18-07-2014, 09:44 AM
IMPROVING HANDOVER PERFORMANCE IN HMIPV6 USING AREA BORDER ROUTES IN WIRELESS MOBILE NETWORKS
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Abstract
Hierarchical Mobile IPv6 (HMIPv6) introduces a mobility anchor point (MAP) that localizes the signaling traffic and hence reduces the handoff latency. To support inter-area handovers, several methods have been proposed in the literature to address the challenging problems of minimizing the handoff signaling delay and call blocking probability for Hierarchical Mobile IP version 6 (HMIPV6). In this paper, we propose a new concept for inter-area handovers to solve signaling delay and call blocking probability. In this concept, the border zone is made between two different neighboring cells. Each neighboring cells is assigned as MAP region. Since the border zone is an overlapping MAP region, MHs can maintain the same MAP as long as they remain inside the border zone.
Introduction
1.1 Overview and Motivation
The Internet is rapidly evolving in to a global and ubiquitous communication network infrastructure. Traditionally it is a wire-lined internet work and serves as a network computing environment only for station any computers. In recent years, the tremendous increase in the number of portable computing devices used, such a slap top computers, palmtop computers, Personal Digital Assistants (PDAs) raise depressing need for a mobile computing environment that incorporates both wireless and wired networking technologies.
Although mobility may be handled by individual applications [1, 2] most of the related work is focused on network layer mobility support. Since it ensures better inter-operability with the existing infrastructure [3]. Mobile IP [4{7] has been standardized by IETF, which allows a mobile computer to change its location with out restarting its applications and without disrupting any ongoing communications. Hierarchical structure has been proposed for Mobile IP to enhance its scalability and improve its handoff performance [8, 9]. Using multicast is an other possible way of handling network layer mobility [10]. A more common practice, however, is to use multicast together with Mobile IP to improve handoff performance [1{14].
There are also some work dealing with the micro-mobility problem that is more suitable for frequent mobility among small cells [15{19]. Also, in recent years there have been quite a lot of efforts in providing Integrated Services, i.e., both real-time services and traditional best-effort services, on the Internet [20] .Examples of real-time services include video-on-demand, video conferencing, interactive TV, Internet Telephony, etc.[21{30]. These multimedia applications possess significantly different characteristics from best-effort services. They require Quality of Service (QoS) commitment, for example, an absolute or statistical bound on the delivery delay of each packet from the underlying network, but this cannot be provided by the current Internet.
Hence IETF has developed the Integrated Service QoS architecture [31] that introduces two service models other than the best-effort model for real-time services: the Con- trolled Load Service [32] and Guaranteed Service[3]. A key component in this architecture is a resource reservation
signaling protocol used to setup prior band-width at intermediate nodes to ensure QoS. This can be done by RSVP [34{38], which is also standardized by IETF.
As portable computing devices become more and more powerful and wireless access technologies become more advanced and offer increasingly higher bit rates, mobile users are now demanding the same real-time services available to stationary users. Thus the provision of QoS guarantees in wireless and mobile networks has recently attracted lots of research efforts. The work of Singh and Brown [39{41] calls for modification to transport protocols such as User Datagram Protocol (UDP). Talukdar et al.[42{4],Chen[45],Awduche[46], and Mahadevan et al. [47,48] share the idea of making RSVP reservation in advance in the cells that the mobile node is going to visit so that the QoS provision during handoff could be seamless.
However, the difficulty is to know where the mobile node is going in advance. If it is not known, resources have to be reserved in all neigh boring cells that the mobile node may visit, but this wastes resources. Although new RSVP reservation models defined, such as active reservation and passive reservation, may alleviate this problem, they also complicate the protocol it self. Therefore, Andreoli and Zhang [49] argue that seamless handoff QoS provision may be too much to ask of a wireless mobile environment with scarce resources.
In their scheme, the handoff Mobile IP and RSVP signaling are performed in parallel with no resource pre-reservation in neighboring cells considered. This direct inter working of Mobile IP and RSVP yields a simpler approach to support QoS in a mobile environment, at the cost of possible QoS disruption during handoff. A part from all the work on the current Internet to accommodate new requirements from the user and applications, the Internet Protocol (IP) it self is undergoing a major migration now.
The explosively growing popularity of inter networking has resulted in a wide consensus that the world is running out of 32 bit IPv4 addresses. This primary concern, along with several other limitations inIPv4, is the driving force for a new protocol, known as Next Generation Internet Protocol (IPng) or Internet Protocol version6(IPv6)[50] defined by the IETF to ultimately replaceIPv4. A next logical step in the evolution is then, to provide real-time services to mobile users in the IPv6 context. This need is further reverenced by the recent trend in converging Third Generation(3G) wireless communication systems with Internet for simultaneous real and non-real time services[51{56], as well as the fact that 3G will adopt IPv6[57]. Currently IETF has defined
Mobile IPv6 [58] as the IPv6 version of Mobile IP. RSVP has also been specified to be usable in both IPv6 and IPv4.
