Random access channel optimization for group handover

Abstract

Example embodiments of the present invention provide at least one method and apparatus to: determine, by a network node of a target cell receiving a handover request, that at least one set of user equipments are present within the handover request; determining a unique dedicated random access channel preamble to assign to each user equipment of the at least one set of user equipment, wherein each dedicated random access channel preamble is used to initiate a random access channel procedure for a handover request of the plurality of handover requests; and providing information to the user equipment, the information comprising the dedicated random access channel preamble and a handover command for a handover of the handover request, and further for receiving, by the user equipment, information about a handover command to a target cell from a source cell of the communication network device, the information comprises an assigned dedicated random access channel preamble for initiating a random access channel procedure for handover and an indication of group handover; and performing a handover based on the information on the handover command.

Description

Technical field:

[0001] Teachings according to exemplary embodiments of the present invention generally relate to a framework to reduce random access channel procedure load, and more particularly to a framework to reduce random access channel procedure load during group handover. Background technology:

[0002] This section is intended to provide background or context for the invention recited in the claims. The description herein may include concepts that could be pursued, but not necessarily concepts that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, the material described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by virtue of its inclusion in this section.

[0003] Certain abbreviations that may be found in the specification and / or drawings are defined herein as follows: HO: Handover IE: Information Element PDCCH: Physical Downlink Control Channel RACH: Random Access Channel RAR: Random Access Response RA-RNTI: Random Access RNTI RNTI: Radio Network Temporary Identifier TA: Time ahead UE: User Equipment

[0004] There are scenarios where many communication devices suddenly need to switch from the same source cell to the same target cell at the same time, such as high-speed trains or drone swarms.

[0005] In these scenarios, there is a group of UEs that follow the same mobility pattern, which is sometimes predetermined based on train routes or, for drones, flight patterns. In the case of a swarm of drones, the network may even have information about the flight patterns.

[0006] Even if the group of UEs has the same mobility pattern, each UE operates individually during the handover (HO) procedure, and the network also handles each of these UEs individually.

[0007] Group mobility scenarios are also envisaged with new use cases, such as platooning, i.e. a method for driving a group of vehicles together to reduce the distance between cars or trucks.

[0008] Furthermore, during the handover process, a large amount of control plane load is generated in preparing resources for the handover, thereby ensuring the execution of the handover, and releasing the resources after the handover is completed.

[0009] These scenarios where a group of UEs perform handovers closely or simultaneously may result in high RACH load in the target cell.

[0010] Example embodiments of the present invention are directed to improving at least these types of operations to at least reduce RACH capacity, computational requirements, and interference caused by such handovers. Summary of the invention:

[0011] This section contains examples of possible implementations and is not intended to be limiting.

[0012] In an exemplary aspect of the present invention, there is provided an apparatus, such as a network-side apparatus, comprising: at least one processor; and at least one non-transitory memory storing instructions that, when executed by the at least one processor, cause the apparatus to at least: determine, by a network node of a target cell receiving a handover request, that at least one group of user equipment exists within the handover request; determine a unique dedicated random access channel preamble to assign to each user equipment in the at least one group of user equipment, wherein each dedicated random access channel preamble is used to initiate a random access channel procedure for a handover request in a plurality of handover requests; and provide information to the user equipment, the information comprising the dedicated random access channel preamble and a handover command for the handover of the handover request.

[0013] In another example aspect of the present invention, there is a method comprising: determining, by a network node of a target cell receiving a handover request, that at least one group of user equipment exists within the handover request; determining a unique dedicated random access channel preamble to assign to each user equipment in the at least one group of user equipment, wherein each dedicated random access channel preamble is used to initiate a random access channel procedure for a handover request in a plurality of handover requests; and providing information to the user equipment, the information comprising the dedicated random access channel preamble and a handover command for the handover of the handover request.

[0014] Another example embodiment is an apparatus and a method comprising the apparatus and method of the preceding paragraphs. wherein the determination of at least one group of user equipment within the handover request is based on an indication from a source cell, wherein the determination of at least one group of user equipment at the target cell or at the source cell of at least one group of user equipment within the handover request is based on the start of a predefined observation period, the start of the predefined observation period being confirmed based on the receipt of the handover request, wherein upon expiration of the predefined observation period, a group of user equipment for the handover request is identified, wherein the determination is based on the identification of at least one group of user equipment for the handover request upon expiration of the predefined observation period, wherein the information includes an indication that the user equipment is part of a group handover; wherein the user equipment grouping is determined based on at least one of the following: historical information of the user equipment from a user equipment information element or historical information of the user equipment provided by the source cell via the Xn interface during reception of the handover request, correlation of the last visited cell information, information of the received handover request, a serving beam in the source cell, a target beam in the target cell, or user equipment trajectory information, wherein the information includes a configuration for the user equipment to determine the probability of transmission per random access channel opportunity period, wherein there is a configuration for the user equipment to determine the probability of transmission per random access channel opportunity period, wherein there is a configuration for the user equipment to determine the probability of transmission per random access channel opportunity period, wherein there is a configuration for the user equipment to determine the probability of transmission per random access channel opportunity period, wherein there is a configuration for the user equipment to determine the probability of transmission per random access channel opportunity period, wherein there is a configuration for the user equipment to determine the probability of transmission per random access channel opportunity period, wherein there is a configuration for the user equipment to determine the probability of transmission per random access channel opportunity period, wherein A network node sends an indication to a user equipment via a source cell that the user equipment is to perform a handover and obtain a random access channel preamble transmission scheme for different random access channel opportunities, wherein the random access channel preamble transmission scheme is based on a threshold parameter and a factor parameter configured for the user equipment, wherein a random number is drawn from a uniform distribution between 0 and 1; and at least one of the following: based on the random number being greater than the threshold, using the assigned dedicated random access channel preamble identifier for transmission on the random access channel, or based on one of the random number being less than the threshold or the random access response message not being received, updating the threshold to threshold=threshold*factor, wherein when the factor is greater than 1, the probability of the user equipment transmitting the random access channel increases at each random access channel opportunity, wherein based on the user equipment in at least one group of user equipment being inactive in the target cell, actively retransmitting the random access response message performed for the handover, wherein the information is provided to the user equipment via the source cell, and / or wherein based on the initiation of the predefined observation period not being confirmed, starting the predefined observation period.

[0015] A non-transitory computer-readable medium stores program code, the program code being executed by at least one processor to perform at least the method as described in the above paragraphs.

