CN101668320B - Method for reducing handover delay in long term evolution systems - Google Patents
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Abstract
The embodiment of the invention discloses a method for reducing handover delay in LTE systems. The method comprises that: source eNB sends a handover request to alternative target eNB of all alternative target cells of which the management meets handover judgment conditions, agrees to allow the alternative target eNB to which the alternative target cells with the handover request to reserve resources for current handover, and stores context of user equipment UE performing the current handover; and the alternative target eNB informs the source eNB of the information of the alternative target cells agreeing to the handover request. The method can trigger all alternative target eNB to be reserved resources for the current handover so as to reduce the handover delay caused by a currently selected target eNB not agreeing to hand over. In addition, in the process of handover execution, the source eNB simultaneously forwards data to all the alternative target eNB returning response to the handover request, so data loss caused by handover failure can be avoided.
Description
Technical field
The present invention relates to the handoff technique of the communications field, relate in particular to a kind of in Long Term Evolution (Long Term Evolution, LTE) method of shortening handover delay in the system.
Background technology
The process of in the LTE system, switching comprises switch decision stage, handoff preparation phase, handover execution stage and switching completion stage.Below in conjunction with the idiographic flow that in the LTE system, switches at present, the method for in the LTE system, switching is introduced.
Fig. 1 is the method flow diagram that in the LTE system, switches at present, and as shown in Figure 1, this method comprises:
Step 101, (User Equipment UE) measures communication quality between this UE and each neighbor cell to source base station (eNB) control subscriber equipment, and the formation measurement report.
Step 102～step 103 is the switch decision stage.
At switch decision in the stage; The measurement report that source eNB sends according to UE and present load situation of each eNB etc. are selected the alternative target cells that satisfies the switch decision condition, and the said number that satisfies the alternative target cells of switch decision condition maybe be for (comprising two) more than two.Particularly:
Step 102, UE sends measurement report to source eNB.
Step 103, source eNB carries out switch decision, selects the alternative target cells that satisfies the switch decision condition.
Step 104～step 106 is a handoff preparation phase.
In handoff preparation phase, source eNB selects the target eNB switched from alternative target eNB, trigger target eNB and carry out acceptance judging, target eNB in admission judgment result when accepting this UE, for this UE reservation switchable resource and store the context of this UE.Wherein, alternative target eNB is meant the eNB of management alternative target cells, and target eNB is accepted to have in the sub-district that this UE is meant that this target eNB manages and agreed to accept this UE's.In addition, an alternative target eNB can only manage a sub-district, also can manage a plurality of sub-districts, and the communication means between eNB and its sub-district of managing is a prior art, not in the discussion scope of this paper.
Specify in the face of step 104～step 106 down:
Step 104, source eNB selects the optimal objective sub-district from the alternative target cells that satisfies the switch decision condition, send handoff request (Handover Request) message to the alternative target eNB of this optimal objective sub-district of management.
Step 105, whether said alternative target eNB admits this UE to make acceptance judging according to said optimal objective sub-district.
In this step, if this UE is admitted in this optimal objective sub-district, then the alternative target eNB of this optimal objective sub-district of expression management agrees said handoff request; Execution in step 106; Otherwise the target eNB of this optimal objective sub-district of expression management is disagreed with said handoff request, and then this alternative target eNB returns to switch to source eNB and prepares failure (Handover Preparation Failure) message; Source eNB carries out the corresponding operating after the handoff request failure, specifically asks for an interview the civilian related description in back.
Step 106, alternative target eNB returns handoff request to source eNB and replys (Handover Request ACK) message.
Step 107～step 111 is a handover execution stage.
