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Towards Cooperative Routing in Underwater and Body Area Wireless Sensor Networks
Abstract and Figures
Wireless Sensor Networks (WSNs), particularly Wireless Body Area Networks (WBANs) and Underwater Wireless Sensor Networks (UWSNs) are important building blocks of upcoming generation networks. Sensor networks consist of less expensive nodes having the features of wireless connectivity, very less transmission power, limited battery capacity and resource constraints. Due to low cost and small size, sensor nodes allow very big networks to be installed at a viable price and develop a link between information systems and the real globe. Cooperative routing exploits the transmission behavior of wireless medium and communicates cooperatively by means of neighboring nodes acting as relays. Prospective relays as well as the destination nodes are chosen from a set of near-by sensors that use distance and Signal-to-Noise Ratio (SNR) of the link conditions as cost functions
– this contributes to significant reduction in path-loss and enhanced reliability. In this dissertation, we propose three schemes Link Aware and Energy Efficient protocol for wireless Body Area networks (LAEEBA), Incremental relay-based Cooperative Critical data transmission in Emergency for Static wireless BANs (InCo-CEStat) and Cooperative Link Aware and Energy Efficient protocol for wireless Body Area networks (Co-LAEEBA). These protocols are efficient in terms of link-losses, reliability and throughput. Consideration of residual energy balances load among sensors, and separation and SNR considerations entrust reliable data delivery. As a promising technique to mitigate the effect of fading, cooperative routing is introduced in the functionality of LAEEBA and Co-LAEEBA protocols. Similarly, incremental relaying in InCo-CEStat account for reliability. Simulation results show that our newly proposed schemes maximize the network stability period and network life-time in comparison to other existing schemes for WBANs. In Underwater Acoustic Sensor Networks, demand of time-critical applications leads to the requirement of delay-sensitive protocols. In this regard, this disserta- tion presents five routing protocols for UWSNs; Cooperative routing protocol for Underwater Wireless Sensor Networks (Co-UWSN), Cooperative Energy-Efficient model for Underwater Wireless Sensor Networks (Co-EEUWSN), Analytical ap- proach towards Reliability with Cooperation for Underwater sensor Networks (AR- CUN), Reliability and Adaptive Cooperation for Efficient UWSNs (RACE) and Stochastic Performance Analysis with Reliability and COoperation for UWSNs (SPARCO). In these protocols, physical layer’s cooperative routing is explored for the design of network layer routing schemes that prove to be energy-efficient as well as path-loss aware. The concentration is focused on Amplify-and-Forward (AF) scheme at the relay nodes and Fixed Ratio Combining (FRC) technique at the destination nodes. Nodes cooperatively forward their transmissions taking benefit of spatial diversity to reduce energy consumption. Simulations are conducted to validate the performance of our proposed schemes in comparison to the selected existing ones. Results demonstrate the validity of our propositions in terms of selected performance metrics.
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Underwater wireless sensor network (UWSN) features many unique characteristics, including slow propagation speed, high end-to-end delay, low available bandwidth, variable link quality, and energy constraint. All these problems pose a big challenge to devise a transmission efficient, energy-saving, and low delay routing protocol for UWSNs. In this paper we devise a relative distance based forwarding (RDBF) routing protocol, which aims to provide transmission efficient, energy-saving, and low delay routing. We utilize a fitness factor to measure and judge the degree of appropriateness for a node to forward the packets. Under the limitations of the fitness factor, RDBF can confine the scope of the candidate forwarders and find the beneficial relays to forward packets. In this way, only a small fraction of nodes are involved in forwarding process, which can distinctly reduce the energy consumption. Moreover, using only the selected beneficial nodes as forwarders can both enhance the transmission efficiency and reduce the end-to-end delay. This is because the distances of these nodes to the sink are the shortest and the hop counts of routing paths consisted by these nodes are minimum. We use the ns-2 based simulator to conduct our experiment; the results show that RDBF performs better in terms of packet delivery ratio, end-to-end delay, and energy efficiency.
