Parallel Combinatory Spread Spectrum Research Articles

High performance bit‐activation code index modulation method

AbstractWith the increasing demand of applications for the spread spectrum technique, especially the demand for data transmission rates and spectral efficiency, the advantages of the traditional direct sequence spread spectrum (DSSS) system are limited. Therefore, multi‐ary spread spectrum (M‐ary) technology, parallel combinatory spread spectrum (PCSS) technology, and code index modulation (CIM) technology have been proposed. Although these three new technologies can improve the data rate, they all face the problem of the large consumption of pseudo‐code resources. In order to solve the problem of pseudo‐code resources, a bit‐activation code index modulation (BA‐CIM) method is proposed. At the transmitter, considering the good correlation among multiple pseudo‐codes, the corresponding pseudo‐code activation principle is established, and the corresponding spreading pseudo‐code is activated by using the status of each bit of the index data according to the pseudo‐code activation principle. Then, multicode superposition processing is carried out to spread the modulation data. At the receiver, the corresponding activation pseudo‐code is obtained using the maximum peak‐to‐average ratio (MPAR) and secondary peak‐to‐average ratio (SPAR) judgement mechanisms to decode the multibit index data. Compared with existing methods, the proposed BA‐CIM method can not only achieve a better bit error rate performance but also use the least pseudo‐code resources. Moreover, BA‐CIM has the best comprehensive performance improvement and is far superior to other methods. This research can provide technical support for the application of efficient spread spectrum communication.

Communication and ranging composite system based on parallel combinatory spread spectrum technology

Communication and ranging composite system based on parallel combinatory spread spectrum technology

Communication and ranging composite system based on parallel combinatory spread spectrum technology

Communication and ranging composite system based on parallel combinatory spread spectrum technology

Optical Wireless N-CSK with Modified Pseudo Orthogonal M-Sequence Sets

In this paper, N-CSK (N parallel Codes Shift Keying) using modified pseudo orthogonal M-sequence sets (MPOMSs) to realize the parallel combinatory spread spectrum (PC/SS) communication system for the optical communications is proposed. Moreover, the upper bound of data transmission rate and the bit error rate (BER) performance of this N-CSK system using the chip-level detection are evaluated through theoretical analysis by taking into account the scintillation, background-noise, avalanche photo-diode (APD) noise, thermal noise, and signal dependence noise. It is shown that the upper bound of data transmission rate of the proposed system is better than those of OOK/CDM and SIK/CDM. Moreover, the upper bound of data transmission rate of the proposed system can achieve about 1.5[bit/chip] when the code length of MPOMS is 64[chip].

Constant Amplitude Signaling for Parallel Combinatory Spread Spectrum Systems

In this paper, a parallel combinatory spread spectrum (PC/SS) system using a constant amplitude signaling scheme is proposed. The amplitude of the transmitted signal from multicode transmission systems such as PC/SS systems have a large dynamic range which requires that amplifiers have a wide linearity in the transmitter. From a view point of power efficiency, however, it is reasonable to use non-linear amplifiers rather than linear ones. In that case, the bit error rate performance must degrade because of non-linear distortion. The proposed system can avoid influence of the non-linear amplifiers by making the transmitted signal have a constant amplitude. The bit error rate performance and the data transmission rate performance are investigated. They prove that the proposed system is an attractive candidate among the constant amplitude signaling systems.

On Schemes for Multriate Support in DS-CDMA Systems

Different modulation schemes supporting multiple data rates in a Direct Sequence Code Division Multiple Access (DS-CDMA) system are studied. Both AWGN and multipath Rayleigh fading channels are considered. It is shown that the multi processing-gain scheme and the multi-channel scheme have almost the same performance. However, the multi-channel scheme may have some advantages due to easier code design and multiuser receiver construction. The drawback though, is the need for linear amplifiers also in mobile terminals. A multi-modulation scheme is also possible, but the performance for the users with the high data rates are significantly worse than for the other schemes. Furthermore multi chip-rate, parallel combinatory spread spectrum (PC/SS), pulse position modulation (PPM) and variable duty cycle schemes are discussed briefly.

Performance of differential parallel combinatory spread spectrum communication systems

AbstractThis paper proposes differential parallel combinatory spread spectrum (DPC/SS) communication systems; one of the parallel combinatory spread spectrum (SS) communication systems the authors have been studying so far. the parallel combinatory SS system is a spectral efficient SS system in which the system transforms sever al bits of data into a combination of pseudonoise (PN) sequence with modulation of positive and negative signs and transmits them.The proposed DPC/SS system applies differential encoding to the positive or negative sign modulation of the PN sequences, and then they are transmitted. In the receiver, the combination of a transmitted sequence set is estimated by noncoherent detection and the coded sign is demodulated by differential detection. Thus, the receiver does not need to regenerate the phase of the carrier frequency. the proposed systems will be applicable to a mobile cellular system in which a large phase variation interferes with the communications.This paper evaluates the error performances. of the DPC/SS systems in additive white Gaussian noise (AWGN) channels and frequency‐nonselective, slowly Rayleigh fading channels. It also evaluates the effect of diversity in the Rayleigh fading channels.In the AWGN channel, the DPC/SS system is superior by I dB to the differential phase‐shift keying (DPSK) system and to the BPSK system in terms of required signal‐to‐noise ratio at 10‐8 bit error rate (BER) at the same spectral efficiency. In the Rayleigh fading channel, diversity reception in the DPC/SS system gains more improvement in the BER performance, as the number of branches increases, than that obtained in a direct‐sequence spread spectrum system with DPSK.

Error control technique for parallel combinatory spread spectrum communication system

AbstractThis paper discusses the application of the error control technique for parallel combinatory spread spectrum (PC‐SS) communication system proposed previously by the authors. This paper considers the case where &‐bit information is transmitted in the spreading sequences and considers the following two coding methods as suited to PC‐SS systems: 1) to use 2k‐ary Reed‐Solomon code; and 2) to use the constant‐weight code by Chung et al. in the transmitter, converting the data into the combinatory spreading sequences, and to suppress the error in the receiver by taking the double correlation. The bit‐error rate performance is examined for the two methods and the effectiveness is discussed.It is shown as a result that both methods are useful in improving the bit‐error rate of the PC‐SS system. In the latter method, the number of spreading sequences needed per user is reduced to approximately one‐fourth compared to the conventional PC‐SS system with nearly the same bit‐error rate.