In handover execution stage; After source eNB receives the Handover Request ACK message of alternative target eNB; With this alternative target eNB as target eNB; The sign of optimal objective sub-district is carried in the switching command, sends said switching command to UE, source eNB begins to carry out data forwarding to the target eNB of the said optimal objective of management sub-district; Wherein, the data of preceding commentaries on classics comprise that high level is issued the new data of this UE, source eNB issues this UE and still do not receive the data of this UE affirmation and the up discontinuous data that UE sends.After said UE receives said switching command, according to the sign of the optimal objective sub-district of carrying in this switching command, set up uplink synchronous from the disengaging of old sub-district and with said target eNB, said target eNB is that this UE authorizes ascending resource and confirms Timing Advance.
Specify in the face of step 107～step 111 down:
Step 107, source eNB is carried at the sign of optimal objective sub-district and is handed down to UE in the switching command.
Step 108, source eNB is to target eNB state transitions (the SN Status Transfer) message that transmits Sequence Number, and begins to carry out data forwarding to target eNB.
Step 109, UE sets up uplink synchronous according to the sign of the optimal objective sub-district of carrying in the switching command with the target eNB of this optimal objective sub-district of management.
Step 110, target eNB are sent uplink synchronous to this UE and are confirmed and Timing Advance that UE receives said uplink synchronous affirmation and Timing Advance, and the uplink synchronous of then said UE and target eNB is set up and finished.
Step 111, UE sends up switching to target eNB and accomplishes (Handover Complete) message.
Carry out step 109～process of step 111 in; If the Radio Link connection failure between the Serving cell of UE and this UE is perhaps to the Target cell access failure; Then this UE need reselect Target cell and carries out wireless link recovery or switching; Said needs are reselected the concrete grammar that Target cell recovers or switches, and see back literary composition explanation for details.
Step 112～step 118 is for switching the completion stage.
Switching in the completion stage, gateway (Serving GW) is accomplished the conversion of downlink path, and target eNB guarantees to send according to the order of sequence to the data that belong to said UE that receive that preceding transfer and new.Source eNB the data of the order of the release resource of receiving target eNB and said UE change before finish after, discharge the resource that said UE takies.
Specify in the face of step 112～step 118 down:
Step 112, target eNB is to MME transmit path transfer request (Path Swith Request) message.
Step 113, MME sends user plane to Serving GW and upgrades request (User Plane update request) message.
Step 114; Serving GW carries out data path to be shifted; And, data path sends the bag that carries end mark (END MARK) after shifting completion to source eNB; Expression Serving GW accomplishes to the downlink data to said UE that source eNB sends, and Serving GW sends the downlink data to said UE to target eNB afterwards.
Step 115, Serving GW sends user plane to MME and upgrades response (User Plane update request response) message.
Step 116, MME replys (Path Switch Request ACK) message to target eNB transmit path transfer request.
Step 117, target eNB are sent to source eNB and are discharged UE context (UE Context Release) message.
Step 118, source eNB discharges the resource that the UE carry out this handoff procedure takies, and deletes the context of this UE.
Fig. 1 agree to admit the switching flow figure under the situation of the UE that carries out current switching in the optimal objective sub-district.In actual handover process, also the situation that the UE that carries out current switching is not admitted in the optimal objective sub-district possibly appear.
If the UE that carries out current switching is not admitted in the optimal objective sub-district; Then manage the target eNB of this optimal objective sub-district and send Handover Preparation Failure message to source eNB; After source eNB receives this Handover Preparation Failure message; Restart handoff preparation phase; Promptly Handover Request message is sent to the alternative target eNB of this Target cell of management then in select target sub-district in satisfying the alternative target cells of judgment condition again, and carries out associative operation according to Handover Request ACK message or Handover Preparation Failure message that this eNB returns.When not admitting the UE of request switching in the optimal objective sub-district, source eNB carries out handoff preparation phase again and has increased time delay for switching.
In addition, after Target cell agree to be admitted this UE, also possibly occur between this UE and Serving cell Radio Link Failure or to the situation of Target cell access failure.
