QoS and Security Challenges in the high mobility scenario: the Handover Process
|Series:||-||Book title:||WiMAX Security and Quality of Service: Providing and End to End Explanation|
Currently, research community efforts are being carried out to develop new generation wireless mobile networks that provide broadband data communication in the high speed vehicular scenario. ITU-R (International Telecommunication Union, Radiocommunication Section) has proposed the IMT-Advanced (International Mobile Telecommunications) 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 (up to 120 km/h) with IEEE 802.16e. In the near future, the IEEE 802.16m specification will cover the mobility classes and scenarios supported by the IMT-Advanced, including the high-speed vehicular scenario (up to 350 km or even up to 500 km/h).
IEEE802.16 initial standards adopted DOCSIS (Data Over Cable Service Interface Specification) QoS (Quality of Service) mechanisms. Similarly, the IEEE802.16 MAC (Medium Access Control) 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 details with QoS mechanisms for wired technologies, faces some extra limitations including: bandwidth limitations, longer end to end delays and higher packet losses due to channel-induced bit errors.
Additionally, QoS mechanisms in mobile broadband wireless technologies represent a step further in complexity. The time variability and 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.