Control of signaling during the X2 / Xn TNLA discovery process

Abstract

The UE reports the ECGI of the target eNB / gNB lacking an X2 / Xn interface to the source eNB / gNB. The source eNB / gNB sends a configuration transfer message to the network element to acquire the X2 / Xn TNLA interface TNLA of the target eNB / gNB. The source eNB / gNB starts an initial backoff timer and an exponential backoff multiplier. The source eNB / gNB determines whether the TNLA discovery procedure time is greater than or equal to the current backoff time, where the current backoff time is equal to the previous backoff period multiplied by the exponential backoff multiplier. The source eNB / gNB may resend the configuration transfer message to the network element when the previous TNLA discovery procedure time for the same ECGI is greater than or equal to the current backoff time, and may not resend the configuration transfer message to the network element when the previous TNLA discovery procedure time is less than the current backoff time.

Description

[Technical field]

[0001] This disclosure is the result of the X2 / Xn TNLA discovery process Signaling during Control About 。 [Background technology]

[0002] Generally, a wireless communication system includes a radio access network (RAN) and a core network (CN). The RAN includes several base stations each providing coverage serving a number of user equipment (UE) devices, such as mobile phones, tablet computers, laptop computers, built-in wireless modules, and other wireless equipped devices, whether operated by a user or not. The base stations may include a remote radio unit (RRU) and a baseband unit (BBU). The base stations or access points may be coupled with the CN via a communication link, commonly referred to as a backhaul link. The CN in virtually all wireless communication systems provides a connection to a fixed system, such as the public switched telephone network (PSTN) and / or the Internet.

[0003] Wireless communication services are provided by a particular operator in a particular location. These individual wireless networks are often referred to as cellular networks. A particular operator or cellular network may be referred to as a Public Land Mobile Network (PLMN). A PLMN is identified by a PLMN identity broadcast within System Information Block (SIB) 1 (SIB1), and the UE is responsible for the selection of the PLMN. A cell may belong to more than one PLMN, in which case SIB-1 may broadcast multiple PLMN identities.

[0004] Each cellular network may operate with a specific radio access protocol, such as Long Term Evolution (LTE) and New Radio (NR) or 5G wireless communication protocols. LTE networks and 5G networks share an all-Internet Protocol (IP) architecture. The network architectures of LTE networks and 5G networks differ in some respects. Many current LTE networks are being transitioned to 5G networks. A non-standalone (NSA) 5G architecture may include a 4G / LTE core implemented with 5G radios. A standalone (SA) 5G network is an end-to-end 5G network. In an LTE network, a base station may be referred to as an eNB, the eNBs may be interconnected via an X2 link, and the network may include a mobility management entity (MME) for managing UE access and mobility. In a 5G network, a base station may be referred to as a gNB, the gNBs may be interconnected via an Xn link, and may include an access and mobility management function (AMF) for handling connectivity and mobility management tasks.

[0005] Generally, each base station may provide a coverage area and define an air interface for carrying communications between the base station and the UE, including a downlink from the base station to the UE and an uplink from the UE to the base station. The air interface may occupy carriers, which may be frequency division duplex (FDD) with separate ranges of frequencies for downlink and uplink communications, or time division duplex (TDD) with a single range of frequencies multiplexed over time between downlink and uplink use.

[0006] Depending on the radio access protocol, the air interface may then define various resources and channels for carrying communications between the base station and the UE, including various control plane communications (e.g., operational control signaling) and user plane communications (e.g., bearer data such as application layer communications).

[0007] In the downlink, for example, the air interface may define a reference channel carrying a broadcast reference signal that the UE can measure to assess downlink coverage quality, as well as various other downlink control channels for carrying control signaling to the UE, and the air interface may define one or more traffic channels for carrying bearer data, etc. In the uplink, the air interface may define an access channel for carrying UE access requests to the base station, as well as various other uplink control channels for carrying control signaling to the base station, and the air interface may define one or more uplink traffic channels for carrying bearer data, etc. to the base station.

[0008] A UE in a connected state transmits and receives data packets over a wireless communication link with a source base station. The quality of the wireless signal between the UE and a base station in the network can change over time for a variety of reasons, including changes in the UE's location as the UE moves through a coverage area, base station loading, and signal fading.

[0009] The source base station monitors the quality of the signal connection between the UE and the source base station by sending a measurement control request message to the UE and receiving a measurement report message from the UE. Based on the measurement report criteria and threshold settings, the source base station may make a decision to handover the UE to the target base station. As part of the handover process, the UE sends a measurement report identifying the target base station. In some cases, the reported target base station may have a Physical Cell ID (PCI) that is unknown to the source base station. That is, the reported target base station is not in the source base station Neighbor Relation Table (NRT).

[0010] If the target base station (PCI) is not known by the source base station, the source base station sends a configuration forwarding message to the MME or AMF of the core network to discover the X2 / Xn transport network layer association (TNLA). If the MME / AMF cannot reach the target base station, it does not send a response to the configuration forwarding message and the source base station does not know the X2 / Xn TNLA address of the target base station.

