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The Analysis of the Channel Elemet CongestionProblem description

As the traffic increasing in the network, a lot of cells has up link channel element (CE) congestion, it first affects PS setup success rate, and the IA(1-Call Setup Success Rate).Problem analysisNow most of the NodeB in the network was configure as UL 124 CEs and DL 124 CEs. In Huaweis algorithm, only dedicated channel consume CE. Most of users bear in HSDPA, HSDPA in DL and R99 in UL, and HSDPA use common channel while R99 use dedicate channel. So UL need more CE than DL and congestion happens in UL.According the situation, the solution is as follows

1, CE expansion.

2, Reduce the UL data rate for some user to release some CEs for new user access to the network.Operation and Result Analysis

Operation 1, LDR (2010-4-27)LDR is a algorithm to reduce congestion when the cell or node in basic congestion state, first choose site U_3111_CERRO_QUEMADO in PTO.

CommandSET CORRMALGOSWITCH: ChSwitch=DCCC_SWITCH-1;Open the DCCC switch.SET LDCALGOPARA: LdcSwitch=NODEB_CREDIT_LDR_SWITCH-1&LCG_CREDIT_LDR_SWITCH-1&LC_CREDIT_LDR_SWITCH-1;Set LDR trigged in RNC level, this command means LDR can be trigged by CE high usage of Cell level, cell group level and Node level.

MOD NODEBALGOPARA: NodeBName="xxxxxx", NodeBLdcAlgoSwitch=NODEB_CREDIT_LDR-1&LCG_CREDIT_LDR-1; Set Node LDR trigged in NodeB level, this command means nodeb LDR can be trigged by CE high usage of cell group level and Node level.MOD CELLALGOSWITCH: CellId=xxxxx, NBMLdcAlgoSwitch=CELL_CREDIT_LDR-1;Set cell LDR trigged by the by high CE usage of Cell level.MOD CELLLDR: CellId=xxxxx, UlLdrFirstAction=BERateRed, UlLdrSecondAction=NoAct, GoldUserLoadControlSwitch=ON;Set cell LDR action, it means when LDR trigged, some user with BE service will be reduce data rate. Also make the data rate of gold user also can be reduced, because all the users in network are gold user.Result AnalysisAfter active LDR on 2010-04-27 morning, LDR start to work, but it did not help much, the congestion is also high(Figure1)

After check the Users in network, most of user is PS 64K, especial in busy hour, the average PS64 is round 35 in UL (means 105 CE), nearly did not have PS384 and PS128user(Figure2).

There is minimal data rate for LDR, the minimal data rate used is just PS64, it means if there is no user with higher data rate than 64kbps, LDR cannot reduce its data rate.

Figure1 LDR Work_Cell31111

Figure2 User with Differnt BE Service_Cell31111Operation 2, Change DCCC Threshold and GBR(2010-5-4)SET FRC: UlBeTraffInitBitrate=D32;Change the Initial BE UL data rate from PS64 to PS32.

SET DCCC: UlDcccRateThd=D32, LittleRateThd=D32, UlRateDnAdjLevel=3_Rates, UlMidRateCalc=HAND_APPOINT, UlMidRateThd=D64;Change the DCCC data rate degree, from (MBR-PS128-PS64) to (MBR-PS64-PS32),make user with low data transition use PS32 and if need more data transition, increase the Data rate to PS64 and MBR(now use PS384). SET USERGBR: TrafficClass=INTERACTIVE/ BACKGROUND, THPClass=High/ Medium/ Low, BearType=R99, UserPriority=GOLD/ SILVER/ COPPER, UlGBR=D32;Change the GBR, from PS64 to PS32. GBR is guarantee data rate, also the minimal data rate the LDR can reduce. Result AnalysisAlso take cell 31111 as example, after parameter change,The Congestion is significantly lower than before(Figure3) , especially very low congestion in CS, the PS Call setup success rate and CS IA is better than before, but in the busy hour, it is not very good in 2010-5-5(Figure4). The most users in UL become PS32, PS64 decreased and PS128 was disappeared.PS384 is a little bit higher than before but also under 2(Figure5). Also, the CS user nearly no change (Figure6).

The PS Call setup success rate of the whole RNC of PTO also improve very much (Figure7) ,the traffic include Erlangs, HSDPA throughput,R99 UL throughput did now show significant change compared with before(Figure8), but it need be monitored for a long time. So, from the result, the congestion was decreased, the PS CSSR and CS IA is get better. But also have congestion in busy hour.

Figure3 Congestion Change_Cell31111

Figure4 PS CSSR and CS IA

Figure5 User with Differnt BE Service_Cell31111

Figure6 User of Voice Call_Cell31111

Figure7 PS CSSR_PTO

Figure7 Traffic_PTOOperation 3, 2010-5-1112On 5.11, change DCCC threshold for RNC PLM, LCH, and MCY. On 5-12active the LDR for all the cells of PTO, LCH, PLM and site 3637 in MCY. Also changed the DCCC threshold for BTO.Result Analysis

The congestion has significantly decreased both PS and CS.

PS CSSR and CS IA also improved

PS CSSR: most of time, CSSR washigher than 95%

CS IA : most of time, CS IA decrease to lower than 2%.

The HSDPA users has slightly increased.

The Traffic did not show big difference in these days.

CS Traffic

HSDPA data volume

R99 UL data volume

Advice

1,CE congestion is normal problem in network, the best way to resolve it is expansion the license and add new site nearby. But in really situation, the operator cannot do these in a short time, so we need do parameter optimization to decrease the congestion.

2,Huawei have some feature to resolve the problem ,but it should according to the really network, in the case, LDR did not help at first but when change DCCC threshold, LDR and DCCC both work well.7/2/2010HUAWEI confidential