WO2025231908A1

WO2025231908A1 - Random access backoff

Info

Publication number: WO2025231908A1
Application number: PCT/CN2024/092486
Authority: WO
Inventors: John Harris; Mads LAURIDSEN; Daniela Laselva; Chunli Wu; Ahlem KHLASS
Original assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy; Nokia Technologies Oy
Current assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy; Nokia Technologies Oy
Priority date: 2024-05-10
Filing date: 2024-05-10
Publication date: 2025-11-13
Anticipated expiration: 2026-11-10

Abstract

Example embodiments of the present disclosure are directed to random access backoff. A method includes receiving configuration information indicating a time offset to be applied when selecting a random access channel, RACH, occasion for a physical random access channel transmission. The method further includes upon triggering of the physical random access channel transmission, determining whether the time offset shall be applied based at least on said configuration information. The method further includes computing the time offset based on at least the configuration information. The method further includes selecting said RACH occasion based at least on the computed time offset.

Description

RANDOM ACCESS BACKOFF

FIELD

Various example embodiments of the present disclosure generally relate to the field of telecommunication and in particular, to methods, devices, apparatuses and computer readable storage medium for random access backoff.

BACKGROUND

In a wireless communication network, when a user equipment (UE) wishes to establish a connection or respond to a network request, it first needs to perform a random access procedure. The UE needs to select one from multiple available Random Access Channel (RACH) occasions to initiate the access process.

SUMMARY

In a first aspect of the present disclosure, there is provided a user equipment. The user equipment comprises at least one processor, and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the user equipment at least to: receive configuration information indicating a time offset to be applied when selecting a random access channel, RACH, occasion for a physical random access channel transmission; upon triggering of the physical random access channel transmission, determine whether the time offset shall be applied based at least on said configuration information; compute the time offset based on at least the configuration information; and select said RACH occasion based at least on the computed time offset.

In a second aspect of the present disclosure, there is provided a network node. The network node comprises at least one processor, and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the network node at least to: configure configuration information; and send said configuration information; wherein said configuration information includes information indicating a time offset to be applied when selecting a random access channel, RACH, occasion for a physical random access channel transmission, such that, upon triggering of the physical random access channel transmission, a user equipment can determine whether the time offset shall be applied based at least on said configuration information, and information to compute the time offset, such that said user equipment can select the RACH occasion for the physical random access transmission based at least on the computed time offset.

In a third aspect of the present disclosure, there is provided a method. The method comprises: receiving, at a user equipment, configuration information indicating a time offset to be applied when selecting one of a RACH occasion for a physical random access channel transmission; upon triggering of the physical random access channel transmission, determining whether the time offset shall be applied based at least on said configuration information; computing the time offset based on at least the configuration information; and selecting said one RACH occasion based at least on the computed time offset.

In a fourth aspect of the present disclosure, there is provided a method. The method comprises: configuring, at a network node, configuration information; and sending said configuration information, wherein said configuration information includes information indicating a time offset to be applied when selecting a RACH occasion for a physical random access channel transmission, such that, upon triggering of the physical random access channel transmission, a user equipment can determine whether the time offset shall be applied based at least on said configuration information, and information to compute the time offset, such that said user equipment can select the RACH occasion for the physical random access transmission based at least on the computed time offset.

In a fifth aspect of the present disclosure, there is provided a first apparatus. The first apparatus comprises means for receiving configuration information indicating a time offset to be applied when selecting one of a random access channel, RACH, occasion for a physical random access channel transmission; means for upon triggering of the physical random access channel transmission, determining whether the time offset shall be applied based at least on said configuration information; means for computing the time offset based on at least the configuration information; and means for selecting said one RACH occasion based at least on the computed time offset.

In a sixth aspect of the present disclosure, there is provided a second apparatus. The second apparatus comprises means for configuring configuration information; and means for sending said configuration information; wherein said configuration information includes information indicating a time offset to be applied when selecting a RACH occasion for a physical random access channel transmission, such that, upon triggering of the physical random access channel transmission, a user equipment can determine whether the time offset shall be applied based at least on said configuration information, and information to compute the time offset, such that said user equipment can select the RACH occasion for the physical random access transmission based at least on the computed time offset.

