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298 lines
15 KiB
Python
298 lines
15 KiB
Python
"""
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Help texts for Shannon application.
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Cleaned-up version of Shannon_Dict.py, organized by section.
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Unicode subscripts/superscripts replaced by readable equivalents for web display.
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"""
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# ──────────────────────────────────────────────────────────────────────────────
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# Panel 1: Theoretical Exploration
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# ──────────────────────────────────────────────────────────────────────────────
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THEORY_HELP = {
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"cnr": (
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"**Reference C/N [dB]**\n\n"
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"Reference Carrier to Noise Ratio in decibels: 10·log(C/N), where C is the "
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"Carrier's power and N is the Noise's Power, both measured in the reference "
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"Channel Bandwidth.\n\n"
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"The Carrier's power is often named Signal's Power and the Carrier to Noise Ratio "
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"is often named Signal to Noise Ratio."
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),
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"bw": (
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"**Reference BW [MHz]**\n\n"
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"Reference Channel Bandwidth — a key parameter of the communication channel.\n\n"
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"This bandwidth is usually a degree of freedom of the system design, eventually "
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"constrained by technological constraints and various kinds of frequency usage regulations."
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),
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"c_n0": (
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"**Carrier Power to Noise Power Density Ratio: C/N₀**\n\n"
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"Carrier's power (in Watts) divided by the Noise Spectral Power Density "
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"(in Watts per MHz). The result's units are MHz."
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),
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"br_inf": (
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"**Theoretical BR at infinite BW: 1.44·C/N₀**\n\n"
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"Bit Rate theoretically achievable when the signal occupies an infinite Bandwidth. "
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"This value is a useful asymptotic limit."
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),
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"br_unit": (
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"**Theoretical BR at Spectral Efficiency = 1: C/N₀**\n\n"
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"Bit Rate theoretically achievable at a Spectral Efficiency = 1: "
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"Bit Rate in Mbps = Bandwidth in MHz.\n\n"
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"The corresponding value, deduced from Shannon's formula, is given by C/N₀."
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),
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"br_bw": (
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"**Theoretical BR at Reference (BW, C/N)**\n\n"
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"Bit Rate theoretically achievable when the Bandwidth is constrained "
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"to the given reference value."
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),
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"cnr_lin": (
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"**C/N = C / (N₀·B)**\n\n"
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"Reference Carrier to Noise Ratio (or Signal to Noise Ratio). "
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"The C/N Ratio is usually given in dB: 10·log(C/N).\n\n"
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"Although the logarithm is convenient for many evaluations (multiplications become additions), "
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"it's also good to consider the ratio itself (Linear Format) to get some physical sense "
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"of the power ratio.\n\n"
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"The Carrier to Noise Ratio in linear format is the value used in Shannon's formula."
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),
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"br_mul": (
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"**Bit Rate Increase Factor**\n\n"
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"Bit Rate multiplying factor achieved when the Bandwidth and the Power "
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"are multiplied by a given set of values."
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),
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"bw_mul": (
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"**BW Increase Factor**\n\n"
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"Arbitrary multiplying factor applied to the Carrier's Bandwidth, for sensitivity analysis."
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),
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"p_mul": (
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"**Power Increase Factor**\n\n"
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"Arbitrary multiplying factor applied to the Carrier's Power, for sensitivity analysis."
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),
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"shannon": (
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"**The Shannon Limit** allows to evaluate the theoretical capacity achievable over "
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"a communication channel.\n\n"
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"As a true genius, Claude Shannon founded communication theory, information theory "
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"and more (click the Wikipedia button for more info).\n\n"
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"This equation is fundamental for the evaluation of communication systems. "
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"It is an apparently simple but extremely powerful tool to guide communication systems' designs.\n\n"
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"This equation tells us what is achievable, not how to achieve it. It took almost 50 years "
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"to approach this limit with the invention of Turbo codes.\n\n"
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"In the satellite domain, DVB-S2x, using LDPC codes iteratively decoded (Turbo-Like), "
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"is only 1 dB away from this limit."
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),
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"advanced": (
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"**AWGN Channel Model**\n\n"
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"The model assumes that the communication channel is **AWGN** (Additive White Gaussian Noise). "
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"This noise is supposed to be random and white, meaning noise at a given time is independent "
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"of noise at any other time — implying a flat and infinite spectrum. "
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"This noise is also supposed to be Gaussian.\n\n"
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"Although these assumptions seem very strong, they accurately match the cases of interest. "
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"Many impairments are actually non-linear and/or non-additive, but combining equivalent C/N "
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"of all impairments as if they were fully AWGN is in most cases very accurate. "
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"The reason is that the sum of random variables of unknown laws always tends to Gaussian, "
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"and thermal noise is dominating, actually white and gaussian, and whitening the rest.\n\n"
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"The tool accepts lists of comma-separated CNRs which will be combined in that way.\n\n"
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"Overall, the Shannon Limit is a pretty convenient tool to predict the real performances "
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"of communication systems."
