Placement of Relay Stations in WiMAX Network Using Glowworm Swarm Optimization

Placement of Relay Stations in WiMAX Network Using Glowworm Swarm Optimization

Sangeetha J (M S Ramaiah Institute of Technology, Bengaluru, India), Keerthiraj Nagaraj (University of Florida, Gainesville, USA), Ram Prakash Rustagi (Kammavari Sangha Institute of Technology, Bengaluru, India) and Balasubramanya Murthy K N (PES University, Bengaluru, India)
Copyright: © 2019 |Pages: 29
DOI: 10.4018/IJAMC.2019070103
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The Relay Station (RS) deployment problem for WiMAX networks is studied. Unlike Base Station (BS), RS does not need a wire-line backhaul and has much lower hardware complexity. Hence, usage of RSs can significantly minimize the deployment cost and maximize the network coverage of the system. To solve the RS deployment problem, the authors have used a nature inspired technique known as Glowworm Swarm Optimization (GSO). Different cases have been considered for a single fixed BS, to find the feasible number of RSs and its optimal placement in WiMAX networks. Computational experiments are conducted to show the effect of RS deployments in different distribution scenarios. This article also shows the impact of placing RSs at optimal locations to serve given Mobile Stations (MSs) that are distributed arbitrarily in a given geographic region such that the cost is minimized, and the network coverage is maximized. The results obtained from the GSO algorithm are compared with k-means algorithm and it is observed that GSO performs better than k-means algorithm.
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1. Introduction

Broadband wireless access technology provides last mile connectivity problem, and to address this problem many standards have been developed. One such standard is IEEE 802.16 or WiMAX (Worldwide interoperability for Microwave Access) network (Andrews et al., 2007) which was developed in 2001. Initially IEEE 802.16 standard was designed to satisfy the need of fixed user and to have a Line-Of-Sight (LOS) to the Base Station (BS) for the Internet access. Later, IEEE 802.16e (IEEE Std. 802.16, 2009) standard was designed to support mobile user (Balipadia & Sangeetha, 2016) and to have Non-Line-Of-Sight (NLOS) to the BS. This standard defines WiMAX network consisting of one BS and multiple MSs. A BS is located at the center of the cell and provides coverage within the cell only. The BS supports both fixed users and mobile users with Internet access.

In the literature, several studies have been proposed for network deployment using IEEE 802.16e standard (i.e. mobile WiMAX) (Oh & Kim, 2011; Al Tamimi et al., 2010; Sangeetha, Goel, Rustagi, & Murthy, 2017). As an example, Figure 1 shows direct connectivity of few MSs to a BS in a cell. The constraint of this deployment is that it is not always possible to provide high data rates to MSs, especially to those which are located at the cell edge or which are in area which is not reachable (coverage hole) or which are placed in the shadow of a building (Peters & Heath, 2009). To address these problems, one could consider shrinking the cell size and thereby installing a large number of BSs in a given area. This solution will likely increase network capacity (i.e. higher data rates) because MSs are located much closer to its serving BSs. However, the benefit of this solution is limited because deploying additional BSs (Nathanzon et al., 2008) leads to high cost. The cost includes wired backhaul connectivity and an antenna space in the network. Hence, to reduce the cost of placing large number of BSs, the Relay Stations (RSs) are used to interconnect the BS and MSs. This is proposed in IEEE 802.16j standard (IEEE Std. 802.16j, 2009; Peters & Heath, 2009), which was developed in the year 2009. This is also known as Mobile Multi-hop Relay (MMR) network, which is a modification to IEEE 802.16e standard (i.e. mobile WiMAX).

The IEEE 802.16j standard targets on the network coverage and capacity extension. This standard adds relay support to the mobile WiMAX (Wang et al., 2008; Ahmadi 2009). Thus, IEEE 802.16j (Peters & Heath, 2009) subscribers are expected to experience performance improvement in terms of network coverage and capacity through a low-cost RS. This standard is fully compatible with all the earlier standards of WiMAX network. In IEEE 802.16j WiMAX network (Bayan & Wan, 2011), traffic and signaling from MS can be directly communicated with the BS (i.e. when MS is in the coverage range of its serving BS) or routed through one or more number of RSs. The RSs helps in extending network coverage and performance of the network.

Figure 1.

Topology of IEEE 802.16e Network


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