[0016] In another example aspect of the present invention, there is an apparatus comprising: a component for determining, by a network node of a target cell receiving a handover request, that at least one group of user equipment exists within the handover request; a component for determining a unique dedicated random access channel preamble to assign to each user equipment in the at least one group of user equipment, wherein each dedicated random access channel preamble is used to initiate a random access channel procedure for a handover request in a plurality of handover requests; and a component for providing information to the user equipment, the information comprising the dedicated random access channel preamble and a handover command for the handover of the handover request.

[0017] According to the example embodiments described in the above paragraphs, at least the means for determining and providing include a network interface, and computer program code stored on a non-transitory computer readable medium and executed by at least one processor.

[0018] In another example aspect of the present invention, there is an apparatus, such as a user equipment side apparatus, comprising: at least one processor; and at least one non-volatile memory, the at least one non-volatile memory storing instructions that, when executed by the at least one processor, cause the apparatus to at least: receive, by the user equipment, information about a handover command to a target cell from a source cell of a communication network device, the information including an assigned dedicated random access channel preamble code and an indication of a group handover for initiating a random access channel process for the handover; and perform handover based on the information about the handover command.

[0019] In another exemplary aspect of the present invention, there is a method comprising: receiving, by a user equipment, information about a handover command to a target cell from a source cell of a communication network device, the information including an assigned dedicated random access channel preamble code and an indication of a group handover for initiating a random access channel procedure for the handover; and performing the handover based on the information about the handover command.

[0020] Another example embodiment is an apparatus and a method, comprising the apparatus and method of the preceding paragraphs. In response to receiving an indication, the random access channel process initiates monitoring in a random access response window before transmitting a first random access channel preamble, wherein one of: sending a dedicated preamble identifier toward a target cell or determining whether to send a dedicated preamble identifier toward the target cell based on a random access response message having a random access radio network temporary identifier, the random access radio network temporary identifier corresponding to the assigned dedicated random access channel preamble; and determining synchronization with the target cell for successfully completing a handover, wherein the information includes a configuration for a user equipment to determine a probability of transmitting a dedicated preamble per random access channel opportunity period; and wherein the user equipment receives, by the user equipment, a signal that the user equipment is to perform a handover and obtains a signal for the target cell. An indication of a random access channel preamble transmission scheme for different random access channel opportunities, wherein the random access channel preamble transmission scheme is based on a threshold parameter and a factor parameter configured for a user equipment, wherein a random number is drawn from a uniform distribution between 0 and 1; and at least one of the following: based on the random number being greater than the threshold, using the assigned dedicated random access channel preamble identifier to transmit on the random access channel, or based on one of the random number being less than the threshold or the random access response message not being received, updating the threshold to threshold = threshold * factor, and / or wherein when factor is greater than 1, the probability of the user equipment transmitting the random access channel increases at each random access channel opportunity.

[0021] A non-transitory computer-readable medium stores program code, the program code being executed by at least one processor to perform at least the method as described in the above paragraphs.

[0022] In another example aspect of the present invention, there is an apparatus comprising: a component for receiving, by a user equipment, information about a handover command to a target cell from a source cell of a communication network device, the information including an assigned dedicated random access channel preamble code and an indication of a group handover for initiating a random access channel procedure for the handover; and a component for performing the handover based on the information about the handover command.

[0023] According to the example embodiments described in the above paragraphs, at least the means for receiving and executing include a network interface, and computer program code stored on a non-transitory computer-readable medium and executed by at least one processor.

[0024] A communication system includes a network-side device and a user equipment-side device for performing the above-mentioned operations. Description of the drawings:

[0025] The above and other aspects, features and benefits of various embodiments of the present disclosure will become more fully apparent from the following detailed description with reference to the accompanying drawings, in which like reference numerals are used to designate the same or equivalent elements. The accompanying drawings are shown to facilitate a better understanding of the embodiments of the present disclosure and are not necessarily drawn to scale, wherein:

[0026] Figure 1A shows the source cell handover preparation stage;

[0027] Figure 1B shows the source cell handover execution phase;

[0028] Figure 2 A user equipment flow diagram for group-based handover is shown;

[0029] Figure 3 The comparison between the existing technology and the proposed solution for ra-ResponseWindow is shown;

[0030] Figure 4 An example of a user equipment random access channel transmission scheme is shown;

[0031] Figure 5 shows high-level block diagrams of various devices used to implement various aspects of the present invention; and

[0032] Figure 6A and Figure 6B Each shows a method that can be performed by an apparatus according to an example embodiment of the present invention. Specific implementation method:

[0033] Example embodiments of the present invention are directed to a framework for reducing the random access channel procedure load during group switching.

[0034] As described above, during the group handover procedure, there is a large amount of generated control plane load when preparing resources for the handover, thereby ensuring the execution of the handover, and releasing resources after the handover is completed, and the scenario where these group UEs perform handovers closely or simultaneously can lead to a high RACH load in the target cell.

[0035] Furthermore, in the above scenario where a group of UEs performs handover simultaneously, a high RACH load in the target cell may result.

[0036] As one of the main use cases of the random access channel, the random access channel is an UL physical channel adopted by the UE to initiate access to the network, but it is also used during handover and other procedures (such as PDCCH orders or beam failure recovery).

[0037] T304 timer: This timer is associated with the handover process. When the timer expires, the UE shall initiate the RRC re-establishment process. The currently defined triggers that enable the UE to access the base station are defined in the standard.

[0038] RACH resources are typically limited to 64 preambles per RACH opportunity, and these preambles are used for many purposes, including early identification of UE capabilities. In a typical configuration of 64 preambles, the cell reserves approximately 24 dedicated preambles for handover and other purposes (e.g., PDCCH orders).

[0039] If more than 24 UEs need to perform HO to the same target cell at roughly the same time, some UEs will have to resort to contention-based access during the HO process due to the lack of dedicated preamble resources, resulting in higher outage times. This can lead to a poor end-user experience for high-speed trains constantly moving through the cell.

[0040] Adding RACH resources may be a simple solution, but this imposes additional overhead since new RACH resources may need to be reserved for each beam and all UEs within a group may be in a single beam.

[0041] Furthermore, the high burstiness of RACH preambles may cause a surge in UL interference, thereby degrading neighboring cell performance. RACH processing requires high computational power, so it would be beneficial to avoid decoding the preamble for every UE in the group.

[0042] Therefore, for at least these reasons, example embodiments of the present invention are directed to addressing the problem of how to efficiently handle RACH procedures during group handover scenarios.

[0043] According to current 3GPP specifications, the RACH procedure is performed independently for each device in the group, and therefore differs from the proposed solution. In other prior art techniques, the UE group is determined by the relay UE based on measurement reports. In an example embodiment of the present invention, the group is determined by the target cell based on, for example, the relevance of the UE's last visited cell. In an example embodiment of the present invention, this eliminates the need for UE relay to enable group HO enhancement.

