iCORE Guest Seminars in Communications

Performance metrics are calculated using the derived PDF and CDF expressions. Simulation results are used to verify the obtained solutions. The exact results permit accurate comparisons of the performance of dual-hop AF relaying systems without relay selection, opportunistic dual-hop AF relaying systems with relay selection, and dual-hop AF relaying systems with full selection. It is found that dual-hop AF relaying systems with relay selection outperform dual-hop AF systems without relay selection, and that they provide a diversity gain, proportional to the number of relays, over conventional dual-hop AF relaying systems. It is shown also that full selection dual-hop AF systems outperform both of the other two systems and that they provide a higher diversity gain.

*Research Funded by TELUS/NSERC CRD Grant.

*Research Funded by TELUS/NSERC CRD Grant.

We present the design of an experiment particularly suited for evaluating cooperative techniques using a common set of measurements. This enables (i) derivation of ranging models, (ii) characterization of localization algorithms, (iii) quantification of cooperation benefit, (iv) development of techniques for harnessing environmental knowledge such as non-line-of-sight detection. As a case study, we consider ultrawide bandwidth cooperative location-aware networks in cluttered environments and evaluate their performance using experimental data.

Dr. Scholtz will describe his exploration of ultra-wideband (UWB) radio over the past two decades, and present his view of measuring and modeling UWB radio propagation channels. As time permits, he will explain the connections of his experimental work in the UltRa Lab and elsewhere to UWB system topics, such as Rake receiver design, UWB signal design, rapid sync acquisition, ranging, time transfer between network nodes, hyperbolic navigation, channel identification for secure communications, etc.

Various research projects were carried out at Laval University over the last few years focusing on both advanced wireless transceiver architectures and self-organization in wireless networks. The former topic was concerned with the development of novel signal processing techniques, exploiting the latest in communication theory and having fundamental advantages, while keeping a focus throughout on associated implementation issues, such as algorithmic complexity, power consumption, etc. This research approach, bridging theory and implementation under a pragmatic mindset, yielded rather promising results. For example, it is known that MIMO techniques are the key to augmenting effective link throughput without bandwidth expansion. However, it is still problematic in practice to incorporate multiple antennas on handsets because of cost / power / size constraints. As a solution, virtual MIMO techniques based on sphere decoding were developed which can effectively at the receiver separate more co-channel signals than there are receive antennas.

With regards to the second topic, given the increasing pervasiveness of wireless networks of all sorts, including ad hoc networks competing within narrow unlicensed bands and wireless sensor networks, self-organization could constitute the next defining paradigm in wireless communications. It can be shown that a set of heuristic principles can be leveraged to engineer a self-organized connection- oriented wireless network with minimal complexity. Such a system requires no centralization of information, yet achieves a nearly optimal global state with only a modest amount of local signaling. It will naturally and jointly balance the many parameters related to radio resource management, exhibiting great adaptability, fault tolerance and scalability.

A salient feature of wireless networks is the close interaction between the physical layer and other networking layers. This phenomenon is a result of the principal distinguishing features of wireless, namely mobility and the importance of physical properties (diffusion, interference, fading and radio geometry) in determining link characteristics. For example, the applications layer interacts considerably with the physical layer, as is well known through the importance of quality-of-service in wireless network design. This talk will explore four other issues in which the applications layer influences, or interacts with, the physical layer. In particular, the four applications of file transfer, real-time multimedia transmission, inference and social networking, will be used to motivate consideration of four respective research problems involving the physical layer: physical layer security in data networks, finite-blocklength capacity in multimedia networks, distributed inference in sensor networks, and connectivity in small-world networks. Recent progress in each of these three research areas will be reviewed.