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),
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"help": (
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"**Recommendations for using the tool**\n\n"
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"The first purpose of the tool is educational, allowing people to better understand "
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"the physics of communications and the role of key parameters.\n\n"
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"- Try multiple values in all the fields one by one\n"
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"- Explore the graphs and try to understand the underlying physics\n"
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"- The units are as explicit as possible to facilitate the exploration\n"
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"- Click on the info icons to get information about each parameter"
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),
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}
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# ──────────────────────────────────────────────────────────────────────────────
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# Panel 2: Real World (Satellite Link Budget)
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# ──────────────────────────────────────────────────────────────────────────────
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REAL_WORLD_HELP = {
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"freq": (
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"**Frequency [GHz]**\n\n"
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"Frequency of the electromagnetic wave supporting the communication.\n\n"
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"For satellite downlink, typical bands: L: 1.5 GHz, S: 2.2 GHz, C: 4 GHz, "
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"Ku: 12 GHz, Ka: 19 GHz, Q: 40 GHz"
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),
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"sat_alt": (
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"**Satellite Altitude [km]**\n\n"
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"The position of the satellite is expressed in latitude, longitude, altitude. "
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"A GEO satellite has a latitude of 0° and an altitude of 35786 km. "
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"LEO satellites have altitudes lower than 2000 km. "
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"MEO altitudes are between LEO and GEO (O3B constellation: 8063 km)."
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),
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"sat_latlon": (
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"**Satellite Latitude and Longitude [°]**\n\n"
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"The program doesn't simulate the orbit — any satellite coordinates can be used. "
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"A GEO satellite has a latitude of 0°."
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),
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"gs_latlon": (
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"**Ground Station Lat, Lon [°]**\n\n"
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"The position of the ground station affects link availability due to weather statistics "
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"(tropical regions have very heavy rains attenuating signals at high frequencies). "
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"It also impacts the elevation angle and overall path length.\n\n"
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"[Find coordinates](https://www.gps-coordinates.net)"
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),
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"availability": (
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"**Link Availability [%]**\n\n"
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"A high desired link availability corresponds to high signal attenuation: "
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"only rare and severe weather events exceeding this attenuation can interrupt the link.\n\n"
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"For example, at 99.9% availability, the attenuation considered is only exceeded 0.1% of the time."
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),
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"path_length": (
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"**Path Length [km] @ Elevation [°]**\n\n"
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"Distance from the satellite to the ground station and elevation angle. "
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"Minimum path length = satellite altitude (elevation = 90°). "
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"A negative elevation means the satellite is not visible."
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),
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"atm_loss": (
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"**Atmospheric Attenuation [dB]**\n\n"
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"The atmosphere affects radio wave propagation with attenuation from rain, clouds, "
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"scintillation, multi-path, sand/dust storms, and atmospheric gases.\n\n"
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"Typical attenuation exceeded 0.1% of the time in Europe from GEO:\n"
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"- Ku: 2.5 dB\n- Ka: 6.9 dB\n- Q: 22 dB\n\n"
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"Uses [ITU-Rpy](https://itu-rpy.readthedocs.io/en/latest/index.html)."
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),
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"hpa": (
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"**HPA Output Power [W]**\n\n"
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"Power of the High Power Amplifier at the satellite's last amplification stage. "
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"Some satellites operate at saturation (DTH), others in multicarrier mode with "
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"reduced power (3 dB Output Back Off is typical for VSAT)."
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),
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"sat_beam": (
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"**Satellite Beam Diameter [°]**\n\n"
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"Half-power beam width. Typical values: 0.4–1.4° for GEO HTS, 3–6° for GEO DTH."
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),
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"gain_offset": (
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"**Gain Offset from Peak [dB]**\n\n"
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"Simulates terminals not at beam peak. 3 dB = worst case in 3 dB beam (DTH). "
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"1 dB = typical median performance for single feed per beam HTS."
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),
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"losses": (
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"**Output Section Losses [dB]**\n\n"
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"Signal loss between HPA and antenna (filters, waveguides, switches). "
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"Typical: 2.5 dB for classical satellites, 1 dB for active antennas."
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),
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"sat_cir": (
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"**Satellite C/I [dB]**\n\n"
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"Signal impairments from satellite implementation: intermodulation, filtering, phase noise. "
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"Supports comma-separated lists to include uplink C/N, interferences, etc."
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),
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"output_power": "**Output Power [W]** — Signal power at antenna output carrying user information.",
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"sat_gain": (
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"**Satellite Antenna Gain**\n\n"
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"Ratio between signal radiated on-axis vs. isotropic antenna. "
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"Expressed in dBi (dB relative to isotropic antenna)."
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),
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"eirp": (
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"**Equivalent Isotropic Radiated Power (EIRP)**\n\n"
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"Product Power × Gain in Watts. Represents the power required for an isotropic antenna "
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"to match the directive antenna's radiation in that direction."
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),
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"path_loss": (
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"**Path Dispersion Loss**\n\n"
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"Free-space propagation loss — simply the surface of a sphere with radius = path length. "
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"Not actual absorption, just geometric spreading."
