tdscdma handover method and timedelay performance analysis chen

1、TD-SCDMA Handover Method and Time-Delay Performance Analysis （MII Key Lab of Mobile Communications Technology, Chongqing University of Posts and Telecommunications）Abstract：Baton Handover is the very important part of TD-SCDMA system. But because of the faultiness and other reasons, The Baton Handov

2、er has not been realized at the real network. Now we use a handover technology based on Hard Handover but still keep some Baton Handover features. This handover method can shorten the handover time-delay and reduce the signal interaction complexity. This article analyzes the handover time-delay perf

3、ormance of this handover mode. Keywords：Baton Handover Hard Handover Handover Time-Delay Interruption TimeRRC Procedure Performance Parameter1 Baton Handover Transformed From Hard Handover Baton Handover Realization DifficultyBaton handover has a great demand for the equipment and system. then it is

4、 very difficult to be realized. Baton handover requires the source cell to acquire the UE location, frequency, short code, downlink transmission timing deviation, and busy-idle state indicator that belong to adjacent cell and other system cell. It increases the signal complexity and UE measurement l

5、oad greatly. UE should have more than one transmitter and receiver on demand, so it can receive two downlinks of the source cell and destination cell simultaneous. And the UE should have the ability that switches 3-4 times between inter-frequency cells in 5ms subframe on demand. These requirements f

6、or UE and system can't be contented .So the baton handover can't be realized now .A new baton handover method which has the primary baton handover features and is based on the hard handover is proposed by this paper. This method reduces the signal interaction and lower the demand for UE and

7、system.1.2 Modify Hard Handover to Baton HandoverBecause the baton handover requires the UE to keep two downlinks of the two cell simultaneous at the handover time ,and the realization of signal is very difficult ,so a new handover method based hard handover is propose. This method reduces the acces

8、s synchronization time and has modified some hard handover below steps:1 For the handover between intra-frequency and synchronous cells ,after UE has received the RRC Physical Channel Reconfiguration message, UE should have have access to the destination cell by using allocated DCH without the uplin

9、k and downlink synchronization procedure.2 For the handover between inter-frequency and asynchronous cells, after the UE has received the RRC Physical Channel Reconfiguration message, UE should have access to the destination cell after uplink synchronous procedure without downlink synchronization pr

10、ocedure because the Physical Channel Reconfiguration message has gave the UE destination cells SYNC_DL,MIDAMBLE.etc.3 This method's realization is based on the UE precious location technology by using Smart Antenna2 Handover Between Synchronization TD-SCDMA Cells Time-delay AnalysisThe synchrono

11、us TD-SCDMA systems means the source and destination cells keep frame synchronization and the UE can directly have access to the destination cell without downlink and uplink synchronous procedure at handover time. Because of the lack of synchronization procedure, this types handover time-delay is th

12、e smallest delay among all TD-SCDMA systems handover types. The main used RRC handover command is the Physical Channel Reconfiguration, this command has included the spreading code ,MIDAMBLE, occupied timeslots of destination cell, etc. UE Measurement Reporting TimeBaton handover time i.e. the time

13、between the time UE starts reporting the measurement result and the time handover completion. It means handover time-delay is made of two parts. One is the time that UE reporting measurement result The other is the handover signal time-delay. The UE measurement reporting time includes these parts:1M

14、esurement reporting uncertain time t1t1 results from inserting the measurement report to the TTI of the uplink DCCH ,The delay uncertainty is twice the TTI of the uplink DCCH. The TTI of DCCH is equal to 40ms,so the t1=80ms.2Event triggered measurement reporting time t2The t2 is defined as the time

15、between any event that will trigger a measurement report, until the UE starts to transmit the measurement report over the Uu interface. This requirement assumes that the measurement report is not delayed by other RRC signaling on the DCCH.the t2 should be less than the new cell detection time .（acco

16、rding to 3GPP TR 25.123 and ）According to the 3GPP TR 25.123 .2.2.1,The new intra-frequency cell detection time is:TMeasurement_Period, Intra 200ms，it is the PCCPCH RSCP measurement period;NPeriod,Intra 40，the number of subframes in the PCCPCH RSCP measurement period.Tbasic_identify_TDD, intra 800ms

17、；NIntra is the minimum number of sub-frame in that the period of TS0, DwPTS and main guard period is available for intra frequency measurements, during the measurement period.Here, we assume that there are 40 subframes to be used in new cell detection procedure in 200ms.Accroding to above formula, t

18、he minim new cell detection time is 800ms. According to 3GPP TR 25.123 .2.3.1,the new inter-frequency cell detection time is :Tbasic_identify_TDD,inter 800ms；Nbasic identify TDD, Inter 160ms，the number of subframes in Tbasic_identify_TDD,interNInter is the minimum number of sub-frame in that the sig

19、nal of P-CCPCH and DwPCH can be received for inter frequency target cell during the period TMeasurement_Period inter with an arbitrarily chosen timing. we assume that UE can use all 800ms to detect the new cell, so the value is 800/5=160ms.NFreq Is the TDD frequency number given by measurement contr

20、ol message. This article assume the inter-frequency neighbor cell number is 1.According to above formula, the mimum inter-frequency and intra-frequency cell detection time is either 800ms.then,so the t2 is 800ms.3 L3 filtering time-delay t3This time is related to filter coefficient k included in the

