Fourier Transform based DS/FH Spread Spectrum Receiver

An approach towards an efficient implementation of a spread spectrum receiver for wireless noncellular home-systems is presented. Whereas conventional receivers apply some filtering after despreading to recover the transmitted data, here a Discrete Fourier transform is applied and its output is redirected to an application specific processor (ASP). As mathematical operations (Fourier transforms) play a key role in both the data detection and synchronization scheme, this concept lends itself to be implemented as an embedded system. For this purpose the ASP is equipped with some additional functional units. The application in mind is a home system. To make the system more flexible and easier to implement a non-cellular approach was selected. A draw-back of this concept is that Power-Control (controlling the transmitted power), playing a key role in combating the Near-Far effect, is no longer possible. The hybrid direct-sequence fast-frequency-hop spreading technique was therefore chosen. To reduce the effect of channel distortion a Multiple Frequency Shift Keying (MFSK) modulation scheme is applied. The in-house developed sea-of-gates design system OCEAN is being used for prototyping.