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sdrangel/modemm17/M17Modulator.h
Jon Beniston 967d9e1131 Update packet mode to follow current spec
2023-11-15 15:38:01 +00:00

592 lines
17 KiB
C++
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#pragma once
#include <QDebug>
#include <QString>
#include "FirFilter.h"
#include "LinkSetupFrame.h"
#include "CRC16.h"
#include "Convolution.h"
#include "PolynomialInterleaver.h"
#include "M17Randomizer.h"
#include "Util.h"
#include "Golay24.h"
#include "Trellis.h"
#include <array>
#include <atomic>
#include <chrono>
#include <cstdint>
#include <future>
#include <iostream>
#include <memory>
#include "export.h"
namespace modemm17
{
/**
* Common routines extracted from the original asynchronous M17 modulator.
* It is used to produce the various symbol sequences but modulation is handled at
* upper level.
*/
struct MODEMM17_API M17Modulator
{
public:
using symbols_t = std::array<int8_t, 192>; // One frame of symbols.
using baseband_t = std::array<int16_t, 1920>; // One frame of baseband data @ 48ksps
using bitstream_t = std::array<uint8_t, 48>; // M17 frame of bits (in bytes).
using lsf_t = std::array<uint8_t, 30>; // Link setup frame bytes.
using lich_segment_t = std::array<uint8_t, 96>; // Golay-encoded LICH bits.
using lich_t = std::array<lich_segment_t, 6>; // All LICH segments.
using audio_frame_t = std::array<int16_t, 320>;
using codec_frame_t = std::array<uint8_t, 16>;
using payload_t = std::array<uint8_t, 34>; // Bytes in the payload of a data frame.
using frame_t = std::array<uint8_t, 46>; // M17 frame (without sync word).
using packet_t = std::array<uint8_t, 25>; // Packet payload
static const std::array<uint8_t, 2> SYNC_WORD;
static const std::array<uint8_t, 2> LSF_SYNC_WORD;
static const std::array<uint8_t, 2> STREAM_SYNC_WORD;
static const std::array<uint8_t, 2> PACKET_SYNC_WORD;
static const std::array<uint8_t, 2> BERT_SYNC_WORD;
static const std::array<uint8_t, 2> EOT_SYNC;
static int8_t bits_to_symbol(uint8_t bits)
{
switch (bits)
{
case 0: return 1;
case 1: return 3;
case 2: return -1;
case 3: return -3;
}
return 0;
}
template <typename T, size_t N>
static std::array<int8_t, N / 2> bits_to_symbols(const std::array<T, N>& bits)
{
std::array<int8_t, N / 2> result;
size_t index = 0;
for (size_t i = 0; i != N; i += 2)
{
result[index++] = bits_to_symbol((bits[i] << 1) | bits[i + 1]);
}
return result;
}
template <typename T, size_t N>
static std::array<int8_t, N * 4> bytes_to_symbols(const std::array<T, N>& bytes)
{
std::array<int8_t, N * 4> result;
size_t index = 0;
for (auto b : bytes)
{
for (size_t i = 0; i != 4; ++i)
{
result[index++] = bits_to_symbol(b >> 6);
b <<= 2;
}
}
return result;
}
/*
* Converts a suite of 192 symbols (from the 384 bits of a frame) into 1920 16 bit integer samples to be used
* in the final FM modulator (baseband). Sample rate is expected to be 48 kS/s. This is the original 48 kS/s
* 16 bit audio output of the modulator.
