Collaborative Localization Algorithms for Wireless Sensor Networks with Reduced Localization Error

Localization is an important research issue in Wireless Sensor Networks (WSNs). Though Global Positioning System (GPS) can be used to locate the position of the sensors, unfortunately it is limited to outdoor applications and is costly and power consuming. In order to find location of sensor nodes without help of GPS, collaboration among nodes is highly essential so that localization can be accomplished efficiently. In this paper, novel localization algorithms are proposed to find out possible location information of the normal nodes in a collaborative manner for an outdoor environment with help of few beacons and anchor nodes. In our localization scheme, at most three beacon nodes should be collaborated to find out the accurate location information of any normal node. Besides, analytical methods are designed to calculate and reduce the localization error using probability distribution function. Performance evaluation of our algorithm shows that there is a tradeoff between deployed number of beacon nodes and localization error, and average localization time of the network can be increased with increase in the number of normal nodes deployed over a region

Approximate K-Coverage Configuration in WirelessSensor Networks

The K-coverage configuration is widely exploited to guarantee the surveillance quality of applications on wireless sensor networks. To prolong the system lifetime, a sensor node is determined to sleep if its sensing range is already K-covered. Many K-coverage configuration algorithms in literature cannot satisfy the requirements of high quality and low cost simultaneously. In this paper, we propose an efficient K-coverage eligibility algorithm, which determines the eligibility of each sensor node at very low cost. The distinct feature of the ACE algorithm is to discover the regions with lower coverage degree of each sensor node. Experimental results show that the accuracy of the ACE algorithm is guaranteed to be higher than 90%, while its computational cost is only 11% of a well-known deterministic algorithm. The ACE algorithm is suitable to be used for a long-term monitoring task on wireless sensor networks

Fabrikasi dan Pencirian Pencerai 3×3 Berasaskan Gentian Optik Polimer (POF) dengan Teknik Pelakuran Berkos Rendah

Gentian optik polimer (POF) mempunyai banyak kelebihan dan banyak digunakan untuk komunikasi terutamanya dalam industri automotif. Komunikasi ini memerlukan maklumat yang banyak dihantar pada satu masa dengan kos yang rendah. Untuk itu pencerai 3×3 POF yang berkonsepkan pemultipleks bahagi jarak gelombang (WDM) yang berkos rendah dan berteknologi hijau difabrikasikan. Pencerai POF ini difabrikasikan dengan menggunakan alat yang murah dan mudah didapati, iaitu tiub besi dan lilin. Teknik fabrikasi yang digunakan adalah dengan memanaskan tiga lembar POF sehingga bahagian tengahnya mencair dan melakur sehingga mengecil dan memanjang berdiameter 1 mm. Pencerai 3x3 POF yang berjaya difabrikasi dicirikan dengan mengukur kehilangan POF sebelum dan selepas hujungnya diratakan dan digilap dengan dua jenis kertas pasir yang berlainan darjah kekasaran. Ini untuk melihat kesan gilapan pada kehilangan isyarat optik. Kehilangan pencerai POF juga diukur pada suhu yang berbeza bagi melihat kesannya pada prestasi pencerai POF. Berdasarkan keputusan yang diperoleh, dapat dilihat bahawa kebersihan dan kerataan hujung POF memberi kesan kepada kehilangan dengan penurunan antara 0.3 hingga 5.0 dB. Suhu juga memberi kesan kepada kehilangan isyarat POF, walaupun tidak begitu ketara, dengan purata peningkatan kehilangan sebanyak 0.3 dB. Walaupun secara keseluruhannya nilai kehilangan dalam pencerai POF yang difabrikasi ini masih tinggi, prestasi ini dapat diperbaiki dengan penambahbaikan pada teknik pelakuran dan penggunaan alat yang lebih berkualiti. Teknik pemfabrikasi berkos rendah ini dipercayai boleh menghasilkan pencerai POF yang murah secara komersil, tetapi dengan kajian yang lebih mendalam pada teknik pelakuran, punca kehilangan dan cara meminimumkan kehilangan boleh diperoleh dan meningkatkan isyarat optik keluaran

Memory And Network Architecture Interaction In An Optically Interconnected Distributed Shared Memory System

This paper develops a performance model of an optically interconnected parallel computer system operating in a distributed shared memory environment. The performance model is developed to reflect the impact of low level optical media access protocol and optical device switching latency on high level system performance. This enables the model to predict the performance impact in supporting distributed shared memory with different address allocation schemes and media access protocols. The passive star-coupled photonic network operates through wavelength division multiple access. Two media access protocols are examined for this WDM network, both are designed to operate in a multiple-channel multiple-access environment and require each node to possess a wavelength tunable transmitter and a fixed (or slow tunable) receiver. A semi-Markov model has been developed to study the interaction of the distributed shared memory architecture and the two access protocols of the photonic network. This ..