Difference between revisions of "CommNet"

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'''CommNet''' is a relay and control communication system implemented first in KSP 1.2 pre-release. Probes now have limited attitude and thrust control if they are not linked back to Kerbin or a control point via a relay antenna. <ref name="commnet">https://docs.google.com/document/d/1Tu3KnB1alOMn_VXqF31BPDbAu24HdHLiYP2V1I6b6pU/edit</ref> Antennae have limited range from which control and transmission of science data is possible.
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'''CommNet''' is a relay and control communication system implemented first in KSP 1.2 pre-release. With CommNet enabled (as a difficulty setting), antennae have limited range from which control and transmission of science data is possible. Vessels without a [[Pilot]] require a link to a control source for full control (valid control sources are a vessel with an operational [[Probe_Control_Point|Probe Control Point]], or more commonly the Deep Space Network on [[Kerbin]]). Locations may be linked either through a direct connection or indirectly via one or more relays.  
  
 +
The following table lists the maximum range for vessels with a single antenna signaling the Deep Space Network:
 
{| class="wikitable"
 
{| class="wikitable"
 +
! colspan="2" rowspan="2" | '''Antenna Type'''
 +
! colspan="3" | [[Tracking Station]] Level (Rating)
 
|-
 
|-
! Tracking Station Level !! 5k (Probes / Manned)  !! 500k (Communotron 16)  !! 5m (HG-5 High Gain)  !! 5b (DTS-M1 / RA-5) !! 50b (HG-55 / RA-50) !! 100b (Communotron 88-88 / RA-100)
+
! '''1''' (2G) !! '''2''' (50G) !! '''3''' (250G)
 
|-
 
|-
| 1 || 5Mm (halfway to Mun) || 50Mm (Minmus) || ~158Mm  || 5Gm || ~15.8Gm  || ~22.4Gm
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| <center>'''5k'''</center> || <center>'''Command pods (Built-in)'''</center>
 +
| <center>3.16Mm (25% way to Mun)</center>
 +
| <center>15.81Mm (Mun)</center>
 +
| <center>35.36Mm (75% way to Minmus)</center>
 
|-
 
|-
| 2 || ~15.8Mm (Mun) || ~158Mm (Deep Space) || 500Mm || ~15.8Gm (Duna if close) || 50Gm (Duna/Dres always, Jool if close) || ~70.7Gm
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| <center>'''500k'''</center> || <center>'''[[Communotron 16]] / [[Communotron 16-S|16-S]]'''</center>
 +
| <center>31.62Mm (67% way to Minmus)</center>
 +
| <center>158.11Mm (Kerbin SOI)</center>
 +
| <center>353.55Mm (Kerbin SOI)</center>
 
|-
 
|-
| 3 || ~22.4Mm (halfway to Minmus) || ~224Mm  || ~707Mm || ~22.4Gm (Dres if close) || ~70.7Gm  || 100Gm (Jool always, Eeloo if close)  
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| <center>'''5M'''</center> || <center>'''[[HG-5 High Gain Antenna|HG-5 High Gain]]'''</center>
 +
| <center>100Mm (Minmus)</center>
 +
| <center>500Mm (Interplanetary around Kerbin)</center>
 +
| <center>1.12Gm (Interplanetary around Kerbin)</center>
 +
|-
 +
| <center>'''2G'''</center> || <center>'''[[Communotron DTS-M1|DTS-M1]] / [[RA-2 Relay Antenna|RA-2]]'''</center>
 +
| <center>2Gm (Interplanetary around Kerbin)</center>
 +
| <center>10Gm (Moho, Eve & Duna when close)</center>
 +
| <center>22.36Gm (Moho always, Eve, Duna & Dres (barely) if close)</center>
 +
|-
 +
| <center>'''15G'''</center> || <center>'''[[Communotron HG-55|HG-55]] / [[RA-15 Relay Antenna|RA-15]]'''</center>
 +
| <center>5.48Gm (Eve when close)</center>
 +
| <center>27.39Gm (Always Moho & Eve, Duna & Dres if close)</center>
 +
| <center>61.24Gm (Dres, Jool & Eeloo if close, other planets always)</center>
 +
|-
 +
| <center>'''100G'''</center> || <center>'''[[Communotron 88-88]] / [[RA-100 Relay Antenna|RA-100]]'''</center>
 +
| <center>14.14Gm (Moho, Eve & Duna when close)</center>
 +
| <center>70.71Gm (Jool & Eeloo if close, other planets always)</center>
 +
| <center>158.11Gm (all bodies always)</center>
 