[0011] The source base station continues to send configuration transfer messages until it knows the X2 / Xn TNLA address of the target base station, which results in unnecessary signaling storms to the core network. Summary of the Invention [Problem to be solved by the invention]

[0012] Therefore, there is a need for a solution to prevent unnecessary signaling storms towards the core network during the X2 / Xn TNLA discovery procedure when the target base station is not known. [Means for solving the problem]

[0013] In one general aspect, a method for reducing Transport Network Layer Association (TNLA) discovery procedure messages is provided. The method may include reporting, by a user equipment (UE), an extended cell global identifier (ECGI) of a target neighbor base station lacking an X2 or Xn interface TNLA, by a source base station, receiving, by a source base station, the ECGI of the target neighbor base station lacking an X2 or Xn interface TNLA, by the source base station, transmitting a configuration transfer message to a network element to obtain the X2 or Xn interface TNLA of the target neighbor base station, where a time between transmitting the configuration transfer message and waiting for the network element to transmit a network configuration transfer message in response to the configuration transfer message may comprise a TNLA discovery procedure time. The method may include starting an initial backoff timer and an exponential backoff multiplier, determining whether a time elapsed since a previous TNLA discovery procedure timestamp is greater than or equal to a current backoff time, where the current backoff time is equal to a previous backoff period multiplied by the exponential backoff multiplier. The method may also include, by the source base station, resending a configuration transfer message to the network element if the time elapsed since the previous TNLA discovery procedure time is greater than or equal to the current backoff time, and not sending the configuration transfer message to the network element if the time elapsed since the previous TNLA discovery procedure time is less than the current backoff time, performing an X2 or Xn setup between the source base station and the target base station if the network element configuration transfer message is received, and stopping the source base station from resending the configuration transfer message when a maximum backoff time is reached and the network element configuration transfer message is not received. Other embodiments of this aspect include corresponding computer systems, apparatus, and computer programs recorded on one or more computer storage devices, each configured to perform the operations of the method.

[0014] In another general aspect, a wireless communication system is provided that includes a target base station, a network element, a user equipment (UE) configured to report an extended cell global identifier (ECGI) of the target base station lacking an X2 or Xn interface transport network layer association (TNLA), and receive the ECGI of the target base station reported by the UE and send a configuration transfer message to the network element as a request for an X2 or Xn interface TNLA of the target base station, start an initial backoff timer and start an exponential backoff multiplier, and determine whether a time elapsed since a previous TNLA discovery procedure timestamp is greater than or equal to a current backoff time, where the current backoff time is multiplied by the exponential backoff multiplier. the TNLA discovery procedure time is equal to a previous back-off period set in the network element, the TNLA discovery procedure time being the time between sending a configuration transfer message and receiving a network configuration transfer message from the network element, resending the configuration transfer message to the network element if the time elapsed since the previous TNLA discovery procedure time is equal to or greater than the current back-off time, not sending the configuration transfer message to the network element if the time elapsed since the previous TNLA discovery procedure time is less than the current back-off time, performing an X2 or Xn setup with the target base station if the network element configuration transfer message is received, and stopping resending the configuration transfer message when a maximum back-off time is reached and no network element configuration transfer message is received. Other embodiments of this aspect include corresponding computer systems, apparatus, and computer programs recorded on one or more computer storage devices, each configured to perform the operations of the method.

[0015] In yet another general aspect, a non-transitory computer-readable medium having stored thereon instructions for causing a processing circuit to perform a process, the process including reporting, by a user equipment (UE), an extended cell global identifier (ECGI) of a target neighbor base station lacking an X2 or Xn interface TNLA, by a source base station, receiving, by the source base station, the ECGI of the target neighbor base station lacking an X2 or Xn interface TNLA, transmitting, by the source base station to a network element, a configuration transfer message to obtain the X2 or Xn interface TNLA of the target neighbor base station, where a time between transmitting the configuration transfer message and waiting for the network element to transmit a network configuration transfer message in response to the configuration transfer message may include a TNLA discovery procedure time, starting an initial backoff timer, and transmitting an exponential backoff timer. starting a multiplier, determining if a TNLA discovery procedure timestamp is greater than or equal to a current backoff time, where the current backoff time is equal to a previous backoff period multiplied by an exponential backoff multiplier, resending a configuration transfer message by the source base station to the network element if the time elapsed since the previous TNLA discovery procedure time is greater than or equal to the current backoff time, and not sending the configuration transfer message to the network element if the time elapsed since the previous TNLA discovery procedure time is less than the current backoff time, performing an X2 or Xn setup between the source base station and the target base station if the network element configuration transfer message is received, and stopping the source base station from resending the configuration transfer message when a maximum backoff time is reached and no network element configuration transfer message is received. Other embodiments of this aspect include corresponding computer systems, apparatus, and computer programs recorded on one or more computer storage devices, each configured to perform the operations of the method. [Brief description of the drawings]

[0016] [Figure 1] FIG. 2 illustrates a communication link between a mobile device and a base station according to an exemplary embodiment. [Figure 2A] A signaling diagram of the X2 TNLA discovery process during handover is shown. [Figure 2B] 1 illustrates a signaling diagram of an X2 TNLA discovery process according to some embodiments. [Diagram 3] 1 illustrates a signaling diagram of the Xn TNLA discovery process according to some embodiments. [Figure 4] 1 is a flowchart of an example process for controlling an X2 / Xn TNLA discovery process, according to some embodiments. [Diagram 5] 13 is a flowchart of an additional implementation for controlling the X2 / Xn TNLA discovery process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] FIG. 1 illustrates a communication link between a mobile device and a source base station before handover and a communication link between a mobile device and a target base station after handover. The base station may be an eNB or a gNB. As shown in FIG. 1, a source base station 102 has a bidirectional wireless connection with a UE 106. A signal 108' may be referred to as a downlink (DL) signal, and a signal 110' may be referred to as an uplink (UL) signal. The mobile device 106 receives a signal 108' from the source base station 102 and transmits a signal 110' to the source base station 102.

