See the Hedy and George Story
Answer: Synchronous agreement on code books or code particulars!Examples:Military orders for the day.
The proposed "player piano" anti-jamming system of Hedy Lamarr and George Antheil
The main parameter of importance in the discussion of spread spectrum systems is the so-call processing gain-- the ratio of the transmission bandwidth to the information bandwidth -- viz.,
This parameter is also refered to as the spreading factorand it determines the number of users that can be allowed in a system, the amount of multi-path effect reduction, the difficulty to jam or detect a signal etc. For spread spectrum systems it is advantageous to have a processing gain as high as possible!
PN code is an abbreviation for Pseudo Random Noise Code
The Principles of Spread Spectrum Communication: a brief, but quite insightful tutorial by Jack Glas (original)
The CDMA Report from students at MTU
The ABCs of Spread Spectrum -- A Technology Introduction and Tutorial: an valuable tutorial and web link list (from the Spread Spectrum Scene) which includes:
Randy Katz' wonderful and downloadable introduction to wireless modulation: CS294-7: Digital Modulation
Phil Flikkema's concise and downloadable introduction: Overview of Modulation Techniques for Wireless.
Amateur Radio Spread Spectrum Communications Page
Spread Spectrum Data Communcation: a thesis by Darryl Smith at the University of Technology, Sidney.
Spread Spectrum Communication Papers - Tutorial Papers: a collection of set of tutorials by Francisco Rodrigues-Henriquez.
The Hedy Lemarr - George Antheil Story
The Birth Of Spread Spectrum from MicroTimes (original)
The famous story ofHedy Lamarr's "Secret Communications Technique" Patent. (original)