ISM-OFDM and FBMC

1. SIM-OFDM and FBMC
Ph.D Course_ Broadband Communications
Lect#7
hikmat.abdullah@coie-nahrain.edu.iq

2. Problems of classical OFDM

3. Index Modulation (IM)Techniques
• Recently IM techniques are introduced as possible solutions
to OFDM problems mentioned earlier
• The techniques include: SIM-OFDM and ESIM-OFDM
SIM-OFDM

4. SIM-OFDM

5. Problems of SIM-OFDM
There are two main issues which limit the performance of SIM-
OFDM:
 An OOK detector at the destination requires the usage of a threshold.
SIM-OFDM suffers from bit error propagation in the presence of Additive
White Gaussian Noise (AWGN),an incorrect detection of a carrier state not
only leads to incorrect demodulation of the M-QAM symbol it encodes, but
also to incorrect demodulation of all subsequent QAM symbols

6. Enhanced SIM-OFDM (ESIM-OFDM)

7. ESIM-OFDM
Receiver
Transmitter

8. ESIM-OFDM

9. Advantages of ESIM-OFDM
The error that can be made is limited within each pair of carriers.
The number of active carriers within each pair is known and is always
one, so there is no need to use a threshold for OOK detection. Instead,
the carrier with higher power can be recognized as active.
Problem of ESIM-OFDM:
The only disadvantage of the modified scheme, compared to the former
SIM-OFDM, is the slightly reduced spectral efficiency. Spectral efficiency
of SIM-OFDM, measured in bits/carrier, is
Η OLD SIM−OFDM = log2(M)/ 2 + 1
while the spectral efficiency of the modified SIM-OFDM is
Η NEW SIM−OFDM = log2(M) /2 + 1/ 2

10. Filter Bank Multicarrier Modulation
(FBMC)
• Filter Bank Multicarrier (FBMC) is a multicarrier modulation that
employs localized pulse shaping for improved spectral properties.
• This is opposed to Orthogonal Frequency-Division Modulation (OFDM)
where the basic rectangular pulse is employed which has a slowly
decaying spectrum.
• OFDM requires Cyclic Prefix (CP) to eliminate the ISI introduced by the
multipath effect of the wireless channel.
• In FBMC, the CP is not required to combat the multipath channel
because of the localized pulse shape.

11. OFDM vs FBMC Spectrum Shape

12. OFDM vs FBMC
OFDM CP-OFDM FBMC
No CP With CP No CP
Orthogonal basis Biorthogonal Basis Orthogonal Basis
Complex modulating
symbols
Complex modulating
symbols
Real modulating symbols
Signaling interval=T=1/F Signaling interval=T+TCP Signaling interval=T/2
Pulse Duration=T Pulse Duration=T+TCP Pulse Duration=KT (K=4)
Basic rectangular pulse
shape
Basic rectangular pulse
shape
Localized pulse shape

13. OFDM vs FBMC

14. FBMC Transmitter

15. FBMC Receiver

16. Symbols Overlap in OFDM and FBMC

17. Locality of pulse Shaping in FBMC




 dt
t
p
t
E
T
s
e
2
2
2
)
(
1




 df
f
P
f
E
B
s
e
2
2
2
)
(
1









 df
f
P
dt
t
p
Es
2
2
)
(
)
(

4
1

e
eT
B
2
2
)
( t
e
t
g 



2
2
2
/
)
( 



 f
e
f
G 

e
eT
B

 4

The Gaussian function is the most localized
pulse shape with locality parameter =1
because it has the same shape in time domain
and frequency domain
However, the Gaussian function is
not orthogonal, therefore, it is not
suitable for FBMC

18. Pulse Shaping Filters in FBMC
The impulse response of the different shaping filters

19. Pulse Shaping Filters in FBMC
The spectrum of the different shaping filters

20. Pulse Shaping Filters in FBMC
The PSD of OFDM and FBMC with different pulse shapes
N=1024, Nu=600

21. The PSD of OFDM and FBMC with different pulse shapes N=1024, Nu=600 for
OFDM and Nu=1000 for FBMC
Pulse Shaping Filters in FBMC

22. Rectangular RC IOTA PYDYAS Hermite
Te 0.2887 0.2435 0.2729 0.2745 0.2015
Be 8.48 0.3612 0.3242 0.328 0.4031
 30.76 1.1053 1.1118 1.1314 1.0208
0 1.13105 2.4104 1.17107 2.35109
The parameters of the shaping filters used in FBMC



)
0
,
0
(
)
,
(
2
2
)
2
,
2
(
k
n
p
I kK
nM
A

Pulse Shaping Filters in FBMC

23. PHADYAS Shaping Filter

24. Other Multicarrier Techniques for Future Comm.

25. Other Multicarrier Techniques for Future Comm.