How the cellular network works? - GSM Architecture | 1G & 2G | Arun

Summary

This video explains the evolution of mobile network technologies, starting with 1G, the first generation, which was primarily for voice services with analog modulation. It then covers 2G GSM, which introduced digital modulation, SIM cards, and data services. The video breaks down the architecture of the GSM network into four key subsystems: Mobile Station, Base Station Subsystem, Network Switching Subsystem, and Operation Support Subsystem. It explores the components of each subsystem, such as the Mobile Switching Center and the Home Location Register, and concludes by demonstrating the call routing process in a simplified GSM system.

Takeaways

• 😀 1G, introduced in the 1980s, was the first-generation cellular standard that supported only voice services and used analog modulation with FDMA.
• 😀 GSM, or Global System for Mobile Communication, was introduced in 1991 as the second-generation cellular standard supporting both voice and data services with digital modulation and TDMA.
• 😀 GSM handsets were cheaper, smaller, and the first to introduce SIM cards, which are detachable smart cards containing IMSI numbers.
• 😀 The GSM system uses GMSK digital modulation and TDMA, with data speeds around 14.4 kilobytes per second.
• 😀 In India, GSM operates on 900 MHz and 1800 MHz frequency bands.
• 😀 The GSM architecture consists of four main subsystems: Mobile Station, Base Station Subsystem, Network Switching Subsystem, and Operation Support Subsystem.
• 😀 The Mobile Station consists of two components: Mobile Equipment (IMEI number) and SIM (IMSI number) that allow users to send and receive calls.
• 😀 The Base Station Subsystem includes the Base Transceiver System (BTS) for sending and receiving signals and the Base Station Controller for managing radio channels and handovers.
• 😀 The Network Switching Subsystem's key components are the Mobile Switching Center (MSC), Home Location Register (HLR), Visitor Location Register (VLR), Equipment Identity Register (EIR), and Authentication Center (AUC).
• 😀 The GSM signal flow involves the Mobile Station sending a signal to the Base Station Subsystem, which then routes it to the Network Switching Subsystem and finally to an external wired network like PSDN or ISDN.

Q & A

What is 1G and when was it introduced?

1G is the first generation cellular standard, introduced in the 1980s. It is known by different names like AMPS, MTS, and IMTS and primarily supported voice services with analog modulation and FDMA.

What were the main limitations of 1G technology?

The main limitations of 1G included bulkier handsets, analog modulation, limited coverage, and the inability to support data services.

What advancements did GSM bring with the introduction of 2G?

GSM, a second-generation cellular standard introduced in 1991, supported both voice and data services. It replaced analog signals with digital modulation using TDMA, and also introduced SIM cards for mobile identification.

How does GSM differ from 1G in terms of technology and functionality?

GSM uses digital modulation with TDMA, unlike 1G's analog modulation and FDMA. It supports both voice and data services, introduces SIM cards for mobile identification, and provides better efficiency, smaller handsets, and higher data speeds.

What is the GSM architecture and its components?

The GSM architecture consists of four subsystems: Mobile Station (MS), Base Station Subsystem (BSS), Network Switching Subsystem (NSS), and Operation Support Subsystem (OSS). These subsystems manage communication, routing, and network maintenance.

What are the key components of the Mobile Station in GSM?

The Mobile Station includes Mobile Equipment (IMEI) and the Subscriber Identity Module (SIM), which stores the IMSI number and allows the user to send and receive calls.

What is the role of the Base Station Subsystem (BSS) in GSM?

The BSS is responsible for communication between mobile stations and the network. It includes the Base Transceiver Station (BTS) which sends and receives signals, and the Base Station Controller (BSC) which manages BTSs, allocates radio channels, and handles handovers.

What are the components of the Network Switching Subsystem (NSS) in GSM?

The NSS consists of five main components: Mobile Switching Center (MSC), Home Location Register (HLR), Visitor Location Register (VLR), Equipment Identity Register (EIR), and Authentication Center (AC). These components manage call routing, user location, and security.

How does the Visitor Location Register (VLR) work in GSM?

The VLR stores local data of users who are visiting a different network area. For example, when a user moves from Chennai to Delhi, the VLR in Delhi manages the user's location while the HLR in Chennai holds their home network details.

What is the process of a mobile call in the GSM network?

When a user makes a call, the signal is sent from the mobile to the BTS, which routes it to the MSC. The MSC allocates a radio channel and tracks the user's location. The signal then reaches the telephone network, and the process is reversed on the receiver's end.