Resource management in OFDM-based wireless networks with cooperative relays

Abstract

In these days, various kinds of Internet services and wide use of portable mobile devices increase the demand for wireless Internet services greatly. Because of the growing demand for high data rate services, wireless communication technology has been being developed from voice the oriented 1st generation mobile communication to the current high technology mobile communication. In forthcoming 4th generation (4G) mobile communication, technology and standard are being prepared for services that can provide ultra-high data rate to mobile users and for commercialization of 4G mobile communication system, which could be achieved in about 2015. Recently, orthogonal frequency division multiplexing (OFDM) has emerged as one of the promising techniques that can enable ultra-high data rate services. OFDM can overcome the frequency selective fading and inter-symbol interference problem. Also, cooperative relay technology enables enlarging the coverage area, increasing capacity at cell border, eliminating blinding spots and reducing transmit power. For these reasons, relay technology is also considered as an effective scheme for 4G. Since subdivided and newly added components make mobile communication systems more complex to operate, an efficient wireless resource management in mobile communication systems has become evidently important. This study mainly focuses on the wireless resource management for OFDM based wireless communication systems with cooperative relays. First, we study on a subcarrier and power allocation algorithm which maximizes system throughput while guaranteeing QoS requirement of users in user-cooperative OFDMA up-link system. In the user-cooperative system, optimizing system performance is challenging because the new issues such as selection of sources and relays and assignment of subcarrier and power for relay transmission must be considered. We introduce the simplified relay channel gain which converts cooperative transmissions into direct transmis...