[0044] However, before describing exemplary embodiments of the present invention in further detail, reference is made to Figure 5 . Figure 5 A block diagram is shown of one possible and non-limiting exemplary system in which exemplary embodiments may be practiced.

[0045] like Figure 5As shown, user equipment (UE) 110 wirelessly communicates with wireless network 100. A UE is a wireless device that can access a wireless network, typically a mobile device. UE 110 includes one or more processors 120, one or more memories 125, and one or more transceivers 130, interconnected via one or more buses 127. Each of the one or more transceivers 130 includes a receiver (Rx) 132 and a transmitter (Tx) 133. The one or more buses 127 can be an address bus, a data bus, or a control bus, and can include any interconnect mechanism, such as a series of wires on a motherboard or integrated circuit, optical fiber, or other optical communication equipment. The one or more transceivers 130 are connected to one or more antennas 128. The one or more memories 125 include computer program code 123. UE 110 may include an access module 140 configured to perform the example embodiments of the present invention described herein. Access module 150 may be implemented solely in hardware or as part of the processor and / or computer program code of UE 110. Access module 140 includes one or both of portion 140-1 and / or portion 140-2. Access module 140 can be implemented in a variety of ways. Access module 140 can be implemented in hardware as access module 140-1, for example, as part of one or more processors 120. Access module 140-1 can also be implemented as an integrated circuit or through other hardware, such as a programmable gate array. In another example, access module 140 can be implemented as access module 140-2, which is implemented as computer program code 123 and executed by one or more processors 120. Note that access module 140-1 and / or access module 140-2 are optional. For example, one or more memories 125 and computer program code 123 can be configured, along with one or more processors 120, to enable user equipment 110 to perform one or more operations described herein. UE 110 communicates with gNB node 170 via wireless link 111 and with LMF 200 via link 221.

[0046] gNB 170 (NR / 5G Node B or possibly eNB) is a base station (e.g., for LTE, Long Term Evolution) that provides access to wireless network 100 by wireless devices (such as UE 110). gNB 170 includes one or more processors 152, one or more memories 155, one or more network interfaces (N / WI / F) 161, and one or more transceivers 160, interconnected via one or more buses 157. Each of the one or more transceivers 160 includes a receiver Rx 162 and a transmitter Tx 163. The one or more transceivers 160 are connected to one or more antennas 158. The one or more memories 155 include computer program code 153. gNB 170 includes an access module 150 configured to perform the example embodiments of the present invention as described herein. Access module 150 may include one or both of portion 150-1 and / or portion 150-2, which may be implemented in a variety of ways. The access module 150 can be implemented solely in hardware or as part of a processor and / or computer program code of the gNB 170. Access module 150-1, for example, is implemented as part of one or more processors 152. Access module 150-1 can also be implemented as an integrated circuit or other hardware implementation, such as a programmable gate array. In another example, access module 150 can be implemented as access module 150-2, which is implemented as computer program code 153 and executed by one or more processors 152. Note that access modules 150-1 and / or 150-2 are optional. For example, one or more memories 155 and computer program code 153 can be configured to work with one or more processors 152 to enable the gNB 170 to perform one or more operations as described herein. One or more network interfaces 161 communicate over a network (such as via links 176, 221, and link 131). Two or more gNBs 170 can communicate using, for example, link 176. Link 176 can be wired, wireless, or both, and can implement an X2 interface.

[0047] The one or more buses 157 may be an address bus, a data bus, or a control bus, and may include any interconnection mechanism, such as a series of wires on a motherboard or integrated circuit, optical fiber or other optical communication equipment, a wireless channel, etc. For example, the one or more transceivers 160 may be implemented as a remote radio head (RRH) 195, where the other elements of the gNB 170 are physically located in a different location from the RRH, and the one or more buses 157 may be implemented in part as a fiber optic cable to connect the other elements of the gNB node 170 to the RRH.

[0048] Note that the description herein indicates that a "cell" performs a function, but it should be clear that the gNB forming the cell also performs the function. A cell constitutes part of a gNB. That is, each gNB can have multiple cells.

[0049] The wireless network 100 may include NCE / MME / SGW / UDM / PCF / AMM / SMF 190, which may include a network control element (NCE), and / or a serving gateway (SGW) 190, and / or an MME (mobility management entity) and / or an SGW (serving gateway) function, and / or a user data management function (UDM), and / or a PCF (policy control) function, and / or an access and mobility management (AMM) function, and / or a session management (SMF) function, and / or an authentication server (AUSF) function, and the wireless network 100 provides connection to another network (such as a telephone network and / or a data communication network (e.g., the Internet)), and the wireless network 100 is configured to perform any 5G operation and / or NR operation in addition to or instead of other standard operations at the time of this application. The NCE / MME / SGW / UDM / PCF / AMM / SMF 190 may be configured to perform operations according to example embodiments of the present invention in any of LTE, NR, 5G, and / or any standards-based communication technologies being implemented or discussed at the time of this application.

[0050] gNB 170 is coupled to NCE / MME / SGW 190 via link 131 and to LMF 200 via link 131 and link 225. Link 131 or link 225 may be implemented as an S1 interface, for example. NCE / MME / SGW 190 includes one or more processors 175, one or more memories 171, and one or more network interfaces (N / WI / F) 180, interconnected via one or more buses 185. The one or more memories 171 include computer program code 173. The one or more memories 171 and the computer program code 173 are configured to, in conjunction with the one or more processors 175, cause NCE / MME / SGW 190 to perform one or more operations. Furthermore, NCE / MME / SGW 190 (like other devices) is equipped to perform operations such as controlling UE 110 and / or gNB 170 for 5G operation and / or NR operation, as well as any other standard operations as of the time of this application.

