Zax
Active Member
Hi cellular - the following is an extract from a previous thread looking at how fast you can go on GPRS. As you can see there are a lot of variables...
Quote:
Originally Posted by kwmf View Post
80kbit is what you can theoretically get on coding scheme 4 if you can grab the maximum allowable time slots.
Coding scheme is determined by signal quality and strength, if I recall CS4 was only about 25% of the cell - but I stand to be corrected. Most people will generally fall into the CS2 or CS3 range which is essentially dialup speeds. If your signal is really bad you will get CS1.
Check out http://en.wikipedia.org/wiki/Gprs if you really want to get into it.
end Quote:
With CS4 you can get a maximum of 171kbps with the maximum of 8 timeslots, however as far as I can gather we are limited to Class 12 operation which restricts the number of slots to 4 - this means you could get a maximum speed of 86kbps. I agree that it may be difficult to get CS4 since you need a good radio path. CS4 uses a minimum of overhead bits which limits error correction - thus the noisier your radio signal, the lower the coding scheme used to maximise the channel reliability. The actual data throughput per timeslot is as follows:
CS4 - 21.4kbps
CS3 - 15.6
CS2 - 13.4
CS1 - 9.05
Thus there are a lot of possible reasons for the slow speeds e.g.:
- Poor signal - maybe forced as far as CS1
- Congestion on your local tower - insufficient slots - maybe you only get 1 slot...
- Congestion somewhere else in the network.
You could get only one of the above or a combination...leaves you going nowhere fast!