Iterative algorithms are an attractive approach to approximating optimal, but high-complexity, joint channel estimation and decoding receivers for communication systems. We present a unified approach based on factor graphs for deriving iterative message-passing receiver algorithms for channel estimation and decoding. For many common channels, it is easy to find simple graphical models that lead directly to implementable algorithms. Canonical distributions provide a new, general framework for handling continuous variables. Example receiver designs for Rayleigh fading channels with block or Markov memory, and multipath fading channels with fixed unknown coefficients illustrate the effectiveness of our approach.

Energy-efficient wireless communication network design is an important and challenging problem. Its difficulty lies in the fact that the overall performance depends, in a coupled way, on the following subsystems: antenna, power amplifier, modulation, error control coding, and network protocols. In addition, given an energy constraint, improved operation of one of the aforementioned subsystems may not yield better overall performance. Thus, to optimize performance one must account for the coupling among the above subsystems and simultaneously optimize their operation under an energy constraint. In this article we present a generic integrated design methodology that is suitable for many kinds of mobile systems and achieves global optimization under an energy constraint. By pointing out some important connections among different layers in the design procedure, we explain why our integrated design methodology is better than traditional design methodologies. We present numerical results of the application of our design methodology to a situational awareness scenario in a mobile wireless network with different mobility models. These results illustrate the improvement in performance that our integrated design methodology achieves over traditional design methodologies, and the tradeoff between energy consumption and performance.

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Recent technological advances coupled with the collaboration between government and industry will soon make it possible to include IP routers and IP modems on board a commercial geostationary communications satellite. The Internet Protocol Routing in Space (IRIS) Joint Capability Technology Demonstration (JCTD) will introduce a new network capability that is aimed at enhancing military network-centric operations through information access, collaboration and dissemination.This paper describes the IRIS vision and strategy, and the specific goals ofthe JCTD. It describes the network architecture and technology development aspects for deploying a combined router and modem function as part of a hosted payload within a commercial transponded satellite.1-4244-151