Long Distance Data Transmission Chapter
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Questions and Answers

What is the purpose of retuning equalizers in modems?

  • To increase the transmission speed
  • To decrease power consumption
  • To enhance the security of the data transmission
  • To maintain optimal operating conditions for the modem (correct)

How quickly can the automatic equalizer adjust to line conditions?

  • 60ms to 75ms
  • 15ms to 25ms (correct)
  • 5ms to 10ms
  • 30ms to 50ms

What characteristic distinguishes synchronous modems from asynchronous modems?

  • Synchronous modems require less power
  • Synchronous modems do not transmit data in blocks
  • Synchronous modems operate with a clock signal (correct)
  • Synchronous modems are slower in data transmission

What does the term 'Split System Modem' (SSM) refer to?

<p>A modem that can split the channel for multiple consumers (A)</p> Signup and view all the answers

Why do digital signals distort when transmitted over analog media?

<p>Because analog media are not designed for digital signals (A)</p> Signup and view all the answers

What type of signals are used in digital communication over telephone lines?

<p>Square waves (C)</p> Signup and view all the answers

What is the primary characteristic of asymmetric DSL (ADSL) in terms of data transmission rates?

<p>Higher download speed than upload speed (D)</p> Signup and view all the answers

What is typically the responsibility of the data source in synchronous data transmission?

<p>Assembling blocks into frames (D)</p> Signup and view all the answers

Which of the following statements is true about DSL technology?

<p>DSL allows high-speed internet access over existing local loops. (D)</p> Signup and view all the answers

What limits the bandwidth of the local loop to 4 KHz for ADSL?

<p>The filter installed at the end office of the telephone company (B)</p> Signup and view all the answers

What is the typical frequency range used by telephone lines for data communication?

<p>300 Hz to 3300 Hz (B)</p> Signup and view all the answers

Which of the following factors is NOT mentioned as affecting the bandwidth of ADSL?

<p>Geographical terrain (D)</p> Signup and view all the answers

What is the maximum theoretical bandwidth capability of the twisted-pair local loop used by ADSL?

<p>1.1 MHz (C)</p> Signup and view all the answers

What is the primary function of a modem?

<p>To convert digital data into analog signals for transmission (C)</p> Signup and view all the answers

Why was the PSTN originally designed?

<p>To handle only low frequency analog voice signals (C)</p> Signup and view all the answers

Which DSL variation is specifically designed for business customers needing more symmetrical bandwidth?

<p>SDSL (A)</p> Signup and view all the answers

What is the role of the receiving modem in a data transmission?

<p>To demodulate analog signals back to digital data (A)</p> Signup and view all the answers

What primarily differentiates the various DSL technologies like ADSL, VDSL, HDSL, and SDSL?

<p>The first letter representing their functionality (C)</p> Signup and view all the answers

Why is ADSL not suitable for business customers?

<p>It has an uneven bandwidth distribution not favorable for upload needs. (A)</p> Signup and view all the answers

What does the acronym 'ASCII' stand for?

<p>American Standard Code for Information Interchange (A)</p> Signup and view all the answers

Which term best describes the process of converting digital data into analog signals in a modem?

<p>Modulating (A)</p> Signup and view all the answers

What coding system is utilized by modems similar to Morse code?

<p>ASCII code (C)</p> Signup and view all the answers

What type of signals did the PSTN originally transmit?

<p>Low frequency analog voice signals (C)</p> Signup and view all the answers

What is a key feature of modems in relation to the telephone network?

<p>Modems change digital data into analog signals compatible with the telephone network (A)</p> Signup and view all the answers

What is the purpose of the adaptive technology used in ADSL?

<p>To test the line condition and adjust data rate dynamically. (B)</p> Signup and view all the answers

How many channels are typically used for upstream data transfer in ADSL?

<p>25 channels for data and control. (C)</p> Signup and view all the answers

What modulation technique is considered standard for ADSL?

