Congestion control and resource allocation algorithms in multi-hop communication systems

Abstract

Recently, researches in wireless communication systems using multihop links have been focused due to its capability to achieve extended coverage and high capacity. Thus, Wireless Local Area Network (WLAN) mesh networks and relay communication systems using multi-hop technique are focused in this thesis. Also, among Radio Resource Management(RRM) technique, we consider congestion control and resource allocation strategies for WLAN mesh networks and relay communication systems. Recently, WLAN mesh networks are attracting significant attention. Since the Institute of Electrical and Electronics Engineers (IEEE) 802.11 Medium Access Control (MAC) protocol has been designed for single hop networks, the performance of WLAN mesh networks with multihops degrades due to congestion, and buffer overflow in intermediate Mesh Nodes (MNs). In this thesis, we propose a new congestion control scheme which applies Adaptive Modulation and Coding (AMC) scheme and effective buffer usage to enhance the performance. AMC scheme uses multiple fragmentation thresholds, modulation levels and coding rates for various data sizes according to Channel State Information(CSI). Because CSI can be used more effectively to squeeze more bits into the medium, the throughput is enhanced. Simulation results show that the proposed scheme achieves higher throughput than other congestion control schemes. Next, we propose a novel resource allocation algorithm in relay communication networks. Many schemes improving the system performance have been researched in a multi-hop relay network. Especially, the resource allocation for relay networks is the most important issue to increase the coverage and the capacity efficiently with low power consumption. However, most existing algorithms have the high complexity with additional computation time because these algorithms assign a subcarrier to the lowest capacity hop one at a time. Thus, we propose sub-optimal joint subcarrier and power allocation algorith...