may be same as the configuration information 215 discussed with reference to FIG. 2.

[0031] The terminal device 110 receives (520) the configuration information 515 accordingly. Then, the terminal device 110 transmits (530) to the network device 120 a request 535 for validating whether the terminal device 110 is allowed to use a first format of the multiple formats or a first cyclic prefix (CP) duration of the multiple CP durations. In some embodiments, the first format may be the (partially) lean format mentioned above, and the first CP duration may be the (partially) lean CP duration mentioned above.

[0032] In some embodiments, the terminal device 110 may transmit the request 535 during a random access procedure. For example, the validation is performed as part of the random access procedure. Specifically, when the first time the terminal device 110 accesses the cell, it may use a normal PRACH format and then validates with the cell whether it can use the lean PRACH. This would allow the network device120 to check whether the terminal device 110 is allowed to use the lean PRACH format (e.g. check that UE’s calculated TA is valid). In another example, the terminal device 110 may also validate with the cell whether it can use the lean PRACH in another random access procedures other than the first time as a part of the other random access procedure, since the terminal device may move to another place which may cause TA changes. In some embodiments, this validation may be per cell, per group of cells (e.g. cells belonging to a RAN notification area), or per network (e.g. PLMN). As mentioned above, the network device 120 may configure the terminal device 110 to use the lean PRACH format. For example, for stationary UE that is known to the network (e.g. via service subscription), the network device 120 may configure the terminal device 110 to use last stored TA and lean PRACH during random access procedure.

[0033] Alternatively, the validation may be also performed in other steps, for instance, as part of the RRC Release procedure. For example, the request 535 may be transmitted by the terminal device 110 in Msg 3 of the random access procedure. In some other embodiments, the terminal device 110 may transmit the request in any other messages.

[0034] In some embodiments, based on determining whether the TA of the terminal device 110 is valid, the network device 120 may determine the validation result. For example, if the network device 120 determine that the TA of the terminal device 110 is valid, the network device 120 may determine the validation result as positive. Otherwise, the network device 120 may determine the validation result as negative. The TA of the terminal device 110 may be indicated in the request message 535, or may be determined by the network device 120 based on the received UL transmission.

[0035] Then, the network device 120 transmits (550) an indication 555 of a validation result to the terminal device 110. In some embodiments, the network device 120 may transmit the indication of the validation result in Msg 4 in the random access procedure. Alternatively, in some embodiments, the network device 120 may transmit the indication of the validation result in connection release message, for example, RRCConnectionRelease message. For example, the network device 120 may receive the request during connection release procedure from the terminal device 110. Then, the network device 120 may transmit, to the terminal device, a connection release message comprising the indication of the validation result.

[0036] After receiving (560) the indication 555, the terminal device may perform the subsequent random access procedure(s) based on the validation result. The terminal device 110 selects (570) a format from the multiple formats or selects (570) a CP duration from the multiple CP durations based on the validation result.

[0037] For example, if the validation result is positive, the terminal device 110 may determine whether to use the lean format or lean CP duration based on the criterion related to the TA, in the same way as discussed with reference to FIG. 2. Otherwise, the terminal device 110 may perform the random access procedure based on the normal PRACH format.

[0038] Then, the terminal device 110 performs (580) a PRACH transmission 585 based on the selected format or selected CP duration to the network device 120. The network device 120 receives (590) the PRACH transmission 585 from the terminal device 110 accordingly.

[0039] Only for discussion purposes, another example of signaling associated with the above embodiments is shown in FIG. 6. FIG. 6 illustrates a third example signaling process 600 for random access in the LPWA network according to example embodiments of the present disclosure.

[0040] In the signaling process 600, at 610, the terminal device 110 may receive SSB. At 615, the terminal device 110 may receive SIB1 including normal PRACH configuration (e.g., the normal format), lean PRACH configuration (e.g., the lean format) and criterion for the selection of PRACH format (e.g., the criterion mentioned above). At 620, if it is the first time accessing this cell, the terminal device 110 may select normal PRACH format for performing the random access procedure. At 625, 630, 635 and 640, the terminal device 110 may perform a four-step random access procedure with the network device. Moreover, the terminal device 110 may transmit the request for validating in Msg 3. The network device 120 may transmit the validation result in Msg 4 or in below RRC release message. After the RRC setup completing at 645, the terminal device and network device may perform UL / DL transmissions. At 655, the terminal device 110 may release the connection to the network device 120, and transition to the idle state or inactive state at 660. At 665, when data to be transmitted arrives or the terminal device 110 is paged, the terminal device 110 may perform a next random access procedure. Based on the validation result and the criterion mentioned above, the terminal device 110 may check whether it can use lean PRACH type of format at 670. Then, at 675, the terminal device 110 may transmit Msg1 using lean PRACH format (e.g., the validation result is positive and the criterion is satisfied).

[0041] In addition, there may be another solution for enhancing the UL capacity in the random access procedure. As mentioned above, in the third aspect, the terminal devices may apply a further timing offset in addition to their respective obtained TAs. This means that the PRACH transmission will arrive synchronized in the uplink, except for the selected timing offset by the terminal device. By analyzing the timing offset, the network device can distinguish between multiple UEs transmitting using the same preamble.

[0042] FIG. 7 illustrates a fifth example signaling process for random access in the LPWA network according to example embodiments of the present disclosure. For the purpose of discussions, the signaling process 700 will be described with reference to FIG. 1 A. It would be appreciated that although the signaling process 700 has been described in the communication environment 100 of FIG. 1A, this signaling process 700 may be likewise applied to other communication scenarios.

[0043] In the signaling process 700, the network device 120 transmits (710) configuration information 715 comprising a set of preambles associated with a timing adjustment. In some embodiments, the set of preambles may be a reserved preamble group which is in association with a further timing adjustment in addition to the TA. In an example, if the terminal device that knows or is able to determine its TA selects apreamble from the set of preambles for transmitting the PRACH, the terminal device may apply the TA and a further timing offset to the PRACH. In some embodiments of the disclosure, the usage of this set of preambles needs to satisfy the usage criterion.

[0044] The terminal device 110 determines (750) whether the criterion related to the usage of the set of preambles and a set of timing offsets is satisfied. In some embodiments, the criterion requires that the terminal device 110 is able to obtain its TA in advance. For example, the criterion may include a TA determination capability. If the terminal device is able to determine its TA, the terminal device 110 may determine that the criterion is satisfied. In another example, criterion may include that the terminal device is configured to use a stored TA. As similar to the solution discussed with reference to FIG. 2, the terminal device 110 may be configured by the network device 120 to use TA that is stored during the previous accessing. In this case, the terminal device 110 may determine that the criterion is satisfied.

[0045] If the terminal device 110 determines that the criterion is satisfied, the terminal device 110 may use the set of preambles for initiating the random access procedure. For example, in the case that the criterion is satisfied, the terminal device 110 selects (760) a preamble among the set of preambles. Further, the terminal device 110 selects (770) a first timing offset from the set of timing offsets (for example, a list of timing offsets).

[0046] Otherwise, the terminal device will not use this set of preambles. For example, in the case that the criterion is not satisfied, once the terminal device 110 is to initiate the random access procedure, the terminal device 110 can select a preamble from another set of preambles (e.g., a normal set of preambles which is not in association with the timing adjustment feature).

[0047] In some embodiments, the set of timing offsets may be configured by the network device 120. For example, the network device 120 may broadcast a group of preambles that can be selected by UE satisfying certain criteria. Furthermore, the network device 120 may broadcast a list of timing offsets that can be used by above terminal devices.

[0048] Alternatively, in some embodiments, the set of timing offsets may be predefined, e.g., in the specification. Alternatively, in some embodiments, the set of timing offsets may be determined by the terminal device 110 itself.

[0049] To discuss clarity, the above criterion related to the usage of the set of preambles and the set of offsets may be referred to as a first criterion in some embodiments. In addition, in some embodiments, the terminal device may select the first timing offset from the set of timing offsets based on a second criterion.

[0050] In some embodiments, the second criterion may include that the terminal device 110 may select the first timing offset randomly. In addition or alternatively, the second criterion may include that the terminal device 110 may select the first timing offset from the set of timing offsets based on a location of the terminal device 110. As an example, the network device 120 may transmit a mapping table of multiple reference locations and their corresponding timing offsets. The terminal device 110 may choose the timingoffset that corresponds to its nearest reference point. As an example, the terminal device 110 may determine a reference location from the multiple reference locations based on the location of the terminal device. The determined reference location may be the reference location nearest to the terminal device’s location. Then, the terminal device 110 may select, among the multiple timing offsets corresponding to the multiple reference locations, the first timing offset which corresponds to the determined reference location.

[0051] In addition or alternatively, the second criterion may include that the terminal device 110 may select the first timing offset based on the TA determined by the terminal device, or channel delay profile estimation. As an example, in the case of random selection of an offset value, the list of timing offsets that are eligible for use by a terminal may also depend on the channel delay profile estimation of the terminal device. Specifically, if the terminal device’s estimate of its channel delay profile is larger than some threshold, then the terminal device may only be able to use even numbered offsets, since the preamble transmission may be spread / wide enough to occupy that offset and the subsequent offset. This is intended to achieve benefits more similar to slotted ALOHA, not pure aloha where pure aloha has more collisions due to increased chances of partial overlap in time of subsequent terminal device’s transmissions. In some embodiments, the terminal device may estimate it preamble spread using e.g. AI / ML, location and history of channel delay profile at that location, reciprocity / observations of the DL, etc.

