Hybrid chaotic sequence for QS-CDMA system with RAKE receiver

A class of the hybrid chaotic sequences is presented. The generator of the sequences is given and realized by the digital method. The hybrid chaotic sequences exhibit good random properties that are very important for the performance of QS-CDMA system with RAKE receiver. The performance of the system is analyzed when the hybrid chaotic sequences are used as spreading codes in a QS-CDMA system with RAKE receiver and compared with those obtained for m-se-quences and logistic sequences. The results show that the hybrid chaotic sequences are a class of very promising spreading codes for QS-CDMA system.

ANALYSIS OF A CUMULANT-BASED 2D-RAKE RECEIVER FOR CDMA SYSTEM OVER FREQUENCY-SELECTIVE FADING CHANNELS

The conventional 2D Rake receivers for code division multiple access (CDMA) system over frequency selective fading channels are generally based on the second order statistics while assuming perfect array conditions. However, the sensor response, location uncertainty, and the use of sample statistics can severely degrade the performance of second order statistics processing. And in practical application, it is impossible to calibrate the array frequently. In this paper a cumulant based 2D Rake receiver for synchronous CDMA system with decorrelator is presented. Decorrelating is a multi user detection approach that not only provides a fundamental solution to the mutual interference problem in CDMA communications but also makes it convenient for the decoupled signal to be processed spatially and temporally. High order signal processing has some inherent advantages over that of second order. Employing second order statistics it is impossible to estimate source steering vector blindly, while employing higher than second order cumulants, this purpose can be achieved. The performance analysis shows that employing cumulant based signal processing technique the proposed 2D Rake receiver is blind and demonstrates excellent performance.

Study on Cell Error Rate of a Satellite ATM System Based on CDMA

Abstract: In this paper, the cell error rete (CER) of a CDMA-based satellite ATM system is analyzed. Two fadingmodels, i. e. the partial fading model and the total fading model are presented according to multi-path propagation fadingand shadow effect. Based on the total shadow model, the relation of CER vs. the number of subscribers at variouselevations under 2D-RAKE receiving and non-diversity receiving is got. The impact on cell error rate with pseudo noise(PN) code length is also considered. The result that the maximum likelihood combination of multi-path signal would notimprove the system performance when multiple access interference (MAI) is small, on the contrary the performance maybe even worse is abtained.

Improved BLAST for wireless communications

Bell layered space-time architecture （BLAST） is a multi-antenna communication structure with high spectrum efficiency, and it has found wide applications in LANs and WLANs. However, its performance is much poorer than those of other space-time coding approaches. In order to improve its performance, an improved BLAST based on RAKE receiving is investigated. The new system introduces orthogonal spreading sequences （OSS） into the transmitter while retains the basic structure of BLAST. The proposed receiver suppresses interferences from other antennas by the orthogonality contained in the received signals, and extracts information from each receiving antenna by using RAKE receiving principle to construct efficient statistic decision. Simulation results show that the improved system performs well over both frequency-fiat and frequency-selective fading channels.

A New UWB Receiver in the Indoor Multipath Environment

In the literatures about Ultra Wide Band （UWB） to date, the receiver structure is mainly based on Rake receiver. But due to the wave distortion caused by overlapped between the received and the sent pulses, a lot of energy in demodulator will be lost. In this paper, a new receiver is developed by adopting maximum likelihood algorithm, in which RAKE structure is not needed and can also be implemented easily. The simulation showed that this method has BER advantage over the traditional RAKE receiver with maximal ratio combining at high SNR, and over the autocorrelation receiver as well.