Performance Evaluation of Time Alignment Control under High-Mobility Environment for Dynamic Parameter Controlled OF/TDMA

Abstract

This paper proposes a time alignment control (TAC) for reducing an influence of multiple access interference (MAI) due to propagation delays (PDs) in uplink transmission from multiple mobile stations (MSs) to an access point (AP) for an orthogonal frequency division multiple access (OFDMA) based mobile communication system. In addition, this paper presents our evaluation of the proposed TAC as applied to dynamic parameter control orthogonal frequency and time division multiple access (DPC-OF/TDMA) which has been suggested for use in new generation mobile communication system. This paper also proposes several formats for an activation slot (ACTS) in which the GIs are lengthened in order to avoid the MAI because the TAC cannot be performed yet in an initial registration of the MSs. Computer simulation elucidates that lengthening the GIs of data symbols in the ACTS adequately to compensate a maximum delay improves the transmission performance of the ACTS at the initial registration without PDs compensation. The simulation also elucidates that the proposed TAC is performed to reduce the influence of the MAI effectively and that updating the estimates of the PDs every certain period is needed to compensate the PDs accurately under high-mobility environment.