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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 2007,2011,2012 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 <digital/api.h>
+#include <gr_block.h>
+#include <vector>
+
+namespace gr {
+  namespace digital {
+    
+    /*!
+     * \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_API ofdm_insert_preamble : virtual public gr_block
+    {
+    public:
+      // gr::digital::ofdm_insert_preamble::sptr
+      typedef boost::shared_ptr<ofdm_insert_preamble> sptr;
+      
+      /*!
+       * Make an OFDM preamble inserter block.
+       *
+       * \param fft_length length of each symbol in samples.
+       * \param preamble   vector of symbols that represent the pre-modulated preamble.
+       */
+      static sptr make(int fft_length,
+		       const std::vector<std::vector<gr_complex> > &preamble);
+
+      virtual void enter_preamble() = 0;
+    };
+
+  } /* namespace digital */
+} /* namespace gr */
+
+#endif /* INCLUDED_DIGITAL_OFDM_INSERT_PREAMBLE_H */