MANAGING CELL GROUP CONFIGURATION IN DISAGGREGATED BASE STATION ARCHITECTURE

In a base station central unit (CU) coupled to one or more base station distributed units (DUs), a base station CU determines that a UE should perform a reconfiguration with sync procedure (1204). The base station CU transmits, to a base station DU, an indication that the UE should perform a reconfiguration with sync procedure (1204). The base station CU then receives, in response to the indication, a cell group configuration IE including a reconfiguration with synchronization IE (1208), and transmits, to the base station DU, a message including the cell group configuration IE, to be forwarded to the UE (1210).

FIELD OF THE DISCLOSURE

This disclosure relates to wireless communications and, more particularly, to radio resource control procedures in disaggregated base station architecture.

BACKGROUND

In a disaggregated base station, a base station central unit (CU) is coupled to one or more base stations distributed units (DUs). For example, a 5G radio access network (RAN) can include a next-generation Node B (gNB) made up of a gNB-CU coupled to one or more gNB-DUs via the F1 interface. Generally speaking, a gNB-CU is a logical node hosting Radio Resource Control (RRC), Service Data Adaptation Protocol (SDAP) and Packet Data Convergence Protocol (PDCP) protocols of the gNB; and a gNB-DU is a logical node hosting radio link control (RLC), medium access control (MAC) and physical (PHY) layers of the gNB. The gNB-CU partly controls operation of the gNB-DU. A user device (or user equipment (“UE”), as user devices are known in technical literature) communicates with a gNB-DU via a radio interface that conforms to 5G New Radio (NR), and the gNB-DU exchanges messages with the corresponding gNB-CU.

The gNB-CU in various scenarios can direct the UE to perform random access using Radio Resource Control (RRC) procedures such as RRC reconfiguration, or direct the UE to omit random access using an RRC resume procedure. The RRC connection resume procedure generally applies to the RRC_INACTIVE state, which the 5G protocol introduced to allow a UE to more quickly transition back to the RRC_CONNECTED state due to radio access network (RAN)-level base station coordination and RAN-paging procedures.

The gNB can configure the UE in the RRC_CONNECTED with a certain cell group configuration, which includes such information as RLC bearer configuration, MAC configuration (MAC-CellGroupConfig), physical layer configuration (PhysicalCellGroupConfig), special cell configuration (SpCellConfig), and secondary cell configuration (SCellConfig). The cell group configuration can include reconfiguration with synchronization (or sync), which includes serving cell configuration (ServingCellConfigCommon), a new UE identity (Radio Network Temporary Identifier (RNTI)), and timer T304 value configuration. The reconfiguration with sync in some cases includes dedicated random access channel (RACH) configuration (RACH-ConfigDedicated).

In some scenarios, a UE transmits to the gNB-DU a request to activate an RRC connection, e.g., RRCResumeRequest, RRCResumeRequest1, RRCSetupRequest, or RRCReestablishmentRequest. The gNB-DU transmits the request to the gNB-CU along with a cell group configuration. The gNB-DU includes also the ReconfigurationWithSync information element (IE) in the cell group configuration for the gNB-CU to convey reconfiguration with sync information. The gNB-CU then generates a response to the request to activate an RRC connection and includes the cell group configuration with the ReconfigurationWithSync in the response.

Upon receiving the ReconfigurationWithSync IE, the UE resets the MAC entity of the cell group. This causes the UE to consider the Time Alignment timer expired, which in turn causes the UE to consider the uplink unsynchronized. The UE accordingly fails to activate an RRC connection.

SUMMARY

Generally speaking, the techniques of this disclosure prevent the gNB-DU from transmitting an RRC command that includes the ReconfigurationWithSync IE to the UE, under certain circumstances. The gNB-CU and/or the gNB-DU in various implementations thus cause the UE to not perform a reconfiguration with sync procedure and maintain (rather than reset) the MAC entity, and thereby retain link synchronization.

The gNB-CU in some implementations receives cell configuration information in the form of the cellGroupConfig IE from the gNB-DU, removes the ReconfigurationWithSync IE from the cellGroupConfig IE, and formats an RRC command for transmission to the UE via the gNB-DU with the modified cellGroupConfig IE. In these implementations, the gNB-CU formats the cellGroupConfig IE, and the gNB-DU then activates the radio connection while causing the UE to maintain the MAC entity by forwarding the RRC command to the UE via the radio interface.

In other implementation, the gNB-CU provides an indication to the gNB-DU that the gNB-DU should omit the ReconfigurationWithSync IE while formatting the cellGroupConfig IE. To this end, the gNB-CU in one example can use handover preparation information (e.g., where presence of the handover preparation information IE indicates that the gNB-DU should include the ReconfigurationWithSync IE, and absence of the handover preparation information IE indicates that the gNB-DU should omit the ReconfigurationWithSync IE). In another example implementation, the gNB-CU stores cell group configuration for the relevant cell group and provides a cellGroupConfig IE to the gNB-DU to indicate that the gNB-DU should include the ReconfigurationWithSync IE, and omits the cellGroupConfig IE from a message to the gNB-DU to indicate that the gNB-DU should omit the ReconfigurationWithSync IE).

One example embodiment of these techniques is a method in a base station CU coupled to one or more base station DUs. The method comprises receiving, by processing hardware from a base station DU, a cell group configuration information element (IE) including a reconfiguration with synchronization IE, related to a user equipment (UE). The method further includes determining, by the processing hardware, that the UE should not perform a reconfiguration with sync procedure; removing, by the processing hardware, the reconfiguration with synchronization IE from the cell group configuration IE to generate a modified cell group configuration IE; and transmitting, by the processing hardware to the base station DU, a message including the modified cell group configuration IE, to be forwarded to the UE.

