LINEARLY CONSTRAINED DIRECT-SEQUENCE SPREAD-SPECTRUM INTERFERENCE REJECTION

A constrained least-squares technique is presented that utilizes a mod ified optimality criterion which enhances the detection capabilities o f direct sequence spread spectrum systems. The standard least-squares rejection filter adds distortion to the decision variable at the outpu t of the despreading operation Constraints are introduced into the lea st-squares solution of the rejection filter which reduce the self-nois e of the filter while simultaneously retaining its interference reject ion properties. Two types of constraint conditions are considered. The first is a correlation matching property for the rejection filter out put. This constraint induces the filter to pass the chip sequence undi storted. The second type or constraint is energy reduction, which indu ces the filter to achieve minimal energy. Both constraint types are su ccessful at increasing the output signal-to-noise ratio (SNR). Simulat ion results are presented which demonstrate the output SNR improvement by using the constrained rejection filter.