CN104602276B

CN104602276B - The adaptive optimization method that a kind of eSRVCC handoff parameters are set

Info

Publication number: CN104602276B
Application number: CN201410827291.1A
Authority: CN
Inventors: 费泽松; 苑婷婷; 邢成文; 匡镜明
Original assignee: Beijing Institute of Technology BIT
Current assignee: Beijing Institute of Technology BIT
Priority date: 2014-12-25
Filing date: 2014-12-25
Publication date: 2018-01-16
Anticipated expiration: 2034-12-25
Also published as: CN104602276A

Abstract

The present invention relates to the adaptive optimization scheme that a kind of eSRVCC handoff parameters are set, belong to wireless communication technology field.The inventive method includes herein below：1. in the handover measurement stage, the trigger condition that measurement event reports adaptively is adjusted according to the CQI indexs of channel, effectively avoids ping-pong.2nd, in switch decision stage, the judgment condition switched according to the real-time adjustment of the priority of user setting, so as to improve the flexibility of eSRVCC switchings.Specifically, optimize hysteresis auto-adaptive parameter amendment in handover triggering condition by measuring the CQI of channel first, then the method that the situation of handover request proposes priority design is initiated simultaneously for multi-user, finally the user UE for selected optimal objective cell completes to be switched to Target cell from cell-of-origin.Prior art is contrasted, the inventive method can adjust the setting of handoff parameter in real time according to the quality of channel, provide the user the call experience of more preferable seamless switching, be more applicable for existing network environment.

Description

The adaptive optimization method that a kind of eSRVCC handoff parameters are set

Technical field：

The present invention relates to the adaptive optimization method that a kind of eSRVCC handoff parameters are set, and belongs to wireless communication technology neck Domain.

Background technology：

With the continuous development of mobile communication technology, network is for Long Term Evolution (Long Term Evolution, LTE) Commercial stage is stepped into, and in numerous business that LTE system provides, speech business is still most basic most important business. When LTE network large scale deployment, mobile operator will face LTE and second generation mobile communication system/third generation movement is logical The situation of the multiple network long-term co-existence such as letter system (Second Generation/Third Generation, 2G/3G), therefore How a weight that speech business continuity LTE and 2G/3G network between be current industrial circle and academia research is kept Want problem.To solve this problem third generation partner program (3rd Generation Partnership Project, 3GPP) normal structure proposes a solution, i.e. single wireless voice calling continuity technology (Single Radio Voice Call Continuity, SRVCC).

The target for the LTE voice service systems switching that SRVCC technologies are unanimously approved as industry provides scheme and is primarily referred to as In LTE covering boundary, the voice in IP multimedia subsystem (IP Multimedia Subsystem, IMS) domain will be anchored on Calling, switch the circuit domain (Circuit of 2G/3G systems from packet switch (Packet Switch) domain of LTE system Switch, CS).Yet with the complexity of handover scheme in SRVCC schemes, its performance of handoffs is less desirable, major embodiment Two aspects：First, time delay caused by switching can not still meet the condition for being less than 300ms as defined in 3GPP, especially at user In the case of roaming state；Second, the success rate of switching is not high, the performance of SRVCC switchings depends on distal end renewal journey Sequence.The shortcomings that these two aspects make under most of scenes, the performance of SRVCC switchings can not meet requirement, therefore various Prioritization scheme arises at the historic moment.A comprehensive scheme has finally been formulated in the standards of 3GPP TS 23.865, i.e., " has been based on SIP (meetings Talk about initializtion protocol, Session Initiation Protocol) eSRVCC (enhanced SRVCC, Enhanced SRVCC) Scheme " (hereinafter referred to as eSRVCC schemes).

ESRVCC main thought is exactly that voip call is anchored on into an IMS network element close to network where calling subscribe On, only need to change calling subscribe to the branch road between anchor point without changing anchor point so when Session Hand-off To the branch road between remote subscriber to shorten the time delay of Session Hand-off.The system architecture of eSRVCC handover schemes as shown in Figure 1, The program has increased two functional entitys newly in IMS systems：Access transfer control function (Access Transfer Control Functionality, ATCF) and access transfer gateway (Access Transfer Gateway, ATGW).ATCF and ATGW points Not as audio call in control plane and the anchor point of user plane.ESRVCC schemes by avoiding the renewal of distant end media, Handover delay is effectively reduced, improves the performance of switching.But in order to provide the user with the call body being preferably seamlessly connected Test, it is also necessary to which existing handover scheme is optimized and improved.

