The Scheme to Improve the Performance of Initial Ranging Symbol Detection with Common Ranging Code for OFDMA Systems

In orthogonal frequency division multiple access (OFDMA) systems, timing synchronization in uplink is accomplished by an initial uplink synchronization called an initial ranging process. The base station´s receiver synchronizes the symbol timing to any user´s symbol and the other user´s symbols have some symbol timing offset (STO). Linear phase shift is occurred by each user´s STO in an OFDMA symbol. The multiple access interference (MAI) caused by the summation of each user´s linear phase shift degrades the performance of the ranging code detection. In this paper, we propose an initial ranging symbol structure with common ranging code for phase shift estimation and compensation