Simulations and results » History » Version 12
Version 11 (GAY, Adrien, 03/23/2015 11:43 AM) → Version 12/15 (GAY, Adrien, 03/24/2015 12:14 AM)
h1. Simulations and results
From the method described previously, we have developed three Matlab programs enabling to compute or visualize the influence of various parameters according to what is assume known or not.
h2. Computation of the MODCOD and (G/T) required:
Supposing that the specifications and frequency band are known (_Rb, R, f, B_ and _EIRP_ are known), we directly get all the parameters for the system design by following the method described previously.
_+f= 869,5 MHz B= 250 kHz PAR= 0.5 W Rb=500 bits/s R=50 km:+_
p=. !850M-MODCOD-GoT.png!
*Comment value (G/T): low BW so "high" modcod, high power allows low GoT, does not need a directive antenna*
_+f= 5 GHz B= 500 kHz EIRP= 1 W Rb=500 bits/s R=50 km:+_
p=. !5G-MODCOD-GoT.png!
We can see from these two simulations that:
* The *Comment value (G/T): higher the Bandwidth, the BW so lower the Modcod
* The higher the frequency, the higher the modcod, but high Got to compensate high free space loss, and then the higher the (G/T) and EIRP requested to compensate these losses.
Moreover, we can evaluate the requested gain of the antennas from the (G/T) values. In fact, we have been told by Mr Perrin that the receivers temperature was between 400K and 600K, depending on the quality receiver and the directivity of the antenna (looking toward the ground or not?).
Then, a (G/T) of -27.3 dB corresponds more or less to an isotropic antenna, and a (G/T) of -16.9 dB corresponds to a 9 dB gain antenna, which is easily feasible at the 5 GHz frequency.
loss (high freq) --> directive antenna*
h2. Influence of the bandwidth on the EIRP:
If the regulatory frequency for application is known, this tool enables to visualize the tradeoff between the EIRP and bandwidth to fulfil the specifications:
_+f= 869,5 MHz Rb=500 bits/s R=50 km:+_
p=. !850M-BW_vs_EIRP.png!
Comments
_+f= 5 GHz Rb=500 bits/s R=50 km:+_
p=. !5G-BW_vs_EIRP.png!
Comments
h2. Influence of the distance on the bite rate:
If the required system design is too constraining for a given specification, and then not achievable, we might lower our expectations and have a tradeoff between the desired bit rate and the range
_+f= 869,5 MHz B= 250 kHz PAR= 0.5 W+_
p=. !850M-range_vs_Bit_rate.png!
_+f= 5 GHz B= 500kHz EIRP= 1 W+_
p=. !5G-range_vs_Bit_rate.png!
We can notice the bite rate is dropping quickly with the range of transmission. Then, the video transmission can be lost if the aircraft moves just a little bit too far of the limit range.
From the method described previously, we have developed three Matlab programs enabling to compute or visualize the influence of various parameters according to what is assume known or not.
h2. Computation of the MODCOD and (G/T) required:
Supposing that the specifications and frequency band are known (_Rb, R, f, B_ and _EIRP_ are known), we directly get all the parameters for the system design by following the method described previously.
_+f= 869,5 MHz B= 250 kHz PAR= 0.5 W Rb=500 bits/s R=50 km:+_
p=. !850M-MODCOD-GoT.png!
*Comment value (G/T): low BW so "high" modcod, high power allows low GoT, does not need a directive antenna*
_+f= 5 GHz B= 500 kHz EIRP= 1 W Rb=500 bits/s R=50 km:+_
p=. !5G-MODCOD-GoT.png!
We can see from these two simulations that:
* The *Comment value (G/T): higher the Bandwidth, the BW so lower the Modcod
* The higher the frequency, the higher the modcod, but high Got to compensate high free space loss, and then the higher the (G/T) and EIRP requested to compensate these losses.
Moreover, we can evaluate the requested gain of the antennas from the (G/T) values. In fact, we have been told by Mr Perrin that the receivers temperature was between 400K and 600K, depending on the quality receiver and the directivity of the antenna (looking toward the ground or not?).
Then, a (G/T) of -27.3 dB corresponds more or less to an isotropic antenna, and a (G/T) of -16.9 dB corresponds to a 9 dB gain antenna, which is easily feasible at the 5 GHz frequency.
loss (high freq) --> directive antenna*
h2. Influence of the bandwidth on the EIRP:
If the regulatory frequency for application is known, this tool enables to visualize the tradeoff between the EIRP and bandwidth to fulfil the specifications:
_+f= 869,5 MHz Rb=500 bits/s R=50 km:+_
p=. !850M-BW_vs_EIRP.png!
Comments
_+f= 5 GHz Rb=500 bits/s R=50 km:+_
p=. !5G-BW_vs_EIRP.png!
Comments
h2. Influence of the distance on the bite rate:
If the required system design is too constraining for a given specification, and then not achievable, we might lower our expectations and have a tradeoff between the desired bit rate and the range
_+f= 869,5 MHz B= 250 kHz PAR= 0.5 W+_
p=. !850M-range_vs_Bit_rate.png!
_+f= 5 GHz B= 500kHz EIRP= 1 W+_
p=. !5G-range_vs_Bit_rate.png!
We can notice the bite rate is dropping quickly with the range of transmission. Then, the video transmission can be lost if the aircraft moves just a little bit too far of the limit range.