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Low-Complexity OSIC Equalization for OFDM-Based Vehicular Communications

Vehicular communication systems are usually equipped with orthogonal frequency division multiplexing (OFDM) transceivers that operate on rapidly changing radio propagation environments, which results in high Doppler and delay spreads. More specifically, in these environments, the experienced channels are doubly selective and introduce severe intercarrier interference (ICI) at the receiver. An effective ICI mitigation technique is desired as a constituent part of an ordered successive interference cancellation (OSIC) architecture, which turns out to be computationally efficient, since it may require the solution of linear systems with multiple right-hand sides. To decrease the complexity, several techniques suggest mitigating the ICI by considering only a small number of adjacent subcarriers. However, this approximation introduces an error floor, which may result in unacceptable bit error rates (BER) at high signal-to-noise ratio regimes. In this paper, we propose a new OSIC equalization technique based on an iterative Galerkin projection-based algorithm that reduces the computational cost without sacrificing the performance gains of the OSIC architecture. Furthermore, we suggest a new serial/parallel cancellation architecture that extends the OSIC and has the potential to completely cancel the experienced ICI introduced in high-mobility scenarios. Extensive Monte Carlo experiments have been carried out to validate the accuracy of our framework, revealing intriguing tradeoffs between achieved BER and complexity, and highlighting the importance of designing low-complexity OSIC schemes for OFDM systems operating over double selective channels.