digital: ofdm: Allow multiple CP lengths for cyclic prefixer

This allows to specify multiple CP lengths that can be used one after another, for example for LTE modulators. - Improve sanity checking - Maintains old API
author: Maximilian Stiefel <stiefel.maximilian@online.de> 2020-01-07 17:03:59 -0800
committer: Martin Braun <martin.braun@ettus.com> 2020-01-08 10:19:44 -0800
commit: 445aa4792dcdf4a8bf14600e6d931451e36f0eaa (patch)
tree: 8a011d807a5f30fdf8cac945b5ba294a0937d5af
parent: 90c49ef6d4d215f1db01f591d682947fea727655 (diff)
6 files changed, 399 insertions, 98 deletions
diff --git a/gr-digital/examples/ofdm/tx_ofdm.grc b/gr-digital/examples/ofdm/tx_ofdm.grc
index 4d68086dcc..309dedbb4f 100644
--- a/gr-digital/examples/ofdm/tx_ofdm.grc
+++ b/gr-digital/examples/ofdm/tx_ofdm.grc
@@ -1,6 +1,7 @@
 options:
   parameters:
     author: ''
+    catch_exceptions: 'True'
     category: Custom
     cmake_opt: ''
     comment: ''
@@ -24,6 +25,9 @@ options:
     title: OFDM Tx
     window_size: 1280, 1024
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [16, 12.0]
     rotation: 0
     state: enabled
@@ -35,6 +39,9 @@ blocks:
     comment: ''
     value: '64'
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [208, 12.0]
     rotation: 0
     state: enabled
@@ -44,6 +51,9 @@ blocks:
     comment: ''
     value: digital.header_format_ofdm(occupied_carriers, 1, length_tag_key,)
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [912, 68.0]
     rotation: 0
     state: enabled
@@ -53,6 +63,9 @@ blocks:
     comment: ''
     value: digital.constellation_bpsk()
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [592, 12.0]
     rotation: 0
     state: enabled
@@ -62,6 +75,9 @@ blocks:
     comment: ''
     value: '"packet_len"'
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [368, 12.0]
     rotation: 0
     state: enabled
@@ -72,6 +88,9 @@ blocks:
     value: (list(range(-26, -21)) + list(range(-20, -7)) + list(range(-6, 0)) + list(range(1,
       7)) + list(range(8, 21)) + list(range(22, 27)),)
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [512, 68.0]
     rotation: 0
     state: enabled
@@ -81,6 +100,9 @@ blocks:
     comment: ''
     value: '96'
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [496, 12.0]
     rotation: 0
     state: enabled
@@ -90,6 +112,9 @@ blocks:
     comment: ''
     value: digital.constellation_qpsk()
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [752, 12.0]
     rotation: 0
     state: enabled
@@ -99,6 +124,9 @@ blocks:
     comment: ''
     value: ((-21, -7, 7, 21,),)
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [672, 68.0]
     rotation: 0
     state: enabled
@@ -108,6 +136,9 @@ blocks:
     comment: ''
     value: ((1, 1, 1, -1,),)
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [800, 68.0]
     rotation: 0
     state: enabled
@@ -117,6 +148,9 @@ blocks:
     comment: ''
     value: '0'
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [912, 12.0]
     rotation: 0
     state: enabled
@@ -126,6 +160,9 @@ blocks:
     comment: ''
     value: '50000'
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [272, 12.0]
     rotation: 0
     state: enabled
@@ -140,6 +177,9 @@ blocks:
       0., -1.41421356, 0., 1.41421356, 0., 1.41421356, 0., 1.41421356, 0., -1.41421356,
       0., 1.41421356, 0., 1.41421356, 0., 1.41421356, 0., 0., 0., 0., 0., 0.]'
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [208, 68.0]
     rotation: 0
     state: enabled
@@ -151,6 +191,9 @@ blocks:
       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] '
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [336, 68.0]
     rotation: 0
     state: enabled
@@ -168,6 +211,9 @@ blocks:
     repeat: 'True'
     type: byte
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [16, 164.0]
     rotation: 0
     state: enabled
@@ -183,6 +229,9 @@ blocks:
     type: complex
     vlen: '1'
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [200, 692.0]
     rotation: 0
     state: enabled
@@ -200,6 +249,9 @@ blocks:
     maxoutbuf: '0'
     minoutbuf: '0'
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [640, 244.0]
     rotation: 0
     state: enabled
@@ -217,6 +269,9 @@ blocks:
     maxoutbuf: '0'
     minoutbuf: '0'
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [880, 180.0]
     rotation: 0
     state: enabled
@@ -233,6 +288,9 @@ blocks:
     type: byte
     vlen: '1'
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [176, 180.0]
     rotation: 0
     state: enabled
@@ -249,6 +307,9 @@ blocks:
     type: byte
     vlen: '1'
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [712, 828.0]
     rotation: 0
     state: enabled
@@ -265,6 +326,9 @@ blocks:
     type: complex
     vlen: '1'
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [360, 684.0]
     rotation: 0
     state: enabled
@@ -282,6 +346,9 @@ blocks:
     type: complex
     vlen: '1'
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [512, 360.0]
     rotation: 0
     state: enabled
@@ -298,6 +365,9 @@ blocks:
     type: complex
     vlen: '1'
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [552, 692.0]
