Design and performance evaluation of a banyan network basedinterconnection structure for ATM switches

This paper presents a new self-routing packet network called the plane interconnected parallel network (PIPN). In the proposed design, the traffic arriving at the network is shaped and routed through two banyan network based interconnected planes. The interconnections between the planes distribute the incoming load more homogeneously over the network. The throughput of the network under uniform and heterogeneous traffic requirements is studied analytically and by simulation. The results are compared with the results of the baseline network and another banyan network based parallel interconnection network. It is shown that, for the proposed design, a higher degree of heterogeneity results in better performance     

A dynamic and weighted spectrum decision mechanism based on SNR Tracking in CRAHNs

The spectrum decision concept in Cognitive Radio Ad-Hoc Networks (CRAHNs) introduces important challenges. These include the time-dependent SNR observations of individual CRAHN users due to the fading and shadowing effects in the licensed channels, the necessity of fusion mechanisms for accurate decisions, and the difficulties depending on multi-hop deployment. Considering these challenges, in this paper, we propose a dynamic, cooperative and distributed spectrum decision mechanism in order to decide the channel usage in CRAHNs accurately. The proposed mechanism introduces the SNR Tracking System which considers the time-varying local SNR observations and decisions of the CRAHN users. The proposed mechanism employs a distributed Weighted Fusion Scheme (WFS), to combine the individual decisions and hence, to obtain the cooperative decision. The proposed spectrum decision mechanism adapts itself dynamically to the multi-hop architecture of the network. The performance of the proposed mechanism is compared to some conventional fusion mechanisms based on the AND, OR and MAJORITY rules, and it is shown that the proposed weighted mechanism gives lower false alarm and higher detection probabilities compared to the conventional fusion mechanisms.     

Performance evaluation of distributed localization techniques for mobile underwater acoustic sensor networks

Underwater sensor networks (USN) are used for tough oceanographic missions where human operation is dangerous or impossible. In the common mobile USN architecture, sensor nodes freely float several meters below the surface and move with the force of currents. One of the significant challenges of the mobile USN is localization. In this paper, we compare the performance of three localization techniques; Dive and Rise Localization (DNRL), Proxy Localization (PL) and Large-Scale Localization (LSL). DNRL, PL and LSL are distributed, range-based localization schemes and they are suitable for large-scale, three dimensional, mobile USNs. Our simulations show that, DNRL and LSL can localize more than 90% of the underwater nodes with high accuracy while LSL has higher energy consumption and higher overhead than DNRL. The localization success and accuracy of PL is lower than the other techniques however it can localize underwater nodes faster when small number of beacons are employed.     

Loss rate-based burst assembly to resolve contention in optical burst switching networks

Two loss rate-based optical burst assembly techniques addressing contention resolution are studied. These techniques stem from the burst assembly schemes using adaptive thresholds, which have been introduced earlier by the authors. The loss rates on the links/paths leading to the destination nodes are used to estimate congestion levels. Three alternative time and size threshold value pairs are employed based on the congestion level observed. Here, the aim is to generate short bursts under heavy traffic and long bursts under light traffic conditions in order to enhance performance. The results that are obtained in terms of byte loss rate and delay are compared with those of the hybrid burst assembly. It is observed that the adaptive techniques significantly enhance the byte loss rate as traffic gets heavier while keeping end-to-end delay in a feasible range.