On Dec 5, 6:10 am, Bob Bob wrote:
So at 5AM I may not be too sharp...

The formula you used doesnt seem to allow for the required demod s/n.
QAM64 for example (from memory) is around 30dB so this has to be "added"
to the path loss. Differing mod/demod/FEC have differing margin
requirmeents. Somewhere in there too you have to stipulate the bit loss
rate "allowed".

Can you explain this further please?

In the past I use to calculate the noise floor at b/w, apply RX noise
figure and then add the margin.

When I last did this I upset my employer by saying that their marketing
hype was flawed. They had specified a lowest usable sensitivity that
after applying the required demod s/n was below the calculated noise
floor for that b/w. We were in fact consistently getting RX sensitivty
issues during the manufacturing phase for this reason... Marketing had
created a spec that wasnt possible!

Interesting. So these margin requirements are specified in the
standard?

Also, I dont know about 802.15 but I do know that 802.11 has variable
data rates (ie bandwidth) that can be advertised something like "54Mbps
and -87dBm sensitivity". The numbers dont actually go together. At
54Mbps you might get -77dBm and you have to use 11Mbps to get -87dBm!

Thank you. I'll look into this!

I'll admit I havent studied your maths in detail....

The above probably not a lot of use to you... Sorry!

Cheers Bob VK2YQA

Thanks a bunch. A reply to my above queries would be very helpful.