Low-complexity End-to-End Performance Optimization in MIMO Full-Duplex Relay Systems (1311.3428v1)

Abstract: In this paper, we deal with the deployment of full-duplex relaying in amplify-and-forward (AF) cooperative networks with multiple-antenna terminals. In contrast to previous studies, which focus on the spatial mitigation of the loopback interference (LI) at the relay node, a joint precoding/decoding design that maximizes the end-to-end (e2e) performance is investigated. The proposed precoding incorporates rank-1 zero-forcing (ZF) LI suppression at the relay node and is derived in closed-form by solving appropriate optimization problems. In order to further reduce system complexity, the antenna selection (AS) problem for full-duplex AF cooperative systems is discussed. We investigate different AS schemes to select a single transmit antenna at both the source and the relay, as well as a single receive antenna at both the relay and the destination. To facilitate comparison, exact outage probability expressions and asymptotic approximations of the proposed AS schemes are provided. In order to overcome zero-diversity effects associated with the AS operation, a simple power allocation scheme at the relay node is also investigated and its optimal value is analytically derived. Numerical and simulation results show that the joint ZF-based precoding significantly improves e2e performance, while AS schemes are efficient solutions for scenarios with strict computational constraints.

• The paper introduces a joint precoding and decoding strategy that effectively mitigates loopback interference using a zero-forcing criterion.
• It derives closed-form solutions and analyzes outage performance, demonstrating improved end-to-end SNR and diversity order.
• The study explores low-complexity antenna selection schemes, offering viable alternatives for systems with limited computational resources.

Summary of "Low-complexity End-to-End Performance Optimization in MIMO Full-Duplex Relay Systems"

The paper "Low-complexity End-to-End Performance Optimization in MIMO Full-Duplex Relay Systems" provides a comprehensive analysis of the challenges and solutions associated with the implementation of full-duplex systems in Multiple-Input Multiple-Output (MIMO) relay networks. The focus is on optimizing the end-to-end (e2e) performance of amplify-and-forward (AF) cooperative networks, particularly in addressing loopback interference (LI), a significant impediment in full-duplex operations.

Key Contributions

The key contributions of this paper are twofold. Firstly, it presents a joint precoding and decoding strategy that effectively mitigates LI using a zero-forcing (ZF) criterion. This approach significantly enhances the e2e performance by providing closed-form solutions that minimize system complexity. Secondly, the paper explores various antenna selection (AS) schemes as a low-complexity alternative to full MIMO processing, offering viable solutions for systems with constrained computational resources.

Main Findings

1. ZF-based Precoding Design: The authors develop a rank-1 ZF-based precoding technique that targets LI suppression, yielding improved e2e SNR. The paper derives closed-form solutions for these schemes and provides insights into their performance through exact and asymptotic outage probability analyses.
2. Antenna Selection Schemes: The paper discusses several AS strategies, such as the optimal AS (OP AS), $\max-\max$ AS (MM AS), partial AS (PR AS), and loop interference AS (LI AS). These schemes provide different trade-offs between performance and complexity. OP AS offers the best performance with higher complexity, while LI AS is a simpler but less effective alternative.
3. Outage Performance Analysis: For both precoding and AS designs, the paper presents analytical expressions for outage probability and diversity order, crucial metrics for evaluating system reliability. The analysis shows that while precoding designs deliver higher diversity, AS schemes are beneficial in low-diversity scenarios.
4. Impact of Antenna Configurations: The paper demonstrates how different numbers of antennas at source, relay, and destination nodes affect system performance. For instance, configurations with more antennas at the relay can enhance performance without significantly increasing complexity.
5. Power Allocation Strategy: A simple yet effective power allocation scheme is proposed to mitigate zero-diversity behavior in full-duplex systems. The authors provide optimal parameters for power allocation, balancing between computational efficiency and performance improvement.

Practical Implications and Future Research

The findings of this paper have practical implications for the deployment of full-duplex relay systems in wireless networks, facilitating more efficient spectrum usage without compromising on interference handling. The closed-form solutions and antenna selection strategies can be directly applied to various scenarios in modern wireless communication systems, such as LTE-Advanced and next-generation Wi-Fi.

Future research could explore the integration of these techniques into heterogeneous networks and cognitive radio systems, potentially expanding the applicability of full-duplex solutions. Developing adaptive algorithms that can dynamically switch between precoding and AS strategies based on real-time channel conditions could further enhance system robustness and flexibility.

In conclusion, this paper offers a significant contribution to the optimization of MIMO full-duplex relay systems, presenting solutions that are both innovative and practical for real-world applications. The balance between performance enhancement and complexity reduction achieved through its proposed methods positions this work as a valuable resource for ongoing advancements in wireless communications.