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Satellite Communication - Science topic

For RF and Satellite communication reseach and implementations
Questions related to Satellite Communication
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I am trying to execute the "satelliteScenarioViewer(sc)" command of the Multihop Regenerative Repeater Link Between two ground stations, an example of the Satellite Communications Toolbox. One error occurs stating that MATLAB has disabled some advanced graphics rendering features by switching to OpenGL software. Hardware graphics with WebGL support is required to solve this error. As my system is not compatible with this so I am trying to update software graphics by using the following command as provided in this link:-
Command: opengl('save','software')
This is again not working.
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Any new and innovative topics in this field will be appreciated; Radio Communication, Antennas and Propagation, Satellite Communication, Microwave Communication, Radio Propagation
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Research in electronic approaches that address rural connectivity deficits in cost-efficient ways would be of interest to countries that host rural populations in remote locations. (E-health is one such approach.)
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As far as I know, some types of antennas are used in satellite communications such as reflector antenna, reflectarray antenna, and array antenna. But which one of these or another antennas will be more useful in next-generation of satellite communication?
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Deployable Mesh Satellite Antenna
The next generation satellite antenna design will use the lightweight large deployable reflector antenna to provide high performance shaped and multi spot beam coverage's.
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I am looking for research idea in Satellite Communication systems for my master research. I work in Broadcasting. Your good suggestions will be highly valued. Thank you
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Hello researchers,
I need help with a dataset for calculating/ modelling path losses for telecommunications and satellite communications.
It will be great to have a load of literature on how to model path losses.
How did the Egil model was achieved?
Regards
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There is a chapter in the book: Advanced electronic communication systems by G. Tomasi that has a chapter about satellite communications. There is an example hoe one calculates the link budget between the satellite and the ground stations.
The satellite link is a line of sight channel model with the effect of elevation angel and the additional path loss due to fog and rain.
Best wishes
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Hi, I am a student who just started working at a space industry, and I want to know how to teach myself to use HFSS. I have experience with 4NEC2, but HFSS just seems much more complicated, and I was wondering if any experienced people here have tips or manuals to share? My model is a conical shape for cube satellite, at frequency of 2.4 GHz.
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Along with all the great answers above consider the HFSS book for your reference:
Best regards,
Yani
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Hello All,
Please is it possible to use MATLAB in analysing the sharing and compatibility studies between Satellite Communication systems and 5G systems using the Monte Carlo Simulation approach rather than the Minimum Coupling Loss approach?
OR the Monte Carlo Simulation approach in analysing sharing & compatibility studies is only implemented using Spectrum Engineering software (e.g. SEAMCAT) other than MATLAB?
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I think it is possible to use Monte Carlo simulation, but you need to implement it by yourself in Matlab.
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Is there any 5G ray tracing software that can simulate channel sounding at 5G.If you know any such software- open source or commercial, let me know
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Wireless Insite Software from Remcom is good soft for 5G Ray tracing channel modeling, MIMO, Massive MIMO application.
Please contact at this email.
Regards
Anil Sharma
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.
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More Precisely,
Let's, Sensor, (Sw x Sh) = 13.2 x 8.8 mm
Focal length, F = 8.8 mm (rear focal length, not 35 mm equivalent)
The flight height, H = 100 m
Video resolution, (imW x imH) = 4096 x 2160 (in pixels)
Then,
Ground Sampling Distance, (GSD) = (H * Sw) / (F * imW) (in cm)
Also, Image width footprint on the ground = (H * Sw) / (F ) (in meters)
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Good morning
I'm interested for cooperation. My reseach is treatment of signal  (colon Cancer.... ) and radio mobile for telecommunications.
can you explain your points.
good day
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I'm interested. My email ID-farhanatasnimanti99@gmail.com. Thanks in advance.
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Hello All,
I am presently enrolled as an MSc Electrical Engineering (Telecommunication Option). I have finished my coursework and about to engage in my research but I am having difficult in getting a Research Proposal Topic. I actually want to work in Satellite Communication but also finding it difficult to narrow the area of interest. With this, I am kindly asking for your assistance/guidance or any suggestion that might help. Thank you for considering my request and look forward to hearing from you.
Kind regards,
Sajor Barrie.
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Dear Sajor,
welcome,
As an electronic engineer i would like to propose you developing on board communication systems for on board satellite and in the ground station
for both control and pay load. You can choose from picosatellite up to microsatellite. The development effort covers the hard the specifications, the hardware design , the software development, the testing and trouble shooting.
Best wishes
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Satellite communication with wireless devices using OMNET++ simulation tool. I have created 5 mobile devices and set their behavior in the .cc file. They show mainly 2 behavior; signal send/receive from satellite and movement. But while simulating the source code either of the two behavior is executed (i.e, either signal send/receive or movement). Initialization of the architecture is done inside .ned file.
If anyone is following the platform, please give your suggestions; how to run the 2 behaviors simultaneously.
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You could also look at NetSim's satellite library - https://tetcos.com/satellite-communication.html, which is much easier to use than OMNET.
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Could EMF generated by a big electricity substation and / or satellite communications facility discourage microbats / interfere with microbat echolocation? Surveys using an Anabat detector in this part of northern Sydney often record few or no calls at all. It is an area with lots of bushland, so habitats are otherwise very good.
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Trying to get information
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I have heard that it may be around 23 GHz or 28 GHz.
Are we going to have unified communications Satellite and Mobile terrestrial?
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Follow
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What is meant by the "Physical Layer" in Satellite Communications?
As well as how it is different from the 7 layers OSI model of computer networking?
It would be a great help if you could give me some ideas.
Thank you in advance.
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In addition to what Radwa answered, in the 7-layer OSI model, the physical layer is layer 1. That's the layer which describes how the bits are transferred over the medium. In the case of satellite, it will typically be PSK or 16-QAM at most, single carrier, to achieve robustness with the least demands on transmit power.
The next layer up in the OSI model is the data link layer, which describes how the data frames are arranged. Such as MAC addresses, the type of frame being transmitted (meaning what the payload consists of), the size of the payload, payload size limits, and frame error checking.
So in principle, one can conceive of a satellite link only being different from other links, such as Ethernet let's say, at layer 1. And all the upper layers, from data link on up t application, being the same. Although frequently, satellite links use MPEG2-TS at layer 2, as opposed to Ethernet or other.
