What is the advantage for Spread Spectrum?
1. Spread-spectrum is useful because it provides some robustness against multipath and discrete signal interference, such as exists from microwave ovens in the 2450 MHZ band. Both frequency hopping and direct-sequence systems operate over many frequencies. Multipath signal cancellation is highly dependant on propagation path geometry. A small frequency change alters this geometry, reducing or eliminating the cancellation. These spread-spectrum systems offer a frequency change that is faster than the bit rate. The result is there is some reduction in the severity of multipath cancellation. The de-spreading process in a direct sequence receiver actually spreads discrete frequency signals. This has the affect of lowering the intensity of discrete frequency interference. Most of the potential interference in the ISM bands is from low power transmitters. The exception to this is leakage from microwave ovens. A direct sequence spread-spectrum processor will reduce this interference by the sa