For the situation of the Radio Link Failure between UE and Serving cell, according to present 3GPPTS 36.332 agreements (" Evolved Universal Terrestrial Radio Access (E-UTRA); " Radio Resource Control (RRC) protocol specification " .) regulation; If occur Radio Link Failure in the handoff procedure, then UE carries out wireless link recovery and can only in those have stored the sub-district that eNB managed of context data of this UE, accomplish.
Introduce the detailed process of carrying out wireless link recovery below:
According to present 3GPP TS 36.300 agreements (" Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access (E-UTRAN); Overall description; The regulation that Stage 2 "): if UE detects the Radio Link Failure of this UE and current service cell, then this UE reselects Target cell and carries out wireless link recovery, and the management UE of target eNB through random access procedure of selected Target cell again identifies this UE of authentication; particularly; this target eNB is searched the context that whether stores this UE in this target eNB according to this UE sign, if, then indicate UE to carry out wireless link recovery; if not; then refuse said UE and in this sub-district, recover with the said Target cell of reselecting, this moment, UE possibly need to get into idle (RRC IDLE) state of wireless connections, initiated initial connection procedure again.UE gets into RRC IDLE state and resends initial connection procedure and can increase and carry out time delay for switching.
Usually, after target eNB received the Handover Request message of source eNB, if agree to admit the UE that carries out current switching, then this target eNB was stored the context of this UE.In handoff procedure, because will satisfying the cells of switch decision condition, source eNB do not give this UE, therefore, the target eNB that UE reselects possibly not satisfy the switch decision condition, then can not store the context of this UE in this target eNB of reselecting.According to the flow process of Fig. 1, store the context of this UE among the optimal objective eNB that only active eNB and agreement are switched, therefore, this UE can only carry out wireless link recovery in source eNB and said target eNB.
For the situation of UE to the Target cell access failure; UE need reselect Target cell and insert; If this Target cell of reselecting is not said UE reserved resource or the context of not storing this UE, then said UE can't successfully insert the Target cell that this is reselected.
Visible by such scheme; Switch in the set-up procedure, source eNB selects the optimal objective sub-district from the alternative target cells that satisfies the switch decision condition, only sends Handover Request message to the alternative target eNB of this optimal objective sub-district of management; Triggering this alternative target eNB is current handoff reservation resource; Switch in case this optimal objective sub-district is disagreed with,, also do not store the context of this UE because management is satisfied the unpromising said handoff reservation respective resources of alternative target eNB of the sub-district of switching condition except that this optimal objective sub-district other; Therefore; Source eNB needs to initiate again to switch set-up procedure, promptly need reselect sub-district that another one satisfies judgment condition as new Target cell, sends Handover Request message to the alternative target eNB of this new Target cell of management; And carrying out associative operation according to Handover Request ACK message or Handover Preparation Failure message that this eNB returns, this must increase and carry out time delay for switching.
And when between UE and this Serving cell Serving cell, Radio Link Failure occurring; Because source eNB only sends Handover Request message to the target eNB of management optimal objective sub-district; Trigger this target eNB and carry out switching preparation, therefore, only in source eNB and said optimal objective eNB, store the context of this UE; If this UE has selected the sub-district except that source eNB and other eNB management the said optimal objective eNB when carrying out wireless link recovery; Then wireless link recovery can't normally carry out, and UE possibly be introduced into the RRC_IDLE state, and this can increase and carry out time delay for switching.
Summary of the invention
In view of this, the purpose of the embodiment of the invention is to provide a kind of method that in the LTE system, shortens handover delay, disagrees with the Target cell that reduces current selected and switches the handover delay that causes.
