System, method, user equipment and base station for performing handover in wireless network

Abstract

The present disclosure relates to a wireless communication method for supporting a handover from a first base station to a second base station by a user equipment, the method comprising the steps of: obtaining (316) a random access scheduling configuration of at least the user equipment, the configuration comprising at least a random access delay value; upon receiving a handover command from the first base station, starting (317) a timer configured according to the random access delay value; and triggering (319) a delayed random access procedure to the second base station when the timer expires (318). The disclosure also provides a wireless communication method in which a first base station performs handover of at least one user equipment from a second base station to the first base station; user equipment, base station and wireless system for implementing the method.

Description

Technical Field

[0001] The following relates generally to wireless communications, and more particularly to an improved handover method in a non-terrestrial network. Background Art

[0002] Wireless communication systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on.

[0003] A wireless multiple access communication system may include multiple base stations, each of which supports communication for multiple mobile devices simultaneously. A base station can communicate with UEs on both the downlink and uplink. Each base station has a coverage area, sometimes referred to as a cell coverage area.

[0004] Non-terrestrial networks (NTN) have become a general term for any network involving non-terrestrial flying objects, such as satellite communications networks or high altitude platform systems (HAPS), which include aircraft, balloons and airships.

[0005] Satellite communication networks rely on spaceborne platforms consisting of low earth orbit (LEO) satellites, medium earth orbit (MEO) satellites and geosynchronous earth orbit (GEO) satellites.

[0006] There is growing interest in broadband supported by LEO NTNs using large satellite constellations, as LEO NTNs have smaller propagation delays and higher link quality than MEO or GEO satellites. The satellite industry is currently working on integrating satellite networks into the 5G ecosystem in the 3GPP process.

[0007] The integration of non-terrestrial networks (NTNs) within the 5G framework is being standardized and may bring multiple advantages, such as broad service coverage capabilities, reduced vulnerability of space / air vehicles to physical attacks and natural disasters, or enhanced service reliability.

[0008] However, NTN integration also brings challenges related to the application and adaptation of technologies originally designed for terrestrial networks to space networks.

[0009] In particular, handovers in LEO satellite networks differ significantly from traditional terrestrial cellular networks in that handovers are triggered by the mobility of the satellite. In terrestrial networks, there are relatively small fixed cells and mobile UEs, while in non-terrestrial networks, cells move with the movement of satellites. In contrast, UE movement is slow and sometimes negligible. Once a LEO satellite moves to a new cell, most (if not all) UEs will be handed over to another cell.

[0010] Given the large cell sizes of non-terrestrial networks, multiple devices can be served within a single cell. Depending on the constellation assumptions (e.g., propagation delay and satellite speed) and UE density, there may be a large number of UEs that need to be handed over in a given time, which may result in large signaling overhead and high power consumption, and pose service continuity challenges. In addition, if many UEs need to be handed over from one base station to another, random access conflicts between UEs will increase.

[0011] Therefore, a handover method is needed to reduce random access conflicts and UE energy consumption. Summary of the invention

[0012] According to one aspect of the present disclosure, there is provided a wireless communication method for supporting handover from a first base station to a second base station by a user equipment, the method comprising:

[0013] - obtaining a random access scheduling configuration of at least the user equipment, the configuration comprising at least a random access delay value,

[0014] - starting a timer configured according to the random access delay value upon receiving a handover command from the first base station,

[0015] - triggering a delayed random access procedure to the second base station when the timer expires.

[0016] Therefore, it is proposed that the user equipment obtains a specific RACH delay timer value and waits for the delay to expire before performing random access (e.g., transmitting a random access preamble). In this way, it can be understood that the random access process performed by a group of user equipments is thus spread out over time, so that the risk of collision events can be reduced.

[0017] In one embodiment, the obtained random access scheduling configuration further comprises a random access backoff delay value, and the method comprises the step of applying the backoff delay value when the random access procedure fails.

[0018] Therefore, the random access scheduling configuration obtained by the user equipment may include a backoff delay value. Therefore, if a first random access attempt of the user equipment fails, the user equipment may apply such a backoff delay value before initiating a new random access attempt.

[0019] In one embodiment, the random access scheduling configuration is obtained from a message including the random access scheduling configuration.

[0020] The random access scheduling configuration is transmitted to the user equipment in a message (eg, a handover command message).For example, the RRC reconfiguration message may include a random access delay timer and / or a random access backoff timer.

[0021] In one embodiment, the message including the random access scheduling configuration is received from the first base station.

[0022] In one embodiment, the random access scheduling configuration obtained for the user equipment is determined according to a QoS profile and / or priority associated with the user equipment.

[0023] In this way, the random access scheduling configuration (including the random access delay value and / or the random access backoff value) obtained by the user equipment depends at least on the priority value and / or the quality of service (QoS) profile associated with the user equipment: therefore, a high priority user equipment will be set with a smaller RACH delay timer and / or backoff value than a low priority user equipment.