[0018] When the source base station 102 determines that the UE 104 should be handed over to the target base station 104, the source base station 102 attempts to establish an X2 / Xn connection with the target base station 104. The X2 / Xn handover procedure is performed without going through the packet core network, i.e., corresponding messages are exchanged between the source base station and the target base station. When the target base station is known to the source base station, a direct X2 / Xn transport link 112 is established between the source base station and the target base station.

[0019] Once the handover process is completed, downlink 108 ′ and uplink 110 ′ signals are established between the UE 106 and the target base station 110 ′, and the downlink 108 ′ and uplink 110 ′ resources are released from the source base station 102 .

[0020] 2A shows a condensed handover signaling diagram recalling the X2 TNLA discovery process. The UE 204 sends a measurement report 210 to the S-eNB 202. The measurement report 210 includes the signal strength of the S-eNB 202, the signal strength of the radio signal of the T-eNB 208, and the Physical Cell Identifier (PCI) of the T-eNB 208. At 212, the case is shown where the PCI of the T-eNB 208 is not known to the S-eNB 202. The S-eNB 202 sends an Extended Cell Global Identifier (ECGI) Request message 214 to the UE 204, which responds by sending a measurement report with the ECGI information 216 of the T-eNB 208. At 218, the S-eNB 202 updates its Neighbor Relation Table (NRT). Although not shown, the S-eNB may send a new neighbor discovery notification to the network element and receive a configuration update for the new neighbor base station (T-eNB 208), which may allow the S-eNB to update the NRT at 218.

[0021] At 220, the S-eNB 202 checks X2 availability for the reported neighbor (T-eNB 208). For each ECGI for which the S-eNB 204 does not have an X2 Transport Network Layer Association (TNLA) connection, the S-eNB sends an eNB Configuration Transfer message 222 to the Mobility Management Entity (MME) 206 to obtain the TNLA of the new neighbor (T-eNB 208). The MME 206 then sends an MME Configuration Transfer message 224 to the T-eNB 208 to obtain the TNLA. If the MME 206 is successful in obtaining the TNLA of the T-eNB 208, the T-eNB 208 responds by sending TNLA details 226 to the MME 206. The MME 206 then sends the TNLA information 228 to the S-eNB 202. At 230, the S-eNB 202 updates its X2 list. The S-eNB 202 then sends an X2 Setup Request / eNB Configuration Update message 232 to the T-eNB 208 to initiate the handover process.

[0022] 2B is a handover signal diagram recalling the X2 TNLA discovery process according to an example embodiment. 3GPP TS36.423, incorporated herein by reference, describes the X2 application protocol and associated signaling. The RAN of a wireless communication system may be dynamically reconfigured for system requirements. Thus, base stations, access points, etc. may be added to the network and / or moved within the network's wireless coverage area to accommodate network requirements. As a result, situations arise where the network may not be able to identify new neighboring or target base stations.

[0023] In Figure 2B, the signaling and process from 210 to 220 are the same as described in Figure 2A. At 234, the S-eNB determines the PLMN of the reported neighbor T-eNB 208. If the T-eNB 208 belongs to a different PLMN than the S-eNB's PLMN / operator or is otherwise not available in the S-eNB's PLMN network, the PLMN is blacklisted. The X2 establishment procedure will not be attempted for a neighbor / target with a blacklisted PLMN. In the case of a blacklisted PLMN, the neighbor / target is added to the NRT and handover should be performed via S1 only.

[0024] For all non-blacklisted PLMNs, the S-eNB sends an eNB configuration transfer message 222 to the mobility management entity (MME) 206 to acquire the TNLA of the new neighbor (T-eNB 208). As shown in FIG. 2A, if the MME 206 is successful in acquiring the TNLA of the T-eNB 208, the T-eNB 208 responds by sending TNLA details 226 to the MME 206, which then sends an MME configuration transfer message 224 to the T-eNB 208 to acquire the TNLA. However, as discussed above, the T-eNB 208 may be unknown or otherwise unreachable and the MME 206 does not receive a timely response from the T-eNB 208. That is, the MME 206 does not receive the TNLA details 226. Therefore, since the MME 206 has not received the TNLA details 226 from the T-eNB 202, the MME 206 cannot send the TNLA information 228 to the S-eNB 206.

[0025] If the S-eNB cannot receive TNLA information 228 from the MME 206, the S-eNB 202 continues to send eNB configuration transfer messages 222 to the MME 206 to discover the X2 TNLA of the T-eNB 208. As a result, an X2 signaling storm may be generated as the S-eNB 202 continues to send eNB configuration transfer messages 222 to the MME 206 to learn the X2 TNLA of the T-eNB 208 while the T-eNB is not known or reachable.

