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Definition
Signals attenuate more at higher frequenceis than at lower frequencies.
The difference of attuenuation of the high-frequency signals relative to that of low-frequency signals increase as the length of the cable system increases.
The cable tilt must be compensated for or equalized in order to maintain a flat amplitude response throughout the cable system.
Amplifiers are used to equalize the signals by amplifying the higher frequency signals and by adding attenuation to the lower frequencies. |
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Definition
Bit Error Rate
This error rate depend on the signal to noise ratio at the receiver.
BER = Ne/Nb or Ne/(datarate * time)
Ne = number of errors over the interval
Nb number of bits transmitted over interval |
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Definition
Digital Phase Lock Loop
A method used to sychronous with the date being received. If data is very late A = -2 if a little late B = -1 if right on the target C = 0 little early D = +1 and very early E = +2. At most DPLL will need 10 bits to get sychronied with the recieving data. |
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| The arrive times of different rays that propagates on different modes are unequal. The staggered arrival times spread the burst as it propagates along the fiber. If the time allowed for teh transmisison of one Bit is short enough the bits will overlap at the receiver. Thus the effeect of modal dispersion is to impose a minimum value of T, the time taken for transmitting each bit. As a consequence model disperion limits the maximum bit-transmission rate. Transmission for a long fiber is less that that of a short fiber. |
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Application
TCP (Transport Layer)
IP (Internet Layer)
Network
Physical |
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Definition
| Responsible for functions dealing with transmission medium, singals, and data rate |
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Definition
| responsible for exchange of data with the newtork to which the host is attached. Thus this layer is concerned with access to and routing data across a network for two hosts attached to the same network. |
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Definition
| provides the routing function across multiple networks |
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Definition
| ensures reliable exchange of data. One of the responsiblitity of this layer is to make sure the data arrive at the destination in the same order in which they were sent. |
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Definition
| Provides the functionality needed to support the user applications |
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Definition
•Uses the 1’s-complement sum as the basis of the block sum check.
•The error-detection properties of this scheme are better than the modulo-2 sum method.
•The characters are added together using 1’s complement arithmetic. All the bits in the resulting sum are then inverted and used as BCC.
•At the receiver, the 1’s complement sum of all the characters in the block-including the BCC-is computed and, if no error are present, the result should be zero.
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Term
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Definition
–The transmitter waits for an acknowledgment after transmitting each frame
–The receiver sends an acknowledgment after receiving a frame. This indicates its willingness to receive another frame.
–The destination can stop the flow by withholding acknowledgment.
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