Hello Gem,
The main reasons for low throughput are:
1- poor RxQual (= poor C/I)
2- low RxLev
3- congestion in the cell (congestion CS + PS)
4- congestion in the Abis
5- bad parameters (max pdch high load, max pdch, max number of tbf multiplexed in one pdch, etc)
6 – Congestion in the Ater PS or in the Gb or in the Gn or in the Gi interfaces.
Since you are talking about a network wide problem, you should focus on the case 3, 4 and 5 and 6. I doubt you have interference and poor coverage in your whole network.
If you’re talking about just one cell in particular, investigate all possible cases.
First step;
how many trx in the cell?
how many erlang at busy hour?
how many pdch are allocated in average in the cell ?
how much abis is used and free?
what is the congestion on the ater ps?
what is the congestion on the other interfaces ?
For one cell, perform a drive test a low load hour, and then same place at busy hour. Do you see any difference ?
(which vendor are you using ?)
cheers,
pix