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Reply To: EDGE Low DL Throughput


KB, no problem 🙂
if you can’t work on your Abis capacity.. mmm…

BTS config = 4/4/4 ?
that’s (i assume) 3 BCCH + 6 SDCCH
so you have 9 bonus nibbles + 8 extra nibbles… that’s a total of 14 extra nibbles.

Imagine: one MS, with 4 PDCH at MCS-9. It will use 4 x 4.5 nibbles = 18 nibbles.

it will use its 4 basic nibbles + 12 extra nibbles.

All extra nibbles are used up by only one MS !!!
Since they are a lot of GPRS signallings (Attach, PDP context, RA update), many MS’s will require capacity… And therefore there won’t be enough even for the one MS that needs 4PDCH at MCS 9.

Conclusion: you must add extra TS. If you can’t, then the ONLY solution is to reduce TCH capacity. You can do it this way:

MAX PDCH HIGH LOAD = 5 … 7 … 8
GPRS HIGH LOAD = 85% … 90%

Start with values at the left, then try the values at the right. Check if you have improvements, step by step. Check your TCH congestion.

If your BTS is 4/4/4, you should have more than 2 extra abis nibbles left… I cant remember exactly, but it should be 5 or 6, no ?

Finally, check your GPRS indicators. You can see how much Abis nibbles are busy or free, how many PDCH are allocated in the cell, at busy hour, etc. They will really help you to understand what is limiting your TBF throughput.