Subject: [NEXTEL-1] Re: any noise floor, noise figure, C/N and such presentation available?

From: [email-masked]
Date: Tue, 11 Nov 2003 21:11:06 -0500

-------- Original Message --------
From: "gwweimer3" <[email-masked]>
Subject: Re: any noise floor, noise figure, C/N and such presentation available?

Eric:
Performance of any receiver is a function of the required C/N. It 
does not matter where the noise (N) comes from, internal to the 
receiver (or receive system) or external to the receiver (entering 
the antenna). If you read TIA/EIA TSB-88, it defines the required C/N 
based upon the Channel Performance Criteria (CPC). That criteria is 
stated in terms of Delivered Audio Quality or DAQ (as defined in TSB-
88)for analog systems and Bit Error Rate (BER) for digital receivers. 
In does not matter what "minimum" signal level a receiver can 
receive, a receiver can respond to a level of 1dB above the total 
noise, but you probably would not want to use it at that level (you 
could not hear anything).

For example, analog commercial grade service (DAQ 3) can be obtained 
with 17 dB C/N if you consider N to be the sum total noise in the 
receive system. Remember, that nominal signal level will provide 50% 
probability of successful communications. That number is valid for a 
25kHz bandwidth receiver with +/- 5 kHz deviation.

Therefore, there is no need to have a receiver with a reference 
sensitivity of -120 dBm if your total noise is -85 dBm. If the total 
noise is -85 dBm, you would need -68 dBm for 50 % reliability or -
54.8 dBm for 95% probability.

Also consider, internally-produced intermodulation (inside the 
receiver) must be added to the noise when determining the required 
signal level.

Hope this helps...
George

 "eric995us" 
<eric.h.lawson@a...> wrote:
> Does anyone out there know of a freely availble "White Paper" type 
of 
> document that gets into ambient noise floor and system noise 
figure,  
> and how that relates to "how weak of a signal can you hear" and "a 
> better receiver under the current conditions is a waste"? 
> 
> I was in a meeting and pointed out several flaws....I don't think I 
> need to say more....
> 
> Anyway, I'm trying to be efficient (lazy is too harsh of a word) 
and 
> not reinvent the wheel if someone has already gone through this. 
 
> Eric

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