A Novel Initial Ranging Algorithm for WIMAX-OFDM System

摘要

In WIMAX system, OFDMA is adopted and the base station communicates with several fixed and mobile users simultaneously by allocating subcarriers in one OFDM symbol to different users. As the distances to the base station of different users are different, the synchronization technology is critical for the WIMAX-OFDM system. Normally, initial ranging and periodic ranging are adopted to estimate the transmission delay between the base station and the user, and the time synchronization is acquired by compensating the estimated time delay in transmission. Thus the near-far effect of different users is overcome and the system performance is guaranteed. In this paper, the initial ranging algorithm of the WIMAX-OFDM system is studied. According to the relevant and power character of the initial ranging code, we proposed a simplified initial ranging algorithm; the initial ranging code is detected through 4 modules: power detecting, hard decision, coarse selection and final selection. Compared with the traditional frequency domain ranging algorithm and the time domain ergodic algorithm, our algorithm has good performance and low computation complexity, and is a practical algorithm.