ITR: Cooperative Communication Schemes for Wireless Networks

University Of Florida, Gainesville FL

Investigators

Abstract

In a wireless network, multiple communications devices in close proximity form a natural distributed antenna array. If a group of such devices transmit and receive in some cooperative manner, then the system performance can be significantly improved. This researchexplores techniques for cooperative transmission and reception using multiple devices. This cooperative communication approach is differentfrom traditional array processing because the distributed nature of the communication nodes calls for network-oriented design approaches and processing algorithms. In particular, techniques that allow distributed and asynchronous processing that utilizes information provided by other nodes in a cluster will be considered. For cooperative transmission, distributed space-time coding will be employed to take advantage of transmit diversity provided by the distributed array. One crucial issue for distributed space-time coding is that only rough synchronization between the nodes can be achieved. Hence space-time coding in an asynchronous setting needs to be considered. This leads to research on asynchronous diversity and coding gain analysis, symbol waveform design, and tradeoff between the complexity of transmitter synchronization and complexity of the decoding process. For cooperative reception, distributed iterative decoding will be employed to obtain diversity advantage in reception. In this approach, multiple nodes form a distributed antenna array by collaboratively processing a received signal. By exchanging information in a distributed decoding process, the nodes are able to extract diversity from the channel and decode the message. The main obstacle to this approach is that there is a vast amount of information that can be shared between the nodes. This problem can be solved by using iterative decoding to extract important information from the received signal at each node, and only this information is passed to other nodes. Each node will then utilize the information from other nodes to perform further decoding to obtain the diversity advantage provided by the additional information. The objective is to develop distributed processing techniques that allow us to obtain the maximum degree of diversity advantage from the signals received at multiple receiving nodes, while requiring a minimum amount of information exchange between the nodes. In order to make the above cooperative communication schemes work, a control signaling strategy has to be designed to allow sharing of information between nodes. More importantly, the physical-layer communication performance of the proposed system will be dependent on the control signaling strategy. Therefore this signaling design problem will be attacked by a cross-layer design approach. Analytical guidelines for designing systems employing the proposed cooperative communication schemes will be developed. The expected results of this research can be utilized in many different commercial and military communication networks, such as cellular and sensor networks.