331 lines
33 KiB
Python
331 lines
33 KiB
Python
|
|
Help={'-iCNR-':'Reference C/N [dB]\n\nReference Carrier to Noise Ratio in decibels : 10 log (C/N), where C is the '
|
|
'Carrier\'s power and N is the Noise\'s Power, both are measured in the reference '
|
|
'Channel Bandwidth.\n\nThe Carrier\'s power if often named Signal\'s Power and the Carrier to Noise Ratio'
|
|
' is often named Signal to Noise Ratio.',
|
|
'-iBW-':'Reference BW [MHz]\n\nReference Channel Bandwidth, this is a key parameter of the communication channel.'
|
|
'\n\nThis bandwidth is usually a degree of freedom of the system design, eventually constrained by technological'
|
|
' constraints and various kind of frequency usage regulations.',
|
|
'-iC_N0-':'Carrier Power to Noise Power Density Ratio : C/N\N{SUBSCRIPT ZERO}\n\nCarrier\'s power (in Watts) '
|
|
'divided by the Noise Spectral Power Density (in Watts per MHz), the result\'s units are MHz.',
|
|
'-iBRinf-':'Theoretical BR at infinite BW : 1.44 C/N\N{SUBSCRIPT ZERO}\n\nBit Rate theoretically achievable when '
|
|
'the signal occupies an infinite Bandwidth, this value is a useful asympotical limit.',
|
|
'-iBRunit-':'Theoretical BR at Spectral Efficiency = 1 : C/N\N{SUBSCRIPT ZERO}\n\nBit Rate theoretically '
|
|
'achievable at a Spectral Efficiency = 1 : Bit Rate in Mbps = Bandwith in MHz.'
|
|
'\n\nThe corresponding value, deduced from the Shannon\'s formula is given by C/N\N{SUBSCRIPT ZERO}.',
|
|
'-iBRbw-':'Theoretical BR at Reference (BW,C/N)\n\nBit Rate theoretically achievable when the Bandwidth is '
|
|
'constrained to the given reference value.',
|
|
'-iCNRlin-':'C / N = C / (N\N{SUBSCRIPT ZERO}.B)\n\nReference Carrier to Noise Ratio (or Signal to Noise Ratio).'
|
|
' The C/N Ratio or CNR is usually given in dBs or 10 log (C/N). '
|
|
'\n\nAlthough the logarithm is convenient for many evaluations (multiplications become additions), '
|
|
'it\'s also good to consider the ratio itself (named here Linear '
|
|
'Format) to get some physical sense of the power ratio.'
|
|
'\n\nThe Carrier to Noise Ratio in linear format, is the value used in the Shannon\'s formula.',
|
|
'-iBRmul-':'Bit Rate Increase Factor\n\nBit Rate multiplying factor achieved when the Bandwidth and the Power '
|
|
'and multiplied by a given set of values.',
|
|
'-iCmul-':'Power Increase Factor\n\nArbitrary multiplying factor applied to the Carrier\'s Power, for '
|
|
'sensitivity analysis.',
|
|
'-iBWmul-':'BW Increase Factor\n\nArbitrary multiplying factor applied to the Carrier\'s Bandwidth, for '
|
|
'sensitivity analysis.',
|
|
'-CRC-':'Cyclic Redundancy Check of the input parameters, for changes identification purposes.\n\n'
|
|
'https://en.wikipedia.org/wiki/Cyclic_redundancy_check',
|
|
'Advanced': 'The model assumes that the communication channel is \"AWGN\", just Adding White Gaussian Noise to '
|
|
'the signal. This noise is supposed to be random and white which means that noise at a given time is '
|
|
'independent of noise at any other time, this implies that the noise has a flat and infinite spectrum.'
|
|
'This noise is also supposed to be Gaussian which means that its probability density function follows a '
|
|
'Gaussian law, with a variance associated to the Noise\'s power.\n\n'
|
|
'Although these assumptions seem very strong, they are quite accurately matching the cases of interest. '
|
|
'Many impairments are actually non linear and/or non additive, but just combining equivalent C/N of all '
|
|
'impairments as if they were fully AWGN is in most of the cases very accurate.'
