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Modifying comments in soft_algs.c.

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master
marojevic 11 years ago
parent e3ae271f5c
commit 5915918794
1 changed files with 8 additions and 8 deletions
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16
lte/phy/lib/modem/src/soft_algs.c
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@ -50,7 +50,6 @@
* \param S Soft demapping auxiliary matrix * \param S Soft demapping auxiliary matrix
* \param sigma2 Noise vatiance * \param sigma2 Noise vatiance
*/ */
/* Note: Optimized implementation of approximate LLR algorithm, July 2014*/
void llr_approx(const _Complex float *in, float *out, int N, int M, int B, void llr_approx(const _Complex float *in, float *out, int N, int M, int B,
_Complex float *symbols, uint32_t (*S)[6][32], float sigma2) { _Complex float *symbols, uint32_t (*S)[6][32], float sigma2) {
int i, s, b; int i, s, b;
@ -59,7 +58,7 @@ void llr_approx(const _Complex float *in, float *out, int N, int M, int B,
float x, y, d[64]; float x, y, d[64];
for (s=0; s<N; s++) { /* recevied symbols */ for (s=0; s<N; s++) { /* recevied symbols */
/* Compute exp{·} of the distances between received symbol and all constallation symbols */ /* Compute the distances squared d[i] between the received symbol and all constellation points */
for (i=0; i<M; i++) { for (i=0; i<M; i++) {
x = __real__ in[s] - __real__ symbols[i]; x = __real__ in[s] - __real__ symbols[i];
y = __imag__ in[s] - __imag__ symbols[i]; y = __imag__ in[s] - __imag__ symbols[i];
@ -71,8 +70,9 @@ void llr_approx(const _Complex float *in, float *out, int N, int M, int B,
num = d[S[0][b][0]]; num = d[S[0][b][0]];
den = d[S[1][b][0]]; den = d[S[1][b][0]];
/* half the constellation symbols have '1'|'0' at any bit pos. */ /* Minimum distance squared search between recevied symbol and a constellation point with a
for (i=1; i<M/2; i++) { '1' and a '0' for each bit position */
for (i=1; i<M/2; i++) { /* half the constellation points have '1'|'0' at any given bit position */
if (d[S[0][b][i]] < num) { if (d[S[0][b][i]] < num) {
num = d[S[0][b][i]]; num = d[S[0][b][i]];
} }
@ -106,7 +106,6 @@ void llr_approx(const _Complex float *in, float *out, int N, int M, int B,
* \param S Soft demapping auxiliary matrix * \param S Soft demapping auxiliary matrix
* \param sigma2 Noise vatiance * \param sigma2 Noise vatiance
*/ */
/* Note: Optimized implementation of exact LLR algorithm, July 2014*/
void llr_exact(const _Complex float *in, float *out, int N, int M, int B, void llr_exact(const _Complex float *in, float *out, int N, int M, int B,
_Complex float *symbols, uint32_t (*S)[6][32], float sigma2) { _Complex float *symbols, uint32_t (*S)[6][32], float sigma2) {
int i, s, b; int i, s, b;
@ -115,19 +114,20 @@ void llr_exact(const _Complex float *in, float *out, int N, int M, int B,
float x, y, d[64]; float x, y, d[64];
for (s=0; s<N; s++) { /* recevied symbols */ for (s=0; s<N; s++) { /* recevied symbols */
/* Compute exp{·} of the distances between received symbol and all constallation symbols */ /* Compute exp{·} of the distances squared d[i] between the received symbol and all constellation points */
for (i=0; i<M; i++) { for (i=0; i<M; i++) {
x = __real__ in[s] - __real__ symbols[i]; x = __real__ in[s] - __real__ symbols[i];
y = __imag__ in[s] - __imag__ symbols[i]; y = __imag__ in[s] - __imag__ symbols[i];
d[i] = exp(-1*(x*x + y*y)/sigma2); d[i] = exp(-1*(x*x + y*y)/sigma2);
} }
/* Sum up the corresponding d[i]'s for each bit position */
for (b=0; b<B; b++) {/* bits per symbol*/ for (b=0; b<B; b++) {/* bits per symbol*/
/* initiate num[b] and den[b] */ /* initiate num[b] and den[b] */
num = 0; num = 0;
den = 0; den = 0;
/* half the constellation symbols have '1'|'0' at any bit pos. */
for (i=0; i<M/2; i++) { for (i=0; i<M/2; i++) { /* half the constellation points have '1'|'0' at any given bit position */
num += d[S[0][b][i]]; num += d[S[0][b][i]];
den += d[S[1][b][i]]; den += d[S[1][b][i]];
} }

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