This chapter is from the book
This chapter is from the book
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.