While rapid variations of the fading channel cause intercarrier interference (ICI) in orthogonal frequency-division multiplexing (OFDM), thereby degrading its performance considerably, they also introduce temporal diversity, which can be exploited to improve the performance. In this paper, we first derive a matched-filter bound (MFB) for OFDM transmissions over doubly selective Rayleigh fading channels, which benchmarks the best possible performance if ICI is completely canceled without noise enhancement. We then derive universal performance bounds which show that the time-varying channel causes most of the symbol energy to be distributed over a few subcarriers, and that the ICI power on a subcarrier mainly comes from several neighboring subcarriers. Based on this fact, we develop low-complexity minimum mean-square error and decision-feedback equalizer (DFE) receivers for ICI suppression. Simulations show that the DFE receiver can collect significant gains of ICI-impaired OFDM with affordable complexity. In the relatively low Doppler frequency region, bit-error rate of the DFE receiver is close to the MFB.
Bibliographical noteFunding Information:
Paper approved by C. Tellambura, the Editor for Modulation and Signal Design of the IEEE Communications Society. Manuscript received July 18, 2002; revised July 7, 2003. This work was supported through collaborative participation in the Communications and Networks Consortium, sponsored by the U.S. Army Research Laboratory under the Collaborative Technology Alliance Program, under 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. This paper was presented in part at the 36th Asilomar Conference on Signals, Systems, and Computers, Pacific Grove, CA, November 3–6, 2002.
- Doubly selective Rayleigh fading
- Interference suppression
- Orthogonal frequency-division multiplexing (OFDM)