[0051] LMF 200 (NR / 5G Node B, evolved NB or LTE device) is a network node, such as a node including a location management function device (e.g., for NR or LTE long term evolution), which is connected to a network device such as Figure 5The LMF 200 provides access to wireless devices such as the UE 10 and the eNB / gNB 170. The LMF 200 provides access to the wireless network 1 for wireless devices such as the UE 10. The LMF 200 includes one or more processors DP 12A, one or more memories MEM 12B, and one or more transceivers TRANS 12D, interconnected via one or more buses. According to example embodiments, these TRANS 12D may include an X2 and / or Xn interface for implementing the example embodiments. Each of the one or more transceivers TRANS 12D includes a receiver and a transmitter. The one or more transceivers TRANS 12D may optionally be connected to one or more antennas for communicating with the UE 110 via at least a link 221. The one or more memories MEM 12B and computer program code PROG 12C are configured to, together with the one or more processors DP 12A, cause the LMF 200 to perform one or more operations as described herein. The LMF 200 may communicate with the gNB or eNB 170, such as via link 225 and link 131. In addition, the link 221, 225 or 131 and / or any other link can be wired or wireless or both, and can implement, for example, an X2 or Xn interface. In addition, the link 221, 225 or 131 can pass through other network devices, such as but not limited to, Figure 5 The NCE / MME / SGW / UDM / PCF / AMF / SMF / LMF 14 devices in the LMF 200 can perform the functions of an MME (Mobility Management Entity) or an SGW (Serving Gateway), such as user plane functions and / or access management functions for LTE and similar functions for 5G.

[0052] Wireless network 100 may implement network virtualization, which is the process of combining hardware and software network resources and network functions into a single, software-based managed entity, a virtual network. Network virtualization relates to platform virtualization and is often combined with resource virtualization. Network virtualization can be categorized as external, combining many networks or portions of networks into virtual units, or internal, providing network-like functionality to software containers on a single system. Note that the virtualized entities resulting from network virtualization are still implemented at some level using hardware, such as processors 152 or 175 and memories 155 and 171, and such virtualized entities also produce technical effects.

[0053] Computer-readable memories 125, 155, and 171 may be of any type suitable for the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory, and removable memory. Computer-readable memories 125, 155, and 171 may be components for performing storage functions. As non-limiting examples, processors 120, 152, and 175 may be of any type suitable for the local technical environment and may include one or more of a general-purpose computer, a special-purpose computer, a microprocessor, a digital signal processor (DSP), and a processor based on a multi-core processor architecture. Processors 120, 152, and 175 may be components for performing functions and controlling processes such as those described herein. Figure 5 Other functions of the network equipment of UE 110, gNB 170, and / or NCE / MME / SGW 190.

[0054] Note that according to an exemplary embodiment of the present invention, Figure 5 The functionality(ies) of any device shown (e.g., UE 110 and / or gNB 170) may also be implemented by other network nodes (e.g., wireless or wired relay nodes (also known as integrated access and / or backhaul (IAB) nodes)). In the case of IAB, the UE functionality may be implemented by the MT (mobile terminal) portion of the IAB node, and the gNB functionality may be implemented by the DU (data unit) portion of the IAB node. These devices may utilize at least the wireless link 111 and / or the NCE / MME / SGW 190 as shown. Figure 5 Links 199 to other network(s) / the Internet are shown connected to the UE 110 .

[0055] Example embodiments of the present invention propose a framework by which the RACH load during group handover is significantly reduced. The framework is based on the following novel steps according to example embodiments of the present invention: 1. The target cell receives a large number of HO requests from a single source cell within a defined short observation period (T_obs); 2. When the T_obs period expires, the target cell identifies the group HO scenario. The UEs that are part of the group HO are identified based on, for example, the correlation of the last visited cell information of the received handover request, the serving beam in the source cell and the target beam in the target cell, UE trajectory information, etc. 3. The target cell provides a single dedicated RACH preamble to all UEs in the group; 4. The target cell provides the UE with a handover command via the source cell with the following items: a. Dedicated preamble Id, b. An indication that the UE is part of a group HO; c. Indication of optional preamble transmission scheme 5. The UE may monitor the random access response message before initiating the RACH procedure with the assigned dedicated preamble, i.e., the start of the RAR window may be shifted left before the UE even transmits the first RACH preamble; 6. If the target cell knows that not all UEs in the group are active in the target cell, the target cell can proactively retransmit the RAR message; 7. If at any point (before expiration of T304) the UE receives a RAR with a RA-RNTI corresponding to the assigned dedicated preamble, the UE may consider that synchronization with the target cell has been successfully completed.

[0056] Note that in the described group HO scenario, the UEs all follow very similar mobility patterns, so the synchronization of one UE with the target cell can be leveraged for all UEs in the group. Even at a high speed of 300 km / h, for an SCS of 120 kHz, an observation window (T_obs) of 235 ms will result in an error of 1 TA unit. Lower SCSs will allow for much higher T_obs periods.

[0057] In addition, for situations where group HO is not common, the setting of T_obs may affect HO latency, so this setting should only be applied when needed. A large value of T_obs will result in a higher RACH preamble capacity gain, but if the UE speed is large, the reuse of the TA from one UE in the group to another UE in the initial UL transmission may have lower reliability. This parameter can also be set based on the RACH periodicity of the target cell. For example, if the RACH period is 20ms, a T_obs of 5ms is likely to have little impact.

[0058] exist Figure 1A In FIG, a flow chart of the target cell handover preparation process is depicted. At

[10] , the source cell may receive an incoming HO request. If the observation window timer (T_obs) is not running

[20] , it is started

[30] . When the T_obs timer expires, the target cell will attempt to determine the UE group

[50] . In an embodiment of the present invention, UE grouping (i.e., steps

[10] -

[50] ) may be performed in the source cell.

[0059] The UE group can be determined based on several aspects, for example, it can be based on UE history information from UE IE or UE History Information IE, which can be provided by the source cell via Xn during the handover request procedure. The UE history information from UE IE is based on VisitedCellInfoList IE, which includes mobility history information of up to 16 most recently visited primary cells in NR or E-UTRA or the time spent in any cell selection state and / or the time spent in any cell state. The UE History Information IE provides information about the UE's last visited cell, that is, information about the cell that the UE has been served by in the active state before the target cell.

[0060] A handover request for a UE with information about the last visited cell received within a short time span may imply that the UE belongs to a common group following similar mobility patterns, and thus the handover procedure for these UEs may be optimized. In addition to the above IEs, the beam of the UE in the source cell and the target beam in the target cell or UE trajectory information or artificial intelligence / machine learning techniques may also be employed for UE grouping.

[0061] In

[60] , after UE grouping has been performed, the target cell assigns a single dedicated preamble ID to each UE in the group. In addition, the target cell may provide an indication that the UE is performing group HO and UE-specific information to derive the RACH preamble transmission scheme

[70] .

[0062] In the HO execution phase ( Figure 1B ), according to the prior art, when the target cell receives a dedicated preamble ID, the target cell should transmit a RAR message. Alternatively, if the number of users is not yet active in the cell, for which handover resources are granted, the source cell may also actively and continuously transmit RAR messages associated with a specific group preamble ID [120-130].