Another example embodiment of these techniques is a method in a base station CU coupled to one or more base station DUs. The method includes determining, by processing hardware, that a UE should perform a reconfiguration with sync procedure; transmitting, by the processing hardware to a base station DU, an indication that the UE should perform a reconfiguration with sync procedure; receiving, by the processing hardware in response to the indication, a cell group configuration IE including a reconfiguration with synchronization IE; and transmitting, by the processing hardware to the base station DU, a message including the cell group configuration IE, to be forwarded to the UE.

Another embodiment of these techniques is a base station CU comprising processing hardware configured to implement the method above.

Yet another example embodiment of these techniques is a method in a base station DU coupled to a base station CU. The method comprises receiving, by processing hardware from a base station CU, an indication that a UE should perform a reconfiguration with sync procedure; generating, by the processing hardware, a cell group configuration IE that includes a reconfiguration with synchronization IE, for the UE; transmitting, by the processing hardware to the base station CU, the cell group configuration IE; receiving, by the processing hardware from the base station CU, a message for the UE including the cell group configuration IE; and transmitting, by the processing hardware to the UE, the message.

Still another embodiment of these techniques is a base station CU comprising processing hardware configured to implement the method above.

Another embodiment of these techniques is a disaggregated base station comprising a central unit (CU) and at least one distributed unit (DU) communicatively coupled to the base station DU. The disaggregated base station includes processing hardware configured to: (i) receive, via a radio interface from a user equipment (UE), an RRC message, determine that the UE should not perform a reconfiguration with sync procedure, and transmit an RRC command responsive to the RRC message, the RRC command including a cell group configuration IE and including a reconfiguration with synchronization IE.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1depicts an example wireless communication network100in which a disaggregated gNB104manages RRC cell group configuration so as to allow a UE102to avoid resetting the MAC entity under certain conditions, in accordance with the techniques discussed below. The examples below refer primarily to gNBs that can communicate with UEs over the 5G NR radio access technology (RAT). However, these techniques more generally can apply to any suitable disaggregated base station architecture.

The disaggregated gNB104includes gNB-CU110and gNB-DUs112A and112B. In general, the gNB-CU110can be coupled to one, two, or more than two gNB-DUs. The gNB-CU110is coupled to the gNB-CU110via an F1 interface. The gNB-CU110also can be coupled to another base station106, which can be disaggregated or non-disaggregated, via an Xn-C. The base station106can operate as a gNB or an eNB, and in some cases can operate as a master node (MN). In general, the wireless communication network100can include any number of base stations, and each of the base stations can cover one, two, three, or any other suitable number of cells. Further, the gNB-CU110is connected to a core network (CN)108of CN type 5GC. The gNB-DU112A in this example configuration covers a 5G NR cell120.

The UE102can be any suitable device capable of wireless communications (as further discussed below). The UE102is equipped with processing hardware130that can include one or more general-purpose processors (e.g., CPUs) and a non-transitory computer-readable memory storing instructions that the one or more general-purpose processors execute. Additionally or alternatively, the processing hardware130can include special-purpose processing units. The processing hardware130in an example implementation includes an RRC controller132, and the memory of the processing hardware stores a MAC entity134(e.g., as a data structure). The processing hardware130also can implement a Timing Alignment timer136.

The gNB-CU110also can include processing hardware such as one or more CPUs and a non-transitory computer-readable memory. The processing hardware of the gNB-CU110can implement a CU RRC controller140that controls RRC procedures. Processing hardware150of the gNB-DU112A also can include one or more general-purpose processors, a non-transitory computer-readable memory, special-purpose processing units, etc. The processing hardware in an example implementation includes a cell group configuration module154.

In operation, the UE102connects to the gNB-CU110via the gNB-DU112A. The gNB-DU112generates a certain cell group configuration for the UE102. The gNB-DU112also provides the cell group configuration of the UE102to the gNB-CU110, in the format of a CellGroupConfig IE. As discussed in more detail below, the gNB-DU112in some cases includes a ReconfigurationWithSync IE in the CellGroupConfig IE. When the gNB-CU140includes the ReconfigurationWithSync IE in an RRC command (such as RRCResume) and transmits the RRC command to the UE102via the gNB-DU112A, the UE102performs one or more actions associated with the reconfiguration with sync procedure, which resets the MAC entity134. As a result, the UE102considers the Timing Alignment timer136expires and determines that the uplink to the gNB-DU112A is not synchronized. The UE102accordingly does not transmit the RRCResumeComplete command to the gNB-DU112A.

To prevent the UE102from performing a reconfiguration with sync procedure (which causes the resetting of the MAC entity134), the CU RRC controller140determines in some cases that the gNB-CU110and/or gNB-DU112A should not include the ReconfigurationWithSync IE in the message to the UE102. In the various implementations discussed above, the CU RRC controller140provides an indication regarding omission of the ReconfigurationWithSync IE to the gNB-DU112A. Several example scenarios in which the CU RRC controller140provides such an indication are discussed next.

In the scenario ofFIG. 2, the UE102initiates202an RRC connection establishment, resume, or a reestablishment procedure. The UE102performs210a random access procedure with the gNB-DU112A and receives212a random access response including a timing advance command. The UE102then applies214the timing advance command to get the uplink synchronized and stats a timing alignment timer.

