Adaptive OFDM_Orthogonal Frequency Dvision Multiplexing_1

1. BER PERFORMANCE OF OFDM SYSTEM
WITH ADAPTIVE MODULATION
Presented by:
Harish Rajula
P14EC009
SV_NIT-Surat
harish.rajula91@gmail.com
Ieee Explorer search:BER Performance of OFDM System with
Adaptive Modulation

2. Challenges in Designing OFDM
Transmitter:
1. The Number of subcarriers required to send
the given data
Each subcarriers are centered at frequencies
that are orthogonal to each other (usually
multiples of frequencies).

3. 2. The second design parameter could be
the
Modulation format that we wish to use
 An OFDM signal can be constructed using
anyone of the
following digital modulation techniques
namely
BPSK,
QPSK,
QAM etc..,

5.  In an OFDM transmission system if the
same
fixed transmission scheme is used for all
OFDM
subcarriers,
 Each subcarrier is attenuated individually
under the frequency-selective and fast
fading channel
 It results in highest attenuation
and hence poor performance

6. Adaptive Modulation

8.  Adaptive modulation comparison is made with fixed
modulation system under various IFFT size(N).
 BER is calculated using following formula:
 Adaptive modulation is introduced by presenting
some
of the simpler adaptive Quadrature Amplitude
Modulation(QAM) schemes and their performance
for
both perfectly known and predicted channels.

12. Here IFFT size is denoted by N. For
IFFT size N=64,
128, 256,512 ,1024,2048 BER
performance has shown

13. In adaptive modulation, modulation rate
changes based upon value of an
instantaneous SNR.
The BER performance comparison between
fixed and adaptive modulation shows that
BER performance for all modulation
techniques is better, when IFFT size is
greater than 512.
For all values of IFFT sizes, average BER of
Adaptive modulation is approximately
0.203568 and for higher order fixed
modulation it is approximately 0.913545 .
Hence, it concludes that BER performance of

14. Effect of Channel Prediction on
Automatic Modulation Classification
for Adaptive OFDM Systems…
 Adaptive OFDM for Wireless Interconnect
in Confined Enclosures…..