L-3 Communications Corporation

Steven B Perkins

Thomas R Giallorenzi

L Andrew Gibson

Lee A Butterfield

Samuel Charles Kingston

Johnny M Harris

Dan M Griffin

DeLon K Jones

Lyman D Horne

Leon L Nieczyporowicz

Ronald B Arthur

R William Steagall

A method and system for open-loop acquisition of a pseudo-noise (PN) encoded QPSK burst signal is provided. The method includes the steps of determining a PN correlation accumulation (PNCA) threshold and a sync threshold. Searching for a burst signal synchronization by searching a burst preamble for a sync word exceeding the sync threshold. In response to detecting the sync word, performing a PNCA of at least 256 bits following the detected sync word and comparing the PNCA of the at least 256 bits with the PNCA threshold. The comparison further includes the step of verifying that the PNCA of the 256 bits following the detected sync word exceeds the PNCA threshold and then verifying sync word detection. Next, using the burst preamble an estimate of carrier signal frequency is determined; and using a subsequent burst preamble carrier signal frequency and carrier signal phase is determined.

Acquisition of a synchronous CDMA TDD QPSK waveform using variable thresholds for PN and burst synchronization

A method for improving the spectral properties of a PN codeset for use in channels of a synchronous CDMA telecommunications system. The method includes steps of (a) providing a PN codeset matrix; and (b) reordering the columns of the PN codeset matrix in accordance with a reordering code. The method may further include the step of inverting at least one codeword of the reordered PN codeset in accordance with an inversion pattern, and may further include the step of selecting PN codes to optimize a subset of channels to operate in an asynchronous manner.

PN code selection for synchronous CDMA

Disclosed is a method for generating I/Q waveforms for transmission over a CDMA radio channel. The method includes steps of (a) summing, for each of a plurality N of channels, the state of I bits to form an Isum value having a sign bit, the state of Q bits to form a Qsum value having a sign bit, and a total number of active channels to form a channel sum value; (b) applying the Isum value and sign bit, the Qsum value and sign bit, and the channel sum value to an input of a multiplexer; and (c) time multiplexing the inputs to generate first and second sets of output bits. The first set of output bits includes a subset of the Isum value bits, a subset of the Qsum value bits, the I sign bit, and the channel sum value bits. The second set of output bits includes the subset of the Isum value bits, the subset of the Qsum value bits, the Q sign bit, and the channel sum value bits. A next step of the method sequentially applies the first and second sets of output bits to a lookup table memory device for sequentially outputting an I value and a Q value for application to a digital to analog converter for generating I/Q waveforms that are predetermined to reduce transmission power and distortion. In the preferred embodiment of this invention the lookup table memory uses the LSB of the channel sum value as the LSB of the I value and the LSB of the Q value.

Fixed wireless loop system having baseband combiner predistortion

Users or subscribers of a multi-user communications system, such as a spread spectrum communications system, provide signals to the central station or base unit of that system, and receive signals therefrom. Avoidance of interference among those users' signals is needed to ensure proper operation of the system. To do so, the data of each user is individually scrambled to randomize the data that different users are transmitting, in order to improve tracking performance at a receiver. The data of each user is scrambled independently, in a manner unique to that user in the system, in order to improve tracking performance and detection performance of a receiver. This scrambling makes the multi-user interference zero mean, and makes it possible to integrate out or average out the multi-user interference. The pattern or sequence used for this scrambling, and the pattern or sequence used for spreading here, are preferably identical except in frequency.

Data scrambling system and method and communications system

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Sandy, UT, United States of America

Steven B Perkins