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Computer Engineering Articles
Page 12 of 36
The Local Loop
In a telephone system, the local loop is a two-wire connection between the subscriber's house and the end office of the telephone company. It is commonly referred to as the "last mile" of the telephone network, representing the final physical connection that delivers telecommunication services to end users. The loop may run from 1 km to as far as 10 km depending on the geographic location and infrastructure. Local Loop in Telephone Network Subscriber Home/Office Central ...
Read MoreTelephone Modems
A modem is an abbreviation of "modulator demodulator". It is a network device that modulates digital information or bits into analog signals for transmission at the sending end, and demodulates the analog signals back to bits at the receiving end. Telephone modems enable data communication between two computers over voice-grade telephone lines. Purpose and Usage Computers are digital devices that need to communicate over the analog local loops of telephone networks. There is a need to convert digital bits to analog signals for transmission over physical telephone channels, and conversely convert analog signals back to computer-understandable bits. A ...
Read MoreTrunks and Multiplexing
A trunk is a high-capacity communication channel that connects switching centers, forming the backbone of telecommunication networks. Trunks are designed to carry large volumes of voice and data traffic simultaneously over long distances using multiplexing techniques. Unlike local loops that connect individual subscribers to the nearest switching office, trunks handle the bulk transmission of aggregated traffic between network nodes. They represent the core infrastructure that enables telecommunications networks to scale efficiently. Trunk Network Architecture End Office A (Local Switch) ...
Read MoreDigitizing Voice Signals
Digitizing voice signals is the process of converting analog voice communications into digital form for transmission over modern telephone networks. This transformation enables efficient multiplexing, improved signal quality, and integration with digital communication systems. Analog Telephone Cores Early telephone networks operated with analog cores that transmitted voice signals in their original analog form. These systems used Frequency Division Multiplexing (FDM) to combine multiple voice channels over a single transmission line. Group formation − Twelve individual calls were multiplexed into a basic group Supergroup formation − Five groups were further multiplexed into a supergroup ...
Read MorePulse Code Modulation
Pulse Code Modulation (PCM) is a technique for digitally representing analog signals. It takes samples of the amplitude of the analog signal at regular intervals and converts them to binary data. PCM is widely used by codecs in telephone networks to convert analog signals in local loops to digital signals in the trunks, and performs reverse conversion at the receivers' end. How PCM Works PCM operates through three fundamental steps: sampling, quantization, and encoding. These processes convert continuous analog signals into discrete digital representations that can be transmitted and stored efficiently. PCM Process ...
Read MoreThe Mobile Telephone System
Mobile telephone service (MTS) connects mobile radio telephones with other networks like public switched telephone networks (PSTN), other mobile telephones and communication systems like Internet. This system enables seamless communication between mobile devices and fixed networks worldwide. Basic Mobile Communications System Mobile phones and other mobile devices, called mobile stations, are connected to base stations. Communication between the mobile stations and the base stations are done by wireless radio signals, which may be both data signals and voice signals. Each base station has a coverage area around it, such that mobile stations within this area can connect ...
Read MoreFirst-Generation (1G) Mobile Phones
First-generation (1G) mobile phones marked the beginning of wireless cellular technology, introducing the world's first commercial mobile communication system. It was an analog telecommunications system that revolutionized personal communication by making voice calls possible from virtually anywhere within network coverage. 1G technology operated from 1979 to the mid-1980s, establishing the foundation for all modern mobile communication systems that followed. 1G Cellular Network Architecture Cell A Cell B Cell C BS ...
Read MoreImproved Mobile Telephone System
The Improved Mobile Telephone System (IMTS) was a pre-cellular radio communication system that connected mobile devices to the Public Switched Telephone Network (PSTN). Introduced in 1964, IMTS served as the wireless equivalent of landline dial-up telephones and represented a significant advancement over its predecessor, the Mobile Telephone System (MTS). IMTS operated as a centralized system where a single high-power transmitter served mobile users within its coverage area, typically spanning 25-50 miles radius depending on terrain and transmitter placement. IMTS System Architecture IMTS Base Station ...
Read MoreAdvanced Mobile Phone System
The Advanced Mobile Phone System (AMPS) was a standard for analog cellular phone systems developed by Bell Labs and officially introduced by AT&T in 1983. It was the first widespread cellular technology in North America and became the foundation for modern mobile communications. Key Features of AMPS Analog technology − Based on the initial electromagnetic spectrum allocation for cellular service by the Federal Communications Commission (FCC). Frequency Division Multiple Access (FDMA) − Allows multiple simultaneous conversations by assigning different frequency channels to each user. Frequency allocation − Operates within the 800 and ...
Read MoreFrequency Division Duplex
Frequency Division Duplex (FDD) is a communication technique where two parties can communicate with each other in both directions simultaneously by using separate frequency bands for transmitting and receiving data. Since FDD uses different frequency bands for upstream data and downstream data, the sending and receiving signals do not interfere with each other. This separation allows for continuous, full-duplex communication without the need for time-based coordination between transmitter and receiver. Frequency Division Duplex (FDD) Base Station ...
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