While EDGE describes the physical upgrade to the radio interface (how the air carries the data), EGPRS is the specific packet-switched service that runs on top of it. If GPRS was the dial-up of the mobile world, EGPRS was its first version of high-speed broadband.
Key Technical Concepts
- Packet-Switched Data: Unlike traditional voice calls (circuit-switched), which keep a line open, EGPRS breaks data into small packets. This allows multiple users to share the same radio channel, using bandwidth only when data is being sent.
- Incremental Redundancy (IR): A sophisticated error-correction method used in EGPRS. If a data packet is corrupted during transmission, the system doesn’t just resend the same thing; it sends additional sub-packets with different coding. The receiver then combines these to piece together the original data, significantly improving reliability in poor signal areas.
- RLC/MAC Layer (Radio Link Control / Medium Access Control): In EGPRS, this layer is more advanced than in standard GPRS. It handles 1 to prevent dropped downloads when you move behind a building or into a basement.
- The “E” in EGPRS: It signifies the transition from the older GMSK modulation to 8-PSK. This transition allows the data pipe to increase from roughly 20 kbps per time slot to nearly 60 kbps per time slot.
Performance Comparison
| Feature | GPRS | EGPRS (EDGE) |
| Max Speed per Time Slot | 20 kbps | 59.2 kbps |
| Total Max Throughput | 171.2 kbps | 473.6 kbps |
| Error Correction | Standard ARQ | Incremental Redundancy |
| Window Size | 64 packets | Up to 1024 packets |
The Window Size Advantage
One of the biggest unsung heroes of EGPRS is the increased Link Layer Window Size.
- In standard GPRS, the window (the amount of data that can be sent before the receiver has to say I got it) was small.
- EGPRS increased this window size significantly. This reduced the 1een the phone and the tower, 1 the early mobile web feel much snappier.