HSDPA accessibility rate degraded.Hi experts,What's the possible
reasons of HSDPA accessibility rate degraded (NSN Technologie).
The PS384 is used 20% in the infected NodeB,then i suspect that
the basic problem is the CE congestion in the uplink .In fact,the
PS384 uplink bearer uses about 12 to 16 CE according to the system
module used.
I'll change the parameter HSDPAMaxBitrateUL from 6 (384kbps) to
4 (128kbps).
This parameter defines the maximum user bit rate allowed in a
cell for HSDPA UL DCH return channel. It is applicable to the PS
domain NRT RAB.
For the HSDPA Accessibility please first check the RSRAN 073
Report for the infected NodeB and see where you are having the
maximum failures which is contributing max to HSDPA Accessibiility
degradation. Then Below are the reasons you have to look into.
1) For Setup Fail BTS--Check CEs at BH 2) For setup fail UL
Return Channel--check UL power congestion and reduce the UL bit
rate accordingly. 3) For Setup Fail Iub Transport-- check Iub
Resource Congestion 4) For Setup Fail UE-- Check RAB
Reconfiguration failure Rate 5) For Setup Fail RNC-- Check RNC Unit
Load and Alarms on units 6) For Setup Fail too many Users-- Check
simultaneous HSDPA Users
So first thing to do is to find actually which out of these 6
reasons is contributing for your accessibility degradation so that
you can work on that.
Hope will be helpful.
the HSDPA =downlink and PS384 should be R99! the HSUPA=uplink
and should be not use 384k, so what you saying is DCH/HS, so if you
have high RTWP (UL RSSI) than try to lower the DCH rate to 128 or
64
Actually if the RAB used is DL=HS/UL=DCH you will need
HSDPAMaxBitrateUL =384 otherwise don't expect to have high bit
rates on HSDPA DL (like 14 Mbpsec or more when you have MIMO or
DC-HSDPA)). That is because whatever application is used by your
mobile(TCP/IP usually) on your test laptop it will need an
acknowledgement sent in uplink( to UTRAN network). That
acknowledgement is using a DCH channel( R99) that needs to have a
specific bandwidth. You can try a new value of HSDPAMaxBitrateUL
=384 Kbpsec but have a look at your HSDPA throughput and see if it
is not limited by this change.
After implementing the HSDPAMaxBitrateUl=128Kbpsec,I found that
HSDPA throughput has deteriorated even more.Then I'll return to the
first configuration and try an alternative.
Usually synchronization affects RRC accessibility and you need
to maintain a certain number of consecutive sync burst to
establish/keep your connection. You need to check your sync timers,
sometimes if it is set to high value you lose your connection more
frequently otherwise you should have a look on the sync
server/solution. It is also a good idea to check Sync alarms on
node-B/RNC level. In case you have server issue, then you are
supposed to see more alarms at node-b/RNC level. Moreover, you are
supposed to see RAB drop due to abnormal release/sync issue.
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As Dan mention RRC failure will not effect HS accessibility or
HS/EUL Throughput, it will shows poor PS or CS accessibility, and
again if the failure due to synch it most be problem in Air
interface DL or UL. it could be UE accessing the cell from too far,
cell has high UL RSSI, or there is pilot population in DL. IF you
sure that cells footprint is controlled and UL RSSI is good you
need to modify some timers as Dan suggest, I cant recommend values
as I m not NSN expert
While CE congestion is one of the common causes of accessibility
problems in most countries and vendors we should not conclude until
we see the actual CE utilization...i suggest pulling CE util stats
first on a per hour basis to really verify if CE util is reaching
capacity/license limit....also there are counters indicating if
accessibility issues are due to HW limitation...
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