Modulation and processing gain tradeoffs in DS-CDMA spread spectrum systems

Asano, David K.; Hayashi, Tetsuya; Kohno, Ryuji

doi:10.1109/isssta.1998.726185

Cited by 8 publications

(10 citation statements)

References 4 publications

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“…Firstly, the constant envelope allows the usage of the nonlinear amplifiers which are more powerefficient and cheaper. Moreover, the narrow power spectral density (PSD) will increase the processing gain in band-limit conditions and the spread-spectrum techniques will make the signal format to have a low probability of intercept (LPI) [3]. Finally, based on the correlation properties of pseudorandom spreading sequences, a remarkable diversity gain effect can be obtained using RAKE receiver under a multipath channel and a code division multiple-access (CDMA) system is available for multiuser scenarios [4].…”

Section: Introductionmentioning

confidence: 99%

Coherent RAKE Receiver for CPM-Based Direct Sequence Spread Spectrum

Zhou¹,

Wang

Er-yang

2016

Mathematical Problems in Engineering

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Direct sequence spread spectrum (DSSS) using continuous phase modulation (CPM) inherits the techniques' benefits, constant envelope, anti-interference, and spectral efficiency. To get diversity gains over a Rayleigh-fading multipath channel as in conventional direct sequence spread-spectrum binary phase shift keying (DSSS-BPSK) system, a new class of coherent RAKE receivers is proposed in this work. By introducing chip branch metric to the receiver scheme, despreading and data detection can be done meanwhile based on Maximum Likelihood Sequence Detection (MLSD). Compared to the conventional RAKE receiver which sums decision metrics symbol-by-symbol, the proposed DSSS-CPM RAKE receiver accumulates symbol branch metric increments over every phase state of multiple paths after chip phase synchronization. Numerical results show that DSSS-CPM using the synchronous despreading and demodulation algorithm has no performance loss compared to CPM system that employs MLSD algorithm under the same test conditions. Moreover, the proposed RAKE receiver outperforms conventional RAKE receiver and achieves a remarkable diversity gain of bit error rate (BER) under the Rayleigh-fading multipath channel.

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Section: Introductionmentioning

confidence: 99%

Coherent RAKE Receiver for CPM-Based Direct Sequence Spread Spectrum

Zhou¹,

Wang

Er-yang

2016

Mathematical Problems in Engineering

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“…CPM is an attractive modulation method that has excellent spectral characteristics due to continuous phase change, and high power utilization efficiency due to the constant envelope waveform. Thus, many researchers are investigating CPM‐CDMA systems in which CPM is employed for primary modulation in CDMA (code division multiple access) .…”

Section: Introductionmentioning

confidence: 99%

“…However, this issue was not considered in previous studies of CPM‐CDMA systems. Asano and colleagues pointed out the trade‐off relation between the spreading gain and the CPM modulation index h and evaluated performance with a fixed postspread bandwidth. However, no band‐limiting filter was applied to BPSK, which prevented a fair comparison .…”

Section: Introductionmentioning

confidence: 99%

“…Asano and colleagues pointed out the trade‐off relation between the spreading gain and the CPM modulation index h and evaluated performance with a fixed postspread bandwidth. However, no band‐limiting filter was applied to BPSK, which prevented a fair comparison . In real systems, band‐limiting filters are used for BPSK, which should be reflected in the comparison.…”

Section: Introductionmentioning

confidence: 99%

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A Method of Constructing Phase Spreading Sequences for CPM‐CDMA Systems

Morioka

Asano

2015

Elect Comm in Japan

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SUMMARY In this paper, a construction method for phase spreading sequences that is suitable for CPM‐CDMA systems is proposed. Using these sequences, the performance of asynchronous CPM‐CDMA systems with traditional BPSK/OQPSK‐CDMA systems and the trade‐off between the spreading factor and modulation parameters are considered. Numerical results show that the optimal modulation index for CPFSK‐CDMA systems is h=0.5 and the performance is better for lower values of BbTc in GMSK‐CDMA systems. Also, we found that the user capacities of MSK‐CDMA systems are 2.3 times larger than those of BPSK/OQPSK‐CDMA systems.

