WiMAX Security and Quality of Service

An End-to-End Perspective

Seok-Yee Tang, Peter Muller, Hamid Sharif, Seok-Yee Tang, Peter Muller, Hamid Sharif

• Publisher: Wiley
• Year: 2011
• Print ISBN:
  9780470721971
• Edition: 1
• eBook ISBN:
  9781119956204
• Topic: Technology & Engineering
• Subtopic: Electrical Engineering & Telecommunications
• Index: Technology & Engineering

WiMAX is the first standard technology to deliver true broadband mobility at speeds that enable powerful multimedia applications such as Voice over Internet Protocol (VoIP), online gaming, mobile TV, and personalized infotainment. WiMAX Security and Quality of Service, focuses on the interdisciplinary subject of advanced Security and Quality of Service (QoS) in WiMAX wireless telecommunication systems including its models, standards, implementations, and applications. Split into 4 parts, Part A of the book is an end-to-end overview of the WiMAX architecture, protocol, and system requirements. Security is an essential element in the wireless world and Part B is fully dedicated to this topic. Part C provides an in depth analysis of QoS, including mobility management in WiMAX. Finally, Part D introduces the reader to advanced and future topics.

• One of the first texts to cover security, QoS and deployments of WiMAX in the same book.
• Introduces the primary concepts of the interdisciplinary nature of WiMAX security and QoS, and also includes discussion of hot topics in the field.
• Written for engineers and researchers, answering practical questions from industry and the experimental field in academia.
• Explains how WiMAX applications' security and QoS are interconnected and interworked among the cross layers.

Part D

Advanced Topics

8

QoS Challenges in the Handover Process

Marina Aguado and Eduardo Jacob

ETSI, Departamento de Electronica y Telecommunicaciones, University of the Basque Country, Spain

Marion Berbineau

Institut National de Recherche sur les Transports et leur Securite (INRETS), France

Ivan Lledo Samper

Bournemouth University, UK

8.1 Introduction

Currently, research is being carried out to develop a new generation of wireless mobile networks that provide broadband data communication in the high speed vehicular scenario. International Telecommunication Union, Radiocommunication Section (ITU-R) has proposed International Mobile Telecommunications (IMT-Advanced) technical requirements for supporting such usage scenarios. IMT-Advanced identifies those mobile communication systems with capabilities which go further than those of IMT-2000. The IEEE 802.16 standard, supported under the WiMAX network, has evolved from a fixed scenario, in IEEE 802.16d, towards a mobile typical vehicular scenario (up to 120 km/h) with IEEE 802.16e. In the near future, the IEEE 802.16m specification will cover mobility classes and scenarios supported by IMT-Advanced, including the high-speed vehicular scenario (up to 350 km or even up to 500 km/h).

IEEE802.16 initial standards adopted Data Over Cable Service Interface Specification (DOCSIS) Quality of Service (QoS) mechanisms. Similarly, the IEEE802.16 Medium Access Control (MAC) Security Sublayer, responsible for providing security mechanisms such as privacy, authentication and encryption over the air link, was also based on DOCSIS standard. However, DOCSIS is a wired based technology and QoS mechanisms in fixed wireless technologies, while sharing many of the features of QoS mechanisms for wired technologies, face some extra limitations including bandwidth limitations, longer end-toend delays and higher packet losses owing to channel-induced bit errors.

Additionally, QoS mechanisms in mobile broadband wireless technologies represent a step further in complexity. Time variability and the unpredictability of the channel become more acute and the main challenge arises from the need to hand over sessions from one cell to another as the user moves across their coverage boundaries. During this handover process, it is still necessary to provide session continuity and to offer the previously negotiated end-to-end QoS and security levels.

In this context, and from the end-to-end QoS point of view, the packet loss and additional latency introduced by the handover process is an issue which needs to be tackled. And from the security point of view, a new goal comes to light: to minimize the impact of security procedures on the performance of the handover process. Stronger security mechanisms, that is using stronger encryption methods and multiple layers of security or changing encryption keys more frequently, come at the price of compromising QoS performance (i.e. increasing processing time and therefore higher end-to-end delays).

This trade-off, security versus QoS performance, is highlighted during the handover process. This chapter focuses on enhancement techniques in the handover process that represent an improvement of global end-to-end QoS indicators.

