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I am bit confused between these two terms. I understand SINR is signal to interference+ noise ratio and SNR is signal to noise but isn't interference noise too? Then why have he segregated these two terms?

Further I also encountered signal dependent and signal independent interference. I couldn't find much about it except the research paper where people have worked on increasing SNR or SINR.

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  • \$\begingroup\$ just a guess: interference might by somehow correlated with the signal, while noise is not, i.e. noise is a completely random signal. \$\endgroup\$ – Curd Oct 9 '14 at 6:44
  • \$\begingroup\$ Can you provide a link to where you head this term defined? \$\endgroup\$ – Andy aka Oct 9 '14 at 7:16
  • \$\begingroup\$ I was looking into MIMO radar signal processing. A lot of stuff there goes into calculating SINR and then optimisation. They always take interference different from noise and interference is also signal dependent and independent \$\endgroup\$ – Aashish Sharma Oct 9 '14 at 8:02
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There is also another term used in ADC testing, SINAD - SIgnal to Noise And Distortion.

In the common, imprecise usage of the term; noise is any unwanted signal or deviation from the desired result.

With most Engineers who delve into the deeper details of signal performance, noise is characterized by a process that is fundamentally stochastic, i.e. it is random and is driven by PDF's (probability density functions). This is typical of several different noise sources like shot noise, flicker noise, RTS - random telegraph signalling etc. etc. the list is quite long. Where as Interference is an unwanted signal from within your circuit or from external sources and is characterized by magnetic/electric field coupling, poor power supply rejection ratio, ground bounce and a multitude of other things that are far more controllable and correctable. The third category is distortion; which arises from non-linear effects within your circuit itself.

In your RADAR example, you can see why they would care about distinguishing these differences. You are listening on an antennae which is receiving your own return signals and signals from aggressor sources which can confuse the processing. But they also care about the noise floor generated from the amplifiers and perhaps even the atmosphere and CMBR (Cosmic Microwave Background Radiation) which sets the sensitivity limit and operational range/performance. Signal dependant interference comes it play with distortion effects in amplifiers, backscatter and non-linear effects in the targets, amongst many other things.

TLDR; the author is being precise and is appropriately drawing a distinction between distinct terms. Common useage is very imprecise.

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