Network Selection Algorithm Based on Diff-AHP and TOPSIS in Heterogeneous Wireless Networks Mohamed Lahby, Leghris Cherkaoui, Abdellah Adib Department of Computer Science, LIM Lab. Faculty of Sciences and Technology of Mohammedia B.P. 146 Mohammedia, Morocco Email: {mlahby, cleghris, adib adbe}@yahoo.fr Abstract—The most important issue in the fourth generation (4G) of wireless communications is how to select the most suitable access network to be used for communication when several access networks are available. To achieve this issue, network selection is intended to choose the most suitable network in terms of quality of service (QoS) for mobile users. This paper proposes a new technique for network selection decision. This technique combines two multi attribute decision making (MADM) methods such as diff-analytic hierarchy process (Diff-AHP) and the technique for order preference by similarity to an ideal solution (TOPSIS). The Diff-AHP method is extension of AHP method which be used to find the differentiate weights of available networks by considering each criterion and TOPSIS method is used to rank the alternatives. Keywords-Heterogeneous Multi-Access, Network Selection, Multi Attribute Decision Making, Diff-AHP, TOPSIS. I. I NTRODUCTION The evolution of the mobile terminals towards a multimode architecture will allow the users to benefit simultaneously from various radio access technologies (RAT’s) such as wireless technologies (802.11a, 802.11b, 802.16...) and cellular net- works (GPRS, UMTS, HSDPA...). The most important issue in RAT’s, is to provide ubiquitous access for the end users, under the principle “Always Best Connected” (ABC) [1]. For that, a vertical handoff decision [2] is intended to determine whether a vertical handoff should be initiated, and to choose the most suitable network in terms of quality of service (QoS) for mobile users. The vertical handover process can be divided into three parts namely: handover initiation, network selection and handover execution. In this paper we focus on the second step of the vertical handover. For that, we propose a new technique for network selection decision which allows to the user to choose the most suitable network in terms of QoS. No single wireless network technology is considered to be more favorable than other technologies in terms of QoS. In addition, the network selection decision depends on multiple criteria [3] which are: • From terminal side: battery, velocity, etc. • From service side: QoS level, security level, etc. • From network side: provider’s profile, current QoS pa- rameters, etc. • From user side: users preferences, perceived QoS, etc. The network selection problem can be tackled with several schemes and decision algorithms such as multi-attribute de- cision making (MADM) methods, genetic algorithms, fuzzy logic and utility functions. In [4] the authors have proposed a new strategy to solve the vertical handover decision problem by using the fuzzy multi attribute decision making methods (Fuzzy MADM). In [5] the authors have proposed also an intelligent approach for vertical handover by using fuzzy logic. In [6] and [7] the network selection algorithm is based on analytic hierarchy process (AHP) and gray relation analysis (GRA) two MADM methods. The AHP method is used to determine weights for each criterion and GRA method is applied to rank the alternatives. In [8] and [9] the network selection algorithm combines two MADM methods AHP and TOPSIS. The AHP method is used to get weights of the criteria and TOPSIS method is applied to determine the ranking of access network. In spite of MADM methods represent promising solution to solve the network selection problem, they still suffer from the ranking abnormality and the ping-pong effect. The ranking abnormality means that the ranking of candidate networks change when the low ranking alternatives are removed from the candidate list, which can make the network selection inefficient. The ping pong effect occurs when the terminal mobile performs excessive handoffs for a given time which causing the higher number of handoffs. This phenomenon can led to increasing in power consumption and the decreasing in throughput. One major cause of these problems is the weighting algorithm [10] used to weigh different criteria. To cope with these problems, this paper proposes a new technique based on two MADM methods namely Diff-AHP and TOPSIS. The Diff- AHP method is extension of AHP method which be applied to find the differentiate weights of available networks by considering each criterion and TOPSIS method is used to rank the alternatives. Contrary to the AHP method which allows to associate the same weight vector for all available networks, our Diff-AHP method allows to attribute different weight vector according to specific access network. This paper is organized as follows. Section II describes Multi Attribute Decision Making methods (MADM). Section III presents our access network selection technique based on Diff- AHP and TOPSIS. Section IV includes the simulations and results. Section V concludes this paper. 978-1-4673-1520-3/12/$31.00 ©2012 IEEE