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sdrangel/plugins/channelrx/demoddatv/ldpctool/qam.h
f4exb dc8f3ee9d9 DATV: soft LDPC (1)
2021-03-07 00:36:48 +01:00

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/*
Quadrature amplitude modulation
Copyright 2018 Ahmet Inan <xdsopl@gmail.com>
*/
#ifndef QAM_HH
#define QAM_HH
namespace ldpctool {
template <int NUM, typename TYPE, typename CODE>
struct QuadratureAmplitudeModulation;
template <typename TYPE, typename CODE>
struct QuadratureAmplitudeModulation<16, TYPE, CODE>
{
static const int NUM = 16;
static const int BITS = 4;
typedef TYPE complex_type;
typedef typename TYPE::value_type value_type;
typedef CODE code_type;
static constexpr value_type FAC = 1.0540925533894596;
static constexpr value_type RCP = 3 * FAC;
static constexpr value_type AMP = 1 / RCP;
static constexpr value_type DIST = 2 * AMP;
static constexpr value_type amp(int i)
{
return AMP * i;
}
static code_type quantize(value_type precision, value_type value)
{
value *= DIST * precision;
if (std::is_integral<code_type>::value)
value = std::nearbyint(value);
if (std::is_same<code_type, int8_t>::value)
value = std::min<value_type>(std::max<value_type>(value, -128), 127);
return value;
}
static void hard(code_type *b, complex_type c)
{
b[0] = c.real() < amp(0) ? code_type(-1) : code_type(1);
b[1] = c.imag() < amp(0) ? code_type(-1) : code_type(1);
b[2] = std::abs(c.real()) < amp(2) ? code_type(-1) : code_type(1);
b[3] = std::abs(c.imag()) < amp(2) ? code_type(-1) : code_type(1);
}
static void soft(code_type *b, complex_type c, value_type precision)
{
b[0] = quantize(precision, c.real());
b[1] = quantize(precision, c.imag());
b[2] = quantize(precision, std::abs(c.real())-amp(2));
b[3] = quantize(precision, std::abs(c.imag())-amp(2));
}
static complex_type map(code_type *b)
{
return AMP * complex_type(
b[0]*(b[2]+value_type(2)),
b[1]*(b[3]+value_type(2))
);
}
};
template <typename TYPE, typename CODE>
struct QuadratureAmplitudeModulation<64, TYPE, CODE>
{
static const int NUM = 64;
static const int BITS = 6;
typedef TYPE complex_type;
typedef typename TYPE::value_type value_type;
typedef CODE code_type;
static constexpr value_type FAC = 0.9258200997725516;
static constexpr value_type RCP = 7 * FAC;
static constexpr value_type AMP = 1 / RCP;
static constexpr value_type DIST = 2 * AMP;
static constexpr value_type amp(int i)
{
return AMP * i;
}
static code_type quantize(value_type precision, value_type value)
{
value *= DIST * precision;
if (std::is_integral<code_type>::value)
value = std::nearbyint(value);
if (std::is_same<code_type, int8_t>::value)
value = std::min<value_type>(std::max<value_type>(value, -128), 127);
return value;
}
static void hard(code_type *b, complex_type c)
{
b[0] = c.real() < amp(0) ? code_type(-1) : code_type(1);
b[1] = c.imag() < amp(0) ? code_type(-1) : code_type(1);
b[2] = std::abs(c.real()) < amp(4) ? code_type(-1) : code_type(1);
b[3] = std::abs(c.imag()) < amp(4) ? code_type(-1) : code_type(1);
b[4] = std::abs(std::abs(c.real())-amp(4)) < amp(2) ? code_type(-1) : code_type(1);
b[5] = std::abs(std::abs(c.imag())-amp(4)) < amp(2) ? code_type(-1) : code_type(1);
}
static void soft(code_type *b, complex_type c, value_type precision)
{
b[0] = quantize(precision, c.real());
b[1] = quantize(precision, c.imag());
b[2] = quantize(precision, std::abs(c.real())-amp(4));
b[3] = quantize(precision, std::abs(c.imag())-amp(4));
b[4] = quantize(precision, std::abs(std::abs(c.real())-amp(4))-amp(2));
b[5] = quantize(precision, std::abs(std::abs(c.imag())-amp(4))-amp(2));
}
static complex_type map(code_type *b)
{
return AMP * complex_type(
b[0]*(b[2]*(b[4]+value_type(2))+value_type(4)),
b[1]*(b[3]*(b[5]+value_type(2))+value_type(4))
);
}
};
template <typename TYPE, typename CODE>
struct QuadratureAmplitudeModulation<256, TYPE, CODE>
{
static const int NUM = 256;
static const int BITS = 8;
typedef TYPE complex_type;
typedef typename TYPE::value_type value_type;
typedef CODE code_type;
static constexpr value_type FAC = 0.8692269873603529;
static constexpr value_type RCP = 15 * FAC;
static constexpr value_type AMP = 1 / RCP;
static constexpr value_type DIST = 2 * AMP;
static constexpr value_type amp(int i)
{
return AMP * i;
}
static code_type quantize(value_type precision, value_type value)
{
value *= DIST * precision;
if (std::is_integral<code_type>::value)
value = std::nearbyint(value);