|
|
'The reason for that is that the sum of random variables of unknown laws always tend to Gaussian and that '
|
|
'in most systems, thermal noise is dominating, is actually white and gaussian and is whitening the rest.\n\n'
|
|
'The tool accepts lists of comma separated CNRs which will be combined in that way. \n\n'
|
|
'In satellite systems, the noise is mainly coming from the electronics of the radio front end, the ground '
|
|
'seen by the antenna, the stars and the atmospheric attenuator. In case of rain, the signal is punished twice '
|
|
': the attenuation makes it weaker and the rain attenuator generates noise added to the overall noise.\n\n'
|
|
'Overall the Shannon Limit is a pretty convenient tool to predict the real performances of communication '
|
|
'systems and even more importantly to get a sense of the role of the key design parameters.',
|
|
'-iShannon-':'The Shannon Limit allows to evaluate the theoretical capacity achievable over a communication '
|
|
'channel.\n\nAs a true genius, Claude Shannon has funded the communication theory, the information theory '
|
|
'and more (click the Wikipedia button for more info).\n\nThis equation is fundamental for the evaluation of '
|
|
'communication systems. It is an apparently simple but extremely powerful tool to guide communication systems\''
|
|
' designs.\n\nThis equation tells us what is achievable, not how to achieve it. It took almost 50 years to '
|
|
'approach this limit with the invention of Turbo codes.\n\nIn the satellite domain, DVB-S2x, using LDPC codes '
|
|
'iteratively decoded (Turbo-Like), is only 1 dB away from this limit.',
|
|
'Help': 'Recommendations for using the tool\n\nThe first purpose of the tool is educational, allowing people to '
|
|
'better understand the physics of communications and the role of key parameters.\n\n'
|
|
'The user should try multiple values in all the fields one per one, explore the graphs and try to '
|
|
'understand the underlying physics.\n\n'
|
|
'The units for the different figures are as explicit as possible to facilitate the exploration.\n\n'
|
|
'All labels can be \"clicked\" to get information about associated item. All values (including this text)'
|
|
' can be copy/pasted for further usage.'
|
|
}
|
|
|
|
Help2={'-iFreq-':'Frequency [GHz]\n\nFrequency of the electromagnetic wave supporting the communication in GHz '
|
|
'(billions of cycles per second).\n\nFor satellite downlink (satellite to terminal), frequency bands '
|
|
'and frequencies are typically : L : 1.5 GHz , S : 2.2 GHz , C : 4 GHz , Ku : 12 GHz, Ka : 19 GHz, '
|
|
'Q : 40 GHz',
|
|
'-iSatAlt-':'Satellite Altitude [km]\n\nThe position of the satellite is expressed in latitude, longitude, '
|
|
'altitude. The program doesnt simulate the orbit, any satellite coordinates can be used. '
|
|
'A GEO satellite has a latitude of zero degrees and an altitude of 35786 km. LEO satellites '
|
|
'have an altitude lower than 2000 km. MEO\'s altitudes are between LEO and GEO : the O3B '
|
|
'constellation\'s altitude is 8063 km',
|
|
'-iSatLatLong-':'Satellite Latitude and Longitude [\N{DEGREE SIGN}]\n\nThe position of the satellite is '
|
|
'expressed in latitude, longitude, altitude. The program doesnt simulate the orbit, any '
|
|
'satellite coordinates can be used. A GEO satellite has a latitude of zero degrees and an '
|
|
'altitude of 35786 km. LEO satellites have an altitude lower than 2000 km. MEO\'s altitudes are'
|
|
' between LEO and GEO : the O3B constellation\'s altitude is 8063 km',
|
|
'-iGSLatLong-':'Ground Station Latitude and Longitude [\N{DEGREE SIGN}]\n\nThe position of the ground station '
|
|
'is expressed in latitude, longitude (the ground station is assumed to be at the surface of '
|
|
'the earth).\n\nThe position of the ground station is affecting the link availability due to'
|
|
' the differences in weather statistics at different locations on earth (tropical regions have '
|
|
'very heavy rains attenuating dramatically signals at high frequencies). It is also impacting '
|
|
'the elevation angle at which the satellite is seen and thus the length of the path in the rain.'
