Roaming in Wireless Networks

Transaction Capabilities Application Part (CCS7 in Wireless Networks)

In modern fixed and wireless networks, unlike the earlier versions, not all the network elements are switches. For example, in GSM, several databases are used that have no switching or routing capabilities of their own. The Transaction Capabilities Application Part (TCAP) provides a mechanism to establish non-circuit-related communication between any two nodes (as long as […]

Brief History of Early Cellular Networks (Global System for Mobile Communication (GSM))

Cellular telephone system, though with limited functionalities, features, and scale of deployment, existed as early as the 1920s. The commercial cellular networks, as we know them today, started in the late 1970s. The growth in mobile communication from then onward is amazing. Within 30 years of introduction, cellular telephony is now so popular that many […]

GSM Overview (Global System for Mobile Communication (GSM))

In 1982, the Conference of European Posts and Telegraphs (CEPT) formed a study group to define and develop a pan-European standard for a mobile telephone system. This group was given the name Groupe Special Mobile (GSM). The main task of this group was to propose a system to overcome inherent issues faced by the analog […]

GSM Offered Services (Global System for Mobile Communication (GSM))

GSM offers a wide range of services, including telephony, emergency calling, data up to 14.4 Kb/s, fax up to 9.6 Kb/s, SMS, and others. In addition, it also offers a rich set of supplementary services. According to ITU specifications, the telecommunication services are categorized into three different types, i.e., bearer services, teleservices, and supplementary services. […]

System Architecture (Global System for Mobile Communication (GSM)) Part 1

A GSM network is a most sophisticated and complex wireless network. It was designed for a purpose from scratch and is neither based on nor compatible with any predecessor technologies. In fact, it is the basis for future wireless networks such as GPRS, EDGE, and 3G. A GSM network comprises several distinct functional entities: ■ […]

System Architecture (Global System for Mobile Communication (GSM)) Part 2

Network switching system The role of the network switching system (NSS) is to set up call connections in a mobile environment. The NSS achieves this by using the following switching and database nodes: ■ Mobile switching center (MSC and gateway MSC) ■ Home location register (HLR) ■ Visitor location register (VLR) ■ Equipment identity register […]

GSM Interfaces and Protocols (Global System for Mobile Communication (GSM)) Part 1

The GSM specifications define the interaction between system components through well-defined interfaces and protocols. Figure 3-11 shows the interfaces between the GSM functional entities. Table 3-3 lists the GSM interfaces. Figure 3-12 shows the protocol architecture used for the exchange of signaling messages on each interface. The protocols are layered according to the OSI Reference […]

GSM Interfaces and Protocols (Global System for Mobile Communication (GSM)) Part 2

Abis interface Abis is the interface between the BSC and the BTS. Figure 3-14 illustrates the protocol stack on the Abis interface. The following sections describe each layer in detail. Physical layer. The physical layer, i.e., Layer 1, consists of a 2-Mb/s PCM30 link. This is based on ITU-T G.703 specifications. APCM30 link consists of […]

GSM Interfaces and Protocols (Global System for Mobile Communication (GSM)) Part 3

A interface The A interface is the interface between the BSC and the MSC. At the physical layer, it uses a 2-Mbps PCM30 link. One or more 64-Kbps timeslots are used to carry signaling information. Typically, more than one 2-Mbps link is required to handle the traffic between the BSC and the MSC. The Base […]

Scenarios (Global System for Mobile Communication (GSM)) Part 1

Mobility management Location update. GSM allows a subscriber to move throughout the coverage area with a capability to make or receive calls. This is possible because the GSM network continuously tracks the movement of a mobile and updates its location all the time. There are three different location-updating scenarios. ■ Attach/initial registration, used when a […]