EVALUATION OF A TECHNOLOGY-AWAREVERTICAL HANDOVER ALGORITHM BASED ON THE IEEE 802.21 STANDARD UMT S WiMA WiFi USER X Other Hetrogenous network
INTRODUCTIO N The availability of diverse wireless access technologies such as (Wi-Fi), (WiMAX), and (UMTS) allows users to stay “always on”. Users demand continuous connectivity guaranteeing the Quality of Service (QoS) required for their communications. The “always best connected” word is fullfilled by Vertical Handover (VHO) techniques make possible to switch from one wireless technology to another in a seamless manner, offering to mobile users the possibility to remain connected under certain QoS criteria. Concept of VHO is switching from one technology to another, it takes into account service continuity, network discovery, network selection, security, mobility management, and QoS issues. The mobile devices connect to these technologies by relying on multi-interfaces under the IEEE 802.21 standard.
INTRODUCTION CONTD… The authors developed an application based on Mobile IP and routing issues which was able to manage handovers among different networks such as the IBM Infrared Wireless LAN, the AT&T Wave LAN and the Metricom Ricochet Network as in-building, campus, and wide area underlying wireless technologies. The IEEE 802.21 Working Group is working on the Media Independent Handover Services Protocol which provides a homogeneous function-interface between heterogeneous network technologies. The use of the Received Signal Strength (RSS) and services of IEEE 802.21 gives evidences that when the VHO is initiated by the mobile node (MIHO) evaluating the VHO latency as well as the VHO Packet loss.
MEDIA INDEPENDENT HANDOVER FUNCTION (MIHF) Media Independent Handover (MIH) is a standard being developed by IEEE 802.21 to enable the handover of IP sessions from one layer 2 access technology to another. It have 2 layer 1) lower layer- acessed by different fuction to retreive detect,prepare, execute VHO. 2) upper laye- demands informations. Services offered are: MIES, MIIS, MICS
MIES- EVENTSERVICE This service detects the changes on the lower layers, e.g. changes on the physical and data link layer. The MIHF notifies events occurring in the lower layers to the MIHUs as they have requested. The MIES covers events such as: • State change events (link up, link down, link parameter changes). • Predictive events (link going down). • Network initiated events (load balancing, operator preferences).
MIIS- INFORMATIONSERVICE The MIIS allows the MIHF to discover its network environment gathering information that the upper layers make use of to make decisions. The information elements refers to the list of available networks, location of Point of Attachment (PoA), operator ID, roaming partners, cost, security, QoS, PoA capabilities, and Vendor specific information, among others.
MICS- COMMANDSERVICE The MICS allows the MIHU to take control over the lower layers through a set of commands. Like Initiate, Prepare, Commit and Complete commands With the information gathered by the MIES and MIIS, the MIHU decide to switch from one PoA to another. The commands allow not only to execute the handover, but to set different parameters in the lower layers elements.
OVERVI EW Figure 4 shows the state diagram of the VHA when selecting a candidate network to switch to. As observed, the MIHF set at User Equipment (UE) is continuously sensing the interfaces. When an event is trig gered, and depending on the type of event, the VHA perfor ms different routines and subroutines based in MICS and MIES , to select the best candidate network, or simply chooses the UMTS network by default, due to the full UMTS coverage. Finally, considering the execution phase of the VHO process, we use Mobility support for Inter net Protocol v.6 (MIPv6) to manage the mobility issues. It is important to emphasize that the 802.21 events: LINK UP and LINK DOWN, determine the behavior of the VHA. When a LINK DETECTED event occurs, events such as LINK UP if the technology detected is able to offer more bandwidth, MIPv6 Is in charge of this negotiation and notification to different components of the system. All these processes require complex actions which implies latency. when a LINK DOWN event is detected, only a notification is performed by the MIPv6 agent, since the interface was already configured in a previous LINK UP. So, there is no added latency to these processes.
EVALUATION (TECHNOLOGY PERFORMANCE)UMTS takes average of 29.6ms to deliver one packet,WiMAX gives 0.81 and WiFi gives 0.23ms of latencies respectively
Switching form high to low bandwidth experience high packet loss.
CONCLUSIONS IEEE 802.21 allowed interoperability among different technologies Author tried experiments to evaluate VHA on aviability and capacity for decision making. Work was based on totally NS2. Final conclusion; different improvement can be suggested to outperform the current evaluated VHA when conditions differ. In high degree of congestion and other parameters(user preference, mobile capabilities, etc.) require sophisticated decision algorithms
REFRENCES M. Stemm and R. H. Katz, “Vertical handoffs in wireless overlay networks,” Springer Mobile Networks and Applications., vol. 3, no. 4, pp. 335–350, 1998. Johann M´arquez-Barja, Carlos T. Calafate, Juan-Carlos Cano and Pietro Manzoni “Evaluation of a technology-aware vertical handover algorithm based on the IEEE 802.21 standard ” in Valencia, Spain,2011. www.ieee802.org/21/ en.wikipedia.org/wiki/IEEE_802.21 www.uwspace.uwaterloo.ca/.../MASc-thesis- YongqiangZhang%20new.pdf