The UE102then transmits220an RRCResumeRequest or RRCResumeRequest1 message to the gNB-DU112A, which forwards222the RRCResumeRequest or RRCResumeRequest1 message and, when needed, the corresponding low-layer configuration for the UE102, to the gNB-CU110in the F1 Application Protocol (F1AP) INITIAL UL RRC MESSAGE TRANSFER message. To identify the UE102, the message can include the C-RNTI the gNB-DU112A allocated to the UE102.

The gNB-CU110transmits230an F1AP UE CONTEXT SETUP REQUEST message to establish the UE context in the gNB-DU112A. In some cases, this message also encapsulates an RRC SECURITY MODE COMMAND message. The gNB-DU112A responds232with a F1AP UE CONTEXT SETUP RESPONSE message containing a cellGroupConfig IE.

In some implementations, the gNB-DU112A includes in the F1AP UE CONTEXT SETUP RESPONSE message an indication of whether the CellGroupConfig IE contains a ReconfigurationWithSync IE. In one implementation, the F1AP UE CONTEXT SETUP RESPONSE message includes a binary indicator with a first value indicating that the ReconfigurationWithSync IE is present, and another value indicating that the ReconfigurationWithSync IE is absent. In another implementation, the F1AP UE CONTEXT SETUP RESPONSE message includes an optional flag, and presence of the optional flag indicates that the ReconfigurationWithSync IE is present. In still another implementation, presence of the optional flag indicates that the ReconfigurationWithSync IE is absent.

The gNB-CU110(e.g., the CU RRC controller140) determines233that the UE102should not perform a reconfiguration with sync procedure. The gNB-CU110removes234the ReconfigurationWithSync IE from the cellGroupConfig IE, when present. The gNB-CU110then formats or encodes an RRCResume message to respond to the RRCResumeRequest or RRCResumeRequest1 message, and includes the cellGroupConfig IE that does not include an ReconfigurationWithSync IE in the message. The gNB-CU110then forwards240the RRCResume message to the gNB-DU112A in an FLAP DL RRC MESSAGE TRANSFER message.

The gNB-DU112transmits242the RRCResume message to the UE102via the radio interface. Because the RRCResume message does not contain an ReconfigurationWithSync IE, the UE102does not reset the MAC entity134and does not consider uplink synchronization lost. The UE102accordingly responds244to the gNB-DU112A with an RRCResumeComplete message. The gNB-DU112A forwards246the RRCResumeComplete message to the gNB-CU110in an F1AP UL RRC MESSAGE TRANSFER message.

FIG. 3illustrates another scenario in which the gNB-CU110removes the ReconfigurationWithSync IE from the CellGroupConfig IE. The UE102first initiates302an RRC resume procedure. Similar to the scenario ofFIG. 2, the UE102performs310a random access procedure with the gNB-DU112A, receives312a random access response including a timing advance command, and UE applies314the timing advance command.

The UE102transmits320an RRCSetupRequest, RRCResumeReequest, RRCResumeReequest1, or RRCReestablishmentRequest message to the gNB-DU112A, which forwards322this message to the gNB-CU110in F1AP INITIAL UL RRC MESSAGE to the gNB-CU110. In some implementations, the gNB-DU112A includes in the F1AP INITIAL UL RRC MESSAGE message an indication of whether the CellGroupConfig IE contains a ReconfigurationWithSync IE.

The gNB-CU110then determines333that the UE102should not perform a reconfiguration with sync and removes334the ReconfigurationWithSync IE from the cellGroupConfig IE, when present. The gNB-CU110forwards340the RRCResume message to the gNB-DU112A in an F1AP DL RRC MESSAGE TRANSFER message, the gNB-DU112A transmits342the RRCSetup message without an ReconfigurationWithSync IE to the UE102via the radio interface, and the UE102resumes the RRC connection without resetting the MAC entity. The UE102responds344to the gNB-DU112A with an RRCSetupComplete message, which the gNB-DU112A forwards346to the gNB-CU110in an F1AP UL RRC MESSAGE TRANSFER message.

Referring generally toFIGS. 2 and 3, the gNB-CU110in some cases can decide to perform a UE Context Modification procedure and utilize similar techniques to prevent the UE102from resetting the MAC entity. More particularly, upon detecting an SpCell change, PSCell addition, SI update for PSCell and security key change, the gNB-CU110can determine that the UE102should perform a reconfiguration with sync procedure and transmit an RRC Reconfiguration message including the ReconfigurationWithSync IE to the UE102via the gNB-DU112A. In other cases, the gNB-CU110can determine that the UE102should not perform a reconfiguration with sync procedure and transmit an RRC Reconfiguration message that does not include the ReconfigurationWithSync IE to the UE102via the gNB-DU112A.

Next,FIG. 4illustrates a scenario in which gNB-CU110provides to the gNB-DU112A an implicit indication that the gNB-112A should not cause the UE102to perform a reconfiguration with sync procedure and reset the MAC entity. The UE102in this scenario initiates402an RRC connection establishment, resume, or a reestablishment procedure. The UE102performs410a random access procedure with the gNB-DU112A and receives412a random access response including a timing advance command. The UE102then applies414the timing advance command to get the uplink synchronized, starts a timing alignment timer, and transmits220an RRCResumeRequest or RRCResumeRequest1 message to the gNB-DU112A, and in response the gNB-DU112A forwards422this message to the gNB-CU110in an INITIAL UL RRC MESSAGE TRANSFER message.

The gNB-CU110determines427that the UE102should nor perform a reconfiguration with sync procedure and determines428to not include the HandoverPreparationInfo in the CU to DU RRC Information IE. Presence or absence of HandoverPreparationInfo in this case operates as an implicit indication of whether the gNB-DU112A should include or not include the ReconfigurationWithSync IE in the CellGroupConfig IE for the UE102.