|
|
'\n\nThe position of the ground station is also impacting the overall path length and thus the '
|
|
'path dispersion loss.\n\nUseful link to find coordinates of interest : '
|
|
'https://www.gps-coordinates.net',
|
|
'-iAvail-':'Desired Link Availability [%]\n\nThe link availability in percentage of the time is a key '
|
|
'performance indicator for satellite communications.\n\nIn this program the only cause of '
|
|
'unavailability modelled in a probabilistic way is the attenuation caused by the atmosphere. A high '
|
|
'desired link availability corresponds to a high signal attenuation : only rare and severe weather '
|
|
'events exceeding this attenuation can interrupt the link.\n\nFor example for an availability of'
|
|
'99.9%, the attenuation considered in the link sizing is only exceeded for 0.1% of the time.',
|
|
'-iPathLength-':'Path Length [km] @ Elevation [\N{DEGREE SIGN}]\n\nDistance in kilometers from the satellite '
|
|
'to the ground station and elevation angle at which the satellite is seen. The actual distance'
|
|
' depends on the satellite\'s altitude and on the relative positions of the satellite and the '
|
|
'ground station.\n\nThe minimum path length is the satellite altitude, achieved when the ground'
|
|
' station is under the satellite (elevation = 90\N{DEGREE SIGN}).\n\nA negative elevation '
|
|
'implies that the satellite is not visible (beyond the horizon).',
|
|
'-iAtmLoss-':'Overall Atmospheric Attenuation [dB]\n\nThe Atmosphere is affecting radio wave propagation '
|
|
'with a signal attenuation caused by rain precipitations and clouds, by scintillation and '
|
|
'multi path effects, by sand and dust storms and also by atmospheric gases. \n\n'
|
|
'Simply speaking, the attenuation is increasing with the rain intensity and with the signal '
|
|
'frequency. C band is almost unaffected, Ku band is significantly affected, Ka band is severely '
|
|
'affected, Q band is dramatically affected\n\nThe overall attenuation depends on the actual '
|
|
'geographical location and on actual weather events. By nature, it is is thus statistical '
|
|
'(considering the past) or probabilistic (considering the future).\n\nAll effects included, '
|
|
'here are typical attenuation figures exceeded for 0.1% of the time in Europe from the GEO orbit '
|
|
': Ku: 2.5 dB, Ka: 6.9 dB, 22 dB \n\n'
|
|
'The program uses ITU-Rpy, python implementation of the ITU-R P Recommendations: '
|
|
'https://itu-rpy.readthedocs.io/en/latest/index.html',
|
|
'-iHPA-':'HPA Power at operating point [W]\n\nPower of the High Power Amplifier used as a last stage of '
|
|
'amplification in the satellite payload.'
|
|
'The value in watts is the value at operating point and for the carrier of interest.\n\n'
|
|
'Some satellites operate their HPAs at saturation in single carrier mode (typical DTH case).'
|
|
'Other satellites operate in multicarrier mode and reduced power (3dB Output Back Off is typical '
|
|
'for satellites serving VSATs)',
|
|
'-iSBeam-':'Satellite Half Power Beam Diameter [\N{DEGREE SIGN}]\n\nBeam diameter expressed as an angle at '
|
|
'satellite level. The power radiated at the edge of this beam is half of the power radiated at '
|
|
'the peak of the beam (on-axis value).\n\n'
|
|
'The beam evaluated is a basic one with simple illumination of a parabolic reflector\n\n'
|
|
'Typical beam size : 0.4-1.4 degrees for GEO HTS satellites, 3..6 degrees for GEO DTH satellites.',
|
|
'-iGOff-': 'Gain Offset from Peak [dB]\n\nThis offset allows to simulate terminals which are not all at '
|
|
'the beam peak. A 3 dB value would simulate a worst case position in a 3dB beam, typical approach '
|
|
'used in DTH. In single feed per beam HTS, a 1 dB value would give a typical median performance.'
