Thứ Bảy, 7 tháng 2, 2015

Bit Rate Calculation for DVB-T,DVB-C


Another way to look at this :

DVB-T modulator maximum play rate depends on code rate, constellation, guard interval, bandwidth.
The maximum bit rate can be calculated as below.

Tbandwidth = {6,000,000, 7,000,000, 8,000,000} in Hz for 6MHz, 7MHz, 8MHz
Tcode_rate = {1/2, 2/3, 3/4, 5/6, 7/8}
TConstellation = {2, 4, 6} <- QPSK = 2, 16QAM=4, 64QAM = 6
TGuardInterval = {4/5, 8/9, 16/17, 32/33}, 1/4 = 4/5, 1/8 = 8/9, 1/16 => 16/17, 1/32 => 32/33}
2K/8K mode does not matter

Maximum bit rate = 1512 / 2048 * 188 / 204 * 64 / 56 * TBandwidth * Tcode_rate * TConstellation * TGuardInterval (bps)
= 423 / 544 * TBandwidth * Tcode_rate * TConstellation * TGuardInterval (bps)

B (DVB-C) = 6.875 * 188* 6/204 = 38.014

B (DVB-T) = 6.75 * 188*6*7/8*32/33*204 = 31.668

Bit Rate Calculation for DVB-T

8 MHz DVB-T COFDM Payload Data Rate

Useable Symbol Rate

6.75000
Msym/s

OFDM Bandwidth

7.61161
MHz

Modulation
Type

Code
Rate

Guard Interval

1/4

1/8

1/16

1/32


QPSK
2
Bits/sym



1/2

4.976

5.529

5.855

6.032

2/3

6.635

7.373

7.806

8.043

3/4

7.465

8.294

8.782

9.048

5/6

8.294

9.216

9.758

10.053

7/8

8.709

9.676

10.246

10.556


16-QAM
4
Bits/sym



1/2

9.953

11.059

11.709

12.064

2/3

13.271

14.745

15.612

16.086

3/4

14.929

16.588

17.564

18.096

5/6

16.588

18.431

19.516

20.107

7/8

17.418

19.353

20.491

21.112


64-QAM
6
Bits/sym



1/2

14.929

16.588

17.564

18.096

2/3

19.906

22.118

23.419

24.128

3/4

22.394

24.882

26.346

27.144

5/6

24.882

27.647

29.273

30.16

7/8

26.126

29.029

30.737

31.668

Payload Data Rates Mbit/s

Sys
Mode

Symbol
Time (us)

Guard Interval Length (us)

1/4

1/8

1/16

1/32

2K

224

56

28

14

7

8K

896

224

112

56

28

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