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This chapter is from the book

What You Have Learned

  • Information is a numerical quantity that measures the randomness of a system.

  • Symbols such as letters have an information content. Not every symbol is equally likely to occur.

  • The redundancy of a system measures how likely symbols are to be repeated.

  • Data communications systems use redundancy to detect and correct errors in transmission.

  • Entropy of a character set or alphabet serves as a goal for developing data-compression algorithms.

  • Signals can travel through guided and unguided transmission media.

  • Adding inductance to pairs of wires is called loading. Loading is used to reduce high-frequency attenuation over the wire pair.

  • The EIA/TIA-568 standard specifies cabling parameters used to connect equipment in wiring closets to workstations.

  • The most common type of twisted-pair cable used with LANs is currently Category 5 cable, while Category 5e is used to support Gigabit Ethernet.

  • The bit error rate of a communications medium primarily depends upon the ability of a receiver to distinguish a signal from noise.

  • Low-orbit satellites support low-power transmitters and are ideal for two-way paging and international cellular communications.

  • Fiber-optic transmission systems send data signals as light rays. These systems have much higher bandwidth and have immunity from most external interference.

  • Transmission rates over channels are limited by the bandwidth of the channel, the signal-to-noise ratio, and the amount of intersymbol interference in the transmitted waveform.

  • The use of different types of digital transmission systems is based on bandwidth availability and economics.

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