     rotation: 0
     state: enabled
@@ -316,6 +386,9 @@ blocks:
     seed: '0'
     taps: 1.0 + 1.0j
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [200, 812.0]
     rotation: 0
     state: enabled
@@ -333,6 +406,9 @@ blocks:
     out_type: complex
     symbol_table: header_mod.points()
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [216, 320.0]
     rotation: 0
     state: enabled
@@ -350,6 +426,9 @@ blocks:
     out_type: complex
     symbol_table: payload_mod.points()
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [216, 392.0]
     rotation: 0
     state: enabled
@@ -365,6 +444,9 @@ blocks:
     minoutbuf: '0'
     packed: 'True'
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [384, 172.0]
     rotation: 0
     state: enabled
@@ -384,6 +466,9 @@ blocks:
     pilot_symbols: pilot_symbols
     sync_words: (sync_word1, sync_word2)
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [200, 476.0]
     rotation: 0
     state: enabled
@@ -393,13 +478,16 @@ blocks:
     affinity: ''
     alias: ''
     comment: ''
-    cp_len: fft_len//4
+    cp_len: fft_len/4
     input_size: fft_len
     maxoutbuf: '0'
     minoutbuf: '0'
     rolloff: rolloff
     tagname: length_tag_key
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [624, 508.0]
     rotation: 0
     state: enabled
@@ -424,6 +512,9 @@ blocks:
     sync_word1: sync_word1
     sync_word2: sync_word2
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [440, 764.0]
     rotation: 0
     state: enabled
@@ -438,6 +529,9 @@ blocks:
     maxoutbuf: '0'
     minoutbuf: '0'
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [640, 180.0]
     rotation: 0
     state: enabled
@@ -456,6 +550,9 @@ blocks:
     type: complex
     window: ()
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [416, 492.0]
     rotation: 0
     state: enabled
@@ -466,6 +563,9 @@ blocks:
     comment: ''
     stream_id: Header Bits
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [1088, 188.0]
     rotation: 0
     state: enabled
@@ -543,6 +643,9 @@ blocks:
     ymax: '10'
     ymin: '-140'
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [960, 756.0]
     rotation: 0
     state: enabled
@@ -563,16 +666,16 @@ blocks:
     alpha9: '1.0'
     autoscale: 'True'
     axislabels: 'True'
-    color1: '"blue"'
-    color10: '"blue"'
-    color2: '"red"'
-    color3: '"green"'
-    color4: '"black"'
-    color5: '"cyan"'
-    color6: '"magenta"'
-    color7: '"yellow"'
-    color8: '"dark red"'
-    color9: '"dark green"'
+    color1: blue
+    color10: dark blue
+    color2: red
+    color3: green
+    color4: black
+    color5: cyan
+    color6: magenta
+    color7: yellow
+    color8: dark red
+    color9: dark green
     comment: ''
     ctrlpanel: 'False'
     entags: 'True'
@@ -637,6 +740,9 @@ blocks:
     ymin: '-1'
     yunit: '""'
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [960, 668.0]
     rotation: 0
     state: enabled
@@ -647,6 +753,9 @@ blocks:
     comment: ''
     stream_id: Time Domain
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [856, 524]
     rotation: 0
     state: enabled
@@ -657,6 +766,9 @@ blocks:
     comment: ''
     stream_id: Payload Bits
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [832, 252.0]
     rotation: 0
     state: enabled
@@ -667,6 +779,9 @@ blocks:
     comment: ''
     stream_id: Pre-OFDM
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [744, 372.0]
     rotation: 0
     state: enabled
@@ -677,6 +792,9 @@ blocks:
     comment: ''
     stream_id: Tx Signal
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [960, 620.0]
     rotation: 0
     state: enabled
@@ -687,6 +805,9 @@ blocks:
     comment: ''
     stream_id: Header Bits
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [8, 316.0]
     rotation: 0
     state: enabled
@@ -697,6 +818,9 @@ blocks:
     comment: ''
     stream_id: Payload Bits
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [8, 388.0]
     rotation: 0
     state: enabled
@@ -707,6 +831,9 @@ blocks:
     comment: ''
     stream_id: Pre-OFDM
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [8, 524.0]
     rotation: 0
     state: enabled
@@ -717,6 +844,9 @@ blocks:
     comment: ''
     stream_id: Time Domain
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [8, 692.0]
     rotation: 0
     state: enabled
@@ -727,6 +857,9 @@ blocks:
     comment: ''
     stream_id: Tx Signal
   states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
     coordinate: [8, 844.0]
     rotation: 0
     state: enabled
diff --git a/gr-digital/grc/digital_ofdm_cyclic_prefixer.block.yml b/gr-digital/grc/digital_ofdm_cyclic_prefixer.block.yml
index 2bae7310eb..fd34e8a3c5 100644
--- a/gr-digital/grc/digital_ofdm_cyclic_prefixer.block.yml
+++ b/gr-digital/grc/digital_ofdm_cyclic_prefixer.block.yml
@@ -8,8 +8,8 @@ parameters:
     dtype: int
     default: fft_len
 -   id: cp_len
-    label: CP Length
-    dtype: int
+    label: CP Length(s)
+    dtype: raw
     default: fft_len/4
 -   id: rolloff
     label: Rolloff
@@ -32,8 +32,16 @@ outputs:
 