<p>Discrete Multi tone Technique (DMT) (C)</p> Signup and view all the answers

What is the maximum bandwidth achievable in the upstream direction of ADSL?

<p>1.44 Mbps (B)</p> Signup and view all the answers

What is reserved for voice communication in ADSL's channel allocation?

<p>Channel 0 (C)</p> Signup and view all the answers

What happens to the data rate in ADSL under noisy conditions?

<p>It usually drops below the potential maximum data rate. (D)</p> Signup and view all the answers

Which of the following channels are not used in ADSL to provide a gap between voice and data communications?

<p>Channels 1 to 5 (D)</p> Signup and view all the answers

What is the typical channel bandwidth used in ADSL?

<p>4.312 KHz (C)</p> Signup and view all the answers

What is the primary function of the ADSL modem?

<p>To modulate and demodulate data using DMT (C)</p> Signup and view all the answers

What technology is employed by HDSL to reduce susceptibility to attenuation?

<p>2B1Q encoding (C)</p> Signup and view all the answers

How does SDSL differ from ADSL in terms of communication symmetry?

<p>SDSL provides full-duplex symmetric communication (C)</p> Signup and view all the answers

What is the maximum data rate achievable by HDSL without repeaters?

<p>2 Mbps (B)</p> Signup and view all the answers

Which device is installed at the telephone company site to manage DSL connections?

<p>DSLAM (B)</p> Signup and view all the answers

What encoding technique does HDSL replace to enhance data transmission over long distances?

<p>Alternate mark inversion (D)</p> Signup and view all the answers

What is a key characteristic of VDSL compared to ADSL?

<p>VDSL primarily uses coaxial cables (B)</p> Signup and view all the answers

Which feature makes ADSL less suitable for business use compared to SDSL?

<p>Asymmetric communication design (B)</p> Signup and view all the answers

What is the primary benefit of using a media converter in a network?

<p>It extends links over greater distances using fiber optic cable. (D)</p> Signup and view all the answers

Which technology does the 2BASE-TL LAN extender utilize to achieve its data transmission?

<p>G.SHDSL.bis (D)</p> Signup and view all the answers

What is the maximum data transmission speed of the 10PASS-TS LAN extender?

<p>10.0 Mbit/s (D)</p> Signup and view all the answers

Which type of cable is typically used with copper-based Ethernet connections?

<p>Unshielded twisted pair (UTP) cable (C)</p> Signup and view all the answers

What is one drawback of using copper-based Ethernet connections mentioned in the content?

<p>They are subject to electromagnetic interference. (B)</p> Signup and view all the answers

How does fiber optic cable improve data transmission compared to copper cable?

<p>It protects data from noise and interference. (D)</p> Signup and view all the answers

What type of link does the 2BASE-TL LAN extender provide?

<p>Full-duplex long reach Point-to-Point link (C)</p> Signup and view all the answers

Which method is used by network extenders to transmit information?

<p>DMT (A)</p> Signup and view all the answers

Flashcards

Modem's function

A modem converts digital computer data into analog signals suitable for transmission over the PSTN (telephone system) and vice-versa.

PSTN

Public Switched Telephone Network; traditional telephone system.

Analog signals

Continuous signals that vary in amplitude over time.

Digital signals

Signals that have discrete values.

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Modem Working Principle

Modems convert digital data into analog signals for transmission over telephone lines and convert them back to digital data at the receiving end.

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Morse Code

A system of dots and dashes used to represent letters of the alphabet, punctuation marks, and numbers.

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ASCII code

A binary coding system used by modems to represent characters.

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Data transmission over telephone lines

Modems use analog signals to send digital data sequentially over telephone lines, similar to Morse Code.

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Equalizer Retuning

Equalizers need adjustments when the communication line changes or periodically, especially for low-quality lines with frequent parameter changes.

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Automatic Equalizer

Equalizers that adjust themselves to line quality changes automatically after a connection is established.

