Spectral Precoding for Out-of-band Power Reduction under Condition Number Constraint in OFDM-Based System

TL;DR

This paper introduces a joint spectral precoding scheme for OFDM systems that significantly reduces out-of-band power leakage while maintaining receiver performance, using matrix operations and condition number constraints.

Contribution

It proposes a novel joint spectral precoding method with an algorithm to design the precoding matrix under condition number constraints, improving spectrum shaping and receiver performance.

Findings

Significant reduction in out-of-band power leakage.

Effective spectrum envelope with maintained receiver performance.

The proposed scheme outperforms existing methods in simulations.

Abstract

Due to the flexibility in spectrum shaping, orthogonal frequency division multiplexing (OFDM) is a promising technique for dynamic spectrum access. However, the out-of-band (OOB) power radiation of OFDM introduces significant interference to the adjacent users. This problem is serious in cognitive radio (CR) networks, which enables the secondary system to access the instantaneous spectrum hole. Existing methods either do not effectively reduce the OOB power leakage or introduce significant bit-error-rate (BER) performance deterioration in the receiver. In this paper, a joint spectral precoding (JSP) scheme is developed for OOB power reduction by the matrix operations of orthogonal projection and singular value decomposition (SVD). We also propose an algorithm to design the precoding matrix under receive performance constraint, which is converted to matrix condition number constraint in practice. This method well achieves the desirable spectrum envelope and receive performance by selecting zero-forcing frequencies. Simulation results show that the OOB power decreases significantly by the proposed scheme under condition number constraint.