Patent ID: 6075781
Filing Date: 2000-06-13
Classification: H04B,Y02D

Abstract:
A spread spectrum CDMA communication system in which one or more receiver equipped base stations communicate with a multiplicity of receiver equipped subscriber terminals located in different beams of a multi-beam satellite relay system, the base station(s) transmits a signal for each beam which is comprised of a set of orthogonally spaced subcarriers, each of which is modulated by a set of orthogonal, or nearly orthogonal, functions which are overlaid with a pseudo-noise (PN) sequence forming a coded spreading sequence for an information signal, each orthogonal function of said set carriers data for a single user in said bean, a source of selected carrier signals and means to modulate said information signals onto said subcarriers to form a beam signal and said coded spreading sequence on said beam signal, and wherein the available frequency spectrum is divided into nonoverlapping or orthogonal frequency segments which are assigned to different beams in a 1:N.sub.ru frequency reuse pattern and each subscriber terminal has a receiver with means to coherently demodulate the base station signal, the improvement comprising:a circuit at said base station for applying a PN spreading code, P2, with chipping rate N.sub.ru .chi.R.sub.c to all of the beam signals simultaneously to spread the signal energy over a wider bandwidth in order to reduce the power spectral density in each beam, anda circuit in the receiver for correlating a received signal with a synchronized replica of P2 to remove P2 from the incoming signal without affecting beam-to-beam frequency isolation.