[0052] After determining the preamble and the first timing offset, the terminal device 110 transmit (780) a physical random access channel (PRACH) transmission 785 comprising the determined preamble. Moreover, for the PRACH transmission 785, the terminal device 110 applies a timing adjustment including the TA and the determined first timing offset to the PRACH. The network device 120 receives (790) the PRACH transmission 785 with the above timing adjustment accordingly. To discuss clarity, the functionality of the first timing offset is further discussed with FIGS. 8(a) and 8(b).

[0053] FIG. 8A illustrates PRACH reception at the network device for terminal devices that know TAs and use the same preamble and apply the TAs.

[0054] As shown in FIG. 8A, when the terminal devices that know their TAs transmit the same preamble in the PRACH transmission. The PRACH transmissions may arrive at the network device 120 at the same time almost based on the correct TA adjustment for UL synchronization. Thus, the network device cannot distinguish the collided multiple same preambles in the PRACH receiver window at the network device 120. In this case, the random access attempt may fail.

[0055] FIG. 8B illustrates PRACH reception at the network device for terminal devices that know TAs, use the same preamble and apply both the TAs and a timing offset according to example embodiments of the present disclosure.

[0056] As shown in FIG. 8B, by applying the first timing offset in addition to the TA, the PRACHs including the same preamble is able to be distinguished in the time domain during the PRACH receiver window. Insome embodiments, to achieve this distinguishment, a timing offset of the set of timing offsets is larger than a maximum multipath delay spread and / or OFDM CP length.

[0057] Referring back to FIG. 7, the network device 120 may detect the first timing offset based on the received PRACH transmission 775. Then, the network device 120 may transmit a random access response (RAR) message comprising the detected first timing offset. For example, in the example of FIG. 8B, the network device 120 may transmit RAR messages including a respective detected timing offset to UE1, UE2 and UE3. For UE1 , the RAR message may include no timing offset or, equivalently, delay by 0 offset unit. For UE2, the RAR message may include delay by 1 offset unit. For UE3, the RAR message may include delay by 3 offset units. In this case, even if UE1, UE2 and UE3 use the same preamble, the RAR message can be detected successfully based on random access preamble identifier (RAPID) and the detected timing offset.

[0058] In some embodiments, the network device 120 may transmit the RAR message containing both the preamble ID and detected timing offset. Once the terminal device 110 detects a RAR message including the expected RAPID, the terminal device 110 may determine whether the timing offset (which may be also referred to as a second timing offset in some embodiments) included in the RAR message matches with the first timing offset applied by the terminal device 110. Based on determining that the second timing offset matches with the first timing offset, the terminal device 110 may determine that the RAR message is destined to the terminal device 110. Otherwise, the terminal device 110 may determine that the RAR message is not destined to the terminal device 110.

[0059] In this way, the network transmits Random Access Response (RAR) containing both the preamble ID and detected timing offset. The terminal device determines its associated RAR grant based on both parameters. As such, there may be multiple RAR for the multiple timing offsets associated with a particular “shared” preamble.

[0060] In addition, in some embodiments, for the case that the terminal device 110 capable of mostly determining its own TA, but there is still some smaller remaining TA error to be resolved, the RAR feedback may enable the terminal device 110 to further correct its TA by adjusting its timing relative to its intended timing within the receiver window. For example, the RAR message may include information for correcting the TA of the terminal device 110.

[0061] In addition, in some embodiments, the medium access control (MAC) RAR may no longer needs to contain the Timing Advance value, and thus more bits can be used for the UL grant or another field. To discuss clarity, an example of MAC RAR is further discussed with reference to FIG. 9. FIG. 9 illustrates an example of a portion of a random access response (RAR) according to example embodiments of the present disclosure.

[0062] As shown in FIG. 9, the MAC RAR may include both RAPID and the timing offset 910, in order to that the terminal devices using the same preamble to detect the correct RAR. In an example, the MACRAR no longer needs to contain the Timing Advance value (not shown) in and thus more bits can be used for the UL grant or another field (e.g. power control). Alternatively, as mentioned above, the RAR message may include information for correcting TA, and the TA field may still be present but fewer bits can be used for small residual correction for TA.

[0063] In addition, as similar to the “fall back” mechanism discussed in FIG. 2, a fall back mechanism may be determined for the set of preambles. As an example, if the terminal device 110 determines that a number of failed random access attempts exceeds a failure number threshold. The terminal device 110 may select another preamble from another set of preambles other than the set of preambles associated with the timing adjustment. Then, the terminal device 110 may perform, to the network device, a subsequent random access procedure by transmitting a PRACH comprising the other preamble. That is, if the terminal device did not receive random access response after several tries, it may fallback to using PRACH preamble group without timing offset.

[0064] Only for discussion purposes, another example signaling process related to the set of preambles is shown in FIG. 10. FIG. 10 illustrates a sixth example signaling process 1000 for random access in the LPWA network according to example embodiments of the present disclosure.

[0065] In the signaling process 1000, similarly, the terminal device 110 receives SSB and SIB1 at 1010 and 1015. Compared to FIG. 6, the SIB 1 includes the set of preambles, a usage / selection criterion for the set of preambles (e.g., the criterion discussed in FIG. 9) and a list of timing offsets for the set of preambles, rather than the lean PRACH format.

[0066] At 1020, the terminal device 110 may determine whether to use the set of preambles based on the criterion. At 1025, if the set of preambles can be used by the terminal device 110 based on the criterion, the terminal device 110 may randomly select a preamble and randomly select a timing offset. At 1030, the terminal device 110 may transmit Msg 1 which is adjusted based on the TA of the terminal device 110 and the selected timing offset.

[0067] At 1035, the terminal device 110 may detect a RAR including both the RAPID and a timing offset. At 1040, the terminal device 110 may check whether both the RAPID and timing offset are matched. If it is matched, the terminal device may proceed with the following steps 1045 and 1050 for the random access procedure. After the setup is completed at 1055, the terminal device and network device may perform the data transmission with each other.

[0068] In addition, as similar to the second aspect, the terminal device 110 may first validate with the network device 120 whether the terminal device 110 is allowed to use the set of preambles. That is, the terminal device may first validate with the network prior to using the reserved preamble group with timing offset.

[0069] FIG. 11 illustrates a seventh example signaling process 1100 for random access in the LPWA network according to example embodiments of the present disclosure. For the purpose of discussions, thesignaling process 1100 will be described with reference to FIG. 1A. It would be appreciated that although the signaling process 1100 has been described in the communication environment 100 of FIG. 1A, this signaling process 1100 may be likewise applied to other communication scenarios.

[0070] In the signaling process 1100, the network device 120 transmits (1110) configuration information 1115 comprising a set of preambles associated with a timing adjustment. Accordingly, the terminal device 110 receives (1120) the configuration information 1115. Then, the terminal device 110 transmits (1130) a request 1135 for validating whether the terminal device is allowed to use the set of preambles. In turn, the network device 120 transmits (1150) an indication 1155 of the validation result to the terminal device 110.

[0071] In some embodiments, the request may include information related to a timing advance (TA) of the terminal device. The network device 120 may determine, based on the information, whether a TA determination of the terminal device is valid. Based on determining that the TA determination is valid, the network device 120 may transmit the indication 555 indicating that the validation result is positive to the terminal device 110. Otherwise, the network device 120 may transmit the indication indicating that the validation result is negative. Then, the terminal device 110 receives (1160) the indication 1155 accordingly.

[0072] Then, based on the validation result, the terminal device 110 may determine whether to use the set of preambles for the random access procedure. In an example, if the validation result is positive, the terminal device 110 may further determine whether to use the set of preambles based on criterion related usage of the set of preambles and a set of timing offsets, in the same way discussed in FIG. 7. As some examples, the terminal device 110 may further determine whether to use the set of preambles associated with the timing adjustment based on the criterion (which may be referred to as the first criterion) related to the usage of the set of preambles and the set of timing offsets, as mentioned above. If the first criterion is satisfied, the terminal device 110 may select a preamble from the set of preambles. Furthermore, the terminal device 110 may select a timing offset from the set of timing offsets, for example, based on a second criterion. Then, the terminal device and network device may perform the other similar steps as discussed with reference to FIG. 7.

[0073] In addition, in some embodiments, the other operations upon the terminal device selects a preamble from the set of preambles may be similar or same to corresponding operations discussed in FIGS.7 to 10. Otherwise, if the validation result is negative, the terminal device 110 cannot use this set of preambles. In this case, the terminal device 110 may select a preamble from a normal set of preambles (e.g., which is not associated with the timing adjustment).

[0074] In view of the above, by means of the lean format or a set of preambles associated with the timing adjustment, the PRACH capacity of the network is increased without having to increase the PRACH resource overhead.

[0075] FIG. 12 illustrates a flowchart 1200 of a method implemented at a terminal device according to some embodiments of the present disclosure. The terminal device performing the method 1200 may be an example of the terminal device 110 above.

[0076] At 1210, the terminal device 110 receives, from a network device 120, configuration information comprising multiple formats or multiple cyclic prefix (CP) durations for a physical random access channel (PRACH). The multiple formats are different with each other at least in a CP duration.