|}
 
|}
  
=Range calculation=
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== Range calculation ==
Each antenna has a "strength rating" measured in meters. It ranges from '''5k''' (5000m) for integrated default antennas available in every spacecraft, to '''100G''' (100 billion meters) for the largest dishes.
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Individual vessels do not have a fixed maximum range: whether a connection is possible between two vessels that are a given distance apart depends on the transmission strength of the vessels at ''both'' ends of the connection. Each antenna has a "power rating", measured as a unitless number, which contributes to the overall power rating of the vessel it is attached to. A connection can be established between two vessels when the geometric mean of their power ratings is greater than their separation as measured in meters.
A connection can be estabilished between two stations (craft to ground, or craft to relay) when the square root of the product of the strength ratings is greater than the distance between the two objects.
+
This is calculated as follows:
When a craft has multiple antennas, all the strength values are summed to obtain the craft strength rating.
+
{{Formula
 +
|math code = <math> Range = \sqrt{Vessel_1 \times Vessel_2} </math>
 +
|where =
 +
*<math>Range</math> is the maximum distance in meters at which two vessels can connect with each other.
 +
*<math>Vessel_1</math> and <math>Vessel_2</math> are the power ratings for the vessels that are attempting to connect to each other.
 +
}}
 +
Power ratings for antennae range from '''5k''' for the integrated antenna available in every [[Command module]], to '''100G''' for the largest dishes. Kerbin's Deep Space Network can be treated as a vessel with a rating of '''2G'''/'''50G'''/'''250G''' (depending on the level of the [[Tracking Station]]) for the purposes of calculating range.
 +
 
 +
=== Combining antennas ===
 +
When a craft has multiple, combinable antennas, the antenna's power ratings stack in a way that provides diminishing returns using the following formula:
 +
 
 +
<math> \text{Vessel Power} = \text{Strongest Antenna Power} \times \left ( \tfrac{\text{Sum of Antenna Powers}}{\text{Strongest Antenna Power}} \right ) ^ \text{Average Combinability Exponent} </math>
 +
 
 +
The vessel's Average Combinability Exponent is the average of the combinability exponent values of all antennas on the vessel, where each antenna is weighted proportionally to its respective power rating. Note that all antennas and relays have a combinability exponent value of 0.75 except for the Communotron 16 and the Communotron 16S, with values of 1.0 and 0.0 respectively. This means that the Average Combinability Exponent will always be 0.75 for a vessel containing neither of these antennae. For vessels with a Communotron 16 or 16S, the Average Combinability Exponent is calculated:
 +
 
 +
{{Formula
 +
|math code = <math>\text{Average Combinability Exponent} = \frac{P_1 C_1 + P_2 C_2 + \cdots + P_n C_n}{P_1 + P_2 + \cdots + P_n} </math>
 +
|where =
 +
*<math>\{P_1, P_2, \dots , P_n\}</math> are the power ratings of each antenna.
 +
*<math>\{C_1, C_2, \dots , C_n\}</math> are the combinability values of each respective antenna.
 +
}}
 +
For example, a vessel with a Communotron 88-88 (100G power, 0.75 combinability) and also a Communotron 16 (500k power, 1.00 combinability) would have the following as its Average Combinability Exponent:
 +
 
 +
<math> \frac{(100 \times 10^9) \times  0.75  + (500 \times  10^3) \times  1.00}{(100 \times  10^9) + (500 \times  10^3)} = 0.75000125 </math>
 +
 
 +
Antennae combinability exponent values can be found under "antennaCombinableExponent" in the part configuration files. If the value is missing, the default value of 0.75 is used.
 +
== Signal strength ==
 +
 
 +
The length of a communication link relative to its maximum range is represented by signal strength. Signal strength for a single-hop link starts at 100% at a distance of zero and decreases as distance increases, down to a signal strength of 0% at the maximum range of the link. The relationship is non-linear: the true value requires plotting the relative distance on a [[w:Cubic Hermite spline|Bezier curve]] with the keys '0 0 0 0' and '1 1 0 0'. This can be calculated as follows:
 +
 
