2.5G(GPRS)

In 2.5G there are 3 main subsystems. They are NSS (Network Switching Subsystem), BSS (Base Station Subsystem), GSS (Group Switch Selector). Actually BSS consist of BTS, BSC and TC with their relevant interfaces. MSC and A (interface) will form NSS. And for 2.5G GGSN (Gateway GPRS Support Node), SGSN (Serving GPRS Support Node), PCU (Packet Control Unit) will form GSS. GSS is linked to BSS and NSS as follows (Through BSC).

Transceiver (TRX)

PDCH can be static or dynamic. When we configure a BTS we can define Min_PDCH, Max_PDCH depending on the customer base. Voice will get the highest priority. If the voice traffic keep increasing we can reduce the number of P channels until it reaches Min_PDCH. Then more subscribers will be able to make calls and data speeds will be reduced at that moment.

On the other hand if the demand for data is getting higher and higher P slots will get up to a maximum of defined Max_PDCH.