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Transcript of Jeeva Review3
8/12/2019 Jeeva Review3
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OBJECTIVE
To model and simulate the Carrier Phase
Offset (CFO) with aid of ML sequence.
Simulation Tool : Matlab
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WORK DONE SO FAR
Estimation of Timing Offset
Estimation of Carrier Frequency Offset
Work done nowo Estimation of Phase Offset
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BLOCK DIAGRAM OF OFDM SYSTEM
Data BitsQPSK
MappingIFFT
Cyclic
Prefix
Rayleigh,
AWGN
Channel
Synchroni
zation
Removal OfCyclic
Prefix,training
Sequence
FFTEquailizatio
nSymbol
Detection
PN
sequence
Generator
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FRAME STRUCTURE OF OFDM SYSTEM
Pilot
s(M
L
seq)
sym
1
sym
2
…… sym
100
Pilot
s(M
L
seq)
sym
1
sym
2
…… sym
99
Sym
100
For every 100 OFDM symbols , one block type pilotsare used.
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PN SEQUENCE
It is a deterministically signal but looks like random
sequences.
Assume order = 9, the generator polynomial is
x^9+x^4+1.It is generated using linear feedback
shift register and exclusive OR gate as below
1 2 763 4 5 98
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C ARRIER PHASE OFFSET
Frequency estimation alone could not complete the
carrier synchronization, additionally it requires
estimating and correcting the phase offset also.
The technique involves the received signal is
multiplied with conjugate of pilots, which is
represented as
y(k) = E[r(k) * (conj (pilots))]
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MODELING OF SIGNAL
Delay
Frequency
and phase
offset
AWGN & Fading
channel noise
Signal from
transmitter
Signal to
Receiver
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DESIGN SPECIFICATION
PARAMETERS VALUE
Nfft 512
N Used Carriers 496Number of lower
frequency guard
subcarriers
8
Number of upperfrequency guard
subcarriers
7
Cyclic Prefix 32
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CONT…
PARAMETERS VALUE
Sampling frequency 1.6MHz
Sampling time (Ts ) 625ns(1/1.6MHz)
Number of frame 10OFDM symbol interval 174.08µs( 544 * Ts)
CP length 20µs ( 32*Ts )
Sub carrier spacing 6.25KHz(1.6MHz/256)
Number of Pilots 256
Modulation QPSK
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FADING CHANNEL SPECIFICATION
Sampling Time in ns 0.1
Path delays in ns 0 781 156 2344
Path gains in dB 0 -3 -6 -9
Delay spread 2344ns
Doppler shift 0
Fading type Frequency selective & slow
fading
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SIMULATION RESULT(MSE PLOT FOR PHASE
OFFSET = 0.5235 IN RADIANS)
In MSE plot, as SNR
varies the MSE value
reduces and move to
zero
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Phase offset(in
radian)
Estimated
offset(AWGN
channel)
Estimated offset
(Rayleigh channel)
0.5236 0.5241 0.5396 0.6109
0.6107
0.6170
0.6989 0.6990 0.6953 0.7854 0.7850 0.7916 0.8727 0.8730 0.8854 0.9599 0.9596 0.9658 1.0472 1.0468 1.0340 1.1345 1.1348 1.1503 1.2217 1.2218 1.2973 1.3090 1.3090 1.4966
SIMULATION RESULT (AT SNR=5dB)
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REFERENCE
Lee. J, Lou, H and Toumpakaris, D. (Oct.
2004)’Maximum likelihood estimation of time and
frequency offset for OFDM systems ’- Electronics
Letters. Volume 40, Issue 22, 28 Page(s):1428 – 1429
Van de Beek J J, Sandell M, Boriesson P (1997)’ MLestimation of time and frequency offset in OFDM
Systems’ - IEEE Transaction on Signal Processing,
volume 45 No.7 pp.1800 – 1805
Michele Morelli, Member IEEE, C.-C. Jay Kuo, Fellow
IEEE, and Man-On Pun, Member IEEE –
‘Synchronization Techniques for Orthogonal Frequency
Division Multiple Access (OFDMA) ‘: A Tutorial Review