A new ranging method for OFDMA systems

We present a new initial ranging method for OFDMA systems such as IEEE 802.16a. First, a new orthogonal ranging signal design is proposed by which an efficient, low-complexity multi-user ranging signal detection is developed. Based on the ranging signal detector results, power estimation for the detected ranging subscriber stations is performed. Then, by utilizing the proposed orthogonal ranging signal design together with the redundancy introduced by cyclic prefixes, a new iterative multi-user timing offset estimator is presented. Compared with the existing methods utilizing the CDMA-type ranging codes (in frequency-domain) defined in IEEE 802.16a, the proposed method achieves a better performance and greater robustness against multi-user interference and multi-path fading channels.