Orthogonal Projection With Optimized Reserved Subcarriers Mapping for Sidelobe Suppression in OFDM Systems

Abstract

As an efficient sidelobe suppression technique for orthogonal frequency-division multiplexing (OFDM) systems, the orthogonal projection is capable of achieving deep suppression while maintaining low complexity. However, the conventional orthogonal projection for sidelobe suppression (SSOP) with the uniform distribution of reserved subcarriers suffers from noise amplification in data recovery, resulting in a degradation of bit-error-rate (BER) performance. To tackle this problem, an improved SSOP with an optimized mapping of reserved subcarriers (SSOP-OM) is proposed in this paper. Additionally, a fast search algorithm is proposed to obtain this optimized distribution. By maximizing the signal-to-noise ratio (SNR) at the receiver, SSOP-OM can obtain more than 3-dB SNR gain for a 16-QAM-modulated OFDM system with 128 subcarriers and 6 of them reserved over conventional SSOP at the BER of 10-3. In addition, the more reserved subcarriers or the more subcarriers are used in the OFDM, the higher the SNR gain can be achieved. The theoretical analysis and simulations are provided to validate the advantage of the proposed SSOP-OM over the conventional SSOP in terms of BER in both AWGN and multipath channels.

Keywords

• OFDM
• sidelobe suppression with orthogonal projection (SSOP)
• noise amplification
• optimized mapping of reserved subcarriers