Power loading algorithms improve the data rates of orthogonal frequency division multiplexing (OFDM) systems. However, they require the transmitter to have perfect channel state information, which is impossible in most wireless systems. We investigate the effects of imperfect (and thus partial) channel feedback on the throughput of OFDM systems. Two channel uncertainty models are studied: 1) the ergodic model, where average rate is the figure of merit and 2) the quasi-static model, where outage rate is relevant. Rate-power allocation algorithms are developed. The throughput achieved by these algorithms and the effects of channel multipath are investigated analytically and with simulations.
Bibliographical noteFunding Information:
Manuscript received February 24, 2003; revised September 29, 2003, February 24, 2004; accepted February 26, 2004. The editor coordinating the review of this paper and approving it for publication is L. I. Vandendorpe. This work was prepared through collaborative participation in the Communications and Networks Consortium sponsored by the U. S. Army Research Laboratory under the Collaborative Technology Alliance Program, Cooperative Agreement DAAD19-01-2-0011. The U. S. Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation thereon.
- Adaptive modulation
- Average rate
- Orthogonal frequency division multiplexing (OFDM)
- Outage rate
- Partial channel state information (CSI)