Estimation of Carrier Frequency Offsets for Uplink OFDMA Using Hybrid Particle Swarm Optimization and Gravitational Search Algorithm

• Main Authors: Ming-Yu Tsai, 蔡明佑
• Other Authors: 譚旦旭
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/69y3dw

碩士 === 國立臺北科技大學 === 電機工程系研究所 === 100 === In orthogonal frequency division multiplexing (OFDM) system, carrier frequency offset (CFO) is an important factor that destroys orthogonality among subcarriers. This will lead to inter-carrier interference (ICI) and therefore significantly degrades system performance. Moreover, in the uplink orthogonal frequency division multiple access (OFDMA) system, the base station will receive multiple CFOs from multi-user which causes multiple access interference (MAI), further degrading system performance. Hence the research on CFO estimation has received much attention in recent years. This study develops an evolutionary algorithm by taking the advantages of both the particle swarm optimization (PSO) and gravitational search algorithm (GSA) for CFOs estimation in two different systems, which are null subcarrier-based system (System-1) and [21,22] system (System-2). A series of experiments is conducted over Rayleigh fading channel with various users and the results indicate that performance of the proposed hybrid scheme is superior to other methods. In addition, System-1 and System-2 have comparable performances, but System-1 has much higher subcarrier utilization efficiency.