[0024] This provision allows random accesses to be spread out over a period of time while favoring user equipment with the highest priority and / or QoS requirements.

[0025] In one embodiment, the message including the random access scheduling configuration is received from the second UE using sidelink communication.

[0026] The first relay UE may collect random access configurations of multiple attached UEs and distribute these configurations to the corresponding UEs. This provision reduces signaling overhead.

[0027] According to another embodiment, the step of obtaining the random access scheduling configuration comprises the following steps:

[0028] - receiving an RRC signalling message including QoS parameters,

[0029] -Looking up a random access scheduling configuration associated with said received QoS parameters in a pre-configured lookup table.

[0030] The mapping between the QoS parameters and the specific random access scheduling configuration is preconfigured in the user equipment. Thus, the random access delay is determined by the user equipment based on the QoS parameters transmitted by the base station in the RCC message. This provision allows saving bandwidth resources by reducing the amount of data exchanged between the user equipment and the source base station. In addition, the method can be implemented using a prior art base station using a traditional QoS profile transmission from the source base station to the user equipment.

[0031] Another aspect of the present disclosure relates to a wireless user equipment for supporting a handover from a first base station to a second base station, the wireless user equipment comprising a processor coupled to a memory having computer program instructions stored therein, wherein the processor is configured by the computer program instructions to:

[0032] - obtaining a random access scheduling configuration of at least the user equipment, the configuration comprising at least a random access delay value,

[0033] - starting a timer configured according to the determined random access delay value upon receiving a handover command from the first base station,

[0034] - triggering a delayed random access procedure to the second base station when the timer expires.

[0035] According to another aspect of the present disclosure, there is provided a wireless communication method for performing, by a first base station, a handover of at least one user equipment from a second base station to the first base station, the method comprising:

[0036] - receiving a handover request from the second base station, the handover request comprising at least a priority value and / or a QoS profile associated with the user equipment,

[0037] - determining a random access scheduling configuration according to at least the user equipment priority value and / or the QoS profile, the random access scheduling configuration comprising at least a random access delay value,

[0038] - Transmitting a handover response message including the determined random access scheduling configuration to the second base station.

[0039] In an embodiment, the random access scheduling configuration further includes a random access backoff delay value.

[0040] Another aspect of the present disclosure relates to a base station for performing handover of at least one user equipment in a wireless network, the base station comprising a processor coupled to a memory having computer program instructions stored therein, wherein the processor is configured by the computer program instructions to implement a wireless communication method for performing handover, the method comprising:

[0041] - receiving a handover request from the second base station, the handover request comprising at least a priority value and / or a QoS profile associated with the user equipment,

[0042] - determining a random access scheduling configuration according to at least the user equipment priority value and / or the QoS profile, the random access scheduling configuration comprising at least a random access delay value,

[0043] - Transmitting a handover response message including the determined random access scheduling configuration to the second base station.

[0044] According to another aspect, a wireless communication system for performing handover of a user equipment from a first base station to a second base station is provided, the second base station comprising a processor coupled to a memory having computer program instructions stored therein, wherein the processor is configured by the computer program instructions to implement a wireless communication method for performing handover, the method comprising:

[0045] - receiving a handover request from said first base station, the handover request comprising at least one priority value and / or QoS profile associated with said user equipment,

[0046] - determining a random access scheduling configuration according to at least the user equipment priority value and / or the QoS profile, the random access scheduling configuration comprising at least a random access delay value,

[0047] - transmitting a handover response message including the determined random access scheduling configuration to the first base station, and

[0048] The user equipment comprises a processor, the processor is coupled to a memory, the memory stores computer program instructions, wherein the processor is configured by the computer program instructions to:

[0049] - receiving a random access scheduling configuration from the first base station, the random access scheduling configuration comprising at least a random access delay value,

[0050] - starting a timer configured according to the received random access delay value,

[0051] - triggering a delayed random access procedure to the second base station when the timer expires.

[0052] In a specific embodiment, each step of the wireless communication method for user equipment supporting handover and the wireless communication method for base station performing handover is determined by instructions of a computer program.

[0053] Therefore, the present disclosure further contemplates computer programs on an information medium, which are suitable for implementation in a user equipment and a base station, respectively, or more generally in a computer, which programs respectively include instructions adapted to implement the steps of the wireless communication method supported by the user equipment and performed by the base station, respectively, which have just been described.

[0054] These programs may use any programming language and may be in the form of source code, object code, or an intermediate code between source code and object code, such as partially compiled form or any other desired form.

[0055] On the other hand, an information medium readable by a computer is envisaged, which information medium comprises instructions of a computer program such as mentioned above.

[0056] The information medium may be any entity or device capable of storing a program. For example, the medium may include a storage device such as a ROM (e.g., a CD ROM or a microelectronic circuit ROM), an EEPROM, a FLASH memory, or any magnetic recording device (e.g., a hard disk drive).

[0057] Furthermore, the information medium may be a transmissible medium such as an electric signal or an optical signal that can be transmitted via an electric or optical cable by radio or by other means.In particular, the program according to the embodiment of the present invention may be downloaded from a network.