 templates:
     imports: from gnuradio import digital
-    make: digital.ofdm_cyclic_prefixer(${input_size}, ${input_size} + ${cp_len}, ${rolloff},
-        ${tagname})
+    make: |-
+        digital.ofdm_cyclic_prefixer(
+            ${input_size},
+        % if isinstance(context.get('cp_len')(), (tuple, list)):
+            ${cp_len},
+        % else:
+            ${input_size} + ${cp_len},
+        % endif
+            ${rolloff},
+            ${tagname})
 
 cpp_templates:
     includes: ['#include <gnuradio/digital/ofdm_cyclic_prefixer.h>']
@@ -41,7 +49,11 @@ cpp_templates:
     make: |-
         this->${id} = digital::ofdm_cyclic_prefixer::make(
             ${input_size},
+        % if isinstance(context.get('cp_len')(), (tuple, list)):
+            ${cp_len},
+        % else:
             ${input_size} + ${cp_len},
+        % endif
             ${rolloff},
             ${tagname});
     link: ['gnuradio-digital']
diff --git a/gr-digital/include/gnuradio/digital/ofdm_cyclic_prefixer.h b/gr-digital/include/gnuradio/digital/ofdm_cyclic_prefixer.h
index f0f0d16097..be4c1e1e77 100644
--- a/gr-digital/include/gnuradio/digital/ofdm_cyclic_prefixer.h
+++ b/gr-digital/include/gnuradio/digital/ofdm_cyclic_prefixer.h
@@ -1,6 +1,6 @@
 /* -*- c++ -*- */
 /*
- * Copyright 2013 Free Software Foundation, Inc.
+ * Copyright 2013, 2018 Free Software Foundation, Inc.
  *
  * This file is part of GNU Radio
  *
@@ -30,7 +30,7 @@ namespace gr {
 namespace digital {
 
 /*!
- * \brief Adds a cyclic prefix and performs pulse shaping on OFDM symbols.
+ * \brief Adds a cyclic prefix and performs optional pulse shaping on OFDM symbols.
  * \ingroup ofdm_blk
  *
  * \details
@@ -45,6 +45,19 @@ namespace digital {
  *         the pulse shaping.
  *
  * The pulse shape is a raised cosine in the time domain.
+ *
+ * Different CP lengths as for instance needed in LTE are supported. This
+ * is why one of the inputs is std::vector<int>. After every CP given has
+ * been prepended to symbols, each with the length of the IFFT operation,
+ * the mechanism will wrap around and start over. To give an example, the
+ * input tuple for LTE with an FFT length of 2048 would be (160,) +
+ * (144,)*6, which is equal to (160, 144, 144, 144, 144, 144, 144). A
+ * uniform CP would be indicated by (uniform_cp_length, ).
+ *
+ * This block does some sanity checking: 1. It is not allowed to have a
+ * vector of CP lengths, which are only 0.  2. Not a single CP in the
+ * vector must be longer than the rolloff. 3. Not a single CP is allowed to
+ * be < 0.
  */
 class DIGITAL_API ofdm_cyclic_prefixer : virtual public tagged_stream_block
 {
@@ -52,15 +65,26 @@ public:
     typedef boost::shared_ptr<ofdm_cyclic_prefixer> sptr;
 