[0063] The processing of the group HO process from the UE's perspective is as follows: Figure 2 is shown in .

[0064] In

[10] , the UE receives a HO command having at least an indication that the UE is a group HO, a dedicated preamble ID and optionally a RACH preamble transmission scheme. In

[20] , as Figure 3 As shown, the UE starts monitoring for RAR messages associated with the assigned dedicated preamble ID even before transmitting the RACH preamble. Figure 3 The comparison between the prior art and the proposed solution for ra-ResponseWindow is shown. Figure 3As shown, the main differences include: during the ra-ResponseWindow, the UE monitors the RAR even before transmitting the RACH preamble.

[0065] If at any point

[30] the UE decodes the RAR associated with the assigned dedicated preamble ID, the handover is complete and the UE resumes normal 3GPP operation. When the UE does not receive the expected RAR, it will determine whether it should transmit the preamble based on the scheme provided by the target cell [50-60]. In the simplest scheme, if the UE does not receive the RAR, the UE can transmit in every RACH opportunity, or the UE can transmit in every second RACH opportunity.

[0066] A more refined RACH preamble transmission scheme may be based on a threshold parameter and a factor parameter configured by the target cell for each UE. For each RACH opportunity within the T304 period, the UE may then: 1. Draw a random number from a uniform distribution between 0 and 1, 2. If the number is greater than the threshold, a dedicated preamble ID is used for transmission on the RACH, and 3. If the number is less than threshold or if the RAR message is not received, return to 1) but update threshold: threshold=threshold*factor

[0067] Using the above scheme and a factor greater than 1, the probability of a UE transmitting a RACH increases with each RACH opportunity.

[0068] exist Figure 4 In Figure 2, an example of this scheme for 4 UEs is shown. Here, one can observe how the threshold increases for each UE for each RACH opportunity. In the first RACH opportunity, 2 UEs will transmit a dedicated preamble ID, and in the last RACH opportunity, if they do not receive a RAR, 3 UEs will transmit a RACH preamble. Figure 4 As shown, the threshold and factor values are parameters configured by the target cell. With the correct parameterization of these parameters, the target cell can reduce the RACH load and thus reduce interference.

[0069] Since a single preamble can generate RARs for multiple users, the source cell RACH calculations are also reduced.

[0070] Within the described framework, the RAR window will be initiated by the UE upon receipt of a HO command plus the processing delay associated with the HO command. The UE will stop monitoring the RAR upon expiration of T304 or successful completion of the synchronization procedure.

[0071] Figure 6A and Figure 6B Each shows a method according to an exemplary embodiment of the present invention that can be performed by an apparatus.

[0072] Figure 6A shows that a network device such as, but not limited to, Figure 5 Operations performed by the network node eNB / gNB 170 or gNB or eNB in the example. Figure 6A As shown in step 610, the network node of the target cell receiving the handover request determines that there is at least one group of user equipment in the handover request. Figure 6A As shown in step 620 of , there is: determining a unique dedicated random access channel preamble to assign to each user equipment in at least one group of user equipments, wherein each dedicated random access channel preamble is used to initiate a random access channel procedure for a handover request in a plurality of handover requests. Then, as Figure 6A As shown in step 630, there is: providing information to the user equipment, the information including a dedicated random access channel preamble and a handover command for the handover request.

[0073] According to an exemplary embodiment of the present invention as disclosed in the above paragraphs, the determination of at least one group of user equipments within the handover request is based on an indication from a source cell.

[0074] According to an example embodiment of the present invention as disclosed in the above paragraphs, the determination of at least one group of user equipment at a target cell or at least one group of user equipment at a source cell within a handover request is based on the start of a predefined observation period, the start of which is confirmed based on the receipt of the handover request; and at least one non-volatile memory stores instructions that are executed by at least one processor to cause the device to at least: identify a group of user equipment for the handover request when the predefined observation period expires.

[0075] According to an exemplary embodiment of the present invention as disclosed in the above paragraphs, wherein the determining is based on identifying at least one group of user equipments for handover request upon expiry of a predefined observation period.

[0076] According to an exemplary embodiment of the present invention as disclosed in the above paragraphs, wherein the information comprises an indication that the user equipment is part of a group handover.

[0077] According to an example embodiment of the present invention as disclosed in the above paragraphs, the user equipment grouping is determined based on at least one of the following: historical information of the user equipment from the user equipment information element or historical information of the user equipment provided by the source cell through the Xn interface during the reception of the handover request, correlation of the last visited cell information, information of the received handover request, the service beam in the source cell, the target beam in the target cell, or user equipment trajectory information.

[0078] According to an exemplary embodiment of the present invention as disclosed in the above paragraphs, wherein the information comprises a configuration for the user equipment to determine the probability of transmission per random access channel opportunity period.

[0079] According to an exemplary embodiment of the present invention as disclosed in the above paragraphs, there is sent by the network node via the source cell to the user equipment an indication that the user equipment is to perform handover and obtain random access channel preamble transmission schemes for different random access channel occasions.

[0080] According to an exemplary embodiment of the present invention as disclosed in the above paragraphs, wherein the random access channel preamble transmission scheme is based on a threshold parameter and a factor parameter configured for a user equipment.

[0081] According to an example embodiment of the present invention as disclosed in the above paragraphs, there is: a random number is drawn from a uniform distribution between 0 and 1; and at least one of the following: based on the random number being greater than a threshold, using the assigned dedicated random access channel preamble code identifier to transmit on the random access channel, or based on one of the random number being less than the threshold or the random access response message not being received, updating the threshold to threshold = threshold * factor, wherein when factor is greater than 1, the probability of the user equipment transmitting the random access channel increases with each random access channel opportunity.

[0082] According to an exemplary embodiment of the present invention as disclosed in the above paragraphs, there is proactively retransmitting a random access response message performed for handover based on user equipment in at least one group of user equipment being inactive in a target cell.

[0083] According to an exemplary embodiment of the present invention as disclosed in the above paragraphs, wherein the information is provided to the user equipment via the source cell.

[0084] According to an exemplary embodiment of the present invention as disclosed in the above paragraphs, there is initiated a predefined observation period based on the initiation of the predefined observation period not being confirmed.

[0085] Non-transitory computer readable media (such as Figure 5 The memory(s) 155 in the memory store program code (e.g. Figure 5Computer program code 153 and / or access module 150-2 in the computer program code, the program code is executed by at least one processor (such as Figure 5 (Multiple) processors 152 and / or access module 150-1) in the processor 152 and / or access module 150-1 execute to perform at least the operations described in the above paragraphs.

