Mobile Network Components and Operation

Summary

This video explains the key components of a mobile network, starting with the handset, which includes a SIM card that stores essential data such as subscriber identity and encryption keys. The network operates through base stations, which consist of transceivers, antennas, and physical support, communicating with mobile switches via a backhaul system. The mobile switch manages user locations, authenticates services, and connects calls to the public network. Additionally, the video covers how base stations handle call handoffs when users move between coverage areas, ensuring seamless communication within the mobile network.

Takeaways

• 😀 A mobile network consists of several components, including a handset, base station, and mobile switch.
• 😀 Handsets, or smartphones, include features like a speaker, microphone, codec, modem, battery, and a removable SIM card.
• 😀 The SIM card contains critical information, including the International Mobile Subscriber Identity (IMSI), encryption key pair, and the Location Area Identifier (LAI).
• 😀 The SIM card can be transferred between phones, allowing the network to recognize the user on a different device.
• 😀 Base stations have three main components: the Base Station Transceiver (BTS), antennas, and the physical support structure for the antennas.
• 😀 Antennas at the base station convert electrical signals into electromagnetic waves, with common designs including omni and flat panel antennas.
• 😀 Base station antennas were traditionally placed on tall towers, but with smaller cells and lower power in newer generations, antennas are now often placed on buildings or other structures.
• 😀 The base station is connected to a mobile switch via backhaul, which can be done through fiber or point-to-point radio links.
• 😀 The mobile switch keeps track of users and their locations using a Location Register, which stores the last registered base station for each phone.
• 😀 When a call is made to a mobile phone, the mobile switch checks the location register, sends a page to the last registered base station, and establishes a connection with the phone if it’s still active.
• 😀 Mobile phone communication involves multiple steps, including airlink communication, backhaul, and connections to the public telephone network, allowing calls to landlines and other networks.
• 😀 When a user moves away from a base station, the mobile switch manages a handoff to a new base station to maintain the call, sometimes with a brief communication drop, depending on the technology used.

Q & A

What are the main components of a mobile network's terminal?

A mobile network terminal includes a speaker, microphone, codec for digitizing speech, modem, antenna, battery, keypad, screen, and the removable SIM card.

What is stored on a SIM card and why is it important?

A SIM card stores critical information such as the International Mobile Subscriber Identity (IMSI), part of an encryption key pair for authentication, and the location area identifier which helps in tracking the phone's last known base station.

What is the purpose of the location area identifier on the SIM card?

The location area identifier helps the mobile switch determine which base station the phone last communicated with, allowing the switch to locate the user for incoming calls.

How does the base station work in a mobile network?

The base station consists of three main components: the base station transceiver (BTS), antennas, and physical support for the antennas. The BTS handles radio communication, antennas transmit electromagnetic waves, and the physical support holds the antennas in place.

What is the difference between an omni antenna and a flat panel antenna?

An omni antenna radiates energy in all directions, while a flat panel antenna emits energy in a shaped wedge, covering a specific portion of the surrounding area, which increases network capacity.

What is the role of the backhaul in a mobile network?

The backhaul is the connection that links the base station to the mobile switch. This can be implemented using fiber optics or point-to-point radio links if fiber is not available.

What happens when a phone first powers on in a mobile network?

When the phone powers on, it transmits its IMSI and other data on predefined radio frequencies. The mobile switch receives this data, authenticates the phone, checks for payment, and allows the phone to connect to the network if everything is correct.

How does a mobile switch handle a phone call from a landline?

When a call is made from a landline, it travels through various systems to reach the mobile switch, which then looks up the phone's last location in the location register. The mobile switch pages the base station that the phone is closest to, and the phone responds to start the communication.

What is handoff in a mobile network, and how does it work?

Handoff is the process where a mobile switch transfers an ongoing call from one base station to another as the user moves. This can involve a brief period of dropped communication or, with advanced technologies, seamless handoff without interruption.

How does a mobile switch connect a mobile network to other networks?

The mobile switch connects to other networks, such as landline systems or other cellular networks, typically using fiber optics to facilitate communication between different networks.