diff options
| -rw-r--r-- | gnuradio-core/src/lib/viterbi/metrics.c | 17 |
1 files changed, 7 insertions, 10 deletions
diff --git a/gnuradio-core/src/lib/viterbi/metrics.c b/gnuradio-core/src/lib/viterbi/metrics.c index 2dd4279aa..9f958cab7 100644 --- a/gnuradio-core/src/lib/viterbi/metrics.c +++ b/gnuradio-core/src/lib/viterbi/metrics.c @@ -46,10 +46,7 @@ #define normal(x) (0.5 + 0.5*erf((x)/M_SQRT2)) /* Logarithm base 2 */ -double log2(double); /* declaration seems to be missing from some math.h's */ -#if !defined(HAVE_LOG2) -#define log2(x) (log(x)*M_LOG2E) -#endif +#define gr_log2(x) (log(x)*M_LOG2E) /* Generate log-likelihood metrics for 8-bit soft quantized channel * assuming AWGN and BPSK @@ -80,8 +77,8 @@ gen_met(int mettab[2][256], /* Metric table, [sent sym][rx symbol] */ /* Prob of this value occurring for a 0-bit */ /* P(s|0) */ p0 = normal(((0-OFFSET+0.5)/amp + 1)/noise); - metrics[0][0] = log2(2*p0/(p1+p0)) - bias; - metrics[1][0] = log2(2*p1/(p1+p0)) - bias; + metrics[0][0] = gr_log2(2*p0/(p1+p0)) - bias; + metrics[1][0] = gr_log2(2*p1/(p1+p0)) - bias; for(s=1;s<255;s++){ /* P(s|1), prob of receiving s given 1 transmitted */ @@ -95,8 +92,8 @@ gen_met(int mettab[2][256], /* Metric table, [sent sym][rx symbol] */ #ifdef notdef printf("P(%d|1) = %lg, P(%d|0) = %lg\n",s,p1,s,p0); #endif - metrics[0][s] = log2(2*p0/(p1+p0)) - bias; - metrics[1][s] = log2(2*p1/(p1+p0)) - bias; + metrics[0][s] = gr_log2(2*p0/(p1+p0)) - bias; + metrics[1][s] = gr_log2(2*p1/(p1+p0)) - bias; } /* 255 is also a special value */ /* P(s|1) */ @@ -104,8 +101,8 @@ gen_met(int mettab[2][256], /* Metric table, [sent sym][rx symbol] */ /* P(s|0) */ p0 = 1 - normal(((255-OFFSET-0.5)/amp + 1)/noise); - metrics[0][255] = log2(2*p0/(p1+p0)) - bias; - metrics[1][255] = log2(2*p1/(p1+p0)) - bias; + metrics[0][255] = gr_log2(2*p0/(p1+p0)) - bias; + metrics[1][255] = gr_log2(2*p1/(p1+p0)) - bias; #ifdef notdef /* The probability of a raw symbol error is the probability * that a 1-bit would be received as a sample with value |