Abstract
The next generation of mobile wireless communications represents a heterogeneous environment which integrates variety of network generation like third generation (3G), fourth generation (4G), and fifth generation (5G). The major challenge in this heterogeneous environment is to decide which access point to use when multiple networks are available. Process of roaming mobile user from one technology to anther different is called vertical handover. In this chapter, the authors propose a new mechanism based on graph theory and cost function in order to determine the best path for the end user in terms of quality of service (QoS) when the vertical handover process is needed. Then, they investigate the impact of some existing weighting methods in order to determine the suitable method which can be coupled with the cost function. The experiments evaluation by using Mininet emulator demonstrate that the proposed approach can achieve a significant improvement concerning four QoS metrics: throughput, packet lost, packet delay, and packer jitter for two services FTP and video streaming.
Top1. Introduction
The future networked world have integrated multiple wireless network technologies like the third generation (3G), the fourth generation (4G) and the fifth generation (5G). The 3G mobile system is designed to support multimedia services and video teleconferencing with data rate of 2 Mbps to 11 Mbps. The 3G can be divided into two groups. The first group represents cellular networks designed by the International Telecommunication Unit’s (UIT). The universal mobile telecommunication system (UMTS) is one of the most popular 3G network. The standardization of UMTS network (Javier, & Mamadou, 2001) is carried out by Third Generation Partnership Project (3GPP). In addition the UMTS network can provide wireless data with data rate of 2Mbps. The second group of 3G systems consists of wireless access networks specified by IEEE 802.11 committee (IEEE 802.11. 2007). These networks include WiFi (IEEE 802.11 a) and its extended systems such as IEEE 802.11b, IEEE 802.11n, etc. For example, the IEEE 802.11 a technology can ensure data rate of 11 Mbps. Furthermore, the 4G technology is on all IP system characterized with high data rate and high coverage area. The 4G system can integrate cellular networks such as Long Term Evolution (LTE) and wireless networks such as Interoperability for Microwave Access (WIMAX). The LTE network (Barth, 2006) is specified by 3GPP in December 2008, this standard allows supporting a variety of services such as interactive and streaming. The WiMax network (IEEE 802.16) is specified by the IEEE 802.16 committee (IEEE 802.16. 2004). This technology have been deployed in order to provide high data and to support multimedia applications. Actually both 3G and 4G have been increasing demand of utilization in spite of their limitations in term of coverage, bandwidth and mobility. In this context, in order to enhance the quality of service (QoS), to ensure high mobility and to increase the bandwidth, the companies of telecommunications are currently driving the development of the fifth generation network (5G). This new generation will provide the foundational infrastructure for building many applications such as Internet of Energy (IoE), Internet of Things (IoT), and Internet of Vehicles (IoV).
In parallel, the development of new mobile devices equipped with multiple network interfaces allow users to roam seamlessly between different technologies by using the vertical handover process (Lahby, 2013). Consequently, the users have the privilege to use different services like voice, data, web browsing, and video streaming by using different technologies at anytime and anywhere. The vertical handover can be divided into three parts namely: handover initiation, handover decision (it is also called network selection) and handover execution. The present chapter focuses on the second part which is considered the principle key of the vertical handover. However, how to choose the most suitable access network by satisfying Always Best Connected (ABC) Paradigm (Gustafsson & Jonsson, 2003), becomes a significant challenge during the network selection process, in this heterogeneous environment. To deal with this issue, several algorithms and strategies have been proposed in the literature in the recent years
Up to our knowledge, most of these existing references, have studied the network selection in the context of selecting only one access technology. In this chapter, we propose new mechanism based on graph theory and cost function in order to determine the best path for the end user in terms of quality of service (QoS). Firstly we introduce graph theory for modeling the network selection problem as graph. Then we use the cost function to calculate the weight of each edge and they apply the Dijkstra's algorithm to determine the best path in terms of QoS. Finally, we investigate the impact of some existing weighting methods in order to determine the suitable method which can be coupled with the cost function.
This chapter is organized as follows, in section 2 we outline some of existing works related to vertical handover algorithms which proposed during the last decade. In section 3 we discuss several existing weighting algorithms based handover. In section 4 we describe our new approach based on graph theory and cost function to deal with vertical handover problem. Section 5 comprises the testbed and the experimental results. Section 6 presents conclusion of this chapter, open issues and future works.
Key Terms in this Chapter
Handover: In cellular telecommunications, the terms handover or handoff refer to the process of transferring an ongoing call or data session of mobile terminal from one access network to another access network. Basically, handovers are mainly classified into horizontal and vertical handovers. Handover within same access networks is referred to as horizontal handover, while handover across heterogeneous access networks is referred to as the vertical.
International Telecommunication Unit (ITU): Is the leading United Nations agency for information and communication technologies. As the global focal point for governments and the private sector, ITU’s role in helping the world communicate spans 3 core sectors: radio-communication, standardization and development. ITU also organizes TELECOM events and was the lead organizing agency of the World Summit on the Information Society.
Throughput: For each access network, this parameter represents the ratio of total successful data delivered over a communication channel per unit time.
Handover Execution: It consists on establishing the target access network by using mobile IP protocol.
Quality of Service (QoS): Refers to the description or measurement of the overall performance of a service, such as access network or a cloud computing service, particularly the performance seen by the users of the network. To quantitatively measure quality of service, several related aspects of the network service are often considered, such as throughput, packet loss, packet delay, packet jitter, etc.
Handover Initiation: During this step, the mobile terminal discovers available networks. In addition, some initial parameters for measurement and handover are configured. Measurement related parameters may include the required link quality, measurement metrics, measurement interval, and so on.
Packet Loss: Is the ratio of the number of the failure of packets and the number of packets originated by the source.
Always Best Connected (ABC) Paradigm: Means that the users have the possibility to connect to applications using the devices and access technologies that best suit his or her needs, thereby combining the features of access technologies such as Bluetooth, Wifi, WiMax, UMTS, and LTE. In addition, a user is able to choose the best available access networks at anywhere and at any in time by using mobile terminal equipped with multiple interfaces.
Packet Delay: Is defined as difference between time taken by the transmitted packets from source to destination. It includes all possible delays in the network like buffering route discovery latency, and propagation and transmission delay.
Packet Jitter: Is defined as a variation in the delay of received packets. At the sending side, packets are sent in a continuous stream with the packets spaced evenly apart.
Handover Decision: It’s namely also network selection. In this step the mobile terminal evaluates the reachable wireless networks to make a decision according some criteria such as battery, velocity, QoS level, security level, users’ preferences, perceived QoS, etc.