congestion analysis2

7/30/2019 Congestion Analysis2

1/14

HSDPA License and Uplink CE Congestion Analysis

Prepared By:

Jefferson Aboo ,

NPO ,Alums ,Mumbai

Date : 09/09/2012


2/14

Issue :

As the traffic increasing in the network, a lot of cells RRC and RAB Access Success Rate are getting

degraded.

Problem analysis

During the Analysis it was found from M2000 that RNC is getting HSDPA License exceed alarm

(Currently configured License for HSDPA is 210 Mbps but our license is based on

Voice(18000Erlng) + data usage(210 R99 +210 HS) which if we calculate in terms of Mbps will be

more than 2000Mbps ,so our first conclusion is that HSDPA License should not create any issue .

Analysis of Stats statistics for one of the RNC in the Punjab

1) From the below stats it is clear that maximum Access failure is in 22:00 Hrs which is the

RNC Data Busy Hour .

2) If we further drill down the PS access failure it is clear that Access Success Rate in RRC is

ok , we are having issue in RAB Assignment3) If we further drill down PS RAB Failure , it is clear that most affect RAB is R99 .

4) If it was HSDPA License issue it could have affected HSDPA RAB Most

We furthur drilled down to find out what is the reason for RAB Failure using sub counter.

Attached below is the RAB failure analysis for same RNC .


3/14


4/14

From the above stats it is clear th

1) Also from the counter def

pegged in VS.RAB.FailEs

Counter Definition ; When toperation fails because of insuffici

call is rejected then count will be(the failures are pegged due to con

Top 10 Cells with Maximum Failu

at most of the calls are rejected due to UL CE C

inition if any call are rejected due to license the

abPS.Unsp

he RNC sends the CN a RAB ASSIGNMENT RESPONSE mess

nt abilities (such as Resource Admission Failure, License Reject

VS.RAB.FailEstabPS.Unsp - VS.RAB.FailEstabPS.Cong),from tgestion and mainly uplink CE Congestion

res

ngestion.

it should be

ge indicating that the

and so on.) ie if any

he a stats it is zero , all


5/14

Now we have to find what is the reason for high uplink CE Congestion

2) Detailed analysis was done node B wise to find the actual reason for uplink CE Congestion

3) Top 10 Cells with maximum number of Access failure was filtered and from that 4 Node B

for which CEs are Highly utilized without enough traffic (RNC Data Busy Hour ) .


6/14

Malikpur_Rajpura - Node B Failu

Cell is having high uplink

Along with traffic for few

congestion starts

When the traffic starts increasing

Below chart shows which RABs(

re Analysis

CE Congestion Below shows the mapping of

ays .It is clear that when uplink R99 traffic incr

number of failure also started increasing.

verage number of Users in each RAB ) are mos

E Rejection

ases

ly Used .


7/14

Total CE required for each RAB

Chart shows the total CE require

64Kbps and we dont have RAB u

Now we have to find CE utilizatio

CE Utilisation from the stats .

From the current formula MAX C

for R99 Service ,Most of the RB used for UL in

sage details for HSUPA ,inorder to find the CE u

n in UL for all service

utilisation was showing only 58%

the nodeB is

sage for HSUPA


8/14

After rechecking the formula it was found the utilisation was calculated using below formula

Total CE used / Total License ,

Total License was 192 but the hardware configured was only of 64 CE ,so actual maximum

utilization was above 90% and mean 71%.

In Busy hour CE utilization should not cross more than 60% ( IF the CE is crossing more than 60

then at any point in that hour CE Congestion can occur and new call will be rejected .

Also from the above Utilisation chart HSUPA utilisation is only 11% , 11% of 64CE Configured is

roughly around 8 CE .ie for R99 37 CE and HSUPA 8 CE .

So the conclusion is that R99 is using More CEs .

2 ) Node B BSNL_PUNJAB_PHASE_3B2_MOHALI failure Analysis

RB Mapping


9/14

CE Usage .

From the above analysis also it is clear R99 is using more CE and majority of the RB is 64Kbps .

