HARQ in Relay-Assisted Transmission for Machine Type Communications

Abstract

This letter describes the impact of unknown channel access delay on the timeline of the hybrid automatic repeat request (HARQ) process in the 3rd generation partnership project long term evolution (3GPP LTE) system when a relay node (RN) is used for coverage extension of machine type communication (MTC) devices. A solution is also proposed for the determination of unknown channel access delay when the RN operates in the unlicensed spectrum band. The proposed mechanism is expected to help MTC operation in typical coverage holes areas such as smart meters located in the basement of buildings.