An adaptive Bayesian receiver structure for use in asynchronous multi-user code division multiple access (CDMA) systems is presented. The structure consists of a bank of eigenfilters and a radial basis function (RBF) network. This receiver can be trained to form the Bayesian non-linear decision boundary. Simulations demonstrate that it outperforms conventional matched filter detectors. Bit-error-rate curves are presented which show that it is robust, near-far resistant and able to cope with multipath. Its performance is similar to that of optimal maximum likelihood detectors with the advantage that it is less complex and inherently adaptive

Direct-sequence spread-spectrum transmissions are increasingly employed in terrestrial radio-location systems to minimise interference with narrowband communications services in shared bands. Further flexibility in band planning is afforded by a scheme to generate from the high-rate sequence an integral number of lower-rate, narrow-bandwidth, `split-signal' sequences which are transmitted in available gaps in the spectrum. The paper shows that the bandwidth and power density of the transmission may be further controlled by overlapping or interleaving the spectra of the split signals without unacceptable degradation of positioning performance due to their mutual interference

The delay-lock-loop is a device used in direct-sequence spread-spectrum receivers to track the delay difference between two binary correlated waveforms. This short paper aims to clarify both the interpretation of the S-curve and the sign of the tracking error for such devices, especially those for navigation systems such as GPS.

The paper investigates methods to minimise interference between spread-spectrum (SS) radio-location systems and other radio services. Methods to control the power spectral density (PSD) of SS signals are reviewed. A novel technique, called `split-signal', is described which minimises mutual interference. The technique exploits the noncontinuous use of the radio spectrum by splitting the SS signals into several lower-rate, narrower-bandwidth components. These are transmitted independently in gaps in the radio spectrum and recombined at the receiver. It is shown, by analysis and simulation, that the performance of split-signal SS radio-location systems in comparable to that of conventional wideband SS systems

It is well known that multiple correlations of deterministic signals allow information about those signals to be extracted. The paper describes the application of triple correlation techniques to identify characteristics of several binary cyclic sequences commonly used in communications systems, especially those used in spread-spectrum systems. It is shown that the feedback function for a linear feedback shift register which generates an m-sequence can be found through the use of triple correlation. Examples of how to identify the feedback function when noise and data are present on the spread-spectrum signal are given

It is demonstrated that the detection of direct-sequence spread-spectrum signals by triple correlation is robust in the presence of multipath. The detection performance is illustrated by means of a typical receiver operating curve.

The feedback function of the linear feedback shift register, which generates the coded sequences employed in spread-spectrum systems for the spreading function, is detected by the use of triple correlation analysis. This allows the pseudonoise (PN) code to be determined for correct waveform demodulation

It is demonstrated that the period of an m-sequence and the feedback function of the linear feedback shift register which generates it can be determined by the use of a triple correlation analysis technique.