Mobile IPv6-based real-time services, however, require mobility and QoS support simultaneously. This raises an apparent requirement for an inter working mechanism between in dependent IPv6 mobility and QoS protocols such as Mobile IPv6 and RSVP. This issue has been addressed by Chiruvoluetal.[59] and Fankhauseret al.[60]. Basically, both of them propose that after a mobile node's handoff, a new RSVP negotiation will be invoked to reserve resources for the new flow. Both approaches however, require the RSVP renegotiation to be performed end-to-end for each handoff, irrespective of how significant the handoff affects the flow path.
Thus a potential limitation of both approaches is-the required QoS handoff period could be unnecessarily long during which the application may suffer not able service degradation due to lack of QoS in the newly added portion of the flow path. Ensuring fast QoS handoff is always crucial for a good mobile QoS model, just as handoff performance is essential when dealing with mobility.
Thesis Contributions
Therefore, the motivation of our work is to minimize the handoff QoS renegotiation duration in RSVP and Mobile IPv6 integration, which will in turn minimize the handoff data packet delays and thus enhance the handoff performance of wireless mobile real-time services. The scheme proposed in this thesis is based on the fact that a single handoff usually affects only part of the routers with in the whole flow path. So it is possible to limit the handoff RSVP renegotiation only to the routers in the newly added portion of flow path, while those routers in the common portion of the old and new flow path could be exempted from handoff RSVP update.
To achieve this we introduce a flow transparency concept which requires the mobility support scheme to provide a constant flow identity for the application data flow at the network layer regardless of node mobility. By providing flow transparent mobility support for RSVP, we obtain a more efficient RSVP and Mobile IPv6 integration model with fast QoS handoff. The major contributions of this thesis are as follows:
IMPROVING HANDOVER PERFORMANCE IN HMIPV6 USING AREA BORDER ROUTES IN WIRELESS MOBILE NETWORKS
Mobile IPv6 Operation Overview
Mobile IPv6 has two basic functional entities:
Mobile Node- A mobile node is a node that changes its point of attachment from one network to another. A mobile node may change its location without changing its IP address. It may continue to communicate with other Internet nodes at any location using its (constant) IP address, assuming link- layer connectivity to a point of attachment is available.
Home Agent- A home agent is a router on a mobile node's home network that tunnels packets for delivery to the mobile node when it is away from home and maintains current location information for the mobile node.
The mobile node's ability to maintain ongoing communications even when changing its point of attachment to the network is enabled by a two-tier address scheme.
A mobile node is normally assigned two types of addresses. The first one is called home address, which is the mobile node's constant IP address that does not change as it moves from one network to another. The mobile node's home address is closely related to the mobile node's home agent and home network, which all share the same network -prefix. The other type of IP address is assigned to
a mobile node when it is visiting a foreign network and called Colo-cated care-of address. Colo-cated care-of address is an IP address temporarily assigned to an interface of the mobile node itself, so it can be used by only one mobile node at one time.
Figure2. Shows the Mobile IPv6 architecture. A Mobile Node (MN) first needs to determine whether it is currently connected to its home network or a foreign network. If it detects it has moved
to a foreign network, it will obtain a care-of address at the foreign network. Then the mobile node notifies its home agent of its care-of address; it also reports its care-of address to the Correspondent
Nodes (CNs). These two procedures are called Binding Update and the latter, binding update with the correspondent node is known as Route Optimization. Once the correspondent node knows the mobile node's new care-of address it will be able to send further packets directly to mobile node's care-of address, without going through the triangle route via mobile node's home agent as shown in the figure. The above brief over view of Mobile IPv6 operation contains three key components of the protocol, namely, Router Discovery, Address Notification, and Packet Routing, which will be further illustrated in the following sections.
Conclusions
In this paper, we have conducted a comparative study of border zone approach with the alternative where non-overlapping MAP domains are formed within the limit of the hierarchical area.HMIPv6 pre-reservation exhibits high call blocking probabilities, and end-to-end RSVP signaling delays. Multicast pre-reservation methods minimize the call blocking probability and RSVP signaling delays by reducing 50% cells in the MG compare with HMIPv6 shown in Table 1. By ensuring minimum signaling delay and call blocking in inter-area handovers, the introduction of the border zone is shown to outperform conventional approaches, which define detached MAP domains associated with each non-blocked hierarchical area. In this case the border zone approach study demonstrates its impact on producing significantly lower inter-MAP handover rates in the presence of high inter-area migrations, reducing the associated mobility signaling and routing overhead as well as the bandwidth blocking and dropping rates.