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The space shuttle repair and maintenance is often very challenging and require very specific Space Robotics & Automated Systems that are interconnected via Satellite Communication Systems.
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A huge question, tourism in space companies may have such interests.
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I have 24 hours dual frequency GPS observations of 10 points 
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Just a quick update: The Bern server has been changed to a new host name. The CODE maps can now be retrieved from here: ftp://ftp.aiub.unibe.ch/CODE/
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There are many things facing satellite communication in the c-band which effect on the system performance efficiency.
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C-band received signal is very weak due to the long distance from GSO to earth. Thus it is very vulnerable to interference coming from Fixed Wireless Access FWA services operating in the same or adjacent frequency bands (c-band 3.4-3.8GHz; or extended C-band 3.8-4.2GHz).
Check the following research papers covering this issue:
and;
and;
and;
With my best wishes
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The nanosatellite operating in amateur radio frequencies have limited bandwidth. 2m band have 144-146MHz and 70cm band have 434-438MHz. How much bandwidth (Maximum) we can use in this?
Norwegian Post and Telecommunication Authority (NPT) says the maximum bandwidth are limited to 18KHz and 30KHz respectively. Is this applicable for every region?
On 8th page of document Johan L. Tresvig say a regulationby norwegian goverment. What I would like to know is whether any other contries or organization set a limit to the bandwidth.I couldn't find much details about this in internet.
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Dear Dileep,
I am also interested in this information. Could please attach a link or a document about the Norwegian bandwidth limitation of the cube satellite.
From the conceptual point of view, the bandwidth required to transmit data rate rb depends on this rate, the type of modulation.
For example for binary phase shift keying PSK the minimum required bandwidth B= the bit rate = rb, in case of qpsk, the B= rb/2 and in case of frequency shift keying FSK, B= 2(delta f + rb/2) where delta f= the frequency deviation. For minimum shift keying MSK, B= approximately rb/2 like QPSK.
If the bandwidth is limited to 25 KHz, then the maximum data rate fo MSK for example rbmax= 2 B= 2x25= 50 Kb/s. Which is very enough for the cube sat control and telemetry information transmission. In cube sat the control signal is about 1200 bts/s and the telemetry and pay load signal is in the order of 9.6 Kb/s, even if one requires to transmit the 9.6 Kbls using BFSK the one can adjust delta f to be = B/2 - rb/2= (B-rb)/2= (25-9.6)/2= 7.7 KHz, which lies in the audio frequency range and therefore this type of binary frequency shift keying is called audio frequency shift keying AFSK which is used widely in the cube sat communication systems.
So, the band widths allocated for the transmission in cube sats are sufficient and can satisfy the requirements.
Best wishes
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I'm trying to understand the different modulation techniques for the satellite communication
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Dear Mardi,
The different digital modulation techniques including the binary phase shift keying can be implemented using digital signal processors. The digital signal processor calcualtes the the required wave forms. In case of BPSK there are two possible implementations:
a base band implementation where logic one is represented by + V and the logic zero is represented by  -V , where V is any suitable scalar, and band pass representation where logic 1 is represented by V cos wct and the logic 0 is represented by - V cos wct.
Normally the base band implementation is the common method for DSP to save the computation and reduce the power consumption. If is necessary to implement BFSK in band pass form, it is advisable to select as low as possible carrier frequency wc.
For more information please refer to the link: https://cdn.intechopen.com/pdfs-wm/6846.pdf
Best wishes
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I followed method suggested by G. Ma(2003) to estimate GPS receiver bias and calculated VTEC by removing Receiver Bias (Standard Deviation Method), it performs best but I get few values with negative VTEC  at 30o elevation cut off.
Any suggestions relating to this will be helpful. Thanks.
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I suspect your problem may be due to an underlying weakness in the Ma (2003) method, the assumption that the observed TEC values can be mapped onto a screen at some fixed altitude.  This assumption works at mid-latitudes, but will break down as the equatorial ionosphere is approached.  The source of this problem is the plasmasphere (or protonosphere), which adds an increasingly important component to TEC as the ionospheric equatorial anomalies (located nominally at +/-18 deg dip latitude) are approached.  This will lead to errors in the bias estimated, which can lead to negative TEC values.
Ma (2003) suggests that this can be mitigated by first determining a receiver bias value by operating the receiver at a mid-latitude location, and then using this receiver bias as a fixed value after the receiver is relocated.  I do not expect this method to work all that well.  Studies have found that the bias at the receiver end of the link (which includes everything from the antenna through the cabling to the receiver) can be sensitive to what appear to be only slight changes in the setup (particularly in the cabling) and to the ambient temperature.
You might want to look into work done by Andrew Mazella on a method he calls SCORPION (I don't have a recent citation for this).  It is similar to Ma's method, but it tries to take into account problems due to plasmaspheric contributions to TEC.
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STK Analyzer tool is an awesome tool for designing an experiment. I tried to use it for selecting both the constellation and orbital parameters based on the elevation angle between the ground stations and all the satellites in a constellation. Using macros in Analyzer may be a way, but it needs more participation from specialists. Hence, any thoughts?
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use the matlab and stk. define your parameters in matalb then simulate in stk and save data in matlab
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what are the files should be changing in ns2
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Thankyou sir. It is very helpful to  understand ns2
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hi...
as you may know iranian govt (and some other countries) use territorial jammers to disturb satellite signals. i've seen a lot about jamming cancellation using beam forming methods but my question is:
does any method exist that can be applied to this special problem? considering that any recommended method should perform signal processing after LNB ,
my initial guess is to use an array antenna and a FPGA board to process data between LNB and receiver and use a beamforming method but i dont know much about the output of LNB and jamming effects on that i will appreciate any help on this issue too
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Phase estimation (or signal runtime estimation) can be done by finding corresponding "points" (eg. peaks, spikes etc. of the jamming) in both input signals. If the jammer is stationary, this is a one-time job.
I see more difficulty in adjusting differing gains, especially if the LNBs implement AGC. (Otherwise this might be a one-time job as well.)
Good luck with that.