For achieving the above object, the technical scheme of the embodiment of the invention specifically is achieved in that
A kind of method of in Long Term Evolution LTE system, switching, this method comprises:
Source base station eNB satisfies alternative target eNB from the alternative target cells of switch decision condition to all management sends handoff request;
All agree that the affiliated alternative target eNB of alternative target cells of said handoff request reserves the resource of carrying out current switching; And storage carries out the context of user equipment (UE) of said current switching, and said alternative target eNB will agree that all alternative target cells information of said handoff request notify to said source eNB;
Source eNB will agree that the sign of all alternative target cells of said handoff request is carried at and be handed down to the UE that carries out current switching in the switching command;
Said UE agrees that from all switch the selected target sub-district the alternative target cells of said handoff request;
UE and selected target eNB set up in the process of uplink synchronous or target eNB to UE send that uplink synchronous is confirmed and the process of Timing Advance in or UE send in the process of handoff completion message to target eNB; If the situation of UE and the connection failure of Serving cell Radio Link; Then UE reselects Target cell and carries out wireless link recovery from all alternative target cells of agreeing said handoff request; Perhaps if UE to Target cell access failure situation, then UE reselects Target cell and initiates access procedure again from all alternative target cells of agreeing said handoff request.
It is thus clear that; In the embodiment of the invention; Source eNB satisfies alternative target eNB from the alternative target cells of switch decision condition to all management sends handoff request, agrees said handoff request if having in the said alternative target cells of said alternative target eNB management, and then said alternative target eNB reserves the resource of switching; And storage carries out the context of user equipment (UE) of said current switching, and the alternative target cells of agreeing said handoff request is notified to said source eNB.Therefore, the method for the embodiment of the invention can trigger all alternative target eNB and be said handoff reservation resource, carries out switching preparation.Like this; The Target cell of current selected is disagreed with when switching; If reselecting Target cell from the alternative target cells that other agreements are switched, UE switches; Then source eNB does not need to initiate handoff preparation phase again, and the Target cell that has reduced current selected is disagreed with and switched the handover delay that causes.
Description of drawings
Fig. 1 agree to admit the switching flow figure under the situation of the UE that carries out current switching in the optimal objective sub-district;
Fig. 2 is the method flow diagram that in the LTE system, switches that the embodiment of the invention provides;
Fig. 3 is the switching flow figure of UE under selected Target cell access failure situation in the process of in the LTE system, switching.
Embodiment
Core concept of the present invention is that source base station eNB satisfies alternative target eNB from the alternative target cells of switch decision condition to all management sends handoff request; Agree said handoff request if having in the said alternative target cells of said alternative target eNB management; Then said alternative target eNB reserves the resource of carrying out current switching; And storage carries out the context of user equipment (UE) of said current switching, and the alternative target cells of agreeing said handoff request is notified to said source eNB.
For making the object of the invention, technical scheme and advantage clearer, below with reference to the accompanying drawing embodiment that develops simultaneously, to further explain of the present invention.
Fig. 2 is the method flow diagram that in the LTE system, switches that the embodiment of the invention provides, and is of Fig. 2, and this method comprises:
Step 201 is with step 101.
Step 202～step 203 is for the switch decision stage, with step 102～step 103.
In the switch decision stage; Source eNB judges the alternative target cells that satisfies the switch decision condition; Judge alternative target eNB according to the eNB under the alternative target cells that satisfies judgment condition, promptly judge the alternative target eNB that the alternative target cells of switch decision condition is satisfied in management.
Step 204～step 206 is handoff preparation phase.
In handoff preparation phase; Source eNB satisfies alternative target eNB from the alternative target cells of switch decision condition to all management all sends handoff request message; After each alternative target eNB receives said handoff request message, all carry out acceptance judging, when court verdict is to admit the UE that carries out current switching; When promptly agreeing this handoff request; Alternative target eNB sends Handover Request ACK message to source eNB, and reserves the resource of carrying out current switching, the context that the user equipment (UE) of said current switching is carried out in storage, otherwise target eNB is sent Handover Preparation Failure message to source eNB.Wherein, alternative target eNB admits the UE that current request is switched to be meant, the alternative target cells of the UE that agrees that the admittance current request is switched is arranged in the sub-district of this alternative target eNB management.