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Equalizer Adjustment Speed

Equalizer adjustments happen in a timeframe of 15-25 milliseconds, and can be adjusted up to 2400 times per second in some modems.

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Synchronous Modems

Modems that operate in the same manner as asynchronous modems but at higher speeds, with more complex channel splits.

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Split System Modem (SSM)

Modems that split the channel into parts at different speeds, either by a basic split or a more advanced multipoint connection.

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Synchronous Data

Data transmitted synchronously (with clock signal) often grouped into blocks for efficient transmission and error detection.

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Analog Media

Communication channels (like telephone lines) that have limited bandwidth.

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Analog Bandwidth

The frequency range available on a line like a telephone line, useful for data communication.

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ADSL

Asymmetric DSL, provides higher download speeds than upload speeds.

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XDSL

A family of DSL technologies, including ADSL, VDSL, HDSL and SDSL.

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Local loop bandwidth

The maximum data rate a local telephone line can handle, typically up to 1.1 MHz.

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Filter in the end office

Limits the bandwidth of the local loop to 4 KHz, sufficient for voice calls.

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Adaptive technology

DSL can adjust its data rate based on factors like distance, cable size, and signaling.

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Upstream

Data transfer from your computer to the internet.

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Downstream

Data transfer from the internet to your computer.

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ADSL Data Rate

The speed of ADSL changes based on the condition of the phone line. It's not fixed.

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Discrete Multi Tone (DMT)

ADSL uses DMT, a modulation technique combining QAM and FDM, to send data over multiple channels.

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Bandwidth Division in ADSL

The total ADSL bandwidth is divided into channels, each with a specific task (like voice, data, control).

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Upstream Channels

Channels 6 to 30 in ADSL are for sending data from your computer to the internet.

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Downstream Channels

Channels 31 to 255 in ADSL are for receiving data from the internet to your computer.

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ADSL Modem

A device that connects your computer to the ADSL line, separating voice and data signals.

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ADSL Splitter

A device that separates voice and data signals from the ADSL line.

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Why is ADSL data rate below maximum?

ADSL data rate is often less than the theoretical maximum because some channels are unused due to noise or bad signal quality.

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ADSL Modulation

ADSL uses DMT (Discrete Multitone Technique) to modulate and demodulate data, creating separate channels for downstream (Internet to user) and upstream (user to Internet) traffic.

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ADSL Installation

ADSL requires a technician to install the splitter at the customer's location. The voice line uses existing wiring, but the data line needs professional installation.

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ADSL Cost

ADSL can be expensive due to the requirement for professional installation and the use of specialized equipment like the DSLAM at the telephone company's site.

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Universal ADSL

Universal ADSL (ADSL Lite) is an alternative to traditional ADSL, offering a simpler and potentially more affordable option.

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DSLAM Function

A DSLAM (Digital Subscriber Line Access Multiplexer) at the telephone company's site performs a similar function to the ADSL modem at the customer's location, but also packetizes data for transmission to the internet.

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HDSL Advantage

HDSL (High-bit-rate Digital Subscriber Line) overcomes the limitations of T-1 lines by using 2B1Q encoding, which is less susceptible to signal attenuation, allowing for longer distances without repeaters.

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SDSL vs. ADSL

SDSL (Symmetric Digital Subscriber Line) offers full-duplex, symmetrical communication with equal bandwidth for both upstream and downstream traffic, unlike ADSL which has higher downstream bandwidth. It's an alternative suitable for businesses with high bidirectional data demands.

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LAN Extender

A device that forwards traffic between Local Area Networks (LANs) transparently over long distances, overcoming Ethernet limitations.

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2BASE-TL

A type of LAN extender that uses voice-grade copper wiring to provide full-duplex, long-reach Point-to-Point links up to 2700 meters using G.SHDSL.bis technology.

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10PASS-TS

A type of LAN extender that uses voice-grade copper wiring to provide full-duplex, short-reach Point-to-Point links up to 750 meters using VDSL technology.