This chapter is structured as follows. Section 8.1 describes the challenge that the han-dover process represents from the point of view of QoS performance indicators in the full mobility scenario. It describes the application of QoS requirements for the full mobility scenario. These requirements are related to end-to-end performance but will also apply to sessions involving handovers.

Section 8.2 is a necessary overview of the handover process in the IEEE802.16 standard; timing and performance considerations illustrate each stage in the handover process. Section 8.3 describes the Media Independent Handover (MIH) Initiative or IEEE802.21. Section 8.4 presents a survey on the different handover enhancement strategies found in the literature. These strategies are grouped, classified and discussed. Section 8.5 covers the efficient scheduling of the handover process and its influence on handover performance and end-to-end quality of service. To conclude, in section 8.6, a handover performance analysis is carried out.

8.2 Handover in WiMAX

When mobile broadband wireless technologies migrate from a nomadic scenario to a typical vehicular or a high speed vehicular usage scenario, the supported mobile speed increases, the dwelling time within a cell decreases, and the time variability as well as the channel unpredictability become more acute.

The time during which the mobile node is involved in handover processes compared to normal operation increases. Consequently, end-to-end QoS indicators, such as delay time or data loss, are significantly more affected by QoS handover performance indicators. Therefore, as WiMAX technology reaches higher mobility scenarios, a heavy burden is placed upon the performance of the handover process and mobility management solutions. This leads one to consider the handover process as a fundamental research topic and the critical issue to be considered as WiMAX technology reaches higher mobility scenarios.

WiMAX architecture is expected to support six different usage scenarios: fixed, nomadic, portable, simple mobility, full mobility and the high speed vehicular scenario. In the simple mobility scenario at least one of the mobile nodes involved in the communication flow performs its trajectory at a speed of up to 50 km/h. In the full mobility usage scenario at least one of the mobile nodes involved in the communication flow performs its trajectory at a speed of up to 150 km/h. The characterization of this full mobility usage scenario from a telecommunication point of view is that one in which:

• the mobile node stays connected to the network and experiences no performance degradation at mobility speeds up to 150 km/h;
• there is session continuity
• real and non real time applications are supported while moving, including during the handover process;
• any pre-negotiated QoS levels are supported across multiple Base Stations (BSs) at all times;
• the total handover latency is below 50ms;
• there is bounded packet loss (e.g., < 1 %) during handovers.

These features may be viewed as the requirements that Mobile WiMAX networks are expected to meet when supporting real time applications in the full mobility scenario.

8.3 The IEEE802.16 Handover Process

In order to propose a strategy for enhancing the handover process it is necessary to study the IEEE 802.16 handover mechanisms and internal features, along with timing considerations. This overview allows one to identify the main points where enhancement strategies may be implemented. This section details some specific IEEE802.16e standard concepts and procedures that are involved in the handover process. First, subsection 8.2.1 details the specific network entry procedure. Second, in subsection 8.2.2, some of the details of the IEEE802.16e specific network topology advertising and network topology acquisition strategy are outlined. The next subsection covers the association procedure. We conclude this section detailing the different stages in the handover process.

8.3.1 The Network Entry Procedure

The first process to be considered when studying the handover process is the network entry procedure. It must be taken into account that a handover process worst case scenario represents a complete re-entry procedure. Figure 8.1 presents the network entry procedure. The implementation of phases represented in the light grey blocks is optional.

8.3.1.1 Scan for DL Channel and Establish Synchronization with BS

The Mobile Station (MS) begins to scan the possible channels of the downlink (DL) frequency band of operation until it finds a valid DL signal. Once the physical (PHY) layer has obtained synchronization, as given by a PHY trigger indication, the MAC layer will attempt to acquire the channel control parameters for the DL and then the uplink (UL). The MS searches for the DL frame preambles. The preamble initiates the downlink subframe. When one is detected, the MS can synchronize itself with respect to the DL transmission of the BS. The MS then obtains the PHY DL synchronization.

Figure 8.1 Initialization of an MS (Mobile Station), ...

Table of contents

• Cover
• Title
• Copyright
• Preface
• Acknowledgements
• Contributors
• Acronyms
• Figures
• Tables
• Part A Introduction
• Part B Security
• Part C Quality of Service
• Part D Advanced Topics
• Appendix
• Index