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I'm working on passive radars, I have a reference channel and a surveillance channel! I want to simulate the signal received on the surveillance antenna composed with reflexiosn from clutter interfering targets , target of interest and noise.Having just the SNRis , the time delays and doppler shifts and the reference channel, how can I do that since I haven't the amplitudes.
thanks in advance
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Also, see A. Zaimbashi, Forward M-ary Hypothesis Testing Based Detection Approach for Passive Radar
IEEE Trans. on Signal Processing, 65, 10, 2659-2671, 2017
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In WBAN, pulses are transmitted from an antenna , diffract around the body and can reflect off of arms and shoulders. so there are always two clusters of multi path components due to the initial wave diffracting around the body, and a reflection off of the ground.
I need to work with ZigBee (Narrow band data rate), Can I ignore the effect of reflection components in describing narrowband channel in small scale Statistics?
And take only the effect of diffraction?
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Thanks prof. Abdelhalim
Could you please suggest a simple reference to read more about your answer ?
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A case study of 3 to 6 weather stations would be considered for this research work
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You may want to look at the pressure and relative humidity in addition or as a proxy for temperature.
section 2:
The temperature, especially close to  phase transition regions (melting/freezing) will affect the humidity which will affect the attenuation.
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Is there any relation between the interference of mobile signals and the bluetooth signal strength.
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I have seen it the other way around, LTE bands 13 and 14 I believe (787 MHz) interfering strongly the GPS reception at 1575.42 MHz.
The 2nd harmonic of 787 MHz lies in the GPS frequency band. Even when the 2nd harmonic was weak, the GPS LNA would produce the 2nd harmonic when receiving the strong 787 MHz carrier. A good notch filter at the LNA's RF-input was necessary.
GPS signals are very weak and are easy to get interfered.
GPS interference on mobile signals is not present as far as I know.
regards, Bart
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Terminal equipment should be capable of video/voice/data communications, preferably if it can act as GIS terminal too.
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Nowadays, SatCom On-The-Move (SOTM) is coming into operation. Applications for SatCom On-The-Move (SOTM) are intended to provide mobile users with communication services especially at places without any terrestrial communication infrastructure, or at disaster scenarios.
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Modelling and simulation of nonstationary land mobile satellite channels by using extended suzuki and handover processes.
(city 25.mat and sub 15.mat)
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Based on measurements of the land mobile satellite LMS channel, an image-based channel model was developed in our departement and used in practical applications.
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Hello, i am trying to generate zenith angle of elevation and departure for SCM based wireless channel simulator. My end goal is to get the channel coefficients with respect to azimuth and elevation, so that i can apply beam-forming algorithms at Tx to enhance and analyse the overall system performance specifically vertical and horizontal beam-forming
PS: My Tx is a planar antenna with 100 dipole antenna's in a square grid. I already wrote my matlab code using the 3GPP technical report -(study on 3D channel Model for LTE) but i just want to be sure that i am going in the right direction. Your kind help would be highly appreciated:)
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Dear  professor Mohamed-Mourad Lafifi and  Professor Abdullah Bin shams,
Thanks a zillion for your kind help:)
Br//
Amit
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SMD GPS antenna, small GND plane
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Thank you Faisal, I will have a look at GGBLA.01.A.
Happy New Year.
Svetlan
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In VTEC maps that have been created from GNSS differential phase measurements of the TEC, the ionospheric pierce point is often shown. TEC that is measured over 20 200 km is mapped to somewhere between 400-600 km.
In GNSS computerized Ionospheric tomography (CIT), the electron density maps are only shown to an upper altitude of 600-1000 km.
Above what altitude is the contribution to the TEC considered negligible? Stankov et al. 2003 state, "The electron density above approximately 2000 km contributes little (less than 5%) to the integrated electron content and above the mean height of the plasmapause (25,000 km) the contribution is negligible." I seem to recall reading the contribution above 1000 km "is negligible" in another paper. What is the consensus?
Please provide a reference for a characteristic altitude.
For completeness, I believe the lower limit of the TEC integral is at about 60 km, assuming the tropospheric contribution is also negligible. Please correct me if I'm wrong.
Cheers,
Alex
Stankov et al., 2003,  A new method for reconstruction of the vertical electron density distribution in the upper ionosphere and plasmasphere, available from: http://onlinelibrary.wiley.com/doi/10.1029/2002JA009570/full
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It depends on your location; although, 1000km is too low a boundary even in the best cases. At high latitudes, where there is virtually no plasmasphere, the contribution above 1500-2000km or so is generally negligible; however, at the equator one would have to consider electron density out to the plasmapause region. This will also depend on time of day, season, geomagnetic activity, and solar activity. For your own reference, try creating a few electron density profiles with the Gallagher Plasmaspheric Model (an extension of the IRI). See the following for some codes: https://plasmasphere.nasa.gov/models/ These models can at least give you a rough feel to assess the significance of plasmaspheric TEC in the context of what you're interested in researching and provide a starting point.
There has been a considerable amount of work done by Andrew Mazzella and his colleagues on assessing the plasmaspheric contribution and effects on GPS observations. I would consult his work as well.
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hi all 
i hope someone can help me on the design of the vsat network for the calculation of the number of the vsat in the star Architecture
many thanks
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To add to the previous answer, you could for example browse through the Capacity Building Seminars organized by ITSO,
see for example:
and
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We would like to put collar on foxes in the Arctic. T°c can reach -40°c. We have a very small budget, so Telemetry solution etc... are far beyond what we can spend.
So we need a GPS logger that can resist to those extreme T°c and a drop-off system, and obviously a VHF unit to be able to find the collar again. Foxes are not easily trappable many times. The best, I think would be to have a WiFi tool on the GPS unit that could send the data on an external logger that we could set up on the dens for example, so that most data are safe. Has anyone does that before, or has a suggestion?
Thanks for your help!
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Hi Chloe
i agree that probably the most sensible component is the battery. most devices use lithium batteries, and they tend to fail in in low temp. But, i think that the issue might be less problematic than you expect fro two reasons: micro-climate and fox behavior. when you attach the collar to the fox neck, it is partially heated from the body of the animal and protected from wind by its fur. this may buffer some of the lower temp. second, since foxes themselves benefit from saving energy on thermo regulation by avoiding exterem condition, your devices might experience less of these freezing conditions.
Finally, even if the tag will eventually fail (due to temps or any other reason), remote download will minimize data losses. Since a short tracking effort will allow you to detect den location(s) for your tracked individuals, using a unit that has remote download will ensure that at least most of the data is secured. Wifi options are usually very energy consuming, and i would recommend a UHF or VHF downloading to a base-station placed in these frequently visited sites.  we had good experience with Eobs telemetry, Germany (see also some other answers i wrote here in RG). i think they are much cheaper that Telemetry solutions, but i havent checked lately. Other options are also worth exploring (e.g. Technosmart Itally have BT remote download that might work for your system, and they are also fairly cheap).
cheers
Orr 
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Frequently i facing interference in c,ext-c band satellite communication network.