     /*!
-     * \param input_size FFT length (i.e. length of the OFDM symbols)
-     * \param output_size FFT length + cyclic prefix length (in samples)
-     * \param rolloff_len Length of the rolloff flank in samples
-     * \param len_tag_key For framed processing the key of the length tag
+     * \param input_size IFFT length (i.e. length of the OFDM symbols).
+     * \param output_size FFT length + cyclic prefix length (in samples).
+     * \param rolloff_len Length of the rolloff flank in samples.
+     * \param len_tag_key For framed processing the key of the length tag.
      */
     static sptr make(size_t input_size,
                      size_t output_size,
                      int rolloff_len = 0,
                      const std::string& len_tag_key = "");
+
+    /*!
+     * \param fft_len IFFT length (i.e. length of the OFDM symbols).
+     * \param cp_lengths CP lengths. Wraps around after reaching the end.
+     * \param rolloff_len Length of the rolloff flank in samples.
+     * \param len_tag_key For framed processing the key of the length tag.
+     */
+    static sptr make(int fft_len,
+                     const std::vector<int>& cp_lengths,
+                     int rolloff_len = 0,
+                     const std::string& len_tag_key = "");
 };
 
 } // namespace digital
diff --git a/gr-digital/lib/ofdm_cyclic_prefixer_impl.cc b/gr-digital/lib/ofdm_cyclic_prefixer_impl.cc
index f79238e461..36bae1098e 100644
--- a/gr-digital/lib/ofdm_cyclic_prefixer_impl.cc
+++ b/gr-digital/lib/ofdm_cyclic_prefixer_impl.cc
@@ -1,6 +1,6 @@
 /* -*- c++ -*- */
 /*
- * Copyright 2013,2018 Free Software Foundation, Inc.
+ * Copyright 2013, 2018 Free Software Foundation, Inc.
  *
  * This file is part of GNU Radio
  *
@@ -26,73 +26,117 @@
 
 #include "ofdm_cyclic_prefixer_impl.h"
 #include <gnuradio/io_signature.h>
-#include <gnuradio/math.h>
 
 namespace gr {
 namespace digital {
 
+// Do not break backwards compatibility and overload the make function.
 ofdm_cyclic_prefixer::sptr ofdm_cyclic_prefixer::make(size_t input_size,
                                                       size_t output_size,
                                                       int rolloff_len,
                                                       const std::string& len_tag_key)
 {
+    int fft_len = input_size;
+    std::vector<int> cp_lengths(
+        1, static_cast<int>(output_size - input_size)); // Cast to silence compiler :(
     return gnuradio::get_initial_sptr(
-        new ofdm_cyclic_prefixer_impl(input_size, output_size, rolloff_len, len_tag_key));
+        new ofdm_cyclic_prefixer_impl(fft_len, cp_lengths, rolloff_len, len_tag_key));
 }
 
+ofdm_cyclic_prefixer::sptr ofdm_cyclic_prefixer::make(int fft_len,
+                                                      const std::vector<int>& cp_lengths,
+                                                      int rolloff_len,
+                                                      const std::string& len_tag_key)
+{
+    return gnuradio::get_initial_sptr(
+        new ofdm_cyclic_prefixer_impl(fft_len, cp_lengths, rolloff_len, len_tag_key));
+}
 
