From 183e3bfc6c5f3f1bb4e9640bfa44fb2e3dc16cbe Mon Sep 17 00:00:00 2001
From: Glenn Bradford <glenn.bradford@unimelb.edu.au>
Date: Fri, 8 Apr 2022 19:57:38 +1000
Subject: [PATCH] fix tx rrc scaling, add cfo command and time/chan est tags
---
examples/packet_phy_tx.grc | 2 +-
grc/elen90089_corr_est_cc.block.yml | 6 +++-
lib/corr_est_cc_impl.cc | 52 ++++++++++++++++++++---------
lib/corr_est_cc_impl.h | 1 +
python/packet_phy_tx.py | 2 +-
5 files changed, 45 insertions(+), 18 deletions(-)
diff --git a/examples/packet_phy_tx.grc b/examples/packet_phy_tx.grc
index 7d6128c..e91a642 100644
--- a/examples/packet_phy_tx.grc
+++ b/examples/packet_phy_tx.grc
@@ -108,7 +108,7 @@ blocks:
parameters:
alpha: excess_bw
comment: ''
- gain: nfilts/2
+ gain: nfilts
ntaps: 5*sps*nfilts
samp_rate: nfilts
sym_rate: '1.0'
diff --git a/grc/elen90089_corr_est_cc.block.yml b/grc/elen90089_corr_est_cc.block.yml
index fa8de8c..4db7551 100644
--- a/grc/elen90089_corr_est_cc.block.yml
+++ b/grc/elen90089_corr_est_cc.block.yml
@@ -19,11 +19,15 @@ inputs:
- label: in
domain: stream
dtype: complex
+
outputs:
- label: out
domain: stream
dtype: complex
-- label: out
+- label: cfo
+ domain: message
+ optional: True
+- label: corr
domain: stream
dtype: float
optional: True
diff --git a/lib/corr_est_cc_impl.cc b/lib/corr_est_cc_impl.cc
index 5cb25a7..cd9e757 100644
--- a/lib/corr_est_cc_impl.cc
+++ b/lib/corr_est_cc_impl.cc
@@ -36,6 +36,8 @@ corr_est_cc_impl::corr_est_cc_impl(const std::vector<gr_complex>& sequence,
{
set_max_noutput_items(s_nitems);
set_sequence(sequence);
+
+ message_port_register_out(pmt::mp("cfo"));
}
corr_est_cc_impl::~corr_est_cc_impl() {}
@@ -54,14 +56,14 @@ void corr_est_cc_impl::set_sequence(const std::vector<gr_complex>& sequence)
// create time-reversed conjugate of training sequence for filtering
std::vector<gr_complex> taps(sequence.size());
std::reverse_copy(sequence.begin(), sequence.end(), taps.begin());
- float scale = 0.0;
+ d_scale = 0.0;
for (size_t i = 0; i < taps.size(); i++) {
taps[i] = std::conj(taps[i]);
- scale += std::norm(taps[i]);
+ d_scale += std::norm(taps[i]);
}
- scale = 1.0 / sqrt(scale);
+ d_scale = 1.0 / sqrt(d_scale);
for (size_t i = 0; i < taps.size(); i++) {
- taps[i] *= scale;
+ taps[i] *= d_scale;
}
// set taps and block output multiple to FFT kernel's internal nsamples
@@ -150,25 +152,45 @@ int corr_est_cc_impl::work(int noutput_items,
if (corr_mag[i] > d_threshold) {
// coarse frequency estimate
double freq_est = estimate_freq_offset(&in[i]);
+
+ // single-tap (inverse) channel estimate
+ gr_complex chan_est = d_corr[i] * d_scale;
+ chan_est = conj(chan_est) / (chan_est*conj(chan_est));
+
+ // time phase estimate - center-of-mass (3 samples)
+ double nom = corr_mag[i-1] + 2*corr_mag[i] + 3*corr_mag[i+1];
+ double den = corr_mag[i-1] + corr_mag[i] + corr_mag[i+1];
+ double time_est = (nom/den) - 2.0;
+
+ // send frequency correction message
+ int offset = nitems_written(0) + i;
+ pmt::pmt_t cmd = pmt::make_dict();
+ cmd = pmt::dict_add(cmd,
+ pmt::mp("offset"),
+ pmt::from_long(offset));
+ cmd = pmt::dict_add(cmd,
+ pmt::mp("inc"),
+ pmt::from_double(-freq_est));
+ message_port_pub(pmt::mp("cfo"), cmd);
// tag output
- add_item_tag(0, nitems_written(0) + i,
- pmt::intern("corr_start"),
- pmt::from_double(corr_mag[i]),
- d_src_id);
- add_item_tag(0, nitems_written(0) + i,
- pmt::intern("freq_est"),
- pmt::from_double(freq_est),
- d_src_id);
- if (output_items.size() > 1) {
- add_item_tag(1, nitems_written(0) + i,
+ for(int ch = 0; ch < output_items.size(); ch++) {
+ add_item_tag(ch, offset,
pmt::intern("corr_start"),
pmt::from_double(corr_mag[i]),
d_src_id);
- add_item_tag(1, nitems_written(0) + i,
+ add_item_tag(ch, offset,
pmt::intern("freq_est"),
pmt::from_double(freq_est),
d_src_id);
+ add_item_tag(ch, offset,
+ pmt::intern("chan_est"),
+ pmt::from_complex(chan_est),
+ d_src_id);
+ add_item_tag(ch, offset,
+ pmt::intern("time_est"),
+ pmt::from_double(time_est),
+ d_src_id);
}
// skip remaining symbols in sequence
diff --git a/lib/corr_est_cc_impl.h b/lib/corr_est_cc_impl.h
index 9fc44e6..479dac5 100644
--- a/lib/corr_est_cc_impl.h
+++ b/lib/corr_est_cc_impl.h
@@ -28,6 +28,7 @@ private:
volk::vector<gr_complex> d_corr;
volk::vector<float> d_corr_mag;
volk::vector<float> d_y_mag;
+ float d_scale;
float d_y_accum;
int d_skip;
diff --git a/python/packet_phy_tx.py b/python/packet_phy_tx.py
index ce7df6e..831abba 100644
--- a/python/packet_phy_tx.py
+++ b/python/packet_phy_tx.py
@@ -43,7 +43,7 @@ class packet_phy_tx(gr.hier_block2):
# Variables
##################################################
self.nfilts = nfilts = 32
- self.rrc_taps = rrc_taps = firdes.root_raised_cosine(nfilts/2, nfilts,1.0, excess_bw, 5*sps*nfilts)
+ self.rrc_taps = rrc_taps = firdes.root_raised_cosine(nfilts, nfilts,1.0, excess_bw, 5*sps*nfilts)
self.taps_per_filt = taps_per_filt = len(rrc_taps)/nfilts
self.header_format_cdc_0 = header_format_cdc_0 = elen90089.header_format_cdc(digital.packet_utils.default_access_code, 3, 1)
self.hdr_encoder = hdr_encoder = fec.dummy_encoder_make(1500)
--
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