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HSDPA License and Uplink CE Congestion Analysis
Prepared By:
Jefferson Aboo ,
NPO ,Alums ,Mumbai
Date : 09/09/2012
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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 .
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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
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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 ) .
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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 .
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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
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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
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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
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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
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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
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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 ,
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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
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