- Added new Viterbi convolutional decoder to the OFDM Decode Mac block replacing the former IT++ version. This new decoder uses

SSE2 and improves the performance significantly. The decoder was taken from the gr-dvbt module from GNU Radio.
- Disabled some logging functions in the ofdm_mac and ofdm_decode_signal blocks that were degrading the performance significantly.

[Gonzalo Arcos | Rodrigo Ferreri]

lib/utils.h

@@ -23,6 +23,9 @@
 #include <cinttypes>
 #include <iostream>
 
+// Needed for the SSE2 Viterbi decoder
+#include <xmmintrin.h>
+
 const int MAX_SYM = 520; // enough for 1500 byte BPSK 1/2
 const int MAX_BITS = 1550 * 8 * 2;
 
@@ -120,4 +123,66 @@ void split_symbols(const char *input, char *out, tx_param &tx, ofdm_param &ofdm)
 
 void generate_bits(const char *psdu, char *data_bits, tx_param &tx);
 
+/* New functions for the SSE2 Convolutional Decoder */
+
+/* This Viterbi decoder was taken from the gr-dvbt module of 
+ * GNU Radio. It is an SSE2 version of the Viterbi Decoder 
+ * created by Phil Karn. The SSE2 version was made by Bogdan 
+ * Diaconescu. For more info see: gr-dvbt/lib/d_viterbi.h
+ */
+
+
+struct viterbi_state {
+  unsigned long path;	/* Decoded path to this state */
+  long metric;		/* Cumulative metric to this state */
+
+  /* vector implementation */
+  __m128i pp;		/* Decoded path to this state */
+  __m128i mm;		/* Cumulative metric to this state */
+};
+
+int d_gen_met(int mettab[2][256],	/* Metric table */
+	    int amp,		/* Signal amplitude */
+	    double esn0,	/* Es/N0 ratio in dB */
+	    double bias, 	/* Metric bias */
+	    int scale);		/* Scale factor */
+
+unsigned char
+d_encode(unsigned char *symbols, unsigned char *data,
+       unsigned int nbytes,unsigned char encstate);
+
+void
+d_viterbi_chunks_init(struct viterbi_state* state);
+
+void
+d_viterbi_chunks_init_sse2(__m128i *mm0, __m128i *pp0);
+
+void
+d_viterbi_butterfly2(unsigned char *symbols, int mettab[2][256], struct viterbi_state *state0, struct viterbi_state *state1);
+
+void
+d_viterbi_butterfly2_sse2(unsigned char *symbols, __m128i m0[], __m128i m1[], __m128i p0[], __m128i p1[]);
+
+void
+d_viterbi_butterfly_sse2(unsigned char *symbols, __m128i m0[], __m128i m1[], __m128i p0[], __m128i p1[]);
+
+unsigned char
+d_viterbi_get_output(struct viterbi_state *state, unsigned char *outbuf);
+
+unsigned char
+d_viterbi_get_output_sse2(__m128i *mm0, __m128i *pp0, int ntraceback, unsigned char *outbuf);
+
+
+int 
+d_viterbi(unsigned long *metric,	/* Final path metric (returned value) */
+	unsigned char *data,	/* Decoded output data */
+	unsigned char *symbols,	/* Raw deinterleaved input symbols */
+	unsigned int nbits,	/* Number of output bits */
+	int mettab[2][256]	/* Metric table, [sent sym][rx symbol] */
+);
+
+
+/* End of added functions */
+
+
 #endif /* INCLUDED_IEEE802_11_OFDM_UTILS_H */