Md. Akbar Hossain*, Khan Md. Rezaul Hoque† *Department of Telecommunication Engineering, Faculty of Engineering

† Department of Information and Communication Technology, Faculty of Science University of Trento, Italy

Email: mdakbar.hossain@studenti.unitn.it, khan@dit.unitn.it

Abstract- During the last decade wireless systems has experienced tremendous demands from social market. Subscribers now want a wider choice of services, better quality, faster response times, and greater coverage, which enhance the development of wireless technology than ever before. Among these, one of the greatest concerning problems for seamless global connectivity of mobile user is mobility management. The aim of this paper is to analyze the IP based Mobility management for next generation wireless networks. By the way of mobility management it is possible to locate roaming terminals for call delivery and maintain connections with mobile terminal that changes their points of attachment. In this paper it is also discussed how several type of mobility can be solved by Mobile IP and cellular IP.

I. INTRODUCTION

Now a days wireless communication systems are the fastest growing area of the communication sector. The protocol of IP plays an important role in the field of mobility management in various types of wireless networks. One of the key features of 4G is that it will be based on an all-IP infrastructure for both fixed and mobile networks. Moreover, positioning on network layer, IP acts as a masking isolator that prevents the protocols, services, and applications of upper layers from the awareness of network interconnecting architecture and possible changes caused. So, as a suitable layer to solve the problem of mobility and provide transparent mobility to applications and higher level protocols like TCP, IP becomes one of the most important research issues in mobility and location management, which results in various techniques and standards based on the extension of fundamental IP protocol proposed. The main goal of the mobile IP working group is to develop routing support to permit IP nodes (hosts and routers) using either IPv4 or IPv6 to seamlessly “roam” among IP sub networks and media types.

This article is organized as a general description and operation of mobile IP and IP based mobility management in section 2. In section 3 mobile IP optimization and advantages of MIPV6 are also

Fig. 1 Architecture of Mobile IP discussed. Intra-Domain Mobility management is described in section 4. Cellular IP as a solution of mobility management for next generation wireless communication is also describe in section 5.

II. IP BASED MOBILITY MANAGEMENT

A simple Mobile IP architecture is illustrated in Fig. 1. In this example, the CN sends packets to the MN via the MN’s HA and the FA.IP-based networking is designed such that each host is identified by a unique IP address. Standard IP routing assumes that IP addresses are distributed hierarchically. For example, a host with a certain subnet prefix is assumed to be located at the subnet referenced by that prefix, the home network. This dual use of IP addresses is fine when hosts are not mobile, as each host can be assigned its unique IP address according to the hierarchical structure needed for IP routing. However, it creates a problem when hosts need to be mobile. If a host moves to a foreign network, packets for it will still be routed to its home network. Furthermore, a host may obtain a temporary address in the foreign network for routing purposes, but there is no

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Fig. 2. Mobile IP with foreign agent

association between its temporary and permanent addresses. In MIP, each Mobile Host (MH) is still identified by its permanent IP address. However, for routing purposes, when an MH is roaming it obtains a temporary care-of-address (COA), which is a foreign network address that identifies the location of the MH. The MH registers this COA with a mobility agent in its home network known as its Home Agent (HA). The HA then stores the COA of the MH in a binding cache. Nodes communicating with the MH send packets addressed to its permanent address. These packets are routed to the MH’s home network, where it’s HA intercepts them and tunnels them (encapsulated) to its COA. The MH registers its latest COA with it’s HA whenever its COA is changes, which occurs when the MH moves to another foreign network. It should also refreshes the registration with it’s HA periodically. MIP can operate in two modes, namely with foreign agents or with co-located COAs, illustrated respectively in Fig. 2 and Fig. 3. In the mode with foreign agents, the visited network has a Foreign Agent (FA). The FA broadcasts its IP addresses that can be used as COAs. The MH picks a valid IP address of the FA as its COA and registers this with it’s HA (in this mode, the registration goes through the FA rather than directly to and from the HA). When packets arrive for the MH at the FA tunneled from the HA, they are un-encapsulated and forwarded to the MH through its layer 2 address previously registered with the FA. On the other hand, in the mode with co-located COAs, the MH would obtain a temporary IP address at the foreign network using a protocol such as DHCP (Dynamic Host Configuration Protocol). The MH would use this temporary IP address as its COA and registers this with HA.

Fig. 3. Mobile IP with collocated COA

Fig. 4. Mobile IP with Route Optimization

III. MOBILE IP OPTIMIZATION

To solve the problem of triangular routing, MIP with Route Optimization [3] (MIP-RO) has been proposed in Fig. 4. In order to use MIP-RO, a CH must understand binding updates and be able to tunnel packets to a COA, while the MH must send binding updates to the CH to update it on the MH’s location. The binding update informs the CH of the COA of the MH and hence the CH can tunnel packets to the COA without going through the HA. Several new messages, including “binding warning”, “binding update”, “binding request”, and “binding acknowledge”, are used to maintain the correct COA binding. While MIP-RO deals with the triangular routing problem, it does not address the issue of micro-mobility management. IPv6 is defined in the IETF working group of IP Next Generation [4], by providing enhancements over the capabilities of existing IPv4 service. Basic improvements to IPv4 include optimal header format, reasonable addressing architecture, neighbor discovery mechanism, stateless auto-configuration, and security and QoS support. Mobility support in IPv6 takes full advantage of these enhancements. Three advantages of MIPv6 are apparent: (a) route optimization is facilitated,

445IP BASED MOBILITY MANAGEMENT FOR NEXT GENERATION WIRELESS NETWORKS

Fig. 5 Mobile IPV6

without needing to be concerned about whether the CHs can understand binding updates, as with MIP-RO; (b) explicit binding updates or MIP registration messages become unnecessary, as the destination options are naturally piggy-backed on IP data packets; and (c) packets from CH to MH need not be encapsulated but are sent directly to the MH with its COA in the source route. The 3rd advantage just mentioned also is due to the way IPv6 makes source routing possible which is shown in fig. 5.