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RF interference for C-band in above link is good. 
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Dear All
As we know any flying object like LEO Satellite or UAV its elevation angle of antenna of a ground(Earth) receiver starts from some value reaches a peak (maximum value) when flying object is just above your head then it starts decreasing and decreasing after some time it reaches below the earth surface and or elevation reaches zero .
Now we take an example of a signal tracking  of low earth orbit satellite satellite. suppose we have a signal receiver at ground and trying to receive the satellite signal. as the elevation angle increases the received signal strength increases, this strength keep increasing as the elevation angle keep increasing . the strength of signal reaches maximum value when the satellite is just above our head after that satellite elevation decreases so the receive signal strength reaches a minimum value at minimum elevation.
the requirement is mathematical formula which provide relation between receive signal strength and elevation angle.
I found paper attached which derived probability density function of elevation angle .how can I use this pdf function in order to get the receive signal strength(or SNR) from this pdf formula. do we need another formula or some changes is required to this formula.
I shall be very grateful for help.
Regards
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Hello Shakeel,
The K in my equation is for Kelvin. I was trying to indicate that TA the result of the calculation is a temperature in Kelvin. I'm afraid this text box does not work well for equations.
For a reference I recommend
Satellite communications systems / Gerard Maral, Michel Bousquet
This equation for Noise Figure will allow you to derive the relationship between the elevation angle (α) in my first equation to S/N. Again, this text box does not work well for equations. However, you should be able to find this equation in any EM or antenna text.
F= (Si/Ni)/(So/No) = No/(GNi) = No/(GkTAB) = 〖GkTA B + N)+R]/(GkTA B)
• Ni = kTOB is the available noise power at the input
• F       is the Noise Figure of the receiver
• Si        is the available signal power at the input
• So     is the available signal power at the output
• TA       is the temperature of the antenna in Kelvin
• NO      is the available noise power at the output
• NR      is the noise added by the receiver
• G       is the available gain of the receiver
• B       is the effective noise bandwidth of the receiver
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For example:
Given a specific bandwidth, is there anyway I can relate it to how much data transfer rate can be achieved? Or the other way around (given a specific data transfer rate, how much satellite bandwidth will it need)? 
I know this is in dependence of the modulation/codification (MODCOD) used, as well as the service, but is there any mathematical relation? I'm guessing it involves C/No, Eb/No, etc.
Would appreciate specific text recommendation.
Best Regards
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In general, the required occupied bandwidth for digital modulation, including FEC coding, is
B = k ( Rb / m )(1 / r )
where Rb is the bit rate, m is the number
of bits per symbol, r is the code rate, and
k is the bandwidth expansion factor used
to minimize intersymbol interference.
For example, if Rb = 64 kbps, m = 2 for
QPSK modulation, r = 1/2, and k = 1.2,
then B = 76.8 kHz.
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Most of the GSO(Geo synchronous orbit) satellites operate in L band  and/or  S band. What makes the bands convenient for satellite communication?
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All GPS signals are in the L-band of the frequency spectrum ( 1–2 GHz). Because L-band waves penetrate clouds, fog, rain, storms, and vegetation, GPS units can receive accurate data in all weather conditions, day or night. There are circumstances in which GPS units may not receive signals accurately, such as inside concrete buildings or under heavy forest canopies.
The choice of the GPS carrier frequency (to transport data signals) was submitted to the following requirements:
• Frequencies should be below 2 GHz, as frequencies above 2 GHz would require beam antennae for the signal reception.
• Ionospheric delays are enormous for frequency rages below 1,000 MHz and above 10 GHz.
• The PRN codes (explained in the Glossary) require a high bandwidth for code modulation on the carrier frequency. Therefore, a range of high frequencies with the possibility of a high bandwidth had to be chosen.
• The chosen frequency should be in a range where the signal propagation is not influenced by weather phenomena like rain, snow, or clouds.
Based on these considerations, the choice of L-band frequencies proved to be advantageous. Each GPS satellite (Block IIF and beyond) transmits three carrier signals in the microwave range of the electromagnetic spectrum, designated as L1, L2, and L5 (frequencies located in the L-band between 1,000 and 2,000 MHz of the spectrum). The L1 frequency is 1,575.42 MHz (wavelength 19.05 cm), the L2 frequency is 1,227.60 MHz (wavelength 24.45 cm), and the L5 frequency is 1,176.45 MHz (wavelength 25.48 cm).
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What is the scientific facts behind that?
Also that how to represent CDMA, 3G, 4G and 5G.
How to represent Satellite radio communication?
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Hexagonal cell shape is perfect in cellular architecture because it cover an entire area without overlapping.
Satellite radios are most commonly used by consumers in automobiles as it offers better sound quality and more station programming choices over traditional AM and FM radio.Consumers typically pay for Satellite radio programming on a monthly subscription basis.
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I am developing a plugin using PyQGIS, the raster data sets in use are quite big in size hence making the interface to appear as "not responding" despite the execution being done in the background. I have gone through a number of sources but I can't get to understand how to properly implement multi-threading to update a progress bar in my plugin. Which sources should I use for a better understanding of the implementation? Ideas will be appreciated.
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Is it possible for a hacker to send signals so similar to those of a GPS satellite but carrying wrong information, so that a GPS receiver thinks he is in another place?
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Dear Fabrice,
Indeed, that it is called spoofing: civilian GPS signals are known to be susceptible to spoofing attacks which make GPS receivers in range believe that they reside
at locations different than their real physical locations. Please find below a list of papers and links that may come useful for understanding it:
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SSPA is linear and TWTA is more efficient. How are linearity and efficiency of high power amplifier related? Where should I concentrate more; on linearity or efficiency? 
