AboutLuis Emiliani Expertise Strengths
- Satellite link design and analysis
- Vsat network design and analysis
- Propagation aspects for terrestrial and satellite links
- ITU-R P recommendations
Can not help with:
- Questions related to TV receivers, TV kits, or specific networks such as DirecTV or DISH
- Antenna pattern synthesis, RF MoM analysis, S-parameters.
Experience My experience is in satellite communication networks and terrestrial microwave links.
Expert: Luis Emiliani Date: 6/8/2008 Subject: Link Analysis Calculation.
Question (1)How can we find satellite parameters ? For example NSS-6
(2)How can we find LINK parameters ?
(3) How can we find UPLINK analysis of C/N in clear sky & in rain ?
(4) How can we find DOWNLINK analysis of C/N in clear sky & in rain?
(5)What about total Link analysis ?
(6)How can we find Tx E/S Power Amplifier sizing ?what are the parameters come under ?
(7)How can we find Tx EIRP Calculation ?
(8)How can we find % Transponder utilisation ?
(9)How can we find Noise Bandwidth ?
(10)Sir, do you have any easiest table for calculating link analysis ?
(11) What are the technical details keep in mind while calculating Link Analysis ?
Answer Hi,
this is a very complex subject and question. we could spend hours going over every element and the background you need to have to understand each parameter and its implication in the process of link analysis.
i suggest you buy a good book such as Maral and Bousquet's for space communication design or Maral's for vsat networks.
on the web you can find useful primers, but i find that they do not cover all the detail you need to have sound understanding of the design.
this is a good primer:
download the SST tool. to use you need to know everything regarding your satellite, and by that i mean
Saturation flux density contours
EIRP contours
G/T contours
input backoff, output backoff or DELTA backoff, which relates one with the other.
bandwidth of the transponder to use, frequencies, type of transponder (most of them are linearized TWTAs).
these values you get directly from the operator or perhaps from a specialized database. something like the satellite encyclopedia gives you some parameters, but not all, the website of each operator gives the basic marketing contours for EIRP and G/T and a range for the Input, output backoffs and also for the saturation flux density.
beware of "simple tables". simple link calculations yield results that might not reflect the real situation once you activate the carrier. them ore information you leave out (such as propagation analysis, interference management, intermodulation) the less precise the result will be. the more thought and work you put into the input data, the better the results you will obtain.
total link quality is the inverse of the sum of the inverses of the C/N ratio of each element in the link: uplink, downlink C/thermal noise, the overall C/Intermod noise on the transponder and earth station, the C/Interference power corresponding to adjacent channel interference, co-channel interference and adjacent satellite interference.
the %transponder utilization is just how much of the transponder power and bandwidth you are using. it depends on the carrier's parameters (modulation, coding) and the equipment used (roll-off factor of the filters)
all rain analysis require knowledge of the local climatology. i suggest you download and use the current itu-r models for rain attenuation and rain intensity calculations. those are recommendations ITU-R P837-5 and ITU-R P618-8. those recommendations are normally implemented in the software used to perform the link calculations. i believe sst tool from loral has them built-in. however, you can also build your own software based on the text in the recommendations and the data available to download from the itu. you can download up to three recommendations free of charge per year, if you register in the itu e-bookstore.
i hope i have covered what you need to get started.
do not hesitate to post again if i can be of assistance.
