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GPRS : General Packet Radio System - page 12 / 20

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12 / 20

Networks: L17

12

Coding schemes

nine more schemes introduced for EDGE – MCS1 to MCS9

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MCS1 to MCS4 for GMSK, MCS5 to MCS9 for 8PSK

GPRS tops out at 20kbs, EDGE goes up to 59,2kbs

Retransmission

a packet sent using a higher coding scheme that is not properly received can be retransmitted with a lower coding scheme

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requires changes in payload sizes to take account of extra error correction bits

GPRS required same coding scheme to be used again in retransmissions

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even if radio environment had changed

EDGE has a faster scheme for analysing the radio link quality

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allows faster adaptation to the current radio environment

Interleaving

entire block retransmitted in GPRS if any of the 4 bursts not received correctly

EDGE interleaves over two bursts instead of four – better likelihood of success

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