if (std::is_same<code_type, int8_t>::value)
value = std::min<value_type>(std::max<value_type>(value, -128), 127);
return value;
}
static void hard(code_type *b, complex_type c)
{
b[0] = c.real() < amp(0) ? code_type(-1) : code_type(1);
b[1] = c.imag() < amp(0) ? code_type(-1) : code_type(1);
b[2] = std::abs(c.real()) < amp(8) ? code_type(-1) : code_type(1);
b[3] = std::abs(c.imag()) < amp(8) ? code_type(-1) : code_type(1);
b[4] = std::abs(std::abs(c.real())-amp(8)) < amp(4) ? code_type(-1) : code_type(1);
b[5] = std::abs(std::abs(c.imag())-amp(8)) < amp(4) ? code_type(-1) : code_type(1);
b[6] = std::abs(std::abs(std::abs(c.real())-amp(8))-amp(4)) < amp(2) ? code_type(-1) : code_type(1);
b[7] = std::abs(std::abs(std::abs(c.imag())-amp(8))-amp(4)) < amp(2) ? code_type(-1) : code_type(1);
}
static void soft(code_type *b, complex_type c, value_type precision)
{
b[0] = quantize(precision, c.real());
b[1] = quantize(precision, c.imag());
b[2] = quantize(precision, std::abs(c.real())-amp(8));
b[3] = quantize(precision, std::abs(c.imag())-amp(8));
b[4] = quantize(precision, std::abs(std::abs(c.real())-amp(8))-amp(4));
b[5] = quantize(precision, std::abs(std::abs(c.imag())-amp(8))-amp(4));
b[6] = quantize(precision, std::abs(std::abs(std::abs(c.real())-amp(8))-amp(4))-amp(2));
b[7] = quantize(precision, std::abs(std::abs(std::abs(c.imag())-amp(8))-amp(4))-amp(2));
}
static complex_type map(code_type *b)
{
return AMP * complex_type(
b[0]*(b[2]*(b[4]*(b[6]+value_type(2))+value_type(4))+value_type(8)),
b[1]*(b[3]*(b[5]*(b[7]+value_type(2))+value_type(4))+value_type(8))
);
}
};
template <typename TYPE, typename CODE>
struct QuadratureAmplitudeModulation<1024, TYPE, CODE>
{
static const int NUM = 1024;
static const int BITS = 10;
typedef TYPE complex_type;
typedef typename TYPE::value_type value_type;
typedef CODE code_type;
static constexpr value_type FAC = 0.8424235391742344;
static constexpr value_type RCP = 31 * FAC;
static constexpr value_type AMP = 1 / RCP;
static constexpr value_type DIST = 2 * AMP;
static constexpr value_type amp(int i)
{
return AMP * i;
}
static code_type quantize(value_type precision, value_type value)
{
value *= DIST * precision;
if (std::is_integral<code_type>::value)
value = std::nearbyint(value);
if (std::is_same<code_type, int8_t>::value)
value = std::min<value_type>(std::max<value_type>(value, -128), 127);
return value;
}
static void hard(code_type *b, complex_type c)
{
b[0] = c.real() < amp(0) ? code_type(-1) : code_type(1);
b[1] = c.imag() < amp(0) ? code_type(-1) : code_type(1);
b[2] = std::abs(c.real()) < amp(16) ? code_type(-1) : code_type(1);
b[3] = std::abs(c.imag()) < amp(16) ? code_type(-1) : code_type(1);
b[4] = std::abs(std::abs(c.real())-amp(16)) < amp(8) ? code_type(-1) : code_type(1);
b[5] = std::abs(std::abs(c.imag())-amp(16)) < amp(8) ? code_type(-1) : code_type(1);
b[6] = std::abs(std::abs(std::abs(c.real())-amp(16))-amp(8)) < amp(4) ? code_type(-1) : code_type(1);
b[7] = std::abs(std::abs(std::abs(c.imag())-amp(16))-amp(8)) < amp(4) ? code_type(-1) : code_type(1);
b[8] = std::abs(std::abs(std::abs(std::abs(c.real())-amp(16))-amp(8))-amp(4)) < amp(2) ? code_type(-1) : code_type(1);
b[9] = std::abs(std::abs(std::abs(std::abs(c.imag())-amp(16))-amp(8))-amp(4)) < amp(2) ? code_type(-1) : code_type(1);
}
static void soft(code_type *b, complex_type c, value_type precision)
{
b[0] = quantize(precision, c.real());
b[1] = quantize(precision, c.imag());
b[2] = quantize(precision, std::abs(c.real())-amp(16));
b[3] = quantize(precision, std::abs(c.imag())-amp(16));
b[4] = quantize(precision, std::abs(std::abs(c.real())-amp(16))-amp(8));
b[5] = quantize(precision, std::abs(std::abs(c.imag())-amp(16))-amp(8));
b[6] = quantize(precision, std::abs(std::abs(std::abs(c.real())-amp(16))-amp(8))-amp(4));
b[7] = quantize(precision, std::abs(std::abs(std::abs(c.imag())-amp(16))-amp(8))-amp(4));
b[8] = quantize(precision, std::abs(std::abs(std::abs(std::abs(c.real())-amp(16))-amp(8))-amp(4))-amp(2));
b[9] = quantize(precision, std::abs(std::abs(std::abs(std::abs(c.imag())-amp(16))-amp(8))-amp(4))-amp(2));
}
static complex_type map(code_type *b)
{
return AMP * complex_type(
b[0]*(b[2]*(b[4]*(b[6]*(b[8]+value_type(2))+value_type(4))+value_type(8))+value_type(16)),
b[1]*(b[3]*(b[5]*(b[7]*(b[9]+value_type(2))+value_type(4))+value_type(8))+value_type(16))
);
}
};
} // namespace ldpctool
#endif
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