Cross-layer design of ranging code expansion in OFDMA BWA network

Zadoff-Chu (ZC) sequence has been proposed as the contention based ranging preamble code (RPC) in 3GPP LTE and IEEE 802.16m specifications. The performance of the initial ranging process is affected by the number of available RPCs. In scenarios with high mobility and large round-trip delay (RTD), however, the number of available RPCs is limited; this would result in a higher collision probability. In this paper, we propose two efficient schemes to reduce the collision probability, namely ranging preamble codes division (RPCD) and ranging preamble codes partition (RPCP). Both schemes can effectively increase the number of available RPCs in the initial ranging process. The superiorities of the proposed schemes are demonstrated via computer simulations.