Optimization of the industry to eSRVCC technologies at present is most in the optimization analysis of signaling process, and for handoff parameter Optimization is not studied also.In existing different system switching, handover triggering condition has two kinds：First, other wireless access technologys (Radio Access Technology, RAT) adjacent cell becomes better than thresholding；Another kind is that serving cell becomes than thresholding 1 more Difference, adjacent cell becomes more preferable than thresholding 2 between RAT.The threshold value of switching and sluggish value parameter are all by base station fixed configurations, nothing Different channels environment of the method according to residing for user is modified, so will result in produced in communication process it is non-essential switching or Switching is not in time.Such as UE pingpang handoffs can be caused due to signal jitter when threshold value setting is too low, and when threshold value is too high It can shine again into switching not in time.

The content of the invention:

The purpose of the present invention is immobilized to solve base station switches in existing eSRVCC threshold value and sluggish value parameter A kind of caused non-essential the problem of switching or switching not in time, it is proposed that the adaptive optimization that eSRVCC handoff parameters are set Scheme, the CQI by measuring channel optimize hysteresis auto-adaptive parameter amendment in handover triggering condition, and for multi-user simultaneously The method that the situation of handover request proposes priority design is initiated, so as to ensure that the validity of eSRVCC handoff algorithms and spirit Activity, and the more preferable experience for being seamlessly connected call has been provided the user, it is more applicable for existing network environment.

To achieve these goals, the present invention is achieved through the following technical solutions：

The adaptive optimization method that a kind of eSRVCC handoff parameters are set, comprises the following steps：

Step 1, handover measurement stage, user trigger reporting measurement reports to base station according to certain criterion, sentenced for switching Certainly prepare.

Before user equipment (User Equipment, UE) carries out eSRVCC switchings, base station (eNodeB) is sent to UE Measurement request, mainly transmitted by RRC connections reconfiguration message, as shown in Figure 2.UE carries out relevant parameter according to measurement request Measurement, when the result of measurement meets report reporting trigger conditions, UE will be to eNodeB report measurement results.Above-mentioned thing Part trigger condition is that auto-adaptive parameter based on CQI proposed in the present invention sets algorithm, including entry condition and is left Condition.

Wherein, Ms is the measurement result of serving cell, does not consider the amount of bias of any cell.Mn is RAT adjacent cell measurements Result, Ofn is the specific frequency offset amount of RAT adjacent cell frequencies, and Hys is the hysteresis of the event, and its span is 0 to arrive 30 integer, Thresh1 and Thresh2 are the absolute threshold values of measured value, and its parameter type is consistent with Ms and Mn respectively； If Ms, Mn are Reference Signal Received Power (Reference Signal ReceivingPower, RSRP), then Thresh1, Thresh2 unit is dBm；If Ms, Mn are Reference Signal Received Quality (Reference Signal Receiving Quality, RSRQ), then Thresh1/Thresh2 unit is dB；σ 1, σ 2 are the parameters related to the CQI value of present channel, Change with CQI change, its main purpose is to carry out adaptive amendment to the threshold value of switching.

CQI is the measurement standard of eless channel communication quality, and CQI is that UE measures according to downlink reference signal, is indicated The quality of down channel, and pass through Physical Uplink Control Channel/Physical Uplink Shared Channel (Physical Uplink Control Channel/Physical Uplink Shared Channel, PUCCH/PUSCH) it is sent to eNodeB.CQI's Span is 0~16, and CQI value is bigger, and explanation channel quality is better, and vice versa.If when the CQI in the previous period is equal When CQI averages in value upper period are high, σ value should be reduced to reduce user's incision or increase user cuts out door Limit value.If when the CQI averages in the upper period of the CQI averages in the previous period are low, should increase σ value with Increase user incision reduces the threshold value that user cuts out.Reached in the present invention program by the real-time adjustment to σ to Thresh Carry out the effect of adaptive correction.

Step 2, the switch decision stage, eNodeB is that user selects an optimal Target cell incision, as multiple users When initiating handover request simultaneously, eNodeB determines the transfer sequence of different user according to the priority size of user.

