14-08-2012, 10:03 AM
Multiplexing Techniques
[attachment=31367]
MULTIPLEXING
Whenever the bandwidth of a medium linking two devices is greater than the bandwidth needs of the devices, the link can be shared. Multiplexing is the set of techniques that allows the simultaneous transmission of multiple signals across a single data link. As data and telecommunications use increases, so does traffic.
In synchronous TDM, the data rate of the link is n times faster, and the unit duration is n times shorter.
Interleaving
The process of taking a group of bits from each input line for multiplexing is called interleaving.
We interleave bits (1 - n) from each input onto one output.
Inefficient use of Bandwidth
Sometimes an input link may have no data to transmit.
When that happens, one or more slots on the output link will go unused.
That is wasteful of bandwidth.
Code division multiplexing (cdm)
Also known as Code division multiple access (CDMA).
An advanced technique that allows multiple devices to transmit on the same frequencies at the same time.
Each mobile device is assigned a unique 64-bit code (chip spreading code)
To send a binary 1, mobile device transmits the unique code
To send a binary 0, mobile device transmits the inverse of code
[attachment=31367]
MULTIPLEXING
Whenever the bandwidth of a medium linking two devices is greater than the bandwidth needs of the devices, the link can be shared. Multiplexing is the set of techniques that allows the simultaneous transmission of multiple signals across a single data link. As data and telecommunications use increases, so does traffic.
In synchronous TDM, the data rate of the link is n times faster, and the unit duration is n times shorter.
Interleaving
The process of taking a group of bits from each input line for multiplexing is called interleaving.
We interleave bits (1 - n) from each input onto one output.
Inefficient use of Bandwidth
Sometimes an input link may have no data to transmit.
When that happens, one or more slots on the output link will go unused.
That is wasteful of bandwidth.
Code division multiplexing (cdm)
Also known as Code division multiple access (CDMA).
An advanced technique that allows multiple devices to transmit on the same frequencies at the same time.
Each mobile device is assigned a unique 64-bit code (chip spreading code)
To send a binary 1, mobile device transmits the unique code
To send a binary 0, mobile device transmits the inverse of code