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Hi Nishil,
For a short introduction you can visit
The most useful comment above is the shortest, your choice shall be based on your mission requirements. Both SSPA and TWTA have dramatically improved in the last decade. Better efficiency for SSPA, allowing to reach higher power levels 5GaN technology) and flexible TWTA (check Thales Electronic Devices website, output power can be adjusted in a 0 to 4 dB range while keeping almost a constant efficiency for such devices, allowing flexible output power per transponder) or mini-TWTA for example. In most traditional C-band COMSAT applications TWTA would be the only choice due to output power requirement (derived from needed EIRP). But as said it depends on the mission requirements, type of modulation used (=> linearity requirement). Do not forget that eventually solutions shall be compared taking into account system parameters, e.g. TWTA efficiency shall be considered at operating point, it will not be the same if your mission requirements impose an operation at 3 to 10 dB back-off or allow to operate the TWTA at saturation (which is usually the operating point point used for stating the efficiency by the TWT manufacturer). Then for TWTA you will have the option of conduction or radiation cooled devices... 
To make your choice, you will need to perform at least a short system analysis.
P. Pierrot
I do hope it will help 
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I got the output for combinational TEC,but when coming to kalman filter, I am getting confused about which terms to be used in the equation,
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Surely, it is widely knows that TCP/IP satellite networks have a very high latency, specially for GEO links. However, which factors would be the most influent on the jitter for TCP/IP over satellite links ?
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You might want to take a look at these:
I don't know that jitter itself would be a big factor, but for sure latency is, at least for efficient use of TCP/IP. UDP, depending exactly how it is used, might not be impacted negatively. When using geosynchronous satellites, anyway, certain accommodations need to be made for the much longer RTT experienced, compared with terrestrial systems.
Another possible problem is your uplink speed. It might be very different from the downlink speed, which also impacts on TCP efficiency.
But I don't think jitter would necessarily be a problem particular to satellite.
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Generally, for satellite communication circular polarization is required. But, my doubt is can't we use linear polarization for satellite communication (within the satellite).
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It can be linearly polarized, however, it is preferable to have circular polarization because:
"An electromagnetic wave transmitted from a satellite-communication antenna to an earth station antenna has a specific feature -- polarization which is an electric-field vector orientation relative to the Earth.Thus, a satellite signal is also distinguished by the type of signal polarization in addition to the frequency range. When a linear polarization takes place, an electric-field vector oscillates in the vertical or horizontal plane. Accordingly, there is a vertical (V) and horizontal (H) linear polarization.The horizontal polarization signal is transmitted to a satellite-communication antenna in a horizontal plane, and the vertical polarization signal is transmitted vertically. The polarization of a signal transmitted from the satellite is strictly parallel or completely perpendicular to the Earth surface only at the longitude of the satellite.If the reception is directed to the East or to the West, the plane of polarization has an inclination relative to the Earth due to its surface curvature. The more distance between the altitude of the receiving point and the altitude of the satellite is the bigger is the inclination.Therefore, the antenna polarizer has a bigger or a smaller inclination relative to the Earth. If an electric-field vector constantly changes its orientation and the angle of rotation, such polarization is called a rotatable or circular polarization. Thereby a circular polarization is characterized by high speed of clockwise and reverse rotation of a signal.Fields of clockwise and reverse rotation are distinguished depending on the direction of the vector rotation."
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For mobile satellite communication system, Such as Iridium system in which every satellite could establish four links with its neighbor, can it be regarded as a DTN? And, if we could design the satellite constellation in term of DTN, could it reduce the cost of satellite networking and make the satellite Internet be popular?
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Please note that in the following answer I just consider store-and-forward, I don't seek to provide a full answer related to DTN as a whole. However, I think it can complement the existing answers: on the practical side, it is worth mentioning that the idea to implement store-and-forward schemes for satellite constellations is not unprecedented. For instance, the Orbcomm LEO constellation (~30 LEO satellites orbiting at 775 km altitude) tried this approach a "long time" ago (during the 90's). At this time, there was no intention to use inter-satellite links, but there already was a concept of non-real time system architecture, with ground stations as relays. So to start with, I suggest you investigate the details / architecture / performance / issues / challenges of this constellation (to my best knowledge it suffered during the early 2000s just like competitors (e.g. Iridium, to name one) but it could survive and is still in operation. Maybe you could start here
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Delay and Disruption Tolerant Networking could be an alternative solution for space network, I do research on space network, mainly about routing protocol. I want to consider the QoS and congestion in the space network.  Could anyone recommend some related works?
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Maybe these publications can help you: "Multipath TCP over LEO satellite networks" ( http://web.cs.ucla.edu/~youlu/IWCMC_2015_MPTCP-Satellite.pdf )
and the book "Routing and Quality-of-Service in Broadband LEO Satellite Networks"
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I want to get simulated result for geostationary satellite.
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Hi, Have you got a satellite simulation software ?
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Both IETF RFC2488 (Enhancing TCP Over Satellite Channels) and RFC3135 (Performance Enhancing Proxies Intended to Mitigate Link-Related
Degradations) provides some reccomendation/advice on usage of TCP over long latency links (e.g. Satelltes bridges), however, as of 2015, which are the most commonly adopted techniques in commercially available equipment ?
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That question is, I think, more for Gilat than for this research forum. However, based on what I know, TCP acceleration features include local acknowledgements and ack spoofing, NACK and header compressions, persistent sessions and also HTTP web pre-fetch acceleration and compression. Of course, as you can understand, many of the specifics of what the product is capable of doing are proprietary to Gilat. You should also try one of the forums in LinkedIn, where professionals from Gilat or other companies using Gilat products could give you direct product feedback.
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Using an all band(HF/VHF/UHF) Radio such as IC-9100 which is capable of doing FM modulation and demodulation, can I transmit and receive FSK data?
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Dear Bhagath,
Yes you can use analog fm transceivers to implement the FSK digital binary modulation and demodulation since simply the digital FSK is a special case of the analog fm where the modulating signal will be in a binary form having only two possible amplitudes say +V and  - V.One gets two fm symbols; one for the mark with frequency fmark, and the other for the space with frequency fspace..
But you have to take care of the achievable parameters of the FSK. The fm broadcast system has a bandwidth B= 200 KHz. This bandwidth is related to the input bit rate fb and the frequency deviation df by the Carsons rule, B= 2( df +fb/2)
For efficient bandwidth utilization it is required that df=fb/2 which means that the modulation index mf=1. Therefore, the highest  data rate will be 100 KHz with df= 100KHz too.
Since the FSK is a special case pf analog fm, the devices used for the fm can be used also for the FSK.
