Queueing-Aware Weighted-Round-Robin Subchannel Allocation for Multi-service OFDM Systems

• Main Authors: Heng-Yi Wu, 吳恆毅
• Other Authors: Min-Kuan Chang
• Format: Others
• Language: en_US
• Online Access: http://ndltd.ncl.edu.tw/handle/05225901548040150544

碩士 === 國立中興大學 === 電機工程學系所 === 95 === As we move toward the next generation wireless communication systems, providing the quality of service (QoS) to multimedia transmission in the wireless network is an attracted intensive research. To meet this problem, only considering the single-layer scenario with the separate optimal solutions to each layer does not provide adequate supports for multimedia applications in crowded wireless networks. To cope with this job, devising a system model with cross-layer categories is necessary. Certain layered strategies can be implemented simultaneously in several layers and, hence, the in-depth understanding and comparative evaluation of those strategies through the negotiation between layers can lead into a well-handled system. In this dissertation, a novel resource allocation algorithm is proposed to allocate subchannels and control the queueing capacity in multi-service orthogonal frequency division multiplexing (OFDM) systems. By decomposing this algorithm into two components, namely WRR scheduler and switch-based subchannel allocator, efficient resource management is realized. Specifically, the number of subchannels to be assigned to each stream is first determined by WRR scheduler, which is founded on weighted round robin (WRR) with weight modification. Such a weight modification adapts to the service required rate and queueing variation and tackles with the unfairness inherent in conventional resource allocation mechanisms as possible. Secondly, the responsibility of the switch-based subchannel allocator is to assign subchannels with a specifically probabilistic distribution for streams. One distinguishing feature of the proposed approach is the ability of maintaining the queueing length of streams. This feature can help guarantee the delay within a bound according to Little’s law and can benefit delay constraint traffic for Expedited Forwarding (EF) class services. In addition, the proposed mechanism is combined with adaptive modulation to make more efficient utilization of subchannels. The proposed mechanism is validated through simulation. The simulation results have shown the better capability of maintaining queueing length and the fairness that can be achieved by the proposed mechanism.