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

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

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

Some example embodiments will now be described with reference to the accompanying drawings, where:

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

FIG. 2 illustrates a schematic diagram of clustered paging in low load scenarios;

FIG. 3 illustrates an example signalling chart of selecting a RACH occasion in accordance with some example embodiments of the present disclosure;

FIG. 4 illustrates another example signalling chart of selecting a RACH occasion in accordance with some example embodiments of the present disclosure;

FIG. 5 illustrates a schematic diagram of RACH occasion loads;

FIG. 6 illustrates a flowchart of a method implemented at a user equipment in accordance with some example embodiments of the present disclosure;

FIG. 7 illustrates a flowchart of a method implemented at a network node in accordance with some example embodiments of the present disclosure;

FIG. 8 illustrates a simplified block diagram of a device that is suitable for implementing example embodiments of the present disclosure; and

FIG. 9 illustrates a block diagram of an example computer readable medium in accordance with some example embodiments of the present disclosure.

Throughout the drawings, the same or similar reference numerals represent the same or similar element.

DETAILED DESCRIPTION

Principle 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. Embodiments described herein can be implemented in various manners other than the ones described below.

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.

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.

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

As used herein, “at least one of the following: <a list of two or more elements>” and “at least one of <a list of two or more elements>” 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.

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

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.

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.

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.

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

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

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

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

FIG. 1 illustrates an example communication environment 100 in which example embodiments of the present disclosure can be implemented. In the communication environment 100, a user equipment 110 and a network node 120 can communicate with each other. In some example embodiments, the user equipment 110 may be a terminal device, and the network node 120 may be a network device (for example, a gNB) .

It is to be understood that the number of user equipment 110 and network node 120 shown in FIG. 1 is given for the purpose of illustration without suggesting any limitations. The communication environment 100 may include any suitable number of user equipment 110 and network node 120.

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

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

As mentioned above, the UE notifies the network of its intention to establish a connection by sending a preamble, thereby making the entire wireless communication network operate more efficiently. Related objectives are illustrated as Table 1.

Table 1

The paging clustering approach has been proposed. FIG. 2 illustrates a schematic diagram of clustered paging in low load scenarios. Without this paging clustering approach, UEs’ Paging Occasions (POs) are distributed in the time domain (this is by design to increase paging capacity and distribute resource usage over time) . However, such design negatively impacts the random access network (RAN) sleeping opportunities because the cell must wake up at different times for paging transmissions (according to the paging occasions) even when the paging load is low.

To reduce the number of paging transmissions in low-load scenarios, the paging of Release (Rel) 19 UEs in fewer Paging Occasions is clustered in time, which are common or contiguous for different UEs. As shown in FIG. 2, the paging occasions of different UEs are confined in the clustered paging occasion time interval. This can be achieved by adjusting the UE’s PO/Paging Frame (PF) calculations of Rel. 19 UEs. The same paging latency is ensured for Rel 19 UEs as in legacy as their Paging Occasions are only clustered together. Legacy UEs can continue using legacy paging, therefore there shall be no impact to legacy UE paging.

As used herein, the term “paging window” may refer to a time window, a time interval or a time period within which paging occasions of different UEs are confined. These paging occasions may be considered as clustered in the paging window. In present disclosure, such a paging window may be also referred to as a clustered paging occasion time interval.

Regarding adaptation of common signal/channel transmissions, adaptation of paging occasions includes confining the paging occasions in the time domain. Note that there shall be no impact to legacy UEs nor paging latency increase. Therefore, paging occasion adaptation solution is expected in Release 19.

The following in Table 2 has been agreed.

Table 2

Currently, if the UE sends a PRACH preamble but either it does not receive a Random Access Response (RAR) or receives a RAR including a Random Access Preamble Identifier (RAPID) that is not for the UE, the UE is allowed to make a subsequent PRACH transmission after a certain time delay (i.e. a backoff time) . This time delay is controlled by two parameters received from the network (i.e. PREAMBLE_BACKOFF and SCALING_FACTOR_BI, which is ‘ascaling factor for prioritized Random Access procedure’ ) as defined in TS38.321. The texts in Table 3 and Table 4 excerpt from TS38.321.

Table 3

Table 4

In the context of earlier Machine-Type Communication (MTC) work, a PRACH backoff indicator is currently defined. The Backoff Indicator is a special MAC sub-header that carries the parameter indicating the time delay between a PRACH and the next PRACH. The backoff indicator is transmitted as a Medium Access Control (MAC) sub-header during the RAR window i.e. after UE transmitted the PRACH preamble.