-ofdm_cyclic_prefixer_impl::ofdm_cyclic_prefixer_impl(size_t input_size,
-                                                     size_t output_size,
+ofdm_cyclic_prefixer_impl::ofdm_cyclic_prefixer_impl(int fft_len,
+                                                     const std::vector<int>& cp_lengths,
                                                      int rolloff_len,
                                                      const std::string& len_tag_key)
-    : tagged_stream_block("ofdm_cyclic_prefixer",
-                          io_signature::make(1, 1, input_size * sizeof(gr_complex)),
-                          io_signature::make(1, 1, sizeof(gr_complex)),
-                          len_tag_key),
-      d_fft_len(input_size),
-      d_output_size(output_size),
-      d_cp_size(output_size - input_size),
+    : gr::tagged_stream_block("ofdm_cyclic_prefixer",
+                              gr::io_signature::make(1, 1, fft_len * sizeof(gr_complex)),
+                              gr::io_signature::make(1, 1, sizeof(gr_complex)),
+                              len_tag_key),
+      d_fft_len(fft_len),
+      d_state(0),
+      d_cp_max(0),
+      d_cp_min(std::numeric_limits<int>::max()),
       d_rolloff_len(rolloff_len),
+      d_cp_lengths(cp_lengths),
       d_up_flank((rolloff_len ? rolloff_len - 1 : 0), 0),
       d_down_flank((rolloff_len ? rolloff_len - 1 : 0), 0),
-      d_delay_line(0, 0)
+      d_delay_line(0, 0),
+      d_len_tag_key(len_tag_key)
 {
-    set_relative_rate((uint64_t)d_output_size, 1);
-
-    // Flank of length 1 would just be rectangular
+    // Sanity
+    if (d_cp_lengths.empty()) {
+        throw std::invalid_argument(this->alias() +
+                                    std::string(": CP lengths vector can not be empty."));
+    }
+    for (size_t i = 0; i < d_cp_lengths.size(); i++) {
+        if (d_cp_lengths[i] != 0) {
+            break;
+        }
+        if (i == d_cp_lengths.size() - 1) {
+            throw std::invalid_argument(
+                this->alias() +
+                std::string(": Please provide at least one CP which is != 0."));
+        }
+    }
+    for (const int cp_length : d_cp_lengths) {
+        d_cp_max = std::max(d_cp_max, cp_length);
+        d_cp_min = std::min(d_cp_min, cp_length);
+    }
+    if (d_cp_min < 0) {
+        throw std::invalid_argument(this->alias() +
+                                    std::string(": The minimum CP allowed is 0."));
+    }
+    // Give the buffer allocator and scheduler a hint about the ratio between input and
+    // output.
+    set_relative_rate(d_cp_max + d_fft_len);
+    // Flank of length 1 would just be rectangular.
     if (d_rolloff_len == 1) {
         d_rolloff_len = 0;
+        GR_LOG_WARN(d_logger,
+                    "Set rolloff to 0, because 1 would result in a boxcar function.");
     }
     if (d_rolloff_len) {
         d_delay_line.resize(d_rolloff_len - 1, 0);
-        if (rolloff_len > d_cp_size) {
+        // More sanity
+        if (d_rolloff_len > d_cp_min) {
             throw std::invalid_argument(
-                "cyclic prefixer: rolloff len must smaller than the cyclic prefix.");
+                this->alias() + std::string(": Rolloff length must be smaller than any "
+                                            "of the cyclic prefix lengths."));
         }
-        // The actual flanks are one sample shorter than d_rolloff_len, because the
-        // first sample of the up- and down flank is always zero and one, respectively
+        /* The actual flanks are one sample shorter than d_rolloff_len, because the
+           first sample of the up- and down flank is always zero and one, respectively.*/
         for (int i = 1; i < d_rolloff_len; i++) {
-            d_up_flank[i - 1] = 0.5 * (1 + cos(GR_M_PI * i / rolloff_len - GR_M_PI));
+            d_up_flank[i - 1] = 0.5 * (1 + cos(M_PI * i / rolloff_len - M_PI));
             d_down_flank[i - 1] =
-                0.5 * (1 + cos(GR_M_PI * (rolloff_len - i) / rolloff_len - GR_M_PI));
+                0.5 * (1 + cos(M_PI * (rolloff_len - i) / rolloff_len - M_PI));
         }
     }
-
-    if (len_tag_key.empty()) {
-        set_output_multiple(d_output_size);
+    if (d_len_tag_key.empty()) {
+        // noutput_items is set to be a multiple of the largest possible output size.
+        // It is always OK to return less (in case of the shorter CP).
+        set_output_multiple(d_fft_len + d_cp_max);
     } else {
+        // Avoid automatic tag propagation and propagate them manually.
         set_tag_propagation_policy(TPP_DONT);
     }
 }
 
 ofdm_cyclic_prefixer_impl::~ofdm_cyclic_prefixer_impl() {}
 
-
 int ofdm_cyclic_prefixer_impl::calculate_output_stream_length(
     const gr_vector_int& ninput_items)
 {
-    int nout = ninput_items[0] * d_output_size + d_delay_line.size();
-    return nout;
+    int noutput_items = ninput_items[0] * (d_cp_max + d_fft_len) +
+                        (d_len_tag_key.empty() ? 0 : d_delay_line.size());
+    return noutput_items;
 }
 