[0058] Alternatively, the information medium may be an integrated circuit in which the program is contained, the circuit being arranged for carrying out or for carrying out the method in question.

[0059] The advantages of the user equipment, the base station and the system, as well as the corresponding computer program and information medium are the same as those presented with respect to the corresponding method according to any of the above-described embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Other advantages and characteristics of the invention will become more apparent on reading the following description, given by way of simple illustrative and non-limiting examples, and the accompanying drawings, in which:

[0061] - Figure 1 A wireless communication system arranged to implement a wireless communication method for performing a handover according to an embodiment is presented,

[0062] - Figure 2 is a combined flow chart and block diagram showing the prior art inter-cell handover process,

[0063] - Figure 3a is a combined flow chart and block diagram showing the main steps of a wireless communication method for performing a handover of a UE from a source base station to a target base station according to an embodiment,

[0064] - Figure 3b is a flow chart showing steps of a wireless communication method supporting handover by a user equipment according to a particular embodiment,

[0065] - Figure 3c is a flowchart showing steps of a wireless communication method for performing a handover by a target base station according to a specific embodiment,

[0066] - Figure 4a is a combined flow chart and block diagram showing the main steps of a wireless communication method for performing a handover of a UE from a source base station to a target base station according to another embodiment,

[0067] - Figure 4bis a flow chart showing steps of a wireless communication method supporting handover by a user equipment according to a particular embodiment,

[0068] - Figure 4c is a flowchart showing steps of a wireless communication method for performing a handover by a target base station according to a specific embodiment,

[0069] - Figure 5 is a table showing a set of backoff delay values ​​according to an embodiment,

[0070] - Figure 6 is a flow chart showing steps of a wireless communication method supporting handover by a user equipment according to a particular embodiment,

[0071] - Figure 7 is an exemplary mapping table for associating QoS parameters with random access scheduling parameters according to an embodiment,

[0072] - Figure 8 is a block diagram depicting the architecture of a user equipment arranged to implement a wireless communication method for performing a handover according to an embodiment, and

[0073] - Fig. 9 is a block diagram depicting the architecture of a base station apparatus arranged to implement a wireless communication method for performing handover according to an embodiment. DETAILED DESCRIPTION

[0074] The specific embodiments described below with reference to the accompanying drawings are intended as descriptions of various configurations and are not intended to represent the only configuration in which the concepts described herein may be practiced. The specific embodiments include specific details to provide a thorough understanding of the various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In particular, although terminology from 3GPP 5G NR may be used in this disclosure to illustrate the embodiments of this document, this should not be viewed as limiting the scope of the invention. Moreover, it should be understood that although this disclosure is illustrated with respect to non-terrestrial base stations, this should not be viewed as limiting the scope of the invention, as the teachings of this disclosure may be applied to terrestrial base stations without modifying the invention.

[0075] Figure 1 An exemplary 5G New Radio (NR) wireless communication system 100 is shown according to an embodiment of the present disclosure, the system being configured to support handover procedures in a non-terrestrial network (NTN).

[0076] The wireless system 100 comprises at least a first NTN base station 101 and a second NTN base station 102. Figure 1In the examples, NTN base stations 101 and 102 are LEO satellites orbiting the earth with known / or predictable orbital parameters. However, it should be noted that base stations 101 and 102 can be any high altitude platform system (HAPS), including aircraft, balloons or airships, or even ground base stations. In some examples, NTN base stations 101 and 102 are 5G NR base stations (gNodeB or gNB).

[0077] Figure 1 Also shown are a first user equipment (UE) 105 and a second user equipment 106 that are initially served by the base station 101 in the source cell. The UE 105 and the UE 106 can be of any type. For example, the UE 105 can be a mobile phone, a connected vehicle, or an IoT device (Internet of Things). The UE 106 can also be a mobile phone, a connected vehicle, or an IoT device.

[0078] LEO satellites 101 and 102 travel along predictable orbits at a constant speed (e.g., 7.56 km / s) relative to the earth's surface, causing their respective radio beams 103 and 104 to move over time. Therefore, UE 105 and other UEs served in the same cell (e.g., UE 106) frequently switch to new target cells. Considering the large cell size of NTN, a large number of UEs may need to be switched at the same time.

[0079] Figure 2 is a call flow illustrating a conventional inter-cell handover procedure in the prior art. The UE periodically transmits measurement reports on signal quality in message 200. When the signal strength from the second gNB becomes greater than the signal strength from the first gNB, the first gNB makes a decision 201 to handover the UE and sends a handover request 202 to the second gNB via the inter-gNB Xn interface. The second gNB acknowledges the handover request in a message 204 transmitted to the first gNB after an admission check 203. The first gNB then sends a handover command 205 (i.e., an RRC reconfiguration message) to the UE to instruct the UE to handover to the second gNB.

[0080] Upon receiving the handover command 205, the UE synchronizes with the second gNB and performs a random access procedure 206 to establish a communication channel, and then sends a handover complete message 207 (i.e., an RRC reconfiguration complete message).

