Resource management for infrastructure-based two-hop fixed relay systems which are applicable to TDD-FH-OFDMA based cellular systems with sectorization is proposed in this paper. The severe interference problem caused by both inter-sector and inter-cell can be tackled by employing 6-sector directional antennas combined with the resource allocation. The simulation results demonstrate that at the outer-region of the cell, the high data rate service coverage can be extended.

In this letter, two receive diversity combining techniques are proposed for cooperative relay systems based on single-carrier frequency division multiple access (SC-FDMA) when relay station (RS) transmits the received signals from multiple mobile stations (MSs) together using one large size discrete Fourier transform (DFT). A simplified-MRC (S-MRC) technique performs diversity combining in the time-domain by using the estimated channel weights and initial estimates obtained by the SC-FDMA signal detector. An interference rejection-MRC (IR-MRC) technique performs diversity combining in the frequency-domain by adjusting the DFT spreading size at the receiver. It is shown by computer simulation that the proposed receive combining techniques achieve a significant diversity gain over the conventional techniques.

The time division duplex cellular system can support various downlink and uplink traffic ratios by setting the downlink and uplink transmission periods appropriately. However, it causes severe co-channel interference problem when some cells are active in the downlink while the others are in the uplink [2]. To mitigate this problem, a resource allocation scheme combined with sectorization is proposed for orthogonal frequency division multiple access. Simulations demonstrate that the proposed scheme improves both spectral efficiency and outage performance compared to the conventional allocation schemes.

In this paper, a new handover procedure for OFDM-based multi-hop relay systems is proposed to reduce handover overhead by distinguishing an inter-cell handover event from an intra-cell handover event at the level of the physical layer using a preamble with a hierarchical design. A Subcell ID concept used to identify relay station in a cell is proposed in the hierarchical design that works in conjunction with the existing Cell ID used to identify base station. The proposed handover procedure can simplify the scanning procedure and skip/simplify the network re-entry procedure, resulting in a significant reduction in handover overhead.