[0077] At 1220, the terminal device 110 selects, based on a predefined or a configured criterion, a format from the multiple formats or a CP duration from the multiple CP durations. At 1230, the terminal device 110 performs, to the network device 120, a PRACH transmission based on the selected format or the selected CP duration.

[0078] In some embodiments, the terminal device may select the format or CP duration by determining whether the predefined or configured criterion is satisfied and one of the following: based on determining that the criterion is satisfied, selecting a first format from a set of formats within the multiple formats as the selected format, or selecting a first CP duration from a set of CP durations within the multiple CP durations as the selected CP duration; or based on determining that the criterion is not satisfied, selecting a second format from another set of formats within the multiple formats as the selected format, or selecting a second CP duration from another set of CP durations within the multiple CP durations as the selected CP duration.

[0079] In some embodiments, the set of formats comprises one or more of a lean format and a partially lean format. The lean format includes a short CP duration and the partially lean format includes a medium CP duration longer than the short CP duration, at least one of the lean format and the partially lean format comprises no guard period (GP). In some embodiments, the other set of formats comprises a normal format, wherein the normal format includes a normal CP duration longer than the medium CP duration. In some embodiments, the set of CP durations comprises one or more of a lean CP duration and the partially lean CP duration longer than the lean CP duration. In some embodiments, the other set of CP durations comprises a normal CP duration longer than the partially lean CP duration.

[0080] In some embodiments, the set of formats comprises the lean format and the partially lean format, the criterion comprises accuracy of a TA determination of the terminal device, and the terminal device may select the first format or the first CP duration by the following: based on determining that the accuracy is higher than or equal to an accuracy threshold, determining a lean format among the set of formats as the first format or a lean CP duration from the set of formats as the first CP duration; or based on determining that the accuracy is lower than the accuracy threshold, determining a partially lean format among the set of formats as the first format or a partially lean CP duration from the set of CP durations as the first CP duration.

[0081] In some embodiments, the criterion comprises at least one of the following: a TA determination capability; one or more accuracy level thresholds for a TA determination of the terminal device; the terminal device being configured to use a stored TA; one or more power thresholds for a received power at the terminaldevice; one or more power thresholds associated with a neighboring cell; a distance between the terminal device and a reference location; or one or more accuracy levels of propagation delay between the terminal device and the network device.

[0082] In some embodiments, the terminal device may further receive the criterion from the network device. In some embodiments, the criterion is predefined.

[0083] In some embodiments, the selected format is a first format of the multiple formats, or the selected CP duration is a first CP duration of the multiple CP durations, and the terminal device may further: determine that a number of failed random access attempts using the first format or first CP duration exceeds a failure number threshold; select a second format from the multiple formats or a second CP duration from multiple CP durations, wherein a CP duration of the second format is longer than a CP duration of the first format, or the second duration is longer than the first CP duration; and perform, to the network device, a subsequent random access procedure by transmitting a PRACH based on the normal format or the normal CP duration.

[0084] In some embodiments, the selected format is a first format of the multiple formats, or the selected CP duration is a first CP duration of the multiple CP durations, and the terminal device may further: receive, from the network device, an instruction to fall back to a second format or a second CP duration, wherein a CP duration of the second format is longer than a CP duration of the first format, or the second duration is longer than the first CP duration; and perform, to the network device, a subsequent random access by transmitting a PRACH based on the second format or the second CP duration.

[0085] FIG. 13 illustrates a flowchart 1300 of a method implemented at a network device according to some embodiments of the present disclosure. The network device performing the method 600 may be an example of the network device 120 above.

[0086] At 1310, the network device 120 transmits, to a terminal device 110, configuration information comprising multiple formats or multiple cyclic prefixes (CP) durations for a physical random access channel (PRACH). The multiple formats are different with each other at least in a CP duration. At 1320, the network device 120 transmits, to the terminal device, a predefined or configured criterion. At 1330, the network device 120 performs, from the terminal device, a reception of a PRACH transmission that is based on a format of the multiple formats or a CP duration of the multiple CP durations.

[0087] In some embodiments, the multiple formats comprise a set of formats for a terminal device satisfying the criterion and another set of formats for a terminal device not satisfying the criterion; or the multiple CP durations comprise a set of CP durations for the terminal device satisfying the criterion and another set of CP durations for the terminal device not satisfying the criterion.

[0088] In some embodiments, the set of formats comprises one or more of a lean format and a partially lean format. The lean format includes a short CP duration and the partially lean format includes a medium CP duration longer than the short CP duration, at least one of the lean format and the partially lean format comprises no guard period (GP). In some embodiments, the other set of formats comprises a normal format,wherein the normal format includes a normal CP duration longer than the medium CP duration. In some embodiments, the set of CP durations comprises one or more of a lean CP duration and the partially lean CP duration longer than the lean CP duration. In some embodiments, the other set of CP durations comprises a normal CP duration longer than the partially lean CP duration.

[0089] In some embodiments, the criterion comprises at least one of the following: a TA determination capability; one or more accuracy level thresholds for a TA determination of the terminal device; the terminal device being configured to use a stored TA; one or more power thresholds for a received power at the terminal device; one or more power thresholds associated with a neighboring cell; a distance between the terminal device and a reference location; or one or more accuracy levels of propagation delay between the terminal device and the network device.

[0090] In some embodiments, the network device may transmit the configuration information comprising the multiple formats or multiple CPs based on at least one of the following: a size of cell; one or more coverage enhancement levels supported by the cell; or a load status of the cell.

[0091] In some embodiments, the network device may further estimate a percentage of PRACH attempts using at least one or more of a lean format, a partially lean format, a lean CP duration or a partially lean CP duration in a cell; and determine, based on the percentage, a set of time units supporting the at least one or more of a lean format, a partially lean format, a lean CP duration or a partially lean CP duration.

[0092] In some embodiments, the format for the PRACH transmission is a first format of the multiple formats, or the CP duration for the PRACH transmission is a first CP duration of the multiple CP durations, and the network device may further transmit, based on a TA detection, an instruction to fall back to a second format or a second CP duration to the terminal device, wherein a CP duration of the second format is longer than a CP duration of the first format, or the second duration is longer than the first CP duration.

[0093] FIG. 14 illustrates a flowchart 1400 of a method implemented at a terminal device according to some embodiments of the present disclosure. The terminal device performing the method 1400 may be an example of the terminal device 110 above.

[0094] At 1410, the terminal device 110 receives, from a network device, configuration information comprising multiple formats or multiple cyclic prefixes (CP) durations for a physical random access channel (PRACH). The multiple formats are different with each other at least in a CP duration.

[0095] At 1420, the terminal device 110 transmits, to the network device, a request for validating whether the terminal device is allowed to use a first format of the multiple formats or a first cyclic prefix (CP) duration of the multiple CP durations. At 1430, the terminal device 110 receives an indication of a validation result from the network device. At 1440, the terminal device 110 selects, based on the validation result, a format from the multiple formats or a CP duration from the multiple CP durations. At 1450, the terminal device 110 performs, to the network device, a PRACH transmission using the selected format or selected CP duration.

[0096] In some embodiments, the terminal device may transmit the request by the following: transmitting a Message 3 (Msg3) comprising the request in a first random access procedure

[0097] In some embodiments, the terminal device may further perform, in a random access procedure, another PRACH transmission based on a second format of the multiple formats or a second CP duration of the multiple CP durations, wherein a CP duration of the second format is longer than another CP duration of the first format, and the second CP duration is longer than the first CP duration.

[0098] In some embodiments, the terminal device may receive the indication of the validation result by the following: receiving, from the network device, a Message 4 (Msg4) comprising the indication of the validation result in the first random access procedure.

[0099] In some embodiments, the terminal device may receive the indication of the validation result by the following: transmitting, to the network device, the request during connection release procedure; and receiving, from the network device, a connection release message comprising the indication of the validation result.

[0100] In some embodiments, the terminal device may select the format or the CP duration by the following: based on that the validation result is indicated as positive, select a format from the multiple formats or a CP duration from the multiple CP durations based on a predefined or configured criterion.

[0101] In some embodiments, the terminal device may select the format of the CP duration by the following: determining whether the predefined or configured criterion is satisfied; based on determining that the predefined or configured criterion is satisfied, selecting the first format from a set of formats within the multiple formats as the selected format, or selecting the first CP duration from a set of CP durations within the multiple CP durations as the selected CP duration; and based on determining that the predefined or configured criterion is unsatisfied, selecting a second format from another set of formats within the multiple formats as the selected format, or selecting a second CP duration from another set of CP durations within the multiple CP durations as the selected CP duration.

[0102] In some embodiments, the set of formats comprises one or more of a lean format and a partially lean format, wherein the lean format includes a short CP duration and the partially lean format includes a medium CP duration longer than the short CP duration, at least one of the lean format and the partially lean format comprise no guard period (GP), the other set of formats comprises a normal format, wherein the normal format includes a normal CP duration longer than the medium CP duration, the set of CP durations comprises one or more of a lean CP duration and the partially lean CP duration longer than the lean CP duration, and / or the other set of CP durations comprises a normal CP duration longer than the partially lean CP duration.

[0103] In some embodiments, the predefined or configured criterion comprises at least one of the following: a TA determination capability; one or more accuracy level thresholds for a TA determination of the terminal device; the terminal device being configured to use a stored TA; one or more power thresholds for a received power at the terminal device; one or more power thresholds associated with a neighboring cell; a distancebetween the terminal device and a reference location; or one or more accuracy levels of propagation delay between the terminal device and the network device.

