Context-aware Media Independent Information Server for Optimized Seamless Handover Procedures
; Pires, H. P.
Computer Networks Vol. 55, Nº 7, pp. 1498 - 1519, May, 2011.
ISSN (print): 1389-1286
ISSN (online): 1389-1286
Journal Impact Factor: 1,304 (in 2008)
Digital Object Identifier: 10.1016/j.comnet.2011.01.022
The proliferation of the Internet and wireless access technologies introduced the constant mobile paradigm, in which users want to be always connected making use of the best available networks and technologies. In order to provide seamless connectivity among the new wireless access technologies, such as Wi-Fi, WiMAX and 3GPP (UMTS, HSPA and/or LTE), the IEEE 802.21 standard has defined the media independent handover framework. However, although there is a recognized importance of the IEEE 802.21 framework in the vertical handover optimization procedures, it is still necessary to improve this in what the radio access technologies individual features are concerned. Moreover, the IEEE 802.21 standard defines an information server that is only able to manage static network information. It is clear that in current and future environments, dynamic context information from the terminal and the network side entities is very important for the vertical handover decision procedures. This paper presents the integration process of the MIH framework with the aforesaid wireless access technologies, enabling the complete support of all the envisioned IEEE 802.21 handover phases. It describes how IEEE 802.21 can be adapted to the specific characteristics of the access technologies, and the mechanisms required to perform the several handover phases between Wi-Fi, WiMAX and 3GPP. Furthermore, this paper addresses a new concept of a context-aware information server that is able to store, manage and deliver real-time dynamic information retrieved from both the network and the terminal side entities, such as the user preferences, running services, mobile nodes characteristics and available network resources. The purpose of this context-aware information server is to optimize the handover preparation and decision phases. Additionally, a meticulous evaluation of the depicted handover mechanisms optimized by the IEEE 802.21 framework is presented, demonstrating that seamless handover between WiMAX, Wi-Fi and 3GPP access networks is achieved with low latency and no packet loss. Finally, the benefits of integrating a context-aware information server in the seamless handover procedure are also evaluated. To perform this evaluation, significant add-ons, also described in this paper, were implemented in the NS-2 simulator to support all the functionalities defined by the IEEE 802.21 standard, as well as the proposed extensions to the standard.