|
|
'If you know the EIRP you have, the best is to iterate this value to get this EIRP '
|
|
'(the process will allow you to get a feeling of the tradeoff power / footprint size / EIRP. ',
|
|
'-iLoss-':'Output Section Losses [dB]\n\nLoss of signal\'s power in the path connecting the HPA to the '
|
|
'antenna. This loss is associated with filters, waveguide sections, switches ...\n\n'
|
|
'Typical value : 2.5 dB for large classical satellites, 1 dB for active antennas with HPAs close to '
|
|
'the feeds. If the power value is given at antenna level, the value should just be set to zero.',
|
|
'-iSCIR-':'Satellite C/I [dB]\n\nEffect of signal impairments associated with satellite implementation,'
|
|
'expressed as a signal to impairment noise ratio to be combined with the intrinsic Signal to Noise '
|
|
'Ratio affecting the link. Typical impairments are : intermodulation in the HPA, filtering effects, '
|
|
'oscillator\'s phase noise ...\n\n'
|
|
'The tool supports comma separated lists of C/I or C/N values expressed in dB. In addition to '
|
|
'satellites impairments, one can use this feature to also simulate infrastructure C/N, uplink C/N, '
|
|
'uplink interferences ...',
|
|
'-iOPow-':'Output Power [W]\n\nThe output power in watts at antenna output is associated with the useful '
|
|
'signal carrying user\'s information. It is also common to express this value in dBs (dBs transform '
|
|
'multiplications in additions, easier for human computation. Nevertheless, reasoning in watts tells '
|
|
'more about the physics.',
|
|
'-iSGain-':'Satellite Antenna Gain \n\nAn antenna concentrating the signal in the direction of the users is '
|
|
'almost always required to compensate for the path loss associated with the distance from the '
|
|
'satellite to the terminal.\n\nThe antenna gain is the ratio between the signal radiated '
|
|
'on the axis of the antenna (direction of maximum radiation) and the signal radiated by an '
|
|
'antenna radiating equally in all directions (for the same input power).\n\n'
|
|
'Antenna gains are without units but can be expressed in dB for convenience : dBi = dB relative to'
|
|
' isotropic antenna (antenna radiating equally in all directions)',
|
|
'-iEIRP-':'Equivalent Isotropic Radiated Power\n\nThe product Power x Gain expressed in Watts is a convenient '
|
|
'characterisation of the satellite radiation capability. It does correspond to the power which would '
|
|
'be required for an isotropic antenna radiating in the same way in the direction of the antenna '
|
|
'considered.\n\nThere is no "power creation" of course : for the directive antenna, the integral of '
|
|
'the radiated signal over a sphere centered on the antenna is at best equal to the input power '
|
|
'(lossless antenna).\n\n'
|
|
'As the value in watts is usually pretty big, a value in dBW is more convenient '
|
|
'for practical human computations.',
|
|
'-iPLoss-':'Path Dispersion Loss\n\nAssuming communication in free space (thus also in the vacuum), '
|
|
'this figure characterises the effect'
|
|
' of the distance from the satellite to the terminal. It gives an attenuation equivalent to the '
|
|
'inverse ratio of the power reaching one square meter at the terminal side and the equivalent '
|
|
'isotropic radiated power at satellite level.\n\n'
|
|
'This simply equals the surface in square meters of a sphere with a radius equal to the path length.'