[0081] The UE initiates this random access procedure by randomly selecting a signature from a given set of signatures and by transmitting a so-called preamble containing the selected signature to the second gNB. This preamble is also called a "random access preamble".

[0082] Since different UEs can initiate a random access procedure on a common RACH channel at the same time, and since there are only a limited number of different signatures available for selection, different UEs may randomly select the same signature. If this happens, the unique identification of the respective UEs and the messages from or to the UEs during the synchronization process are hampered by so-called collisions. As a result, the random access procedure may fail, resulting in termination of the random access procedure and the UE has to repeat the random access procedure at a later time.

[0083] It is easy to understand that the risk of such a conflict occurring is particularly high when a large number of UEs are transferred from the source gNB to the target gNB at the same time.

[0084] For the sake of clarity, in the following description, like reference numerals will be used to refer to like entities.

[0085] Now refer to Figure 3a , Figure 3b and Figure 3c A first embodiment of a wireless communication method for performing handover is described.

[0086] Figure 3a A combined flow chart and block diagram illustrating main steps of a wireless communication method for performing a handover of a UE 105 from a first base station 101 to a second base station 102 according to an embodiment is shown.

[0087] The UE 105 sends a periodic or aperiodic report message 310 including an indication suitable for the serving gNB 101 to decide whether the UE 105 should be handed over to another gNB serving a neighboring cell. Basically, such a report may include the signal quality of the first gNB 101 and the signal quality of the second gNB 102 serving the neighboring cell. Such measurement reports are well known and are used by the first gNB 101 to trigger the handover during step 311 and will not be described in further detail.

[0088] Once the first gNB 101 has decided that the UE 105 should be switched to another gNB, the source gNB 101 may send a switching request message 312 to the second gNB 102.

[0089] In an embodiment, the handover request message 312 includes a priority associated with the UE 105 and / or a QoS profile associated with the UE 105. The UE 105 may obtain the priority and / or QoS profile from the first gNB 101 via MAC layer signaling (i.e., logical channel prioritization and / or 5QI signaling).

[0090] The second gNB 102 receives such a message 312 including the priority and / or QoS profile of the UE 105 during step 325. The message 312 may be a handover request message or any suitable message sent over the Xn interface.

[0091] During step 313, the second gNB 102 determines a UE-specific random access scheduling configuration based on the priority and / or QoS profile associated with the UE 105. The gNB 102 may determine a random access delay timer value for each UE and / or a backoff timer value for each UE based on a mapping table between UE priority or QoS profile and specific random access and / or backoff delays. In some embodiments, the highest priority and / or QoS value will be associated with a lower delay value in such a mapping table. According to an embodiment, the random access delay value and the backoff delay value may be selected from a set of delay values ​​defined by 3gpp, such as Figure 5 shown.

[0092] In some embodiments, the determined random access scheduling configuration includes at least a random access delay value determined based on the priority and / or QoS profile associated with the UE 105. Such a random access delay value is a waiting period that the UE 105 needs to observe before initiating an initial random access attempt to the second gNB 102.

[0093] In some embodiments, the determined random access scheduling configuration comprises at least a backoff delay value determined according to said priority and / or QoS profile associated with the UE 105. Such a backoff delay value is a waiting period that the UE 105 needs to observe before a new random access attempt can be made if the first attempt has failed.

[0094] At step 327, the second gNB 102 sends a switching confirmation message 314 to the first gNB 101, wherein the message includes at least a random access scheduling configuration determined for the UE 105.

[0095] gNB 101 forwards the random access scheduling configuration received from gNB 102 to UE 105 in a handover command message 315 (e.g., in an RRC reconfiguration message).

[0096] At step 316, UE 105 obtains the random access scheduling configuration transmitted by gNB 101 in message 315. If the random access scheduling configuration includes a random access delay timer value, UE 105 configures and starts a timer during step 317 to delay the random access procedure.

[0097] When the scheduled random access timer fires at step 318, the UE 105 initiates a random access procedure 319. Thus, the random access procedure is delayed for a period of time depending on the priority and / or QoS value associated with the UE 105.

[0098] Therefore, the contention risk can be reduced by spreading out the random access procedure.In addition, the random access procedure is delayed according to the priority and / or QoS profile of the UE to be handed over, while providing the best performance and response time for high priority UEs.

[0099] In some embodiments, the UE 105 may check at step 320 whether the random access procedure 319 has failed, for example, due to contention. When the initial random access 319 fails, the UE 105 may check during step 321 whether the received random access scheduling configuration includes a random access backoff value and obtain the set backoff value. The UE 105 may then schedule a new timer based on the backoff timer value at step 322. When the timer expires at step 323, the UE 105 may initiate a new random access attempt during step 324, thereby further reducing the risk of collision while maintaining a good quality of service for high priority UEs. The steps of checking whether the random access has failed and performing a subsequent RACH attempt after the timer scheduled with the backoff value expires may be repeated until the random access attempt is successful.