[0104] FIG. 15 illustrates a flowchart 1500 of a method implemented at a network device according to some embodiments of the present disclosure. The network device performing the method 1500 may be an example of the network device 120 above.

[0105] At 1510, the network device 120 transmits, to a terminal device, configuration information comprising multiple formats or multiple cyclic prefixes (CP) durations for a physical random access channel (PRACH), wherein the multiple formats are different with each other at least in a CP duration. At 1520, the network device 120 receives, from the terminal device, a request for validating whether a first format of the multiple formats or a first cyclic prefix (CP) duration of the multiple CP durations can be used. At 1530, the network device 120 transmits an indication of a validation result to the terminal device. At 1540, the network device 120 receives, from the terminal device, a PRACH transmission using a format or CP duration that is selected from the multiple formats or multiple CP durations based on the validation result.

[0106] In some embodiments, the network device 120 may receive the request by receiving a Message 3 (Msg3) comprising the request in a random access procedure. In some embodiments, the network device may receive, in the random access procedure, a first PRACH being based on a second format of the multiple formats or a second CP duration of the multiple CP durations. A CP duration in the second format is longer than another CP duration in the first format, and the second CP duration is longer than the first CP duration.

[0107] In some embodiments, the network device may transmit the indication of the validation result by the following: transmitting, to the terminal device, a Message 4 (Msg4) comprising the indication of the validation result during the first random access procedure.

[0108] In some embodiments, the network device may transmit the indication of the validation result by the following: receiving, from the terminal device, the request during connection release procedure; and transmitting, to the terminal device, a connection release message comprising the indication of the validation result.

[0109] In some embodiments, the multiple formats comprise a set of formats for a terminal device satisfying a predefined or configured criterion and another set of formats for a terminal device not satisfying the predefined or configured criterion; or the multiple CP durations comprise a set of CP durations for the terminal device satisfying the predefined or configured criterion and another set of CP durations for the terminal device not satisfying the predefined or configured criterion.

[0110] In some embodiments, the set of formats comprises one or more of a lean format and a partially lean format, wherein the lean format includes a short CP duration and the partially lean format includes a medium CP duration longer than the short CP duration, at least one of the lean format and the partially lean format comprise no guard period (GP), the other set of formats comprises a normal format, wherein the normal format includes a normal CP duration longer than the medium CP duration, the set of CP durationscomprises one or more of a lean CP duration and the partially lean CP duration longer than the lean CP duration, and / or the other set of CP durations comprises a normal CP duration longer than the partially lean CP duration.

[0111] In some embodiments, the network device may further transmit to the terminal device the predefined or configured criterion comprises at least one of the following: a TA determination capability; one or more accuracy level thresholds for a TA determination of the terminal device; the terminal device being configured to use a stored TA; one or more power thresholds for a received power at the terminal device; one or more power thresholds associated with a neighboring cell; a distance between the terminal device and a reference location; or one or more accuracy levels of propagation delay between the terminal device and the network device.

[0112] In some embodiments, the network device may transmit the indication of a validation result by the following: determining whether a TA indicated by the terminal device is valid; based on that the TA is valid, transmitting the indication indicating that the validation result is positive; and based on that the TA is invalid, transmitting the indication indicating that the validation result is negative.

[0113] FIG. 16 illustrates a flowchart 1600 of a method implemented at a terminal device according to some embodiments of the present disclosure. The terminal device performing the method 1600 may be an example of the terminal device 110 above.

[0114] At 1610, the terminal device 110 receives, from a network device, configuration information comprising a set of preambles associated with a timing adjustment. At 1620, the terminal device 110 determines whether a criterion related to usage of the set of preambles and a set of timing offsets is satisfied. At 1630, based on determining that the criterion is satisfied, the terminal device 110 selects a preamble from the set of preambles. At 1640, the terminal device 110 selects a first timing offset from the set of timing offsets. At 1650, the terminal device 110 performs, to the network device, a physical random access channel (PRACH) transmission comprising the preamble by applying a timing advance (TA) of the terminal device and the first timing offset.

[0115] In some embodiments, the terminal device may further receive, from the network device, a random access response (RAR) message comprising a second timing offset. In some embodiments, the terminal device may further determine whether the second timing offset matches with the first timing offset. Based on determining that the second timing offset matches with the first timing offset, the terminal device determines that the RAR message is destined to the terminal device. Based on determining that the second timing offset does not match with the first timing offset, the terminal device determines that the RAR message is not destined to the terminal device.

[0116] In some embodiments, the RAR message further comprises: information for correcting the TA of the terminal device. In some embodiments, criterion comprises at least one of the following: a TA determination capability; or the terminal device being configured to use a stored TA.

[0117] In some embodiments, the terminal device may further receive the criterion from the network device. In some embodiments, the criterion related to the usage of the set of preambles and the set of timing offsets is a first criterion, and the terminal device may select the first timing offset based a second criterion.

[0118] In some embodiments, the second criterion comprises at least one of the following: selecting the first timing offset randomly; selecting the first timing offset based on a location of the terminal device; selecting the first timing offset based on the TA determined by the terminal device; or selecting the first timing offset from the set of timing offsets based on channel delay information.

[0119] In some embodiments, the terminal device may select the first timing offset based on the location by the following: receiving, from the network device, a mapping table indicating multiple reference locations and multiple timing offsets corresponding the multiple reference locations; determining a reference location from the multiple reference locations based on the location of the terminal device; and selecting, among the multiple timing offsets, the first timing offset which corresponds to the determined reference location.

[0120] In some embodiments, the terminal device may further: receive the set of timing offsets from the network device. In some embodiments, the set of timing offsets is predefined; or the set of timing offsets is determined by the terminal device. In some embodiments, the second criterion is received from the network device; or the second criterion is predefined.

[0121] In some embodiments, a timing offset of the set of timing offsets is larger than a maximum multipath delay spread.

[0122] In some embodiments, the terminal device may further: determine that a number of failed random access attempts exceeds a failure number threshold; select another preamble from another set of preambles other than the set of preambles associated with the timing adjustment; and perform, to the network device, a subsequent random access procedure by transmitting a PRACH comprising the other preamble.

[0123] FIG. 17 illustrates a flowchart 1700 of a method implemented at a network device according to some embodiments of the present disclosure. The network device performing the method 1700 may be an example of the network device 120 above.

[0124] At 1710, the network device 120 transmits, to a terminal device, configuration information comprising a set of preambles associated with a timing adjustment. At 1720, the network device 120 transmits, to the terminal device 110, a criterion related to usage of the set of preambles and a set of timing offsets. At 1730, the network device 120 receives, from the terminal device, a physical random access channel (PRACH) transmission comprising a preamble among the set of preambles, wherein the PRACH transmission is adjusted based on a timing advance (TA) of the terminal device and a first timing offset.

[0125] In some embodiments, the network device may further: detect the first timing offset based on the received PRACH transmission; transmit, to the terminal device, a random access response (RAR) message comprising the detected first timing offset.

[0126] In some embodiments, the RAR message further comprises: information for correcting the TA of the terminal device. In some embodiments, the criterion comprises at least one of the following: a TA determination capability; or the terminal device being configured to use a stored TA.

[0127] In some embodiments, the network device may further transmit a set of timing offsets for applying a timing adjustment to a PRACH transmission comprising a preamble from the set of preambles.

[0128] In some embodiments, a timing offset of the set of timing offsets is larger than a maximum multipath delay spread. In some embodiments, the criterion related to the usage of the set of preambles and the set of timing offsets is a first criterion, and the network device may further transmit to the terminal device a second criterion for selecting the first timing offset. In some embodiments, the second criterion comprises at least one of the following:

[0129] selecting the first timing offset randomly; selecting the first timing offset based on a location of the terminal device; selecting the first timing offset based on the TA determined by the terminal device; or selecting the first timing offset from the set of timing offsets based on channel delay profile estimation of the terminal device.

[0130] In some embodiments, the network device may further: transmit, to the terminal device, a mapping table indicating multiple reference locations and multiple timing offsets corresponding the multiple reference locations.

[0131] FIG. 18 illustrates a flowchart 1800 of a method implemented at a terminal device according to some embodiments of the present disclosure. The terminal device performing the method 1800 may be an example of the terminal device 110 above.

[0132] At 1810, the terminal device 110 receives, from a network device, configuration information comprising a set of preambles associated with a timing adjustment. At 1820, the terminal device 110 transmits, to the network device, a request for validating whether the terminal device is allowed to use the set of preambles. At 1830, the terminal device 110 receives an indication of a validation result from the network device.

[0133] In some embodiments, the first request comprises information indicating the network device to determine whether the timing advance (TA) determination of the terminal device is valid or not.

[0134] In some embodiments, the validation result is positive, and the terminal device may further: determine whether a criterion related to usage of the set of preambles and a set of timing offsets is satisfied; based on determining that the criterion is satisfied, select a preamble from the set of preambles; select a first timing offset from the set of timing offsets; and perform, to the network device, a physical random access channel (PRACH) transmission comprising the preamble by applying a timing advance (TA) of the terminal device and the first timing offset.

[0135] In some embodiments, the criterion related to the usage of the set of preambles and the set of timing offsets is a first criterion, and the terminal device may select the first timing offset based on a second criterion.