 
@@ -112,49 +156,59 @@ int ofdm_cyclic_prefixer_impl::work(int noutput_items,
     gr_complex* in = (gr_complex*)input_items[0];
     gr_complex* out = (gr_complex*)output_items[0];
     int symbols_to_read = 0;
-
-    // 1) Figure out if we're in freewheeling or packet mode
-    if (!d_length_tag_key_str.empty()) {
+    // 1) Figure out if we're in freewheeling or packet mode.
+    if (!d_len_tag_key.empty()) {
         symbols_to_read = ninput_items[0];
-        noutput_items = symbols_to_read * d_output_size + d_delay_line.size();
     } else {
-        symbols_to_read = std::min(noutput_items / (int)d_output_size, ninput_items[0]);
-        noutput_items = symbols_to_read * d_output_size;
+        symbols_to_read =
+            std::min(noutput_items / (int)(d_fft_len + d_cp_max), ninput_items[0]);
     }
-
-    // 2) Do the cyclic prefixing and, optionally, the pulse shaping
+    noutput_items = 0;
+    // 2) Do the cyclic prefixing and, optionally, the pulse shaping.
     for (int sym_idx = 0; sym_idx < symbols_to_read; sym_idx++) {
-        memcpy((void*)(out + d_cp_size), (void*)in, d_fft_len * sizeof(gr_complex));
-        memcpy((void*)out,
-               (void*)(in + d_fft_len - d_cp_size),
-               d_cp_size * sizeof(gr_complex));
+        memcpy(static_cast<void*>(out + d_cp_lengths[d_state]),
+               static_cast<void*>(in),
+               d_fft_len * sizeof(gr_complex));
+        memcpy(static_cast<void*>(out),
+               static_cast<void*>(in + d_fft_len - d_cp_lengths[d_state]),
+               d_cp_lengths[d_state] * sizeof(gr_complex));
         if (d_rolloff_len) {
             for (int i = 0; i < d_rolloff_len - 1; i++) {
                 out[i] = out[i] * d_up_flank[i] + d_delay_line[i];
+                /* This is basically a cyclic suffix, but completely shifted into the next
+                   symbol. The data rate does not change. */
                 d_delay_line[i] = in[i] * d_down_flank[i];
             }
         }
         in += d_fft_len;
-        out += d_output_size;
-    }
-
-    // 3) If we're in packet mode:
-    //    - flush the delay line, if applicable
-    //    - Propagate tags
-    if (!d_length_tag_key_str.empty()) {
-        if (d_rolloff_len) {
-            for (unsigned i = 0; i < d_delay_line.size(); i++) {
-                *out++ = d_delay_line[i];
-            }
-            d_delay_line.assign(d_delay_line.size(), 0);
-        }
+        out += d_fft_len + d_cp_lengths[d_state];
+        // Raise the number of noutput_items depending on how long the current output was.
+        noutput_items += d_fft_len + d_cp_lengths[d_state];
+        // Propagate tags.
+        unsigned last_state = d_state > 0 ? d_state - 1 : d_cp_lengths.size() - 1;
         std::vector<tag_t> tags;
-        get_tags_in_range(tags, 0, nitems_read(0), nitems_read(0) + symbols_to_read);
+        get_tags_in_range(
+            tags, 0, nitems_read(0) + sym_idx, nitems_read(0) + sym_idx + 1);
         for (unsigned i = 0; i < tags.size(); i++) {
-            tags[i].offset =
-                ((tags[i].offset - nitems_read(0)) * d_output_size) + nitems_written(0);
+            tags[i].offset = ((tags[i].offset - nitems_read(0)) *
+                              (d_fft_len + d_cp_lengths[last_state])) +
+                             nitems_written(0);
             add_item_tag(0, tags[i].offset, tags[i].key, tags[i].value);
         }
+        // Finally switch to next state.
+        ++d_state %= d_cp_lengths.size();
+    }
+    /* 3) If we're in packet mode:
+          - flush the delay line, if applicable */
+    if (!d_len_tag_key.empty()) {
+        if (d_rolloff_len) {
+            std::memcpy(static_cast<void*>(out),
+                        static_cast<void*>(d_delay_line.data()),
+                        sizeof(gr_complex) * d_delay_line.size());
+            d_delay_line.assign(d_delay_line.size(), 0);
+            // Make last symbol a bit longer.
+            noutput_items += d_delay_line.size();
+        }
     } else {
         consume_each(symbols_to_read);
     }
diff --git a/gr-digital/lib/ofdm_cyclic_prefixer_impl.h b/gr-digital/lib/ofdm_cyclic_prefixer_impl.h
index 50b05f95d4..4e4cab5ddd 100644
--- a/gr-digital/lib/ofdm_cyclic_prefixer_impl.h
+++ b/gr-digital/lib/ofdm_cyclic_prefixer_impl.h
@@ -1,6 +1,6 @@
 /* -*- c++ -*- */
 /*
- * Copyright 2013 Free Software Foundation, Inc.
+ * Copyright 2013, 2018 Free Software Foundation, Inc.
  *
  * This file is part of GNU Radio
  *
@@ -24,6 +24,7 @@
 #define INCLUDED_DIGITAL_OFDM_CYCLIC_PREFIXER_IMPL_H
 
