TURBO-CODED HARQ BASED MUTLI-HOP COOPERATIVE WIRELESS SYSTEM

Abstract

Wireless Communications is an ever evolving field and has been one of the rapidly growing technology sectors from a consumer, business, military and research perspective. With the explosive growth of wireless technologies, there is need to provide reliable, high bandwidth and high data rate services to meet the increasing consumer demand. Therefore, it is necessary to integrate enhanced technologies to the conventional wireless systems in order to improve these performance factors. Cooperative Communications is a promising technique addressing these performance issues beside it also provides extended coverage and mitigates multipath fading in a cost effective manner. To date, Cooperative wireless systems exist in classical three node network to achieve diversity. The concept of multi-hop relayed Cooperative wireless system is proposed to further enhance the performance in terms of BER and extended coverage range of an overall system as compared to single hop cooperative wireless system. The advantages offered by multi-hop cooperative system are the outcome of the usage of multiple distributed antennas which leads to an overall better system performance by having independent uncorrelated channel paths and finally enables the system to make best use of the benefits of macro-diversity in annex to micro-diversity. In this research, Turbo Codes with Maximum a-posteriori (MAP) decoding algorithm are integrated in multi-hop cooperative wireless system as Forward Error Correction (FEC) technique in order to combat the drastic effects of fading environment which improves the system performance in terms of BER. Use of such a powerful coding scheme leads to overall coding gain of the system. To make the system more robust, Hybrid Automatic Repeat re-Quest (HARQ) protocol is also incorporated in the system as retransmission scheme to rectify the errors that are detected at receiver end. Finally integrate all three technologies, Multi-hop Cooperative system, Turbo Codes and HARQ together to enhance the system performance. The BER results of multi-hop cooperative system justify the usage of multiple relays in cooperative wireless systems in comparison to single-hop systems. In addition the proposed technique also provides cost effective solution to get diversity gains.