Described a proposition for Physical Layer of Next generation broadcast television (NGBT) and ATSC 3.0 Television standard. The Proposed system is back compatible with existing ATSC standards A/53, A/153 and based on improved version of SC-FDMA modulation.
4. NEW TECHNOGIES
• Any new standard should not only rely on
existing technologies
– Need balanced mix of proven technologies + new
challenges (technologies pushing limit)
– We should explore and choose the right mix of
novel technologies for new standard.
• 1024QAM
• SC-FDMA
• 32VSB
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5. Introduction to SC-FDMA
• SC-FDMA can be regarded as the discrete Fourier transform (DFT)-spread OFDMA,
where time domain data symbols are transformed into the frequency domain by
DFT before going through OFDMA modulation. The orthogonality of the users
steams from the fact that each user occupies different subcarriers in the frequency
domain, similar to the case of OFDMA. Because the overall transmit signal is a
single carrier signal, PAPR is inherently low compared to the case of OFDMA which
produces a multicarrier signal. SC-FDMA uses the cyclic prefix like OFDM.
• SC-FDMA has the same immunity to multipath distortion as OFDM and the same
spectrum of the transmitted signal. Because PAR of SC-FDMA is only ~7.5 dB and
PAR of OFDM is about 10~12.5 dB, the SC-FDMA system needs in significant lower
power of the RF transmitter.
• Unfortunately, SC-FDMA comprises DFT and IDFT cores these are high complexity
devices. For processing of N-point DFT N^2 operations are required. For N-point
FFT, only N*log2(N) operations are required. This is the reason why SC-FDMA is
used only in narrowband LTE uplink.
•
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7. Introduction to improved
SC- FDMA
• In a new SC-FDMA system information symbols come to Transmitter,
which generates a single carrier signal with the spectrum and peak-to-
average ratio which depend of the defined wavelet form. This signal
comes to M-point FFT core. After a FFT transform and subcarrier
mapping the signal arises to the digital filter. The filtered signal is added
to a number of pilot signals. After M-point IFFT transform in the SC-
FDMA signal inserts a cyclic prefix. Because of this cyclic prefix the SC-
FDMA signal has the same an immunity to multipath distortion as OFDM
signal .
• The PAR of a new SC-FDMA signal is about 5~7.5 dB, that's significantly
less than PAR of OFDM (10~12 dB) and known SC-FDMA (7~8.5dB).
• Because of absence of DFT the improved SC-FDMA system can be used for
transmission of broadband signals like TV or broadcast satellite. Note that,
in improved SC-FDMA system, both FFT and IFFT transforms have the
same order(M) and may use the same physical core.
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VIO Concept LTD. 7
12. Features
• Back computable to ATSC A53 /A153 standards.
• Multi-carrier modified SC-FDMA modulation with cyclic prefix and VSB mode of
operation.
• Uses A/53 data fields and data segments synchronization.
• Each data field of A/53 data frame may carry A/53 8VSB signal or ATSC-3.0 SC-
FDMA signal.
• ATSC-3.0 multi-carrier SC-FDMA signal is modulated by 2VSB, 4VSB, 8VSB, 16VSB,
32VSB and has the same immunity to multipath distortion as corresponding
OFDM.
• Modes of operation: 1K, 2K, 4K, 8K subcarriers.
• Inner FEC : LDPC
• Outer FEC : BCH.
• Low PARP ( <7 dB)
• Low level of out-of-band Distortion : (<60 dB)
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13. SC-FMT based ATSC-3.0 is backwards compatible
with ATSC A/53 standard.
• The ATSC-3.0 standard shall be global. The most difficult problem for development
of the global standard is backwards compatibility with existing DTT standards :
ATSC, DVB-T, ISDB-T, DTMB. The most important for ATSC-3.0 is the backwards
compatibility with ATSC standard, that uses very special 8-VSB modulation.
• Version of SC-FDMA system that is backwards compatibility with 8-VSB is shown in
next slides.
• The SC-FDMA output signal has the same spectrum as 8-VSB signal and the same
field and segment synchronization signals as A/53 standard.
• The ATSC -3.0 transmitter generates data frames these can include or normal
A/53 data fields with 8VSB modulation, or ATSC-3.0 data fields with SC-FDMA
modulation.
• The existing A/53 receiver can decode only A/53 data fields remove pilots from
received signal and to sense pilots as additional noise. This noise has power equal
~ 0.1% of the power of the received signal and not affect the receiver
performance.
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22. Systems performance comparison
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STANDARD ATSC A/53 DVB-T2 ATSC-3.0
(Single side band)
Country of origin USA EUROPE USA
Channel Spacing (MHz) 6 1.7,5,6,7,8,10 6
Carrier
(Sub-carrier ) Modulation
8VSB QPSK, 16QAM,
64QAM, 256QAM
2VSB, 4VSB, 8VSB,
16VSB, 32VSB,
TYPE Single carrier Multi-carrier
OFDM
Multi-carrier
SC-FDMA
Single side band
Number of
Sub-carriers
1 1K, 2K, 4K, 8K, 16K, 32K 1K, 2K, 4K, 8K
GUARD Time
Relative to symbol length
- 1/4,19/128,1/8, 19/256,
1/16,
1/32, 1/128
1/5.6
Data Frame length (ms) 48,38 Not fixed 48,38
26. 0 5 10 15
-6
-5
-4
-3
-2
-1
0
PAPR in dB
CCDF
CCDF of TX signal
CCDF in baseband
CCDF in passband
Spectrum and CCDF of PARP for
SC-FDMA signal (Wavelet filter 1)
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PAPR= 7.5 dB
PAPR=5.5 dB
0.5 0.52 0.54 0.56 0.58 0.6 0.62 0.64 0.66 0.68
-100
-90
-80
-70
-60
-50
-40
-30
Normalized Frequency (rad/sample)
Power/frequency(dB/rad/sample)
Spectrum of TXIF signal after IF filter
65 dB
27. Spectrum and CCDF of PARP for
SC-FDMA signal (Wavelet filter 2)
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0 5 10 15
-6
-5
-4
-3
-2
-1
0
PAPR in dB
CCDF
CCDF of TX signal
CCDF in baseband
CCDF in passband
PAPR=6 dB
PAPR=3.5 dB
0.54 0.56 0.58 0.6 0.62 0.64 0.66 0.68
-100
-90
-80
-70
-60
-50
-40
-30
Normalized Frequency (rad/sample)
Power/frequency(dB/rad/sample)
Spectrum of TX IF signal after IF filter
28. Spectrum and CCDF of PARP for
SC-FDMA signal (Wavelet filter 3)
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0 5 10 15
-6
-5
-4
-3
-2
-1
0
PAPR in dB
CCDF
CCDF of TX signal
CCDF in baseband
CCDF in passband
PAPR=5.3 dB
PAPR=2.5 dB
0.55 0.6 0.65 0.7 0.75
-90
-80
-70
-60
-50
-40
-30
Normalized Frequency (rad/sample)
Power/frequency(dB/rad/sample)
Spectrum of TXIF signal after IF filter
29. Output signal of SC-FDMA transmitter
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0 2 4 6 8 10 12 14
x 10
5
-0.1
-0.08
-0.06
-0.04
-0.02
0
0.02
0.04
0.06
0.08
0.1
Tx IF signal