 #include <gnuradio/digital/ofdm_cyclic_prefixer.h>
+#include <vector>
 
 namespace gr {
 namespace digital {
@@ -31,26 +32,34 @@ namespace digital {
 class ofdm_cyclic_prefixer_impl : public ofdm_cyclic_prefixer
 {
 private:
-    size_t d_fft_len;
-    //! FFT length + CP length in samples
-    size_t d_output_size;
-    //! Length of the cyclic prefix in samples
-    int d_cp_size;
+    //! FFT length
+    int d_fft_len;
+    //!  State, that determines the current output length used.
+    unsigned d_state;
+    //! Variable being initialized with the largest CP.
+    int d_cp_max;
+    //! Variable being initialized with the smallest CP.
+    int d_cp_min;
     //! Length of pulse rolloff in samples
     int d_rolloff_len;
+    //! Vector, that holds different CP lengths
+    std::vector<int> d_cp_lengths;
     //! Buffers the up-flank (at the beginning of the cyclic prefix)
     std::vector<float> d_up_flank;
     //! Buffers the down-flank (which trails the symbol)
     std::vector<float> d_down_flank;
+    //! Vector, that holds tail of the predecessor symbol.
     std::vector<gr_complex> d_delay_line; // We do this explicitly to avoid outputting
                                           // zeroes (i.e. no history!)
+    //! Holds the length tag key.
+    const std::string d_len_tag_key;
 
 protected:
     int calculate_output_stream_length(const gr_vector_int& ninput_items);
 
 public:
-    ofdm_cyclic_prefixer_impl(size_t input_size,
-                              size_t output_size,
+    ofdm_cyclic_prefixer_impl(int fft_len,
+                              const std::vector<int>& cp_lengths,
                               int rolloff_len,
                               const std::string& len_tag_key);
     ~ofdm_cyclic_prefixer_impl();
diff --git a/gr-digital/python/digital/qa_ofdm_cyclic_prefixer.py b/gr-digital/python/digital/qa_ofdm_cyclic_prefixer.py
index fc486fa6a2..665236cd03 100644
--- a/gr-digital/python/digital/qa_ofdm_cyclic_prefixer.py
+++ b/gr-digital/python/digital/qa_ofdm_cyclic_prefixer.py
@@ -1,26 +1,27 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
+#
+# Copyright 2007-2018 Free Software Foundation, Inc.
 #
-# Copyright 2007,2010,2011,2013,2014 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 GNU Radio; see the file COPYING.  If not, write to
 # the Free Software Foundation, Inc., 51 Franklin Street,
 # Boston, MA 02110-1301, USA.
-# 
-
-from __future__ import division
+#
+"""
+Unit tests for OFDM cyclic prefixer.
+"""
 
 from gnuradio import gr, gr_unittest, digital, blocks
 import pmt
@@ -51,7 +52,7 @@ class test_ofdm_cyclic_prefixer (gr_unittest.TestCase):
         fft_len = 8
         cp_len = 2
         rolloff = 2
-        expected_result = (7.0 / 2,       8, 1, 2, 3, 4, 5, 6, 7, 8, # 1.0/2
+        expected_result = (7.0 / 2,         8, 1, 2, 3, 4, 5, 6, 7, 8, # 1.0/2
                            7.0 / 2+1.0 / 2, 8, 1, 2, 3, 4, 5, 6, 7, 8)
         src = blocks.vector_source_c(list(range(1, fft_len+1)) * 2, False, fft_len)
         cp = digital.ofdm_cyclic_prefixer(fft_len, fft_len + cp_len, rolloff)
@@ -65,7 +66,7 @@ class test_ofdm_cyclic_prefixer (gr_unittest.TestCase):
         fft_len = 8
         cp_len = 2
         tag_name = "ts_last"
-        expected_result = (7.0 / 2,       8, 1, 2, 3, 4, 5, 6, 7, 8, # 1.0/2
+        expected_result = (7.0 / 2,         8, 1, 2, 3, 4, 5, 6, 7, 8, # 1.0/2
                            7.0 / 2+1.0 / 2, 8, 1, 2, 3, 4, 5, 6, 7, 8, 1.0 / 2)
         tag2 = gr.tag_t()
         tag2.offset = 1
@@ -84,7 +85,75 @@ class test_ofdm_cyclic_prefixer (gr_unittest.TestCase):
         ]
         self.assertEqual(tags, expected_tags)
 
