Chapter 12

Retransmission Protocols

Abstract

In LTE, two retransmission mechanisms are used. Retransmissions of missing or erroneous data units are handled primarily by the hybrid-ARQ mechanism in the MAC layer, complemented by the retransmission functionality of the RLC protocol. This chapter describes the details of both these protocols, as well as explaining why the use of two complementing protocols is beneficial.

Keywords

hybrid ARQ; retransmission; soft combining; RLC; in-sequence delivery

The LTE downlink and uplink transmission schemes have been described from a physical layer perspective in Chapters 10 and 11 respectively. In this chapter, the operation of the two mechanisms responsible for retransmission handling in LTE, the MAC and RLC ...

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