This document discusses different types of multiplexing including frequency division multiplexing (FDM), time division multiplexing (TDM), and code division multiple access (CDMA). FDM divides the spectrum into logical channels and allocates each user an exclusive frequency band. TDM divides the shared channel among users by assigning time slots. CDMA allows multiple users to occupy the entire channel bandwidth simultaneously by encoding each user's signal differently.

1. Multiplexing
Asst.Prof. Rupali Lohar
Dept. of Computer Science & Engineering
B. R. Harne College Of Engineering & Technology, Karav, Post Vangani (W Tal
Ambernath, Mumbai, Maharashtra 421503

2. Multiplexing
• Multiplexing is a technique in which, multiple simultaneous analog or
digital signals are transmitted across a single data link.
• The concept behind it is very simple: Proper Resource Sharing and its
Utilization.

6. Types of Multiplexing-

8. Frequency Division Multiplexing(FDM)
• FDM is used because of the fact that, a number of frequency band
can work simultaneously without any time constraint.
• For Example : Frequency Division Multiplexing can be used for radio
station in a particular region as every radio station will have their own
frequency and can work simultaneously without having any constraint
of time.
• FDM divides the spectrum or carrier bandwidth in logical channels
and allocates one user to each channel. Each user can use the
channel frequency independently and has exclusive access of it. All
channels are divided in such a way that they do not overlap with each
other.

11. Advantages of FDM
• This concept is applicable on both analog signals as well as digital signals.
• Simultaneous signal transmission feature.
Disadvantages of FDM
• Less Flexibility.
• Bandwidth wastage is high and can be an issue.

12. Time Division Multiplexing(TDM)
• TDM the shared channel is divided among its user by means of time slot. Each
user can transmit data within the provided time slot only. Digital signals are
divided in frames, equivalent to time slot i.e. frame of an optimal size which can
be transmitted in given time slot.
• TDM works in synchronized mode. Both ends, i.e. Multiplexer and De-
multiplexer are timely synchronized and both switch to next channel
simultaneously.
• Time Division is used for a particular amount of time in which the whole
spectrum is used.
• Time frames of same intervals are made such that the entire frequency spectrum
can be accessed at that time frame.

14. Synchronous TDM
• The synchronous TDM is very useful in both analog as well as digital
signals. In this type of TDM, the connection of input is allied to a
frame. For example, if there are n-connections in the frame, then a
frame will be separated into n-time slots, and for every unit, each slot
is assigned to every input line.
• In the sampling of synchronous TDM, the speed is similar for every
signal, as well as this sampling needs a clock (CLK) signal at both the
ends of sender & receiver. In this type of TDM, the multiplexer assigns
the similar slot for each device at every time.

16. Asynchronous TDM
1. It is also known as statistical time division multiplexing.
2. Asynchronous TDM is called so because is this type of multiplexing, time slots are not fixed i.e. the slots are
flexible.
3. Here, the total speed of input lines can be greater than the capacity of the path.
4. In synchronous TDM, if we have n input lines then there are n slots in one frame. But in asynchronous it is
not so.
5. In asynchronous TDM, if we have n input lines then the frame contains not more than m slots, with m less
than n (m < n).
6. In asynchronous TDM, the number of time slots in a frame is based on a statistical analysis of number of
input lines.

19. Advantages of TDM
• Single user at a time.
• Less complex and more flexible architecture.
Disadvantages of TDM
• Difficult to implement.

20. Space Division Multiplexing(SDM)
• Space Division can be called as the combination of concepts of
Frequency Division Multiplexing and Time Division Multiplexing.
• In SDM, the goal is to pass messages or data parallelly with the use of
specific frequency at certain interval of time.
• It means, a particular channel for some amount of time will be used
against a certain frequency band.

21. Space Division Multiplexing(SDM)
Advantages of SDM
• High Data transmission rate.
• Optimal Use of Time and Frequency bands.
Disadvantages of SDM
• Inference Problems.
• High inference losses.
• For Example : GSM(Global Service For Mobile) Technology.

22. Code Division Multiple Access(CDMA)
• In CDMA, a number of users occupy all of the channel bandwidth all
of the time. Their signals are encoded so that information from an
individual transmitter can be detected and recovered only by a
properly synchronized receiving station that knows the code being
used.
• Each receiving station has its own code, called its “address” and a
transmitting station simply modulates its transmission with the
address of the intended receiver whenever it wishes to send a
message to that receiver.

23. Features of CDMA
• CDMA is Full Duplex
• Multipath reception improves voice clarity
• Security or Interference rejection : Cross- correlating the code signal
with a narrowband signal spreads the power of the narrowband
signal, thereby reducing the interfering information bandwidth.

24. Power Control: Avoids near-far effect
and increases mobile unit battery life
POWER CONTROL
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25. CDMA Architecture
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Consists of the following components
Mobile user/subscriber (MS)
Base Trans/Receive Station (BTS) &Antennae
Mobile Switching Center (MSC)
Authentication Center (AC)
Operation, Administration & Maintenance
(OAM)

26. CDMA Architecture
IOS: Interoperability Specification IWF: Interworking Function
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27. CDMA Channels
Forward Link Channels
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28. CDMA Channels
Reverse Link Channels
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29. CDMA Call Processing
There are four stages or modes in CDMA call
processing
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30. CDMA Call Execution
Land to Mobile Call
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31. CDMA Call Execution
Mobile to Land Call
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32. CDMA Call Execution
Mobile to Mobile Call within same network
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33. CDMA Call Execution
Mobile to Mobile Call in different network
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34. CDMA Applications
In Bluetooth
 Bluetooth uses Fast FH-CDMA with a hopping
rate of 1,600 hops per second.
 Each piconet has its own spreading sequence.
 FH/CDMA in Bluetooth allows tens of piconets
to overlap in the same area providing an
effective throughput of more than 1 Mbps.
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35. Limitations of CDMA
Synchronization Requirement
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• Unavailability of large contiguous bandwidth
• Near-far Effect
• Self-Jamming