There are cases where a UE must send another PRACH after it already sent a PRACH such as: (i) UE sent a PRACH but didn’ t get a RAR for some reason; (ii) UE sent a PRACH and got RAR, but the RAPID in the RAR is not for the UE.

However, earlier MTC work does not describe explicit paging control of the backoff after paging occasion prior to RACH.

Continue with reference to FIG. 2, the Random Access (RA) /PRACH load level will inherently increase during/after each “clustered” NW paging window, in which the paging occasions are grouped closely in time. This is because the UEs will have to be paged during the same paging window or clustered paging occasion time interval, thereby causing the UEs to respond to the paging by transmitting a PRACH preamble in a clustered time interval. Note that the UE responds to paging by initiating the Random Access procedure either for Radio Resource Control (RRC) Connection setup, resume, or Small Data Transmission (SDT) .

It is noted that currently there are limitations on the maximum number of ROs which can be configured during each RO cycle/period. Also, providing a large amount of ROs or more frequent ROs reduces the number of resources available for data transmissions because the PUSCH resources reserved for RO cannot be used for other purposes.

Based on the discussion above, the issue to be addressed is how to handle the RA load when clustered paging is used for network energy saving.

To this end, embodiments of the present disclosure propose solutions for random access backoff. According to the embodiments of the present disclosure, user equipment receives configuration information indicating a time offset to be applied when selecting a RACH occasion for a physical random access channel transmission. upon triggering of the physical random access channel transmission, the user equipment determines whether the time offset shall be applied based at least on said configuration information. Further, the user equipment computes the time offset based on at least the configuration information and selects said RACH occasion based at least on the computed time offset.

In this way, PO clustering may be enabled for NW Energy Savings while appropriately managing preamble transmissions/RA attempts relative to resources and the clustered POs.

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

Reference is now made to FIG. 3, which illustrates a signalling chart 300 of selecting RACH occasion in accordance with some example embodiments of the present disclosure. As shown in FIG. 3, the signalling chart 300 involves the user equipment 110 and the network node 120. For the purpose of discussion, reference is made to FIG. 1 to describe the signaling chart 300. In some example embodiments, the user equipment 110 may be or be comprised in a terminal device, and the network node 120 may be or be comprised in a network device.

As shown in FIG. 3, in some example embodiments, the network node 120 configures 302 configuration information. The configuration information includes information indicating a time offset to be applied when selecting a RACH occasion for a physical random access channel transmission.

The user equipment 110 (or UE group) may apply the time offset (also referred to as First PRACH Offset (FRO) ) when selecting a RACH Occasion for an initial PRACH preamble transmission.

In some example embodiments, the configuration information may be received from a cell of a network. In some example embodiments, the physical random access channel transmission may be to the cell.

The network node 120 sends 304 the configuration information to the user equipment 110. The user equipment 110 receives the configuration information.

After receiving the configuration information, the user equipment 110 may determine whether the physical random access channel transmission is triggered. If the physical random access channel transmission is triggered, the user equipment 110 determines 306 whether the time offset shall be applied based at least on said configuration information.

The user equipment 110 computes 308 the time offset based on at least the configuration information. For example, the time offset may be determined based on information received from the network, including at least dynamic information that depends on the actual PRACH load (e.g. number of paged UEs, number of POs in a window) .

In some example embodiments, the configuration information may be indicated in a combination of one or more of a System Information Block (SIB) , a Paging Early Indication (PEI) , in a paging Downlink Control Information (DCI) , in a short message, in a paging message, in RRC signalling. For example, the user equipment 110 may compute the time offset based on information associated with the paging, such as information received in any of PEI, paging DCI, or paging record, or optionally in SIB.

In some example embodiments, the user equipment 110 may determine whether to apply the time offset based on a trigger of the first PRACH transmission. For example, whether to apply the time offset may depend on whether the first PRACH transmission is triggered by paging by the network node 120 or having UL data to transmit.

In some example embodiments, the user equipment 110 may determine whether to apply the time offset based on whether the user equipment 110 is paged by the network node 120. The user equipment 110 may determine to apply the time offset if the triggering of the physical random access channel transmission is to respond to the paging. That is, the time offset may be applicable to the case where RACH is triggered due to paging, i.e. the Random Access is triggered in response to the fact that the UE was paged.

