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diff --git a/gr-digital/include/digital_ofdm_insert_preamble.h b/gr-digital/include/digital_ofdm_insert_preamble.h
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+/* -*- c++ -*- */
+/*
+ * Copyright 2007,2011 Free Software Foundation, Inc.
+ * 
+ * This file is part of GNU Radio
+ * 
+ * GNU Radio 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, or (at your option)
+ * any later version.
+ * 
+ * GNU Radio 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, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef INCLUDED_DIGITAL_OFDM_INSERT_PREAMBLE_H
+#define INCLUDED_DIGITAL_OFDM_INSERT_PREAMBLE_H
+
+#include <gr_block.h>
+#include <vector>
+
+class digital_ofdm_insert_preamble;
+typedef boost::shared_ptr<digital_ofdm_insert_preamble> digital_ofdm_insert_preamble_sptr;
+
+digital_ofdm_insert_preamble_sptr
+digital_make_ofdm_insert_preamble(int fft_length,
+				  const std::vector<std::vector<gr_complex> > &preamble);
+
+/*!
+ * \brief insert "pre-modulated" preamble symbols before each payload.
+ * \ingroup sync_blk
+ * \ingroup ofdm_blk
+ *
+ * <pre>
+ * input 1: stream of vectors of gr_complex [fft_length]
+ *          These are the modulated symbols of the payload.
+ *
+ * input 2: stream of char.  The LSB indicates whether the corresponding
+ *          symbol on input 1 is the first symbol of the payload or not.
+ *          It's a 1 if the corresponding symbol is the first symbol,
+ *          otherwise 0.
+ *
+ * N.B., this implies that there must be at least 1 symbol in the payload.
+ *
+ *
+ * output 1: stream of vectors of gr_complex [fft_length]
+ *           These include the preamble symbols and the payload symbols.
+ *
+ * output 2: stream of char.  The LSB indicates whether the corresponding
+ *           symbol on input 1 is the first symbol of a packet (i.e., the
+ *           first symbol of the preamble.)   It's a 1 if the corresponding
+ *           symbol is the first symbol, otherwise 0.
+ * </pre>
+ *
+ * \param fft_length length of each symbol in samples.
+ * \param preamble   vector of symbols that represent the pre-modulated preamble.
+ */
+
+class digital_ofdm_insert_preamble : public gr_block
+{
+  friend digital_ofdm_insert_preamble_sptr
+  digital_make_ofdm_insert_preamble(int fft_length,
+				    const std::vector<std::vector<gr_complex> > &preamble);
+
+protected:
+  digital_ofdm_insert_preamble(int fft_length,
+			       const std::vector<std::vector<gr_complex> > &preamble);
+
+private:
+  enum state_t {
+    ST_IDLE,
+    ST_PREAMBLE,
+    ST_FIRST_PAYLOAD,
+    ST_PAYLOAD
+  };
+
+  int						d_fft_length;
+  const std::vector<std::vector<gr_complex> > 	d_preamble;
+  state_t					d_state;
+  int						d_nsymbols_output;
+  int						d_pending_flag;
+
+  void enter_idle();
+  void enter_preamble();
+  void enter_first_payload();
+  void enter_payload();
+  
+
+public:
+  ~digital_ofdm_insert_preamble();
+
+  int general_work (int noutput_items,
+		    gr_vector_int &ninput_items,
+		    gr_vector_const_void_star &input_items,
+		    gr_vector_void_star &output_items);
+};
+
+#endif /* INCLUDED_DIGITAL_OFDM_INSERT_PREAMBLE_H */