Abstract-Two-way relaying promises considerable improvements on spectral efficiency in wireless relay networks. While most existing works focus on physical layer approaches to exploit its capacity gain, the benefits of two-way relaying on upper layers are much less investigated. In this paper, we study the cross-layer design and optimization for delay quality-of-service (QoS) provisioning in two-way relay systems. Our goal is to find the optimal transmission policy to maximize the weighted sum throughput of the two users in the physical layer while guaranteeing the individual statistical delay-QoS requirement for each user in the datalink layer. This statistical delay-QoS requirement is characterized by the QoS exponent. By integrating the concept of effective capacity, the cross-layer optimization problem is equivalent to a weighted sum effective capacity maximization problem. We derive the jointly optimal power and rate adaptation policies for both three-phase and twophase two-way relay protocols. Numerical results show that the proposed adaptive transmission policies can efficiently provide QoS guarantees and improve the performance. In addition, the throughput gain obtained by the considered three-phase and twophase protocols over direct transmission is significant when the delay-QoS requirements are loose, but the gain diminishes at tight delay requirements. It is also found that, in the two-phase protocol, the relay node should be placed closer to the source with more stringent delay requirement. Index Terms-Cross-layer optimization, two-way relaying, quality-of-service (QoS), delay-bound violation probability, effective capacity, resource allocation. The explosive developments of wireless communication have brought us into a new era where higher data transmission rates and diverse quality-of-service (QoS) provisioning are desperately expected. Real-time applications, such as voice over IP and video streaming, which are highly delay-sensitive, need reliable QoS guarantees. The design merely at the physical layer may not ensure the desired QoS requested by the service from upper layers. Only through the interaction and optimization between different layers can such QoS guarantees be fulfilled. This kind of cross-layer approach relaxes the layering architecture of the conventional network model and brings remarkable performance enhancement, which in turn could result in high complexity. Therefore, to develop efficient cross-layer methods with small information flows between layers is interesting from both theoretical and practical perspectives.
Jointly optimal power and rate adaptation policies were derived in REF for two-way relaying protocols by solving a weighted-sum EC maximization problem.
Cross-Layer Optimization of Two-Way Relaying for Statistical QoS Guarantees
IEEE Journal on Selected Areas in Communications, Special Issue on Theories and Methods for Advanced Wireless Relays, 2012
Mathematics Computer Science