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Which would be the most commonly used Channel Equalization techniques for Satellite Links (regardless of the Medium Acess Schemes used, SCPC, DVB-S, DVB-RCS, etc .... ) which are publicly known/available ? Here i'm also considering both linear and non-linear techniques and algorithms.
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I think non-linear equalizers should also be kept in mind as they perform better than linear equalizers, in most cases.
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I need the angle of the solar sheet
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solar array proper control help to absorb the maximum power from the sun. in this way you are suggested to make arrays to track the sun in the best shape. the following references could help you: 1-KALWEIT, C. "Optimum yaw motion for satellites with a nadir-pointing payload." Journal of Guidance, Control, and Dynamics 6.1 (1983): 47-52.
 2-Hablani, Hari B. "Sun-tracking commands and reaction wheel sizing with configuration optimization." Journal of guidance, control, and dynamics 17.4 (1994): 805-814.
3-Long, Matthew R. Spacecraft attitude tracking control. Diss. Virginia Polytechnic Institute and State University, 1999.
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Any help would be highly appreciated
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The Weibull "model" is a probability distribution. The Weibull distribution characterizes for being continuous, and is applied in several scenarios; mostly, those requiring performance analysis.
Check:
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Can I please get some relevant paper on different algorithms used to estimate the power loss in dB caused due to the atmospheric losses such as ionospheric effects and troposphere effects while performing inter satellite links/communication/ranging (e.g.: MEO to MEO)?  I have the entry and exit points in the atmosphere along with satellite coordinates
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Communication between MEO and MEO:
Since these are positioned about 20,000 Km from earth, we do not expect any additional loss except free space loss. This can be computed using Frii's equation.
Communication between MEO and Earth surface:
This depends upon the frequency of operation.
  1. If it is Ku band operation, rain loss dominates over other losses. The rain loss can be calculated from ITU-R recommendations. ITU-R P.838-2, Specific attenuation model for rain for use in prediction methods. Available at  https://www.itu.int/dms_pubrec/itu-r/rec/p/R-REC-P.838-2-200304-S!!PDF-E.pdf
  2. For ionospheric losses, you can refer: Determination of the ionospheric transmission loss of the low frequency EM waves by simultaneous measurements of satellite and ground-based experiments by Hobara, Y and Parrot, M., IEEE General Assembly and Scientific Symposium, 2011 XXXth URSI. Available at  http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=6050768
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How would it be possible to map the different QoS and/or DifffServ/IntServ QoS types into the DVB-RCS Acess Scheme and Bandwidth allocation policies . I.e. : CRA, RBDC, VBDC and ?
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In a DVB-RCS based Satellite Network, the Satellite Interactive Terminals (SIT) requests for specific service types and the DVB-HUB allocates the SIT with slots depending on the service type. In the Return Link Subsystem (RLSS) of the DVB-RCS Hub, after the requests from the different SITs are demodulated and decoded (using Multi Carrier Burst Demodulators) the request in the form of IP packets is sent to the Bandwidth Manager or the system which does the Dynamic Bandwidth Management. This software depending on the service type allocates the slots to the terminals which is intimated to the Terminals using the Forward Link using Service Information Tables like the Terminal Burst Time Plan (TBTP) or  unicast/broadcast Terminal Information Message (TIM). The mapping needs to be done after suitable consideration in the Dynamic Bandwidth Management Software in the Hub. However, it depends on the implementation of the Hub Software and this is quite a general suggestion I have provided. 
For details |I am attaching two  papers which may be of some help to you. All the best for your Research.
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Is the effect significant? Is it useful or not? Is there really any effect in the received datarate? Are there effects in other forms of mobile communication?
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Doppler effect is due to mobile moving speed. The higher the speed, higher is the carrier frequency shift. This is serious if bandwidth is large. Therefore, high data rates and high speed of vehicle will not go together. 
At very high vehicle speed, modulation level drops and hence data rates. A trade-off is made between vehicle speed and data rate.
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I would like to calculate the propagation losses in dB (ionosphere, troposphere) when an inter satellite link is established between the MEO-MEO satellite. If there is any algorithm or model, i can use it for the implementation. 
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Hi,
here are some references
whether you cross the atmosphere and need to worry about ionosphere/troposphere losses is highly dependent on the configuration of your ISLs. If you restrict communication to the immediate neighbor in the same orbital plane or across an orbital plane (see iridium), you might never cross any layer of the atmosphere.
if that is your case then all you need to consider is the Friis transmission equation, antenna subsystem pointing losses, and device-related losses. but the radio path is relatively simple.
if you need to operate an ISL that is tangential to the surface of the earth (which also creates many other problems) then the next question is what is your frequency of operation. High frequency radio signals are more or less unaffected by the ionosphere, but affected by the troposphere. How you account for tropospheric losses is a more complicated matter since as pointed out the current models are developed for slant paths. You could perform an integration across the length of the path crossing the troposphere and account for the influence of atmospheric gases, clouds and rain on the path but that is highly dependent on the link configuration. You need to resort to physical models of rainfall fields i think
But for most practical situations, i think in practice you will not  have a link that requires you to account for those elements.
see for example
Maybe other colleagues in researchgate can comment
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Dear
Could anyone please let me know the procedure of making fine resolution DEM from CARTOSAT image. I would be happy even if you can help me to send relevant literature to prepare DEM. 
My objective is to check the impact of LU/LC change on runoff.
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1.First  add image
2. select RCP file
3.do interior & exterior orientation
4. Run Auto die point generation
5. do Triangulation
6. images are fit to image coordinates then give GCP and run again triangulation after giving GCP the images are come to ground coordinates.
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Which simulator software can best help to simulate mobility across hybrid terrestrial-satellite networks?
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Some of suggestion given by other researchers : 
Have a look at NANHAO ZHU's PhD These of 5 Jun 2014. "Simulation and optimization of energy consumption in wireless sensor networks"
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I'm wondering if there are any low cost SDR Satellite Channel Emulators.
I'm looking at emulating the Doppler Shift for VHF & UHF frequencies as seen by ground stations that don't dynamically tune. In this instance the ground stations have a fixed central frequency.
Has anybody tried using a HackRF to emulate Doppler Shift? Probably for something like GPS and or GNSS?
This:
versus:
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Thank you for your help. 
So far I'm attempting to emulate the Doppler shift associated with satellites in LEO so I can see how different receivers will interoperate. So far I haven't found anyone else working on this. I was hoping others had started experimenting with similar equipment in field of study.
