Search

In this paper, we consider a wireless cooperative multimedia decode-and-forward network wherein one relay may assist multiple source-destination pairs. By exploiting the global channel state information at the relay, we propose a power allocation, a time allocation and an iterative joint power-time allocation algorithm to minimize the sum expected distortion. Firstly, we separately optimize the relay's transmission power and the system transmission time allocated to each source-destination pair such that the sum expected distortion can be minimized. Then, we propose an iterative joint power-time allocation algorithm subject to the relay's total power constraint to further improve the distortion performance. The proposed iterative algorithm is guaranteed to converge to an optimal, despite not necessarily globally optimal, point and can achieve the minimum sum expected distortion among all the schemes. ©2009 IEEE.

This paper has been withdrawn by the authors as they feel it inappropriate to publish this paper for the time being., Comment: This paper has been withdrawn by the authors

In the past few decades, we have witnessed a significant development of wireless networks and applications, e.g., cellular systems and wireless ad hoc networks. Unfortunately, unlike its wireline counterpart, wireless communications is accompanied by some intrinsic challenges, such as randomly faded channels, which limit the achievable performance of the network. As a natural remedy, multiple-input multiple-output technology has been proposed to enhance the spectral efficiency through spatial multiplexing, and to improve the robustness and reliability of wireless links by providing spatial diversity gain. Nonetheless, in many wireless applications, the transmitters may not be able to support multiple physical antennas due to the size, complexity, cost or other constraints. Recently, a promising technique, known as cooperative communications, has been becoming increasingly popular thanks to its ability to create spatial diversity without packing multiple antennas physically into small-size mobile nodes. Given cooperative communications, many critical issues have arisen. In particular, statistical Quality-of-Service (QoS) guarantee and reliability provisioning are becoming even more important in the design of future cooperative networks. In the first part of this thesis and by considering a cooperative multi-relay network, we propose a time-slot allocation scheme to increase the system throughput subject to the queue-overflow statistical QoS requirement. Initially, assuming a block fading channel, we derive an algorithm in which each relay is allocated a time slot of optimal length during the cooperation phase. The analysis indicates that when the QoS requirement is loose, only the relay with the best average channel condition should be selected for cooperation. On the other hand, when the QoS requirement becomes more stringent, more relays should participate in cooperation. The asymptotic case when either the transmit power or the number of relays goes to infinity is

In this paper, we propose a resource allocation scheme to maximize the system throughput subject to the queue overflow Quality-of-Service (QoS) requirement for wireless cooperative networks. Specifically, the considered network consists of one source-destination pair and N relays that can detect and forward the source's message. By integrating the concept of effective capacity with cooperative relay networks, the proposed scheme allocates each relay a time slot of optimal length during the cooperation phase, based on the channel statistics. Our analysis shows that selecting the relay with the best channel condition for cooperation is optimal when no QoS requirement is considered, while more relays should participate in cooperation when the level of QoS requirement becomes more stringent. ©2008 IEEE.

In this paper, we propose a limited feedback scheme to minimize the outage probability for a wireless cooperative decode-and-forward network. Specifically, based on the instantaneous conditions of the source-destination and relay-destination channels, the destination will allocate the transmission time of the source and relay and feed back the allocation results to the source. Both full, or infinite-rate, feedback and limited feedback are considered. To simplify the expression of the outage probability in the full feedback case, a lower bound is proposed, based on which we find the sub-optimal location of the relay that can result in a close-to-optimal outage performance. Our results show that, even with only one-bit feedback, a significant improvement in terms of the outage probability can be achieved compared to the no feedback case. Furthermore, the outage performance can approach optimality by exploiting only two or three bits feedback from the destination. © 2008 IEEE.