I'm currently developing DVB-T transmitter on FPGA platform. DVB-T standard (ETSI EN 300 744 v1.6.1) says that in 16-QAM, non-hierarchical transmission mode, bit interleaver uses following interleavers: I0: H0(w) = w I1: H1(w) = (w + 63) mod 126 I2: H2(w) = (w + 105) mod 126 I3: H3(w) = (w + 42) mod 126 I've tested it both using a reference model (found here: http://dante.diei.unipg.it/~baruffa/dvbt/index.php) and in hardware FPGA device, and came to a conclusion that in fact 16-QAM mode uses interleavers I0, I1, I4 and I5, despite what is written in the standard. I4: H4(w) = (w + 21) mod 126 I5: H5(w) = (w + 84) mod 126 I've managed to successfully receive and decode such signal using commercial (R&S) TV signals analyser. It didn't work when using I2 and I3. I want to do 64-QAM mode next and I would like to know what is the right order of interleavers without reverse engineering it from reference model by trial and error. I would also like to base my work on dvb-t standard documents. My question is: am I reading the standard wrong? why is there such a difference?

# DVB-T Bit interleaver problem

Started by ●June 1, 2012

Reply by ●June 1, 20122012-06-01

On Jun 1, 9:35�am, "DruidNei" <DruidNei@n_o_s_p_a_m.gmail.com> wrote:> I'm currently developing DVB-T transmitter on FPGA platform. DVB-T standard > (ETSI EN 300 744 v1.6.1) says that in 16-QAM, non-hierarchical transmission > mode, bit interleaver uses following interleavers: > I0: H0(w) = w > I1: H1(w) = (w + 63) mod 126 > I2: H2(w) = (w + 105) mod 126 > I3: H3(w) = (w + 42) mod 126 > > I've tested it both using a reference model (found here:http://dante.diei.unipg.it/~baruffa/dvbt/index.php) and in hardware FPGA > device, and came to a conclusion that in fact 16-QAM mode uses interleavers > I0, I1, I4 and I5, despite what is written in the standard. > > I4: H4(w) = (w + 21) mod 126 > I5: H5(w) = (w + 84) mod 126 > > I've managed to successfully receive and decode such signal using > commercial (R&S) TV signals analyser. It didn't work when using I2 and I3. > > I want to do 64-QAM mode next and I would like to know what is the right > order of interleavers without reverse engineering it from reference model > by trial and error. I would also like to base my work on dvb-t standard > documents. > > My question is: am I reading the standard wrong? why is there such a > difference?There may be an issue of interpretation here. Note that 21 + 105 = 126 and 42 + 84 = 126. So, if x = w + 21 mod 126, then w = x - 21 mod 126 = x + 105 mod 126, and so on. With x = w + 63 mod 126, w = x - 63 mod 126 = x + 63 mod 126. Dilip Sarwate

Reply by ●June 2, 20122012-06-02