|
|
'This attenuation is pretty big and is thus more humanly manageable in dB m\N{SUPERSCRIPT TWO}.\n\n'
|
|
'As the the vacuum is lossless, this "attenuation" is simply associated with the fact that only '
|
|
'a marginal fraction of the power radiated is captured in one square meter at destination, '
|
|
'the rest is going somewhere else.',
|
|
'-iPFD-':'Power Flux Density\n\nSignal power per square meter at the terminal side. '
|
|
'The actual power captured by the terminal is given by this value multiplied by the effective surface '
|
|
'of the terminal\'s antenna.\n\nNote that if the surface of antenna is not perpendicular to the '
|
|
'propagation direction of the radio wave, the effective surface presented to the wave is reduced '
|
|
'and less power is captured.',
|
|
'-iCPE-':'Customer Antenna Size [m]\n\nSize of the terminal antenna. A basic parabolic antenna with state of '
|
|
'the art efficiency is assumed.\n\n'
|
|
'The main source of noise is in general the terminal\'s radio front end'
|
|
' attached to the antenna. A state of the art Noise Temperature of 80K is assumed for this front end.',
|
|
'-iCPE_T-':'Noise Temperature [K]\n\nTotal Receiver\'s Clear Sky Noise Temperature. It includes all noise '
|
|
'temperature\'s contributors : receiver, sky, ground seen by the antenna... Antenna catalogs often '
|
|
'provide this value, the proposed default of 120K is a reasonable typical value. The computation '
|
|
'under rain fade conditions assumes 40K is affected by rain attenuation and the rest is not. ',
|
|
'-iCGain-':'Customer Antenna Effective Area and G/T\n\nThe effective area in square meters is expressing the '
|
|
'capability of the terminal to capture the Power Flux Density '
|
|
'(the multiplication of both give the power captured). The effective area is typically 60% of the '
|
|
'physical surface of the antenna\'s aperture.'
|
|
'This capability can also be equivalently expressed as a gain as it\'s the case for the satellite '
|
|
'antenna.\n\nThe figure of merit of a receive antenna is best expressed as the G/T ratio, '
|
|
'ratio between antenna gain and the total Noise temperature in Kelvins. The noise is mainly coming '
|
|
'from the electronics of the radio front end, the ground seen by the antenna, the stars and the '
|
|
'atmospheric attenuator.\n\nIn case of rain, the signal is punished twice : the '
|
|
'attenuation makes it weaker and the rain attenuator generates noise added to the overall noise.\n\n'
|
|
'The noise power density N\N{SUBSCRIPT ZERO} is derived from the noise temperature with a very '
|
|
'simple formula : N\N{SUBSCRIPT ZERO}=kTB (k being the Boltzmann constant), '
|
|
'the G/T leads easily to the key overall link figure of merit C/N\N{SUBSCRIPT ZERO}.',
|
|
'-iRXPow-':'RX Power at Antenna Output\n\nPower at receiver\'s antenna output before amplification. '
|
|
'This power is extremely small and can only be exploited after strong amplification.\n\n'
|
|
'As the main source of noise is in general coming from this amplification, the first amplification '
|
|
'stage has to be a Low Noise Amplifier.\n\nThis power is "C" in the Shannon\'s equation.',
|
|
'-iN0-' : 'Noise Power Density Antenna Output\n\nNoise Spectral Power Density of the radio front end under '
|
|
'actual link conditions (in Watts per MHz). '
|
|
'This PSD is N\N{SUBSCRIPT ZERO} in the Shannon\'s equation',
|
|
'-iBRinf-':'Bit Rate at infinite Bandwidth\n\nBit Rate theoretically achievable when the signal occupies an '
|
|
'infinite Bandwidth, this value is a useful asymptotic limit. The corresponding value, deduced '
|
|
'from the Shannon\'s formula is given by 1.443 C/N\N{SUBSCRIPT ZERO}\n\nThis bit rate is an '
|
|
'asymptotic value and is thus never achieved in practice.',
|
|
'-iBRhalf-':'Bit Rate at Spectral Efficiency=1/2\n\nBit Rate theoretically achievable at a Spectral Efficiency '
|
|
'= 1/2. The corresponding value, deduced from the Shannon\'s formula is given by 1.207 '
|
|
