QoS-aware resource allocation in OFDMA-based wireless telecommunication systems

Abstract

Recently, an orthogonal frequency division multiple access (OFDMA), which is a multi-user version of the OFDM digital modulation scheme, has emerged as one of the prime multiple access schemes for broadband wireless networks. OFDMA can overcome frequency-selective fading and the inter-symbol interference problem. Moreover, the adaptive subcarrier allocation allows OFDMA system to achieve higher spectral efficiency by multiuser diversity. Subcarrier and power allocation plays important role to enhance the system throughput and to maintain the QoS among the users. This study mainly focuses on the radio resource allocation considering QoS for OFDMA-based wireless telecommunication systems. First, we study on satisfying actual client demand in OFDMA downlink system. Due to the limitations of wireless resources, some clients may not be able to obtain their desired throughput. To minimize conflicting client demands, we propose a goal programming technique which sets a goal for each client. As the goal is not a strict constraint, the system can allocate resources flexibly and generate feasible solutions consistently. In the proposed approach, we aim to minimize the weighted sum of client dissatisfaction and propose an efficient algorithm for real-time applications. The proposed algorithm can reduce the amount of dissatisfaction significantly, especially with a large number of users. Then, we extend our scope to a cooperative OFDMA system. Cooperative system allows single-antenna users to transmit using the antennas of other users, so that the users form a virtual antennas array. By cooperative transmission, users experiencing deep fading can transmit in association with relays and get better channel gain. We aim to evaluate the performance of user-cooperative transmission in multiuser OFDMA systems while optimally allocating bandwidth and transmission power to each source/relay. We consider the problem of minimizing the total transmission power while satisfying e...