AboutMark C J Posen Expertise I am happy to answer questions of a technical and regulatory nature in the area of satellite and radio communications. I am best able to answer questions about systems and technology and less able to respond to questions about specific hardware and equipment setup and installation, but I'm happy to try and address any question put my way.
My main areas of expertise are link analysis (link budgets, performance, Eb/No, capacity), interference analysis (C/I, protection ratios, interference avoidance), spectrum management (frequency coordination, inter-system sharing), Radio Regulation (ITU, ITU-R) and satellite technologies and trends.
Experience I have worked as a satellite communications engineer at a professional level since 1983. Since 1990, as Managing Director of RPC Telecommunications Limited, I have operated a private satellite communications consultancy and have provided technical support to many satellite operators and national governments.
Organizations IET - Institution of Engineering and Technology, IEEE - Institute of Electrical and Electronic Engineers
Question Dear Sir, In our Uplink, we are changing FEC 3/4 to 5/6,I know advantage of FEC,but can you explain me what is disadvantage?Where get the problem?Why?
Sanat
Answer Hello,
When you change from rate 3/4 to rate 5/6 FEC you are reducing the amount of coding (i.e. before you have 1 coding bit for 3 data bits, now you have 1 coding bit for 5 data bits).
This means:
* The transmitted bit-rate reduces slightly, which has the advantage of reducing the bandwidth required to support the carrier, thereby potentially reducing the satellite bandwidth costs.
* BUT, because the coding rate is reduced then the code will be slightly less efficient at correcting errors, so you'll need to transmit a little more power in the carrier (i.e. achieve a slightly higher C/N) in order to achieve the same bit error rate (BER) on the assumption that all other conditions remain unchanged.
Basically what is happening here is a slight re-adjustment of the trade-off between the amount of satellite bandwidth and the amount of satellite bower that is needed to support this carrier.
I hope this helps. Please remember to rate this answer.
