An EM-based SIR Estimation Method for WCDMA Cellular Systems

• Main Authors: WEI-JUNG LEE, 李唯榮
• Other Authors: Wen-Rong Wu
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/19708888938324383784

碩士 === 國立交通大學 === 電信工程系 === 91 === In WCDMA systems, power control algorithms are used to cope with the fast channel fading. The signal to interference (SIR) ratio is a common measure for the channel condition. Thus, a fast and accurate SIR estimation method is required. Most present SIR estimation methods use pilot bits to estimate the power of interference and noise. In this thesis, we formulate the SIR measurement problem as a Gaussian mixture identification problem. Applying the expectation maximization (EM) algorithm, we are able to estimate signal and interference power using not only the pilots bits also the information bits. Since the information bits have smaller spreading factors, the estimator can have more samples. Moreover, in order to track the fasting fading, the number of samples used is small and the SIR estimate sequence is then noisy. We then apply a Kalman filter to further processing the EM-estimated sequence. The simulation results show that the proposed method can provide fast and accurate SIR estimates.