WIP: link budgets

.gitignore

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+.vscode
 
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.gitmodules

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+[submodule "analysis/modules/pylink"]
+	path = analysis/modules/pylink
+	url = [email protected]:stanford-ssi/pylink.git

analysis/.gitignore

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+.conda.env

analysis/README.md

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+# Analysis
+
+## Environment Setup
+
+First, use the `environment.yml` file to set up your python environment. Any version of Python roughly 3.6 or later should be fine, but we didn't test that rigourosly (we are currently using 3.9 and will upgrade to 3.10 when it comes out). Next, install all the submodules in `modules/` into your python environment (they are modified versions of pypi packages).

analysis/comms/README.md

@@ -1,2 +1,20 @@
-# Comms
-pylink-satcom
+# Link Budgets
+
+## Rough Plan of Attack
+
+Run antenna simulations in `4nec2`, and then use pylink-satcom
+to simulate the RF links, and then use Python to simulate the
+data encoding and generate plots of SNR vs Error rate. In
+addition, use Python to generate graphs of link margin over
+the course of a couple of ground pass profiles, and generate
+statistics of data per ground pass, average number of ground
+passes per day, and data throughput.
+
+<https://arxiv.org/pdf/1905.11252.pdf>
+
+## Current Needs
+
+- Figure out RX and TX efficiencies and es/n0 (not SNR) for both LoRa
+and frequency hopping.
+
+- Read more about radios and determine components with greater accuracy

analysis/comms/modulation.py

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+#!/usr/bin/env python
+
+import os
+
+import pylink
+from sband import DOWNLINK
+
+"""Example of using a complex modulation with many code options.
+Complex modulations, such as DVB-S2(X) have many different code-rate
+options available for variable/adaptive bitrates, or encoder/decoder
+capabilities, etc.  The ability to specify multiple code options and
+select the appropriate option for the circumstances (largely dependent
+upon the allocation size and the received C/N0) is included.
+"""
+
+m = DOWNLINK
+e = m.enum
+
+# Modify our boilerplate model to illustrate the coding
+m.override(e.allocation_hz, 5e6)
+m.override(e.cn0_db, 73)
+m.override(e.target_margin_db, 1)
+m.override(e.implementation_loss_db, 1)
+
+# Observe the best code option
+code = m.best_modulation_code
+print("=== Modulation: %s ===" % m.modulation_name)
+print("  Code:                         %s" % code.name)
+print("  Transmit Spectral Efficiency: %f" % code.tx_eff)
+print("  Receive Spectral Efficiency:  %f" % code.rx_eff)
+print("  Required Es/N0:               %f" % code.esn0_db)
+print("  Required Eb/N0:               %f" % code.ebn0_db)
+
+print("")
+print("=== System ===")
+print("  Transmit Spectral Efficiency: %f" % m.tx_spectral_efficiency_bps_per_hz)
+print("  Receive Spectral Efficiency:  %f" % m.rx_spectral_efficiency_bps_per_hz)
+print("  Required Demod Eb/N0:         %f" % m.required_demod_ebn0_db)
+print("  Implementation Losses:        %f" % m.implementation_loss_db)
+print("  Required Eb/N0:               %f" % m.required_ebn0_db)
+
+print("")
+print("Note how the transmit and receive spectral efficiencies are different.")

analysis/comms/sband.py

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+#!/usr/bin/env python
+
+# standard libraries
+import os
+import shutil
+import subprocess
+
+# third-party libraries
+import numpy as np
+import matplotlib.pyplot as plt
+import pylink
+
+sat_pattern = pylink.pattern_generator(3)
+
+sat_rf_chain = [
+    pylink.Element(name="Cables", gain_db=-0.05, noise_figure_db=0.75),
+    pylink.Element(name="Filter", gain_db=-3.5, noise_figure_db=3.5),
+    pylink.Element(name="Demodulator", gain_db=0, noise_figure_db=15),
+]
+
+gs_rf_chain = [
+    pylink.Element(name="Cables", gain_db=-0.75, noise_figure_db=0.75),  # TODO measure
+    pylink.Element(name="LNA", gain_db=35, noise_figure_db=2.75),  # TODO double check
+    pylink.Element(name="Filter", gain_db=-3.5, noise_figure_db=3.5),
+    pylink.Element(name="Demodulator", gain_db=0, noise_figure_db=15),
+]
+
+geometry = pylink.Geometry(
+    apoapsis_altitude_km=450, periapsis_altitude_km=450, min_elevation_deg=20
+)
+
+sat_rx_antenna = pylink.Antenna(  # TODO figure out whether there is geometry and what pointing assumptions are made
+    gain=3,
+    polarization="RHCP",
+    pattern=sat_pattern,  # TODO double check what this means
+    rx_noise_temp_k=1000,
+    is_rx=True,
+    tracking=False,
+)
+
+sat_tx_antenna = pylink.Antenna(
+    gain=3, polarization="RHCP", pattern=sat_pattern, is_rx=False, tracking=False
+)
+
+gs_rx_antenna = pylink.Antenna(
+    pattern=pylink.pattern_generator(48),  # TODO what does this mean
+    rx_noise_temp_k=300,
+    polarization="RHCP",
+    is_rx=True,
+    tracking=True,
+)
+
+gs_tx_antenna = pylink.Antenna(gain=25, polarization="RHCP", is_rx=False, tracking=True)
+
+sat_receiver = pylink.Receiver(
+    rf_chain=sat_rf_chain, implementation_loss_db=2, name="Satellite SBand Receiver"
+)
+
+gs_receiver = pylink.Receiver(rf_chain=gs_rf_chain, name="Ground SBand Receiver")
+
+gs_transmitter = pylink.Transmitter(
+    tx_power_at_pa_dbw=23, name="Ground SBand Transmitter"
+)
+
+sat_transmitter = pylink.Transmitter(
+    tx_power_at_pa_dbw=1.5, name="Satellite SBand Transmitter"
+)
+
+rx_interconnect = pylink.Interconnect(is_rx=True)
+
+
+tx_interconnect = pylink.Interconnect(is_rx=False)
+
+s_channel = pylink.Channel(
+    bitrate_hz=500e3,  # TODO double check
+    allocation_hz=5e6,  # TODO double check
+    center_freq_mhz=2450.0,
+    atmospheric_loss_db=0.5,
+    ionospheric_loss_db=0.5,
+    rain_loss_db=1,
+    multipath_fading_db=0,
+    polarization_mismatch_loss_db=3,
+)
+
+# defaults to DVB-S2X
+modulation = pylink.Modulation(name="p2400 345.6")  # TODO add frequency hopping scheme
+
+DOWNLINK = pylink.DAGModel(
+    [
+        geometry,
+        gs_rx_antenna,
+        sat_transmitter,
+        sat_tx_antenna,
+        gs_receiver,
+        s_channel,
+        rx_interconnect,
+        tx_interconnect,
+        modulation,
+        pylink.LinkBudget(name="SBand Downlink", is_downlink=True),
+    ]
+)
+
+UPLINK = pylink.DAGModel(
+    [
+        geometry,
+        sat_rx_antenna,
+        sat_receiver,
+        gs_transmitter,
+        gs_tx_antenna,
+        s_channel,
+        pylink.LinkBudget(name="SBand Uplink", is_downlink=False),
+    ]
+)