New acquisition decision algorithm for multiple access interference suppression in DSSS system

For decreasing the multiple access interference of weaker signal acquisition in direct sequence spread spectrum（DSSS） systems,a new single decision algorithm is presented.The maximum value of correlation results is conventionally detected.However,there may be not only one strong peak among correlation results when the cross-correlation noise is strong enough to affect the correlation results.The proposed algorithm decreases the false alarm probability through the decision of the ratio of the maximum value and the second maximum value of the correlation results.Theoretical analysis and simulation results indicate that the proposed algorithm effectively suppresses the acquisition problem of multiple access interference in DSSS system.

New Acquisition Algorithm for Direct Sequence Spread Spectrum Signals

Aiming at improving acquisition performance for direct sequence spread spectrum （DSSS） signals, a new acquisition algorithm based on fast Fourier transform （FFT） is proposed. The code phases are parallel searched throughout the Doppler frequency domain. Since the influence of Doppler frequency errors on peak-to- average ratios of correlation power shows a pattern similar to the sinc function, it is our belief that by judging on peak-to-average ratios for different Doppler frequency errors false alarm probabilities should be lowered. Analyses have supported the underlying principle of this new algorithm. Simulation results have also indicated that the new algorithm can effectively improve the acquisition performance for DSSS signals.

Enhanced spectrum sensing using a combination of energy detector,matched filter and cyclic prefix

In this paper,we propose a sensing scheme based on energy detection,matched filter and cyclic prefix.Both Equal Gain Combining(EGC)and optimal combination of the aforementioned detectors are investigated in cooperative and non-cooperative spectrum sensing scenarios.In packet transmission systems such as OFDM(Orthogonal Frequency Division Multiple access)systems,the proposed scheme takes advantage of utilizing more samples than individual detectors,i.e.,cyclic prefix,training or pilot samples,and data payload samples.The proposed combine-sensing scheme offers higher detection probability and lower false alarm probability,as compared with the performance of individual detectors over the same frame duration.Simulation results are congruent with the theoretical curves and confirm the validity of our derivations.

DCT domain filtering method for multi-antenna code acquisition

For global navigation satellite system （GNSS） signals in Gaussian and Rayleigh fading channel, a novel signal detection algorithm is proposed. Under the low frequency uncertainty case, after performing discrete cosine transform （DCT） to the outputs of the partial matched filter （PMF） for every antenna, the high order com- ponents in the transforming domain will be filtered, then the equalgain （EG） combination for the inverse discrete cosine transform （IDCT） reconstructed signal would be done subsequently. Thus, due to the different frequency distribution characteristics between the noise and signals, after EG combination, the energy of signals has almost no loss and the noise energy is greatly reduced. The theoretical analysis and simulation results show that the detection algorithm can effectively improve the signal-to-noise ratio of the captured signal and increase the probability of detection under the same false alarm probability. In addition, it should be pointed out that this method can also be applied to Rayleigh fading channels with moving antenna.

Robust and Low-Complexity Synchronization for Energy Detection UWB Receiver

A simple method using aided sliding rectangular windows for synchronization in energy detector （ED） receiver is proposed for impulse-based ultra wideband radios （IR-UWB） under binary pulse position modulation （PPM）, therefore grants an attractive solution for gaining low complexity while the accompanying performance loss in terms of UWB signal reception is comparatively low. Also, a method is developed to sup- press noise through accumulation of integrated results before synchronization point is reached. This proposed method can effectively reduce the impact of one of the major performance-degrading factors in ED receivers, i. e., noise caused by heightened noise floor due to large bandwidth product. Our theoretic work on this im- proved synchronization performance and relevant simulations are conducted on IEEE 802.15.4a channel mod- els, and results show that the proposed design scheme can effectively decrease both the probability of false alarm and probability of missed detection.