In some example embodiments, the user equipment 110 may determine whether to apply the time offset based on whether the user equipment 110 have uplink data in the buffer. The user equipment 110 may not determine to apply the time offset if the triggering of the physical random access channel transmission is due to the UL data. For example, if the PRACH transmission is triggered by UL data, the user equipment 110 may not apply the time offset and just select the RACH occasion based on legacy behavior (e.g., the UE typically picks the first available RACH occasion) . When the user equipment 110 is in RRC Idle/Inactive state, any type of UL data (for example, user plane data or control plane data) may trigger the user equipment 110 to perform PRACH transmission. The PRACH transmission may be performed as Small Data Transmission or Initial Access /Connection Resume etc.

In some example embodiments, if the first PRACH transmission is triggered by both paging by the network node 120 and having UL data in the buffer, the user equipment 110 may determine to apply the time offset.

In some example embodiments, the determining whether to apply the time offset depends on the user equipment 110 being indicated by the network node 120 to apply the time offset. Then, the user equipment 110 may determine to apply the time offset if the user equipment 110 is indicated by the network node 120 to apply the time offset. For example, if the network node 120 explicitly indicates to the user equipment 110 to apply the time offset or if the network node 120 configures a value of the time offset to the user equipment 110, the user equipment 110 may determine to apply the time offset.

In some example embodiments, the determining whether to apply the time offset may depend on whether additional physical random access channel resources are configured for the user equipment 110. For example, the additional physical random access channel resources may be different from physical random access channel resources used for legacy UEs or for UEs without capability of applying a time offset in RO selection. In some example embodiments, the additional physical random access channel resources may comprise physical random access channel resources additional to the resources that are provide in system information for any RRC Idle/Inactive UE.

In some example embodiments, whether or not the additional physical random access channel resources are configured for the user equipment 110 may be indicated in the received configuration information.

The user equipment 110 selects 310 said the RACH occasion based at least on the computed time offset. Note that based on legacy behavior, the selection of the RO to be used for initial PRACH preamble transmission is up to the UE implementation, and typically, the UE selects the first available RO (based on the NW configuration) . By applying the proposed time offset, FRO, this allows the NW to use a controlled spreading of the RACH load in time, when needed (if the PRACH load is expected to be high in a certain period) to reduce the number of PRACH collisions and to optimize the resource utilization.

In some example embodiments, the time offset may be relative to at least one of: a start of a paging offset of the user equipment, a start of a paging window within which paging occasions for different user equipment are confined, a start of a plurality of paging occasions confined in a time window, a start of a paging window used for network energy saving (e.g., a cluster of paging occasions of NW energy savings paging window) , a start of a paging frame, reception of a paging message or record, reception of paging early indication, or reception of a wake-up signal.

In some example embodiments, the time offset is based on at least one of: if paging occasion adaptation is used, the number of paging occasions adapted to fit within a paging window, the length of the paging window, the number of UEs being paged in the paging message or record, where the user equipment is paged, or a relative position of a paging occasion, of the user equipment, in the paging window. For example, the time offset may be relative to one of a start of a UE’s PO, PF, Paging Window.

In some example embodiments, the time offset may define a minimum time offset. Alternatively, or in addition, the time offset may define a maximum time offset that the user equipment 110 (or UE group) has to apply when selecting a RACH Occasion that the user equipment 110 (or UE group) is allowed to use. As an option, the user equipment 110 may be allowed to select a valid RO located in time only after the minimum time offset has expired. As another option, the user equipment 110 may be allowed to select a valid RO falling before the maximum time offset. As a further option, the user equipment 110 may be allowed to select a valid RO after the minimum time offset and before the maximum time offset.

In some example embodiments, the user equipment 110 may use the time offset only if configured/indicated by the network. In one example, the NW may indicate that the use of the time offset depends on the number of UEs paged in the same paging record. For example, the application of the time offset results in a backoff that is only applied if the number of UEs being paged is above a certain network-configured threshold, which may result in a higher PRACH collision probability, and where the backoff reduces such probability of PRACH collision.

In some example embodiments, the time offset may be configured to be applied to legacy RO and/or additional ROs (e.g., available to R19 UEs) .