'C/N\N{SUBSCRIPT ZERO}\n\nThis operating point is bandwidth intensive ( bandwidth = 2 x bit rate). '
|
|
'Practical systems allow this operating point ( DVB-S2\'s QPSK 1/4 )',
|
|
'-iBRUnit-':'Bit Rate at Spectral Efficiency=1\n\nBit Rate theoretically achievable at a Spectral Efficiency '
|
|
'= 1. The corresponding value, deduced from the Shannon\'s formula is given by '
|
|
'C/N\N{SUBSCRIPT ZERO}.\n\nThis data point has remarkable attributes : bandwidth = bit rate and '
|
|
'C/N = 1 (equivalent to 0 dB), which means Noise Power = Signal Power.',
|
|
'-iBRdouble-':'Bit Rate at Spectral Efficiency=2\n\nBit Rate theoretically achievable at a Spectral Efficiency '
|
|
'= 1. The corresponding value, deduced from the Shannon\'s formula is given by '
|
|
'0.667 C/N\N{SUBSCRIPT ZERO}.\n\nThis operating point is relatively bandwidth efficient '
|
|
'( bandwidth = 0.5 x bit rate) and is often considered as a typical setting.',
|
|
'-iBW-':'Available Bandwidth [MHz]\n\nBandwith occupied by the communication channel. This bandwidth is usually'
|
|
' a degree of freedom of the system design, eventually constrained by technological constraints and '
|
|
'various kind of frequency usage regulations. Interestingly this parameter is also often mentally '
|
|
'constrained by past usages which were driven by technological constraints at that time.',
|
|
'-iRO-':'Nyquist Filter Rolloff [%]\n\n'
|
|
'To pass a limited bandwidth channel symbol have to be mapped on pulses, "filtered" to limit the '
|
|
'Bandwidth occupied. Theoretically, filtering can be "brickwall", one symbol per second passing in '
|
|
'1 Hertz. Practically, an excess of bandwidth is required, also called "Roll-Off of the filter.\n\n'
|
|
'The filter used is designed to respect the symmetry condition expressed in the Nyquist Criterion '
|
|
'avoiding inter-symbol interferences. Such a filter is called a Nyquist Filter. '
|
|
'and the mimimum theoretical bandwidth (Roll-Off = zero) is called Nyquist Bandwidth.\n\n'
|
|
'The Roll-Off or Excess of Bandwidth is usually expressed as a percentage of the Nyquist Bandwidth.',
|
|
'-iCIR-':'Receiver\'s C/I [dB]\n\nEffect of signal impairment associated with terminal implementation, '
|
|
'expressed as a signal to noise ratio to be combined with the intrinsic Signal to Noise Ratio affecting'
|
|
' the link.\n\nImpairments are multiple : Phase Noise of the radio front end, Quantization Noise of the'
|
|
' receiver\'s Analog to Digital Conversion, effect of imperfect synchronisation ...\n\n'
|
|
'The tool supports comma separated lists of C/I or C/N values expressed in dB. In addition to the '
|
|
'overall receiver\'s impairments, one can use this feature to simulate more details : downlink '
|
|
'interferences, LNB\'s phase noise, impairment of signal distribution ...\n\nNote that signal '
|
|
'impairments associated with the satellite and the receiver are combined together with the link '
|
|
'noise to evaluate the practical bit rate.',
|
|
'-iPenalty-':'Implementation Penalty vs theory [dB]\n\nTurbo and Turbo-like Codes are known for getting '
|
|
'"almost Shannon" performances. There are however still some implementation taxes '
|
|
': codes always have a residual bit error rate, making it very low requires some CNR margin.\n\n'
|
|
'Other practical aspects also cost signal\'s energy like time and frequency synchronisation, '
|
|
'physical layer framing...\n\nDVB-S2x, using LDPC codes and modern modulation related features '
|
|
'is typically 1 dB away of the Shannon Limit in Quasi Error Free operation. Real systems also have'
|
|
' to take margins, considering a reasonable value of 0.5 dB, a total penalty of 1.5 dB can be '
|
|
'considered as typical.\n\n'
|
|
'Original Turbo codes designed with higher residual bit error rates can get much closer '
|
|
'to the Shannon Limit. ',
|
|
'-iOH-':'Higher Layers Overhead [%]\n\nThe practical usage of information bits is based on a breakdown '
|
|
'in multiple communications layers, all spending bits for the logistics of carrying user bits.'