[0136] In some embodiments, the second criterion comprises at least one of the following: selecting the first timing offset randomly; selecting the first timing offset based on a location of the terminal device; selecting the first timing offset based on the TA determined by the terminal device; or selecting the first timing offset from the set of timing offsets based on channel delay information.

[0137] In some embodiments, the second criterion is received from the network device; or the second criterion is predefined.

[0138] In some embodiments, the terminal device may further: receive, from the network device, a random access response (RAR) message comprising a second timing offset; determine whether the second timing offset matches with the first timing offset; based on determining that the second timing offset matches with the first timing offset, determine that the RAR message is destined to the terminal device; and based on determining that the second timing offset does not match with the first timing offset, determine that the RAR message is not destined to the terminal device.

[0139] In some embodiments, the terminal device may further receive the criterion related to the usage the set of preambles and the set of timing offsets from the network device. In some embodiments, the criterion related to the usage the set of preambles and the set of timing offsets is predefined.

[0140] In some embodiments, the terminal device may further: receive the set of timing offsets from the network device. In some embodiments, the set of timing offsets is predefined; or the set of timing offsets is determined by the terminal device.

[0141] FIG. 19 illustrates a flowchart 1900 of a method implemented at a network device according to some embodiments of the present disclosure. The network device performing the method 1900 may be an example of the network device 120 above.

[0142] At 1910, the network device 120 transmits, to a terminal device, configuration information comprising a set of preambles associated with a timing adjustment. At 1920, the network device 120 receives, from the terminal device, a request for validating whether the terminal device is allowed to use the set of preambles. At 1930, the network device 120 transmits an indication of a validation result to the terminal device.

[0143] In some embodiments, the request comprises information indicating the network device to determine whether the timing advance (TA) determination of the terminal device is valid or not.

[0144] In some embodiments, the network device may transmit the indication by the following: determining, based on the information, whether a TA determination of the terminal device is valid; based on determining that the TA determination is valid, transmit the indication indicating that the validation result is positive; andbased on determining that the TA determination is invalid, transmit the indication indicating that the validation result is negative.

[0145] In some embodiments, the indication indicates that the validation result is positive, and the network device may further: transmit, to the terminal device, a criterion related to usage of the set of preambles and a set of timing offsets; and receive, from the terminal device, a physical random access channel (PRACH) transmission comprising a preamble among the set of preambles, wherein the PRACH transmission is adjusted based on a timing advance (TA) of the terminal device and a first timing offset.

[0146] In some embodiments, the network device may further: detect the first timing offset based on the received PRACH transmission; transmit, to the terminal device, a random access response (RAR) message comprising the detected first timing offset.

[0147] In some embodiments, the criterion comprises at least one of the following: a TA determination capability; or the terminal device being configured to use a stored TA.

[0148] In some embodiments, the network device may further: transmit a set of timing offsets to be used for a PRACH transmission comprising a preamble from the set of preambles.

[0149] In some embodiments, the criterion related to the usage of the set of preambles and the set of timing offsets is a first criterion, and the network device may further transmit to the terminal device a second criterion for selecting the first timing offset.

[0150] In some embodiments, the second criterion comprises at least one of the following: selecting the first timing offset randomly; selecting the first timing offset based on a location of the terminal device; selecting the first timing offset based on the TA determined by the terminal device; or selecting the first timing offset from the set of timing offsets based on channel delay profile estimation of the terminal device.

[0151] In some embodiments, an apparatus capable of performing any of the method 1200 (for example, the terminal device) may comprise means for receiving, from a network device, configuration information comprising multiple formats or multiple cyclic prefix (CP) durations for a physical random access channel (PRACH), wherein multiple formats are different with each other at least in a CP duration; means for selecting based on a predefined or configured criterion, a format from the multiple formats or a CP duration from the multiple CP durations; and means for performing, to the network device, a PRACH transmission based on the selected format or the selected CP duration.

[0152] In some embodiments, the means for selecting the format or CP duration may include: means for determining whether the predefined or configured criterion is satisfied and one of the following: means for based on determining that the criterion is satisfied, selecting a first format from a set of formats within the multiple formats as the selected format, or selecting a first CP duration from a set of CP durations within the multiple CP durations as the selected CP duration; or means for based on determining that the criterion is not satisfied, selecting a second format from another set of formats within the multiple formats as the selectedformat, or selecting a second CP duration from another set of CP durations within the multiple CP durations as the selected CP duration.

[0153] In some embodiments, the set of formats comprises one or more of a lean format and a partially lean format. The lean format includes a short CP duration and the partially lean format includes a medium CP duration longer than the short CP duration, at least one of the lean format and the partially lean format comprises no guard period (GP). In some embodiments, the other set of formats comprises a normal format, wherein the normal format includes a normal CP duration longer than the medium CP duration. In some embodiments, the set of CP durations comprises one or more of a lean CP duration and the partially lean CP duration longer than the lean CP duration. In some embodiments, the other set of CP durations comprises a normal CP duration longer than the partially lean CP duration.

[0154] In some embodiments, the set of formats comprises the lean format and the partially lean format, the criterion comprises accuracy of a TA determination of the terminal device, and the means for selecting the first format or the first CP duration may include: means for based on determining that the accuracy is higher than or equal to an accuracy threshold, determining a lean format among the set of formats as the first format or a lean CP duration from the set of formats as the first CP duration; or means for based on determining that the accuracy is lower than the accuracy threshold, determining a partially lean format among the set of formats as the first format or a partially lean CP duration from the set of CP durations as the first CP duration.

[0155] In some embodiments, the criterion comprises at least one of the following: a TA determination capability; one or more accuracy level thresholds for a TA determination of the terminal device; the terminal device being configured to use a stored TA; one or more power thresholds for a received power at the terminal device; one or more power thresholds associated with a neighboring cell; a distance between the terminal device and a reference location; or one or more accuracy levels of propagation delay between the terminal device and the network device.

[0156] In some embodiments, the apparatus may further include means for receiving the criterion from the network device. In some embodiments, the criterion is predefined.

[0157] In some embodiments, the selected format is a first format of the multiple formats, or the selected CP duration is a first CP duration of the multiple CP durations, and the apparatus may further include: means for determining that a number of failed random access attempts using the first format or first CP duration exceeds a failure number threshold; means for selecting a second format from the multiple formats or a second CP duration from multiple CP durations, wherein a CP duration of the second format is longer than a CP duration of the first format, or the second duration is longer than the first CP duration; and means for performing, to the network device, a subsequent random access procedure by transmitting a PRACH based on the normal format or the normal CP duration.

[0158] In some embodiments, the selected format is a first format of the multiple formats, or the selected CP duration is a first CP duration of the multiple CP durations, and the apparatus may further include: means for receiving, from the network device, an instruction to fall back to a second format or a second CP duration, wherein a CP duration of the second format is longer than a CP duration of the first format, or the second duration is longer than the first CP duration; and means for performing, to the network device, a subsequent random access by transmitting a PRACH based on the second format or the second CP duration.

[0159] In some embodiments, the apparatus further comprises means for performing other steps in some embodiments of the method 1200. In some embodiments, the means comprises at least one processor and at least one memory including computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the performance of the apparatus.

[0160] In some embodiments, an apparatus capable of performing any of the method 1300 (for example, the network device) may comprise means for transmitting, to a terminal device, configuration information comprising multiple formats or multiple cyclic prefixes (CP) durations for a physical random access channel (PRACH), wherein multiple formats are different with each other at least in a CP duration; means for transmitting, to the terminal device, a predefined or configured criterion; and means for performing, from the terminal device, a reception of a PRACH transmission that is based on a format of the multiple formats or a CP duration of the multiple CP durations.

[0161] In some embodiments, the multiple formats comprise a set of formats for a terminal device satisfying the criterion and another set of formats for a terminal device not satisfying the criterion; or the multiple CP durations comprise a set of CP durations for the terminal device satisfying the criterion and another set of CP durations for the terminal device not satisfying the criterion.

[0162] In some embodiments, the set of formats comprises one or more of a lean format and a partially lean format. The lean format includes a short CP duration and the partially lean format includes a medium CP duration longer than the short CP duration, at least one of the lean format and the partially lean format comprises no guard period (GP). In some embodiments, the other set of formats comprises a normal format, wherein the normal format includes a normal CP duration longer than the medium CP duration. In some embodiments, the set of CP durations comprises one or more of a lean CP duration and the partially lean CP duration longer than the lean CP duration. In some embodiments, the other set of CP durations comprises a normal CP duration longer than the partially lean CP duration.

[0163] In some embodiments, the criterion comprises at least one of the following: a TA determination capability; one or more accuracy level thresholds for a TA determination of the terminal device; the terminal device being configured to use a stored TA; one or more power thresholds for a received power at the terminal device; one or more power thresholds associated with a neighboring cell; a distance between the terminal device and a reference location; or one or more accuracy levels of propagation delay between the terminal device and the network device.

[0164] In some embodiments, the apparatus may further include means for transmitting the configuration information comprising the multiple formats or multiple CPs based on at least one of the following: a size of cell; one or more coverage enhancement levels supported by the cell; or a load status of the cell.

[0165] In some embodiments, the apparatus may further include means for estimating a percentage of PRACH attempts using at least one or more of a lean format, a partially lean format, a lean CP duration or a partially lean CP duration in a cell; and means for determining, based on the percentage, a set of time units supporting the at least one or more of a lean format, a partially lean format, a lean CP duration or a partially lean CP duration.

