Multiplexing And Multiple Access :
Digital CommunicationsDifference 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.
|
In the realm of telecommunications and networking, terms like multiplexing and multiple access are often used interchangeably, leading to confusion among enthusiasts and professionals alike. While both concepts involve the efficient sharing of resources in communication systems, they serve distinct purposes and operate on different principles. In this blog post, we'll delve into the nuances of multiplexing and multiple access, elucidating their differences and shedding light on their respective roles in modern communication technologies.
Understanding Multiplexing:
Multiplexing is a technique employed to combine multiple signals or data streams into a single, high-capacity transmission medium, allowing efficient utilization of resources such as bandwidth, time, or space. The primary objective of multiplexing is to enable the simultaneous transmission of multiple signals over a shared channel, thereby maximizing throughput and minimizing costs.
There are several types of multiplexing, each suited for specific applications and scenarios:
Frequency Division Multiplexing (FDM): FDM divides the available frequency spectrum into multiple non-overlapping frequency bands, with each band allocated to a different signal or user. This approach is commonly used in radio and television broadcasting, as well as in cable-based broadband internet services.
Time Division Multiplexing (TDM): TDM allocates fixed-duration time slots within a predefined time frame, allowing multiple signals to take turns transmitting data. This method is prevalent in telecommunications networks, where it ensures efficient utilization of time slots to accommodate various users or services.
Space Division Multiplexing (SDM): SDM involves the use of multiple physical channels or spatial paths to transmit data concurrently. It is commonly employed in wireless communication systems, where multiple antennas or spatial streams are utilized to enhance signal reliability and throughput.
Exploring Multiple Access:
Multiple access refers to the ability of multiple users or devices to access a shared communication medium simultaneously. Unlike multiplexing, which focuses on combining signals for transmission, multiple access techniques facilitate concurrent access to the same channel, enabling efficient communication among multiple entities.
There are several types of multiple access schemes, each offering unique advantages and suited for different scenarios:
Frequency Division Multiple Access (FDMA): FDMA divides the available frequency spectrum into multiple non-overlapping channels, with each channel assigned to a different user or device. This approach is commonly used in cellular communication systems, where each user is allocated a specific frequency band for data transmission.
Time Division Multiple Access (TDMA): TDMA divides the available time slots within a predefined time frame among multiple users, allowing each user to transmit data during their allocated time slot. This method is widely used in digital communication systems, such as GSM and satellite communication networks.
Code Division Multiple Access (CDMA): CDMA allows multiple users to transmit data simultaneously over the same frequency band by assigning each user a unique spreading code. This approach is utilized in 3G and 4G mobile communication systems, where it enables efficient utilization of the available bandwidth and robustness against interference.
Differentiating Multiplexing and Multiple Access:
While both multiplexing and multiple access techniques involve the sharing of resources in communication systems, they serve distinct purposes and operate on different principles:
Objective: Multiplexing aims to combine multiple signals or data streams into a single transmission medium to maximize throughput and minimize costs. Multiple access, on the other hand, enables multiple users or devices to access a shared communication channel simultaneously, facilitating efficient communication among them.
Focus: Multiplexing focuses on the aggregation of signals for transmission, utilizing techniques such as FDM, TDM, or SDM. Multiple access techniques, such as FDMA, TDMA, and CDMA, focus on enabling concurrent access to the same channel by multiple users or devices.
Application: Multiplexing techniques are commonly employed in scenarios where multiple signals need to be transmitted over a shared medium, such as broadcasting, telecommunications, and data networking. Multiple access schemes find applications in wireless communication systems, cellular networks, satellite communication, and shared network infrastructures.
In conclusion, while multiplexing and multiple access are both integral to modern communication systems, they serve distinct purposes and operate on different principles. Multiplexing focuses on combining signals for transmission, while multiple access enables concurrent access to a shared communication channel. Understanding the differences between these concepts is crucial for designing and deploying efficient communication networks that meet the diverse needs of users and applications.