[0026] To avoid X2 signaling storms and reduce the number of X2 messages in the X2 TNLA discovery process, an initial back-off timer may be started at 236. The initial back-off timer 236 applies to an eNB configuration transfer message 222 when a previous eNB configuration transfer message 222 for the same ECGI is not resolved; i.e., there is no response (226) from the MME 206. The initial back-off timer 236 is configurable. The initial back-off timer 236 may be configured with an initial value, for example, from 5 seconds to 600 seconds or more in five steps. Thus, when the S-eNB 202 sends an eNB configuration transfer message 222 and fails to receive a response, the S-eNB does not retransmit the eNB configuration transfer message 222 before the expiration of the configured value of the initial back-off timer 236. However, the S-eNB 202 continues to retransmit the configuration transfer message 222 until it receives a response from the MME 206. For example, if the initial backoff timer is set to 30 seconds, the S-eNB 202 continues to resend the configuration transfer message 222 every 30 seconds until a response is received from the MME 206.

[0027] In addition, an exponential backoff multiplier 238 may be implemented. The exponential backoff multiplier is a factor that is multiplied with the previous backoff period to successively cause an exponential backoff period. The exponential backoff multiplier 238 may be configurable. For example, the exponential backoff multiplier 238 may be configured with a value of 4. Considering the previous example where the initial backoff timer is configured with a value of 30 seconds, after an initial backoff of 30 seconds, the next backoff period will be 120 seconds (30×4). If there is no response from the MME 206, the S-eNB 202 resends the eNB configuration transfer message 222 after 120 seconds. If no response is received from the MME 206 for the same ECGI, the S-eNB 202 resends the eNB configuration transfer message 222 after 480 seconds (120×4). If no response is received, the next eNB configuration transfer message 222 for the same ECGI is sent after 1,920 seconds, and so on. Therefore, implementing the initial backoff timer 236 and the exponential backoff timer 238 significantly reduces the signaling overhead in the X2 TNLA discovery process. The exponential backoff timer 238 may be configured with a maximum backoff value, which is a configurable value. The value may be set from 60 seconds to 3600 seconds or more.

[0028] When a wireless communication network is dynamically changed, new eNBs and / or T-eNBs may be unknown to the network elements. By implementing the technique described in FIG. 2B, the X2 signaling overhead can be significantly reduced for any new eNB or T-eNB that is unknown. When the new eNB or T-eNB 208 responds to the MME Configuration Transfer message 224 with the TNLA details at 226, the MME 206 responds to the S-eNB 202 with the TNLA information 228. At 230, the S-eNB 202 updates its X2 list. The S-eNB 202 then sends an X2 Setup Request / eNB Configuration Update message 232 to the T-eNB 208 to initiate the handover process.

[0029] 3 shows an Xn TNLA discovery process according to an exemplary embodiment. The Xn TNLA discovery process is similar to the X2 TNLA discovery process. However, the Xn TNLA discovery process may be applicable to a 5G network, while the X2 TNLA discovery process may be applicable to an LTE network.

[0030] In FIG. 3, the signaling and process from 310 to 320 are the same as described in FIG. 2B. The UE 304 sends a measurement report 310 to the S-gNB 302. The measurement report 310 includes the signal strength of the S-gNB 302, the signal strength of the radio signal of the T-gNB 308, and the physical cell identifier (PCI) of the T-gNB 308. At 312, the case is shown where the PCI of the T-gNB 308 is not known to the S-gNB 302. The S-gNB 302 sends an Extended Cell Global Identifier (ECGI) Request message 314 to the UE 304, which responds by sending a measurement report with the ECGI information 316 of the T-gNB 308. At 318, the S-gNB 202 updates its Neighbor Relation Table (NRT). Although not shown, the S-gNB 304 may send a new neighbor discovery notification to the network element and receive a configuration update for the new neighbor base station (T-gNB 308), which allows the S-gNB to update the NRT at 318. At 320, the S-gNB 302 checks Xn availability for the reported neighbor (T-gNB 308). For each ECGI for which the S-gNB 304 does not have an Xn Transport Network Layer Association (TNLA) connection, the S-gNB 304 sends an uplink RAN ​​Configuration Transfer message 322 to the Access and Mobility Function (AMF) 306 to obtain the TNLA of the new neighbor (T-gNB 308).

[0031] The AMF 306 then sends a Downlink RAN ​​Configuration Transfer message 324 to the T-gNB 308 to acquire the TNLA. If the AMF 306 is successful in acquiring the TNLA for the T-gNB 308, the T-gNB 208 responds by sending TNLA details 326 to the AMF 306. The AMF 306 then sends the TNLA information 322 to the S-gNB 302. At 330, the S-gNB 302 updates its Xn list. The S-gNB 302 then sends an Xn Setup Request / gNB Configuration Update message 332 to the T-gNB 308 to initiate the handover process.

[0032] At 334, the S-gNB 304 determines the PLMN of the reported neighbor T-gNB 308. If the T-gNB 308 belongs to a different PLMN than the PLMN / operator of the S-gNB 304 or is otherwise not available in the PLMN network of the S-gNB 304, the PLMN is blacklisted. The Xn establishment procedure will not be attempted for a neighbor / target gNB with a blacklisted PLMN. In the case of a blacklisted PLMN, the neighbor / target gNB is added to the NRT and handover should be performed via S1 only.

[0033] For all non-blacklisted PLMNs, the S-gNB 304 sends an uplink RAN ​​configuration transfer message 322 to the AMF 306 to acquire the TNLA of the new neighbor (T-gNB 308). As mentioned above, if the AMF 306 is successful in acquiring the TNLA of the T-gNB 308, the T-gNB 308 responds by sending TNLA details 326 to the AMF 306, which then sends a downlink configuration transfer message 322 to the T-gNB 308 to acquire the TNLA.