|
|
'For example, the process of encapsulation of IP datagrams on a DVB-S2x physical layer using'
|
|
' the GSE standard costs a few percents of net bit rate, spent in framing structures, integrity '
|
|
'control bits ...\n\n'
|
|
'In a modern efficient satellite forward communication system the overhead to IP costs typically 5%',
|
|
'-iNBW-':'Nyquist Bandwidth\n\nThe modulated carrier is passing bits in groups mapped on modulation symbols.'
|
|
'Satellite modulation schemes typically map from 1 to 8 bits on each symbol passing though the channel.'
|
|
'The Bit Rate is directly linked to the symbol rate, the number of symbols per second passing '
|
|
'the channel ( BR = SR . Number of Bits per Symbol ).\n\n'
|
|
'To pass a bandwidth limited channel, symbols have to be mapped on pulses "filtered" to limit the '
|
|
'bandwidth. Theoretically, filtering can be "brickwall", one symbol per second passing in 1 Hertz.'
|
|
'Practically, an excess of bandwidth is required, also called "Roll-Off of the filter. '
|
|
'The filter used is also designed to respect the symmetry condition expressed in the Nyquist Criterion '
|
|
'avoiding inter-symbol interferences. Such a filter is thus called Nyquist Filter '
|
|
'and the minimum theoretical bandwidth (Roll-Off = zero) is called Nyquist Bandwidth.',
|
|
'-iCNRbw-':'Signal to Noise Ratio in Available BW\n\n Ratio of the Signal Power and the Noise Power Captured '
|
|
' in the available bandwidth.',
|
|
'-iCNRnyq-':'Signal to Noise Ratio in Nyquist BW\n\nRatio of the Signal Power and the Noise Power Captured '
|
|
' in the Nyquist Bandwidth = Available Bandwidth / ( 1 + Roll-Off).',
|
|
'-iCNRrcv-':'Signal to Noise Ratio at Receiver Output\n\nRatio of the Signal Power and the total Noise Power'
|
|
' captured along the complete communication chain (at receiver ouptut). This ratio is the relevant one'
|
|
' for real-life performance evaluation. It is computed by combining the Signal to Noise in the Nyquist '
|
|
'Bandwidth, the Receiver\'s C/I and the Satellite\'s C/I. Note that these 2 items are themselves '
|
|
'resulting of many items which can be detailed as comma separated lists.',
|
|
'-iBRbw-':'Theoretical Bit Rate in Available BW\n\nBit Rate theoretically achieved with zero Roll-Off in '
|
|
'the available bandwidth. This bit rate is given by a direct application of the Shannon Limit. '
|
|
'The normalized bit rate expressed as a percentage of the bit rate at infinite bandwidth is also given '
|
|
'as well as the spectral efficiency of the available bandwidth.',
|
|
'-iBRnyq-':'Theoretical Bit Rate in Nyquist BW\n\nBit Rate theoretically achieved in '
|
|
'the Nyquist bandwidth (after having removed the Nyquist Roll-Off from the available Bandwidth).'
|
|
'This bit rate is given by a direct application of the Shannon Limit.\n\nThe normalized bit rate '
|
|
'expressed as a percentage of the bit rate at infinite bandwidth is also given as well as the spectral '
|
|
'efficiency of the available bandwidth.\n\nThe efficiency in bit per symbol is also given and does '
|
|
'correspond to the classical spectral efficiency in the Nyquist bandwidth.',
|
|
'-iBRrcv-':'Practical Physcial Layer Bit Rate\n\n Practical Bit Rate achieved using real-world conditions. '
|
|
'This bit rate is evaluated by using the "all degradations included" signal to noise ratio'
|
|
'in the Shannon\'s formula.'