[0100] Now refer to Figure 4a , Figure 4b and Figure 4c A second embodiment of a wireless communication method for performing handover is described.

[0101] Figure 4a is a combined flow chart and block diagram illustrating the main steps of a wireless communication method for performing a handover of a UE 105 and a relay UE 106 from a first base station 101 to a second base station 102 according to another embodiment.

[0102] FIG4 shows a so-called relay UE 106 that is initially served by the gNB 101. The relay UE 106 aggregates the signaling of several "slave" or "sidelink" UEs (including UE 105) in order to reduce the signaling bandwidth overhead. The UE 105 may communicate with the relay UE 106 using ProSe sidelink communication. The sidelink communication may be provided by a V2X PC5, DSRC, WiFi, LoRa ZigBee, or Bluetooth communication interface. For clarity, in the example of FIG4 , the relay UE 106 handles only one slave UE 105. However, the relay UE 106 may act as a signaling relay for multiple slave UEs 105 for optimizing the handover signaling overhead.

[0103] During the preliminary step, UE 105 attaches to relay UE 106 using ProSe sidelink communication and sends its priority and QoS profile to relay UE 106 in message 409. UE 105 may obtain its priority and / or QoS profile from gNB 101 through MAC layer signaling (i.e., logical channel prioritization and / or 5QI signaling). Thus, relay UE 106 maintains a list of registered UEs including the priority and / or QoS profile associated with each of the attached UEs.

[0104] The relay UE 106 may send periodic or aperiodic report messages 410 including indications suitable for the gNB 101 to decide whether the relay UE 106 and the attached UE 105 should be handed over to another gNB serving a neighboring cell. Basically, such a report may include values ​​representing the signal quality of the gNB 101 and the signal quality of the gNB 102 serving the neighboring cell as perceived by the relay UE 106. Such measurement reports are well known and are used by the serving gNB 101 to trigger the handover during step 411 and will not be described in further detail.

[0105] The measurement report 410 sent by the relay UE 106 may include a list of UEs attached to the relay UE 106, and the priorities and QoS profiles associated with the attached UEs. In some implementations, the message 410 includes a list of UEs managed by the relay UE 106, each entry in the list including an identifier of the UE, a QoS profile of the UE, and a priority. Figure 4a In the example of , it is assumed that the priority of UE 105 is lower than the priority of UE 106.

[0106] In some embodiments, the relay UE 106 includes its own priority and / or QoS profile in the list transmitted in the measurement report 410. The relay UE 106 may obtain its priority and / or QoS profile from the gNB 101 through MAC layer signaling (i.e., logical channel prioritization).

[0107] The gNB 101 may make a handover decision during step 411. Once the gNB 101 has decided that the relay UE 106 should be handed over to another gNB, the gNB 101 sends a handover request message 412 to the second gNB 102.

[0108] In an embodiment, the handover request message 412 may include a list of managed UEs received from the relay UE 106, each entry in the list including an identifier of the UE, a QoS profile and / or a priority of the UE.

[0109] At step 426, the second gNB 102 receives the switching request message.

[0110] During step 413, the second gNB 102 may determine a specific random access scheduling configuration for each UE in the list received from the first gNB 101, the random access scheduling configuration being determined based on a priority and / or QoS profile associated with each UE.

[0111] In some embodiments, the random access scheduling configuration determined for a particular UE includes at least a random access delay value determined for the particular UE based on the priority and / or QoS profile associated with the UE. Such a random access delay value is a waiting period that the UE needs to observe before initiating an initial random access attempt to the target gNB 102.

[0112] In some embodiments, the random access scheduling configuration determined for a specific UE includes at least a backoff delay value determined according to its priority and / or QoS profile for the specific UE managed by the relay UE 106. Such a backoff delay value is a waiting period that the UE needs to observe before a new random access attempt can be made if the first attempt has failed.

[0113] The gNB 102 may determine the random access delay timer value for each UE and / or the backoff timer value for each UE according to a predefined time range, i.e., the UE associated with the highest priority and / or QoS value will be assigned to the lower limit of the time range, while the lowest priority and / or QoS value will be assigned to the upper limit of the time range. According to an embodiment, the random access delay value and the backoff delay value may be selected from a set of delay values ​​defined by 3gpp, such as Figure 5 shown.

[0114] Then, gNB 102 sends a handover confirmation message 414 to gNB 101 during step 428, the message including at least the random access scheduling configuration determined for the UE managed by relay UE 106 (e.g., UE 105 in the example of FIG. 4 ). Thus, each random access scheduling configuration may be associated in message 414 with an identifier of the UE for which the random access scheduling configuration was determined. In some embodiments, the identifier of the UE may be a C-RNTI.

[0115] The gNB 101 may forward the received random access scheduling configuration along with the corresponding UE identifier to the relay UE 106 in a handover command message 415 (e.g., in an RRC reconfiguration message).

