Study on Performance Enhancement in Wireless Relay Networks

• Main Authors: Lin, Tzu-Ming, 林咨銘
• Other Authors: Chen, Wen-Tsuen
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/59863655709722511451

博士 === 國立清華大學 === 通訊工程研究所 === 102 === Wireless relay network is a low-cost solution for extending the service coverage and increasing the throughput of the conventional single-hop wireless network. Introducing RNs into the traditional wireless communication system has also been proven to be a viable way to expand system capacity and reduce Capital Expenditure (CAPEX) and Operational Expenditure (OPEX) [2]. Recently, relay technology has been adopted to enhance the coverage and performance of wireless networks such as WiMax and LTE-A. Mobile relay is also adopted as a special application of relay network to serve people in movement and considered to support communication services high speed mobile networks. By deploying a relay network, an enhanced node B (eNB) can provide services to user equipments (UEs) through relay links. For a mobile relay scenario, an RN establishes backhaul links with the serving donor eNB (DeNB), and coordinates control and data flows for UEs. Because the relay transmissions are conducted through multiple radio links, using relays to forward packets will induce new transmission and handover problems. This dissertation discusses the performance issues of fixed and mobile relays, especially on overhead and latency. First, conventional transmission schemes require an RN to store and process each packet before the destination is identified, and thus introduce extra processing and buffering overheads on the RN. In this dissertation, we propose a simple and efficient forwarding scheme which multiplexes bursts of packets for the UEs attached to the same access RN and switches packet bursts in an end-to-end manner to enhance the transmission efficiency. Second, it was observed that an improper ARQ strategy increases latency, blocked packets and workloads on a multi-hop relay network. To handle the ARQ problem, this dissertation proposes a new relay ARQ scheme providing efficient acknowledgement scheme to reduce transmission latency and also the number of blocked packets. In the mobile relay scenario, the relay network suffers from heavy signalling overhead since the vehicle moves in high speed, causing the mobile RN to change the serving DeNB frequently. Enhanced measurement and handover schemes are provided to solve the problems of message overhead and handover latency in the mobile relay systems. Furthermore, this dissertation also provides analytic models to evaluate the performance of the proposed schemes. Simulation results also validate the proposed analytic models and demonstrate that the proposed schemes can solve the addressed problems.