*/
template <size_t N>
std::array<int16_t, N*10> symbols_to_baseband(std::array<int8_t, N> symbols, bool invert = false)
{
std::array<int16_t, N*10> baseband;
baseband.fill(0);
for (size_t i = 0; i != symbols.size(); ++i) {
baseband[i * 10] = symbols[i];
}
for (auto& b : baseband) {
b = rrc(b) * 7168.0 * (invert ? -1.0 : 1.0);
}
return baseband;
}
std::array<int8_t, 368> make_lsf(lsf_t& lsf, bool streamElsePacket = false)
{
lsf.fill(0);
M17Randomizer randomizer;
PolynomialInterleaver<45, 92, 368> interleaver;
CRC16 crc(0x5935, 0xFFFF);
auto rit = std::copy(dest_.begin(), dest_.end(), lsf.begin());
std::copy(source_.begin(), source_.end(), rit);
lsf[12] = can_ >> 1;
lsf[13] = (streamElsePacket ? 5 : 2) | ((can_ & 1) << 7);
if (gnss_on_)
{
lsf[13] |= (1<<5);
std::copy(gnss_.begin(), gnss_.end(), &lsf[14]);
}
crc.reset();
for (size_t i = 0; i != 28; ++i) {
crc(lsf[i]);
}
std::array<uint8_t, 2> checksum = crc.get_bytes();
lsf[28] = checksum[0];
lsf[29] = checksum[1];
std::array<uint8_t, 488> encoded;
size_t index = 0;
uint32_t memory = 0;
for (auto b : lsf)
{
for (size_t i = 0; i != 8; ++i)
{
uint32_t x = (b & 0x80) >> 7;
b <<= 1;
memory = modemm17::update_memory<4>(memory, x);
encoded[index++] = modemm17::convolve_bit(031, memory);
encoded[index++] = modemm17::convolve_bit(027, memory);
}
}
// Flush the encoder.
for (size_t i = 0; i != 4; ++i)
{
memory = modemm17::update_memory<4>(memory, 0);
encoded[index++] = modemm17::convolve_bit(031, memory);
encoded[index++] = modemm17::convolve_bit(027, memory);
}
std::array<int8_t, 368> punctured;
auto size = puncture<488, 368, 61>(encoded, punctured, P1);
if (size != 368) {
qWarning() << "modemm17::M17Modulator::make_lsf: incorrect size (not 368)" << size;
}
interleaver.interleave(punctured);
randomizer.randomize(punctured);
return punctured;
}
static lich_segment_t make_lich_segment(std::array<uint8_t, 5> segment, uint8_t segment_number)
{
lich_segment_t result;
uint16_t tmp;
uint32_t encoded;
tmp = segment[0];
tmp <<= 4;
tmp |= ((segment[1] >> 4) & 0x0F);
// tmp = segment[0] << 4 | ((segment[1] >> 4) & 0x0F);
encoded = modemm17::Golay24::encode24(tmp);
for (size_t i = 0; i != 24; ++i)
{
result[i] = (encoded & (1 << 23)) != 0 ? 1 : 0;
encoded <<= 1;
}
tmp = segment[1] & 0x0F;
tmp <<= 8;
tmp |= segment[2];
// tmp = ((segment[1] & 0x0F) << 8) | segment[2];
encoded = modemm17::Golay24::encode24(tmp);
for (size_t i = 24; i != 48; ++i)
{
result[i] = (encoded & (1 << 23)) != 0 ? 1 : 0;
encoded <<= 1;
}
tmp = segment[3];
tmp <<= 4;
tmp |= ((segment[4] >> 4) & 0x0F);
// tmp = segment[3] << 4 | ((segment[4] >> 4) & 0x0F);
encoded = modemm17::Golay24::encode24(tmp);
for (size_t i = 48; i != 72; ++i)
{
result[i] = (encoded & (1 << 23)) != 0 ? 1 : 0;
encoded <<= 1;
}
tmp = segment[4] & 0x0F;
tmp <<= 8;
tmp |= (segment_number << 5);
// tmp = ((segment[4] & 0x0F) << 8) | (segment_number << 5);
encoded = modemm17::Golay24::encode24(tmp);
for (size_t i = 72; i != 96; ++i)
{
result[i] = (encoded & (1 << 23)) != 0 ? 1 : 0;
encoded <<= 1;
}
return result;
}
static std::array<int8_t, 272> make_stream_data_frame(uint16_t frame_number, const codec_frame_t& payload)
{
std::array<uint8_t, 18> data; // FN, payload = 2 + 16;
data[0] = uint8_t((frame_number >> 8) & 0xFF);
data[1] = uint8_t(frame_number & 0xFF);
std::copy(payload.begin(), payload.end(), data.begin() + 2);
std::array<uint8_t, 296> encoded;
size_t index = 0;
uint32_t memory = 0;
for (auto b : data)
{
for (size_t i = 0; i != 8; ++i)
{
uint32_t x = (b & 0x80) >> 7;
b <<= 1;
memory = modemm17::update_memory<4>(memory, x);
encoded[index++] = modemm17::convolve_bit(031, memory);
encoded[index++] = modemm17::convolve_bit(027, memory);
}
}
// Flush the encoder.
