use long preamble for channel estimation and add lms equalizer

2015-04-17 10:23:25 +02:00
parent 5dd30e5e84
commit 48950a502b
9 changed files with 364 additions and 60 deletions
@@ -0,0 +1,104 @@
+/*
+ * Copyright (C) 2015 Bastian Bloessl <bloessl@ccs-labs.org>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "lms.h"
+#include <cstring>
+#include <iostream>
+
+using namespace gr::ieee802_11::equalizer;
+
+void lms::equalize(const gr_complex *in, gr_complex *out, int n) {
+
+	static float freq_offset = 0;
+	static float freq_sum = 0;
+	static float alpha = 0.9;
+
+	if(n == 0) {
+		std::memcpy(carrier, in, 64 * sizeof(gr_complex));
+	} else if(n == 1) {
+		gr_complex sum =
+			(carrier[11] * conj(in[11])) +
+			(carrier[25] * conj(in[25])) +
+			(carrier[39] * conj(in[39])) +
+			(carrier[53] * conj(in[53]));
+		freq_offset = arg(sum);
+		freq_sum = 0;
+		for(int i = 0; i < 64; i++) {
+			carrier[i] += in[i];
+			carrier[i] *= ref[i] * gr_complex(0.5, 0);
+		}
+	} else {
+
+		gr_complex p = POLARITY[(n - 2) % 127];
+		gr_complex sum =
+			(carrier[11] * conj(in[11]) *  p) +
+			(carrier[25] * conj(in[25]) *  p) +
+			(carrier[39] * conj(in[39]) *  p) +
+			(carrier[53] * conj(in[53]) * -p);
+
+		freq_offset = (1 - alpha) * freq_offset + alpha * arg(sum);
+		freq_sum += freq_offset;
+
+		//std::cout << "lms: symbol " << n
+		//	<< "   p1 " << abs(carrier[11] * conj(in[11]) *  p)
+		//	<< "   p2 " << abs(carrier[25] * conj(in[25]) *  p)
+		//	<< "   p3 " << abs(carrier[39] * conj(in[39]) *  p)
+		//	<< "   p4 " << abs(carrier[53] * conj(in[53]) * -p)
+		//	<< std::endl;
+		//std::cout << "lms: symbol " << n
+		//	<< "   p1 " << arg(carrier[11] * conj(in[11]) *  p)
+		//	<< "   p2 " << arg(carrier[25] * conj(in[25]) *  p)
+		//	<< "   p3 " << arg(carrier[39] * conj(in[39]) *  p)
+		//	<< "   p4 " << arg(carrier[53] * conj(in[53]) * -p)
+		//	<< std::endl;
+
+		carrier[11] = in[11] *  p;
+		carrier[25] = in[25] *  p;
+		carrier[39] = in[39] *  p;
+		carrier[53] = in[53] * -p;
+
+		int c = 0;
+		for(int i = 0; i < 64; i++) {
+			if( (i == 11) || (i == 25) || (i == 32) || (i == 39) || (i == 53) || (i < 6) || ( i > 58)) {
+				continue;
+			} else {
+				out[c] = in[i] / carrier[i] * exp(gr_complex(0, freq_sum));
+				c++;
+			}
+		}
+	}
+}
+
+const gr_complex lms::ref[] = {
+	 0,  0,  0,  0,  0,  0,  1,  1, -1, -1,
+	 1,  1, -1,  1, -1,  1,  1,  1,  1,  1,
+	 1, -1, -1,  1,  1, -1,  1, -1,  1,  1,
+	 1,  1,  0,  1, -1, -1,  1,  1, -1,  1,
+	-1,  1, -1, -1, -1, -1, -1,  1,  1, -1,
+	-1,  1, -1,  1, -1,  1,  1,  1,  1,  0,
+	 0,  0,  0,  0
+};
+
+const gr_complex lms::POLARITY[127] = {
+	 1, 1, 1, 1,-1,-1,-1, 1,-1,-1,-1,-1, 1, 1,-1, 1,
+	-1,-1, 1, 1,-1, 1, 1,-1, 1, 1, 1, 1, 1, 1,-1, 1,
+	 1, 1,-1, 1, 1,-1,-1, 1, 1, 1,-1, 1,-1,-1,-1, 1,
+	-1, 1,-1,-1, 1,-1,-1, 1, 1, 1, 1, 1,-1,-1, 1, 1,
+	-1,-1, 1,-1, 1,-1, 1, 1,-1,-1,-1, 1, 1,-1,-1,-1,
+	-1, 1,-1,-1, 1,-1, 1, 1, 1, 1,-1, 1,-1, 1,-1, 1,
+	-1,-1,-1,-1,-1, 1,-1, 1, 1,-1, 1,-1, 1, 1, 1,-1,
+	-1, 1,-1,-1,-1, 1, 1, 1,-1,-1,-1,-1,-1,-1,-1 };