Satellite Coordination Calculation & Software (http://www.satcom.co.uk/article.asp?article=19)

 Introduction The pages which follow are the slides of a lecture presented by Mark C J Posen of RPC Telecommunications Ltd. The slides were created using Microsoft PowerPoint and converted to HTML. During conversion the slides were combined into 7 sections. You can navigate between these sections at will from the left hand side. However, bear in mind that for the slides to make the most sense, it is suggested that you read through them in order. Please note that this presentation contains the lecturers notes, and so in some places are not complete. If you have any questions regarding these lectures please contact the author here.
 Coordination Tasks What do we need to be able to do for successful coordination? Link and interference analysis: Link budget / C/N analysis Interference analysis Margin analysis Proposing technical solutions Data gathering and processing: Collecting information about other networks Understanding regulatory issues Analysing transmission parameters to support technical analysis Software Tools Software tools can assist with all these tasks: Data searching, manipulation and analysis Pre-calculation dataset preparation Calculation and technical analysis Software is available from a number of sources, but the main "software" needed to do successful coordination is in your own brain!  So we will look at some manual analysis before we review software tools.
 Link & Interference Analysis Link budget refresher: Received Carrier Power: Pr = Pt + Gt  Lp + Gr (dBW) Received Noise Power: Pn = 10 log (k T B) (dBW) Carrier to Noise Ratio: C/N = Pt  Pn = Pt + Gt  Lp + Gr  10 log (T) - 10 log (B)  10 log (k) (dB) Carrier to Interference refresher: Received Wanted Carrier Power: Pw = Pt + Gt (θ)  Lp + Gr (φ) (dBW) Received Interfering Carrier Power Pi = Pt + Gt(θ)  Lp + Gr(φ) (dBW) So carrier to interference ratio: C/I = Pw  Pi = [Pt + Gt (θ)  Lp + Gr (φ)]  [Pt + Gt(θ)  Lp + Gr(φ)] Normally simplify by assuming that Lp = Lp. Note that the Gr terms both refer to the same antenna (the receiving system gain). Define receive antenna discrimination, Dr = Gr (φ) - Gr (φ), typically 3 or 4 dB for a satellite receive antenna, generally much higher, say +20 to +40 dB for an earth station receive antenna. So simplify terms: C/I = Pt + Gt (θ) + Dr  Pt  Gt(θ) (dB) This is a very simple equation; satellite to satellite coordination is not technically difficult to analyse! Some additional complications to bear in mind: Pt and Pt can be power spectral densities (dBW/Hz) or powers (dBW). If Pt and Pt are densities then strictly you have calculated Co/Io not C/I (Co/Io ~ C/I for digital carriers). If Pt and Pt are powers then they may have different bandwidths - normalise C/I inside the bandwidth of the wanted carrier.
 Protection Ratio Analysis Protection ratio is the minimum acceptable single entry C/I for a wanted carrier.  This is defined by ITU-R Recommendations. Recommendation ITU-R S.741 summarises the protection ratios for different wanted carrier types. Protection ratios are generally defined in terms of an "allowable" interference level as a proportion of the thermal noise in a link. Examples for different wanted carrier types: Digital carrier 6% of thermal noise PR = C/N + 12.2 dB FM/TV carrier 4% of thermal noise PR = C/N + 14 dB FDM/FM (multiplexed telephony) carrier 800 pW0p in 7500 pW0p noise budget, i.e. 10.67% of thermal noise PR = C/N + 9.7 dB
 Databases, Data Gathering & Processing Coordination analysis needs information on "wanted" and "interfering" satellite networks. Some regulatory information: ITU status of network ITU "findings" for specific assignments ITU "priority" (date of protection) for assignments Detailed technical information: Satellite beam parameters (gain, footprint, service area, noise temperature) Earth station parameters (gain, sidelobe, noise temperature) Transmission parameters (carrier type, modulation, max and min power and power density) The ITU maintains a comprehensive database of all networks (satellite and terrestrial) undergoing coordination and those that have completed coordination and are recorded as in use (Master International Frequency Register - MIFR).  This database should be the source of all regulatory and technical data used for coordination. Most software tools use this database.