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How can I use Python and GDAL to perform raster algebra? Is there a way that I can declare two or more satellite images lets say as A and B and thereafter use python and GDAL to perform raster algebra A*B = C?
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A simple Python raster calculator is actually shipped with GDAL - gdal_calc.py
Usage is pretty straightforward, you can declare input images to the letters A-Z, declare an output file as well as calculation. Your Example would look something like this:
gdal_calc.py -A imageA.tif -B imageB.tif --outfile=ABmultiplied.tif --calc="A*B"
In the current version of GDAL you can even employ numpy array functions on your input files (e.g. logical_and, logical_or, etc.)
If you find the GDAL handling from Python a bit cumbersome might I suggest taking a look at the rasterio module developed by the Mapbox team: https://github.com/mapbox/rasterio
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I am looking at laser communications between satellites and ground stations. I have been reading about nanocircuitary and plasmonic lasers. It does seem interesting but due to my limited background knowledge on microfabrication, I was wondering if other researchers in this field felt it was a possibility.
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A laser is a device with both optical gain and feedback. A certain amount of power needs to be supplied to this device before it starts to show the lasing behavior. This is known as the lasing threshold.
Current plasmonic lasers are relatively inefficient lasers because the metals used to make them have large optical loss. These need to be overcome. They also have relatively small output power compared to other lasers because the amount of material involved in the laser action is limited. For these reasons I believe that plasmonic lasers are a bad choice for laser communication systems.
My personal interest in these plasmonic lasers is to get a clearer picture on what comprises feedback (what is the feedback length of a plasmonic laser?) and to find an answer if losses in plasmonic circuits can be overcome. To realize loss-less plasmonics or metamaterials we need to think how to prevent lasing. Once a system lases, the extra power supplied to the laser tends to escape as laser radiation.
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Literature uses 1112 ESH for a year on GSO with north-south faced satellite. This can be found on:
"Degradation of thermal control materials under a simulated radiative space environment" by A.K. Sharma and N. Sridhara
"Evaluation of Thermal Control Coatings Degradation in Simulated Geo-Space Environment" by J. Marco and S. Remaury
and other publications. How does this value derives in detail? My approximations  show results around 886 ESH.
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Thank you very much!
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I am working on project related to wireless standard LTE and DVB-RCS. I have simulated individual blocks like modulator or  FEC in MATLAB but I have to simulate full system and for that I would like to know which software is proper to get correct results.
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For DVB-RCS simulation some patches which can be used with ns2 simulator is available but mainly used o simulate the Bandwidth on Demand techniques used in DVB-RCS.
Commercially there are Software & Hardware like DVB-RCS Forward and Return Link Analyzer used to work on DVB-RCS standard. There is also an Emulator commercially available named DVB-RCS Terminal Emulator which can emulate many DVB-RCS terminals and create a live DVB-RCS network environment.  These are very useful tools to work on DVB-RCS technology or to develop DVB-RCS Hubs. However, they are commercially available and quite costly.
For pure research DVB-RCS  patches in ns2 may help I feel.
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I am a research student and want to look a little more in the Satellite Comms Diversity Technique and would like to see the Satellite Communication Diversity Performance Tool works.
Thank you very much
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Hello,
you can find a sample implementation of the current model in recommendation p618-11 in the study group 3 website. Navigate to itu.int, radiocommunications, study groups, and follow the links to study group 3
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I want to know the acceptable model to estimate the attenuation due to rainfall in the northern Africa region.
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Hi,
I would suggest you start with the current ITU-R P 618 model for combined effects (including rain attenuation). Although there are several alternative models available, none have been exhaustively tested in the region you are interested in. 
regards
Luis
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in satelite uplink frequency is higher than downlink frequency
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Well, what you mean by uplink and downlink depends on the type of communication you are referring to. Here, I am going to discuss about two major domains- satellite communication (satcomm) and mobile communication (mobcomm).
satcomm: downlink- signal from earth base station to satellite
uplink- signal from satellite back to earth
mobcomm: downlink: signal from base station to mobile station (cellphone)
uplink: signal from mobile station(cellphone) to base station
Now, as would have thought, separate frequency bands are always allocated for uplink and downlink signals, often separated by a gap (maybe for future allocation, since the span of 'guard bands' are relatively very less compared to the actual information-carrying bands, e.g., 100 KHz guard bands in case of GSM-900, where the uplink and downlink bands span 25 MHz each).
The main question that this article will be answering is pretty simple: If you observe the uplink and downlink channels carefully, you would notice that the uplink frequencies are higher than the corresponding downlink frequencies in the case of satcomm, whether in the case of mobcomm, it's just the reverse.
satcomm: C-band : U/L-6 GHz, D/L-4 GHz
Ku band: U/L-14 GHz, D/L-12 GHz
mobcomm: GSM-900: U/L-890-915 MHz, D/L- 935-960 MHz
GSM-1800: U/L-1710-1785 MHz, D/L- 1805-1880 MHz
WHY IS THAT SO?
The answer is simple too. It's all about power considerations.
In satcomm, the signals have to cross the atmosphere which presents a great deal of attenuation. The higher the frequency, the more is the signal loss and more power is needed for reliable transmission.
So now you would say why use higher frequencies if signal loss is more and you need more power? It's because lower frequencies get reflected by atmospheric bands and cannot penetrate to get through to the satellite.
Now, a satellite is a light-weight device which cannot support high-power transmitters on it. So, it transmits at a lower frequency (higher the frequency, higher is the transmitter power to accommodate losses) as compared to the stationary earth station which can afford to use very high-power transmitters. This is compensated by using highly sensitive receiver circuits on the earth station which is in the line-of-sight (LOS) of the satellite.
In mobcomm, a similar point holds. A mobile is a portable device which cannot afford high-power transmission as it has a small battery with limited power. The 'free space path loss' comes to play. The higher the transmitting frequency, the higher is the loss. Since a mobile station (cellphone) cannot afford to transmit at high power to compensate for this loss, it must transmit on a lower frequency as a lower frequency presents lesser free space path loss. Therefore, mobile-to-base station (uplink) frequencies are lower than base station-to-mobile(downlink) frequencies.
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My aim is to design a LEO constellation to have regional cover.The number of satellite is 12 so my network has inter satellite link sometimes. But I do not know the typical frequency that ISL works at. And how to calculate the ISL budget. The other question is how can I simulate ISL and which software is useful? 
