Tham khảo tài liệu 'quality of service and resource allocation in wimaxfig part 15', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 15 Cost Effective Coverage Extension in Based Mobile WiMAX Systems Se-Jin Kim Byung-Bog Lee Seung-Wan Ryu Hyong-Woo Lee and Choong-Ho Cho Dept. of Computer and Information Science Korea University Republic of Korea 1. Introduction Recently there have been numerous standardization activities for making the system highly effective in supporting mobile users based on orthogonal frequency division multiple access OFDMA with Time Division Duplex TDD mode in IEEE Standard 2005 and WiMAX Forum . Standardization activities of the system were completed in 2005 and currently enhancements of the standard are under discussion. One such enhancement effort is cell coverage extension and link throughput enhancement which was studied in TG in 2008 . In order to achieve these goals the TG introduces mobile multi-hop relay technology to the system. The other enhancement effort is being discussed in TG. The system called the gigabit WiMAX makinly aims to enhance system throughput up to 1Gbps. Besides this system aims to support legacy standards including the and to interworking with other wireless systems such as 3GPP LTE and IMT-advanced system in WiMAX Forum and Lee et al. 2006 . In particular in Korea the standard-based wireless broadband WiBro system was developed in 2005 and WiBro service was launched in 2006 covering isolated areas in Seoul. Since the initial launch WiBro service providers have been trying to extend service areas from Seoul to regions nationwide. In order to cover the entire region of Korea however deployment cost for the traditional infrastructure consisting of only Base Stations BSs is estimated to be astronomical. For this reason it is necessary to adopt a cost-effective service coverage extension method and the mobile multi-hop relay MMR WiBro system is considered as a strong candidate .