[0166] In some embodiments, the format for the PRACH transmission is a first format of the multiple formats, or the CP duration for the PRACH transmission is a first CP duration of the multiple CP durations, and the network device may further transmit, based on a TA detection, an instruction to fall back to a second format or a second CP duration to the terminal device, wherein a CP duration of the second format is longer than a CP duration of the first format, or the second duration is longer than the first CP duration.

[0167] In some embodiments, the apparatus further comprises means for performing other steps in some embodiments of the method 1300. In some embodiments, the means comprises at least one processor and at least one memory including computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the performance of the apparatus.

[0168] In some embodiments, an apparatus capable of performing any of the method 1400 (for example, the terminal device) may comprise means for receiving, from a network device, configuration information comprising multiple formats or multiple cyclic prefixes (CP) durations for a physical random access channel (PRACH), wherein multiple formats are different with each other at least in a CP duration; means for transmitting, to the network device, a request for validating whether the terminal device is allowed to use a first format of the multiple formats or a first cyclic prefix (CP) duration of the multiple CP durations; and means for receiving an indication of a validation result from the network device; means for selecting, based on the validation result, a format from the multiple formats or a CP duration from the multiple CP durations; and means for performing, to the network device, a PRACH transmission using the selected format or selected CP duration.

[0169] In some embodiments, the means for transmitting the request may include: means for transmitting a Message 3 (Msg3) comprising the request in a first random access procedure

[0170] In some embodiments, the apparatus may further include means for performing, in a random access procedure, another PRACH transmission based on a second format of the multiple formats or a second CP duration of the multiple CP durations, wherein a CP duration of the second format is longer than another CP duration of the first format, and the second CP duration is longer than the first CP duration.

[0171] In some embodiments, the means for receiving the indication of the validation result may include: means for receiving, from the network device, a Message 4 (Msg4) comprising the indication of the validation result in the first random access procedure.

[0172] In some embodiments, the means for receiving the indication of the validation result may include: means for transmitting, to the network device, the request during connection release procedure; and means for receiving, from the network device, a connection release message comprising the indication of the validation result.

[0173] In some embodiments, the means for selecting the format or the CP duration may include: means for based on that the validation result is indicated as positive, selecting a format from the multiple formats or a CP duration from the multiple CP durations based on a predefined or configured criterion.

[0174] In some embodiments, the means for selecting the format of the CP duration may include: means for determining whether the predefined or configured criterion is satisfied; means for based on determining that the predefined or configured criterion is satisfied, selecting the first format from a set of formats within the multiple formats as the selected format, or selecting the first CP duration from a set of CP durations within the multiple CP durations as the selected CP duration; and means for based on determining that the predefined or configured criterion is unsatisfied, selecting a second format from another set of formats within the multiple formats as the selected format, or selecting a second CP duration from another set of CP durations within the multiple CP durations as the selected CP duration.

[0175] In some embodiments, the set of formats comprises one or more of a lean format and a partially lean format, wherein the lean format includes a short CP duration and the partially lean format includes a medium CP duration longer than the short CP duration, at least one of the lean format and the partially lean format comprise no guard period (GP), the other set of formats comprises a normal format, wherein the normal format includes a normal CP duration longer than the medium CP duration, the set of CP durations comprises one or more of a lean CP duration and the partially lean CP duration longer than the lean CP duration, and / or the other set of CP durations comprises a normal CP duration longer than the partially lean CP duration.

[0176] In some embodiments, the predefined or configured criterion comprises at least one of the following: a TA determination capability; one or more accuracy level thresholds for a TA determination of the terminal device; the terminal device being configured to use a stored TA; one or more power thresholds for a received power at the terminal device; one or more power thresholds associated with a neighboring cell; a distance between the terminal device and a reference location; or one or more accuracy levels of propagation delay between the terminal device and the network device.

[0177] In some embodiments, an apparatus capable of performing any of the method 1500 (for example, the network) may comprise means for transmitting, to a terminal device, configuration information comprising multiple formats or multiple cyclic prefixes (CP) durations for a physical random access channel (PRACH),wherein the multiple formats are different with each other at least in a CP duration; means for receiving, from the terminal device, a request for validating whether a first format of the multiple formats or a first cyclic prefix (CP) duration of the multiple CP durations can be used; means for transmitting an indication of a validation result to the terminal device; and means for receiving, from the terminal device, a PRACH transmission using a format or CP duration that is selected from the multiple formats or multiple CP durations based on the validation result.

[0178] In some embodiments, the mean for receiving the request may include means for receiving a Message 3 (Msg3) comprising the request in a random access procedure. In some embodiments, the apparatus may receive, in the random access procedure, a first PRACH being based on a second format of the multiple formats or a second CP duration of the multiple CP durations. A CP duration in the second format is longer than another CP duration in the first format, and the second CP duration is longer than the first CP duration.

[0179] In some embodiments, the means for transmitting the indication of the validation result may include: means for transmitting, to the terminal device, a Message 4 (Msg4) comprising the indication of the validation result during the first random access procedure.

[0180] In some embodiments, the means for transmitting the indication of the validation result may include: means for receiving, from the terminal device, the request during connection release procedure; and transmitting, to the terminal device, a connection release message comprising the indication of the validation result.

[0181] In some embodiments, the multiple formats comprise a set of formats for a terminal device satisfying a predefined or configured criterion and another set of formats for a terminal device not satisfying the predefined or configured criterion; or the multiple CP durations comprise a set of CP durations for the terminal device satisfying the predefined or configured criterion and another set of CP durations for the terminal device not satisfying the predefined or configured criterion.

[0182] In some embodiments, the set of formats comprises one or more of a lean format and a partially lean format, wherein the lean format includes a short CP duration and the partially lean format includes a medium CP duration longer than the short CP duration, at least one of the lean format and the partially lean format comprise no guard period (GP), the other set of formats comprises a normal format, wherein the normal format includes a normal CP duration longer than the medium CP duration, the set of CP durations comprises one or more of a lean CP duration and the partially lean CP duration longer than the lean CP duration, and / or the other set of CP durations comprises a normal CP duration longer than the partially lean CP duration.

[0183] In some embodiments, the apparatus may further include means for transmitting to the terminal device the predefined or configured criterion comprises at least one of the following: a TA determination capability; one or more accuracy level thresholds for a TA determination of the terminal device; the terminaldevice being configured to use a stored TA; one or more power thresholds for a received power at the terminal device; one or more power thresholds associated with a neighboring cell; a distance between the terminal device and a reference location; or one or more accuracy levels of propagation delay between the terminal device and the network device.

[0184] In some embodiments, the means for transmitting the indication of a validation result may include: means for determining whether a TA indicated by the terminal device is valid; means for based on that the TA is valid, transmitting the indication indicating that the validation result is positive; and means for based on that the TA is invalid, transmitting the indication indicating that the validation result is negative.

[0185] In some embodiments, the apparatus further comprises means for performing other steps in some embodiments of the method 1500. In some embodiments, the means comprises at least one processor and at least one memory including computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the performance of the apparatus.

[0186] In some embodiments, an apparatus capable of performing any of the method 1600 (for example, the terminal device) may comprise means for receiving, from a network device, configuration information comprising a set of preambles associated with a timing adjustment; means for determining whether a criterion related to usage of the set of preambles and a set of timing offsets is satisfied; means for based on determining that the criterion is satisfied, select a preamble from the set of preambles; means for selecting a first timing offset from the set of timing offsets; and means for performing, to the network device, a physical random access channel (PRACH) transmission comprising the preamble by applying a timing advance (TA) of the terminal device and the first timing offset.

[0187] In some embodiments, the apparatus may further include means for receiving, from the network device, a random access response (RAR) message comprising a second timing offset. In some embodiments, the apparatus may further include means for determining whether the second timing offset matches with the first timing offset; means for based on determining that the second timing offset matches with the first timing offset, the terminal device determines that the RAR message is destined to the terminal device; and means for based on determining that the second timing offset does not match with the first timing offset, the terminal device determines that the RAR message is not destined to the terminal device.

[0188] In some embodiments, the RAR message further comprises: information for correcting the TA of the terminal device. In some embodiments, criterion comprises at least one of the following: a TA determination capability; or the terminal device being configured to use a stored TA.

[0189] In some embodiments, the apparatus may further include means for receiving the criterion from the network device. In some embodiments, the criterion related to the usage of the set of preambles and the set of timing offsets is a first criterion, and the terminal device may select the first timing offset based a second criterion.

[0190] In some embodiments, the second criterion comprises at least one of the following: selecting the first timing offset randomly; selecting the first timing offset based on a location of the terminal device; selecting the first timing offset based on the TA determined by the terminal device; or selecting the first timing offset from the set of timing offsets based on channel delay information.

[0191] In some embodiments, the means for selecting the first timing offset based on the location may include: means for receiving, from the network device, a mapping table indicating multiple reference locations and multiple timing offsets corresponding the multiple reference locations; means for determining a reference location from the multiple reference locations based on the location of the terminal device; and means for selecting, among the multiple timing offsets, the first timing offset which corresponds to the determined reference location.

