U900 Optimization Issue

[itking]

Hi Friends,

We [Huawei] are working on U900 project with an operator. We have 4.2 MHz Band, very tight planning but there are few problems we are facing at the moment.

We have below issues [priority by issue]

1. RTWP: Around 40% of all sites have this issue..... RTWP SLA is -100 & better but currently sites with bad RTWP ranges -95 to -99.
(a) Field test done no considerable interference.
(b) Parameter audit done, everything looks normal.
(c) Jumpers and connectors checked randomly and found OK [and U900 is carrier expansion so no major hardware changing just adding board]

2. iRAT: neighbor audit done, there is slight improvement with some parameter changes but still not as per SLA [98% & drops less than 5]
3. PS & CS drop: Mainly due to vs.RAB.AbnormRel.PS.RF.uuNoReply vs.RAB.AbnormRel.CS.RF.uuNoReply. What parameter or value I should change to improve it.


Appreciate your input on this issue as we are facing customer pressure now, It will be great if some one can provide me some list or case study of changing parameters for above issues. waiting for your Expert Opinion................

[Shakeel_15]

Hello,

For U900 are you using seprate antennas or existing 2G Antennas?

BR

[giegala]

Huawei allows to do UL frequency scan which is similar for frequency analyser. Did you run it? U could see where interference is located - maybe it is coming from GSM

[itking]

Hello,

For U900 are you using seprate antennas or existing 2G Antennas?

BR

Same 2G antennas

[itking]

Huawei allows to do UL frequency scan which is similar for frequency analyser. Did you run it? U could see where interference is located - maybe it is coming from GSM

We've used Frequency Scanner & Spectrum analyzer inf the field and there was no interference reported [chose random sites]

[giegala]

Well, it is likely that your cables are clean, so nothing had shown up by external Freq scanner and Spectrum Analyzer. If there is no TMA or it has been configured properly (a common mistake by HW wireless team), then most likely cause of RTWP is interference between GSM and WCDMA.

The cause could be near-far effect between GSM and WCDMA users. NodeB has narrow 4.2 MHz transmission in DL, but UEs are made for 5MHz. So, there is out of band leakage. When there is single WCDMA cell, NB controls and coordinates UL power for all UEs. But there is no coordination between GSM and UMTS. So when 1 UE is transmitting high UL power, it would leak to GSM. Now GSM will have bad UL rxqual and force MS to use higher power, which in turn will ask for more UL power in WCDMA.

In order to verify this hypothesis, you can switch off GSM trx (on cell and site level) and check for RTWP. Also it might worth to look at real-time RTWP monitor - maybe you could see that the RTWP goes high for some time, but then later it drops, because of no activity on GSM.

[RF engineer]

You need to check if CDMA800 network you have as due to inter-modulation external interference generated.do you have subscriber on U900? and HSUPA is working?

There is a solution we tried and worked but need license and RRU should be 3929 which called NBIS feature. will reduce RTWP to almost -105 dBm .

Let me know what your result .

[rumy]

I can see RF engineer already pointed to which would be the issue in your network: intermodulation products. Can you give us an idea, briefly, in terms of aerial : RRU (?)->jumper->(combiner?)->jumper->(TMA?)->ANTENA(?)
It might be that you need to revise the design/ planning in the network!

[srilasitha]

You need to check if CDMA800 network you have as due to inter-modulation external interference generated.do you have subscriber on U900? and HSUPA is working?

There is a solution we tried and worked but need license and RRU should be 3929 which called NBIS feature. will reduce RTWP to almost -105 dBm .

Let me know what your result .

Can you provide details of the feature

[brianm]

If you did your 2G refarming correctly then try and do RF footprint optimisation on the 2G sites to minimise over-shooting as I suspect there is a leakage from U900 to GSM as someone explained above