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GPRS and EDGE bit-rates

This page tries to outline the possible achievable GPRS bit-rates.

There are multiple aspects that relate to the problem
  • channel coding, which in turn depends on
    • capabilities of the BTS and MS
    • performance of the radio channel
  • multi-slot operation, which depends on
    • capabilities of the BTS and MS
    • contention on the radio channel / resource sharing by multiple phones

channel coding

Depending on the characteristics of the radio channel (interference, bit errors, link quality, C/I), the network will
dynamically select the best coding scheme. The lower numbers (CS-1/MCS-1) have the most error coding and are very
resiliant but have little throughput. MCS-9 has no error correction coding at all, but t

GPRS channel coding

Each of the 8 GSM time-slots can operate i a number of different coding schemes:

Coding Scheme kbit/s
CS-1 8.0
CS-2 12.0
CS-3 14.4
CS-4 20.0

EDGE channel coding

Each of the 8 GSM time-slots can operate i a number of different coding schemes:

Coding Scheme kbit/s
MCS-1 8.80
MCS-2 11.20
MCS-3 14.80
MCS-4 17.60
MCS-5 22.40
MCS-6 29.60
MCS-7 44.80
MCS-8 54.54
MCS-9 59.20

multi-slot capabilities

BTS side

BTS equipment is normally capable to run all timeslots in GPRS mode. If you're running a single-TRX small BTS, the first timeslot is always allocated for the BCCH/CCCH, leaving 7 time-slots available for voice (TCH) and data (PDTCH).

For example, a total of 7 time-slots in MCS-9 coding scheme would render
59.20 kbps * 7 = 414.40 kbps

MS side

On the MS (phone) side, things are not that simple. Normally, phones can not decode all 7/8 time-slots, as they operate in half-duplex mode and need some time for transmit, too. The capabilities of each phone are specified as so-called multislot class

For a table of multislot classes, please see 3GPP TS 45.002, or a summarized version at wikipedia.

multi-slot class 10

For example, a phone with EDGE multislot class 10 permits for a total of 5 active time-slots, which can be either 4+1 (4 downlink, 1 uplink) or (3+2) (3 uplink, 2 downlink).
Under ideal radio conditions (MCS-9), such a phone can thus reach the following two bit-rates:
Coding Scheme multislot downlink uplink
MCS-9 4+1 236.80 59.20
MCS-9 4+2 177.60 118.40

multi-slot class 32

Coding Scheme multislot downlink uplink
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