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How to plan for FPDCH and Soft and Hard

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  • #69354

    Hi Team

    Can someone pls tell me that how FPDCH and OPDCH channels are planned for carrying data traffic.
    Pls help in making this understand wrt to voice analogy like we plan Trx wrt the voice traffic carried which is measured by the voice equipped capacity and the traffic carried. which in turn helps us understand the SD and Tch Blocking.


    hi deepak,

    heavy topics, I feel it’s too much to explain…



    Hi Pix

    Well I thought so but I just need a bit of help actually if you could generalize in terms of voice planning. Till now i have done only voice planning and I couldn’t correlate data planning in terms of that how to plan FPDCH and OPDCH initially for a site and its cells. For ex: in voice if I plan a site with expected base of 100 Subs and tentative calls in BH are approx. 800 then with 30 milli erl I need a capacity of (30*800)/1000 erl i.e 24 erl so a sector config of 6.5 erl and site config of 6.5*3=22.5 erl would easily do that. I just want someone to help me correlate intial data planning of channels like that or may be its more tedious than that. I have studied basics of data and i’m familiar with TBF and EDGE/EGPRS basics if not more.


    Hi Again

    Actually I have some cells with Tch blocking and the interesting thing is that if I augment capacity in them they go below threshold of the post voice utilization which should be higher than 50% after capacity addition. Now we would augment in most of the cases from 2 to 4 Trx where only additional Trx card is inserted and 4 Trx transmit on same antenna with combiner loss of 3db which will further increases the chances of 1 and 1.5 erl traffic dip post Trx addition. So what I want is that if I could dig deep a little on data channels then I could ask for FPDCH reductions in case data volume is not that high in those cells or inversely could ask for increasing FPDCH after Trx addn if data volume is high. So for this analysis I need a bit of info and Knowledge on data planning basics and parameters like Hard and Soft Blocking.
    Hoping for some kind of feedback on this.


    hi deepak,

    there is a big difference between planning a data network from scracth, or upgrading an exisitng network (your case).

    So in your case, you want to know how to increase voice capacity, by decreasing capacity for PS.

    FPDCH or SPDCH are static timeslots that cannot be preempted by voice. Usually, you can choose a value between 2 to 4. Selecting SPDCH rather than FPDCH should decrease your GPH load.
    Next step is to maximize usage of each PS timeslot (pdch) :
    pile up several TBF on the same PDCH
    authorize EGPRS on all ts
    authorize maximum throughput (mcs9)
    reduce the inactivity timers, so that idle TBF are released and make room for new TBF

    Then OPDCH .. it is an interesting parameter, but should not affect your voice capacity. All PDCH in the OPDCH zone can & will be preempted by voice whenever it is needed.
    You can put a high value, but avoiding to stress your GPH board too much.

    In your study you can also measure how many TCH are used AT MOST in your cells, and calculate how many PDCH are left. Would that be enough to provide a good-enough experience to the user ?
    If number of remaingin ts is too low at the busy hour, you can then “force” Half rate to be triggered early (CSPRIO or something like this). It’s probably the most efficient parameter to restrain the voice to take too much space in the cell.


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