Thanks
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To begin, you'll also need to state how many planes, what the separation of those planes will be and how many satellites are in each plane.
Typically, purpose built communications between satellites is colloquially called "Crosslink". As this is outside the atmosphere your only limiting factors are: 1) Free Space Path Loss 2) Inter-spacecraft network knowledge; how aware does each satellite have to be about where it is in the constellation 3) pointing and directionality of your crosslink. 4) How much money you have to get all this done? 5) ITU available frequencies.
It can take up to 4 years to get the okay from ITU to use a given frequency. Not including the orbital slot. No, I have not filed ITU paperwork myself. The U of M is still building and iterating on its nanosatellite communications boards.
The software package you're looking for is called the Systems Tool Kit (STK) from Analytical Graphics Inc. (AGI)
With it you can model the orbits, the figure of merit for coverage over an area and the link budget. Optimising the orbits using the Walker tool is a non-trival process. They do have a tools called Analyzer and Optimizer that streamline the process. But they aren't free. You'll need some fun justification to your department for those costs. 
You can apply to get and educational licence here:
They also have excellent training guides:
The alternative software solution for you is called FreeFlyer from a.i. solutions.
So far I haven't had any experience with FreeFlyer. I'd love to give it a try to see how and why it differs from STK.
Be aware that currently, satellite systems technology is often under ITARS restriction from the U.S. and as such your institution may not have access to all of the available features.
Here's a random ITU link for the Space Services Department
You've got a great deal of study ahead of you. The learning curve is steep. 
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I am investigating the performance of OPLL in optical inter satellite communication systems.
I have made numerous simulations and in all of them, the performance was found to better for a higher bandwidth. My hypothesis is that at some point the performance should worsen for very high bandwidths as well because of the shot noise(AWGN). Is it correct? Can anyone throw some more light on this?
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I am impressed from the kind words of my colleagues Abedallah and Barrie.
For your question, there is an answer based on the communication theory.
According to Shanon:
C= W log2 (1 + S/N),
where w the bandwidth, S is the signal power and N the noise power.In case of thermal noise N=N0*W, with N0 the thermal noise density.Substituting N in the above equation we get,
C= W log2 (1 + S/No*W),
It is clear from this equation that still C increases with W keeping the power constant. Which means that the speed of the communication link increases by increasing its bandwidth even if S kept constant and the thermal noise increased proportional to the bandwidth.
This thanks to the nature of the information bearing symbols and the the noise. The symbols are a priory known where the noise is random in nature. So, the symbols can be  detected from noise by using correlators or matched filters.
Thank you Sharma for exciting such subject.
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Positions of a GPS user and GPS satellite were calculated from Kai Borre MATLAB programmes.
I want validate my results. Do you know of any interactive tools that give the results of user and satellite?
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Following software may b useful in this regard 
GAPS : The University of New Brunswick (UNB) developed the GPS Analysis and Positioning Software (GAPS).
GIPSY-OASIS, or GIPSY: the GNSS-Inferred Positioning System and Orbit Analysis Simulation Software package, developed by the Jet Propulsion Laboratory (JPL), and maintained by the Orbiter and Radio Metric Systems (ORMS) group.
Bernese Software: GPS/GLONASS post processing package developed by Astronomical and the Physical Institutes of the University of Bern, Switzerland.
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The cause of air disasters may range from bad weather to technical glitches. The worst part is when nothing is known about the location of crash sites like that of the MH370. The knowledge of what happened or where a disaster occurred may at least loosen the mystery surrounding them. This would not only answer those grieving relatives of the lost ones who have lost all hope in knowing what happened to the fate of their loved ones but also help in analyzing and resolving future air disasters. It is challenging to imagine that in this age of space exploration where humans have been able to cross interstellar space, we have still not been able to accurately monitor the space around our own home planet. Although reconnaissance missions may have clandestinely been able to monitor regions of the earth with sub-centimeter level resolution, it would be worthwhile to put them into humane operations with better temporal resolutions. Related research articles would be appreciated.
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The case of MH370 is too new to aviation and caught everyone by surprise (the 9/11 lessons of transponders being turned off voluntarily seemed to have been forgotten). Although it is too early to say what happened and why, the probability is that MH370 transponder was also turned off voluntarily. A solution, which could also bypass the need for remote sensors in the immediate future, is to make transponders inaccessible to any voluntary interference.
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I am currently doing a project in the area of optical inter-satellite communication (GEO-LEO).
I am using a optical carrier of 281 THz, and the Doppler shift corresponding to it is +/-7 GHz. I have introduced this Doppler shift in the transmitted signal S as an offset like
* e j2πfdoppler
At the receiver, I am using Costas Loop as a demodulator. I have to do Doppler shift compensation while recovering the signal. Guess, I have to add an offset compensator in the local oscillator.
Anybody has an idea doing this?
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Dear Abdelhalim,
Many Many Thanks for your answer. 
Your answer has helped me in many ways
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For some small countries which want to have their own satellite will it be possible to include the transponder and imager in the payload of the satellite?
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Quite an old example, probably many more:
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Respected Researchers, I need to know the difference between path loss of mobile-satellite links and mobile to mobile -mobile links.
1.If i write received signal as r given by r=h*((d)^-alpha)x+n will it be correct to write such equation for satellite to fix mobile station links.where h denotes shadowed rice distribution, x is signal , and d^ -alpha denotes distance based path loss effect. as you know the distance between(slant range) LEO satellite is variable. can i take d equation for elevation angle as variable.
2. similarly for mobile to mobile channel i have r=h1*((d)^-alpha1)x+n here h1 represents nakagami-m or rayleigh channel and d denotes distance based path loss. please guide and advise whether both equations are correct to write because in most papers i have not seen any d^ path loss exponent factor.
3. if I write most people write r=sqrt(E) h1*x+n. How to relate E to distance because in my case for LEO slant range is changing. 
4. Lastly How to combine path loss distance dependent factor in one network i.e in hybrid satellite-terestrial network. i.e in satellite-mobile-mobile
i.e r=h1*((d_satellite)^-alpha1)x1+h1*((d_mobile)^-alpha2)x2+n will this equation is correct. we have very large distance between satellite-mobile(d_satellite) path as compared with mobile-mobile(d_mobile) .
Any help How relate these distance with power of signal or SNR .
Most regards
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