for (size_t i = 0; i != 4; ++i)
{
memory = modemm17::update_memory<4>(memory, 0);
encoded[index++] = modemm17::convolve_bit(031, memory);
encoded[index++] = modemm17::convolve_bit(027, memory);
}
std::array<int8_t, 272> punctured;
auto size = modemm17::puncture<296, 272, 12>(encoded, punctured, modemm17::P2);
if (size != 272) {
qWarning() << "modemm17::M17Modulator::make_stream_data_frame: incorrect size (not 272)" << size;
}
return punctured;
}
std::array<int8_t, 368> make_packet_frame(
uint8_t packet_number,
int packet_size,
bool last_packet,
const std::array<uint8_t, 25> packet
)
{
M17Randomizer randomizer;
PolynomialInterleaver<45, 92, 368> interleaver;
std::array<uint8_t, 26> packet_assembly;
packet_assembly.fill(0);
std::copy(packet.begin(), packet.begin() + packet_size, packet_assembly.begin());
if (packet_number == 0) {
crc_.reset();
}
for (int i = 0; i < packet_size; i++) {
crc_(packet[i]);
}
if (last_packet)
{
packet_assembly[25] = 0x80 | ((packet_size+2)<<2); // sent packet size includes CRC
packet_assembly[packet_size] = crc_.get_bytes()[0];
packet_assembly[packet_size+1] = crc_.get_bytes()[1];
}
else
{
packet_assembly[25] = (packet_number<<2);
}
std::array<uint8_t, 420> encoded;
size_t index = 0;
uint32_t memory = 0;
uint8_t b;
for (int bi = 0; bi < 25; bi++)
{
b = packet_assembly[bi];
for (size_t i = 0; i != 8; ++i)
{
uint32_t x = (b & 0x80) >> 7;
b <<= 1;
memory = modemm17::update_memory<4>(memory, x);
encoded[index++] = modemm17::convolve_bit(031, memory);
encoded[index++] = modemm17::convolve_bit(027, memory);
}
}
b = packet_assembly[25];
for (size_t i = 0; i != 6; ++i)
{
uint32_t x = (b & 0x80) >> 7;
b <<= 1;
memory = modemm17::update_memory<4>(memory, x);
encoded[index++] = modemm17::convolve_bit(031, memory);
encoded[index++] = modemm17::convolve_bit(027, memory);
}
// Flush the encoder.
for (size_t i = 0; i != 4; ++i)
{
memory = modemm17::update_memory<4>(memory, 0);
encoded[index++] = modemm17::convolve_bit(031, memory);
encoded[index++] = modemm17::convolve_bit(027, memory);
}
std::array<int8_t, 368> punctured;
auto size = puncture<420, 368, 8>(encoded, punctured, P3);
if (size != 368) {
qWarning() << "modemm17::M17Modulator::make_packet_frame: incorrect size (not 368)" << size;
}
interleaver.interleave(punctured);
randomizer.randomize(punctured);
return punctured;
}
static std::array<int8_t, 368> make_bert_frame(PRBS9& prbs)
{
std::array<uint8_t, 25> data; // 24.6125 bytes, 197 bits
// Generate the data (24*8 = 192 bits).
for (size_t i = 0; i != data.size() - 1; ++i)
{
uint8_t byte = 0;
for (int i = 0; i != 8; ++i)
{
byte <<= 1;
byte |= prbs.generate();
}
data[i] = byte;
}
// Generate the data (last 5 bits).
uint8_t byte = 0;
for (int i = 0; i != 5; ++i)
{
byte <<= 1;
byte |= prbs.generate();
}
byte <<= 3;
data[24] = byte;
// Convolutional encode
std::array<uint8_t, 402> encoded;
size_t index = 0;
uint32_t memory = 0;
// 24*8 = 192 first bits
for (size_t i = 0; i != data.size() - 1; ++i)
{
auto b = data[i];
for (size_t j = 0; j != 8; ++j)
{
uint32_t x = (b & 0x80) >> 7;
b <<= 1;
memory = update_memory<4>(memory, x);
encoded[index++] = convolve_bit(031, memory);
encoded[index++] = convolve_bit(027, memory);
}
}
// last 5 bits
auto b = data[24];
for (size_t j = 0; j != 5; ++j)
{
uint32_t x = (b & 0x80) >> 7;
b <<= 1;
memory = update_memory<4>(memory, x);
encoded[index++] = convolve_bit(031, memory);
encoded[index++] = convolve_bit(027, memory);
}
// Flush the encoder.
