Telecommun Syst (2013) 52:1697–1704 DOI 10.1007/s11235-011-9661-7 Optimization of association procedure in WiMAX networks with relay stations Pavel Mach · Robert Bestak · Zdenek Becvar Published online: 14 September 2011 © Springer Science+Business Media, LLC 2011 Abstract When a MS enters to the WiMAX network, a net- work entry procedure has to be performed. The aim of pro- cedure is twofold. Firstly, several connections between the MS and BS are created, i.e. basic, primary and secondary management connections to control data transmissions. Sec- ondly, the MS is admitted into the network. According to the IEEE 802.16 standard, a MS always tries to associate to BS with the highest received signal quality. This method is suitable as long as the MS is directly connected to the net- work via BS. However by introducing relay stations to the WiMAX architecture, the MS entry procedure needs to be modified. Mainly, the point of attachment influences the net- work performance. This paper proposes an optimized asso- ciation procedure which takes into account the use of relays stations in the network. The obtained results show improve- ment of system performance. Keywords Association · Relay station · Radio resource cost · WiMAX · Path selection 1 Introduction The WiMAX technology is a worldwide wireless network- ing standard that addresses interoperability across IEEE The paper was originally presented in IWSSIP2008 conference. P. Mach · R. Bestak ( ) · Z. Becvar Department of Telecommunication, Czech Technical University in Prague, Technicka 2, 16627 Prague, Czech Republic e-mail: bestar1@fel.cvut.cz P. Mach e-mail: machp2@fel.cvut.cz Z. Becvar e-mail: zdenek.becvar@fel.cvut.cz url: www.cvut.cz/en 802.16 standard-based products. Until now, two standards were approved: IEEE 802.16-2004 [1] intended for fixed scenarios and the IEEE 802.16e [2] implementing to the for- mer standard mobility features such as handover or power management modes. Since requirements and demands to deliver high data transmission rates are increasing, existing technologies try to satisfy these trends. This is the main motivation why a new WiMAX working group, entitled as IEEE 802.16j, was established in 2006. The IEEE 802.16j [3] version intro- duces to WiMAX system network entities called Relay Sta- tions (RSs). The RS has two main purposes, i.e. to enhance the system capacity and to increase the network coverage (see Fig. 1). The RS represents a simplified Base Station (BS). It pro- vides media access management in its area and data transfer between BS/RS and Mobile Stations (MSs). The network efficiency and cost reduction can be significantly improved by this way. How to integrate the RSs into the IEEE 802.16 network is described in [4]. According to [5], three types of RSs are specified; fixed, nomadic and mobile RSs. This paper only considers fixed RSs, i.e. RSs installed at the same location. The RSs are in most cases build in, owned and controlled by service provider. The RS is not directly connected to the wired infrastructure and has minimum functionalities to support multi-hop communication. RSs can be further divided to transparent (T-RS) and non-transparent (NT-RS). In addi- tion, two types of NT-RSs can be considered: (i) centrally controlled RS (CC-RS) and (ii) de-centrally (in some papers denoted as distributed) controlled RS (DC-RS). More infor- mation about RS’s classification can be found for example in [6]. When a new MS associates to the WiMAX network, sev- eral steps have to be accomplished during the initial process.