In Fig. 2, the alternative target eNB that the alternative target cells of switch decision condition is satisfied in management has two, i.e. target eNB 1 and target eNB 2.Facing step 204 and step 206 down describes.
Step 204, source eNB sends Handover Request message to the target eNB 1 that the switch decision stage is judged respectively with target eNB 2.
In this step, carry the sign of alternative target cells in the Handover Request message.If have a plurality of sub-districts to satisfy the switch decision condition in the sub-district that alternative target eNB is managed; Then preferably; Source eNB only sends a Handover Request message to this alternative target eNB; And carry in this handoff request message that this target eNB manages each satisfy the sign of the alternative target cells of switch decision condition; Said sign can be carried at the form of identification list in the said Handover Request message; Certainly, the number of the alternative target cells that satisfies the switch decision condition that source eNB also can be managed according to alternative target eNB all sends HandoverRequest message to alternative target eNB to each said alternative target cells.
Step 205; Target eNB 1 is made acceptance judging with target eNB 2 respectively according to the Handover Request message of receiving separately; And agree to admit the UE that carries out current switching, and when promptly agreeing to carry out said switching, execution in step 206; Otherwise, return Handover Preparation Failure message to source eNB.
Step 206, the alternative target eNB that current switching is carried out in agreement is current handoff reservation resource, and stores the context of the UE that carries out current switching, returns Handover Request ACK message to source eNB.
In this step, agree that the alternative target eNB that carries out current switching is meant the affiliated alternative target eNB of alternative target cells that agrees handoff request.
In Fig. 2, target eNB 1 all agrees to carry out said switching with eNB2, and therefore, target eNB 1 is respectively current handoff reservation resource with eNB2, and returns Handover Request ACK message to source eNB.
Step 207～step 213 is handover execution stage.
In handover execution stage; The sign of the alternative target cells that source eNB on the one hand switches all agreements is carried at issues UE in the switching command, the alternative target eNB of the alternative target cells of agreeing to switch to all management on the other hand transmit Sequence Number state transitions (SN Status Transfer) message, give all said target eNB with the data forwarding of this UE.Wherein, the data of preceding commentaries on classics comprise that high level is issued the new data of this UE, source eNB issues this UE and still do not receive the data of this UE affirmation and the up discontinuous data that UE sends.
In handover execution stage; Switch the corresponding alternative target cells select target sub-district of alternative target cells sign that UE carries from switching command; Set up uplink synchronous with selected Target cell; And behind uplink synchronous affirmation of receiving said Target cell and Timing Advance, notify said selected Target cell to switch and accomplish.
Describe in the face of step 207～step 213 down.
Step 207, source eNB sends switching command to UE, and in this switching command, carries the sign of the alternative target cells of agreeing to switch.
When the number of the alternative target cells of agreeing to switch is two when above, the sign of the alternative target cells that all agreements are switched can be carried in the switching command with the form of identification list.
Step 208, source eNB sends SN Status Transfer message respectively to all alternative target cells, and all carries out data forwarding to all alternative target cells.
Step 209, UE switches according to the sign select target sub-district of the alternative target cells of carrying in the switching command, promptly carries out uplink synchronous with this selected target eNB.If UE and this target eNB have been set up uplink synchronous, then execution in step 210.
In Fig. 2, selected target eNB is a target eNB 1.
Step 210, this selected target eNB 1 are sent uplink synchronous to UE and are confirmed and Timing Advance.
Step 211, UE sends to switch to target eNB 1 and accomplishes (Handover Complete) message, notifies this target eNB to switch and accomplishes.
For step 209～211; If UE and selected target eNB set up in the process of uplink synchronous or target eNB to UE send that uplink synchronous is confirmed and the process of Timing Advance in or UE send in the process of handoff completion message to target eNB; Occurred with the situation of Serving cell Radio Link connection failure or to Target cell access failure situation; Then UE reselects Target cell and carries out wireless link recovery or initiate access procedure again from the corresponding alternative target cells of the entrained alternative target cells sign of switching command tabulation, and concrete switching flow sees also the back literary composition and to the explanation of Fig. 3.
