cells without SDCCH

actully this in my opinion called FACCH call setup

Hello pix,

In my opinion, here during call set up, when a MS requests for a channel in RACH, instead of asking the MS to tune to SDCCH for further call set up procedures, the MS is directly alloted a TCH which in turn would do the neccessary signalling for call set up.

Sanjay,

Thanks for the answer. I understood you’re using this on your Ericsson network ? Does it create too much signalling load on the BCCH ? I’d be interested to see the messages/procedures schematics of such a call setup…

Iwan,

Excessive timing advance, and no neighbor ? Your problem shouldn’t be excessive TA, but rather : “Subscribers that are very far away manage to connect to this cell, and they have a very poor call quality. Such a situation degrades the QoS for this cell (high call drop, low cssr…).”

Well, you can simply set a TA threshold. For instance, TA_LIMIT = 20 … Subscribers after 10km ( = 20 TA / 0.55 km) will not see this cell anymore, therefore they can’t make calls on this cell.

BUT keep in mind that if you reduce the TA limit, you’ll reduce the amount of subscribers that can use this site. In other words, you’ll remove network coverage from a certain populated area. This can have a bad influence on your operator’s image.

Another solution : increase the RXLEV_ACCESS_MIN, from -106dBm to -100dBm and observe the impact. This will filter out all the subscribers that don’t have a RX_LEV strong enough. I prefer this solution, because you don’t limit the cell geographically.

Good luck,
Pix

Iwan,

with rxlev access min = -100dBm, you still have a poor QoS ?

I would check the path balance of this cell, perform drive-tests, check interference, and check the QoS per TRX. Overall : try to be certain that the hardware is good and the frequencies are clear.

If everything is fine, I would check power control parameters, possibly inhibit DL and UL power control for few hours and check the imapact. I would also implement synth. frequency hopping on a TRX, and force traffic to go on this SFH TRX (to benefit from frequency diversity).

Then I would continue reducing the RXlev access min until I see an improvement. Compare those results with your drive-tests. Where is, geographically, the problem ? Can’t you add an aditionnal site to cater for this area ?

For information, what are the values for:
the Call Drop Rate,
the TCH assignment failure rate, the path balance,
the average timing advance,
the average Rx Lev downlink,
and the traffic in erlang ?

for a long time i am facing from one site BS288 this from SDCCH drop rate is very bad.Thogh i checked all of our BTS & BSC related soft, feeder cable, Power, Antenna,yet i am facing SDCCH drop reate is bed.
WOULD you give me suggestion how can i solved the problem.?

hi i m new in NSN optimization

So plz suggest me the ways to improvr KPI’S for NSN system