The Boeing Company

Xinyu Wang

Robert Paul Higgins

Paul R Norris

Igor Elgorriaga

Marcus R Gahler

Yefim Samullovich Poberezhskiy

Michael S Foster

Brian J Hatley

Embodiments of the disclosure provide methods, apparatus, and articles allowing two nodes to communicate in a slot-based direct sequencing spreading communication system. Both a preamble sequence and a payload data spreading PN sequence are generated from the Time of Day and a given user code. Generated sequences are synchronized between two communicating nodes to allow slot-based DSSS communication to take place. Generated sequences also change dynamically from slot to slot to provide waveform security.

Method and device of generating time-varying preamble sequence and pseudorandom noise (PN) binary sequence in direct sequence spread spectrum (DSSS) communications

A device for fast transition from preamble synchronization of a received baseband signal to demodulation of the received baseband signal may include a baseband chip tracking loop to generate an offset tracking value to track any initial chip phase offset and Doppler-caused baseband chip frequency drift associated with the received baseband signal. The device may also include a numerical controlled oscillator to correct any Doppler-caused phase rotation associated with the received signal. The device may additionally include a preamble synchronization unit to detect a preamble of the received baseband signal, and to measure a chip phase offset and a baseband Doppler frequency shift associated with the received baseband signal. The chip phase offset may be used to set an initial chip phase offset value of the chip tracking loop so that the chip tracking loop starts with approximately a zero pull-in error. The baseband Doppler frequency shift may be used to set initial frequency offset values in the chip tracking loop and the numerical controlled oscillator so that both start with substantially near-zero offset errors for substantially immediate demodulation of the received signal. The device may further include an output device to output the data demodulated from the received baseband signal.

Device and method for fast transition from preamble synchronization to data demodulation in direct sequence spread spectrum (DSSS) communications

A system for synchronizing a spreading sequence transmitted during a plurality of time slots includes a plurality of communication stations. Each communication station includes: (a) a control unit; (b) a spreading sequence unit for originating the spreading sequence; (c) at least one of a transmitter and a receiver; (d) at least one delay unit responding to the control unit for imparting a first delay to the spreading sequence presented to the transmitter unit and responding to the receiver unit for imparting a second delay to the spreading sequence presented to the receiver unit; and (e) a synchronizing sequence generator coupled with the transmitter unit. The synchronizing sequence unit in a first station presents a synchronizing sequence for transmission accompanying spread information transmitted during selected time slots. A receiver unit in a second station employs the synchronizing sequence in cooperation with the spreading sequence for despreading received spread information.

System, apparatus and method for synchronizing a spreading sequence transmitted during a plurality of time slots

A spread-spectrum preamble synchronization peak detection system performs multiple statistical tests based on instant and time-averaged channel condition measurements to identify the synchronization peak. In a normalized peak-to-average test, a peak-to-average ratio measurement is normalized by a signal-to-noise ratio measurement to form a new statistical measure which effectively eliminates the impact of the wide dynamic range of the signal-to-noise ratio of the received samples. A transition SNR test is used to eliminate potential false alarms caused by spurious PARN peaks during the transition period at the onset of preamble arrival. Code-phase aligned time-averaging is used to estimate the signal and noise levels over a sliding window. The code-phase alignment of samples effectively separates signal and noise samples in the averaging process, and resulting in more accurate signal and noise measurements. In estimating noise levels, the system takes multi-path interference into account by excluding both the peak signal and the side-lobe signals caused by multi-path wireless channels, resulting in more accurate estimation of noise level.

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Newbury Park, CA, United States of America

Xinyu Wang