Joint Power Adjustment and Interference Mitigation Techniques for Cooperative Spread Spectrum Systems

TL;DR

This paper introduces joint power allocation and interference mitigation algorithms for cooperative spread spectrum systems with relays, improving performance and capacity through adaptive optimization techniques.

Contribution

It proposes a novel joint constrained optimization framework and adaptive algorithms for power allocation and interference suppression in cooperative relay systems.

Findings

Significant performance gains over non-cooperative systems.

Enhanced capacity with optimized power allocation.

Effective interference mitigation through adaptive algorithms.

Abstract

This paper presents joint power allocation and interference mitigation techniques for the downlink of spread spectrum systems which employ multiple relays and the amplify and forward cooperation strategy. We propose a joint constrained optimization framework that considers the allocation of power levels across the relays subject to an individual power constraint and the design of linear receivers for interference suppression. We derive constrained minimum mean-squared error (MMSE) expressions for the parameter vectors that determine the optimal power levels across the relays and the linear receivers. In order to solve the proposed optimization problem efficiently, we develop joint adaptive power allocation and interference suppression algorithms that can be implemented in a distributed fashion. The proposed stochastic gradient (SG) and recursive least squares (RLS) algorithms mitigate the interference by adjusting the power levels across the relays and estimating the parameters of the linear receiver. SG and RLS channel estimation algorithms are also derived to determine the coefficients of the channels across the base station, the relays and the destination terminal. The results of simulations show that the proposed techniques obtain significant gains in performance and capacity over non-cooperative systems and cooperative schemes with equal power allocation.