When the measurement report that UE measurement result meets in step 1 reports trigger condition, eNodeB will receive UE hairs The measurement report sent, and therefrom extract the information required for switch decision.Please if the same time only has a user to initiate switching Ask, then eNodeB need not consider the issue of priority of user, the target cell information directly in measurement report, choose quality Optimal cell is as Target cell, then start flow, into handover execution stage.But there ought be multiple users simultaneously to same During individual eNodeB initiations handover request, situation about being competed between user will be produced, at this moment needs eNodeB to formulate as needed accordingly Criterion to calculate the priority of user, and a user list, priority treatment priority are constructed with the priority height of user Highest user asks, and deletes the user after the completion of processing in user list, and handles the handover request of subsequent user successively.

Step 3, handover execution stage, after selected target cell, eNodeB initiates switching flow, realizes UE is small from source Area is switched to Target cell.

After eNodeB completes the switch decision in step 2, eNodeB is that UE selects an optimal Target cell to carry out Incision, the flow of different systems switching is then initiated, UE is completed from LTE system to the handoff procedure of 2G/3G systems, so as to keep Call is normally carried out.After UE completes eSRVCC handoff procedures, LTE system will be discharged shared by the user speech service bearer Resource, prepared for the accesses of other users.

Brief description of the drawings

Fig. 1 is eSRVCC system architecture schematic diagrams；

Fig. 2 is the adaptive optimization method schematic flow sheet that handoff parameter of the embodiment of the present invention is set；

Fig. 3 is eSRVCC handover scheme signaling process schematic diagrames of the embodiment of the present invention；

Fig. 4 is switching flow schematic diagrames of the UE of the embodiment of the present invention from former cell to Target cell.

Embodiment

To make the purpose of invention, technical scheme and advantage become apparent from, below by be switched to 2G domains from LTE domains Exemplified by eSRVCC handover schemes, and the present invention is described in further details with reference to accompanying drawing.The present embodiment is with the technology of the present invention Implemented under premised on scheme, give detailed embodiment and specific operating process, but protection scope of the present invention It is not limited to following embodiments.

The present embodiment is switched to global system for mobile communications (Global System for audio call from LTE domains Mobile Communications, GSM) process of eSRVCC switchings is described in detail exemplified by domain, and to institute in the present invention program The measurement reported event trigger condition and priority policy of proposition are described in detail.It is attached when audio call is switched to GSM domains Target BS in Fig. 1 is the base station sub-system (Base Station Subsystem, BSS) of gsm system including base Stand transceiver and base station controller two parts.I/S-CSCF (Interrogating/Serving Call in accompanying drawing 1 Session Control Function, inquiry/service call conversation control function) and SCC AS (Service Centralization and Continuity Application Server, service-conformance and continuity application service Device) be IMS domain two network elements, to support eSRVCC switch completion.MSC Server(Mobile Swith Center Server, Mobile Switching Center Server) be eSRVCC switching key network element, its interface Sv between mobile management entity Realization to eSRVCC technologies serves critical.As shown in figure 4, the present embodiment comprises the following steps that：

Step 1, after UE1 receives the measurement request that eNodeB is issued, measured by its requirement, and meeting to trigger bar Reporting measurement reports are to eNodeB during part.

As shown in Figure 2, before eSRVCC switchings are carried out, eNodeB is sent out UE1 by RRC connection reconfiguration messages to UE1 Measurement request is sent, the parameter that UE1 needs to measure according to specified in measurement request measures, when the result of measurement meets measurement During report triggering conditions, UE1 is to eNodeB report measurement results.Measurement result meets trigger conditions also while illustrated UE1 audio call needs to switch over to GSM domains, and now the LTE cells where UE1 can not meet the need of its speech quality Ask.In the present embodiment, the major parameter Ms values of switching are RSRQ, and Mn values indicate for reference signal receiving intensity (Reference Signal Strength Indication, RSSI), i.e. UE is according in the LTE system cell currently measured The RSSI value of cell decides whether to meet handover event trigger condition in RSRQ values and gsm system, and eNodeB will be according to GSM The RSSI of cell comes selection target switching cell.Therefore, handover event trigger condition is represented by：

Wherein, RSRQ_src is the RSRQ values of UE1 current service cells, and RSRQ_thr is entering for UE1 current service cells The threshold value for entering and leaving, RSSI_des are the current RSSI values in target GSM cell, and RSSI_thr is entering for target GSM cell The threshold value for entering and leaving；σ 1 and σ 2 is the threshold value corrected parameter adaptively adjusted with current CQI value.

