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With the emergence of large mobile ad hoc networks, the ability of existing routing protocols to scale well and function satisfactorily comes into question. Clustering has been proposed as a means to divide large networks into groups of suitably smaller sizes such that prevailing MANET routing protocols can be applied. However, the benefits of clustering come at a cost. Clusters take time to form and the clustering algorithms also introduce additional control messages that contend with data traffic for the wireless bandwidth. In this paper, we aim to analyse a distributed multi-hop clustering algorithm, Mobility-based D-Hop (MobDHop), based on two key clustering performance metrics and compare it with other popular clustering algorithms used in MANETs. We show that the overhead incurred by multi-hop clustering has a similar asymptotic bound as 1-hop clustering while being able to reap the benefits of multi-hop clusters. Simulation results are presented to verify our analysis.

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ASTRALS is a project funded by the FP6 IST available on their practical performance enhancement under program which focuses on the in-home delivery, adaptation and realistic propagation conditions. processing of multiple audio/visual streams. One aspect of this The MIMO scheme proposed in this paper aims at project focuses on the wireless transmission of these streams improving the system capacity especially in Line-of-Sight using the IEEE 802.16 standard. A premium Quality of Service (LoS) while maintaining an equivalent performance to and IP based transmission scheme is employed in this project standard systems in non-LoS conditions. To achieve this, including MIMO and mesh extensions for increased throughput specifically designed antenna arrays are employed using a and robustness. The MIMO architecture is based on a novel novel array design method that orthogonalises the MIMO technique which maximises the performance over both Line-ofSight and non-Line-of-Sight conditions. On the other hand, mesh channel response [2], [3]. A number of simulation results networking is responsible for multi-hopping transmission when a validating the superiority of this architecture are presented in direct link is not available. This paper contains a number of this paper. simulation results which imply the possibility towards fully Another technique which achieves link budget and deterministic wireless audio/visual transmission in the home throughput improvements without sacrificing the wireless environment.robustness is also presented in this paper. This corresponds to the IEEE 802.16-2004 mesh-mode which takes advantage of