In summary, the UE may receive the configuration information related to the time offset to apply for the selection of RO for a first PRACH transmission. If a PRACH transmission is triggered, the UE may determine whether it shall apply the time offset at least based on the configuration information. If so, the UE may compute the time offset at least based on the configuration information, and select the RO for the first PRACH transmission according to the computed time offset. The following will provide another example embodiment of selecting RACH occasion to initiate a PRACH transmission.

FIG. 4 illustrates a signalling chart 400 of selecting RACH occasion in accordance with some example embodiments of the present disclosure. As shown in FIG. 4, the signalling chart 400 involves the user equipment 110 and the network node 120. For the purpose of discussion, reference is made to FIG. 1 to describe the signaling chart 400. The signalling chart 400 may be considered as an example of the signalling chart 300.

As shown in FIG. 4, the user equipment 110 may be 402 in a state of RRC idle/inactive/connected. The network node 120 may send 404 system information to the user equipment 110. The system information may include a PRACH configuration. Alternatively, the system information may further include information related to a FRO. For example, the NW may configure a PRACH configuration in the system information, which may include optional parameters enabling computing the FRO.

The network node 120 may send 406 paging information to the user equipment 110. The paging information may include information related to the FRO. For example, the NW pages the user equipment 110 and provide information to compute the FRO.

The user equipment 110 may receive the system information and the paging information. Such information may include a paging indication and information related to the FRO.

The user equipment 110 may trigger 408 a RACH procedure. The user equipment 110 may determine 410 whether to apply the FRO based on the NW indication. If the NW indicates that the FRO should be applied, the user equipment 110 may use the received information to compute 412 the FRO.

The user equipment 110 may select 414 an RO for an initial PRACH preamble transmission based on the computed FRO. Then the user equipment 110 may apply the FRO to perform 416 a PRACH transmission. The RACH procedure may continue 418 as in legacy.

In the following, examples of how the FRO may be defined are provided. Note that the parameters in the equations below may be provided to the user equipment 110 in any combination of the Paging Record, PEI, the short message of the Paging DCI, SIB, or depend on certain paging information.

As an option, the time offset FRO may be computed as:

FRO = {FRO_Scaling_Factor *N *P} [Nr. of symbols or slots /Nr. of ROs which should elapse /ms] . Eq. (1)

In Eq. (1) , FRO_Scaling_Factor represents (optional) scaling factor that allows the network to better control the absolute FRO value. This may be cell-specific or UE-specific. It may be provided in paging information or in SIB (in this case it can only be cell-specific or UE group-specific) .

In one example, it may be set up to 1. Typically, it may be below 1 and be needed because otherwise the FRO may become too large.

For example, the FRO corresponding to the 3^rd PO in the PO cluster needs to be larger than the FRO corresponding to the 1^st PO, but a value less than 3 (e.g., slots) will likely be sufficient. Note that the FRO may be non-integer.

In Eq. (1) , N represents Total number of UEs in the Paging Record where the UE was paged. FRO may become larger with larger N (i.e., the larger number of UEs in the paging record the more the NW may spread the UE responses to the paging) .

In an example, N may be scaled by the maximum number of UEs in a paging record ( ‘maxNrofPageRec’ = 32 in TS 38.331) as “N divided by maxNrofPageRec” .

In Eq. (1) , P represents (integer) UE’s PO’s Position within the PO Cluster where the UE was paged. For example, if UE’s PO is 2nd PO in the PO cluster, then P=2. If the UE’s PO is the Nth PO in the PO cluster, then P=N.

There may be multiple PO’s within the PO cluster. In general, the amount of accumulated PRACH load ‘pending’ (i.e. not yet served RACH transmissions) is expected to increase later within the PO cluster. For example, the pending but not yet served RACH load is larger after the 3rd and 4th PO in the PO cluster, where the pending but not yet served RACH load is relatively small after the 1st or 2nd PO in the PO cluster. As a result, the FRO used by the UE is larger if the UE’s PO occurs later within the PO cluster, i.e. after which more RA load has more likely “accumulated” .

Note that the NW may choose to configure either N, P or both.

As another option, the time offset FRO may be computed as:

FRO = {FRO_Scaling_Factor *N *P *S + T} [Nr. of symbols or slots /Nr. of ROs which should elapse /ms] . Eq. (2)

The parameters such as FRO_Scaling_Factor, N and P may refer to the description above, which is not repeated here.

In Eq. (2) , S represents Per UE factor, which depend on the position of the UE ID within the Paging record. T represents Additive offset to control the absolute time offset.

