Why are received spread-spectrum signals so resistant to interference?

The core strength of spread-spectrum technology is its immunity to interference. When the receiver applies the synchronized pseudo-random algorithm to "despread" the desired signal, it simultaneously takes any uncorrelated narrow-band interference and spreads it out across the entire bandwidth. Because the interfering signal does not possess the correct spreading code, its energy is diluted into the background noise floor. The desired signal is mathematically reconstructed, while the non-matching signals are inherently suppressed by the despreading process. Distractors suggesting the use of very high power or active frequency-change requests upon detecting interference are incorrect. Spread spectrum often relies on very low power density, and its interference resistance is built directly into the math of the algorithm.