Hierarchical Cooperation in <emphasis emphasistype="italic">Ad Hoc</emphasis> Networks: Optimal Clustering and Achievable Throughput

Abstract

Abstract-For a wireless network with n nodes distributed in an area A, and with n source-destination pairs communicating with each other at some common rate, the hierarchical cooperation scheme proposed in (Ozgur, Leveque, and Tse, 2007) is analyzed and optimized by choosing the number of hierarchical stages and the corresponding cluster sizes that maximize the total throughput. It turns out that increasing the number of stages does not necessarily improve the throughput, and the closed-form solutions for the optimization problem can be explicitly obtained. Based on the expression of the maximum achievable throughput, it is found that the hierarchical scheme achieves a scaling with the exponent depending on n. In addition, to apply the hierarchical cooperation scheme to random networks, a clustering algorithm is developed, which divides the whole network into quadrilateral clusters, each with exactly the number of nodes required.

Analysis of quantization effects on the performance of cooperative MIMO techniques in wireless networks

“…This channel model has broadly been used in the literature, e.g., see [9,10]. Network throughput is defined as the rate at which all the source nodes send their information to destination http://jwcn.eurasipjournals.com/content/2012/1/290 nodes and depends on the spatio-temporal transmission strategies used in the network as discussed later.…”

“…In the last phase, upon reception of the signals transmitted in the second phase, the nearby nodes at the destination side form a virtual MIMO receiver and cooperate with each other to decode the original data at the destination node. As an example of such strategy, we continue our discussion based on the framework developed in [10]. In the network, each node is a source of data for exactly one other node, and also, it is destination of data for exactly one other node.…”

“…This superior performance is due to the cooperative nature of the scheme. Consequently, it has sparked a new wave of interest in the researchers to investigate the role of cooperative MIMO schemes in ad hoc networks (e.g., see [10][11][12]). …”

“…In order to clarify contributions of this article compared with [9,10], it should be noted that our focus in this article is on the optimization of the quantization process, rather than on proposing a new network communication scheme. In fact, the issue of optimization of number of quantization bits is not addressed in [9,10] while as will be shown, intelligent management of this issue results in significant throughput enhancement.…”

“…In fact, the issue of optimization of number of quantization bits is not addressed in [9,10] while as will be shown, intelligent management of this issue results in significant throughput enhancement.…”