In some example embodiments, if the UE ID is within the first X IDs (e.g. X =10) of the paging record, the UE may scale the FRO with k₁ (e.g. k₁ =1) , while if the UE’s ID is not part of the first X IDs it may scale FRO with k₂ (e.g. k₁ =2) .

FIG. 5 illustrates a schematic diagram of RACH occasion load. The plot 502 shows high level trends in RO loads without including details like exact RO timing. The plot 502 shows cumulative offered load for RACH occasions and the dashed line in the plot 502 shows backlogs not yet satisfied. A dashed line 506 represents a FRO computed by a UE based on the time of paging (PO location) of the UE.

FIG. 6 shows a flowchart of an example method 600 implemented at a user equipment in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 600 will be described from the perspective of the user equipment 110 in FIG. 1.

At block 610, the user equipment 110 receives configuration information indicating a time offset to be applied when selecting a random access channel, RACH, occasion for a physical random access channel transmission.

At block 620, upon triggering of the physical random access channel transmission, the user equipment 110 determines whether the time offset shall be applied based at least on said configuration information.

At block 630, the user equipment 110 computes the time offset based on at least the configuration information.

At block 640, the user equipment 110 selects said RACH occasion based at least on the computed time offset.

In some example embodiments, the configuration information is received from a cell of a network.

In some example embodiments, the physical random access channel transmission is to said cell.

In some example embodiments, the configuration information is indicated in a combination of one or more of a System Information Block, a Paging Early Indication, in a paging downlink control information, in a short message, in a paging message, in radio resource control signalling.

In some example embodiments, the determining whether to apply the time offset depends upon the user equipment 110 being paged by a network node, and the user equipment 110 determines to apply the time offset if the triggering of the physical random access channel transmission is to respond to the paging.

In some example embodiments, the determining whether to apply the time offset depends on the user equipment 110 having uplink data in the buffer, and the user equipment 110 determines not to apply the time offset if the triggering of the physical random access channel transmission is due to the uplink data or not due to paging.

In some example embodiments, the determining whether to apply the time offset depends on the user equipment being indicated by a network node to apply the time offset, and the user equipment determines to apply the time offset if the user equipment is indicated by the network node to apply the time offset.

In some example embodiments, the determining whether to apply the time offset depends on whether additional physical random access channel resources are configured for the user equipment 110.

In some example embodiments, the additional physical random access channel resources comprise physical random access channel resources other than physical random access channel resources indicated in system information.

In some example embodiments, whether or not the additional physical random access channel resources are configured for the user equipment 110 is indicated in the received configuration information.

In some example embodiments, the time offset is relative to at least one of: a start of a paging offset of the user equipment 110, a start of a paging window within which paging occasions for different user equipment are confined, a start of a plurality of paging occasions confined in a time window, a start of a paging window used for network energy saving, a start of a paging frame, reception of a paging message or record, reception of paging early indication, or reception of a wake-up signal.

In some example embodiments, the time offset is based on at least one of: if paging occasion adaptation is used, the number of paging occasions adapted to fit within a paging window, the length of the paging window, the number of UEs being paged in the paging message or record, where the user equipment is paged, or a relative position of a paging occasion, of the user equipment, in the paging window.

FIG. 7 shows a flowchart of an example method 700 implemented at a network node in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 700 will be described from the perspective of the network node 120 in FIG. 1.

At block 710, the network node 120 configures configuration information. and

At block 720, the network node 120 sends said configuration information. Said configuration information includes information indicating a time offset to be applied when selecting a random access channel, RACH, occasion for a physical random access channel transmission, such that, upon triggering of the physical random access channel transmission, a user equipment can determine whether the time offset shall be applied based at least on said configuration information, and information to compute the time offset, such that said user equipment can select the RACH occasion for the physical random access transmission based at least on the computed time offset.

In some example embodiments, the network node 120 pages the user equipment to send the configuration information.

In some example embodiments, a user equipment capable of performing any of the method 600 (for example, the user equipment 110 in FIG. 1) may comprise means for performing the respective operations of the method 600. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The user equipment may be implemented as or included in the user equipment 110 in FIG. 1.

In some example embodiments, the user equipment comprises means for receiving configuration information indicating a time offset to be applied when selecting a RACH occasion for a physical random access channel transmission; means for upon triggering of the physical random access channel transmission, determining whether the time offset shall be applied based at least on said configuration information; means for computing the time offset based on at least the configuration information; and means for selecting said one RACH occasion based at least on the computed time offset.

