26-06-2012, 12:24 PM
TRANSMISSION MEDIUM & COMMUNICATION CHANNELS
[attachment=25548]
Design factors
A number of design factors relating to the transmission medium and the signal determine the data rate and distance
Bandwidth
All other factors remaining constant, the greater the bandwidth of a signal, the higher the data rate that can be achieved.
Transmission impairments
Impairments, such as attenuation, limit the distance. For guided media, twisted pair generally suffers more impairment than coaxial cable, which in turn suffers more than optical fiber. When a signal transmits through the channel, channel inherently added some noise to the signal. This noise is known as thermal noise. Noise means any undesirable effect on the signal of interest which results in attenuation, degradation or corruption of the signal. The effect of the noise on the signal can be reduced by increasing the power in the transmitted signal but which results in lesser battery life i.e. more power consumption. There is one more limitation that is available channel bandwidth. Because of these two limitations of the channel, we have to design our communication system such that we can transmit as much data as possible with out getting corrupted.
TYPES OF COMMUNICATION CHANNELS
There are many types of channels. Communication channels are mainly two types guided (wired) channels and unguided (wireless) channels.
Wire line channels operates at frequency few kHz to several hundreds of kHz. Wired media include copper cables (e.g., twisted-pair copper wire cable - the "telephone cable", coaxial cable, UTP cable - the "LAN cable", etc.) and optical fiber cables (made of glass or plastic). Copper cables allow the propagation of electric signals (i.e., electric voltage or current pulses), whereas optical fiber cables allow the propagation of light pulses.
Twisted pairs
Twisted Pair is a transmission medium that uses two conductors that are twisted together to form a pair. The concept for the twist of the conductors is to prevent interference. Ideally, each conductor of the pair basically receives the same amount of interference, positive and negative, effectively cancelling the effect of the interference. Typically, most inside cabling has four pairs with each pair having a different twist rate.
[attachment=25548]
Design factors
A number of design factors relating to the transmission medium and the signal determine the data rate and distance
Bandwidth
All other factors remaining constant, the greater the bandwidth of a signal, the higher the data rate that can be achieved.
Transmission impairments
Impairments, such as attenuation, limit the distance. For guided media, twisted pair generally suffers more impairment than coaxial cable, which in turn suffers more than optical fiber. When a signal transmits through the channel, channel inherently added some noise to the signal. This noise is known as thermal noise. Noise means any undesirable effect on the signal of interest which results in attenuation, degradation or corruption of the signal. The effect of the noise on the signal can be reduced by increasing the power in the transmitted signal but which results in lesser battery life i.e. more power consumption. There is one more limitation that is available channel bandwidth. Because of these two limitations of the channel, we have to design our communication system such that we can transmit as much data as possible with out getting corrupted.
TYPES OF COMMUNICATION CHANNELS
There are many types of channels. Communication channels are mainly two types guided (wired) channels and unguided (wireless) channels.
Wire line channels operates at frequency few kHz to several hundreds of kHz. Wired media include copper cables (e.g., twisted-pair copper wire cable - the "telephone cable", coaxial cable, UTP cable - the "LAN cable", etc.) and optical fiber cables (made of glass or plastic). Copper cables allow the propagation of electric signals (i.e., electric voltage or current pulses), whereas optical fiber cables allow the propagation of light pulses.
Twisted pairs
Twisted Pair is a transmission medium that uses two conductors that are twisted together to form a pair. The concept for the twist of the conductors is to prevent interference. Ideally, each conductor of the pair basically receives the same amount of interference, positive and negative, effectively cancelling the effect of the interference. Typically, most inside cabling has four pairs with each pair having a different twist rate.