Distinguished Lecturers

Prof. Kin K. Leung

Electrical and Electronic Engineering, and Computing Departments at Imperial College

Title: Cross-Layer Designs for Wireless Mesh Networks

Abstract: This speech will be primarily based on recent results obtained by the EU FP6 MEMBRANE project, which investigates new multiple antennas and cross-layer networking techniques for wireless mesh networks to support backhauling applications. Specifically, a new opportunistic scheduling algorithm is proposed to realize the multi-user diversity gain while attempting to satisfy the bandwidth requirement committed for various traffic connections by the routing protocol. An integrated algorithm for routing and scheduling with steerable antenna beams is developed to meet quality of service (QoS) requirements. Last but not least, a new connection control algorithm based on real-time performance statistics is proposed. The cross-layer design of admission control, routing and scheduling is showed to achieve the best network performance while meeting the required QoS.

Prof. Martin Haardt

Technical University of Ilmenau

Bio

Title: Tensor-Based Channel Estimation (TENCE) for Two-Way Relaying with Multiple Antennas and Scalable Complexity to Facilitate Cross-Layer Techniques

Abstract: Relaying is an essential feature of future wireless communication systems to satisfy the ubiquitous demand of high data rates. Two-way relaying systems utilize the radio resources in a particularly efficient fashion. Here, two terminals exchange data with the help of an intermediate relay station. In order to enable the mass deployment of these relays, we focus on very simple amplify-and-forward (AF) relays. Hence, to separate the data streams in two-way relaying, both user terminals need reliable knowledge of all relevant channel parameters.

In this contribution, we develop a tensor-based channel estimation algorithm (TENCE) for two-way relaying that provides both terminals with full knowledge of all channel parameters involved in the transmission, i.e., the channel matrices between both terminals and the relay. The solution is algebraic and is therefore very fast. Moreover, TENCE is applicable to arbitrary antenna configurations at the user terminals and the relay. We also derive criteria for the design of the pilot symbols and the corresponding relay amplification matrices during the training phase. Then we show that the solution obtained by TENCE can be improved by an iterative refinement, which is based on the Structured Least Squares (SLS) technique. Between one and four iterations are sufficient. Consequently, the increase in computational complexity is moderate.

Based on the estimated channel matrices, the optimum transceiver strategies (including the choice of the relay amplification matrices) for the data transmission phase can be obtained via cross-layer considerations.

Prof. Hamid Aghvami

Centre for Telecommunications Research- King's College London

Bio

Title: Cross-Layer Design and Interactions: The Challenges

Abstract: It is now widely accepted that cross-layer optimization offers the potential to achieve vast performance and efficiency gains in wireless communications environments. For example, cross-layer interactions could improve the performance of transport layer protocols, thereby enhancing throughput at the transport/application layer (this is important, as upper-layer performance is what the user actually experiences); as another example, cross-layer optimization between higher and lower layers offers considerable potential for communications to be made more “green”, implying a significant reduction in energy consumptions of networks and devices.

The vision of all-IP wireless networks has been largely achieved. The question that now naturally arises is: What’s comes next? In our view, an architecture that facilitates cross-layer design is the next step forward in all-IP based wireless networking. In this talk, an overview is given on the potential for cross-layer information exchange, involving higher layers interacting with other layers of the protocol stack, to assist communication efficiency and performance, whereby the emphasis is on the transport and network layers. In addition, advanced network-layer functionalities that can be used to facilitate the efficient transfer of cross-layer parameters among network elements are discussed.

Finally covered are cross-layer designs for green communications. The emphasis here is on how new networking paradigms, such as Delay Tolerant Networking, can be utilized to reduce energy consumption for delay-insensitive traffic. This approach will still, nevertheless, allow for considerable capacity gains in the network.

IWCLD2009

Distinguished Lecturers