In time-division multiplexing, time on the information channel, or fiber, is shared among the many data sources.
The multiplexer MUX can be described as a type of “rotary switch,” which rotates at a very high speed, individually connecting each input to the communication channel for a fixed period of time. The process is reversed on the output with a device known as a demultiplexer, or DEMUX. After each channel has been sequentially connected, the process repeats itself. One complete cycle is known as a frame.
To ensure that each channel on the input is connected to its corresponding channel on the output, start and stop frames are added to synchronize the input with the output.
TDM systems may send information using any of the digital modulation schemes described (analog multiplexing systems also exist). This is illustrated in following Figure.
The amount of data that can be transmitted using TDM is given by the MUX output rate and is defined by equation.
MUX output rate = N × Maximum input rate
where N is the number of input channels and the maximum input rate is the highest data rate in bits/second of the various inputs. The bandwidth of the communication channel must be at least equal to the MUX output rate.
Another parameter commonly used in describing the information capacity of a TDM system is the channel-switching rate. This is equal to the number of inputs visited per second by the MUX and is defined as
Channel switching rate = Input data rate × Number of channels
This post was last edited by user_2915719 at 2018-12-25 10:02.
