One of the major limitations of second generation cellular communications
systems is that data can only be transferred after a
connection has been established. This is inefficient if only small
amount of data is transferred, and in situations where data
is transferred in bursts. 2.5G cellular systems allow a
mobile station to be "always-online" for sending and receiving packet
data. This allows efficient transfer of small amounts of data,
without the overhead of establishing a connection for each transfer.
It also efficiently supports bursty data transfers, avoiding the need
to allocate capacity to a connection that cannot be reallocated
by the network if the connection chooses not to use
it. The two major forms of 2.5G enhancements to
second-generation cellular systems are the General Packet Radio Service (GPRS)
and Enhanced Data Rates for Global Evolution (EDGE).
Some GSM networks
support the General Packet Radio Service (GPRS) and Enhanced Data
Rates for Global Evolution (EDGE).
Other topics in our resources on GSM related to 2.5G include: