What is GPRS, and how does it extend GSM for data services?

GPRS (General Packet Radio Service) is an extension of GSM that adds packet-switched data transmission using TCP/IP, enabling mobile internet access — it's classified as generation 2.5.

Key characteristics:

• Packet-switched — unlike GSM's circuit-switched voice, GPRS sends data in packets (like the internet)
• Uses TCP/IP over the GPRS backbone instead of circuit switching
• Classified as mobile generation 2+ or 2.5

Channel usage (a clever optimization):

• Shared channels — multiple users share the same radio channel (unlike dedicated voice channels)
• On-demand allocation — in the startup phase, the phone uses free GSM channels (on-demand)
• Data prioritization — explicit reservation of channels for GPRS is possible (Dedicated Channel)
• Higher data rates by using multiple channels in parallel (PDCH = Packet Data Channel)
• Different coding schemes per channel → different data rates

What changed in the network:

• Required new hardware: two new network nodes were added (SGSN and GGSN)
• The rest of the GSM architecture (BTS, BSC, MSC, HLR) remained largely unchanged
• Flexible use of air interface resources — spectrum is shared between voice and data dynamically

Go deeper:

• GPRS (Wikipedia) — packet-switched "always-on" data over 2G, coding schemes and why it's called 2.5G.