The gNB-CU110transmits430an F1AP UE CONTEXT SETUP REQUEST message with the CU to DU RRC Information IE to the gNB-DU112A. The gNB-DU112A then determines431whether the CU to DU RRC Information IE includes HandoverPreparationInfo. When the CU to DU RRC Information IE includes HandoverPreparationInfo, the gNB-DU112A generates a cellGroupConfig IE that includes the ReconfigurationWithSync IE; otherwise, when the CU to DU RRC Information IE does not include HandoverPreparationInfo, the gNB-DU112A generates a cellGroupConfig IE that does not include the ReconfigurationWithSync IE.

The gNB-DU112A transmits432an F1AP UE CONTEXT SETUP RESPONSE message containing a cellGroupConfig IE. Then, similar to the scenario ofFIG. 2, for example, the gNB-CU110forwards440the RRCResume message to the gNB-DU112A in an F1AP DL RRC MESSAGE TRANSFER message, the gNB-DU112transmits442the RRCResume message to the UE102via the radio interface, the UE102responds444to the gNB-DU112A with an RRCResumeComplete message (when the cellGroupConfig IE does not include the ReconfigurationWithSync IE), and the gNB-DU112A forwards446the RRCResumeComplete message to the gNB-CU110in an F1AP UL RRC MESSAGE TRANSFER message.

FIG. 5illustrates a scenario in which a gNB-CU uses handover preparation information to provide, to a gNB-DU, an implicit indication that the gNB-DU should not include a reconfiguration with sync in a CellGroupConfig IE for a UE during an RRC connection establishment procedure. The UE102in this initiates502an RRC connection establishment procedure. The UE102performs510a random access procedure with the gNB-DU112A, receives512a random access response including a timing advance command, and applies514the timing advance command to get the uplink synchronized and starts a timing alignment timer.

The UE102transmits520an RRCSetupRequest message to the gNB-DU112A, which then forwards522this message to the gNB-CU110in F1AP INITIAL UL RRC MESSAGE to the gNB-CU110. The gNB-CU110transmits522an F1AP DL RRC MESSAGE TRANSFER message enclosing an RRCSetup command to the gNB-DU112A. The gNB-DU112A forwards523the RRCSetup command to the UE102, the UE102responds525with an RRCSetupComplete message, and the gNB-DU112A forwards526the RRCSetupComplete message to the gNB-CU110in an F1AP RRC MESSAGE TRANSFER message.

The gNB-CU110determines527that the determines that the UE102should not perform a reconfiguration with sync procedure and determines528to not include the HandoverPreparationInfo in the CU to DU RRC Information IE. Similar to the scenario ofFIG. 4, presence or absence of HandoverPreparationInfo in this case operates as an implicit indication of whether the gNB-DU112A should include or not include the ReconfigurationWithSync IE in the CellGroupConfig IE for the UE102.

The gNB-CU110transmits530an F1AP UE CONTEXT SETUP REQUEST message with the CU to DU RRC Information IE to the gNB-DU112A. The F1AP UE CONTEXT SETUP REQUEST message in this case also includes a SecurityModeCommand. The gNB-DU112A forwards529the SecurityModeCommand message to the UE102. The gNB-DU112A then determines531whether the CU to DU RRC Information IE includes HandoverPreparationInfo. When the CU to DU RRC Information IE includes HandoverPreparationInfo, the gNB-DU112A generates a cellGroupConfig IE that includes the ReconfigurationWithSync IE; otherwise, when the CU to DU RRC Information IE does not include HandoverPreparationInfo, the gNB-DU112A generates a cellGroupConfig IE that does not include the ReconfigurationWithSync IE. The gNB-DU112A transmits532an F1AP UE CONTEXT SETUP RESPONSE message containing a cellGroupConfig IE.

After the UE102responds560to SecurityModeCommand with a SecurityModeComplete message, and the gNB-DU112A forwards562this message to the gNB-CU110in a UL RRC MESSAGE TRANSFER message. As further illustrated inFIG. 5, the gNB-CU110subsequently transmits to the gNB-112A a DL RRC MESSAGE TRANSFER message enclosing an RRCReconfiguration message. The gNB-DU112A forwards566this message to the UE102and receives566RRCReconfigurationComplete in response. The gNB-DU112A forwards570the RRCReconfigurationComplete message to the gNB-CU110in an UL RRC MESSAGE TRANSFER message.

The scenario ofFIG. 6is similar to the scenario ofFIG. 4, except that here the gNB-CU110uses the cellGroupConfig IE to indicate whether the gNB-DU112A should provide the ReconfigurationWithSync IE to the UE102, thereby causing the UE102to reset the MAC entity.

The events602,610,612,614,620, and622are similar to the events402,610,612,614,620, and622, respectively. The gNB-CU110determines627the UE102should not perform a reconfiguration with sync procedure. According to this implementation, the gNB-CU110indicates to the gNB-112A that the UE102should not perform a reconfiguration with sync procedure by not including628the CellGroupConfig IE in the CU to DU RRC Information IE. The gNB-CU110the transmits630an F1AP UE CONTEXT SETUP REQUEST message with the CU to DU RRC Information IE to the gNB-DU112A.