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Media Converter

A device that converts Ethernet signals between copper and fiber optic cables, allowing for longer distances, improved noise immunity, and increased bandwidth.

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Ethernet to Fiber Converter

A type of media converter that allows copper-based Ethernet devices to connect over fiber optic cables, enabling longer distances and immunity to electromagnetic interference.

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Copper-based Ethernet Limitations

Copper-based Ethernet connections using UTP cable are limited to a maximum distance of 100 meters due to signal degradation.

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Benefits of Fiber Optic Cable

Fiber optic cables offer several advantages over copper cables, including longer distances, immunity to noise and interference, and significantly higher bandwidth capacity.

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Study Notes

Long Distance Data Transmission

  • This chapter covers modems, their diagnostics, digital subscriber lines (DSL), and extending networks using LAN extenders and media converters for internet/railnet connectivity.
  • A modem is a device that allows digital devices (like computers) to communicate over analog telephone systems.

Modem Working

  • The conventional telephone system (POTS/PSTN) is primarily designed for analog voice signals (300-4000 cycles per second).
  • Modems are needed to translate digital computer data into analog signals that the telephone network can carry.
  • At the receiving end, another modem converts the analog signals back into digital data.

Modem Classification by Range

  • Short Haul: Inexpensive modems for short distances (up to 15 km) not part of a public network. These are distance-sensitive, requiring lower transmission rates for longer distances. They lack circuitry for carrier frequency correction and noise reduction, which are less of a concern over short distances.
  • Voice Grade (VG): Designed for moderate to high data rates, usually on leased lines or dial-up. Higher cost with sophisticated maintenance/tuning.
  • Wideband: Used for high data rates in dedicated computer-to-computer links and large-volume telephone line multiplexing (high-volume calls).

Modem Classification by Operation Mode

  • Half Duplex: Signals can be transmitted in one direction at a time.
  • Full Duplex: Signals can be transmitted in both directions simultaneously. Requires signal separation (e.g., frequency division multiplexing/Echo cancellation).
  • Simplex: Signals can only be transmitted in one direction. Used in telemeter applications.

Modem Classification by Synchronization

  • Asynchronous: Used for slower rates (up to 1800 bps). Data is transmitted in blocks with start/stop bits to synchronize clocks at both ends. Does not require a clock signal during transmission.
  • Synchronous: Used for faster data rates (up to 28800 bps). Data is transmitted in synchronized blocks, accompanied by a clock signal, ensuring proper timing and preventing transmission errors.

Modem Diagnostics

  • Modems are equipped with built-in loop diagnostics (V.54 protocol) to check the integrity of the leased line connection.
  • Tests include local and remote analog/digital loopbacks to isolate transmission problems.
  • Bit error rate testing and loopbacks are also used for quality checks on communication links.

Digital Subscriber Line (DSL) & XDSL Modems

  • DSL technology provides high-speed digital communication over existing telephone lines; variations include ADSL, HDSL, VDSL, and SDSL.
  • ADSL (Asymmetric DSL): Asymmetric data rates (higher downstream than upstream), used for residential internet access.

LAN Extend

  • A LAN extender extends a network segment beyond standard Ethernet limitations (typically 100 meters).
  • Copper wiring is used, potentially with various encoding techniques (TC-PAM, 2B1Q, DMT).

Media Converters

  • Media converters enable connections between UTP (copper-based) Ethernet equipment and fiber optic links.
  • Advantages include extended distances, noise/interference protection, and future-proofing of networks with increased bandwidth capabilities.
  • Converts copper-based signals to fiber-optic signals.

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TA2 CH5 Long Distance Data Transmission PDF

Description

This quiz explores the fundamentals of long distance data transmission, focusing on the role of modems, digital subscriber lines (DSL), and network extension techniques. Learn about the working principles of modems, their classifications, and how they enable communication over analog systems.

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