Partially Overlapping Super Location Area (POSLA): An Efficient Scheme for Location Management in PCS Networks Koteswararao Kondepu 1 , Chiranjeev Kumar 2 , Rajeev Tripathi 3 1 Tata Consultancy Services (TCS), Hyderabad, India, Email: koteswararao.kondepu@tcs.com 2 Department of computer Science & Engineering, Indian school of Mines University, Dhanbad, India Email: k_chiranjeev@yahoo.co.uk 3 Department of Electronics & Communication Engineering, Motilal Nehru National Institute of Technology, Allahabad, India. Email: rt@mnnit.ac.in Abstract A Partially Overlapping Super Location Area (POSLA) Scheme is suggested to overcome the varying updation problem of Overlapping Super Location Area (OSLA) Scheme. In this scheme, the LA is partially overlapped by its surrounding LAs and the location updates will be done based on the minimum distance from the center cell. The suggested scheme, POSLA, shows the reduction in the location update cost as compared to OSLA scheme. Keywords: Public Switched Telephone Network (PSTN), Location Area (LA), Location Area Identifier (LAI), Super Location Area (SLA), Overlapped Super Location Area (OSLA), Partially Overlapped Super Location Area (POSLA) 1. Introduction Personal communication service (PCS) is one of the standard widely used in location management [3-6] among existing standards. The typical architecture of the PCS network is shown in Figure 1.1. The architecture has two database HLR and VLR. The mobile switching center (MSC) associated with a specific VLR is in charge of several base station controllers (BSCs), lower control entities which in turn control several base stations (BSs). The MSCs are connected to the backbone wired network such as public switched telephone network (PSTN). The network coverage area is divided into smaller cell clusters called location areas (LAs). SS7: Signaling System 7 Figure 1.1 The Cellular Architecture in PCS Network The visitor location register (VLR) stores temporarily the service profile of the MT roaming in the corresponding LA. The home location register (HLR) stores permanently the user profile and points to the VLR associated with the LA where the user is currently located. Each user is assigned unambiguously to one HLR, although there could be several physical HLRs. A base station periodically broadcasts its location area identifier (LAI), which is unique for each LA. When a MT enters a new LA, it receives a different LAI. Then, the MT sends a registration message to a new VLR. The new VLR sends a registration message to the HLR. Then the HLR sends a registration cancellation message to the old VLR and sends a registration acknowledge message to the new VLR. Now the HLR points the new VLR that has service profile and location information of the MT. This procedure is called the location update. When a call to a PCS user is detected, the corresponding HLR is queried. Once the HLR corresponding to the MT has been queried, the VLR/MSC currently serving the MT is known. Then paging is done through the LA where the MT is currently located. The location update cost consists of the update cost of HLR and that of VLR. Since the HLR is connected to many VLRs as shown in Figure 1.1, reducing the traffic with the HLR becomes an important issue to reduce the whole location update costs. This paper proposes to employ a hierarchical structure to reduce the location update cost of the HLR. In the PCS system, both VLR and HLR are updated whenever a MT enters a new LA. So the location updates tend to occur frequently in the boundary cells of LAs. This is the drawback in PCS system. In [1], the author has proposed a hierarchical structure to reduce the location update cost. The rest of the paper is organized as follows. Section 2 describes the related work. Section 3 includes proposed POSLA scheme. Finally, Section 5 presents conclusions. 978-1-4244-1645-5/08/$25.00 ©2008 IEEE 2182