[0192] In some embodiments, the apparatus may further include: means for receiving the set of timing offsets from the network device. In some embodiments, the set of timing offsets is predefined; or the set of timing offsets is determined by the terminal device. In some embodiments, the second criterion is received from the network device; or the second criterion is predefined.

[0193] In some embodiments, a timing offset of the set of timing offsets is larger than a maximum multipath delay spread.

[0194] In some embodiments, the apparatus may further include: means for determining that a number of failed random access attempts exceeds a failure number threshold; means for selecting another preamble from another set of preambles other than the set of preambles associated with the timing adjustment; and means for performing, to the network device, a subsequent random access procedure by transmitting a PRACH comprising the other preamble.

[0195] In some embodiments, the apparatus further comprises means for performing other steps in some embodiments of the method 1600. In some embodiments, the means comprises at least one processor and at least one memory including computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the performance of the apparatus.

[0196] In some embodiments, an apparatus capable of performing any of the method 1700 (for example, the first terminal device) may comprise means for transmitting, to a terminal device, configuration information comprising a set of preambles associated with a timing adjustment; means for transmitting, to the terminal device, a criterion related to usage of the set of preambles and a set of timing offsets; means for receiving, from the terminal device, a physical random access channel (PRACH) transmission comprising a preamble among the set of preambles, wherein PRACH transmission is adjusted based on a timing advance (TA) of the terminal device and a first timing offset.

[0197] In some embodiments, the apparatus may further include means for detecting the first timing offset based on the received PRACH transmission; and means for transmitting, to the terminal device, a random access response (RAR) message comprising the detected first timing offset.

[0198] In some embodiments, the RAR message further comprises: information for correcting the TA of the terminal device. In some embodiments, the criterion comprises at least one of the following: a TA determination capability; or the terminal device being configured to use a stored TA.

[0199] In some embodiments, the apparatus may further include means for transmitting a set of timing offsets for applying a timing adjustment to a PRACH transmission comprising a preamble from the set of preambles.

[0200] In some embodiments, a timing offset of the set of timing offsets is larger than a maximum multipath delay spread.

[0201] In some embodiments, the apparatus may further include means for transmitting, to the terminal device, a mapping table indicating multiple reference locations and multiple timing offsets corresponding the multiple reference locations.

[0202] In some embodiments, the apparatus further comprises means for performing other steps in some embodiments of the method 1700. In some embodiments, the means comprises at least one processor and at least one memory including computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the performance of the apparatus.

[0203] In some embodiments, an apparatus capable of performing any of the method 1800 (for example, the terminal device) may comprise means for receiving, from a network device, configuration information comprising a set of preambles associated with a timing adjustment; means for transmitting, to the network device, a request for validating whether the terminal device is allowed to use the set of preambles; and means for receiving an indication of a validation result from the network device.

[0204] In some embodiments, the first request comprises information indicating the network device to determine whether the timing advance (TA) determination of the terminal device is valid or not.

[0205] In some embodiments, the validation result is positive, and the apparatus may further include: means for determining whether a criterion related to usage of the set of preambles and a set of timing offsets is satisfied; means for based on determining that the criterion is satisfied, selecting a preamble from the set of preambles; means for selecting a first timing offset from the set of timing offsets; and mean for performing, to the network device, a physical random access channel (PRACH) transmission comprising the preamble by applying a timing advance (TA) of the terminal device and the first timing offset.

[0206] In some embodiments, the criterion related to the usage of the set of preambles and the set of timing offsets is a first criterion, and the terminal device may select the first timing offset based on a second criterion.

[0207] In some embodiments, the second criterion comprises at least one of the following: selecting the first timing offset randomly; selecting the first timing offset based on a location of the terminal device; selecting the first timing offset based on the TA determined by the terminal device; or selecting the first timing offset from the set of timing offsets based on channel delay information.

[0208] In some embodiments, the second criterion is received from the network device; or the second criterion is predefined.

[0209] In some embodiments, the apparatus may further include: means for receiving, from the network device, a random access response (RAR) message comprising a second timing offset; means for determining whether the second timing offset matches with the first timing offset; means for based on determining that the second timing offset matches with the first timing offset, determining that the RAR message is destined to the terminal device; and means for based on determining that the second timing offset does not match with the first timing offset, determining that the RAR message is not destined to the terminal device.

[0210] In some embodiments, the apparatus may further include means for receiving the criterion related to the usage the set of preambles and the set of timing offsets from the network device. In some embodiments, the criterion related to the usage the set of preambles and the set of timing offsets is predefined.

[0211] In some embodiments, the apparatus may further include: mean for receiving the set of timing offsets from the network device. In some embodiments, the set of timing offsets is predefined; or the set of timing offsets is determined by the terminal device.

[0212] In some embodiments, the apparatus further comprises means for performing other steps in some embodiments of the method 1800. In some embodiments, the means comprises at least one processor and at least one memory including computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the performance of the apparatus.

[0213] In some embodiments, an apparatus capable of performing any of the method 1900 (for example, the first terminal device) may comprise means for transmitting, to a terminal device, configuration information comprising a set of preambles associated with a timing adjustment; means for receiving, from the terminal device, a request for validating whether the terminal device is allowed to use the set of preambles; and means for transmitting an indication of a validation result to the terminal device.

[0214] In some embodiments, the request comprises information indicating the network device to determine whether the timing advance (TA) determination of the terminal device is valid or not.

[0215] In some embodiments, the means for transmitting the indication may include: means for determining, based on the information, whether a TA determination of the terminal device is valid; means for based on determining that the TA determination is valid, transmitting the indication indicating that the validation result is positive; and means for based on determining that the TA determination is invalid, transmitting the indication indicating that the validation result is negative.

[0216] In some embodiments, the indication indicates that the validation result is positive, and the apparatus may further include: means for transmitting, to the terminal device, a criterion related to usage of the set of preambles and a set of timing offsets; and means for receiving, from the terminal device, a physical random access channel (PRACH) transmission comprising a preamble among the set of preambles, whereinthe PRACH transmission is adjusted based on a timing advance (TA) of the terminal device and a first timing offset.

[0217] In some embodiments, the apparatus may further include: means for detecting the first timing offset based on the received PRACH transmission; and means for transmitting, to the terminal device, a random access response (RAR) message comprising the detected first timing offset.

[0218] In some embodiments, the criterion comprises at least one of the following: a TA determination capability; or the terminal device being configured to use a stored TA.

[0219] In some embodiments, the apparatus may further include: means for transmitting a set of timing offsets to be used for a PRACH transmission comprising a preamble from the set of preambles.

[0220] In some embodiments, the criterion related to the usage of the set of preambles and the set of timing offsets is a first criterion, and the network device may further transmit to the terminal device a second criterion for selecting the first timing offset.

[0221] In some embodiments, the second criterion comprises at least one of the following: selecting the first timing offset randomly; selecting the first timing offset based on a location of the terminal device; selecting the first timing offset based on the TA determined by the terminal device; or selecting the first timing offset from the set of timing offsets based on channel delay profile estimation of the terminal device.

[0222] In some embodiments, the apparatus further comprises means for performing other steps in some embodiments of the method 1900. In some embodiments, the means comprises at least one processor and at least one memory including computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the performance of the apparatus.

[0223] FIG. 20 is a simplified block diagram of a device 2000 that is suitable for implementing embodiments of the present disclosure. The device 2000 may be provided to implement the communication device, for example the first terminal device, the second terminal device, or the network device. As shown, the device 2000 includes one or more processors 2010, one or more memories 2020 coupled to the processor 2010, and one or more communication modules 2040 coupled to the processor 2010.

[0224] The communication modules 2040 is for bidirectional communications. The communication modules 2040 has at least one antenna to facilitate communication. The communication interface may represent any interface that is necessary for communication with other network elements.

[0225] The processor 2010 may be of any type suitable to the local technical network and may include one or more of the following: general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 2000 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

[0226] The memory 2020 may include one or more non-volatile memories and one or more volatile memories. Examples of the non-volatile memories include, but are not limited to, a Read Only Memory(ROM) 2024, an electrically programmable read only memory (EPROM), a flash memory, a hard disk, a compact disc (CD), a digital video disk (DVD), and other magnetic storage and / or optical storage. Examples of the volatile memories include, but are not limited to, a random access memory (RAM) 2022 and other volatile memories that will not last in the power-down duration.

[0227] A computer program 2030 includes computer executable instructions that are executed by the associated processor 2010. The program 2030 may be stored in the ROM 2024. The processor 2010 may perform any suitable actions and processing by loading the program 2030 into the RAM 2022.

[0228] The embodiments of the present disclosure may be implemented by means of the program 830 so that the device 2000 may perform any process of the disclosure as discussed with reference to FIGS. 2 to 19. The embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

[0229] In some embodiments, the program 2030 may be tangibly contained in a computer readable medium which may be included in the device 2000 (such as in the memory 2020) or other storage devices that are accessible by the device 2000. The device 2000 may load the program 2030 from the computer readable medium to the RAM 822 for execution. The computer readable medium may include any types of tangible non-volatile storage, such as ROM, EPROM, a flash memory, a hard disk, CD, DVD, and the like. FIG. 21 shows an example of the computer readable medium 2100 in form of CD or DVD. The computer readable medium has the program 2030 stored thereon.