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“…Also, error correction is possible due to the inherent phase memory in the signaling scheme. Therefore, CDMA systems using CPM as the first modulation scheme were studied in the literature (1)- (4) .…”

Section: Introductionmentioning

confidence: 99%

Extended Summaries

2014

IEEJ Trans.EIS

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The study of nanoimprint lithography (NIL) has attracted much attention for many industrial fields because it is a promising method to fabricate various nanostructures with a low cost and a high throughput. In the process of NIL, the mold is usually coated with an antisticking layer to avoid resist adhesion. As an antisticking layer of nanoimprint mold, the fluorinated self-assemble monolayer (F-SAM) is used, for example. The evaluation of the F-SAM with different chain length is one of the critical issues in NIL. In this study, four kinds of F-SAMs with different chain length were evaluated using the photoelectron and the near edge X-ray absorption fine structure (NEXAFS) spectroscopies. Four kinds of F-SAMs were prepared from a precursor [CF 3 (CF 2) n (CH 2) 2 Si(OCH 3) 3 ; n = 0, 3, 5, and 7] as denoted FAS-3, 9, 13, and 17, respectively. All photoelectron and NEXAFS measurements were performed on a BL7B end station at the NewSUBARU facility, University of Hyogo. The photoelectron spectra were measured using the Mg Kα line at the total energy resolutions of about 0.7 eV for the C 1s core-level region. NEXAFS spectra were measured using the synchrotron radiation by the total electron yield method. The total energy resolution was about 0.5 eV. In Figure 1, the photoelectron spectra of the C 1s core-level region in four kinds of F-SAMs with different chain length are plotted. In the photoelectron spectra of the C 1s core-level, three peaks at 292, 286, and 284.5 eV were observed in FAS-3 although four peaks at 293, 291, 286, and 284.5 eV were observed in FAS-9, 13, and 17. With increasing the chain length, the intensity of the peak at 291 eV increased while the intensity of the peaks at 293 and 286 eV did not change. From the chemical compositions of four kinds of F-SAMs with different chain length, these peaks at 293, 291, 286, and 284.5 eV were assigned to the CF 3 , CF 2 , CH, and CC components, respectively. In FAS-3, the CF 3 component shifted to lower binding energy side by 1 eV since there is no CF 2 chain. Figure 2 shows the NEXAFS spectra in four kinds of F-SAMs with different chain length. Several peaks were observed at 285, 290, 292, 295, and 299 eV. The intensity of the peaks at 292 and 299 eV increased with increasing the chain length. On the other hand, the intensity of the peaks at 285, 290, and 295 eV did not change with increasing the chain length. The peaks at 292 and 299 eV were assigned to the σ*(C-F) transition from C 1s core-level. On the other hand, these peaks at 285, 290, and 295 eV were assigned to the π*(C-C) and σ*(C-H), π*(C=O) and σ*(C-H), and σ*(C-C) components, respectively. When the incidence angle of the linearly polarized synchrotron radiation to the sample surface increased, the intensity of the peaks at 292 and 299 eV increased. This indicates that the σ*(C-F) orbital is parallel to the surface and that the CF 2 chain in F-SAMs is perpendicular to the surface. Intensity (arb.units) 295 290 285 280 Binding energy (eV)

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Modulation and processing gain tradeoffs in DS-CDMA spread spectrum systems

Cited by 8 publications

References 4 publications

Coherent RAKE Receiver for CPM-Based Direct Sequence Spread Spectrum

Coherent RAKE Receiver for CPM-Based Direct Sequence Spread Spectrum

A Method of Constructing Phase Spreading Sequences for CPM‐CDMA Systems

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