+    def test_wo_tags_no_rolloff_multiple_cps(self):
+        "Two CP lengths, no rolloff and no tags."
+        fft_len = 8
+        cp_lengths = (3, 2, 2)
+        expected_result = (5, 6, 7, 0, 1, 2, 3, 4, 5, 6, 7, # 1
+                           6, 7, 0, 1, 2, 3, 4, 5, 6, 7,    # 2
+                           6, 7, 0, 1, 2, 3, 4, 5, 6, 7,    # 3
+                           5, 6, 7, 0, 1, 2, 3, 4, 5, 6, 7, # 4
+                           6, 7, 0, 1, 2, 3, 4, 5, 6, 7,    # 5
+        )
+        src = blocks.vector_source_c(list(range(fft_len))*5, False, fft_len)
+        cp = digital.ofdm_cyclic_prefixer(fft_len, cp_lengths)
+        sink = blocks.vector_sink_c()
+        self.tb.connect(src, cp, sink)
+        self.tb.run()
+        self.assertEqual(sink.data(), expected_result)
 
-if __name__ == '__main__':
-    gr_unittest.run(test_ofdm_cyclic_prefixer, "test_ofdm_cyclic_prefixer.xml")
+    def test_wo_tags_2s_rolloff_multiple_cps(self):
+        "Two CP lengths, 2-sample rolloff and no tags."
+        fft_len = 8
+        cp_lengths = (3, 2, 2)
+        rolloff = 2
+        expected_result = (6.0/2,7,8,1,2,3,4,5,6,7,8,        #1
+                           7.0/2 + 1.0/2,8,1,2,3,4,5,6,7,8,  #2
+                           7.0/2 + 1.0/2,8,1,2,3,4,5,6,7,8,  #3
+                           6.0/2 + 1.0/2,7,8,1,2,3,4,5,6,7,8,#4
+                           7.0/2 + 1.0/2,8,1,2,3,4,5,6,7,8   #5
+        )
+        src = blocks.vector_source_c(list(range(1, fft_len+1))*5, False, fft_len)
+        cp = digital.ofdm_cyclic_prefixer(fft_len, cp_lengths, rolloff)
+        sink = blocks.vector_sink_c()
+        self.tb.connect(src, cp, sink)
+        self.tb.run()
+        self.assertEqual(sink.data(), expected_result)
+
+    def test_with_tags_2s_rolloff_multiples_cps(self):
+        "Two CP lengths, 2-sample rolloff and tags."
+        fft_len = 8
+        cp_lengths = (3, 2, 2)
+        rolloff = 2
+        tag_name = "ts_last"
+        expected_result = (
+            6.0/2, 7, 8, 1, 2, 3, 4, 5, 6, 7, 8,           #1
+            7.0/2+1.0/2, 8, 1, 2, 3, 4, 5, 6, 7, 8, 1.0/2  #Last tail
+        )
+        # First test tag
+        tag0 = gr.tag_t()
+        tag0.offset = 0
+        tag0.key = pmt.string_to_symbol("first_tag")
+        tag0.value = pmt.from_long(24)
+        # Second test tag
+        tag1 = gr.tag_t()
+        tag1.offset = 1
+        tag1.key = pmt.string_to_symbol("second_tag")
+        tag1.value = pmt.from_long(42)
+        src = blocks.vector_source_c(list(range(1, fft_len+1)) * 2, False, fft_len, (tag0, tag1))
+        cp = digital.ofdm_cyclic_prefixer(fft_len, cp_lengths, rolloff, tag_name)
+        sink = blocks.tsb_vector_sink_c(tsb_key=tag_name)
+        self.tb.connect(src, blocks.stream_to_tagged_stream(gr.sizeof_gr_complex, fft_len, 2, tag_name), cp, sink)
+        self.tb.run()
+        self.assertEqual(sink.data()[0], expected_result)
+        tags = [gr.tag_to_python(x) for x in sink.tags()]
+        tags = sorted([(x.offset, x.key, x.value) for x in tags])
+        expected_tags = [
+            (0, "first_tag", 24),
+            (fft_len + cp_lengths[0], "second_tag", 42)
+        ]
+        self.assertEqual(tags, expected_tags)
 
+
+if __name__ == '__main__':
+    gr_unittest.run(test_ofdm_cyclic_prefixer)
author	Maximilian Stiefel <stiefel.maximilian@online.de>	2020-01-07 17:03:59 -0800
committer	Martin Braun <martin.braun@ettus.com>	2020-01-08 10:19:44 -0800
commit	445aa4792dcdf4a8bf14600e6d931451e36f0eaa (patch)
tree	8a011d807a5f30fdf8cac945b5ba294a0937d5af
parent	90c49ef6d4d215f1db01f591d682947fea727655 (diff)