[0230] Generally, various embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. While various aspects of embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representations, it is to be understood that the block, apparatus, system, technique or method described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

[0231] The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer readable storage medium. The computer program product includes computerexecutable instructions, such as those included in program modules, being executed in a device on a target real or virtual processor, to carry out the method 500, 600, or 700 as described above with reference to FIGS.5-7. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various embodiments. Machine-executable instructions for program modules may be executed within alocal or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

[0232] Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program codes, when executed by the processor or controller, cause the functions / operations specified in the flowcharts and / or block diagrams to be implemented. The program code may execute entirely on a machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

[0233] In the context of the present disclosure, the computer program codes or related data may be carried by any suitable carrier to enable the device, apparatus or processor to perform various processes and operations as described above. Examples of the carrier include a signal, computer readable medium, and the like.

[0234] The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable medium may include but not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of the computer readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. The term “non-transitory,” as used herein, is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM).

[0235] Further, while operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable subcombination.

[0236] Although the present disclosure has been described in languages specific to structural features and / or methodological acts, it is to be understood that the present disclosure defined in the appended claimsis not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

WHAT IS CLAIMED IS:

1. A terminal device, comprising:at least one processor; andat least one memory storing instructions that, when executed by the at least one processor, cause the terminal device at least to:receive, from a network device, configuration information comprising multiple formats or multiple cyclic prefix (CP) durations for a physical random access channel (PRACH), wherein the multiple formats are different with each other at least in a CP duration;select, based on a predefined or a configured criterion, a format from the multiple formats or a CP duration from the multiple CP durations; andperform, to the network device, a PRACH transmission based on the selected format or the selected CP duration.

2. The terminal device of claim 1, wherein the terminal device is caused to select the format or CP duration by determining whether the predefined or configured criterion is satisfied and one of the following:based on determining that the criterion is satisfied, selecting a first format from a set of formats within the multiple formats as the selected format, or selecting a first CP duration from a set of CP durations within the multiple CP durations as the selected CP duration; orbased on determining that the criterion is not satisfied, selecting a second format from another set of formats within the multiple formats as the selected format, or selecting a second CP duration from another set of CP durations within the multiple CP durations as the selected CP duration.

3. The terminal device of claim 2, wherein at least one of the following:the set of formats comprises one or more of a lean format and a partially lean format, wherein the lean format includes a short CP duration and the partially lean format includes a medium CP duration longer than the short CP duration,at least one of the lean format and the partially lean format comprise no guard period (GP), the other set of formats comprises a normal format, wherein the normal format includes a normal CP duration longer than the medium CP duration,the set of CP durations comprises one or more of a lean CP duration and the partially lean CP duration longer than the lean CP duration, orthe other set of CP durations comprises a normal CP duration longer than the partially lean CP duration.

4. The terminal device of claim 2 or 3, wherein the set of formats comprises the lean format and the partially lean format, the criterion comprises accuracy of a TA determination of the terminal device, and the terminal device is caused to select the first format or the first CP duration by the following:based on determining that the accuracy is higher than or equal to an accuracy threshold, determining a lean format among the set of formats as the first format or a lean CP duration from the set of formats as the first CP duration; orbased on determining that the accuracy is lower than the accuracy threshold, determining a partially lean format among the set of formats as the first format or a partially lean CP duration from the set of CP durations as the first CP duration.

5. The terminal device of any of claims 1 to 4, wherein the criterion comprises at least one of the following:a TA determination capability;one or more accuracy level thresholds for a TA determination of the terminal device;the terminal device being configured to use a stored TA;one or more power thresholds for a received power at the terminal device;one or more power thresholds associated with a neighboring cell;a distance between the terminal device and a reference location; orone or more accuracy levels of propagation delay between the terminal device and the network device.

6. The terminal device of any of claims 1 to 5, wherein the terminal device is further caused to: receive the criterion from the network device.

7. The terminal device of any of claims 1 to 5, wherein the criterion is predefined.

8. The terminal device of any of claims 1 to 7, wherein the selected format is a first format of the multiple formats, or the selected CP duration is a first CP duration of the multiple CP durations, and wherein the terminal device is further caused to:determine that a number of failed random access attempts using the first format or first CP duration exceeds a failure number threshold;select a second format from the multiple formats or a second CP duration from multiple CP durations, wherein a CP duration of the second format is longer than a CP duration of the first format, or the second duration is longer than the first CP duration; andperform, to the network device, a subsequent random access procedure by transmitting a PRACH based on the normal format or the normal CP duration.

9. The terminal device of any of claims 1 to 7, wherein the selected format is a first format of the multiple formats, or the selected CP duration is a first CP duration of the multiple CP durations, and the terminal device is further caused to:receive, from the network device, an instruction to fall back to a second format or a second CP duration, wherein a CP duration of the second format is longer than a CP duration of the first format, or the second duration is longer than the first CP duration; andperform, to the network device, a subsequent random access by transmitting a PRACH based on the second format or the second CP duration.

10. A network device comprising:at least one processor; andat least one memory storing instructions that, when executed by the at least one processor, cause the network device at least to:transmit, to a terminal device, configuration information comprising multiple formats or multiple cyclic prefixes (CP) durations for a physical random access channel (PRACH), wherein the multiple formats are different with each other at least in a CP duration;transmit, to the terminal device, a predefined or configured criterion; and perform, from the terminal device, a reception of a PRACH transmission that is based on a format of the multiple formats or a CP duration of the multiple CP durations.

11. The network device of claim 10, wherein:the multiple formats comprise a set of formats for a terminal device satisfying the criterion and another set of formats for a terminal device unsatisfying the criterion; orthe multiple CP durations comprise a set of CP durations for the terminal device satisfying the criterion and another set of CP durations for the terminal device unsatisfying the criterion.

12. The network device of claim 11 , wherein at least one of the following:the set of formats comprises one or more of a lean format and a partially lean format, wherein the lean format includes a short CP duration and the partially lean format includes a medium CP duration longer than the short CP duration,at least one of the lean format and the partially lean format comprise no guard period (GP),the other set of formats comprises a normal format, wherein the normal format includes a normal CP duration longer than the medium CP duration,the set of CP durations comprises one or more of a lean CP duration and the partially lean CP duration longer than the lean CP duration, orthe other set of CP durations comprises a normal CP duration longer than the partially lean CP duration.

13. The network device of claim 11 or 12, wherein the criterion comprises at least one of the following: a timing advance (TA) determination capability;one or more accuracy level thresholds for a TA determination of the terminal device;the terminal device being configured to use a stored TA;one or more powers thresholds for a received power at the terminal device;one or more powers threshold associated with a neighboring cell;a distance between the terminal device and a reference location; orone or more accuracy levels of propagation delay between the terminal device and the network device.

14. The network device of any of claims 11 to 13, wherein the network device is caused to transmit the configuration information comprising the multiple formats or multiple CPs based on at least one of the following:a size of cell;one or more coverage enhancement levels supported by the cell; ora load status of the cell.

15. The network device of any of claims 11 to 14, wherein the network device is further caused to: estimate a percentage of PRACH attempts using at least one or more of a lean format, a partially lean format, a lean CP duration or a partially lean CP duration in a cell;determine, based on the percentage, a set of time units supporting the at least one or more of a lean format, a partially lean format, a lean CP duration or a partially lean CP duration.

16. The network device of claim 12, wherein the format for the PRACH transmission is a first format of the multiple formats, or the CP duration for the PRACH transmission is a first CP duration of the multiple CP durations, and the network device is further caused to:transmit, based on a TA detection, an instruction to fall back to a second format or a second CP duration to the terminal device, wherein a CP duration of the second format is longer than a CP duration of the first format, or the second duration is longer than the first CP duration.

17. A method comprising:receiving, by a terminal device from a network device, configuration information comprising multiple formats or multiple cyclic prefix (CP) durations for a physical random access channel (PRACH), wherein the multiple formats are different with each other at least in a CP duration;selecting, based on a predefined or a configured criterion, a format from the multiple formats or a CP duration from the multiple CP durations; andperforming, to the network device, a PRACH transmission based on the selected format or the selected CP duration.

18. A method comprising:transmitting, by a network device to a terminal device, configuration information comprising multiple formats or multiple cyclic prefixes (CP) durations for a physical random access channel (PRACH), wherein the multiple formats are different with each other at least in a CP duration; andtransmitting, to the terminal device, a predefined or configured criterion for selecting a format of a CP duration; andperforming, from the terminal device, a reception of a PRACH transmission that is based on a format of the multiple formats or a CP duration of the multiple CP durations.

19. An apparatus comprising:means for receiving, from a network device, configuration information comprising multiple formats or multiple cyclic prefix (CP) durations for a physical random access channel (PRACH), wherein the multiple formats are different with each other at least in a CP duration;means for selecting, based on a predefined or a configured criterion, a format from the multiple formats or a CP duration from the multiple CP durations; andmeans for performing, to the network device, a PRACH transmission based on the selected format or the selected CP duration.

20. An apparatus comprising:means for transmitting, to a terminal device, configuration information comprising multiple formats or multiple cyclic prefixes (CP) durations for a physical random access channel (PRACH), wherein the multiple formats are different with each other at least in a CP duration; andmeans for transmitting, to the terminal device, a predefined or configured criterion for selecting a format of a CP duration; andmeans for performing, from the terminal device, a reception of a PRACH transmission that is based on a format of the multiple formats or a CP duration of the multiple CP durations.

21. A computer readable medium comprising program instructions stored thereon for performing at least the method of claim 17 or claim 18.

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