[0034] However, the T-gNB 308 may be unknown or otherwise unreachable, and the AMF 306 does not receive a timely response from the T-gNB 308. That is, the AMF 306 does not receive the TNLA details 326. Thus, since the AMF 306 has not received the TNLA details 326 from the T-gNB 302, the AMF 306 cannot send the TNLA information 328 to the S-gNB 306.

[0035] If the S-gNB 302 cannot receive the TNLA information 328 from the AMF 306, the S-gNB 302 continues to send the uplink RAN ​​configuration transfer message 322 to the AMF 306. As a result, an Xn signaling storm may be generated because the S-gNB 302 continues to send the uplink RAN ​​configuration transfer message 322 to the AMF 306 to learn the Xn TNLA of the T-gNB 308 while the T-gNB 308 is not known or reachable.

[0036] To avoid Xn signaling storms and reduce the number of Xn messages in the Xn TNLA discovery process, an initial back-off timer may be started at 336. The initial back-off timer 336 applies to an uplink RAN ​​configuration transfer message 322 when a previous uplink RAN ​​configuration transfer message 322 for the same ECGI is not resolved; i.e., there is no response (326) from the AMF 306. The initial back-off timer 336 is configurable. The initial back-off timer 336 may be configured with an initial value, for example, from 5 seconds to 600 seconds or more in five steps. Thus, when the S-gNB 302 transmits an uplink RAN ​​configuration transfer message 322 and fails to receive a response, the S-gNB 302 does not retransmit the uplink RAN ​​configuration transfer message 322 before the expiration of the configured value of the initial back-off timer 336. However, the S-gNB 302 continues to retransmit the uplink RAN ​​configuration transfer message 322 until it receives a response from the AMF 306. For example, if the initial backoff timer is set to 30 seconds, the S-gNB 302 continues to resend the uplink RAN ​​configuration transfer message 322 every 30 seconds until a response is received from the AMF 306.

[0037] In addition, an exponential backoff multiplier 338 may be implemented. The exponential backoff multiplier is a factor that is multiplied with the previous backoff period to successively cause an exponential backoff period. The exponential backoff multiplier 338 may be configurable. For example, the exponential backoff multiplier 338 may be configured with a value of 4. Considering the above example with an initial backoff timer with a value of 30 seconds, after an initial backoff of 30 seconds, the next backoff period will be 120 seconds (30×4). If no response is received from the AMF 306, the S-gNB 302 resends the uplink RAN ​​configuration transfer message 322 after 120 seconds. If no response is received from the AMF 306 for the same ECGI, the S-gNB 302 resends the uplink RAN ​​configuration transfer message 322 after 480 seconds (120×4). If no response is received, the next uplink RAN ​​configuration transfer message 322 for the same ECGI is sent after 1,920 seconds, and so on. Therefore, implementing the initial backoff timer 336 and the exponential backoff timer 338 significantly reduces the signaling overhead in the Xn TNLA discovery process. The exponential backoff timer 338 may be configured with a maximum backoff value, which is a configurable value. The value may be set from 60 seconds to 3600 seconds or more.

[0038] When the wireless communication network is dynamically changed, the new gNB and / or T-gNB may be unknown to the network elements. By implementing the technique described in FIG. 3, the Xn signaling overhead can be significantly reduced for any new gNB or T-gNB that is unknown. When the new gNB or T-gNB 308 responds to the downlink RAN ​​configuration message with the TNLA details at 326, the AMF 306 responds to the S-gNB 302 with the TNLA information 328. At 330, the S-gNB 302 updates its Xn list. The S-gNB 302 then sends an Xn Setup Request / gNB Configuration Update message 332 to the T-eNB 208 to initiate the handover process.

[0039] FIG. 4 is a flow chart of an example process for controlling an X2 or Xn TNLA discovery process. As illustrated in FIG. 4, process 400 may include, at block 402, reporting, by a user equipment (UE), an extended cell global identifier (ECGI) of a target neighbor base station lacking an X2 / Xn interface TNLA. For example, the UE may report, as previously described, to a source base station, an extended cell global identifier (ECGI) of a target neighbor base station lacking an X2 / Xn interface TNLA. As shown at block 404, process 400 may include receiving, by the source base station, an ECGI of a target neighbor base station lacking an X2 / Xn interface TNLA. For example, the source base station may receive, as previously described, an ECGI of a target neighbor base station lacking an X2 / Xn interface TNLA. As further shown in FIG. 4, at block 406, the process 400 may include sending, by the source base station, a configuration transfer message to a network element to obtain the X2 / Xn TNLA of the target neighbor base station, where the time between sending the configuration transfer message and waiting for the network element to send a network configuration transfer message in response to the configuration transfer message comprises a TNLA discovery procedure time. For example, the TNLA discovery procedure may be initiated by the source base station sending a configuration transfer message to a network element to discover the X2 / Xn TNLA of the target neighbor base station, where the time between sending the configuration transfer message and waiting for the network element to send a network configuration transfer message in response may be referred to as the TNLA discovery procedure time. As further shown in FIG. 4, at 408, the process 400 may include starting an initial back-off timer and at 410, starting an exponential back-off multiplier. For example, the source base station may start the initial back-off timer after sending the configuration transfer message. While waiting for a response, the source base station does not resend the configuration transfer message until the initial back-off timer expires. The source base station also implements the exponential back-off multiplier.

