Cross-Layer Design And Optimization Of Two-Way Relaying For Statistical QoS Provisioning

Two-way relaying promises considerable improvements on spectral efficiency in wireless relay networks. Most existing works focus on phys-ical layer approaches to exploit its capacity gain, however, convention-al physical-layer design cannot guarantee upper layer service needs (e.g. delay), which should be fulfilled through cross-layer optimization among different layers. For the cross-layer design for two-way relaying, it has been much less studied so far, and the benefits of two-way relaying on up-per layers are not fully investigated as well. To deal with these problems, in this thesis, 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, which is the only requested information exchanged between lay-ers. By integrating the concept of effective capacity, the cross-layer opti-mization problem is equivalent to a weighted sum effective capacity maxi-mization problem. Based on the equal time assignment, we first derive the jointly optimal power and rate adaptation policies for both three-phase and two-phase two-way relay protocols. Then, we propose the optimal time allocation policy for the two protocols under the peak power constraint. Numerical results show that, compared with the strategies without adap-tation, the proposed adaptive transmission policies can efficiently provide QoS guarantees and improve the performance. In addition, the through-put gain obtained by the considered three-phase and two-phase two-way relay protocols over direct transmission is significant when the statistical delay-QoS requirements are loose, but the gain diminishes at tight delay requirements. It is also found that the relay node in the two-phase protocol should be placed closer to the source with more stringent delay require-ment. Last, the performance gains brought by time allocation are much less than the improvements resulting from the power adaptation.