In some example embodiments, the determining whether to apply the time offset depends upon the user equipment being paged by a network node, and the user equipment determines to apply the time offset if the triggering of the physical random access channel transmission is to respond to the paging.

In some example embodiments, the determining whether to apply the time offset depends on the user equipment having uplink data in the buffer, and the user equipment determines not to apply the time offset if the triggering of the physical random access channel transmission is due to the uplink data.

In some example embodiments, the determining whether to apply the time offset depends on whether additional physical random access channel resources are configured for the user equipment.

In some example embodiments, whether or not the additional physical random access channel resources are configured for the user equipment is indicated in the received configuration information.

In some example embodiments, a network node capable of performing any of the method 700 (for example, the network node 120 in FIG. 1) may comprise means for performing the respective operations of the method 700. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The network node may be implemented as or included in the network node 120 in FIG. 1.

In some example embodiments, the network node comprises means for configuring configuration information; and means for sending said configuration information; wherein said configuration information includes information indicating a time offset to be applied when selecting a RACH occasion for a physical random access channel transmission, such that, upon triggering of the physical random access channel transmission, a user equipment can determine whether the time offset shall be applied based at least on said configuration information, and information to compute the time offset, such that said user equipment can select the RACH occasion for the physical random access transmission based at least on the computed time offset.

In some example embodiments, the network node pages the user equipment to send the configuration information.

FIG. 8 is a simplified block diagram of a device 800 that is suitable for implementing example embodiments of the present disclosure. The device 800 may be provided to implement a communication device, for example, the user equipment 110 or the network node 120 as shown in FIG. 1. As shown, the device 800 includes one or more processors 810, one or more memories 820 coupled to the processor 810, and one or more communication modules 840 coupled to the processor 810.

The communication module 840 is for bidirectional communications. The communication module 840 has one or more communication interfaces to facilitate communication with one or more other modules or devices. The communication interfaces may represent any interface that is necessary for communication with other network elements. In some example embodiments, the communication module 840 may include at least one antenna.

The processor 810 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 800 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.

The memory 820 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) 824, an electrically programmable read only memory (EPROM) , a flash memory, a hard disk, a compact disc (CD) , a digital video disk (DVD) , an optical disk, a laser disk, and other magnetic storage and/or optical storage. Examples of the volatile memories include, but are not limited to, a random-access memory (RAM) 822 and other volatile memories that will not last in the power-down duration.

A computer program 830 includes computer executable instructions that are executed by the associated processor 810. The instructions of the program 830 may include instructions for performing operations/acts of some example embodiments of the present disclosure. The program 830 may be stored in the memory, e.g., the ROM 824. The processor 810 may perform any suitable actions and processing by loading the program 830 into the RAM 822.

The example embodiments of the present disclosure may be implemented by means of the program 830 so that the device 800 may perform any process of the disclosure as discussed with reference to FIG. 3 to FIG. 4. The example embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

In some example embodiments, the program 830 may be tangibly contained in a computer readable medium which may be included in the device 800 (such as in the memory 820) or other storage devices that are accessible by the device 800. The device 800 may load the program 830 from the computer readable medium to the RAM 822 for execution. In some example embodiments, the computer readable medium may include any types of non-transitory storage medium, such as ROM, EPROM, a flash memory, a hard disk, CD, DVD, and the like. The term “non-transitory, ” as used herein, is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM) .

FIG. 9 shows an example of the computer readable medium 900 which may be in form of CD, DVD or other optical storage disk. The computer readable medium 900 has the program 830 stored thereon.

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

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

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

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

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.