[0040] 4, at 412, process 400 may include determining whether a time elapsed since a previous TNLA discovery procedure timestamp is greater than or equal to a current backoff time, where the current backoff time is equal to a previous backoff period multiplied by an exponential backoff multiplier. For example, the source base station may determine whether a TNLA discovery procedure time is greater than or equal to a current backoff time, where the current backoff time is equal to a previous backoff period multiplied by an exponential backoff multiplier.

[0041] 4, at 414, the process 400 may include resending a configuration transfer message by the source base station to the network element if the time elapsed since the previous TNLA discovery procedure time is equal to or greater than the current backoff time, and not resending the configuration transfer message to the network element if the time elapsed since the previous TNLA discovery procedure time is less than the current backoff time. That is, the source base station may resend the configuration transfer message to the network element if the time elapsed since the previous TNLA discovery procedure time is equal to or greater than the current backoff time. By implementing an exponential backoff multiplier, the current backoff time is increased exponentially.

[0042] As described with reference to FIG. 2B, the initial back-off timer applies to a configuration transfer message when a previous configuration transfer message for the same ECGI is not resolved; i.e., there is no response from the network element. The initial back-off timer 236 is configurable. Thus, when the source base station sends a configuration transfer message to a network element and fails to receive a response from the network element, the source base station does not resend the configuration transfer message before the expiration of the value of the initial back-off timer. However, the source base station continues to resend the configuration transfer message until it receives a response from the network element. For example, if the initial back-off timer is set to 30 seconds, the source base station continues to resend the configuration transfer message every 30 seconds until it receives a response from the network element.

[0043] An exponential backoff multiplier may be implemented to reduce X2 / Xn signaling toward a network where the target base station is unknown or otherwise unreachable. The exponential backoff multiplier is a factor that is multiplied with the previous backoff period to successively cause the exponential backoff period. For example. Consider an example with an initial backoff timer with a value of 30 seconds and an exponential backoff multiplier configured with a value of 4, after an initial backoff of 30 seconds, the next backoff period will be 120 seconds (4×30). If there is no response from the network element, the source base station resends the configuration transfer message after 120 seconds. If no response is received from the network element for the same ECGI, the source base station resends the configuration transfer message after 480 seconds (120×4). If no response is received, the next configuration transfer message for the same ECGI is sent after 1,920 seconds (480×4), and so on. Thus, implementing the initial backoff timer and the exponential backoff timer significantly reduces the signaling overhead in the X2 / Xn TNLA discovery process. The exponential backoff timer may also be configured with a maximum backoff value. This is a configurable value. The value may be set from 60 seconds to 3600 seconds or more.

[0044] 4, at 416, process 400 may include performing an X2 or Xn setup between the source base station and the target base station if a network element configuration forward message is received. For example, the source base station may perform an X2 / Xn setup with the target base station upon receiving the network element configuration forward message to establish an X2 / Xn connection with the target base station. That is, when the network finally receives a response from the target base station and transmits the TNLA information of the target base station to the source base station after 30 seconds, 60 seconds, an hour, or however long it takes, the source base station may perform an X2 / Xn TNLA setup and establish an X2 / Xn TNLA connection with the target base station.

[0045] 4, at 418, the process 400 may include the source base station stopping resending the configuration transfer message when a maximum backoff time is reached and the network element configuration transfer message is not received. That is, the source base continues to resend the configuration transfer message until the maximum backoff time is reached. When the maximum backoff time is reached, the source base station stops sending the configuration transfer message.

[0046] Process 400 may include additional implementations, such as any single implementation or any combination of implementations, in conjunction with one or more other processes described below and / or elsewhere herein. In a first implementation, the network element sends a network configuration transfer message after the network element discovers the identity of the target neighbor base station.

[0047] 5 is a flowchart of an additional implementation for controlling an X2 / Xn TNLA discovery process. In some implementations, one or more process blocks of FIG. 5 may be performed by a single device.

[0048] In a first implementation, at 502, the network element may send a network configuration transfer message only after the network element discovers identification information for a target neighbor base station.

[0049] In a second implementation, alone or in combination with the first implementation, an exponential backoff multiplier starts with an initially configured backoff period and then increases the backoff period by a factor multiplied with the previous backoff period, at 504. The exponential backoff multiplier may be configured with a maximum backoff time. The initial backoff timer, the exponential backoff timer, and the maximum backoff timer may be configurable.

[0050] In a third implementation, alone or in combination with the first and second implementations, at 506, the process 500 may include determining whether the ECGI is from the same public land mobile network (PLMN) or from a blocked PLMN, and may initiate a configuration transfer procedure only for ECGIs that are from the same PLMN or from a non-blocked PLMN.

[0051] In a fourth implementation, alone or in combination with one or more of the first to third implementations, at 508, the source base station is an S-eNB, the target neighboring base station is a T-eNB, the network element is a mobility management entity (MME), and an X2 interface is implemented.

[0052] In a fifth implementation, alone or in combination with one or more of the first to fourth implementations, at 510, the configuration transfer message is an eNB configuration transfer message and the network element configuration transfer message is an MME configuration transfer message.

[0053] In a sixth implementation, alone or in combination with one or more of the first to third implementations, at 512, the source base station is an S-gNB, the target neighboring base station is a T-gNB, the network element is an access and mobility management function (AMF), and an Xn interface is implemented.

[0054] In a seventh implementation, alone or in combination with one or more of the first to fourth and sixth implementations, at 514, the configuration transfer message is an uplink Radio Access Network (RAN) configuration transfer message and the network element configuration transfer message is a downlink RAN ​​configuration transfer message.