[0116] Upon receiving the handover command message 415, the relay UE 106 may obtain the random access scheduling configuration list transmitted by the gNB 101 in the message 415, and assign the received random access scheduling configuration to the corresponding slave UE, for example in the handover upcoming message 416.

[0117] In an embodiment, the relay UE 106 may perform a step 417 of obtaining a random access scheduling configuration associated with its own identifier within the received message 415. If the random access scheduling configuration associated with the relay UE identifier includes a random access delay timer value, the relay UE 106 performs a step 418 of configuring and starting the timer. When the timer fires at step 419, the relay UE 106 initiates an initial random access procedure 420 to establish an uplink communication channel to the gNB 102. The random access procedure 420 is thus delayed from a time period that depends on the priority and / or QoS value associated with the relay UE 106.

[0118] During step 421, the UE 106 may check whether the initial random access procedure 420 is successful.

[0119] Whenever the initial random access 420 fails, the relay UE 106 may obtain a random access backoff value from the received message 415 during step 422 and schedule a new timer based on the backoff timer value during step 423. When the timer fires at step 425, the UE 106 may initiate a new random access attempt 425. The steps of checking whether random access has failed and performing a subsequent RACH attempt after the timer scheduled with the backoff value expires may be repeated until the random access attempt is successful.

[0120] Upon receiving the message 416 including its specific random access configuration, the UE 105 may also perform a step 417 of obtaining a random access scheduling configuration. The UE 105 may obtain the random access configuration from the received message 416. The UE 105 performs a step 418 of scheduling and starting a timer according to the received random access scheduling configuration, in particular according to a random access delay timer value included in the random access scheduling configuration.

[0121] exist Figure 4a In the depicted example, because UE 105 has a lower priority than UE 106, the random access delay value associated with UE 105 is longer than the timer value received by UE 106. Therefore, the random access timer configured by UE 105 fires after the timer configured by UE 106.

[0122] When the timer expires at step 419, the UE 105 may initiate an initial random access procedure 421 in order to synchronize with the target gNB 102. The random access procedure 421 is thus delayed for a period of time that depends on the priority and / or QoS value associated with the UE 105.

[0123] Since the timer configured by UE 105 fires after the timer configured by UE 106 due to the highest priority of UE 106, the random access procedure 421 triggered by UE 105 occurs after the random access procedure 420. Thus, contention is avoided.

[0124] Whenever the initial random access 421 fails, the UE 105 may obtain a random access backoff value from the received message 416 during step 422 and schedule a new timer based on the backoff timer value during step 423. When the timer fires at step 424, the UE 106 may initiate a new random access attempt 425.

[0125] Now refer to Figure 6 A third embodiment of the present disclosure is described.

[0126] This embodiment is different from the first embodiment and the second embodiment in that the random access scheduling configuration including the random access delay value and / or the random access backoff delay value can be obtained by the user equipment from a pre-configured embedded mapping instead of being received in a message sent by another entity.

[0127] According to the third embodiment, the user equipment 105 may receive QoS requirements from a network node during a preliminary step 600. For example, the UE 105 receives an RRC signaling message sent by the gNB 101, the RRC message including QoS parameters. The QoS parameters may be 5QI (5G QoS identifier). According to the 3GPP 5G NR standard, when the UE 105 makes a request for any type of service, the 5GNR network automatically allocates a 5QI identifier for each user service with the required QoS (quality of service), and changes the technical parameters of the 5G network to meet the requirements of each allocated 5QI.

[0128] The UE 105 obtains during step 601 the random access scheduling configuration by looking up the random access scheduling configuration associated with said received QoS parameters in a pre-configured lookup table.

[0129] In some embodiments, the obtained random access scheduling configuration includes at least a random access delay value. Such a random access delay value is a waiting period that the UE 105 needs to observe before initiating an initial random access attempt to the target gNB.

[0130] In some embodiments, the determined random access scheduling configuration includes at least a backoff delay value. Such a backoff delay value is a waiting period that the UE 105 needs to observe before a new random access attempt can be made if a previous attempt failed.

[0131] Figure 7 An exemplary lookup table is shown, in which a specific QoS parameter value is associated with a random access delay value and a random access backoff value. For example, a UE that has received a 5QI parameter P3 will obtain a random access scheduling configuration including a RD4 random access delay value and a BD4 random access backoff delay value.

[0132] Therefore, no additional signaling is required to obtain the random access scheduling configuration.

[0133] Upon receiving the handover command, the UE 105 configures and starts a timer according to the obtained random access delay value during step 602 to delay the random access procedure.

[0134] When the scheduled random access timer fires at step 603, the UE 105 initiates an initial random access procedure 604. Thus, the random access procedure is delayed from a time period depending on the priority and / or QoS value associated with the UE 105.

[0135] Therefore, the contention risk can be reduced by spreading the random access procedure out. In addition, the random access procedure is delayed according to the QoS parameters configured for the UE, thereby providing the best performance and response time for UEs with higher QoS requirements.