CQI value in the present embodiment, which obtains, to be obtained in the form of periodically reporting, and UE1 passes through PUCCH channel cycles The feedback CQI of property value is to eNodeB.ENodeB adjusts σ 1 and σ 2 according to the CQI of feedback value.Due to terminal have it is various The feature of change, unification is not easy to, and base station is that have by operator's unified plan, therefore in the amendment of eNodeB sides completion parameter There is higher practicality.The CQI communication quality for being sized to reflect wireless channel, therefore according to the adaptive tune of CQI value Whole σ 1 and σ 2 value are so as to realizing the amendment of handoff threshold value so that handover triggering condition is flexible by the change according to channel Adjustment.When CQI average increases, illustrate channel quality become it is more preferable, at this moment by reduce σ 1 and σ 2 value so that More users' rests on current area, provides the user preferable Quality of experience.Equally, when channel CQI value reduces, say Bright channel quality is deteriorated, at this moment should by increasing σ 1 and σ 2 value so that user be difficult incision current area simultaneously The condition of current area is lowered from, is that the more preferable cell of user's selection is its service.

Step 2, after eNodeB receives UE1 measurement report, the relevant parameter in measurement report is user's selection one Individual optimal Target cell is cut.

After eNodeB receives the measurement report that UE1 is reported, therefrom extraction switches related all parameter informations.If now Only mono- user of UE1 asks eSRVCC switchings, then eNodeB selects one directly from the target GSM cell in measurement report The optimal cell of communication quality provides service as Target cell for UE1, and then UE1 completes follow-up according to eNodeB decision-making ESRVCC switching flows.If while UE1 initiates handover request, there are other users also to initiate eSRVCC under same eNodeB Handover request, then eNodeB need first determine user switching priority, then according to priority determine processing user switching Sequencing.In the present embodiment, its priority can be determined according to the RSRP values that user is currently received, and according to The priority at family constructs a user list.Such as instruction manual relatively low RSRP its current performance number that can be received compared with Low, it is poor to can be obtained speech quality experience, therefore should improve its priority, row major switching is entered to the user, prevents from using The situation of call drop occurs in the communication process of family.After the completion of the handover request processing of a user, eNodeB will be in user list Middle deletion user, and the handover request of subsequent user is handled according to this.

Step 3, after eNodeB is UE1 selected target cells, eNodeB initiates follow-up switching flow, realize UE1 from Cell-of-origin is switched to Target cell.

After eNodeB completes the switch decision in step 2, eNodeB have selected an optimal Target cell for UE1 and enter Row incision, then initiates eSRVCC switching flows, i.e. handover request is sent to mobile management entity (Mobile by eNodeB first Management Entity, MME) in (4)；Then MME isolates voice bearer from non-voice carrying, and to MSC Server initiates the order (5~6) of PS to CS switchings；Then established between MSC Server and target MSC circuit connection (7~ 10) and to source eNodeB switching command (17~19) is sent；Carry out IMS handoff procedures in the ims domain simultaneously and include distant end media Renewal and Session Hand-off (11~16)；UE1 performs handoff procedure after the completion of the switching eated dishes without rice or wine and IMS switchings all, completes from source Switching (19~21) of the cell to Target cell.UE1 is switched to the eSRVCC switchings of GSM cell from the LTE cells of current service Signaling process is as shown in Figure 3.Whole handoff procedure is gone back except the handover measurement in step 1 and step 2 and in addition to the switch decision stage There is switching to prepare, switching performs and switching post processing three phases.Wherein influence of the handoff preparation phase to performance of handoffs is main If being embodied in the overlong time in the stage, user may cause call drop handover execution stage due to leaving the area of coverage or other reasonses ESRVCC handover delay and handover success rate mainly are affected, and switches post-processing stages and relates generally to LTE after the completion of switching The resource release process in domain.Present invention relates generally to handover measurement and switch decision stage, the two stages are to determine one User whether the critical stage that can be switched over, therefore, the content present invention of follow-up phase is not described in detail.

The inventive method adjusts handover triggering condition in real time by cqi CQI value, and in switch decision During introduce priority concept so that eSRVCC switching can be carried out flexibly, be effectively guaranteed the seamless company of user The call experience connect.

