Design of Cellular Network and it's working
Areas are divided into hexagonal cells. Each cell having its own tower. Each tower is connected through wires (optical fibre).
Mobile Station (MS) -> Communicating device. It has the IMEI (International Mobile Equipment identity) and SIM (Subscriber Identity Module) card. SIM has IMSI (International Mobile Subscriber identity)
Base Station Subsystem (BSS) -> it is a combination of BTS (Base Transceiver Station) and BSC (Base station Controller).
Base Transceiver Station -> Sends and receive the signal from MS.
Base station controller (BSC) -> Controls the group of the BTS. Handovers from the one BTS to another.
Network switching subsystem (NSS) -> it has five components. The main element is MSC and the others are HLR, VLR, EIR, AUC
Mobile switching centre (MSC) is a centre point of a group of cell towers.
Home MSC -> while getting SIM card, it will be registered in MSC it is home MSC. It knows the status, location and plans.
Foreign MSC-> when moving outside the range of home MSC, the new MSC will serve is foreign MSC.
Each subscriber is allocated a frequency range.
Home Location Register (HLR) -> It has the subscriber’s current location and information.
Visitor Location Register (VLR)-> database for users visiting the location in another domain.
Equipment Identity Register (EIR) -> Contains all valid handsets in the network using IMEI number. Marks IMEI as invalid, if it is stolen.
Authentication Centre (AUC) -> Protected database has a copy of has a copy IMSI number for authentication and encryption task.
Operation Support Subsystem (OSS ) ->provides administration and commercial operation.
Frequency slot distribution -> different frequency slots are carefully allocated to different cell towers.
Multiple access technique -> frequency slot is distributed among all active users.
1G ->where G for Generation. It is allowed the first time to carry a phone without wire. The wireless transmission was in an analogue format so it is easily alterable by the third party. Voice quality is poor. Data speed is 2.4 kbps. It is used FDMA (Frequency Division Multiple Access) techniques, which used the available spectrum in an inefficient way.
2G -> used TDMA (Time Division Multiple Access) or CDMA (Code Division Multiple Access) techniques. Data Speed is 50 kbps. Introduction of data service and SMS.
3G -> is to give higher data transfer speed. It used the WCDMA (Wideband Code Division Multiple Access) techniques, along with increased bandwidth. Data speed is 2 Mbps.
4G -> it gives the data transfer speed of 20 Mbps — 100 Mbps. Higher data transfer rate is possible by the OFD (Orthogonal frequency Division) Multiple access technology and MIMO (Multiple Input Multiple Output) technologies. MIMO Uses multiple receivers and antennas inside both mobile and towers.
5G -> it uses Enhanced MIMO technology and millimetre waves. Data speed is up to 10Gbps. It will give seamless connectivity for IoT such as driverless cars and smart home.
Radio waves are a type of electromagnetic radiation. Radio waves have frequencies as high as 300 gigahertz (GHz) to as low as 30 hertz (Hz). At 300 GHz, the corresponding wavelength is 1 mm. At 30 Hz the corresponding wavelength is 10,000 km (longer than the radius of the Earth).
Working
Microphoneàdigital signal (01001) with help of MEMS sensor and IC à transmitted as an electromagnetic wave (Radio wave)by the antenna (altering the wave characters like frequency) electromagnetic waves are picked up by towers and converted into high-frequency light pulses. This is received by base transceiver (located in the base of the tower) routed to designation tower. And it will produce the electromagnetic waves designation mobile will receive the signal and it will reverse the process. Then we can hear the voice by the speaker.
How Home MSC will know designation BTS
Tower of calling MSC will send the request to designation subscriber’s home MSC and it knows the current location of destination subscriber. And the call request will be forwarded to the current location by destination MSC and tower.
