The Double Retransmission Mechanism Research In LTE System

Mobile communication has spread to people’s daily life. With the developmentof Mobile Internet, the pressure of wireless network surges. So LTE arises at thehistoric moment for a higher rapid rate compared with3G. As the transition to4G,LTE not only embodies the latest MIMO and OFDMA technology, also flattensnetwork architecture to simplify the system and reduce the processing delay formeeting high speed communication. Because of time-varying wireless channeles inLTE, however, it’s inevitable to emerge data errors. To ensure the reliabletransmission, it is designed elaborately for double retransmission mechanism whichconsists of HARQ of MAC and ARQ of RLC. Most retransmissions of data blocksare excuted and managed by MAC HARQ providing fast reransmission, whileretransmission of RLC just plays a role of complement. The main reason of doublelayer retransmission structure is the tradeoff of efficiency and reliability of statusreport feedback.A comprehensive and in-depth study of the double layer retransmission of LTEappears in this paper. Firstly, we analyze the MAC layer of HARQ which includesHARQ retransmission timer, receiving treatment and the involved physical layerprocedure. On this basis, a new HARQ retransmission scheme is proposed. The newscheme combines HARQ with physical layer code block segmentation andcombination. And the simulation results show its excellent performance. Secondly, weresearch the AM entity of RLC layer. Emphasis is ARQ about sending and receivingwindow and RLC PDU structure. Besides, the design of AM entity have been finished,and we present some exceed schemes of buffer controller in the sender and receiver.To complete the retransmission perfactly, we provide the encapsulation process ofRLC PDU at transmitting side and sort the receiving RLC PDU by list at the receivingside. Finally, we analyse the work process of double retransmission and find itsshortcomings from the perspective of double retransmission. So a cross layeroptimization scheme is proposed. Through introducing HARQ process concept toRLC layer, double layers share MAC HARQ feedback information. The performancesimulation verifies the excellent performance of retransmission delay under differentconditions.