The gNB-DU112A accordingly determines631whether the CU to DU RRC Information IE includes the CellConfigInfo IE. When the CU to DU RRC Information IE includes the CellConfigInfo IE, the gNB-DU112A generates a cellGroupConfig IE that includes the ReconfigurationWithSync IE for the subsequent F1AP UE CONTEXT SETUP RESPONSE message; otherwise, when the CU to DU RRC Information IE does not include, the CellConfigInfo IE, the gNB-DU112A generates a cellGroupConfig IE that does not include the ReconfigurationWithSync IE in the subsequent F1AP UE CONTEXT SETUP RESPONSE message. The remaining events632,640,642,644, and646in this scenario are similar to the events432,440,442, and446, respectively.

Thus, the gNB-CU110in some implementations can format the CellGroupConfig1E in a manner that does not require the gNB-DU112A to reformat this IE, as discussed with reference toFIGS. 2 and 3. As one alternative, the gNB-CU110can implicitly indicate to the gNB-DU112A that the gNB-DU112A should cause the UE102to not perform a reconfiguration with sync procedure by including or not including a certain IE such as HandoverPreparationInfo or CellGroupConfig, as discussed with reference toFIGS. 4-6. More generally, the gNB-CU110can provide this implicit indication using any IE whose presence or absence is related to whether the UE102should reset its MAC entity. Further, the gNB-CU110in some implementations can include an explicit indicator or flag in the F1AP message transmitted to the gNB-DU112A, so that one value of the flag indicates that the gNB-DU112A should include the ReconfigurationWithSync IE in the cellGroupConfig IE, and another value of the flag indicates that the gNB-DU112A should not include the ReconfigurationWithSync IE in the cellGroupConfig IE (or presence of the flag indicates that the gNB-DU112A should include the ReconfigurationWithSync IE in the cellGroupConfig IE, and absence of the flag indicates that the gNB-DU112A should not include the ReconfigurationWithSync IE from the cellGroupConfig IE).

As further demonstrated in the discussion above, a disaggregated base station, such as the gNB104, can generate the cellGroupConfig IE in the format provided to the UE102at a CU or a DU, depending on the implementation.

Next,FIG. 7illustrates a scenario in which the gNB-CU110supports non-standalone operation, i.e., dual connectivity in addition to standalone operation. The base station106in this case operates as a Master eNB (MeNB). The MeNB106transmits702, to the gNB-CU110, an SgNB Addition Request message that includes a CG-ConfigInfo IE. The gNB-CU110transmits704an F1AP UE CONTEXT SETUP REQUEST message to the gNB-DU112A and includes the CG-ConfigInfo in this message. The gNB-DU112A then determines706whether the cellGroupConfig IE should include the ReconfigurationWithSync IE based on whether the F1AP UE CONTEXT SETUP REQUEST message includes the CG-ConfigInfo IE. For example, when the F1AP UE CONTEXT SETUP REQUEST message includes the CG-ConfigInfo IE, the gNB-DU112A can include the ReconfigurationWithSync IE in the cellGroupConfig IE; otherwise, when the F1AP UE CONTEXT SETUP REQUEST message does not include the CG-ConfigInfo IE, the gNB-DU112A does not include the ReconfigurationWithSync IE in the cellGroupConfig IE.

The gNB-DU112A transmits708a F1AP UE CONTEXT SETUP RESPONSE message containing a cellGroupConfig IE to the gNB-CU110, which then transmits710an SgNB Addition Request Acknowledge message that includes a CG-Config message, which in turn includes an RRCConnectionReconfiguration message. The MeNB106transmits712the RRCReconfiguration via the radio interface of the MN, and the UE102responds714with RRCConnectionReconfigurationComplete. The MeNB106transmits716an SgNB Reconfiguration Complete message to the gNB-CU110. Subsequently to these steps, the gNB-CU transmits718downlink user data to the gNB-DU112A, and the UE102can perform720a random access procedure to utilize the radio resources of the gNB-DU112A in addition to those of the MeNB106.

Referring generally to the messaging diagrams above, in at least some of the implementations, the gNB-CU110initiates the UE Context Setup procedure for handover if at least one DRB is set up for the UE102, when the gNB-CU110operates as a MN. Similarly, the gNB-CU110can initiate the UE Context Setup procedure for handover if at least one DRB is set up for the UE102, when the gNB-CU110operates as a MN.

Next, several example methods that can be implemented in the gNB-CU110and/or gNB-DU112A are discussed with reference toFIGS. 8-13.

Referring first toFIG. 8, an example method800for generating an RRC message with a modified cell group configuration can be implemented in a CU such as the gNB-CU110ofFIG. 1. The method800can be implemented using any suitable combination of software, hardware, and/or firmware.

At block802, the gNB-CU receives, from the gNB-DU (e.g., the gNB-DU112A), an INITIAL UL RRC MESSAGE TRANSFER message that conveys an RRC message received from a UE (e.g., the UE102). The RRC message can indicate a request that the RRC message be resumed, e.g., RRCResumeRequest or RRCResumeRequest1. Next, at block804, the gNB-CU transmits a request to establish a UE context in the gNB-DU. The gNB-CU receives a response to this request at block806.

The response includes a CellGroupConfig IE or, more generally, information conveying cell group configuration. The gNB-CU determines at block808that the UE should not perform a reconfiguration with sync procedure. The gNB-CU accordingly determines that the RRCResume message responsive to the RRC message received at block802should not contain the ReconfigurationWithSync IE (or, more generally, a reconfiguration with synchronization indication which causes the UE to reset its MAC entity).

At block810, the gNB-CU determines whether the IE conveying cell group configuration received at block806includes the ReconfigurationWithSync IE and, if so, removes this IE at block812. Otherwise, the flow proceeds directly to block814, where the gNB-CU transmits an RRC message (e.g., RRCResume) with the CellGroupConfig IE to the gNB-DU, to be forwarded to the UE.