[0086] According to the exemplary embodiment of the present invention as described above, there is an apparatus comprising: a network node (e.g., a target cell) for receiving a handover request; Figure 5 eNB / gNB 170) in the Figure 5 remote radio head 195, memory(ies) 155, computer program code 153 and / or access module 150-2 and processor(ies) 152 and / or access module 150-1) in a handover request wherein at least one set of user equipment components is present; for determining (e.g. Figure 5 remote radio head 195, memory(ies) 155, computer program code 153 and / or access module 150-2 and processor(ies) 152 and / or access module 150-1) in the at least one group of user equipments to assign a unique dedicated random access channel preamble to each user equipment (e.g., Figure 5 10) in the UE, wherein each dedicated random access channel preamble is used to initiate (e.g. Figure 5 remote radio head 195, (multiple) memory 155, computer program code 153 and / or access module 150-2 and (multiple) processor 152 and / or access module 150-1 in the plurality of handover requests for a random access channel procedure; and for providing (e.g. Figure 5 The remote radio head 195, the memory(s) 155, the computer program code 153 and / or the access module 150-2 and the processor(s) 152 and / or the access module 150-1 in FIG. 1 , wherein the ...

[0087] In an exemplary aspect of the invention according to the above paragraphs, at least the means for determining and providing comprises a computer program encoded with [e.g. Figure 5 The computer program code 153 and / or access module 150-2 in the non-transitory computer readable medium [such as Figure 5 (a plurality of) memories 155], the computer program may be executed by at least one processor [e.g. Figure 5 (multiple) processors 152 and / or access modules 150-1] are executed.

[0088] Figure 6B It shows that the device can be used by, for example, but not limited to, Figure 5The operation performed by the device of UE 110 in FIG. Figure 6B As shown in step 650, the user equipment receives information about a handover command to a target cell from a source cell of a communication network device, the information including an assigned dedicated random access channel preamble and an indication of a group handover for initiating a random access channel procedure for handover. Then, as Figure 6B As shown in step 660, based on the information about the handover command, handover is performed.

[0089] According to an exemplary embodiment of the present invention as disclosed in the above paragraphs, wherein in response to receiving the indication, the random access channel procedure initiates monitoring in the random access response window before transmitting the first random access channel preamble.

[0090] According to an exemplary embodiment of the present invention as disclosed in the above paragraphs, there is one of: sending a dedicated preamble identifier towards a target cell or determining whether to send a dedicated preamble identifier towards the target cell based on a random access response message with a random access radio network temporary identifier, the random access radio network temporary identifier corresponding to the assigned dedicated random access channel preamble; and determining synchronization with the target cell for successfully completing handover.

[0091] According to an exemplary embodiment of the present invention as disclosed in the above paragraphs, wherein the information comprises a configuration for the user equipment to determine a probability of transmission of a dedicated preamble per random access channel opportunity period.

[0092] According to an exemplary embodiment of the present invention as disclosed in the above paragraphs, there is received by a user equipment an indication that the user equipment is to perform a handover and obtain a random access channel preamble transmission scheme for different random access channel opportunities.

[0093] According to an exemplary embodiment of the present invention as disclosed in the above paragraphs, wherein the random access channel preamble transmission scheme is based on a threshold parameter and a factor parameter configured for a user equipment.

[0094] According to an example embodiment of the present invention as disclosed in the above paragraphs, there are: a random number is drawn from a uniform distribution between 0 and 1; and at least one of the following: based on the random number being greater than a threshold, the assigned dedicated random access channel preamble code identifier is used to transmit on the random access channel, or based on one of the random number being less than the threshold or the random access response message not being received, the threshold is updated to threshold = threshold * factor, wherein when factor is greater than 1, the probability of the user equipment transmitting the random access channel increases at each random access channel opportunity.

[0095] Non-transitory computer readable media (such as Figure 5The memory(s) 125 in the memory store program code (e.g. Figure 5 Computer program code 123 and / or access module 140-2 in the computer program code, the program code is executed by at least one processor (such as Figure 5 (Multiple) processors 120 and / or access module 140-1) in the processor 120 and / or access module 140-1) execute to perform at least the operations described in the above paragraphs.

[0096] According to the exemplary embodiment of the present invention as described above, there is an apparatus comprising: Figure 5 UE 110 in the communication network (such as Figure 5 The source cell of the network 100) receives (eg Figure 5 one or more transceivers 130, memory(ies) 125, computer program code 123 and / or access module 140-2 and processor(s) 120 and / or access module 140-1 in the handover command to the target cell, the information including an assigned dedicated random access channel preamble and an indication of group handover for initiating a random access channel procedure for handover; and based on the information about the handover command, performing (e.g. Figure 5 One or more transceivers 130, (multiple) memories 125, computer program code 123 and / or access module 140-2 and (multiple) processors 120 and / or access module 140-1) switching components.

[0097] In an exemplary aspect of the invention according to the above paragraphs, at least the means for determining and providing comprises a computer program encoded with [e.g. Figure 5 The computer program code 123 and / or access module 140-2 in the non-transitory computer readable medium [such as Figure 5 (a plurality of) memories 125], the computer program may be executed by at least one processor [e.g. Figure 5 (multiple) processors 120 and / or access modules 140-1] are executed.

[0098] Advantages of example embodiments according to the present invention include: · Reduction of RACH capacity required for group handover, Reduction in RACH computation requirements for group handover, and • Reduction of RACH interference caused by group switching.

[0099] Furthermore, according to example embodiments of the present invention, there is a circuit system for performing operations according to example embodiments of the present invention as disclosed herein. The circuit system may include any type of circuit, including content encoding and decoding circuit systems, content decoding circuit systems, processing circuit systems, image generation circuit systems, data analysis circuit systems, and the like. Furthermore, the circuit system may include discrete circuit systems, application specific integrated circuit systems (ASICs) and / or field programmable gate array circuit systems (FPGAs), and the like, as well as processors specifically configured by software to perform corresponding functions, or dual-core processors with software and corresponding digital signal processors, and the like. Additionally, the necessary inputs to and outputs from the circuit system, the functions performed by the circuit system, and the interconnection of the circuit system with other components, which may include other circuit systems (possibly via inputs and outputs), are provided to perform example embodiments of the present invention as described herein.

