Upload
michelle-gardner
View
225
Download
7
Tags:
Embed Size (px)
Citation preview
An Initial Study on the Convergence of DVB-H and DTMB
in the Physical Layer
Feng Yang, Jian Song, Changyong Pan,Hui Yang, Kewu Peng, Jun Wang,
Zhixing Yang Dept. EE Tsinghua University
23.08.2007 ChinaCom2007 ShangHai 2
Brief Introduction of MING-T
MING-T = Multistandard Integrated Network convergence for Global Mobile and Broadcast Technologies
Main Objectives of the Project—…— Incorporate both DVB-H and DTMB into the multi-
standard framework.— ...
from project management handbook
Convergence of DVB-H and DTMB
23.08.2007 ChinaCom2007 ShangHai 3
Brief Introduction of MING-T (Cont’d)
— Prototype using two demodulators
— However, single chip is more attractive!
Tuner Tuner
DVB-Hdemodulator
DTMBdemodulator
DVB-HDriver/API
DTMBDriver/API
Middlewave
ESG Player
Laptop/PDA
Receiver
23.08.2007 ChinaCom2007 ShangHai 4
Comparisons of DTMB & DVB-H
Randomization
—Similarities The same PRBS, the same initial state
—Differences Sync byte: DVB (untouched) DTMB (Randomized) Reset: DVB (every 8 TS) DTMB (every signal frame)
23.08.2007 ChinaCom2007 ShangHai 5
Comparisons of DTMB & DVB-H (Cont’d)
Forward Error Correcting (FEC) coding—DVB-H : RS + Convolutional code
RS(204,188) derived from RS(255,239) Convolutional codes : 1/2, 2/3, 3/4, 5/6, 7/8
—DTMB : BCH + LDPC BCH(762,752) derived from BCH(1023,1013) LDPC with 3 code rates as the inner code
23.08.2007 ChinaCom2007 ShangHai 6
Comparisons of DTMB & DVB-H (Cont’d)
Interleaving —Convolutional interleaving
DTMB: B=52 M=240/720 DVB-H: B=12 M=17
1×M
2×M
3×M
…………………………………………
(B-1)×M
0 0
11
2 2
B-1
3 3
B-1
1×M
2×M
3×M
(B-1)×M
B-1 B-1
00
Interleaving Deinterleaving
…………………………………………
B-2
B-3
B-4 B-4
B-3
B-2
23.08.2007 ChinaCom2007 ShangHai 7
Comparisons of DTMB & DVB-H (Cont’d)
Interleaving —Block interleaving
DVB-H in-depth interleaver (8k)
DTMB frequency interleaver (4k)
23.08.2007 ChinaCom2007 ShangHai 8
Comparisons of DTMB & DVB-H (Cont’d)
Frame Structure
—C-OFDM : Process in Frequency domain—Parameter refresh : 1ms; Signal lock : 100ms
—TDS-OFDM : Process in Time/Frequency domain—Channel estimation : 0.56 ms; Signal lock : 5ms
PN Data PN Data
Signal Frame 500μsTDS-OFDM
Copy
CP Data+Pilot CP Data+Pilot
Copy
OFDM Symbol
C-OFDM
23.08.2007 ChinaCom2007 ShangHai 9
Comparisons of DTMB & DVB-H (Cont’d)
Summary —TDS-OFDM vs C-OFDM, Using PN brings
Higher spectrum efficiency Faster channel synchronization
—BCH+LDPC vs RS+Convolutional code for better coding gain, therefore, lower Eb/N0 required for the same BER
Larger coverage Better availability
—Long time-domain interleaver Better immunization to impulsive noise
23.08.2007 ChinaCom2007 ShangHai 10
Receiver Algorithms & Convergence Considerations
Synchronization—Correlation approach
DTMB: correlating with the known PN sequence DVB-H: guard interval correlation (pre-FFT syn.)
DownConverter
ADCCorrelator&memory of bigger size
RF
Channel estimation& equalization
?
Synchronization
?
Block De-interleaver
? ...
ConvolutionalDe-interleaver
?
FEC Decoder
De-scrambler
TS
23.08.2007 ChinaCom2007 ShangHai 11
Receiver Algorithms & Convergence Considerations (Cont’d)
Channel estimation & equalization—DVB-H: 8k FFT—DTMB: 8k FFT (channel estimation)
3780 FFT (equalization)
Correlator&memory of bigger size
RF
Channel estimation& equalization
8K FFT3780 FFT
Synchronization
?
Block De-interleaver
? ...
ConvolutionalDe-interleaverTS
DownConverter
ADC
?
FEC Decoder
De-scrambler
23.08.2007 ChinaCom2007 ShangHai 12
Receiver Algorithms & Convergence Considerations (Cont’d)
De-interleaving—Convolutional de-interleaver
DTMB: B=52, M=720 DVB-H: B=12, M=17
—Block de-interleaver DVB-H: 8K DTMB: 4K
Correlator&memory of bigger size
RF
Channel estimation& equalization
8K FFT3780 FFT
Synchronization
8K
Block De-interleaver
B=52M=720
...
ConvolutionalDe-interleaverTS
DownConverter
ADC
?
FEC Decoder
De-scrambler
23.08.2007 ChinaCom2007 ShangHai 13
Receiver Algorithms & Convergence Considerations (Cont’d)
FEC decoder—DVB-H
Convolutional code: Viterbi Algorithm (VA) RS code: syndrome computation, key-equation solver,
Chien search and error evaluator—DTMB (LDPC)
Hard-decision : Bit-Flipping (BF) Soft-decision : Sum-Product Algorithm (SPA)
FEC Decoder
LDPC Dec.(DTMB)
VA+
RS Dec.(DVB-H)
Thank you for your attention!
Email:[email protected]