FIG. 9illustrates another example method for generating an RRC message with a modified cell group configuration, which also can be implemented in the gNB-CU110or another suitable CU. The method900begins at block902, where the gNB-CU receives, from the gNB-DU, an INITIAL UL RRC MESSAGE TRANSFER message that conveys an RRC message such as RRCSetupRequest, RRCResumeReequest, RRCResumeReequest1, or RRCReestablishmentRequest. Unlike the example ofFIG. 8, the INITIAL UL RRC MESSAGE TRANSFER message includes the CellGroupConfig IE, which in some cases includes the ReconfigurationWithSync IE.

Similar to block808ofFIG. 8, the gNB-CU determines at block908that the UE should not perform a reconfiguration with sync procedure, which resets its MAC entity. The gNB-CU then determines at block910whether the CellGroupConfig IE received from the gNB-DU includes the ReconfigurationWithSync IE and, if so, removes the ReconfigurationWithSync IE from the CellGroupConfig IE at block912. Otherwise, the flow proceeds directly to block914, where the gNB-CU transmits an RRC message (e.g., RRCSetup) with the CellGroupConfig IE to the gNB-DU, to be forwarded to the UE.

FIG. 10illustrates an example method1000for generating an implicit indication that the gNB-DU should not include the ReconfigurationWithSync IE in an RRC message to a UE, which can be implemented in the gNB-CU110. At1002, the gNB-CU receives an INITIAL UL RRC MESSAGE TRANSFER message, similar to block902. The gNB-CU determines that the UE should not perform a reconfiguration with sync procedure, which resets its MAC entity, at block1008and prepares a CU to DU RRC Info IE at block1010. The gNB-CU does not include HandoverPreparationInfo in the CU to DU RRC Info IE to indicate to the gNB-DU that the UE should not perform a reconfiguration with sync procedure, which resets its MAC entity. The gNB-CU then transmits an FLAP UE CONTEXT SETUP REQUEST message including the CU to DU RRC Info IE to the gNB-DU at block1012, and receives an F1AP UE CONTEXT SETUP RESPONSE message in response at block1014. The received message includes a cellGroupConfig IE that does not include the ReconfigurationWithSync IE. The gNB-CU then formats and transmits an RRC Message including the cellGroupConfig IE to the gNB-DU, for transmission to the UE, at block1016.

FIG. 11is a flow diagram of another example method for generating an implicit indication that the gNB-DU should omit the ReconfigurationWithSync IE from an RRC message to a UE, which can be implemented in the gNB-CU110. Block1102-1116are similar to blocks1002-1016, but at block1100the gNB-CU uses inclusion or exclusion of the cellGroupConfig IE to implicitly indicate to the gNB-DU whether the RRC message to the UE should include the ReconfigurationWithSync IE.

Next,FIG. 12illustrates an example method for causing a UE to not perform a reconfiguration with sync procedure, which can be implemented in a CU unit of a base station, e.g., the gNB-CU110.

At block1204, the CU determines that the UE should not perform a reconfiguration with sync procedure, in connection with the procedure (e.g., the RRC procedure) the CU will perform with the UE (e.g., event233ofFIG. 2, event333ofFIG. 3, event427ofFIG. 4, event527ofFIG. 5, event627ofFIG. 6, event706ofFIG. 7; see also block808ofFIG. 8, block908ofFIG. 9, block1008ofFIG. 10, or block1108ofFIG. 11).

Next, at block1208, the CU receive a cell group configuration IE including the reconfiguration with sync IE from the DU (e.g., event432ofFIG. 4, event532inFIG. 5, event632inFIG. 6, event708ofFIG. 7; see also block1014ofFIG. 10, block1114ofFIG. 11).

At block1210, the CU transmits a message (e.g., an RRC message responsive to the message received from the UE via the DU) to the DU, to be forwarded to the UE (e.g., event440ofFIG. 4, event570ofFIG. 5, event640ofFIG. 6, event710ofFIG. 7; see also block814ofFIG. 8, block914ofFIG. 9, block1016ofFIG. 10, block1106ofFIG. 11). The message includes the cell group configuration IE received at block1208.

FIG. 13illustrates an example method for causing a UE to perform reconfiguration with sync, which can be implemented in a DU unit of a base station, e.g., the gNB-DU112A.

At block1302, the DU receives an indication that the UE should perform the reconfiguration with sync, from the CU (generally similar to the events428and430ofFIG. 4, events528and530ofFIG. 5, events628and630ofFIG. 6, event704ofFIG. 7; see also blocks1010and1012ofFIG. 10, blocks1110and1112ofFIG. 11).

In some implementations, prior to executing block1302, the DU generates and transmits to the CU an Initial UL RRC Message Transfer message including the cell group configuration IE. The DU does not include a reconfiguration with synchronization indication IE in the cell group configuration IE.

At block1304, the DU generates a cell group configuration IE including the reconfiguration with sync IE (event431ofFIG. 4, event531ofFIG. 5, event631ofFIG. 6, events706and707ofFIG. 7). The DU transmits the cell group configuration IE including to the CU at block1306(event432ofFIG. 4, event532ofFIG. 5, event632ofFIG. 6, event708ofFIG. 7).

Finally,FIG. 14illustrates another example method for causing a UE to not perform a reconfiguration with sync procedure, which can be implemented in a CU unit of a base station, e.g., the gNB-CU110. According to this method, the CU (rather than the DU) formats the information element that determines whether the UE performs reconfiguration with sync.

