Evaluation of Link Adaptation Methods in Multi-User OFDM Systems with Imperfect Channel State Information

Paper in proceeding, 2011

Link adaptation has shown to be a method of improving the wireless communication system throughput over quasi-static fading channels. Link adaptation, however, requires channel quality information (CQI) at the transmitter side, which is difficult to obtain accurately. Within the European WINNER project, a low complexity, near optimum, mutual information based adaptive coding and modulation (MI-ACM) link adaptation scheme was proposed. Previous work, however, only focused on evaluating this scheme with perfect CQI and without considering the potential signaling overhead introduced by this algorithm. In this paper, the performance of the MI-ACM algorithm is evaluated and compared to the link adaptation framework used in LTE. A more realistic multi-user scenario is studied by taking the channel prediction error and control signaling constraint into account. Simulation results show that the MI-ACM algorithm is useful only in a few types of scenarios, e.g., system with few users having low average SINR, low velocities with channels presenting substantial frequency selectivity.