IV. INTRA-DOMAIN MOBILITY MANAGEMENT

To implement a fast and seamless handoff and a minimized control traffic micro mobility management solution are used for intra domain mobility management. Micro-mobility solutions that use a hierarchy of mobility agents include MIP with Regional Registration [5] (MIP-RR), and TeleMIP/Intra-Domain Mobility management Protocol [6] (IDMP). MIP-RR perhaps involves the fewest modifications to MIP. In a foreign network, the two level mobility hierarchy contains the upper-layer GFA (Gateway Foreign Agent) and several lower-layer RFAs (Regional Foreign Agent). All MHs under the GFA share the same COA. When a MH moves to another FA under the same GFA, it only needs to register with the new RFA and with the GFA. This is because its HA already knows how to route packets addressed to the MH to that GFA. It does not need to register with its HA unless it moves under a new GFA. Suppose an MH moves between subnets under a GFA with which it is already registered. As shown in Fig. 6(b), the MH initiates its registration with FA2. Then the registration request is sent to GFA1. Since MN is already registered with GFA1, GFA1 does not initiate a home registration to HA, but just sends the registration reply to the MH

Fig. 6 MIP Regional Registration (a) movement between

regions; (b) movement within a region

Fig. 7 Cellular IP

through FA2. Since the HA does not need to be contacted in this scenario, MIP-RR reduces the handoff latency caused by registration with Home Agent. If the MH changes its GFA, it needs to register with its HA. As shown in Fig. 6(a), the MH moves from FA3 to FA2, and its GFA is no longer GFA2. The MH sends a registration request to its new RFA, which is FA2, and then GFA1. Because GFA1 is a new GFA, it has to register with the HA.

V. CELLULAR IP

The cellular IP architecture in Fig. 7 consists of interconnected Cellular IP nodes (also known as Cellular IP base stations), these Cellular IP nodes communicate with Cellular IP mobile hosts. The Cellular IP gateway is a special Cellular IP Node as one of its interfaces is connected to a fixed standard IP network. The cellular IP base stations emits beacons on regular basis, this allows the mobile host to locate their nearest base station. When a Mobile host finds its nearest base station it sends a

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route update message to its connected base station, this message is routed internally in the cellular IP network from the base stations to Cellular IP Gateway by using a hop-by hop shortest path routing mechanism Cellular IP support two types of handover – hard and semi soft [7]. Hard handoff is usually described as a ‘break before make’ handoff, i.e. radio link communication is broken before the new radio connection is established. Semi soft uses the fact that certain radio technologies allow nodes to ‘listen’ to two or more base stations while connected/communicating to one base station. Mobile hosts on a foreign network listen to the base station transmit their beacons and determine if a handover procedure should be initiated by measuring the signal strengths. Once the mobile host receives a stronger beacon from a new base station it tunes itself to the new base station, hence it has stopped listening to the old base station, and sends a routing update message to the new base station. The routing update message creates the uplink\downlink route to the gateway and mobile host is now able to send and receive packets. During most of this time packets are still being sent to the mobile host old base station and hence lost. Since the mappings to the old base station are not cleared by the handover procedure, packets are being sent to both base stations until the mappings time out on the old route. The hard handover procedure is simple but the packet loss is not acceptable for real time applications. Using the fact the Mobile host can listen to the beacons of the base stations and determine when to handover, the Cellular IP protocol uses the Semi soft handover scheme. The Mobile host receives a stronger beacon from a new base station and sends a semi soft packet to it, the mobile host then immediately returns listening to the old base and it’s currently connected base station. The semi soft packet sent to the new base station creates the routing cache for

the mobile host on the new base station. Once set up data packets are then sent to both base stations, after a semi soft delay time period the mobile host begins the usual handover procedure. This method of handover is better than the hard handover but it uses twice as much of resources than hard handover.

VI. CONCLUSION

The next generation of wireless communication systems combines both fixed and wireless facilities. We have to ensure uninterrupted delivery of multimedia service as mobile terminals (MTs) move among different areas anywhere in the world. Mobility management plays an important role for the next generation wireless communication and it is necessary to pay special attention to the design of mobility management procedures. In this concern, we have presented Mobile IP as a solution for next generation wireless system networks, which provides secure, macro and micro mobility protocol. Cellular IP works as a micro mobility solution and can work in conjunction with mobile IP for a complete mobility solution

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[1] G. Fleming et a /, “A Flexible Network Architecture for UMTS,” I€€€ Pers ommun, VOI 5, no 2, Apr 1998, pp 8-1 5 [2] G. Fleming et a /, “A Flexible Network Architecture for UMTS,” I€€€ Pers ommun, VOI 5, no 2, Apr 1998, pp 8-1 5 [3] C. Perkins, D.B. Johnson, “Route Optimization in Mobile IP”, Internet Draft, IETF, November 2000. Work in progress. [4] IETF IP Next Generation Working Group (ipngwg), http://www.ietf.org/html.charters/ipngwg-charter.html. Progress, July 2000. [5] E. Gustafsson, A. Jonsson, C. Perkins “Mobile IP Regional Registration”, Internet Draft, IETF, March 2001. Work in Progress. [6] S. Das, A Misra, P. Agrawal, and S.K. Das, “TeleMIP: Telecommunications Enhanced Mobile IP Architecture for Fast Intra-domain Mobility,” IEEE Personal Communications Magazine, Vol 7, pp. 50-58, Aug. 2000 [7]M. Carli, “Mobile IP and Cellular IP integration for Inter Access Network handoff” 2001

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