Above-described specific descriptions, the purpose, technical scheme and beneficial effect of invention are carried out further specifically It is bright, it should be understood that the specific embodiment that the foregoing is only the present invention, the protection model being not intended to limit the present invention Enclose, within the spirit and principles of the invention, any modification, equivalent substitution and improvements done etc., should be included in the present invention Protection domain within.

Claims

A kind of 1. adaptive optimization method that eSRVCC handoff parameters are set, it is characterised in that：Comprise the following steps：

Step 1: the handover measurement stage, user triggers reporting measurement reports to base station according to certain criterion, is done for switch decision Prepare；The criterion sets algorithm for the auto-adaptive parameter based on CQI, including entry condition and leaves condition：

Wherein, Ms is the measurement result of serving cell；Mn is the result of RAT adjacent cell measurements；Ofn is RAT adjacent cell frequencies Specific frequency offset amount；Hys is hysteresis, and its span is 0 to 30 integer；Thresh1 and Thresh2 is measured value Absolute threshold value, its parameter type are consistent with Ms and Mn respectively；σ 1, σ 2 are the communication quality CQI value phases with present channel The parameter of pass, changes with CQI change, and its main purpose is to carry out adaptive amendment to the threshold value of switching；

Step 2: the switch decision stage, base station is that user selects an optimal Target cell incision, when simultaneously multiple users send out When playing handover request, handled according to the priority order from high to low of user；

Step 3: handover execution stage, after selected target cell, switching flow is initiated in base station, realizes and cuts UE from cell-of-origin Change to Target cell.
2. the adaptive optimization method that a kind of eSRVCC handoff parameters according to claim 1 are set, it is characterised in that：Institute The span for stating CQI is 0~16, and CQI value is bigger, and explanation channel quality is better, and vice versa.
3. the adaptive optimization method that a kind of eSRVCC handoff parameters according to claim 1 are set, it is characterised in that：Institute State σ 1 and σ 2 changes with CQI change, its Adjustment principle is：If when the CQI averages in the previous period are upper one Between CQI averages in section it is high when, σ 1 and σ 2 value should be reduced to reduce user's incision or increase user cuts out threshold value；If When the CQI averages in the upper period of the CQI averages in the previous period are low, σ 1 and σ 2 value should be increased to increase User is added to cut or reduce the threshold value that user cuts out.
4. the adaptive optimization method that a kind of eSRVCC handoff parameters according to claim 3 are set, it is characterised in that：Institute The adjustment for stating σ 1 and σ 2 is completed in base station, and CQI value is periodically reported base station by user.
5. the adaptive optimization method set according to a kind of any described eSRVCC handoff parameters of claim 1-4, its feature It is：One optimal Target cell of the selection is that base station is selected from the target GSM cell in the measurement report of reporting of user Select an optimal cell of communication quality.
6. a kind of audio call is switched to the adaptive excellent of global system for mobile communications domain eSRVCC handoff parameters setting from LTE domains Change method, it is characterised in that：Comprise the following steps：

Step 1: after user UE1 receives the measurement request that base station eNodeB issues, measure, and meeting by its requirement Reporting measurement reports are to eNodeB during trigger condition；The trigger condition is：

Wherein, RSRQ_src is the RSRQ values of UE1 current service cells, RSRQ_thr be UE1 current service cells entrance and The threshold value left, RSSI_des are the current RSSI values in target GSM cell, RSSI_thr be target GSM cell entrance and The threshold value left；σ 1 and σ 2 is the threshold value corrected parameter adaptively adjusted with current CQI value；

Step 2: after eNodeB receives UE1 measurement report, the relevant parameter in measurement report selects one most for user Excellent Target cell is cut；When multiple users initiate handover request simultaneously, then eNodeB determines user's switching first Priority, the sequencing of processing user's switching is then determined according to priority；Priority is currently received according to user RSRP values determine that RSRP values are lower, and its priority is higher, i.e., priority has the backward that high to Low order is user's RSRP values；

Step 3: after eNodeB is UE1 selected target cells, eNodeB initiates follow-up switching flow, realizes that UE1 is small from source Area is switched to Target cell.
7. a kind of audio call according to claim 6 is switched to global system for mobile communications domain eSRVCC from LTE domains and cut Change the adaptive optimization method of parameter setting, it is characterised in that：ENodeB issues survey by RRC connection reconfiguration messages to UE1 Amount requires.