Step 212, this switches the target eNB of accomplishing 1 and sends handover success affirmation (Handover commite) message to source eNB.
Handover commite message in this step is the signaling message that increases newly; The switching that is used for this UE of timely notification source eNB and target eNB 1 is successful; So that source eNB in time notifies other alternative target eNB to be released to this UE reserved resource; Said other alternative target eNB leaves said resource for UE that other need switch, improves the resource utilization of system.
Step 213, source eNB sends handover cancelling (Handover Cancel) message to other alternative target eNB.
In this step; Source eNB is through sending Handover Cancel message to other alternative target eNB; The resource of in time notifying other alternative target eNB to be released to current handoff reservation is left resource for UE that other need switch or insert, improves the resource utilization of system.
Other alternative target eNB among Fig. 2 is a target eNB 2, and target eNB 2 is released to this UE reserved resource after receiving Handover Cancel message.
Step 214～step 220 is for switching the completion stage, identical with step 112～step 118.
It is thus clear that; Handoff preparation phase in flow process shown in Figure 2 is promptly in step 204～step 206, because source eNB all sends Handover Request message to all alternative target eNB; And each alternative target eNB makes acceptance judging according to the Handover Request message of receiving separately respectively; And when agreeing to switch, send Handover Request ACK message to source eNB, therefore; In the switch decision stage; Only need experience one to take turns the time of " send Handover Request ACK message-carry out acceptance judging-return Handover Request ACK or Handover Preparation Failure message ", source eNB just can learn the alternative target cells that all agreements are switched, and then judges all alternative target eNB.In handoff preparation phase shown in Figure 1; Source eNB only sends handoff request message to a target eNB; When disagreeing with in this target eNB when switching; Send handoff request message to the another one target eNB again and compare, can shorten owing to the target eNB of current selection is disagreed with and switched the handover delay that causes.
In step 208; Source eNB to all alternative target eNB all before the data of the said UE of commentaries on classics, therefore, the data that source eNB needn't the said UE of buffer memory; Can guarantee if cause needs to change target eNB to a certain target eNB handoff failure; The switching that the target eNB of said UE after changing carried out is the switching that can't harm, and the data of said UE are not lost after promptly guaranteeing to switch, and this has saved the spatial cache of source eNB on the one hand; Also avoided on the other hand owing to the forwarding data that handoff failure causes is lost, the data of UE are complete after having guaranteed to switch.
Through step 212～213, can also further improve resource utilization ratio.Wherein, the Handover commite message of step 212 is the signaling messages that increase newly.Target eNB through the current UE that switches of the timely notification source eNB of Handover commite message in the step 212 successful switch on this target eNB; Source eNB is through the Handover Cancel message in the step 213; In time notify other alternative target eNB to be released to this UE reserved resource; So that said other alternative target eNB leaves resource for UE that other need switch or newly insert, improve the resource utilization of system.
Also can not increase the Handover commite message in the step 212; In this case, direct execution in step 214～219 after step 210 is after the execution of step 219; Promptly after source eNB receives the message of the release resource that the target eNB of handover success is sent; Source eNB discharges the resource that this UE takies on the one hand in the eNB of this source, agree that to other alternative target eNB that switches sends Handover Cancel message on the other hand, after said other agree that the alternative target eNB that switches receives this Handover Cancel message; Be released to the resource that this UE carries out handoff reservation, the context of this UE that deletion is preserved.But it is late than last method that this method makes that other alternative target eNB that agree to switch are released to the related resource that UE reserves, and can make resource utilization decline.