Now we need to analysis why most of the CE are

3 ) Node B SEC_41_D RB


10/14

Solution :

Now most of the NodeB in the network was configure as UL 192 CEs and DL 192 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/HSUPA use dedicate channel. So ULneed more CE than DL and congestion happens in UL.

According the situation, the solution is as follows

1, CE expansion (Not immediate solution as no CE/WBBP boards are available)

2, Reduce the UL data rate for some user to release some CEs for new user access to the network

(Can be implemented)

Solution 1;.

UFRC :ULBETRAFFINITBITRATE

UL initial access rate of PS background or interactive service. When DCCC function is enabled, the uplinkinitial access rate will be set to this value if the uplink maximum rate is higher than the initial access rate.A higher value indicates that it takes shorter time for BE services to reach the maximum rate. Note thatthe rate will be decreased through negotiation when congestion occurs. A smaller value indicates that BEservices is easier to be accessed. It is not recommended to set a too small value, because it will takelonger time for BE services to adjust to a higher rate when needed.

Default D64

Current Setting: D64

Recommendation: D32

HSUPAINITIALRATE:

HSUPA BE traffic initial bit rate. When DCCC algorithm switch and HSUPA DCCC algorithm switch areenabled, the uplink initial bit rate will be set to this value if the uplink max bit rate is higher than the initialbit rate.

Default : D64

Current Setting: D64

Recommendation: D32

Most of user is PS 64K, especial in busy hour, the average PS64 is round 8(ibs) in UL (means 25CE), nearly do not havePS32, PS384 and PS128user

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


11/14

Solution 2

Check if LDR is working or not .

a. SET CORRMALGOSWITCH: ChSwitch=DCCC_SWITCH-1; (On in punjab)

b. DRASWITCH_DRA_HSUPA_DCCC_SWITCH I on or not (On in punjab)

SET LDCALGOPARA: LdcSwitch=NODEB_CREDIT_LDR_SWITCH-

1&LCG_CREDIT_LDR_SWITCH-1&LC_CREDIT_LDR_SWITCH-1;(Currently false- 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)

c. MOD NODEBALGOPARA: NodeBName="xxxxxx",NodeBLdcAlgoSwitch=NODEB_CREDIT_LDR-1&LCG_CREDIT_LDR-1;(Currently false,) -

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

d. MOD CELLALGOSWITCH: CellId=xxxxx, NBMLdcAlgoSwitch=CELL_CREDIT_LDR-

1;(Cureently False) - Set cell LDR trigged by the by high CE usage of Cell level.

e. MOD CELLLDR: CellId=xxxxx, UlLdrFirstAction=BERateRed, UlLdrSecondAction=interrat

handover , GoldUserLoadControlSwitch=ON - Set cell LDR action, it means when LDR trigged,

some user with BE service will be reduce data rate. If most of user are gold users , data rate ofgold user also can be reduced to implimeneted after checking the user category

5 ) Node B Near_RIMT

Stats show the RAB rejection is mainly due to DL Power congestion .Site Downlink Power configuration need to be checked .

From the RNC Dump itr show that power configured for is site is very high

Soultion 3dB Reduction in the CPich recommended for removing DL Power congestion


12/14

5 ) Node B Prababa Colony

Site utilization is high ,

Failure mainly due to ul Power congestion and UU Failure ,ie ther is some issue in uplink

1,check is site is overshooting

2,check if hardware is ok

3, check if cable is ok in uplink ( Path impbalance and RTWP Analysis to be done using naster )

4,balance traffic with neighbouring cell

5.Power configured is also veru high ,


13/14

6 ) Node B SEC22

Ul CE and Ppwer Congestion

Solution:

Check ENU

Reduce Traffic

Check RTWP

Check if site is overshooting

7 ) Node B Ranjit Nagar

High Traffic in the site after checking the RTWP change ENU from 95 to 150

Most of the users are 64Kbps ,

Recommended to change initial bit rate or reduce uplink traffic


14/14

congestion analysis2

Documents