Design, Implementation and Characterization of a Cooperative Communications System

Cooperative communications is a class of techniques which seek to improve reliability and throughput in wireless systems by pooling the resources of distributed nodes. While cooperation can occur at different network layers and time scales, physical layer cooperation at symbol time scales offers the largest benefit. However, symbol level cooperation poses significant implementation challenges, especially in the context of a network of distributed nodes. We first present the design and implementation of a complete cooperative physical layer transceiver, built from scratch on the Wireless Open-Access Research Platform (WARP). In our implementation fully distributed nodes employ physical layer cooperation at symbol time scales without requiring a central synchronization source. Our design supports per-packet selection of non-cooperative or cooperative communication, with cooperative links utilizing either amplify-and-forward or decode-and-forward relaying. A single design implements transmission, reception and relaying, allowing each node to assume the role of source, destination or relay per packet. We also present experimental methodologies for evaluating our design and extensive experimental results of our transceiver's performance under a variety of topologies and propagation conditions. Our methods are designed to test both overall performance and to isolate and understand the underlying causes of performance limitations. Our results clearly demonstrate significant performance gains (more than 50× improvement in PER in some topologies) provided by physical layer cooperation even when subject to the constraints of a real-time implementation. As with all our work on WARP, our transceiver design and experimental framework are available via the open-source WARP repository for use by other wireless researchers

On the Experimental Evaluation of Vehicular Networks: Issues, Requirements and Methodology Applied to a Real Use Case

One of the most challenging fields in vehicular communications has been the experimental assessment of protocols and novel technologies. Researchers usually tend to simulate vehicular scenarios and/or partially validate new contributions in the area by using constrained testbeds and carrying out minor tests. In this line, the present work reviews the issues that pioneers in the area of vehicular communications and, in general, in telematics, have to deal with if they want to perform a good evaluation campaign by real testing. The key needs for a good experimental evaluation is the use of proper software tools for gathering testing data, post-processing and generating relevant figures of merit and, finally, properly showing the most important results. For this reason, a key contribution of this paper is the presentation of an evaluation environment called AnaVANET, which covers the previous needs. By using this tool and presenting a reference case of study, a generic testing methodology is described and applied. This way, the usage of the IPv6 protocol over a vehicle-to-vehicle routing protocol, and supporting IETF-based network mobility, is tested at the same time the main features of the AnaVANET system are presented. This work contributes in laying the foundations for a proper experimental evaluation of vehicular networks and will be useful for many researchers in the area.Comment: in EAI Endorsed Transactions on Industrial Networks and Intelligent Systems, 201