Rheinisch-Westfälische Technische Hochschule Aachen Lehrstuhl für Informatik IV Prof. Dr. rer. nat. Otto Spaniol Mobility Management in GPRS Seminar: Data Communication and Distributed System Winter 2003/04 Wichan Threamthrakanpon Matrikelnummer: 244535 Betreuung:Roger Kalden Ericsson Research, Corporate Unit Ericsson Eurolab Deutschland GmbH Table of Contents ABSTRACT ____________________________________________________ 3 1. INTRODUCTION _____________________________________________ 3 2. CONCEPT OF MOBILITY IN MOBILE COMMUNICATION ______ 4 2.1 Mobility Management Framework ______________________________ 4 2.2 GPRS in Mobility Management Framework ________________________________ 5 3. GPRS MOBILITY MANAGEMENT _____________________________ 5 3.1 GPRS System Architecture ____________________________________ 6 3.2 GPRS Session Management ___________________________________ 7 3.2.1 Attach, Detach Procedure ________________________________ 8 3.2.2 PDP Context Activation, Deactivation Procedure _____________ 8 3.3 GPRS Mobility Management __________________________________ 8 3.3.1 State Model ___________________________________________ 9 3.3.2 Location Update _______________________________________ 9 3.3.3 RA Update____________________________________________ 10 3.3.4 Cell Reselection _______________________________________ 11 3.3.5 Paging of GPRS Mobile Station ___________________________ 11 4. USER MOBILITY INVESTIGATION ___________________________ 12 4.1 Investigation by Mathematical Formulation and Analytical Method ____12 4.2 Investigation by Measuring Geographic Position ___________________13 4.3 Investigation by Exploring Trace Data in Cellular Network __________ 18 5. CONCLUSION _______________________________________________ 20 6. REFERENCES _______________________________________________ 21 2 Abstract Mobility management plays a significant role in the new cellular wireless network standard GPRS. GPRS provides a number of functions, such as location update, cell reselection, paging mobile station, etc., to support subscriber mobility. The characterization of different forms of user mobility and their effects on communication traffic are also important in planning, design, and operation of mobile communication network. This paper describes concepts of mobility in mobile communication, the GPRS mobility management and various user mobility investigation techniques. 1. INTRODUCTION The General Packet Radio Service (GPRS) is a step between GSM and 3G cellular networks. GPRS offers faster data transmission via a GSM network up to the maximum speed 171.2 kbps. This new technology makes it possible for users to make telephone calls and transmit data at the same time. (For example, if you have a mobile phone using GPRS, you will be able to simultaneously make calls and receive e-mail messages.) The main benefits of GPRS are that it reserves radio resources only when there is data to send and it reduces reliance on traditional circuit-switched network elements. GPRS can be thought of as an overlay network onto the GSM network because GPRS uses most of existing GSM network elements, plus new network elements, interfaces, and protocols for building a packet-based mobile cellular network. GPRS is the technology that provides packet data access to an existing GSM Networks. It is designed to support an efficient mobile packet network. One of the greatest advantages of GPRS is that it allows a subscriber to access data services at a higher data rate while on the move. Therefore, reliable seamless mobility handling is a significant key requirement for wireless data networks and in order to achieve the quality of service (QoS), the efficient mobility handling algorithm is needed. Consequently the user mobility model, used to predict the movement of subscriber, is used in planning and implementing the mobility handling algorithm. This causes an emerging of several researches in user mobility investigation techniques. The rest of this paper explores the issues of concepts of mobility in mobile communication, the GPRS mobility management and various user mobility investigation techniques. To describe the concept of mobility, a mobility framework will be first introduced and then we analyze how the GPRS mobility is fixed in our framework in section 2. In addition, in section 3 the GPRS mobility management is presented in detail. In section 4, we present various user mobility investigation approaches, such as an investigation by mathematical formulation, by measuring geographic position, and by exploring trace data, including examples and results from the existing papers [4]-[8], and compare the advantage of each approach. 3 2. CONCEPT OF MOBILITY IN MOBILE COMMUNICATION In order to define a complete mobility management solution, we need to define the framework of mobility management. In the Mobility Management in Mobile Internet, S. Uskela [2], the mobility framework has been examined in three different aspects of mobility: use cases, realization, and functionality. They refer to end user’s perception of the provided mobility, and basic procedures that each mobility management technology supports. In this section, mobility framework will be discussed. 2.1 Mobility Management Framework Use Cases S. Uskela [2] has defined the mobility use case from the end-users’ point of view as three different use cases: static, nomadic and continuous mobility. Static mobility is the case that there is no movement at all. Nomadic mobility is the ability to retain access at the intermediate stop and at the destination, for instance, the users use laptops to connect to the internet from different locations. Continuous mobility refers to the model that the users are always reachable and capable to access the network during the movement. The example for the last use case is the use of cellular network which, the users are always connected to the network and reachable while on the move. In the paper On Fundamental Concept of Mobility for Mobile Communication, Jun-Zhao Sun and Jaakko Sauvola [3], the mobility use case is defined further to pervasive mobility. This scenario is known as mobile ad hoc network communication where the mobile hosts without using any pre-existing network infrastructure are free to move randomly. Realization Based on the use cases discussed above, there are two main different realization approaches to realize mobility: personal and device mobility. The former approach focuses on movement of the user while the latter approach focuses on movement of the user’s device [2]. Personal Mobility focuses on providing communication services and ubiquitous network access for users independent of the device they are currently using, for example, the use of SIM card in GSM system. Another interesting aspect of personal mobility is personalizing the operating environment and maintaining the personalization when changing the device. Device Mobility focuses on movement of device and can be realized in different protocol layers: link, network, session and application layer. While using link layer mobility, device’s point of attachment to IP network remains the same, for instance, IEEE 802.11 and GPRS networks can provide link layer mobility. The network layer mobility has to be provided by the IP routing, there fore Mobile IP (MIP), solution for IPv4 and IPv6, supports the network layer mobility. For session layer mobility, the application can be running on top of session without awareness of the movement. Function In general there are a numbers of functions used in the mobility management schemes and since there is some variation in different technologies, these functions can be variant. As a result, only the key functions are discussed here. 4 Registration. Usually this function is used when the mobile device is switch on. The mobile device informs the network that it is ready to start sending and receiving communication data. The registration function also include the process of checking the authentication of the user to use the network. Paging. Normally the network knows the accurate location of the mobile device only when the device is in the state that performs cell updates frequently. If the device is in power saving mode, the paging function is essential in order to retrieve the current cell, the device is located. Location Update. Location update is used to inform the current location of the device to the network. This location update function can be triggered by both movement or timer, for instance, the mobile device updates the current location to the network when it moves into the new location or the timer is expired. Handover. When the device is in dedicated mode, in order to maintain the connection session, handover must be performed when the device move from one coverage area of one access point to another. The length of time which is used to perform handover is critical to maintain the quality of the communication especially in an interactive session. Rerouting. After a handover procedure, the traffic path in the network often is sub optimal. Then rerouting may be done after the handover to optimize the traffic path. Since the handover is done, the rerouting process is no more time-critical. 2.2 GPRS in Mobility Management Framework The General Packet Radio Service (GPRS) is a new non-voice value added service that allows information to be sent and received across a mobile telephone network. GPRS is an enhancement over the GSM by adding some nodes into the network to provide the packet switch services. In our framework, GPRS is mapped