[0136] In some embodiments, the UE 105 may check at step 605 whether the random access procedure 604 has failed, for example, due to contention. When the initial random access 604 fails, the UE 105 may check during step 605 whether the received random access scheduling configuration includes a random access backoff value and obtain the set backoff value. The UE 105 may then schedule a new timer based on the backoff timer value at step 607. When the timer expires at step 608, the UE 105 may initiate a new random access attempt during step 609, thereby further reducing the risk of collision while maintaining a good quality of service for high QoS UEs. The steps of checking whether the random access has failed and performing a subsequent RACH attempt after the timer scheduled with the backoff value expires may be repeated until the random access attempt is successful.

[0137] Figure 8 A schematic architecture of an apparatus 800 suitable for implementing a wireless communication method for supporting handover by a user equipment according to an embodiment is shown.

[0138] The apparatus 800 comprises a processor 801 and a memory 802, such as a random access memory (RAM). The processor 801 may be controlled by a computer program 803 stored in the memory 802, the computer program comprising instructions configured to implement a wireless communication method for supporting handover according to a particular embodiment.

[0139] More specifically, the computer program 803 comprises instructions for implementing the following steps:

[0140] - obtaining a random access scheduling configuration of at least the user equipment, the configuration comprising at least a random access delay value,

[0141] - starting a timer configured according to the random access delay value upon receiving a handover command from the first base station, and

[0142] - triggering a delayed random access procedure to the second base station when the timer expires.

[0143] At initialization, the instructions of the computer program 803 may be loaded into the memory 802 before being executed by the processor 801. The processor 801 implements the steps of the method according to the instructions of the computer program 803.

[0144] The device 800 includes a wireless communication unit 804, such as a 3G, 4G, 5G, 5GNR, WiFi or WiMax transceiver, for exchanging messages with other devices. In particular, the communication unit 804 is configured to synchronize and exchange data with a base station (e.g., NodeB (NB), eNodeB (eNB) or gNodeB (gNB)) of a wireless access network.

[0145] The apparatus 800 further comprises a RACH scheduling unit 805 configured to obtain a random access scheduling configuration, the random access scheduling configuration comprising at least a specific random access delay value and / or a random access backoff delay value determined based on a priority and / or a QoS profile associated with the apparatus 800. The RACH scheduling module may be implemented by computing program instructions arranged to configure the communication unit 804 to enable reception of a message comprising the random access scheduling configuration, and to extract the random access delay value and / or the random access backoff value from the received message. According to an embodiment, the message comprising the random access scheduling configuration is received from a base station serving a cell in which the apparatus is located. According to another embodiment, the message comprising the random access scheduling configuration is received via a sidelink ProSe communication channel from a user equipment acting as a relay for the purpose of performing a group handover. According to another embodiment, the RACH scheduling module can be implemented by computing program instructions, which are arranged to configure the communication unit 804 to enable reception of messages including QoS parameters (e.g., 5QI parameters), and to look up a pre-configured mapping table to find a random access scheduling configuration associated with the received QoS parameters.

[0146] The apparatus 800 further comprises a timer module 806 configured to trigger a random access procedure when a certain time period expires. The timer module may be implemented by computer program instructions arranged to obtain a random access delay value from the scheduling unit 805, schedule a timer using the delay value, and command the RACH unit 807 to trigger a random access procedure when the scheduled timer expires.

[0147] In some embodiments, the apparatus 800 is included in a user device, a mobile terminal, an IoT device, or a vehicle.

[0148] Fig. 9 The schematic architecture of an apparatus 900 suitable for implementing a wireless communication method in which a base station performs handover according to an embodiment is shown.

[0149] The apparatus 900 comprises a processor 901 and a memory 902, such as a random access memory (RAM). The processor 901 may be controlled by a computer program 903 stored in the memory 902, the computer program comprising instructions configured to implement a wireless communication method for performing a handover according to a particular embodiment.

[0150] More specifically, the computer program 903 comprises instructions for implementing the following steps:

[0151] - receiving a handover request from the second base station, the handover request comprising at least one priority value and / or QoS profile associated with the at least one user equipment,

[0152] - determining a random access scheduling configuration according to the user equipment priority value and / or the QoS profile, the random access scheduling configuration comprising at least a random access delay value,

[0153] - Transmitting a handover response message including the determined random access scheduling configuration to the second base station.

[0154] At initialization, the instructions of the computer program 903 may be loaded into the memory 902 before being executed by the processor 901. The processor 901 implements the steps of the method according to the instructions of the computer program 903.

[0155] The device 900 includes a wireless communication unit 904, such as a 3G, 4G, 5G, 5GNR, WiFi or WiMax transceiver, for exchanging messages with other devices. In particular, the communication unit 804 is configured to synchronize and exchange data with a base station (e.g., NodeB (NB), eNodeB (eNB) or gNodeB (gNB)) of a wireless access network.

[0156] The communication unit 904 can be configured to receive at least one QoS profile and / or priority associated with a specific UE through computer program instructions. For example, the communication unit can be configured to receive a handover request message from a source base station, the handover request message including one or more identifiers of UEs served by the source base station, each of the identifiers being associated with a specific priority value and / or QoS profile.

