diff --git a/lib/decode_mac.cc b/lib/decode_mac.cc
index f82332c..5dff67e 100644
--- a/lib/decode_mac.cc
+++ b/lib/decode_mac.cc
@@ -24,6 +24,8 @@
 
 using namespace gr::ieee802_11;
 
+#define LINKTYPE_IEEE802_11 105 /* http://www.tcpdump.org/linktypes.html */
+
 class decode_mac_impl : public decode_mac {
 
 public:
@@ -34,6 +36,8 @@ decode_mac_impl(bool log, bool debug) :
 	d_log(log),
 	d_debug(debug),
 	d_snr(0),
+	d_nom_freq(0.0),
+	d_freq_offset(0.0),
 	d_ofdm(BPSK_1_2),
 	d_frame(d_ofdm, 0),
 	d_frame_complete(true) {
@@ -70,6 +74,8 @@ int general_work (int noutput_items, gr_vector_int& ninput_items,
 			int len_data = pmt::to_uint64(pmt::tuple_ref(tuple, 0));
 			int encoding = pmt::to_uint64(pmt::tuple_ref(tuple, 1));
 			d_snr = pmt::to_double(pmt::tuple_ref(tuple, 2));
+			d_nom_freq = pmt::to_double(pmt::tuple_ref(tuple, 3));
+			d_freq_offset = pmt::to_double(pmt::tuple_ref(tuple, 4));
 
 			ofdm_param ofdm = ofdm_param((Encoding)encoding);
 			frame_param frame = frame_param(ofdm, len_data);
@@ -141,6 +147,9 @@ void decode() {
 	pmt::pmt_t dict = pmt::make_dict();
 	dict = pmt::dict_add(dict, pmt::mp("encoding"), enc);
 	dict = pmt::dict_add(dict, pmt::mp("snr"), pmt::from_double(d_snr));
+	dict = pmt::dict_add(dict, pmt::mp("nomfreq"), pmt::from_double(d_nom_freq));
+	dict = pmt::dict_add(dict, pmt::mp("freqofs"), pmt::from_double(d_freq_offset));
+	dict = pmt::dict_add(dict, pmt::mp("dlt"), pmt::from_long(LINKTYPE_IEEE802_11));
 	message_port_pub(pmt::mp("out"), pmt::cons(dict, blob));
 }
 
@@ -218,7 +227,9 @@ private:
 
 	frame_param d_frame;
 	ofdm_param d_ofdm;
-	double d_snr;
+	double d_snr;  // dB
+	double d_nom_freq;  // nominal frequency, Hz
+	double d_freq_offset;  // frequency offset, Hz
 	viterbi_decoder d_decoder;
 
 	uint8_t d_rx_symbols[48 * MAX_SYM];
diff --git a/lib/frame_equalizer_impl.cc b/lib/frame_equalizer_impl.cc
index 1bc8355..6b85e66 100644
--- a/lib/frame_equalizer_impl.cc
+++ b/lib/frame_equalizer_impl.cc
@@ -39,7 +39,8 @@ frame_equalizer_impl::frame_equalizer_impl(Equalizer algo, double freq, double b
 			gr::io_signature::make(1, 1, 64 * sizeof(gr_complex)),
 			gr::io_signature::make(1, 1, 48)),
 	d_current_symbol(0), d_log(log), d_debug(debug), d_equalizer(NULL),
-	d_freq(freq), d_bw(bw), d_frame_bytes(0), d_frame_symbols(0) {
+	d_freq(freq), d_bw(bw), d_frame_bytes(0), d_frame_symbols(0),
+	d_freq_offset_from_synclong(0.0) {
 
 	message_port_register_out(pmt::mp("symbols"));
 
@@ -131,6 +132,7 @@ frame_equalizer_impl::general_work (int noutput_items,
 			d_frame_symbols = 0;
 			d_frame_mod = d_bpsk;
 
+			d_freq_offset_from_synclong = pmt::to_double(tags.front().value) * d_bw;
 			d_epsilon0 = pmt::to_double(tags.front().value) * d_bw / (2 * M_PI * d_freq);
 			d_er = 0;
 
@@ -207,11 +209,14 @@ frame_equalizer_impl::general_work (int noutput_items,
 
 			if(decode_signal_field(out + o * 48)) {
 
+				// TODO: it would better to use pmt::dict instead of raw list of numbers
 				add_item_tag(0, nitems_written(0) + o,
 						pmt::string_to_symbol("wifi_start"),
 						pmt::make_tuple(pmt::from_uint64(d_frame_bytes),
 								pmt::from_uint64(d_frame_encoding),
-								pmt::from_double(d_equalizer->get_snr())),
+								pmt::from_double(d_equalizer->get_snr()),
+								pmt::from_double(d_freq),  // nominal frequency
+								pmt::from_double(d_freq_offset_from_synclong)),
 						pmt::string_to_symbol(name()));
 			}
 		}
diff --git a/lib/frame_equalizer_impl.h b/lib/frame_equalizer_impl.h
index d7ed540..86ea4dc 100644
--- a/lib/frame_equalizer_impl.h
+++ b/lib/frame_equalizer_impl.h
@@ -59,8 +59,9 @@ private:
 	viterbi_decoder d_decoder;
 
 	// freq offset
-	double d_freq;
-	double d_bw;
+	double d_freq;  // Hz
+	double d_freq_offset_from_synclong;  // Hz, estimation from "sync_long" block
+	double d_bw;  // Hz
 	double d_er;
 	double d_epsilon0;
 	gr_complex d_prev_pilots[4];