Telecommunication Sector

1- Introduction

     1- Telephon

     2- Mobile phone or cell phone

     3- Internet

     4- Television and Radio

     5- Other Communication

1- Introduction

 

The telecommunications sector is considered one of the most advanced sectors compared to others.

Communication methods began with emitting sounds, codes, or sending optical signals, such as smoke signals. Then, with the advancement of electricity, communication evolved. The telegraph is considered the first manifestation of modern communication. Subsequently, communication technologies have evolved, and there are several forms of communication that play a significant role in our lives:

  1. Telephone
  2. Mobile phone or cell phone
  3. Internet
  4. Radio and Television
  5. Other forms of communication
 
 

1-Telephone

The telephone network is called the Public Switched Telephone Network (PSTN) or the Public Telephone Network.

The principle of operation of the telephone network is Circuit Switching, meaning that during a phone call, the caller and the receiver are connected through an electrical circuit for the entire duration of the call.

The PSTN consists of three main elements:

  1. Subscriber telephones: Regular home telephones.
  2. Transmission cables (copper cables or optical fibers): Connecting telephones to switches.
  3. Switches: Controllers of the network, connecting calls and completing circuits.

Subscriber telephones are connected to switches via transmission cables at Central Offices or Central Offices.

Central Offices are interconnected with each other hierarchically through transmission cables in usually five stages (classes), where each office represents a certain area, and the highest stage represents a larger area.

When a caller dials a number on the phone to call, the phone sends a signal to the Central Office. Central Offices communicate with each other through signaling to determine the location of the dialed number and to determine the routing for the call.

Based on the number sequence, the call is routed to the destination, such as the area code and neighborhood. When reaching the intended recipient, the phone rings.

The PSTN is interconnected with other networks, such as cellular networks, the internet, other carriers, and international networks, usually with a tariff for this connection based on specific standards through a point called Network Access.

In the current situation, the telephone network has evolved significantly from the past, and data is transmitted through packet switching using VoIP protocol, similar to internet data. Voice is converted from analog to digital, and the same internet network and transmission method are used to deliver it to the recipient. Unlike PSTN, a single channel is not secured.



2-Mobile phone or cell phone

The principle of operation of the cellular phone network is WWANs – Wireless Wide Area Networks.

The cellular phone network (1st generation) consists of three main elements:

  1. Mobile phone or cell phone.

  2. Base Transceiver Station (BTS): It consists of towers distributed in a cellular pattern, with each tower covering or responsible for a specific wireless area. These towers are connected via wire to the Mobile Telephone Switching Office (MTSO) and the phone.

  3. Mobile Telephone Switching Office (MTSO): Its function is similar to that of a switching office in the telephone network – it switches mobile calls with each other and also connects them with the telephone network.

During transmission and reception, the mobile phone converts sound into waves, then performs modulation with a carrier wave of high frequency, and sends it through the mobile phone’s receiver as an electromagnetic wave. The reverse process occurs when receiving sound.

Periodically, the tower checks the location of the mobile phone within its coverage area – in a cellular form – by sending periodic signals and constantly communicating.

When connecting to another mobile device, access is achieved through the tower that covers the mobile phone, and then the Mobile Telephone Switching Office connects the two devices during the call.

The cellular phone network has undergone several developments, starting from the 1st generation (1G), then the 2nd generation (2G), then the 3rd generation (3G), then the 4th generation (4G), and currently reaching the 5th generation (5G). During this period, many elements have been added to the network to improve it, and many standards have been added and developed to increase the network’s capacity and optimize frequency usage.

 

 

3-Internet

The principle of operation of the Internet is Packet Switching. In other words, the Internet can be likened to a postal network, but instead of transporting parcels, it transports data. Instead of your home address, your IP address is used as your address on the Internet.

The Internet consists of three main elements:

  1. Computer: Any device capable of connecting to the network with an IP address.

  2. Router: Selects the path to transmit data and forwards it between the computer and the server.

  3. Server: Acts as a memory for storing websites and is located within a data center. Websites also have IP addresses.

  4. Transmission cables: These cables connect the computer, router, and server.

 

A website’s IP address is its actual address, but the URL or link is used for convenience. When you type a website’s URL into the browser’s address bar, your device first goes to a server called DNS, which records the IP address for that website. Then, it sends a request to the location where the content of the website is stored inside the server. Subsequently, a response is sent back by the website with the content, whether it’s a page, image, or video, and thus the interaction proceeds with a request and then a response.

During transmission between your device and the website, data takes the form of packets, similar to envelopes in mail, containing various data including addresses, and the data is divided into several parts, each part following a different path.

During this transmission process, data is sent through cables and routers distributed in the Internet network, performing a process called Packet Switching to push the data to the next point. The router’s function is similar to that of postal workers, as it forwards the Packet Switched data within the network sequentially from point to point until it reaches the destination.

There are several protocols to organize the Internet, with the most important being the IP/UDP protocol.

 

 

4-Radio and Television

1 – Radio

The radio network consists of:

  1. Radio station: Where radio programs are recorded.
  2. Broadcasting tower: Transmits what is recorded in the radio station.
  3. Radio receiver: Receives and filters the broadcast for listening.

When sound is recorded inside the radio station (such as morning radio shows), the sound is converted into an analog electrical waveform. This electrical wave is then modulated with a carrier wave of a frequency representing the channel’s frequency. The tower then broadcasts this waveform wirelessly as electromagnetic waves.

The radio (such as a car radio) receives the channel’s wave along with other channels through the antenna. It then converts the electromagnetic waves back into electrical oscillations.

During radio tuning, the channel frequency is selected by filtering the carrier wave and accessing the channel’s broadcast.

2 – Television

  1. Terrestrial Television: Similar to radio, but there is another wave, the image wave, which is included and synchronized with the sound wave for reception and conversion from an image wave to an image. In the past, old TV stations had analog waves, but currently, most of them are digital, or channels have switched to satellite stations.

  2. Satellite Television

It consists of the following elements:

  1. Television stations or channels that broadcast television programs (Programming Source) connected to the broadcast center.

  2. Broadcast center: Broadcast centers gather television stations and then send them to the satellite.

  3. Geostationary satellites: Satellites orbit the earth at the same speed so that they remain stationary above a certain area (such as the Middle East and Africa).

After recording a television program through television stations, the data is sent to broadcast centers, where the data is compressed into MPEG-2 format, converted into digital form, and encrypted. Then, the data packet is uploaded (Uplink) or transmitted to the satellite wirelessly (using an electromagnetic carrier wave).

The satellite receives the data through the transponder.

Then, the satellite broadcasts the data down (Downlink) in a specific direction and angle.

On the ground, the dish or satellite dish at homes receives these waves by directing the dish at a specific angle of the satellite’s broadcast.

Then, it converts them into electrical oscillations and transmits them through the cable to the receiver.

The receiver decompresses and then decodes the data, converting the digital oscillation into analog for display on the television.

There are two types of satellite TV:

  1. Direct To Home (DTH), which is the most common and contains multiple channels, including free-to-air channels.
  2. Direct Broadcast Satellite (DBS), which is usually subscription-based and provides higher quality with a specific range.
 

5- Other Communication

Different communication networks are used in various sectors such as the military, banking, and aviation. However, the network is private to maintain information confidentiality and speed. The same principles and methods of transmission used in ordinary communication methods above are used.