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),
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"pfd": (
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"**Power Flux Density**\n\n"
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"Signal power per square meter at the terminal side. "
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"Actual captured power = PFD × antenna effective area."
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),
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"cpe_ant": (
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"**Customer Antenna Size [m]**\n\n"
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"Parabolic antenna with state-of-the-art efficiency (~60%)."
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),
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"cpe_temp": (
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"**Noise Temperature [K]**\n\n"
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"Total receiver's clear-sky noise temperature. Includes all contributors: "
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"receiver, sky, ground seen by antenna. Default of 120 K is a reasonable typical value."
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),
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"cpe_gain": (
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"**Antenna Effective Area and G/T**\n\n"
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"G/T is the figure of merit of a receive antenna: Gain / Noise Temperature. "
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"In case of rain, the signal is punished twice: attenuation weakens it and "
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"the rain attenuator generates additional noise."
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),
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"rx_power": "**RX Power** — Extremely small power before amplification. This is 'C' in Shannon's equation.",
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"n0": "**Noise Power Density N₀** — Noise Spectral Power Density of the radio front end.",
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"br_inf": (
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"**Bit Rate at infinite BW** — Asymptotic limit: 1.443·C/N₀. Never achieved in practice."
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),
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"br_unit": "**Bit Rate at Spectral Efficiency=1** — Bandwidth = Bit Rate and C/N = 0 dB.",
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"br_double": (
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"**Bit Rate at Spectral Efficiency=2** — Bandwidth-efficient operating point "
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"(BW = 0.5 × BR), often considered typical."
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),
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"bandwidth": (
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"**Occupied Bandwidth [MHz]**\n\n"
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"Bandwidth occupied by the communication channel — a key degree of freedom in system design."
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),
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"rolloff": (
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"**Nyquist Filter Rolloff [%]**\n\n"
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"Excess bandwidth required beyond the theoretical Nyquist minimum. "
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"The Nyquist filter avoids inter-symbol interference."
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),
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"cir": (
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"**Receiver C/I [dB]**\n\n"
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"Signal impairments from terminal: phase noise, quantization, synchronization errors. "
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"Supports comma-separated lists."
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),
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"penalty": (
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"**Implementation Penalty [dB]**\n\n"
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"DVB-S2x with LDPC codes is typically 1 dB from Shannon Limit. "
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"With 0.5 dB margin, a total of 1.5 dB is typical."
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),
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"overhead": (
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"**Higher Layers Overhead [%]**\n\n"
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"Encapsulation cost (IP over DVB-S2x via GSE). Typically ~5% for modern systems."
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),
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"cnr_bw": "**SNR in Available BW** — Signal-to-Noise Ratio in the available bandwidth.",
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"cnr_nyq": "**SNR in Nyquist BW** — SNR in Nyquist BW = Available BW / (1 + Roll-Off).",
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"cnr_rcv": (
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"**SNR at Receiver Output** — Combining link noise, satellite C/I, and receiver C/I. "
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"This is the relevant ratio for real-life performance."
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),
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"br_nyq": (
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"**Theoretical Bit Rate** — Direct application of Shannon Limit in Nyquist BW. "
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"Efficiency in bits/symbol also shown."
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),
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"br_rcv": (
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"**Practical Physical Layer Bit Rate** — Using all-degradations-included SNR "
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"in Shannon's formula."
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),
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"br_high": (
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"**Practical Higher Layers Bit Rate** — Corresponds to user bits of IP datagrams."
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),
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"satellite": (
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"The evaluation is decomposed in 3 sections:\n\n"
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"1. **Satellite Link** — transmitter and path to receiver with key characteristics\n"
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"2. **Radio Front End** — antenna and amplification capturing signal with minimal noise\n"
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"3. **Baseband Unit** — digital signal processing: filtering, synchronization, "
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"demodulation, error correction, decapsulation\n\n"
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"All fields are initially filled with meaningful values. Start by changing the "
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"straightforward parameters. All parameters have help tooltips."
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),
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"advanced": (
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"**Advanced Analysis Notes**\n\n"
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"All capacity evaluations use direct application of the Shannon formula with real-world "
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"impairments via C/N combinations. Useful links:\n\n"
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"- [Nyquist ISI Criterion](https://en.wikipedia.org/wiki/Nyquist_ISI_criterion)\n"
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"- [Error Correction Codes](https://en.wikipedia.org/wiki/Error_correction_code)\n"
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"- [Viterbi Decoder](https://en.wikipedia.org/wiki/Viterbi_decoder)\n"
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"- [Turbo Codes](https://en.wikipedia.org/wiki/Turbo_code)\n"
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"- [DVB-S2](https://en.wikipedia.org/wiki/DVB-S2)\n"
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"- [OSI Model](https://en.wikipedia.org/wiki/OSI_model)"
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),
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"help": (
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"**Recommendations**\n\n"
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"- Try multiple values one by one, starting from the least intimidating\n"
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"- Explore the graphs to understand the physics\n"
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"- Units are as explicit as possible\n"
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"- The tool can also be used for a quick first-order link analysis"
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),
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}
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