Call setup for cellular ad-hoc relay systems based on TDD-OFDMA scheme

Abstract

Recently, many works have been researched on the cellular ad-hoc relay (AHR) networks to extend the service coverage of base-station (BS) and to combat the impairment of the wireless channels by combining the fixed infrastructure with the AHR technology. Most of the current works consider the mobile-stations (MSs) located within the coverage of BS. If the MSs in the outage or the transmit power deficiency want to communicate reliably, the relay communication via the AHR can be enabled. The conventional call setup schemes mainly focus on the signaling in the medium access control layer for the system access via AHR and, thus, it needs to consider the practical issues for the successful call setup. In this dissertation, we propose a call setup scheme for TDD-OFDMA based cellular AHR systems. The users that cannot obtain the direct communication link from the BS due to the outage or the power deficiency are considered. First, we propose a preamble based system access scheme, which is motivated by the facts that the preamble sequence has the good correlation property and that the cellular users always monitor the preamble signals to find the nearby BSs and to measure the link quality. In our system access scheme, the preamble for the call request is pre-defined. Frame synchronization scheme for call request preamble (CRP) transmission of the caller is presented because the ideal arrival time of the CRP transmitted by caller is during the preamble period. The mean acquisition time of the CRP and the performance of the cellular user affected by the CRP transmission of the caller are investigated. Simulation results show that the proposed scheme can be effectively used for TDD-OFDMA based cellular AHR systems. Once the adjacent cellular users (ACUs) detect the CRP, the ACUs send the ACK response message to the caller. However, the wireless communication of the caller via AHR may be not guaranteed due to the absence of the users providing the reliable relay path....