Tuesday, October 27, 2015

Multiplexing and Multiple Access

Multiplexing And Multiple Access :

Digital Communications

Difference between Multiplexing and Multiple Access:





Sr.No.



Multiplexing




Multiple Access




1

“In telecommunications and 
computer networks, multiplexing
is a process where
multiple analog
 message signals or digital data 
streams are combined into one 
 signal over a shared medium.”

“In telecommunications and
computer networks, a channel
access method or multiple access
 method allows several terminals
connected to the
same multipoint
physical medium to transmit
over it and to share its capacity.”



2

The multiplexed signal is transmitted
 over a communication channel,
 which may be a physical transmission medium.


A channel-access scheme is
 based on a multiplex method 
that allows several data streams 
or signals to share the 
same communication channel or
 physical media.





3

A device that performs the 
multiplexing is called a 
multiplexer (MUX), 
and a device that performs 
the reverse process is called
a demultiplexer (DEMUX).

A channel-access scheme 
is also based on a Multiple access 
protocol and control mechanism, 
also known as media access 
control (MAC). This protocol 
deals with issues such as addressing, 
assigning multiplex channels to 
different users, 
 and avoiding collisions.


4

It works on the physical layer 
(L1) of OSI model.

It works on the Data Link layer
 (L2) of OSI model.








5

Classification of multiplexing:
(w.r.t. channelization methods)

a.Time-division 
multiplexing (TDM)


b.Frequency-division
 multiplexing(FDM)

I.WDM
II.OFDM
III.SC-FDM







c.Code-division multiplexing
 (CDM):
I.DSSS
II.FHSS
III.OFHM
IV.MC-CDM

Classification of Multiple Access:
(w.r.t. channelization methods)

a.TDMA
MF-  TDMA


b.FDMA


I.Wavelength division 
multiple access (WDMA)
II.Orthogonal frequency
 division multiple access
 (OFDMA)
III.Single-carrier
 FDMA (SC-FDMA)



    c.Code division multiple access (CDMA):
I.Direct-sequence CDMA 
(DS-CDMA), based on 
 Direct-sequence spread 
spectrum (DSSS)
II.Frequency-hopping CDMA 
(FH-CDMA), based on 
 Frequency-hopping spread 
spectrum (FHSS)
III.Orthogonal 
frequency-hopping
 multiple access (OFHMA)
IV.Multi-carrier code 
division multiple 
access (MC-CDMA)












6

Classification of multiplexing:
(w.r.t. Applications)

a.Telephony:
I.Fiber in the loop (FITL)
II.FDM in DSL









b.Video processing
I.TDM


c.Digital broadcasting
I.statistical multiplexing                  



Classification of Multiple Access:
(w.r.t. Packet mode methods)

       a.Contention based random multiple access methods:
I.Aloha
II.Slotted Aloha
III.(MACA)
IV.(MACAW)
V.(CSMA)
VI.(CSMA/CD)
VII.(CSMA/CA)
VIII.(DCF)
IX.(PCF)

b.Token passing
    I.Token ring
II.Token bus

 c.Polling

      
d.Resource reservation 
(scheduled) packet-mode
 protocols
I.(Dynamic TDMA)
II.(PRMA)
III.(R-ALOHA)



7

Example:
Cisco Frame Relay and X.25 
systems are also categorized 
as Statistical TDMs.


Example:
Service providers can deploy 
Cisco-CDMA data services 
to track ongoing performance 
of their network end to end.