 +
* Calculate the relative distance between the vessels (the result should be between 0.0 and 1.0): <math> 1 - \frac{\text{Distance From Link Point}}{\text{Maximum Range}} </math>
 +
* Substitute the result above into the Bezier curve equation (cubic derivation): <math>-2x^3 + 3x^2 </math> or <math> (3-2x)x^2</math>
 +
 
 +
The result is the signal strength of the link at the specified distance. Note that the above applies to a single-hop link: if the signal is being bounced through one or more relays, the signal strength is the product of the signal strengths of each link making up the path to the control point.
 +
 
 +
=== Example ===
 +
Calculating the Signal Strength between a Level 3 DSN Tracking Center and a probe around Jool at a distance of 73.4Gm from Kerbin with two Communotron 88-88 antennas:
 +
 
 +
* Max Power of Lvl 3 DSN connection: <math> 250\,000\,000\,000 </math>
 +
 
 +
* Max Power of Probe: <math> 100\,000\,000\,000 \times \left (\frac{200\,000\,000\,000}{100\,000\,000\,000}\right )^{0.75} = 168\,179\,283\,051 </math>
 +
 
 +
* Max Range of Connection: <math>\sqrt{(2.5\times 10^{11})\times (1.68\times 10^{11})} = 205\,048\,337\,625 \text{m} </math>
 +
 
 +
* Relative distance between Link Points: <math> 1 - \frac{73.4}{205} = 0.642 </math>
 +
 
 +
* Signal Strength: <math> (3-2\times 0.642)\times 0.642^2 = 0.707 = 71% </math>
 +
 
 +
Therefore the signal strength for this connection would be 71%.
 +
 
 +
== Connections through Relays ==
 +
 
 +
When considering the antenna power of your vessel, Direct Antennas and Relay Antennas combine to give you a 'Power' to calculate Signal Strength back to the KSC, however, if a different vessel is connecting through you to communicate with the KSC the Direct Antennas are disregarded in any calculations made.
 +
 
 +
=== Example ===
 +
* A vessel with a Communotron 88-88 Direct Antenna and a RA-100 Relay Antenna orbiting around Eeloo at a distance of 105Gm from the KSC, with a Level 3 DSN, will connect back to the KSC with a Signal Strength of 48% as both antennas combine to give an increased antenna 'Power' for its own direct connection.
 +
 
 +
* A vessel rendezvoused with the above craft with a measly Communotron 16 will have to communicate back to the KSC through the relay as its antenna is not strong enough to communicate with the KSC directly. As this small, probe craft will only consider the RA-100 Relay Antenna on the relay craft when calculating its connection back to the KSC, the power rating of the relay vessel drops and therefore the Signal Strength will drop to 26% (please note the calculations for these numbers have been obfuscated from the example for easy understanding of the concept).
 +
 
 +
Please keep the above in mind when creating relay vessels for you other craft to connect through in the depth of space.
 +
 
 +
== DSN Strength ==
 +
Each upgrade of the tracking center improves the strength of Kerbin's terrestrial-based Deep Space Network (DSN). Based on the provided figures, the Level 1 tracking station has an antenna strength of 2G, Level 2 is 50G, and Level 3 is 250G.
 +
 
 +
== Science Transmission ==
 +
Signal strength has no bearing on transmitting [[Science|science]] directly to the KSC, but vessels transmitting  through a relay will gain a 40% bonus to the data transmitted (to a maximum of 100% value). For example, a Gravity Scan from low Jool orbit would give 90*0.4=35 Science if transmitted directly, but if bounced through a relay with an overall strength of 100% would give 90*0.4*1.4=50.4 Science. This bonus decreases non-linearly with signal strength.
 +
 
 +
== Difficulty Settings ==
  
==Example==
+
Range Modifier = The value of this slider is a multiplier value that is applied to the power levels of all Antenna and Relay parts.
An early probe with two Communotron 16 whip antennas has a rating of 1Mm (2 x 500km). The dishes of the basic tracking station have a rating of 5Gm; their product is 5x10<sup>15</sup> m<sup>2</sup>, and the maximum range is 22.36x10<sup>6</sup> m = 22360 kilometers; enough to control a probe in [[Mun]] orbit, but not out to [[Minmus]].
 