The method1400begins at block1402, where the CU receives cell group configuration with a reconfiguration with sync indicator, from a DU unit (event232ofFIG. 2, event322ofFIG. 3; see also block806ofFIG. 8, block902ofFIG. 9).

At block1404, the CU determines that the UE should not perform reconfiguration with sync (event233ofFIG. 2, event333ofFIG. 3; see also block808ofFIG. 8, block908ofFIG. 9).

The CU at block1406removes the reconfiguration with sync indicator (when present) from the cell group configuration received from the DU (event234ofFIG. 2, event334ofFIG. 4; see also block812ofFIG. 8, block912ofFIG. 9).

At block1408, the CU transmits a message including the modified cell group configuration to the UE via the DU unit (event240ofFIG. 2, event340ofFIG. 3; see also block814ofFIG. 8, block914ofFIG. 9).

Referring generally toFIGS. 12-14, in some cases the CU formats the final version of the cellGroupConfig IE for transmission to the UE (e.g., events240and242ofFIG. 2, events340and342ofFIG. 3, event706ofFIG. 7), and in other cases the DU formats the cellGroupConfig IE for transmission to the UE, and the CU does not perform any further modification (e.g., event431ofFIG. 4, event531ofFIG. 5, event631ofFIG. 6).

The following additional considerations apply to the foregoing discussion.

A user device in which the techniques of this disclosure can be implemented (e.g., the UE102) can be any suitable device capable of wireless communications such as a smartphone, a tablet computer, a laptop computer, a mobile gaming console, a point-of-sale (POS) terminal, a health monitoring device, a drone, a camera, a media-streaming dongle or another personal media device, a wearable device such as a smartwatch, a wireless hotspot, a femtocell, or a broadband router. Further, the user device in some cases may be embedded in an electronic system such as the head unit of a vehicle or an advanced driver assistance system (ADAS). Still further, the user device can operate as an internet-of-things (IoT) device or a mobile-internet device (MID). Depending on the type, the user device can include one or more general-purpose processors, a computer-readable memory, a user interface, one or more network interfaces, one or more sensors, etc.

Certain embodiments are described in this disclosure as including logic or a number of components or modules. Modules may can be software modules (e.g., code stored on non-transitory machine-readable medium) or hardware modules. A hardware module is a tangible unit capable of performing certain operations and may be configured or arranged in a certain manner. A hardware module can comprise dedicated circuitry or logic that is permanently configured (e.g., as a special-purpose processor, such as a field programmable gate array (FPGA) or an application-specific integrated circuit (ASIC)) to perform certain operations. A hardware module may also comprise programmable logic or circuitry (e.g., as encompassed within a general-purpose processor or other programmable processor) that is temporarily configured by software to perform certain operations. The decision to implement a hardware module in dedicated and permanently configured circuitry, or in temporarily configured circuitry (e.g., configured by software) may be driven by cost and time considerations.

When implemented in software, the techniques can be provided as part of the operating system, a library used by multiple applications, a particular software application, etc. The software can be executed by one or more general-purpose processors or one or more special-purpose processors.

Upon reading this disclosure, those of skill in the art will appreciate still additional alternative structural and functional designs for support packet-based voice and video calls through the disclosed principles herein. Thus, while particular embodiments and applications have been illustrated and described, it is to be understood that the disclosed embodiments are not limited to the precise construction and components disclosed herein. Various modifications, changes and variations, which will be apparent to those of ordinary skill in the art, may be made in the arrangement, operation and details of the method and apparatus disclosed herein without departing from the spirit and scope defined in the appended claims.

The following list of aspects reflects a variety of the embodiments explicitly contemplated by the present disclosure.

Aspect 1. A method in a base station CU coupled to one or more base station DUs (DUs) comprises: receiving, by processing hardware from a base station DU, a cell group configuration IE including a reconfiguration with synchronization IE, related to a UE; determining, by the processing hardware, that the UE should not perform a reconfiguration with sync procedure; removing, by the processing hardware, the reconfiguration with synchronization IE from the cell group configuration IE to generate a modified cell group configuration IE; and transmitting, by the processing hardware to the base station DU, a message including the modified cell group configuration IE, to be forwarded to the UE.

Aspect 2. The method of aspect 1, wherein receiving the cell group configuration IE from the base station DU includes: receiving, by the processing hardware from the base station DU, an Initial UL radio resource control (RRC) Message Transfer message; transmitting, by the processing hardware to the base station DU, a UE Context Setup Request message; and receiving, by the processing hardware from the base station DU, a UE Context Setup Response message including the cell group configuration IE.

Aspect 3. The method of aspect 1, wherein receiving the cell group configuration IE from the base station DU includes receiving, by the processing hardware from the base station DU, an Initial UL RRC Message Transfer message including the cell group configuration IE.

Aspect 4. The method of aspect 1, further comprising: receiving, by the processing hardware from the base station DU, an RRC request for one of (i) setting up a new RRC connection, (ii) resuming an RRC connection, or (iii) reestablishing an RRC connection, transmitted by the UE; wherein transmitting the message includes generating an RRC command responsive to the request from the UE.

Aspect 5. The method of aspect 1, wherein receiving the cell group configuration IE, the removing and transmitting the modified cell group configuration IE occur in a first instance, the method further comprising, in a second instance: determining, by the processing hardware, that the cell group configuration IE was received during a UE context modification procedure in response to one of (i) a special cell (SpCell) change, (ii) a primary secondary cell (PSCell) change, or (iii) a system information (SI) change for the PSCell, and including the cell group configuration IE in an RRC command, including not modifying the cell group configuration IE.

