Estimation Using Cross-correlation in a Communications Network

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Copyright: Anower, Md. Shamim
In a large-scale wireless sensor network, it is often desirable to count the number of nodes in the network, or the number of nodes that are within communications range of a particular node. In such networks, nodes are deployed for a wide variety of military and civilian applications. These applications require a balance among the number of operating nodes, energy efficiency, and the lifetime of the network. The number of operating nodes is a very crucial factor for the networks. However, the number of operating nodes can vary with time due to various artificial as well as natural reasons (for example, some nodes might fail and some could be damaged because of fouling and corrosion, or batteries might fail). It is therefore a matter of great interest for a communication network to know how many operating nodes or transmitters are available in the region at any point in time to ensure proper network operation (such as routing), as well as to obtain optimum performance or to prevent failure of the mission by network maintenance (such as replacement of faulty nodes). Similarly, a concurrent estimation of the dimensionality of the network might also be important for localising the nodes and estimating their number in a deployed network. To date, techniques employed to estimate the number of nodes and dimensionality have been based on some aspect of the communications protocol(s) in use. The protocol technique can be very hard to implement in harsh environment (e.g. underwater) due to the unavoidable capture effect, poor efficiency due to long propagation delay, high path loss, etc. In this thesis, we propose a novel estimation technique based on cross-correlation of random signals, in which the ratio of the mean of the cross-correlation function to its standard deviation determines the number of nodes. Within the limited scope of this thesis, we have provided some estimation techniques to estimate the number of nodes and network dimensionality. The proposed number of node estimation techniques also addresses a number of practical issues in a digital receiver and channel, including fractional-sample delays, multipath reception, noise etc. An error analysis is provided with comparison to conventional protocol techniques that demonstrates the superior performance of this technique to protocol-based methods. The thesis includes an initial verification of the performance of the proposed techniques and suggests other issues for future verification.
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Anower, Md. Shamim
Frater, Michael
Ryan, Michael
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PhD Doctorate
UNSW Faculty
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