Cellular GSM Technology

Author

GSM Q.? plz

djwk01

2008-02-11, 10:33 pm

What is the number of simultaneous calls in each cell in a GSM
assuming no analog control channels

Andreas Wenzel

2008-02-12, 12:33 pm

djwk01 schrieb:
> What is the number of simultaneous calls in each cell in a GSM
> assuming no analog control channels

Each GSM carrier has eight timeslots. On the first frequency of a cell,
only 7 of those can be used for calls. If the cell has additional
frequencies, all 8 timeslots can be used on them.

So if a cell has 3 carriers, it will have 23 timeslots available for
calls. With standard codecs, you need one timeslot per call, giving you
23 calls. During peak load, the carriers can use half-rate codecs to
squeeze in twice as man calls, at the cost of lower voice quality.

Andreas

matt weber

2008-02-12, 3:34 pm

On Mon, 11 Feb 2008 19:42:58 -0800 (PST), djwk01 <djwk01@gmail.com>
wrote:

>What is the number of simultaneous calls in each cell in a GSM
>assuming no analog control channels

Depends upon how many channels are allocated to the cell.
Each channel (200Khz) can have 8 full rate calls in it (There are 8
time slots in the channel), or 16 half rate calls.(I don't know any
carrier who offers half rate).
The 900 Mhz GSM band has 25 Mhz available in each direction (35 Mhz
for E-GSM),
and that is shared among the operating carriers, and further
subdivided because you cannot use the same channel in adjacent cells.
The 1800 and 1900Mhz bands have more space available, and some cells
from some providers user channels in both the 900 and 1800 Mhz band.

IIRC GSM850 is also 25 Mhz each way.

Generally the carrier will put more channels in heavy used cells, and
fewer in less utilized cells.

The number of calls is further reduced by the use of Data
transmission, where more than one of the 8 time slots can belong to a
single phone or PC card.

So there is no clear answer to your question.

Anonymous

2008-02-13, 4:33 am

"matt weber" <mattheww50@verizon.net> wrote in message
news:4g14r3919qd9q7f
crakhsiphhmedh87o57@
4ax.com...
> On Mon, 11 Feb 2008 19:42:58 -0800 (PST), djwk01 <djwk01@gmail.com>
> wrote:
>
>
> Depends upon how many channels are allocated to the cell.
> Each channel (200Khz) can have 8 full rate calls in it (There are 8
> time slots in the channel), or 16 half rate calls.(I don't know any
> carrier who offers half rate).
> The 900 Mhz GSM band has 25 Mhz available in each direction (35 Mhz
> for E-GSM),
> and that is shared among the operating carriers, and further
> subdivided because you cannot use the same channel in adjacent cells.
> The 1800 and 1900Mhz bands have more space available, and some cells
> from some providers user channels in both the 900 and 1800 Mhz band.
>
> IIRC GSM850 is also 25 Mhz each way.
>
> Generally the carrier will put more channels in heavy used cells, and
> fewer in less utilized cells.
>
> The number of calls is further reduced by the use of Data
> transmission, where more than one of the 8 time slots can belong to a
> single phone or PC card.
>
> So there is no clear answer to your question.

Half rate AMR is widely used in the US and elsewhere (also basic HR) at
special network congestion cases.

The maximum number of carriers on a cell is almost unlimited, in practise it
is limted by the frequency allocation the operator would have.

A site usually has multiple cells (sectors or different frequency bands,
although those can be a common cell too).

At one time the mobile may use maximum 64 frequencies on a hopping
configuration.

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