The underwater acoustic channel is characterized by a path loss that depends not only on the transmission distance, but also on the signal frequency. As a consequence, transmission bandwidth depends on the transmission distance, a feature that distinguishes an underwater acoustic system from a terrestrial radio system. The exact relationship between power, transmission band, distance and capacity for the Gaussian noise scenario is a complicated one. This work provides a closed-form approximate model for 1) power consumption, 2) band-edge frequency and 3) bandwidth as functions of distance and capacity required for a data link. This approximate model is obtained by numerical evaluation of analytical results which takes into account physical models of acoustic propagation loss and ambient noise. The closed-form approximations may become useful tools in the design and analysis of underwater acoustic networks.
Cooperative spectrum sensing (CSS) is a very important technique in cognitive wireless sensor networks, but the channel and multipath affect the sensing performance. For improving the sensing performance, this paper incorporates a modified double-threshold energy detection (MDTED) and the location and channel information to improve the clustering cooperative spectrum sensing (CCSS) algorithm. Within each cluster, the cognitive node with the best channel quality to the fusion center (FC) is chosen as the cluster head (CH), and each node uses the MDTED. The detective information is sent to CH, and CH makes the decision of the cluster. The decision information is sent to FC by each CH, and FC uses the “or” rule to fuse all clusters’ decision information and makes a final decision. Since MDTED needs to transfer large traffic and occupy channel widely, this paper further optimizes the improved algorithm. Ensuring the detection performance, the cognitive nodes participating in the sensing are properly reduced. Simulation results show that the detecting accuracy of the improved algorithm is higher than conventional CSS, and the improved algorithm can also significantly improve collaborative sensing ability. For the optimization of cognitive nodes’ number, the detection probability of the network can be obviously increased.
In recent years, considerable attention has been devoted to design and standardization of wireless system operating in the 60 GHz band. Further in the context of WLAN (Wireless Local Area Network) and WPAN (Wireless Personal Area Network) systems for High Data Rate (HDR) wireless communications, the unlicensed frequency band available in the millimeter wave region has become more and more attractive. However at 60 GHz the shadowing phenomenon is the main cause of strong signal impairments even for shorter distances of few meters. Cooperative communication networks have received significant interests from both academia and industry in the past decade due to its ability to provide spatial diversity without the need of implementing multiple transmit and/or receive antennas at the end-user terminals. These new communication networks have inspired novel ideas and approaches to find out what and how performance improvement can be provided with cooperative communications. Thus cooperative diversity forms an attractive method to mitigate such shadowing effects by use of dedicated active or passive relay stations. The objective of this paper is to implement and analyze a low complexity amplify-and-forward (AAF) cooperative transmission technique. With the AAF method, the paper examines a single relay network in which the channels considered are based on TSV model at 60 GHz. Performances based on different combining methods such as ERC, FRC, ESNRC and SNRC are evaluated. The results indicate satisfactory diversity benefits offered by AAF cooperative diversity protocol as compared to single link transmission. The FRC combining provides attractive benefits but requires channel quality information whereas ERC comparatively, provides better benefits, but requires no channel information. Also, positioning of the relay near to source and / or destination gives slight performance benefits.
In this paper a new method to improve performance of cooperative underwater acoustic (UWA) sensor networks will be introduced. The method is based on controlling and optimizing carrier frequencies which are used in data links between network nods. In UWA channels Pathloss and noise power spectrum density (psd) are related to carrier frequency. Therefore, unlike radio communications, in UWA Communications signal to noise ratio (SNR) is related to frequency besides propagation link length. In such channels an optimum frequency in whole frequency band and link lengths cannot be found. In Cooperative transmission, transmitter sends one copy of transmitted data packets to relay node. Then relay depending on cooperation scheme, amplifies or decodes each data packet and retransmit it to destination. Receiver uses and combines both received signals to estimate transmitted data. This paper wants to propose a new method to decrease network power consumptions by controlling and sub-optimizing transmission frequency based on link length. For this purpose, underwater channel parameters is simulated and analyzed in 1km to 10km lengths (midrange channel). Then link lengths sub categorized and in each category, optimum frequency is computed. With these sub optimum frequencies, sensors and base station can adaptively control their carrier frequencies based on link length and decrease network’s power consumptions. Finally Different Cooperative transmission schemes “Decode and Forward (DF)” and “Amplify and Forward (AF)”, are simulated in UWA wireless Sensor network with and without the new method. In receiver maximum ratio combiner (MRC) is used to combining received signals and making data estimations. Simulations show that the new method, called AFC cooperative UWA communication, can improve performance of underwater acoustic wireless sensor networks up to 40.14%.
