No abstract

No abstract

Collaborative signal processing is one of the most promising applications that are currently being investigated for sensor networks. In this paper, we use FFT computation as a vehicle to highlight the issues involved in realizing distributed computations over sensor networks that have global and local communication and synchronization characteristics. We present a power efficient algorithm for computing 1-D Fast Fourier Transform (FFT) over single and multi-hop wireless sensor networks. The proposed algorithm reduces the number of transmissions, eliminates typical redundant computations in a distributed FFT algorithm and uniformly maps complex multiplications over all the sensors nodes by introducing an extra bit-complement permutation stage after first (log 2 N)/2 iterations. We show that the proposed algorithm improves energy consumption by 36% on the average on multi-hop sensor networks. This saving in energy consumption significantly improves the battery life of the sensor nodes thereby increasing lifetime of the sensor network.

No abstract

Data collection techniques in Wireless Sensor Net-to address aforementioned constraints by employing relatively works (WSN) suffer from heavy congestion particularly at nodes simple MAC protocol and routing layer methods to mitigate closer to the sink node. In order to combat this problem, either MAC protocols shortcomings. We present a novel data colcomplex MAC layer protocols have been proposed or non scalable data collection solutions have been designed. We propose a novel en scheme is betweensr cross layer optimization approach that assumes a very simple and MAC layers. The proposed scheme is suitable for sensor MAC protocol and makes use of both routing and MAC layers networks that use collision based MAC protocols. Examples information to reduce congestion, improve delivery ratio, and include SMAC [18], TMAC [15], and BMAC [12]. These optimize energy usage. The proposed approach uses multiple protocols are popular due to ease of implementation and loose disjoint collection trees, rooted from sink, with non overlapping duty cycles. At the MAC layer, we exploit the fact that nodes that synchronizatlon requirements. In such protocols sensors follow are on different data collection trees need not to communicate periodic sleep cycles, and sleep period is much longer than with each other, hence the SMAC based wake up and sleep the active period. One of the biggest disadvantages of these schedule for each tree is different. Existing multiple tree based protocols is that the wireless channel is not utilized during data collection protocols have been designed primarily for fault the sleep periods. The proposed scheme utilizes the sleeping tolerance or load balancing. For MAC layer part of our protocol, we have modified the SMAC code available in ns-2.28 to simulate periods by constructing multple data collecton trees and our data collection scheme. Our scheme improves the data making different trees wake up at different times. Therefore, delivery ratio up to 40% for regular traffic, and reduces energy unlike scheduling based protocols where each node is assigned consumption by 30%. a unique schedule in a frame, each tree is assigned a unique schedule with in a frame.The idea of using multiple trees in data collection applica-I. INTRODUCTION tions has been proposed in earlier works [3], [2], [14], [11], In data collection applications several communication fac-[8], [9]. In these works, multiple trees have been generally tors, such as limited energy, packet collisions and congestion, used to make the network more robust against node failures reduce the data bandwidth available to sensors. These factors by providing more than one path from nodes to the sink or have been broadly addressed at the MAC layer by introducing base station. Moreover multiple trees have also been used to duty cycles in collision-based protocols (e.g., SMAC [18], decrease the workload on single tree by distributing traffic BMAC [12], etc.), or designing scheduling based protocols load. Our work differs from the previous research in the use of ...