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  1. #1
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    Edap

    Hi,

    Could some one share ideas on EDAP basics and how time slots are configured for TRX. How is EDAP expansion done to accommodate more capacity for GPRS/EDGE?



    Thanks

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    For EDAP speed the timeslot we r assigning is the actual speed like, we are using 3 timeframe so it's ABIS speed will be 192Kbps, so this is the ABIS speed not the Um speed, Um speed is maximum of 230Kbps but the EDAP is only 192Kbps n is divided into the all users using GPRS connection at a time, so in average i get 10-20Kbps in practical at my Nokia 3110c Modem so u can also calculate this. one thing to remember that not go to the Modem speed which shows u the 460Kbps or 115 Kbps whatever.



    One thing to be noted that EDAP in ABIS allocation consumes 1 time frame of minimum n hence u can calculate the speed out of it.

    we all know 1 timeframe's speed is 64Kbps (that is 4 time slots)

    n hence wht we use, if it is 2 time frame then EDAP's speed will be 64*2=128Kbps
    and similarily this goes on.




    perfect ans for Speed of EDAP
    If someone ask in interview the same question, the proper answer is.

    It is the multiple of 64Kbps.


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  5. #3
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    Hi dear,

    EDAP means Dynamic abis pool for EGPRS requests.
    The Abis interface is situated between the BSC and the Base Station sites.The Abis interface is also used for GPRS services. In a “traditional” GSM/GPRS system, each TRX channel is mapped statically to Abis PCM timeslots.


    In the air interface, higher rates are achieved through the use 8-PSK. Achievable transmission rates are in the order of 59.2 Kbit/s per Radio Timeslot (RTSL)
    Higher data rates don’t fit in 16 kbit/s A-bis channels so 32, 48, 64 or 80 kbit/s Abis links are needed and Fixed Abis allocation of such links would be expensive and would lack flexibility.
    The Dynamic Abis Pool is a shared extra Abis resource for EGPRS channels and TRX’s. The Dynamic Abis functionality allocates Abis transmission capacity to cells when needed instead of reserving full fixed transmission link per TRX.

    Now lets see why EDAP is required.

    PCU frame types

    PCU data frame:-

    Used when TRX not in EDGE mode
    Only able to carry CS1 and CS2

    PCU master data frame:-

    Used when TRX is in EDGE mode
    Carries CS1 or MCS1 on its own and CS2-4 and MCS2-9 with the help of slave frame(s)
    Includes pointers to the slave frames

    PCU slave data frame:-

    Carries additional data that does not fit in PCU master data frames

    Click image for larger version. 

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    Fixed channels and EDAP

    For each GPRS radio timeslot on each EDGE TRX, one fixed 16-kbps channel is allocated on the Abis for the transfer of PCU master data frames
    PCU slave data frames are allocated in a common pool, the EDAP (EDGE Dynamic Abis Pool)
    We are still going to make a static allocation of 16 kbit/s per TCH, (used for voice or data)
    In a PSD call, this sub-TSL is called a master Abis channel, and if required, the system can allocate up to 4 extra slave Abis sub-TSLs for same master from dynamic pool.

    There are some counters defined in OSS through which you can see how many requests are getting blocked in particular EDAP.So accordingly you can increase the EDAP size.


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    One thing to be noted that EDAP in ABIS allocation consumes 1 time frame of minimum n hence u can calculate the speed out of it.

    we all know 1 timeframe's speed is 64Kbps (that is 4 time slots)

    n hence wht we use, if it is 2 time frame then EDAP's speed will be 64*2=128Kbps
    and similarily this goes on.


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