Aquatic debris monitoring is of great importance to human health, aquatic habitats and water transport. In this paper, we first introduce the prototype of an aquatic sensor node equipped with an embedded camera sensor. Based on this sensing platform, we propose a fast and accurate debris detection algorithm. Our method is specifically designed based on compressive sensing theory to give full consideration to the unique challenges in aquatic environments, such as waves, swaying reflections, and tight energy budget. To upload debris images, we use an efficient sparse recovery algorithm in which only a few linear measurements need to be transmitted for image reconstruction. Besides, we implement the host software and test the debris detection algorithm on realistically deployed aquatic sensor nodes. The experimental results demonstrate that our approach is reliable and feasible for debris detection using camera sensors in aquatic environments.
There are many applications for using wireless sensor networks (WSN) in ocean science; however, identifying the exact location of a sensor by itself (localization) is still a challenging problem, where global positioning system (GPS) devices are not applicable underwater. Precise distance measurement between two sensors is a tool of localization and received signal strength (RSS), reflecting transmission loss (TL) phenomena, is widely used in terrestrial WSNs for that matter. Underwater acoustic sensor networks have not been used (UASN), due to the complexity of the TL function. In this paper, we addressed these problems by expressing underwater TL via the Lambert W function, for accurate distance inversion by the Halley method, and compared this to Newton-Raphson inversion. Mathematical proof, MATLAB simulation, and real device implementation demonstrate the accuracy and efficiency of the proposed equation in distance calculation, with fewer iterations, computation stability for short and long distances, and remarkably short processing time. Then, the sensitivities of Lambert W function and Newton-Raphson inversion to alteration in TL were examined. The simulation results showed that Lambert W function is more stable to errors than Newton-Raphson inversion. Finally, with a likelihood method, it was shown that RSS is a practical tool for distance measurement in UASN.
Recent years have witnessed successful real-world deployments of wireless sensor networks (WSNs) in a wide range of civil and military applications. Sensing coverage and network connectivity are two of the most fundamental issues to ensure effective environmental sensing and robust data communication in a WSN application. This chapter presents fundamental studies on the sensing coverage and the network connectivity from mathematical modeling, theoretical analysis, and performance evaluation perspectives. Both lattice WSNs that follow a pattern-based deployment strategy and random WSNs that follow a random deployment strategy are considered. The aim of this chapter is to deliver a systematic study on the fundamental problems in WSNs and provide guidelines in selecting critical network parameters for WSN design and implementation in practice.
In this paper, we derive the closed form expressions for symbol error rate (SER) of a multiple relay cooperative communication system using selective decode-and-forward protocol over generalized κ-μ and η-μ independent identically distributed fading channels for different modulation schemes. We also derive the exact expression of SER for non-coherent detection and an approximate expression of SER for coherent detection. At the destination, we employ the maximal ratio combining to provide diversity. The final expressions of SER are represented in terms of moment generating function which is a combination of elementary functions. We also perform the Monte Carlo simulations by assuming different channels and by varying the number of relays to validate the analytical results.
We develop a general approach to cross correlation in antenna systems suitable for applications to spatial diversity and MIMO systems. The far-field correlation is expressed in terms of the currents on the antennas. The basic strategy proposed here is to perform the overall evaluation of cross correlation by means of superposition integrals involving contributions emerging from all possible mutual correlations between the point sources on the antenna currents where interactions are mediated by a new cross-correlation Green's function. The method is verified and demonstrated in several numerical examples and a design methodology aiming at maximizing the diversity gain is outlined and illustrated. It is also shown that arbitrary antenna arrays can be reduced to suitable models involving only infinitesimal dipoles, in effect enabling us to compute the total diversity gain using the cross-correlation Green's function. The formulation provided here gives the electromagnetic aspect of spatial diversity an articulated form proper for design and development of practical communication links using multiple antenna systems.