In addition; Between step 207～step 211, (do not comprise step 207 and step 211); If the Radio Link Failure of UE and Serving cell, then UE can be according to the identification list of the Target cell that carries in the switching command, and wireless link recovery is carried out in the select target sub-district; If carry out the wireless link recovery success with selected Target cell, then UE has promptly switched on the successful Target cell of this wireless link recovery.
What the process of wireless link recovery of carrying out UE and selected Target cell adopted is RRC connection reconstruction flow process, and particularly, this flow process comprises:
Step 1 only is with the difference of step 209, and UE is different to the uplink synchronous code that said selected Target cell sends.
Step 2 is with step 210.
Step 3, the target eNB of UE under said selected Target cell are sent and are rebuild request message.
Step 4, said target eNB is returned reconstruction message to said UE.
Step 5, UE returns to rebuild to said target eNB and accomplishes message.
Said target eNB is after receiving that message is accomplished in said reconstruction; Can return one to the source of said UE eNB and rebuild successful affirmation message; The affirmation message that this reconstruction is successful is equivalent to the Handover commite message in the step 212; The Radio Link reconstruction that is used for said UE of notification source eNB and said Target cell is successful, and source eNB can notify other target eNB to be released to this UE reserved resource then, and deletes the context of this UE.Source eNB receives that step 212 flow process (not comprising step 212) afterwards is identical among said flow process and Fig. 2 that rebuilds after the successful affirmation message.
Said target eNB is after receiving that message is accomplished in said reconstruction; Also can not return and rebuild successful affirmation message to the source of said UE eNB; But direct execution in step 214～219; After the execution of step 219, source eNB agrees that to other alternative target eNB that switches sends Handover Cancel message again.
In the method for carrying out wireless link recovery among the present invention and the prior art can only with source eNB or optimal objective eNB in carry out wireless link recovery method compare; Increased the choice of UE selection carrying out wireless link recovery, reduced owing to carrying out the probability that wireless link recovery causes that handover delay increases.
In addition; The sign of the Target cell that source eNB switches all agreements all is carried at and is handed down to UE in the switching command; This UE switches the select target sub-district from the alternative target cells that said agreement is switched; Promptly insert selected Target cell, if UE in the process that inserts selected Target cell, UE is to said selected Target cell access failure; Because the alternative target eNB that all agreements are switched has all reserved the context that carries out the resource of current switching and stored this UE for this UE in handoff preparation phase; Therefore, this UE can also reselect Target cell and insert according to the sign of the alternative target cells of carrying in the switching command.
Switching flow in the process of UE and target eNB being switched below in conjunction with Fig. 3 under selected Target cell access failure situation is elaborated.
Fig. 3 is the switching flow figure of UE under selected target eNB access failure situation in the process of in the LTE system, switching, and as shown in Figure 3, this flow process specifically comprises:
Step 301～step 308 is with step 201～step 208.
Step 309; UE is to target eNB 1 access failure, and then UE can be to the another one target eNB, and promptly target eNB 2 is set up wireless connections; Particularly; UE and target eNB 2 are set up uplink synchronous, and target eNB 2 is returned uplink synchronous acknowledge message and Timing Advance to this UE then, and UE returns to target eNB 2 and switches the message of accomplishing then.
In Fig. 3, UE with target eNB 1 carry out access failure after, be connected with the Radio Link of target eNB 2 and set up successfully.
Step 310～step 318 only is that with the difference of step 212～step 220 target eNB of handover success becomes target eNB 2 by target eNB 1.
Among Fig. 3; Because in handoff preparation phase, promptly in step 304～306, source eNB triggers all management agreements and carries out the context that the alternative target eNB of the alternative target cells of current switching is said handoff reservation resource, stores the UE that carries out current switching; And the sign that the alternative target cells of current switching is carried out in said agreement is handed down to UE; Therefore, when the Target cell access failure that UE selects, this UE can reselect target eNB and insert from all alternative target eNB.