[0100] According to exemplary embodiments of the present invention disclosed in this application, the provided “circuitry system” may include at least one or more or all of the following: (a) hardware circuit implementation only (such as implementation only in analog and / or digital circuitry); (b) a combination of hardware circuitry and software, such as (if applicable): (i) a combination of analog and / or digital hardware circuit(s) with software / firmware; and (ii) any portion of a hardware processor(s) with software (including digital signal processor(s), software, memory(s) that work together to enable a device such as a mobile phone or server to perform various functions, such as functions or operations according to example embodiments of the present invention as disclosed herein); and (c) Hardware circuit(s) and / or processor(s), such as microprocessor(s) or portions of microprocessor(s) that require software (e.g., firmware) for operation (but where software is not required for operation, the software may not be present).

[0101] In general, the various embodiments may be implemented in hardware or dedicated circuitry, software, logic, or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software that may be executed by a controller, microprocessor, or other computing device, but the invention is not limited thereto. Although various aspects of the invention may be shown and described as block diagrams, flow charts, or described using some other graphical representation, it should be understood that, as non-limiting examples, the blocks, devices, systems, techniques, or methods described herein may be implemented in hardware, software, firmware, dedicated circuitry or logic, general-purpose hardware or a controller or other computing device, or some combination thereof.

[0102] Embodiments of the present disclosure may be practiced in various components such as integrated circuit modules. The design of integrated circuits is a highly automated process. Complex and powerful software tools are available to convert a logic-level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate.

[0103] As used herein, the word "exemplary" means "serving as an example, instance, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. All embodiments described in the detailed description are exemplary embodiments provided to enable those skilled in the art to make or use the invention and are not intended to limit the scope of the invention, which is defined by the claims.

[0104] The foregoing description has provided by way of exemplary and non-limiting examples a complete and informative description of the best method and apparatus presently contemplated by the inventors for carrying out the invention. However, various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description when read in conjunction with the accompanying drawings and the appended claims. Nevertheless, all such and similar modifications of the teachings of this invention will still fall within the scope of this invention.

[0105] It should be noted that the terms "connected," "coupled," or any variations thereof, mean any connection or coupling, direct or indirect, between two or more elements, and may encompass the presence of one or more intermediate elements between two elements that are "connected" or "coupled" together. The coupling or connection between elements may be physical, logical, or a combination thereof. As used herein, two elements may be considered to be "connected" or "coupled" together through the use of one or more wires, cables, and / or printed electrical connections, as well as through the use of electromagnetic energy, such as electromagnetic energy having a wavelength in the radio frequency region, the microwave region, and the optical (visible and invisible) region, as several non-limiting and non-exhaustive examples.

[0106] Furthermore, some of the features of the preferred embodiments of this invention may be used to advantage without the corresponding use of other features.The foregoing description should therefore be considered as merely illustrative of the principles of the invention and not in limitation thereof.

Claims

1. A device comprising: at least one processor; as well as at least one non-transitory memory storing instructions that, when executed by the at least one processor, cause the apparatus to at least: determining, by a network node of a target cell receiving a handover request, that at least one group of user equipment exists within the handover request; determining a unique dedicated random access channel preamble to assign to each user equipment in the at least one group of user equipments, wherein each dedicated random access channel preamble is used to initiate a random access channel procedure for a handover request in the plurality of handover requests; as well as Information is provided to the user equipment, the information including the dedicated random access channel preamble and a handover command for the handover requested. 2 . The apparatus of claim 1 , wherein the determination of the at least one group of user equipment within the handover request is based on an indication from a source cell.

3. The apparatus according to claim 1 , wherein the determination of the at least one group of user equipment at the target cell or at the source cell of the at least one group of user equipment within the handover request is based on the start of a predefined observation period, the start of the predefined observation period being confirmed based on the receipt of the handover request; and wherein the at least one non-transitory memory stores instructions that are executable by the at least one processor to cause the apparatus to at least: identify a set of user equipment for the handover request upon expiration of the predefined observation period; The apparatus of claim 3, wherein the determining is based on identifying the at least one group of user equipments for the handover request upon expiration of the predefined observation period. The apparatus of claim 1 , wherein the information comprises an indication that the user equipment is part of a group handover.

5. The apparatus according to claim 2, wherein the user equipment group is determined based on at least one of the following: Historical information of the user equipment from the user equipment information element or historical information of the user equipment provided by the source cell through the Xn interface during reception of the switching request, correlation of the last visited cell information, information of the received switching request, the service beam in the source cell, the target beam in the target cell, or user equipment trajectory information. 6 . The apparatus according to claim 1 , wherein the information comprises a configuration for the user equipment to determine a probability of transmission per random access channel opportunity period.

7. The apparatus of claim 1 , wherein the at least one non-transitory memory stores instructions that are executable by the at least one processor to cause the apparatus to at least: The network node sends an indication to the user equipment via the source cell, indicating that the user equipment is to perform handover and obtain a random access channel preamble transmission scheme for different random access channel opportunities.

8. The apparatus of claim 8, wherein the random access channel preamble transmission scheme is based on a threshold parameter and a factor parameter configured for the user equipment.

9. The apparatus of claim 8, wherein the at least one non-transitory memory stores instructions that are executable by the at least one processor to cause the apparatus to at least: A random number drawn from a uniform distribution between 0 and 1; and at least one of the following: Based on the random number being greater than the threshold, using the assigned dedicated random access channel preamble identifier to transmit on the random access channel, or Based on one of the following: the random number is less than the threshold or the random access response message is not received, updating the threshold to threshold=threshold*factor; When the factor is greater than 1, the probability of the user equipment transmitting the random access channel increases with each random access channel opportunity.

10. The apparatus of claim 1 , wherein the at least one non-transitory memory stores instructions that are executable by the at least one processor to cause the apparatus to at least: Actively retransmitting a random access response message for handover execution based on the user equipment in the at least one group of user equipment being inactive in the target cell. The apparatus according to claim 1 , wherein the information is provided to the user equipment via the source cell.

12. The apparatus of claim 1 , wherein the at least one non-transitory memory stores instructions that are executable by the at least one processor to cause the apparatus to at least: Based on the initiation of the predefined observation period not being confirmed, the predefined observation period is initiated.

13. A method comprising: determining, by a network node of a target cell receiving a handover request, that at least one group of user equipment exists within the handover request; determining a unique dedicated random access channel preamble to assign to each user equipment in the at least one group of user equipments, wherein each dedicated random access channel preamble is used to initiate a random access channel procedure for a handover request in the plurality of handover requests; as well as Information is provided to the user equipment, the information including the dedicated random access channel preamble and a handover command for the handover requested.

14. The method according to claim 13, wherein the determination of the at least one group of user equipment within the handover request is based on an indication from a source cell.

15. The method according to claim 13 , wherein the determination of the at least one group of user equipment at the target cell or at the source cell of the at least one group of user equipment within the handover request is based on the start of a predefined observation period, the start of the predefined observation period being confirmed based on the receipt of the handover request; and The method further comprises: Upon expiration of the predefined observation period, a group of user equipments for the handover request is identified.