[0157] The apparatus 900 further includes a random access scheduling configuration determining unit 905. The unit 905 can be configured by computer program instructions to obtain at least a received QoS profile and / or a priority associated with a specific UE identifier from the communication unit 904, and determine a random access scheduling configuration based on the QoS and / or priority, the random access scheduling configuration including at least a random access delay value and a random access backoff delay value. The configuration unit 905 can use a mapping table to determine a specific delay according to a specific QoS or priority value.

[0158] The communication unit 904 may be further configured by computer program instructions to transmit a message to the source base station, the message comprising at least one random access scheduling configuration associated with the corresponding UE identifier determined by the unit 904. In some examples, the transmitted message may be a handover confirmation message.

[0159] The apparatus 900 further comprises a random access unit 906 configured to support a delayed random access procedure initiated by the user equipment, the random access procedure being delayed according to the delay value determined by the determination unit 905 for the UE.

[0160] In some embodiments, the apparatus 900 is included in a cellular base station, such as a terrestrial or non-terrestrial NodeB, eNodeB, gNodeB.

Claims

1. A wireless communication method for supporting handover from a first base station to a second base station by a user equipment, the method comprising: obtaining (316) a random access scheduling configuration of at least the user equipment, the configuration comprising at least a random access delay value, upon receiving a handover command from the first base station, starting (317) a timer configured according to the random access delay value, When the timer expires (318), a delayed random access procedure to the second base station is triggered (319).

2. The method of claim 1, wherein: The random access scheduling configuration further comprises a random access backoff delay value, and the method comprises the step of applying the backoff delay value when the random access procedure fails.

3. The method according to claim 1 or 2, wherein: The random access scheduling configuration is obtained from a message including the random access scheduling configuration.

4. The method of claim 3, wherein: The message including the random access scheduling configuration is received from the first base station.

5. The method according to any one of claims 1 to 4, wherein: The random access scheduling configuration is determined by the second base station according to a QoS profile and / or priority associated with the user equipment.

6. The method according to claim 1 or 2, wherein: Obtaining the random access scheduling configuration includes: receiving an RRC signaling message including QoS parameters, The random access scheduling configuration associated with the received QoS parameters is searched in a pre-configured lookup table.

7. A user equipment for supporting handover from a first base station to a second base station, the user equipment comprising a processor (801), the processor coupled to a memory (802), the memory having computer program instructions (803) stored therein, wherein: The processor is configured by the computer program instructions (803) to: obtaining a random access scheduling configuration of at least the user equipment, wherein the configuration includes at least a random access delay value, upon receiving a handover command from the first base station, starting a timer configured according to the determined random access delay value, When the timer expires, a delayed random access procedure to the second base station is triggered.

8. A wireless communication method for performing handover of at least one user equipment from a second base station to the first base station by a first base station, the method comprising: receiving (325) a handover request from the second base station, the handover request comprising at least one priority value and / or QoS profile associated with the at least one user equipment, determining (313) a random access scheduling configuration according to the user equipment priority value and / or the QoS profile, the random access scheduling configuration comprising at least a random access delay value, A handover response message including the determined random access scheduling configuration is transmitted (327) to the second base station.

9. A base station for performing handover of at least one user equipment in a wireless network, the base station comprising a processor (901), the processor coupled to a memory (902), the memory having computer program instructions (903) stored therein, wherein: The processor is configured by the computer program instructions to implement a wireless communication method for performing a handover, the method comprising: receiving a handover request from the second base station, the handover request comprising at least one priority value and / or QoS profile associated with the at least one user equipment, determining a random access scheduling configuration according to the at least one user equipment priority value and / or the QoS profile, the random access scheduling configuration comprising at least a random access delay value, A handover response message including the determined random access scheduling configuration is transmitted to the second base station.

10. A wireless communication system for performing a handover of at least one first user equipment from a first base station to a second base station, the second base station comprising a processor (901), the processor coupled to a memory (902), the memory having computer program instructions (903) stored therein, wherein: The processor (901) is configured by the computer program instructions (903) to implement a wireless communication method for performing a handover, the method comprising: receiving (325) a handover request from the first base station, the handover request comprising at least one priority value and / or QoS profile associated with the at least one user equipment, determining (313) at least one random access scheduling configuration according to the at least one user equipment priority value and / or the QoS profile, the random access scheduling configuration comprising at least a random access delay value, transmitting (327) to the first base station a handover response message including the determined at least one random access scheduling configuration, and The at least one first user equipment comprises a processor (901), the processor is coupled to a memory (902), the memory stores computer program instructions (903), wherein the processor (901) is configured by the computer program instructions (903) to: receiving (316) at least one random access scheduling configuration, the at least one random access scheduling configuration comprising at least a random access delay value, starting (317) a timer configured according to the received random access delay value, When the timer expires (318), a delayed random access procedure to the second base station is triggered (319).

Images