[0055] Although Figure 5 illustrates example blocks of process 500, in some implementations, process 500 may include additional, fewer, different, or differently arranged blocks than those illustrated in Figure 5. Additionally or alternatively, two or more of the blocks of process 500 may be performed in parallel.

[0056] Implementations may include one or more of the following features: A method in which the network element sends a network configuration transfer message after the network element discovers an identity of a target neighbor base station; A method in which an exponential backoff multiplier starts with an initially configured backoff period and then increases the backoff period by a factor multiplied with a previous backoff period, and the exponential backoff multiplier is configured with a maximum backoff time; A method in which the initial backoff timer, the exponential backoff multiplier, and the maximum backoff time are configurable; The method may include determining whether the ECGIs are from the same public land mobile network (PLMN) or from a blocked PLMN, and initiating a configuration transfer procedure for the ECGIs that are from the same PLMN or from a non-blocked PLMN; A method in which the source base station is an S-eNB, the target neighbor base station is a T-eNB, the network element is a mobility management entity (MME), and an X2 interface is implemented; A method in which the configuration transfer message is an eNB configuration transfer message and the network element configuration transfer message is an MME configuration message. The method, in which the source base station is an S-gNB, the target neighbor base station is a T-gNB, the network element is an Access and Mobility Management Function (AMF), and an Xn interface is implemented. The method, in which the configuration transfer message is an uplink Radio Access Network (RAN) configuration transfer message, and the network element configuration transfer message is a downlink RAN ​​configuration transfer message. Implementations of the described techniques may include hardware, methods or processes, or computer tangible media.

[0057] Implementations may also include one or more of the following features. A wireless communication system in which a network element sends a network configuration transfer message after the network element discovers an identity of a target base station. A wireless communication system in which an exponential backoff multiplier starts with an initial configured backoff period and then increases the backoff period by a factor multiplied with a previous backoff period. A wireless communication system in which an initial backoff timer, an exponential backoff multiplier, and a maximum backoff time are configurable. A wireless communication system in which a source base station is further configured to determine whether an ECGI is from the same public land mobile network (PLMN) or from a blocked PLMN and initiate a configuration transfer procedure only for ECGIs that are from the same PLMN or from a non-blocked PLMN. A wireless communication system in which a source base station is an S-eNB, a target base station is a T-eNB, a network element is a mobility management entity (MME), and an X2 interface is implemented. A wireless communication system in which a configuration transfer message is an eNB configuration transfer message and a network element configuration transfer message is an MME configuration message. A wireless communication system in which a source base station is an S-gNB, a target base station is a T-gNB, a network element is an Access and Mobility Management Function (AMF), and an Xn interface is implemented. The wireless communication system in which the configuration transfer message is an uplink Radio Access Network (RAN) configuration transfer message and the network element configuration transfer message is a downlink RAN ​​configuration transfer message. Implementations of the described techniques may include hardware, a method or process, or a computer tangible medium.

[0058] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the recited features, from a study of the drawings, the disclosure, and the appended claims.

[0059] In the claims, the word "comprising" does not exclude other elements or steps and the indefinite article "a" or "an" does not exclude a plurality.

[0060] A single processor, device or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0061] Operations such as acquiring, accessing, analyzing, capturing, comparing, determining, inputting, obtaining, outputting, providing, storing or storing, calculating, simulating, receiving, alerting, and stopping may be implemented as program code means of a computer program and / or as dedicated hardware.

[0062] The computer program may be stored and / or distributed on a suitable medium, such as an optical storage medium or a solid-state medium, supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunications systems.

Claims

1. A method for optimizing a Transport Network Layer Association (TNLA) discovery procedure message, the method comprising: reporting, by a user equipment (UE), an Extended Cell Global Identifier (ECGI) of a target neighboring base station lacking an X2 or Xn interface TNLA at a source base station; receiving, by the source base station, the ECGI of the target neighboring base station lacking the X2 or Xn interface TNLA; initiating a TNLA discovery procedure by transmitting, by the source base station, a configuration transfer message to a network element to obtain the X2 or Xn interface TNLA of the target neighboring base station, wherein the time between the step of transmitting the configuration transfer message and the step of waiting for the network element to transmit a network configuration transfer message in response to the configuration transfer message includes a TNLA discovery procedure time; starting an initial backoff timer; starting an exponential backoff multiplier; determining whether a time elapsed from a previous TNLA discovery procedure timestamp is greater than or equal to a current backoff time, wherein the current backoff time is equal to a previous backoff period multiplied by the exponential backoff multiplier; if the time elapsed from the previous TNLA discovery procedure time is greater than or equal to the current backoff time, retransmitting, by the source base station, the configuration transfer message to the network element, and if the time elapsed from the previous TNLA discovery procedure time is less than the current backoff time, not transmitting the configuration transfer message to the network element; if the network element configuration transfer message is received, performing an X2 or Xn setup between the source base station and the target neighboring base station; including stopping, by the source base station, retransmitting the configuration transfer message when a maximum backoff time is reached and the network element configuration transfer message is no longer received. A method.

2. The method according to claim 1, wherein the network element transmits the network configuration transfer message after discovering the identification information of the target neighboring base station.

