Fahd A. Batayneh Page 1 of 21 [email protected] Location Management in Wireless Data Networks Abstract Location Management (LM) has become a diverse and broad field for research, and Location Based Services (LBS) are the “Application Layer” of LM. Research areas for LM include LM in Wireless Networks, Ad-hoc networks, WiFi, 802.15, WiMax, and mostly; cellular networks. The integration of IP (especially IPv6) into LM is the hottest topic of today. This survey paper tends to introduce the reader to the latest research on LM in Wireless Data Networks and explore the various technologies under research and construction. Table of Contents 1. Introduction 2. Location Based Services 2.1 Classification of LBSs 2.2 Applications of LBSs 2.3 LBSs in Research 3. Location Tracking and Updating (Registration) 3.1 Static Update Strategies 3.2 Dynamic Update Strategies 4. Location Finding (Paging) 4.1 Paging Schemes 4.2 Intelligent Paging Schemes 4.3 Intersystem Paging 4.4 IP Micro-mobility and Paging 5. General Issues in LM 5.1 Security 5.2 Group Based LM 5.3 Distributed LM 6. LM in Wireless Networks 6.1 Heterogeneous Wireless Networks 6.2 Replication in Wireless Networks 7. LM in Wireless Mobile Ad-hoc Networks 7.1 Soft LM Schemes 7.2 Hard LM Schemes 7.3 The use of TCP in MANETs 8. LM in WiFi (802.11) 9. LM in Bluetooth 10. LM and IP Summary References List of AcronymsFahd A. Batayneh Page 2 of 21 [email protected] 1. Introduction Mobile wireless devices with wireless connection facilities are changing the way people think about the use of computing and communication. These wireless devices can communicate with one another even though the user is mobile. People carrying a mobile computer will be able to access information regardless of the time and their current position. Over 100 million wireless Internet users were recorded as of September 2003 with the majority in Japan and Korea, while fast growth rates were recorded in Europe. Significant growth is expected in specialized mobile services such as driving directions, traffic report, tour guides, and commerce services such as mobile shopping. However, Location Management (LM) will be an important issue in these situations because wireless devices can change location while connected to a wireless network. New strategies must be introduced to deal with the dynamic changes of a mobile device’s network address. The ability to change locations while connected to the network creates a dynamic environment. This means that data, which is static for stationary computing, becomes dynamic for mobile computing. There are a few questions that must be answered when looking at a LM scheme. What happens when a mobile user changes location? Who should know about the change? How can you contact a mobile host? Should you search the whole network or does anyone know about the mobile users moves? LM schemes are essentially based on users’ mobility and incoming call rate characteristics. The main task of LM is to keep track of a users’ location all the time while operating and on the move so that incoming messages (calls) can be routed to the intended recipient. LM consists mainly of: 1. Location Tracking and Updating (Registration): A process in which an end-point initiates a change in the Location Database according to its new location. This procedure allows the main system to keep track of a user’s location so that for example an incoming call could be forwarded to the intended mobile user when a call exists or maybe bring a user’s profile near to its current location so that it could provide a user with his/her subscribed services. 2. Location Finding (Paging): The process of which the network initiates a query for an end-point’s location. This process is implemented by the system sending beacons to all cells so that one of the cells could locate the user. This might also result in an update to the location register. As we can see, the main difference between location tracking and paging is in who initiates the change. While location tracking is initiated by a mobile host, paging is initiated by the base system. Most LM techniques use a combination of location tracking and location finding to select the best trade-off between the update overhead and the paging delay. LM methods are classified into two groups: 1. Group one includes methods based on network architecture and algorithms, mainly on processing capabilities of the system. 2. Group two includes methods based on learning processes (i.e. which require the collection of statistics on subscribers’ mobility behavior). This method emphasizes the information capabilities of the network. For LM purposes, a wireless network usually consists of Location Areas (LAs) and Paging Areas (PAs). While LAs are a set of areas over which location updates take place, PAs are a set of areas over which paging updates take place. Usually, LAs and PAs are contiguous, but that’s not the case always. In addition, a LA usually contains several PAs, see Figure 1.1.Fahd A. Batayneh Page 3 of 21 [email protected] As the size of the LA increases, the cost of paging will also increase as more PAs are to be paged to find a called mobile host. On the other hand, reducing the size of a LA will increase the number of crossings per unit time. Hence, the cost of location update or registration will rise. Both paging and location updates consume scarce resources like wireless network bandwidth and power of mobile hosts. Each has a significant cost associated with it. So, LA planning is to be based on a criterion that guarantees the total signaling load, which comprises paging and registration, is kept under tolerable limits. Therefore, it is characterized by the trade-off between the number of location updates and the amount of paging signaling that the wireless network has to deal with. Having discussed briefly about LM, updating, and paging, sections 3 and 4 go more deep into discussing updating and paging in more detail. The next section talks briefly about Location Based Services (LBS) and their impact on LM. The aim of the next section is to provide the reader with an overview as to why LM is necessary. 2. Location Based Services Although Location Based Services (LBS) have been an issue in the field of mobile
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