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skew pilot and reserved tones

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This commit is contained in:
Ahmet Inan 2025-07-01 08:26:28 +02:00
commit 838155c063
2 changed files with 16 additions and 9 deletions
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18
decode.cc
View file

@ -59,6 +59,7 @@ struct Decoder
static const int reserved_tones = 32;
static const int data_tones = 256;
static const int block_length = 10;
static const int block_skew = 3;
static const int pilot_offset = 4;
static const int reserved_offset = 9;
static const int tone_count = data_tones + pilot_tones + reserved_tones;
@ -324,13 +325,14 @@ struct Decoder
seq1.reset();
hadamardenc(mode, oper_mode);
}
int poff = (block_skew * j + pilot_offset) % block_length;
for (int i = 0; i < pilot_tones; ++i)
tone[block_length*i+pilot_offset] *= nrz(seq1()) * mode[i];
tone[block_length*i+poff] *= nrz(seq1()) * mode[i];
for (int i = 0; i < tone_count; ++i)
demod[tone_count*j+i] = demod_or_erase(tone[i], chan[i]);
for (int i = 0; i < pilot_tones; ++i) {
index[i] = tone_off + block_length * i + pilot_offset;
phase[i] = arg(demod[tone_count*j+block_length*i+pilot_offset]);
index[i] = tone_off + block_length * i + poff;
phase[i] = arg(demod[tone_count*j+block_length*i+poff]);
}
tse.compute(index, phase, pilot_tones);
//std::cerr << "Theil-Sen slope = " << tse.slope() << std::endl;
@ -338,7 +340,7 @@ struct Decoder
for (int i = 0; i < tone_count; ++i)
demod[tone_count*j+i] *= DSP::polar<value>(1, -tse(i+tone_off));
for (int i = 0; i < tone_count; ++i)
if (i % block_length == pilot_offset)
if (i % block_length == poff)
chan[i] = tone[i];
else
chan[i] *= DSP::polar<value>(1, tse(i+tone_off));
@ -348,9 +350,11 @@ struct Decoder
std::cerr << "Es/N0 (dB):";
value sp = 0, np = 0;
for (int j = 0, k = 0; j < symbol_count; ++j) {
int poff = (block_skew * j + pilot_offset) % block_length;
int roff = (block_skew * j + reserved_offset) % block_length;
for (int i = 0; i < pilot_tones; ++i) {
cmplx hard(1, 0);
cmplx error = demod[tone_count*j+block_length*i+pilot_offset] - hard;
cmplx error = demod[tone_count*j+block_length*i+poff] - hard;
sp += norm(hard);
np += norm(error);
}
@ -361,9 +365,9 @@ struct Decoder
if (std::is_same<code_type, int8_t>::value && precision > 32)
precision = 32;
for (int i = 0; i < tone_count; ++i) {
if (i % block_length == pilot_offset)
if (i % block_length == poff)
continue;
if (i % block_length == reserved_offset)
if (i % block_length == roff)
continue;
mod_soft(perm+k, demod[tone_count*j+i], precision);
k += mod_bits;

7
encode.cc
View file

@ -40,6 +40,7 @@ struct Encoder
static const int reserved_tones = 32;
static const int tone_count = data_tones + pilot_tones + reserved_tones;
static const int block_length = 10;
static const int block_skew = 3;
static const int pilot_offset = 4;
static const int reserved_offset = 9;
DSP::WritePCM<value> *pcm;
@ -354,10 +355,12 @@ struct Encoder
shuffle(perm, code);
CODE::MLS seq1(mls1_poly);
for (int j = 0, k = 0; j < symbol_count; ++j) {
int poff = (block_skew * j + pilot_offset) % block_length;
int roff = (block_skew * j + reserved_offset) % block_length;
for (int i = 0, m = 0; i < tone_count; ++i) {
if (i % block_length == pilot_offset) {
if (i % block_length == poff) {
tone[i] = nrz(seq1()) * mode[m++];
} else if (i % block_length == reserved_offset) {
} else if (i % block_length == roff) {
tone[i] = 0;
} else {
tone[i] = mod_map(perm+k);