Environmentally-shaped colored spreading sequences for robust wireless communications

Direct Sequence Spread Spectrum modulation is widely used in wireless commercial communication systems for code division multiple-access supporting multiple users simultaneously. The spreading sequences employed are often drawn from a finite set of spreading sequences that are orthogonal or exhibit good cross-correlation properties and therefore mitigate interference caused by simultaneous multiple users, i.e. multi-access interference. However multi-access interference is one of many interference regimes that must be addressed. Often, other external interference sources may have adverse effects on a multi-user wireless system. Traditional spreading codes combat external interference sources through processing gain, however when processing gain is not sufficient unacceptable performance results. The proliferation of software defined radios permit programmatically generated modulation schema and therefore motivate the use of spreading sequences that are environmentally-shaped and robust against additive colored interference sources. We demonstrate improvements in wireless communications performance when comparing environmentally-shaped colored spreading sequences against commonly used pseudo random noise spreading sequences.