  
= DSN Strength =
+
DSN Modifier = The value of this slider is a multiplier value that is applied to the power level of the DSN Network.
Each upgrade of the tracking center improves the strength of Kerbin's terrestrial-based Deep Space Network (DSN). Based on the provided figures, the Level 1 tracking station has an antenna strength of 5G, Level 2 is 50G, and Level 3 is 100G. This is equal to the small, medium and large relay antenna ranges respectively.
 
  
= Science Bonus =
+
== Tutorials, Calculators and Examples ==
The same document from the KSP developers states that science returned via a relay satellite will have a bonus applied (some fraction of the difference between the recovery and transmission science potential). The exact amount of the bonus depends upon signal strength.
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A Google Sheets document that can help calculate Signal Strength and Ranges for you can be found here: [http://forum.kerbalspaceprogram.com/index.php?/topic/149099-commnet-signal-strength-calculator-antenna-selector/ CommNet Signal Strength Calculator & Antenna Selector]
  
 +
Example orbits for setting up a planetary network can be found at: [[Tutorial:Ideal Orbits for Communication Satellites]]
  
These figures may change with the final release of 1.2.
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One method of setting up a full-system network can be found at [[Tutorial:Setting up a CommNet system]].
= References =
 
<references />
 

Revision as of 20:15, 12 July 2019

CommNet is a relay and control communication system implemented first in KSP 1.2 pre-release. With CommNet enabled (as a difficulty setting), antennae have limited range from which control and transmission of science data is possible. Vessels without a Pilot require a link to a control source for full control (valid control sources are a vessel with an operational Probe Control Point, or more commonly the Deep Space Network on Kerbin). Locations may be linked either through a direct connection or indirectly via one or more relays.

The following table lists the maximum range for vessels with a single antenna signaling the Deep Space Network:

Antenna Type Tracking Station Level (Rating)
1 (2G) 2 (50G) 3 (250G)
5k
Command pods (Built-in)
3.16Mm (25% way to Mun)
15.81Mm (Mun)
35.36Mm (75% way to Minmus)
500k
Communotron 16 / 16-S
31.62Mm (67% way to Minmus)
158.11Mm (Kerbin SOI)
353.55Mm (Kerbin SOI)
5M
HG-5 High Gain
100Mm (Minmus)
500Mm (Interplanetary around Kerbin)
1.12Gm (Interplanetary around Kerbin)
2G
DTS-M1 / RA-2
2Gm (Interplanetary around Kerbin)
10Gm (Moho, Eve & Duna when close)
22.36Gm (Moho always, Eve, Duna & Dres (barely) if close)
15G
HG-55 / RA-15
5.48Gm (Eve when close)
27.39Gm (Always Moho & Eve, Duna & Dres if close)
61.24Gm (Dres, Jool & Eeloo if close, other planets always)
100G
Communotron 88-88 / RA-100
14.14Gm (Moho, Eve & Duna when close)
70.71Gm (Jool & Eeloo if close, other planets always)
158.11Gm (all bodies always)

Range calculation

Individual vessels do not have a fixed maximum range: whether a connection is possible between two vessels that are a given distance apart depends on the transmission strength of the vessels at both ends of the connection. Each antenna has a "power rating", measured as a unitless number, which contributes to the overall power rating of the vessel it is attached to. A connection can be established between two vessels when the geometric mean of their power ratings is greater than their separation as measured in meters. This is calculated as follows:

Where:
  • is the maximum distance in meters at which two vessels can connect with each other.
  • and are the power ratings for the vessels that are attempting to connect to each other.

Power ratings for antennae range from 5k for the integrated antenna available in every Command module, to 100G for the largest dishes. Kerbin's Deep Space Network can be treated as a vessel with a rating of 2G/50G/250G (depending on the level of the Tracking Station) for the purposes of calculating range.

