How to calculate bit rate (physical layer) in ISDB-T (OFDM system)?

Question

I was looking at OFDM (ISDB -T) specification. I couldn't figure out how they get the bit rate of 16.851 Mbps by having the following information?

symbol length: 1.008 ms
carrier interval: 0.992 kHz
GI ratio: 1/8
G.I. length: 0.126 ms
Bandwidth: 428.57 kHz × 12
modulation scheme: 64 QAM
time-interleaving: 215 ms
sub carriers: 432 × 12 ＋ 1
Forward Error Correction ¾

The way I understand is that: there are 64 symbols in 64-QAM and each symbol could represent 6 bits. we have 432 × 12 ＋ 1 carriers. meaning that we can carry (432 × 12 ＋ 1) * 64 * 6 = 1991040 bits, since the FEC is 3/4, 1991040 * 3/4 = 1493280.0 , hmm it seems so far from 16.851 Mbps.

You've got 12 bands, but each of these bands has up to 432 OFDM subcarriers. So, your spec isn't quite sufficient — Marcus Müller, Jun 09 '21 at 11:31
@MarcusMüller Hi Marcus, there are 432 × 12 ＋ 1 number of sub carriers — TheFirefly, Jun 09 '21 at 11:33
so, now this looks pretty sensible, wouldn't you say? How many bits can you put into 432 subcarriers if each of these subcarriers carries a 64-QAM symbol? — Marcus Müller, Jun 09 '21 at 11:35
@MarcusMüller what I understand is we can carry 6 bits per symbol. hmm, but i just couldn't work out the same bit rate. There is something I am missing — TheFirefly, Jun 09 '21 at 11:38
so, maybe add your calculation to your question, and we can have a look at it! — Marcus Müller, Jun 09 '21 at 11:49
@MarcusMüller I think there are few places that I don't quite understand. :) — TheFirefly, Jun 09 '21 at 12:19
that's the number of bits you transport – but in which time? — Marcus Müller, Jun 09 '21 at 12:24
@MarcusMüller Is it correct to understand that it is the number of bits we transport in 1.008ms ? but then we get a huge number 1493280 / 1.008 * 1000 — TheFirefly, Jun 09 '21 at 12:34

How to calculate bit rate (physical layer) in ISDB-T (OFDM system)?

0 Answers0