Aspect 6. The method of aspect 1, further comprising: receiving, by the processing hardware from the base station DU, a reconfiguration with sync presence indicator indicating that the cell group configuration IE includes the reconfiguration with synchronization IE.

Aspect 7. The method of aspect 1, further comprising: receiving, by the processing hardware from the base station DU, a reconfiguration with sync absence indicator indicating that the cell group configuration IE does not include the reconfiguration with synchronization IE.

Aspect 8. The method of aspect 6 or 7, further comprising: receiving the reconfiguration with sync presence indicator or the reconfiguration with sync absence indicator in one of an Initial UL RRC Message Transfer message or an UE Context Setup Response message.

Aspect 9. A method in a base station CU coupled to one or more base station DUs comprises: determining, by processing hardware, that a UE should perform a reconfiguration with sync procedure; transmitting, by the processing hardware to a base station DU, an indication that the UE should perform a reconfiguration with sync procedure; receiving, by the processing hardware in response to the indication, a cell group configuration IE including a reconfiguration with synchronization IE; and ransmitting, by the processing hardware to the base station DU, a message including the cell group configuration IE, to be forwarded to the UE.

Aspect 10. The method of aspect 9, wherein transmitting the indication to the base station DU includes: transmitting, by the processing hardware to the base station DU, a UE Context Setup Request message that includes handover preparation information, and

receiving, by the processing hardware from the base station DU in response to the UE Context Setup Request message, a UE Context Setup Response message including the cell group configuration IE that includes the reconfiguration with synchronization IE.

Aspect 11. The method of aspect 9, wherein transmitting the indication to the base station DU includes: transmitting, by the processing hardware to the base station DU, a UE Context Setup Request message that includes cell group configuration information, and receiving, by the processing hardware from the base station DU in response to the UE Context Setup Request message, a UE Context Setup Response message including a cell group configuration IE that includes the reconfiguration with synchronization IE.

Aspect 12. The method of aspect 9, further comprising: receiving, by the processing hardware from a master base station, a request to add the base station CU and the base station DU as a secondary base station, the request including cell group configuration information from the master base station; and wherein transmitting the indication to the base station DU includes: transmitting, by the processing hardware to the base station DU, a UE Context Setup Request message that includes the cell group configuration information from the master base station, and receiving, by the processing hardware from the base station DU in response to the UE Context Setup Request message, a UE Context Setup Response message including the cell group configuration IE that includes the reconfiguration with synchronization IE.

Aspect 13. The method of aspect 9, wherein the base station CU and the base station DU operate as an SN, and wherein the indication transmitted to the base station DU is received from an MN.

Aspect 14. The method of aspect 13, wherein the indication from the MN is a CG-ConfigInfo IE.

Aspect 15. The method of aspect 9, further comprising: receiving, by the processing hardware from the base station DU, a radio resource control (RRC) request for one of (i) setting up a new RRC connection, (ii) resuming an RRC connection, or (iii) reestablishing an RRC connection, transmitted by the UE; wherein transmitting the message includes generating an RRC command responsive to the request from the UE.

Aspect 16. A base station CU comprising processing hardware configured to implement a method of any of the preceding aspects.

Aspect 17. A method in a base station DU coupled to a base station CU, the method comprising: receiving, by processing hardware from a base station CU, an indication that a UE should perform a reconfiguration with sync procedure; generating, by the processing hardware, a cell group configuration IE that includes a reconfiguration with synchronization IE, for the UE; transmitting, by the processing hardware to the base station CU, the cell group configuration IE; receiving, by the processing hardware from the base station CU, a message for the UE including the cell group configuration IE; and transmitting, by the processing hardware to the UE, the message.

Aspect 18. The method of aspect 17, further comprising: receiving, by processing hardware from the UE, an RRC request for one of (i) setting up a new RRC connection, (ii) resuming an RRC connection, or (iii) reestablishing an RRC connection, transmitted by the UE; wherein message received from the base station CU is an RRC command responsive to the RRC request from the UE.

Aspect 19. The method of aspect 17, wherein: the indication is received in a UE Context Setup Request message, and the cell group configuration IE is transmitted in a UE Context Setup Response message.

Aspect 20. The method of aspect 18, further comprising: determining that the indication has been received if the UE Context Setup Request message includes handover preparation information.

Aspect 21. The method of aspect 18, further comprising: determining that the indication has been received if the UE Context Setup Request message includes a cell group configuration IE or a CG-ConfigInfo IE.

Aspect 22. The method of aspect 17, further comprising: transmitting, by the processing hardware to the base station CU, an IE presence indicator indicating that the cell group configuration IE includes a reconfiguration with synchronization IE.

Aspect 23. The method of aspect 17, further comprising: transmitting, by the processing hardware to the base station CU, an IE absence indicator indicating that the cell group configuration IE does not include the reconfiguration with synchronization indication IE.

Aspect 24. The method of aspect 22 or 23, further comprising transmitting the IE presence indicator or the IE absence indicator in one of an Initial UL RRC Message Transfer message or a UE Context Setup Response message.

Aspect 25. A base station distributed unit (DU) comprising processing hardware configured to implement a method of any of aspects 17-24.

Aspect 26. A disaggregated base station comprising: a distributed unit (DU) and a central unit (CU) communicatively coupled to the base station DU; the disaggregated base station including processing hardware configured to: receive, via a radio interface from a user equipment (UE), an RRC message; determine that the UE should not perform a reconfiguration with sync procedure; and transmit an RRC command responsive to the RRC message, the RRC command including a cell group configuration IE and not including a reconfiguration with synchronization IE.