3. The exponential backoff multiplier starts with the initially configured backoff period, and then increases the initially configured backoff period by a factor multiplied by the previous backoff period, and the exponential backoff multiplier is configured with a maximum backoff time, according to the method of claim 1.

4. The method according to claim 3, wherein the initial backoff timer, the exponential backoff multiplier, and the maximum backoff time are configurable.

5. The method according to claim 1, further comprising determining whether the ECGI is from the same public land mobile network (PLMN) or from a blocked PLMN, and starting a configuration transfer procedure for an ECGI that is from the same PLMN or from an unblocked PLMN.

6. The method according to claim 5, wherein the source base station is an S-eNB, the target neighboring base station is a T-eNB, the network element is a mobility management entity (MME), and the X2 interface is implemented.

7. The method according to claim 6, wherein the configuration transfer message is an eNB configuration transfer message and the network element configuration transfer message is an MME configuration transfer message.

8. The method according to claim 5, wherein the source base station is an S-gNB, the target neighboring base station is a T-gNB, the network element is an access and mobility management function (AMF), and the Xn interface is implemented.

9. The method according to claim 8, wherein the configuration transfer message is an uplink radio access network (RAN) configuration transfer message and the network element configuration transfer message is a downlink RAN configuration transfer message.

10. A wireless communication system, comprising a target base station, a network element, A user equipment (UE) configured to report an extended cell global identifier (ECGI) of a target base station lacking an X2 or Xn interface transport network layer association (TNLA), A source base station, Receives the ECGI of the target base station reported by the UE, A network element, Sends a configuration transfer message to the network element as a request for the X2 or Xn interface TNLA of the target base station, Starts an initial backoff timer, Starts an exponential backoff multiplier, Determines whether the time elapsed from the previous TNLA discovery procedure timestamp is greater than or equal to the current backoff time, where the current backoff time is equal to the previous backoff period multiplied by the exponential backoff multiplier, and the TNLA discovery procedure time is the time between the step of sending the configuration transfer message and receiving a network configuration transfer message from the network element, If the time elapsed from the previous TNLA discovery procedure time is greater than or equal to the current backoff time, resends the configuration transfer message to the network element; if the time elapsed from the previous TNLA discovery procedure time is less than the current backoff time, does not resend the configuration transfer message to the network element, If the network element configuration transfer message is received, performs an X2 or Xn setup with the target base station, A radio communication system comprising a source base station configured to stop the step of resending the configuration transfer message when the maximum backoff time is reached and the network element configuration transfer message is no longer received.

11. The radio communication system according to claim 10, wherein the network element transmits the network configuration transfer message after discovering identification information of the target base station.

12. The radio communication system according to claim 10, wherein the exponential backoff multiplier starts with an initially configured backoff period and then increases the backoff period by a factor multiplied by the previous backoff period, and the exponential backoff multiplier is configured with a maximum backoff time.

13. The wireless communication system according to claim 12, wherein the initial backoff timer, the exponential backoff multiplier, and the maximum backoff time are configurable.

14. The source base station determines whether the ECGI is from the same public land mobile network (PLMN) or from a blocked PLMN, and is further configured to start a configuration transfer procedure only for an ECGI that is from the same PLMN or from an unblocked PLMN, the wireless communication system according to claim 10.

15. The wireless communication system according to claim 14, wherein the source base station is an S-eNB, the target base station is a T-eNB, the network element is a mobility management entity (MME), and the X2 interface is implemented.

16. The wireless communication system according to claim 15, wherein the configuration transfer message is an eNB configuration transfer message and the network element configuration transfer message is an MME configuration transfer message.

17. The wireless communication system according to claim 14, wherein the source base station is an S-gNB, the target base station is a T-gNB, the network element is an access and mobility management function (AMF), and the Xn interface is implemented.

18. The wireless communication system according to claim 17, wherein the configuration transfer message is an uplink radio access network (RAN) configuration transfer message and the network element configuration transfer message is a downlink RAN configuration transfer message.

19. A non-transitory computer-readable storage medium having instructions stored therein that, when executed by a processing circuit, cause the processing circuit to execute a process, the process comprising: reporting, by a user equipment (UE), an extended cell global identifier (ECGI) of a target neighboring base station lacking an X2 or Xn interface TNLA at a source base station; receiving, by the source base station, the ECGI of the target neighboring base station lacking the X2 or Xn interface TNLA; A step of transmitting a configuration transfer message by the source base station to a network element to obtain the X2 or Xn interface TNLA of the target neighboring base station, the step of transmitting the configuration transfer message, and a step of waiting for the network element to transmit a network configuration transfer message in response to the configuration transfer message, wherein the time between them includes the TNLA discovery procedure time, A step of starting an initial backoff timer, A step of starting an exponential backoff multiplier, A step of determining whether the time elapsed from the previous TNLA discovery procedure timestamp is greater than or equal to the current backoff time, wherein the current backoff time is equal to the previous backoff period multiplied by the exponential backoff multiplier, If the time elapsed from the previous TNLA discovery procedure time is greater than or equal to the current backoff time, the source base station retransmits the configuration transfer message to the network element. If the time elapsed from the previous TNLA discovery procedure time is less than the current backoff time, the configuration transfer message is not retransmitted to the network element, If the network element configuration transfer message is received, a step of performing X2 or Xn setup between the source base station and the target base station, A non-transitory computer-readable storage medium including a step of stopping the source base station from retransmitting the configuration transfer message when the maximum backoff time is reached and the network element configuration transfer message is no longer received.

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