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Telecom Networks

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  • Difficulty Level : Hard
  • Last Updated : 13 Mar, 2023
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Telecom networks are systems of interconnected communication devices and equipment that enable people to communicate with each other over long distances. These networks use various technologies and protocols to facilitate the transmission of voice, data, and video signals between devices, including smartphones, computers, and other communication devices. Telecom networks play a critical role in modern society, providing essential communication services to individuals, businesses, and organizations. They enable people to communicate with each other across vast distances, enabling global communication and facilitating international trade and commerce.

Telecom networks are made up of various components, including transmission systems, switching systems, and network management systems. These components work together to ensure that communication signals are transmitted and delivered efficiently and securely.

In recent years, telecom networks have evolved significantly, driven by advances in technology and changing communication needs. Modern networks use advanced technologies like 5G, fiber-optic cables, and cloud computing to provide faster, more reliable communication services to users. Telecom networks are essential components of modern communication infrastructure, enabling people to communicate and connect with each other in new and innovative ways.

Telecom networks are mostly used today for wide-area communication. Stringing a wire between every pair of telephones that might want to communicate was not a good long-term strategy. A better idea was to connect all the telephones to a central switching office. There an operator could connect one telephone to another via a switchboard. 

Routing a telephone call: A call is routed up through higher-level switching offices until it reaches a switching office that can reach the destination telephone by connecting with lower-level switching offices, which examine the digits of the telephone number you dialed to make these decisions. 

Connection-Oriented Services – I: A dedicated connection between the endpoints is maintained throughout the session. Usually, this means that the quality of service can be reasonably guaranteed to the extent of the bandwidth for the channel that is established. Message bits arrive in the same order in which they are sent. A traditional telephone circuit is a circuit-switched connection-oriented system. 

Transmission Media in Telephone Systems: In traditional analog telephone systems, the telephone is connected to the local exchange via category 3 UTP cables. This connection is called the local loop. It is typically between 1km and 10km in length. Higher up in the hierarchy, higher bandwidth cables are used to carry multiple telephone calls. This is far cheaper than using separate cables for separate calls. Specifically, digital lines on fiber are used. Analog systems used a technique called frequency division multiplexing (FDM) to do this. 

The local loop: The subscriber handsets are powered by a battery bank in the exchange. With echo suppressors, the transmission is half-duplex. With echo cancellers, it is possible to have full-duplex communication. Since the local loop is still analog, we need modems for sending digital data. Since one bit is used for control purposes, we usually get 56kbps speed. Depending on the line condition, modems may automatically negotiate a lower speed. 

Signaling: Signaling refers to the information exchanges between terminal devices, exchanges, and routers for setting up circuits, termination, billing, advanced network services, etc. In common Channel signaling which is in the band, some of the bits in the frame are used for this purpose, in which SS7 is considered standard. Whether In-band or Out of band, logically the switch controllers may be considered to be an overlay network in the control plane. Out-of-band signaling (CCIS – Common Channel Interoffice Signaling) is more flexible as it allows arbitrarily complex message transfer, as they do not interfere with the regular channel. 

Telecom networks are systems of interconnected communication devices and equipment that allow people to communicate with each other over long distances. 

Some of the key features of telecom networks include:

  • Wide coverage: Telecom networks are designed to provide communication services over a wide area, from local to global coverage. They allow people to communicate across long distances and in remote areas.
  • High capacity: Telecom networks are capable of handling large volumes of traffic, including voice, data, and video. They use various technologies to manage traffic and ensure efficient use of network resources.
  • Reliability: Telecom networks are designed to provide reliable communication services, with high availability and minimal downtime. They use redundancy and backup systems to ensure that communication services are always available.
  • Security: Telecom networks use various security measures to protect communication data and prevent unauthorized access. These measures include encryption, authentication, and firewalls.
  • Flexibility: Telecom networks can be easily customized and adapted to meet different communication needs. They can support different types of communication services, including voice, data, and video, and can be configured to meet specific business requirements.
  • Interconnectivity: Telecom networks are interconnected with other networks, allowing seamless communication between different networks and devices. This interconnectivity enables global communication and allows people to communicate across different platforms and devices.
  • Scalability: Telecom networks can be scaled up or down to meet changing demand for communication services. They can support a growing number of users and devices, and can be expanded as needed to meet future demand.
  • Cost-effectiveness: Telecom networks are designed to provide cost-effective communication services. They use various technologies to optimize network resources and reduce operating costs, while providing high-quality communication services to users.

Control Plane Protocol Stack in SS7: 

  1. Application Service Element (ASE) – Application-level functionality such as interpreting signaling messages. Transaction Capabilities Application Part(TCAP) allows the system to invoke procedure calls on remote machines.  
  2. Message Transfer Part 1 (MTP-1) – it is a physical bit transfer usually on a digital line like E1. One of the main applications of SS7 is Telephone User Part (TUP) which is responsible for setting up voice calls. The TUP interprets dialed digits, routes, reserves resources, maintains accounts, etc. 

Digital Technology in Telephone Networks: Over the past 30 years, much of the traditional analog telephone network has been replaced by digital technology. A device called a codec (coder/decoder) is used to convert analog voice signals into digital information that can be handled by digital technology. The codec is also used to convert the digital signals back into analog voice signals that can be handled by the older analog technology. 

Only the local loop is still analog and this loop can be replaced by Integrated Services Digital Network (ISDN) connections. It was envisaged as an end-to-end digital service. Home users would be connected by the same Cat3 cable. the digital bit streams are time-multiplexed. The system uses Out band signaling and uses the D channel for that. NT1 is a network terminating device which connects to the ISDN exchange on one side and a local passive bus on the other from which up to eight terminal devices can hang. ISDN turned out to be very expensive and obsolete even before the standard was finalized. The vision of broadband ISDN was sought to be realized by ATM. 

Digital Subscriber Loop: The next attempt for converting the analog local loop went in two directions: 

  1. Large users could be serviced by taking fiber to their premises which could terminate on an integrated digital outlet. 
  2. The market for small users was driven by the demand for more bandwidth from the subscriber for Internet connection over the same Cat3 cable.
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