Resource allocation for heterogeneous quality of service in orthogonal frequency division multiple access systems

Abstract

Recently, the focus of the communication technology is moving forward to beyond 3rd generation or 4G. 4G has many requirements and challenges: high data rate, handoff, quality of service, low cost, traffic asymmetry and so on. Among these, the noticeable requirement is very high data rate over the wireless channel environment. To satisfy this requirement, 4G is expected to use broadband, which may be vulnerable in a wireless environment. Among various multiple access technologies, orthogonal frequency division multiple access (OFDMA) is regarded as a good candidate technology due to the robustness against multi-path environment. Another important feature of 4G is heterogeneous quality of services (QoSs). The feature makes wireless communication system more complex. Thus, the existing schemes which consider homogeneous services are easily failed to achieve good system performance for resource allocation. To overcome such performance degradation, in this thesis, we deal with resource allocation considering heterogeneous QoS in OFDMA systems. In Chapter 2, we are interested in new duplex scheme to support various duplex services in OFDMA systems. Duplex scheme represents how to support DL and UL. There exist two traditional duplex schemes: frequency division duplex (FDD) and time division duplex (TDD). However, the duplex schemes are not proper for OFDMA systems, since they cannot support the flexibility of OFDMA system fully. To overcome this limitation and enhance the efficiency and flexibility of the OFDMA system, dynamic hybrid duplex (DHD) is proposed in this chapter. It is a kind of cross-layer approach that considers the user’s traffic, channel status and physical layer information to obtain the optimized duplexing. The OFDMA system with multiple service classes is considered in the next chapter. Each service class has a priority so that the prioritization between service classes can be reflected. In order to obtain good system performance and support...