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TTM4133: Mobile Networks and Services

# Preface This compendium aims to explain the most important concepts in the subject. The content is mostly based onthe lecture slides and the book: "From GSM to LTE-Advanced PRO and 5G". The course focuses on: GSM, GPRS, UMTS, LTE, SIP & IMS, 5G and Over the Top Services. The compendium is structured around explaining each of these items in detail. Everyone is allowed to edit this compendium, if you see any errors feel free to correct them.

# GSM~~The Global System for Mobile Communications (GSM) is a second generation (2G) standard for mobile networks~~

## GSM Subsystems GSM has three different subsystems:

- __The Network Subsystem (NSS)__, also called the "core network" contains all nodes and functionalities that are necessary for switching of calls, for subscriber management and mobility management. - __The Base Station Subsystem (BSS)__, also called the "radio network" contains all nodes and functionalities that are necessay to wirelessly connect mobile subscribers over the radio interface to the network. - __The Intelligent Netowk Subsystem (IN)__ comprises SCP databases that add optional functionality to the network. For example prepaid service, SMS mesages and data services via GPRS and UMTS. ## The Network Subsystem The most important responsibilities of the NSS are call establishment, call control and routing of calls between different fixed and mobile switching centers and other networks. I~~n the early~~ t is also responsible for subscriber management. ![](https://s3-eu-west-1.amazonaws.com/wikipendium-public/15613039580~~s, a group was formed by the European Telecommunications Standards Institute (ETSI~~xda340.jpg) to develop a digital mobile communication system. Aptly named Groupe Speciale Mobile (GSM), its main task was to develop a single, consistent network for all of Europe and come up with a better and more efficient technical solution for wireless communication. The GSM standard operates on three different carrier frequencies: the 900 MHz band, which was used by the original GSM system; the 1800 MHz band, which was added to support the swelling number of subscribers and the 1900 MHz frequency, which is used mainly in the U.S. Although GSM is based on the time division multiple access (TDMA) system, its technology uses digital signaling and speech channels and is considered a second generation (2G) mobile phone system.

## Circuit-Switched Data Transmission GSM was initally designed as a circuit switched network that establishes a direct and exclusive connection between two users on every interface between all network nodes of the system. ## The Signalling System Number 7 Signaling System No.7 (SS-7) is a telecommunications signaling architecture traditionally used for the set up and tear down of telephone calls. It has a robust protocol stack that uses out-of-band signaling to communicate between elements of the public switched telephone network (PSTN). In recent years it has been superseded by the Diameter signaling protocol on all-IP networks. The SS-7 standard defines three basic types of network nodes: - Service Switching Points (SSPs): Are switching centers that are more generally reffered to as network elements and that are able to establish, transport or forward voice and data connections. - Service Control Points (SCPs): Are databases and application software that can influence call establishment of a connection. - Signalling Transfer Points (STPs): Are responsible for the forwarding of signalling messages between SSPs and SCPs as not all network nodes have a dedicated link to all other nodes in the network.