21、 measurement control command. According to the analysis of WCDMA system, the filtering time is 200ms when k is 2.In view of little UE measurement performance difference between TD-SCDMA and WCDMA system , the TD-SCDMA systems t3 is approximately equal to WCDMA systems. The total UE measurements repo

22、rting time T<= t1+t2+t3=1080ms.Notes: The measurement reporting time is main parts of the total handover time-delay. difference UE has difference time. but totally should be less that 1080ms. 2.2 Signal Time-delay Analysis Signal time-delay is made of two parts: RRC procedure parameter and interr

23、uption time.For the handover between synchronous cell, the UE can directly have access to target cell without any synchronization procedure after UE has received the Physical Channel Reconfiguration. This handover time exclude the synchronization time. RRC Procedure ParameterRRC procedure parameter

24、is defined as the time that system completes the Physcial Channel Reconfiguration procedure . This value is analyzed at 3.3 section .the difference from the asynchronous system is that the time-delay is equal to N1+N2.The uplink synchronize procedure time is absent without uplink synchronization pro

25、cedure. The RRC procedure parameter is equal to N1+N2=170ms. Interruption Time AnalysisThe interruption time i.e. the time between the last TTI containing a transport block on the old DPCH and the time the UE starts transmission of the new uplink DPCCH, shall be less than the value in table 1. There

26、 is different requirement on the interruption time depending on if the cell is known or not.For handover between synchronous system and asynchronous systems. the interruption time has the same value：table 1 handover interruption time Number of cell Max delay msKnown cell Unkonw cell140 3502.3 Tim-de

27、lay Summarize of Handover Between Synchronous Cell Handover time-delay=measurement reporting time +RRC procedure parameter+interruption time. According to the above analysis, this time-delay T=1080ms+40ms+170ms=1290ms.In the real networks, the time-delay may be larger because of other factors influe

28、nce3 Handover Between Asynchronization TD-SCDMA Cells Time-delay AnalysisAsynchronous system handover is the inter-frequency TD-SCDMA cell handover, it is hard handover. The source cell and target cell can belong to one NODEB or different NODEB but same RNC. This article only discusses the situation

29、 of in the same NODEB. Because of the adoption of location technology, the inter-frequency baton handover is some different from hard handover. the UE can directly have access to the destination cell by uplink synchronization procedure without downlink synchronize procedure because the Physical Chan

30、nel Reconfiguration message gives UE the destination cells spreading code, MIDAMBLE. etc.3.1 Analysis of UE Measurement Reporting Time-delay And Interruption time According to the 2.1 section analysis ,the measurement reporting time is 1080ms.The interruption time is analyzed at section and the valu

31、e is 40ms 3.2 RRC Procedure ParameterRRC procedure parameter is defined as the time that system completes the Physical Channel Reconfiguration procedure. This time is made of N1 and N2 ,these values is defined at the 3GPP TR 25.331 .N1 = upper limit on the time required to execute modifications in U

32、E after the reception of a UTRAN -> UE message has been completed N2 = number of 10 ms radio frames from end of reception of UTRAN -> UE message on UE physical layer before the transmission of the UE -> UTRAN response message must be ready to start on a transport channel with no have access

33、 to delay other than the TTI alignment (e.g. DCH, therefore excluding delays caused by RACH procedure etc). N1 and N2 are independent, this chart is the RRC procedure parameter sketch mapChart 1 RRC procedure parameter sketch mapN1Interruption timeUplink synchronizationN2Physical channel reconfigura

34、tionPhysical channel reconfiguration completeUEs target state is CELL_DCH when the baton handover has been completed. but the N2 cannot be specified, because the Physical Channel Reconfiguration Complete / Failure message is transmitted only after physical layer synchronization, which depends also o

35、n Node B.When the UE transfers from CELL_FACH to CELL_FACH state with no timing deviation between adjacent synchronous cells, the N2 is 9,For the handover between synchronous system, although the UEs target state is cell_DCH, the N2 is also 9.But for the handover between asynchronous cells, the N2 o

36、f RRC procedure time-delay is 90ms+uplink synchronization procedure time .The uplink synchronize procedure is beginned from the UE transmits SYNC_UL and ended at the completion of UE transmits RACH. The typical uplink synchronization time is 7 subframe ,5ms each subframe. so the N2 for handover betw

37、een asynchronous cells is 90+35=125ms and for handover between synchronous cells is 90ms.So,the RRC procedure parameter is 125ms+N1=205ms.Table 2 Physical Channel Reconfiguration parameterProcedure :UTRAN -> UEUE -> UTRANN1N2NOTES:Physical channel reconfigurationTarget state: CELL_DCHPhysical

38、channel reconfigurationPhysical Channel Reconfiguration complete8NAN2 depends on the nodeb because of physical layer synchronization Physical channel reconfigurationFrom CELL_FACH to CELL_FACHPhysical channel reconfigurationPhysical Channel Reconfigurationcomplete893 3 Time-delay Summarize of Handover Between Asynchronous CellHandover between Asynchronous TD-SCDMA cells time-delay is：T=measurement reporting time +RRC procedure parameter+interruption time., the measurement reporting