16. The method of claim 15, wherein the determining is based on identifying the at least one group of user equipments for the handover request upon expiration of the predefined observation period.

17. The method of claim 13, wherein the information comprises an indication that the user equipment is part of a group handover.

18. The method of claim 14, wherein the user equipment grouping is determined based on at least one of: Historical information of the user equipment from the user equipment information element or historical information of the user equipment provided by the source cell through the Xn interface during reception of the switching request, correlation of the last visited cell information, information of the received switching request, the service beam in the source cell, the target beam in the target cell, or user equipment trajectory information.

19. The method of claim 13, wherein the information comprises a configuration for the user equipment to determine a probability of transmission per random access channel opportunity period.

20. The method of claim 13, further comprising: The network node sends an indication to the user equipment via the source cell, indicating that the user equipment is to perform handover and obtain a random access channel preamble transmission scheme for different random access channel opportunities.

21. The method of claim 20, wherein the random access channel preamble transmission scheme is based on a threshold parameter and a factor parameter configured for the user equipment.

22. The method according to claim 20, comprising: Draw a random number from a uniform distribution between 0 and 1; AND at least one of the following: Based on the random number being greater than the threshold, using the assigned dedicated random access channel preamble identifier to transmit on the random access channel, or Based on one of the following: the random number is less than the threshold or the random access response message is not received, updating the threshold to threshold=threshold*factor; When the factor is greater than 1, the probability of the user equipment transmitting the random access channel increases at each random access channel opportunity.

23. The method of claim 13, further comprising: Actively retransmitting a random access response message for handover execution based on the user equipment in the at least one group of user equipment being inactive in the target cell.

24. The method of claim 13, wherein the information is provided to the user equipment via the source cell.

25. The method of claim 13, further comprising: Based on the initiation of the predefined observation period not being confirmed, the predefined observation period is initiated.

26. An apparatus comprising: means for determining, by a network node of a target cell receiving a handover request, that at least one group of user equipment is present within the handover request; means for determining a unique dedicated random access channel preamble to assign to each user equipment in said at least one group of user equipment, wherein each dedicated random access channel preamble is used to initiate a random access channel procedure for a handover request in said plurality of handover requests; as well as means for providing information to the user equipment, the information comprising the dedicated random access channel preamble and a handover command for the handover requested.

27. An apparatus comprising: at least one processor; and at least one non-transitory memory storing instructions that, when executed by the at least one processor, cause the apparatus to at least: receiving, by the user equipment, information regarding a handover command to a target cell from a source cell of a communication network device, the information including an assigned dedicated random access channel preamble and an indication of a group handover for initiating a random access channel procedure for the handover; as well as Based on the information about the handover command, handover is performed.

28. The apparatus of claim 27, wherein in response to receiving the indication, the random access channel process initiates monitoring in the random access response window before transmitting a first random access channel preamble.

29. The apparatus of any one of claim 27 or claim 28, wherein the at least one non-transitory memory stores instructions that are executable by the at least one processor to cause the apparatus to at least: One of: sending a dedicated preamble identifier toward the target cell or determining whether to send a dedicated preamble identifier toward the target cell based on a random access response message having a random access radio network temporary identifier corresponding to the assigned dedicated random access channel preamble; and Synchronization with the target cell is determined for successfully completing the handover.

30. The apparatus of claim 27, wherein the information comprises a configuration for the user equipment to determine a probability of transmission of the dedicated preamble per random access channel opportunity period.

31. The apparatus of claim 27, wherein the at least one non-transitory memory stores instructions executable by the at least one processor to cause the apparatus to at least: An indication is received by the user equipment that the user equipment is to perform a handover and obtain a random access channel preamble transmission scheme for different random access channel opportunities.

32. The apparatus of claim 31, wherein the random access channel preamble transmission scheme is based on a threshold parameter and a factor parameter configured for the user equipment.

33. The apparatus of claim 32, wherein the at least one non-transitory memory stores instructions executable by the at least one processor to cause the apparatus to at least: A random number drawn from a uniform distribution between 0 and 1; and at least one of the following: Based on the random number being greater than the threshold, using the assigned dedicated random access channel preamble identifier to transmit on the random access channel, or Based on one of the following: the random number is less than the threshold or the random access response message is not received, updating the threshold to threshold=threshold*factor; When the factor is greater than 1, the probability of the user equipment transmitting the random access channel increases at each random access channel opportunity.

34. A method comprising: receiving, by the user equipment, information regarding a handover command to a target cell from a source cell of a communication network device, the information including an assigned dedicated random access channel preamble and an indication of a group handover for initiating a random access channel procedure for the handover; as well as Based on the information about the handover command, handover is performed.

35. The method of claim 34, wherein in response to receiving the indication, the random access channel process initiates monitoring in the random access response window before transmitting a first random access channel preamble.

36. The method of any one of claim 34 or claim 35, wherein the at least one non-transitory memory stores instructions that are executed by the at least one processor to cause the apparatus to at least: One of: sending a dedicated preamble identifier toward the target cell or determining whether to send a dedicated preamble identifier toward the target cell based on a random access response message having a random access radio network temporary identifier corresponding to the assigned dedicated random access channel preamble; and Synchronization with the target cell is determined for successfully completing the handover.

37. The method of claim 34, wherein the information includes a configuration for the user equipment to determine a probability of transmission of the dedicated preamble per random access channel opportunity period.

38. The method of claim 34, further comprising: An indication is received by the user equipment that the user equipment is to perform a handover and obtain a random access channel preamble transmission scheme for different random access channel opportunities.

39. The method of claim 38, wherein the random access channel preamble transmission scheme is based on a threshold parameter and a factor parameter configured for the user equipment.

40. The method of claim 39, further comprising: Draw a random number from a uniform distribution between 0 and 1; AND at least one of the following: Based on the random number being greater than the threshold, using the assigned dedicated random access channel preamble identifier to transmit on the random access channel, or Based on one of the above, that the random number is less than the threshold or the random access response message is not received, updating the threshold to threshold=threshold*factor; When the factor is greater than 1, the probability of the user equipment transmitting the random access channel increases at each random access channel opportunity.

41. An apparatus comprising: means for receiving, by a user equipment, information regarding a handover command to a target cell from a source cell of a communications network device, the information comprising an assigned dedicated random access channel preamble and an indication of a group handover for initiating a random access channel procedure for the handover; as well as Means for performing handover based on said information regarding said handover command.

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