|
|
'This bit rate does correspond to the user bits of the Physical Layer Frames.',
|
|
'-iBRhigh-':'Practical Higher Layers Bit Rate\n\nPractical Bit Rate achieved using real-world modulation '
|
|
'and coding and modern encapsulation methods of higher layers strcutures.\n\nThis Bit Rate does '
|
|
'typically correspond to the user bits of the IP datagrams',
|
|
'-Satellite-':'The evaluation is decomposed in 3 sections:\n\n'
|
|
'1. The satellite link : satellite transmitter and path to the receiver\'s location with '
|
|
'associated key characteristics \n\n'
|
|
'2. The radio front end : antenna and amplification unit capturing as much signal as possible '
|
|
'and as little noise as possible\n\n'
|
|
'3. The base-band processing unit : unit extracting from a modulated carrier the useful '
|
|
'information bits.'
|
|
' All key functions are usually performed via digital signal processing : Nyquist filtering, '
|
|
'synchronisation, demodulation, error correction, higher layer "decapsulation"...\n\n'
|
|
'All fields are initially filled with meaningful values, you should start the exploration by '
|
|
'changing the straightforward parameters and keep the intimidating figures unchanged. '
|
|
'All parameters are "clickable" for getting associated background information.',
|
|
'-CRC1-': 'Cyclic Redundancy Check of the input parameters, for changes identification purposes.',
|
|
'-CRC2-': 'Cyclic Redundancy Check of the input parameters, for changes identification purposes.',
|
|
'-CRC3-': 'Cyclic Redundancy Check of the input parameters, for changes identification purposes.',
|
|
'Advanced': 'The Shannon Limit is a very powerful tool to analyse communication systems\' design, trade offs.'
|
|
'All capacity evaluations in this tool are based on direct application of this formula taking '
|
|
'into account real world impairments via signal to noise combinations. With this approach, '
|
|
'using the overall C/N evaluated for a practical communication link gives a good estimate of the '
|
|
'capacity achievable.\n\nApplying in addition the known average penalty of real modulation and '
|
|
'coding schemes makes it accurate enough for initial systems evaluations.\n\nThe analytic formulas '
|
|
'derived from the Shannon Limit for given spectral efficiencies are also of great help to drive '
|
|
'the thinking in practical trade-offs.\n\n'
|
|
'Additional useful links for people interested in a theoretical immersion :'
|
|
'https://en.wikipedia.org/wiki/Nyquist_ISI_criterion\n'
|
|
'https://en.wikipedia.org/wiki/Error_correction_code#Forward_error_correction\n'
|
|
'https://en.wikipedia.org/wiki/Viterbi_decoder\n'
|
|
'https://en.wikipedia.org/wiki/Turbo_code\n'
|
|
'https://en.wikipedia.org/wiki/DVB-S2\n'
|
|
'https://en.wikipedia.org/wiki/OSI_model\n',
|
|
'Help':'Recommendations for using the tool\n\nThe first purpose of the tool is educational, allowing people to '
|
|
'better understand the physics of communications and the role of key parameters\n\n'
|
|
'All labels can be \"clicked\" to get information about associated item. All values '
|
|
'(including this text) can be copy/pasted for further usage.\n\n'
|
|
'The user should try multiple values in the fields one per one (starting from the least intimidating), '
|
|
'explore the graphs and try to understand the underlying physics.\n\n'
|
|
'The units for the different figures are as explicit as possible to facilitate the exploration.\n\n'
|
|
'Despite the simplicity of the approach, the tool can also be useful to do a quick analysis of a '
|
|
'communication link with a first order approach, avoiding the trap of the illusion of precision.\n\n'
|
|
|
|
}
|
|
|