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.
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 ...