Xref: utzoo rec.ham-radio:4154 sci.electronics:2408
Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!ames!umd5!uvaarpa!mcnc!decvax!decwrl!labrea!paulf@umunhum
From: paulf@umunhum.STANFORD.EDU (Paul Flaherty)
Newsgroups: rec.ham-radio,sci.electronics
Subject: Re: Spread Spectrum
Message-ID: <148@umunhum.STANFORD.EDU>
Date: 2 Mar 88 18:03:41 GMT
References: <1474@hyper.UUCP>
Reply-To: paulf@umunhum.Stanford.EDU (Paul Flaherty)
Organization: The Three Packeteers
Lines: 27
Keywords: detection-unlikely -- unless you try


I missed your reply to my first message, but it's clear that you don't have
a fundamental grasp of Shannon's Law;  Spread Spectrum raises the noise 
floor across the communication passband, and that increase in noise can
be detected.

The BASIC simuation that you've proposed is invalid for a number of reasons,
not limited to:

	1. The BASIC RND function is uniform; to model a radio channel,
	one needs Gaussian noise, plus impulse noise, plus Rayleigh fading
	on the signal.

	2. No statistical test is proposed to separate the spreading code
	and the noise; however, even in the case that you have given,
	it can be shown statistically that the resultant is not uniformly
	distributed, and therefore a signal exists on top of the noise.

Certainly, spread spectrum is less detectable than a narrowband signal, but
to claim that it is next to impossible to detect is foolish.




-=Paul Flaherty, N9FZX	    |
Computer Systems Laboratory |  "panic: getfs: bad magic"
Stanford University	    |
->paulf@shasta.Stanford.EDU |		--4.3bsd Unix