Visible by technique scheme, the method for the embodiment of the invention can trigger all alternative target eNB and be said handoff reservation resource, carries out switching preparation.Like this; Disagree with in the target eNB of current selected and to switch; If reselecting target eNB from the alternative target eNB that other agreements are switched, UE switches; Then source eNB does not need to initiate handoff preparation phase again, and the target eNB that has reduced current selected is disagreed with and switched the handover delay that causes.
The above is merely preferred embodiment of the present invention, is not to be used to limit protection scope of the present invention, all any modifications of within spirit of the present invention and principle, being made, is equal to replacement, improvement etc., all should be included within protection scope of the present invention.
Claims (6)
1. method that in Long Term Evolution LTE system, shortens handover delay is characterized in that this method comprises:
Source base station eNB satisfies alternative target eNB from the alternative target cells of switch decision condition to all management sends handoff request;
All agree that the affiliated alternative target eNB of alternative target cells of said handoff request reserves the resource of carrying out current switching; And storage carries out the context of user equipment (UE) of said current switching, and said alternative target eNB will agree that all alternative target cells information of said handoff request notify to said source eNB;
Source eNB will agree that the sign of all alternative target cells of said handoff request is carried at and be handed down to the UE that carries out current switching in the switching command;
Said UE agrees that from all switch the selected target sub-district the alternative target cells of said handoff request;
UE and selected target eNB set up in the process of uplink synchronous or target eNB to UE send that uplink synchronous is confirmed and the process of Timing Advance in or UE send in the process of handoff completion message to target eNB; If the situation of UE and the connection failure of Serving cell Radio Link, then UE reselects Target cell and carries out wireless link recovery from all alternative target cells of agreeing said handoff request;
Perhaps if the situation of UE to the Target cell access failure, then UE reselects Target cell and initiates access procedure again from all alternative target cells of agreeing said handoff request.
2. the method for claim 1 is characterized in that,
If the number of the alternative target cells that satisfies the switch decision condition of alternative target eNB management is more than two, then source eNB carries the tabulation of sign of the alternative target cells that satisfies the switch decision condition of said alternative target eNB management in said handoff request.
3. the method for claim 1 is characterized in that, the sign of all alternative target cells of agreeing said handoff request is carried at is handed down in the switching command after the UE that carries out current switching, further comprises:
Source eNB changes said UE before the alternative target eNB of the alternative target cells of the said handoff request of all management agreements data.
4. the method for claim 1 is characterized in that, UE is after switch the selected target sub-district from all alternative target cells of agreeing said handoff request, and this method further comprises:
The target eNB of managing said selected Target cell is sent to source eNB and to be confirmed the completed message of said switching after said switching is accomplished;
After source eNB received the completed message of the said switching of said affirmation, the alternative target eNB of notice except that the target eNB of sending the completed message of the said switching of said affirmation was released to the resource of said current handoff reservation.
5. the method for claim 1 is characterized in that, said carrying out after the wireless link recovery, and this method further comprises:
UE manages the target eNB of said selected Target cell again and sends the successful affirmation message of reconstruction to source eNB after said selected again Target cell carries out the wireless link recovery success;
After source eNB received the successful affirmation message of said reconstruction, the alternative target eNB of notice except that the target eNB of the said selected Target cell again of management was released to said UE reserved resource.
6. the method for claim 1 is characterized in that, said alternative target eNB will agree that the alternative target cells information of said handoff request is notified to said source eNB and be:
Said alternative target eNB will agree that the alternative target cells information of said handoff request is carried in the handoff request acknowledgment message notice and gives said source eNB.
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| WO2018205965A1 (en) * | 2017-05-10 | 2018-11-15 | 华为技术有限公司 | Cell switching method, terminal, base station device and communication system |
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| WO2018205965A1 (en) * | 2017-05-10 | 2018-11-15 | 华为技术有限公司 | Cell switching method, terminal, base station device and communication system |
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