Combining antennas

When a craft has multiple, combinable antennas, the antenna's power ratings stack in a way that provides diminishing returns using the following formula:

The vessel's Average Combinability Exponent is the average of the combinability exponent values of all antennas on the vessel, where each antenna is weighted proportionally to its respective power rating. Note that all antennas and relays have a combinability exponent value of 0.75 except for the Communotron 16 and the Communotron 16S, with values of 1.0 and 0.0 respectively. This means that the Average Combinability Exponent will always be 0.75 for a vessel containing neither of these antennae. For vessels with a Communotron 16 or 16S, the Average Combinability Exponent is calculated:

Where:
  • are the power ratings of each antenna.
  • are the combinability values of each respective antenna.

For example, a vessel with a Communotron 88-88 (100G power, 0.75 combinability) and also a Communotron 16 (500k power, 1.00 combinability) would have the following as its Average Combinability Exponent:

Antennae combinability exponent values can be found under "antennaCombinableExponent" in the part configuration files. If the value is missing, the default value of 0.75 is used.

Signal strength

The length of a communication link relative to its maximum range is represented by signal strength. Signal strength for a single-hop link starts at 100% at a distance of zero and decreases as distance increases, down to a signal strength of 0% at the maximum range of the link. The relationship is non-linear: the true value requires plotting the relative distance on a Bezier curve with the keys '0 0 0 0' and '1 1 0 0'. This can be calculated as follows:

  • Calculate the relative distance between the vessels (the result should be between 0.0 and 1.0):
  • Substitute the result above into the Bezier curve equation (cubic derivation): or

The result is the signal strength of the link at the specified distance. Note that the above applies to a single-hop link: if the signal is being bounced through one or more relays, the signal strength is the product of the signal strengths of each link making up the path to the control point.

Example

Calculating the Signal Strength between a Level 3 DSN Tracking Center and a probe around Jool at a distance of 73.4Gm from Kerbin with two Communotron 88-88 antennas:

  • Max Power of Lvl 3 DSN connection:
  • Max Power of Probe:
  • Max Range of Connection:
  • Relative distance between Link Points:
  • Signal Strength:

Therefore the signal strength for this connection would be 71%.

Connections through Relays

When considering the antenna power of your vessel, Direct Antennas and Relay Antennas combine to give you a 'Power' to calculate Signal Strength back to the KSC, however, if a different vessel is connecting through you to communicate with the KSC the Direct Antennas are disregarded in any calculations made.

Example

  • A vessel with a Communotron 88-88 Direct Antenna and a RA-100 Relay Antenna orbiting around Eeloo at a distance of 105Gm from the KSC, with a Level 3 DSN, will connect back to the KSC with a Signal Strength of 48% as both antennas combine to give an increased antenna 'Power' for its own direct connection.
  • A vessel rendezvoused with the above craft with a measly Communotron 16 will have to communicate back to the KSC through the relay as its antenna is not strong enough to communicate with the KSC directly. As this small, probe craft will only consider the RA-100 Relay Antenna on the relay craft when calculating its connection back to the KSC, the power rating of the relay vessel drops and therefore the Signal Strength will drop to 26% (please note the calculations for these numbers have been obfuscated from the example for easy understanding of the concept).

Please keep the above in mind when creating relay vessels for you other craft to connect through in the depth of space.

DSN Strength

Each upgrade of the tracking center improves the strength of Kerbin's terrestrial-based Deep Space Network (DSN). Based on the provided figures, the Level 1 tracking station has an antenna strength of 2G, Level 2 is 50G, and Level 3 is 250G.

Science Transmission

Signal strength has no bearing on transmitting science directly to the KSC, but vessels transmitting through a relay will gain a 40% bonus to the data transmitted (to a maximum of 100% value). For example, a Gravity Scan from low Jool orbit would give 90*0.4=35 Science if transmitted directly, but if bounced through a relay with an overall strength of 100% would give 90*0.4*1.4=50.4 Science. This bonus decreases non-linearly with signal strength.

Difficulty Settings

Range Modifier = The value of this slider is a multiplier value that is applied to the power levels of all Antenna and Relay parts.

DSN Modifier = The value of this slider is a multiplier value that is applied to the power level of the DSN Network.

Tutorials, Calculators and Examples

A Google Sheets document that can help calculate Signal Strength and Ranges for you can be found here: CommNet Signal Strength Calculator & Antenna Selector

Example orbits for setting up a planetary network can be found at: Tutorial:Ideal Orbits for Communication Satellites

One method of setting up a full-system network can be found at Tutorial:Setting up a CommNet system.