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The capacity of each timeslot depends on the network and four coding schemes are defined, CS-
1 to CS-4. These are different to the capacities in HSCSD due to the differences between circuit-
switched and packet data operation. GPRS networks are typically launched using CS-1 and CS-2
only, limiting maximum speeds to those shown in bold below. The P800 supports CS-3 and CS-4
and will operate at the higher speeds where introduced by mobile operators.
CS-1
Rx
Tx
The diagram below shows how the P800 in GPRS mode will send data in packets, combining
timeslots when extra bandwidth is required, up to a maximum of 4 for received data and 1 for
transmitted data
Applications such as Messaging and the integrated browser will automatically initiate CSD,
HSCSD and GPRS connections, warning you if your desired action requires another connection
to be cut. Whilst a CSD/HSCSD connection is terminated after the transaction or a period of
inactivity, the GPRS connection will be maintained. This means that, for example, Web and WAP
pages may be browsed without any connect delay, and that the E-Mail client can automatically
poll for new messages.
When using the P800 as a modem to a PC, the GPRS connection is initiated from the PC as
usual by selecting a Windows
implicitly via the usual way that Windows enables applications to request connections. Where a
GPRS connection is defined in the DUN entry, the P800 will initiate a GPRS attach and connect
to the GPRS network.
9.05kbps
CS-2 13.4kbps
36.2
53.6
9.05
13.4
DUN connection, either explicitly within the DUN folder or
White Paper, January 2003
CS-3 15.6kbps
CS-4 21.4kbps
62.4
15.6
P800/P802
85.6
21.4
101
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