for (size_t i = 0; i != 4; ++i)
{
memory = update_memory<4>(memory, 0);
encoded[index++] = convolve_bit(031, memory);
encoded[index++] = convolve_bit(027, memory);
}
std::array<int8_t, 368> punctured;
auto size = puncture<402, 368, 12>(encoded, punctured, P2);
if (size != 368) {
qWarning() << "modemm17::M17Modulator::make_bert_frame: incorrect size (not 368)" << size;
}
return punctured;
}
static void interleave_and_randomize(std::array<int8_t, 368>& punctured)
{
M17Randomizer randomizer;
PolynomialInterleaver<45, 92, 368> interleaver;
interleaver.interleave(punctured);
randomizer.randomize(punctured);
}
M17Modulator(const std::string& source, const std::string& dest = "") :
source_(encode_callsign(source)),
dest_(encode_callsign(dest)),
can_(10),
rrc(makeFirFilter(rrc_taps)),
crc_(0x5935, 0xFFFF)
{
gnss_.fill(0);
gnss_on_ = false;
}
/**
* Set the source identifier (callsign) for the transmitter.
*/
void source(const std::string& callsign) {
source_ = encode_callsign(callsign);
}
/**
* Set the destination identifier for the transmitter. A blank value is
* interpreted as the broadcast address. This is the default.
*/
void dest(const std::string& callsign) {
dest_ = encode_callsign(callsign);
}
/**
* Set the Channel Access Number (0..15)
*/
void can(uint8_t can) {
can_ = can & 0xF;
}
/**
* Set GNSS data
*/
void set_gnss(float lat, float lon, float alt)
{
gnss_ = LinkSetupFrame::encode_gnss(lat, lon, alt);
gnss_on_ = true;
}
/**
* Reset GNSS data
*/
void reset_gnss()
{
gnss_.fill(0);
gnss_on_ = false;
}
private:
LinkSetupFrame::encoded_call_t source_;
LinkSetupFrame::encoded_call_t dest_;
LinkSetupFrame::gnss_t gnss_;
bool gnss_on_;
uint8_t can_;
BaseFirFilter<150> rrc;
static const std::array<float, 150> rrc_taps;
CRC16 crc_;
static LinkSetupFrame::encoded_call_t encode_callsign(std::string callsign)
{
LinkSetupFrame::encoded_call_t encoded_call = {0xff,0xff,0xff,0xff,0xff,0xff};
if (callsign.empty() || callsign.size() > 9) {
return encoded_call;
}
modemm17::LinkSetupFrame::call_t call;
call.fill(0);
std::copy(callsign.begin(), callsign.end(), call.begin());
encoded_call = LinkSetupFrame::encode_callsign(call);
return encoded_call;
}
template <typename T, size_t N>
static std::array<T, N * 2 + 1> conv_encode(std::array<T, N> data)
{
std::array<T, N * 2 + 1> result;
uint8_t bit_index = 0;
uint8_t byte_index = 0;
uint8_t tmp = 0;
uint32_t memory = 0;
for (auto b : data)
{
for (size_t i = 0; i != 8; ++i)
{
uint32_t x = (b & 0x80) >> 7;
b <<= 1;
memory = update_memory<4>(memory, x);
tmp = (tmp << 1) | convolve_bit(031, memory);
tmp = (tmp << 1) | convolve_bit(027, memory);
bit_index += 2;
if (bit_index == 8)
{
bit_index = 0;
result[byte_index++] = tmp;
tmp = 0;
}
}
}
// Flush the encoder.
for (size_t i = 0; i != 4; ++i)
{
memory = update_memory<4>(memory, 0);
tmp = (tmp << 1) | convolve_bit(031, memory);
tmp = (tmp << 1) | convolve_bit(027, memory);
bit_index += 2;
if (bit_index == 8)
{
bit_index = 0;
result[byte_index++] = tmp;
tmp = 0;
}
}
// Frame may not end on a byte boundary.
if (bit_index != 0)
{
while (bit_index++ != 8) {
tmp <<= 1;
}
result[byte_index] = tmp;
}
return result;
}
};
} // modemm17
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