Multiuser frequency-time domain radio resource allocation in downlink OFDM systems: Capacity analysis and scheduling methods

In this paper, we propose an adaptive multiuser frequency-time domain radio resource allocation model for the downlink OFDM systems, which efficiently exploits the time diversity, frequency diversity as well as multiuser diversity in the time, frequency and user domain, respectively. Next we give an in-depth capacity analysis of the proposed frequency-time domain radio resource allocation which achieves much higher capacity (spectral efficiency) than the conventional frequency domain resource allocation. Then according to the allocation algorithm's computational complexity, two different-complexity adaptive resource allocation algorithms-algorithm A and algorithm B-are proposed which adopt a two-step allocation method to reduce the scheduling complexity and meanwhile improve the scheduling performance. Simulation results show that though the performance of algorithm A and B is slightly different, both of the proposed algorithms yield much higher spectral efficiency and much lower outage probability than conventional OFDM-TDMA scheme or random allocation without any scheduling policy.