Data communication Frequency Division Multiple Access (FDMA) and Time Division Multiple Access(TDMA)

1. Presented By
MD. ABU TALHA
REG: 2012331008
CSE,SUST

2. OBJECTIVES
 What is FDMA?
 Features of FDMA.
 Advantage of FDMA.
 Disadvantage of FDMA.
 What is TDMA?
 Features of TDMA.
 Advantage of TDMA.
 Disadvantage of TDMA.

3. (FDMA)
Frequency Division Multiple Access

4. Total system bandwidth is divided
into narrow frequency slots. Each
user is allocated a unique
frequency band or channel.
1
7
6
5
2
3
4
(FDMA)
Frequency Division
Multiple Access

5. FDMA GRAPH
Time(s)
Frequency(f)
F1 F2 F3 F4 F5 F6 F7

6.  Systems used for low/medium traffic intensity.
 Narrow band interference resistance of the
channel, but sensitive to interference.
 Simplicity of work equipment.
 Difficulty of insertion of the signaling associated
with the call.
 Limitations for quality improvement.
Features of FDMA

7. Numbers of Channels in FDMA
Let,
Btotal = Total system bandwidth,
Bguard = Guard band at edge,
Bch = Single radio channel bandwidth.
Then the number of channels in a FDMA System:
N =
Btotal − 2Bguard
Bch

8. Numbers of Channels in FDMA
 Example:
AMPS (Advanced Mobile Phone Service) uses FDMA with,
Btotal = 12.5 MHz,
Bguard = 10 kHz and
Bch = 30 kHz
N =
12.5 × 106 − 2(10 × 103)
30 × 103
N =416

9. Advantages of FDMA
 If channel is not in use, it sits idle.
 Channel bandwidth is relatively narrow
(30kHz).
 Simple algorithmically, and from a hardware
standpoint.
 Fairly efficient when the number of stations is
small and the traffic is uniformly constant.
 Capacity increase can be obtained by reducing
the information bit rate and using efficient
digital code.
 No need for network timing.

10. Disadvantages to using FDMA
 The presence of guard bands.
 Maximum bit rate per channel is fixed .
 Small inhibiting flexibility in bit rate capability.
 Does not differ significantly from analog system.

11. (TDMA)
Time Division Multiple Access

12. Several users share
one frequency
channel.
Users have to wait
for their turns to
transmit or receive.
0 1 2 3 4 5 6 7 0
0 1 2 3 4 5 6 7 0
(TDMA )
Time Division Multiple Access
TDMA Frame
TDMA frame length = 4.615 ms / 8 Time slot

13. TDMA GRAPH
Time(s)
Frequency(f)
U2
u1
u2
u1

14.  Access Complexity: Strict time synchronization.
 For high capacity systems Traffic.
 Simplification of multi-channel stations.
 Delay in communication.
 Need for digitization of information.
 It achieves high quality.
 Possibility of using a single carrier frequency for both
directions of communication.
Features of TDMA

15. Efficiency of TDMA frame

16. Advantages of TDMA
 Flexible bit rate.
 No frequency guard band required.
 No need for precise narrowband filters.
 Extended battery life.
 The most cost-effective technology for upgrading a current analog
system to digital

17. Disadvantages to using TDMA
 Requires network-wide timing synchronization.
 Requires signal processing for matched filtering and
correlation detection.
 Demands high peak power on uplink in transient mode.
 Multipath distortion.

18. ThankYou All