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

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

Claims

A user equipment, comprising:

at least one processor, and

at least one memory including computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the user equipment at least to:

receive configuration information indicating a time offset to be applied when selecting a random access channel, RACH, occasion for a physical random access channel transmission;

upon triggering of the physical random access channel transmission, determine whether the time offset shall be applied based at least on said configuration information;

compute the time offset based on at least the configuration information; and

select said RACH occasion based at least on the computed time offset.
The user equipment according to claim 1, wherein the configuration information is received from a cell of a network.
The user equipment according to claim 2, wherein the physical random access channel transmission is to said cell.
The user equipment according to any of claims 1 to 3, wherein the configuration information is indicated in a combination of one or more of a System Information Block, a Paging Early Indication, in a paging downlink control information, in a short message, in a paging message, in radio resource control signalling.
The user equipment according to any of claims 1 to 4, wherein the determining whether to apply the time offset depends upon the user equipment being paged by a network node, and the user equipment determines to apply the time offset if the triggering of the physical random access channel transmission is to respond to the paging.
The user equipment according to any of claims 1 to 4, wherein the determining whether to apply the time offset depends on the user equipment having uplink data in the buffer, and the user equipment determines not to apply the time offset if the triggering of the physical random access channel transmission is due to the uplink data.
The user equipment according to any of claims 1 to 4, wherein the determining whether to apply the time offset depends on the user equipment being indicated by a network node to apply the time offset, and the user equipment determines to apply the time offset if the user equipment is indicated by the network node to apply the time offset.
The user equipment according to any of claims 1 to 5, wherein the determining whether to apply the time offset depends on whether additional physical random access channel resources are configured for the user equipment.
The user equipment according to claim 8, wherein the additional physical random access channel resources comprise physical random access channel resources other than physical random access channel resources indicated in system information.
The user equipment according to claim 8, wherein whether or not the additional physical random access channel resources are configured for the user equipment is indicated in the received configuration information.
The user equipment according to any of claims 1 to 10, wherein the time offset is relative to at least one of:

a start of a paging offset of the user equipment,

a start of a paging window within which paging occasions for different user equipment are confined,

a start of a plurality of paging occasions confined in a time window,

a start of a paging window used for network energy saving,

a start of a paging frame,

reception of a paging message or record,

reception of paging early indication, or

reception of a wake-up signal.
The user equipment according to any of claims 1 to 10, wherein the time offset is based on at least one of:

if paging occasion adaptation is used,

the number of paging occasions adapted to fit within a paging window,

the length of the paging window,

the number of UEs being paged in the paging message or record, where the user equipment is paged, or

a relative position of a paging occasion, of the user equipment, in the paging window.
A network node, comprising:

at least one processor, and

at least one memory including computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the network node at least to:

configure configuration information; and

send said configuration information;

wherein said configuration information includes information indicating a time offset to be applied when selecting a random access channel, RACH, occasion for a physical random access channel transmission, such that, upon triggering of the physical random access channel transmission, a user equipment can determine whether the time offset shall be applied based at least on said configuration information, and information to compute the time offset, such that said user equipment can select the RACH occasion for the physical random access transmission based at least on the computed time offset.
The network node according to claim 11, wherein the network node pages the user equipment to send the configuration information.
A method comprising:

receiving, at a user equipment, configuration information indicating a time offset to be applied when selecting one of a RACH occasion for a physical random access channel transmission;

upon triggering of the physical random access channel transmission, determining whether the time offset shall be applied based at least on said configuration information;

computing the time offset based on at least the configuration information; and

selecting said one RACH occasion based at least on the computed time offset.
A method comprising:

configuring, at a network node, configuration information; and

sending said configuration information,

wherein said configuration information includes information indicating a time offset to be applied when selecting a RACH occasion for a physical random access channel transmission, such that, upon triggering of the physical random access channel transmission, a user equipment can determine whether the time offset shall be applied based at least on said configuration information, and information to compute the time offset, such that said user equipment can select the RACH occasion for the physical random access transmission based at least on the computed time offset.
A first apparatus comprising:

means for receiving configuration information indicating a time offset to be applied when selecting one of a random access channel, RACH, occasion for a physical random access channel transmission;

means for upon triggering of the physical random access channel transmission, determining whether the time offset shall be applied based at least on said configuration information;

means for computing the time offset based on at least the configuration information; and

means for selecting said one RACH occasion based at least on the computed time offset.
A second apparatus comprising:

means for configuring configuration information; and

means for sending said configuration information;

wherein said configuration information includes information indicating a time offset to be applied when selecting a RACH occasion for a physical random access channel transmission, such that, upon triggering of the physical random access channel transmission, a user equipment can determine whether the time offset shall be applied based at least on said configuration information, and information to compute the time offset, such that said user equipment can select the RACH occasion for the physical random access transmission based at least on the computed time offset.
A computer readable medium comprising instructions stored thereon for causing an apparatus at least to perform a method of claim 15 or a method of claim 16.