• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.12
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• pp.12-19
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• 2014

In this paper, an advanced UWB (ultra wideband) Rake receiving technique based on the statistical distribution model is studied in the M-ary TH-PPM system with multiple access interference (MAI). In order to improve the performance of the Rake receiver, the stochastic model, which can flexibly express the behavior of MAI-plus-noise, is required and the Laplace distribution and the generalized normal Laplace (GNL) model applied by the curtosis matching method are considered. The performance of Rake receiver based on each probability distribution is evaluated in the IEEE multipath fading channel and compared to that of the conventional Rake receiver. The suggested approach shows a superior BER performance than that of conventional Rake receiver.

• Journal of Satellite, Information and Communications
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• v.7 no.2
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• pp.59-66
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• 2012

In a frequency selective fading channel, Pre-Rake diversity technique provides simple receiver structure and sufficient diversity effect for mobile terminals. However, conventional Pre-Rake systems are more severely affected than Rake systems with regard to multiple access interference since the number of multipaths received at the mobile unit is nearly twice that of the Rake systems. In order to overcome the problem, a Pre-Rake TDD-CDMA system using zero correlation duration (ZCD) spreading code is proposed. Modified ZCD codes including guard interval (GI) is also proposed and the performance is evaluated by computer simulation under the condition of various channel environment.

• Journal of Satellite, Information and Communications
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• v.12 no.2
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• pp.104-111
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• 2017

Pre-Rake CDMA system using multiple transmit antenna provides a good system performance without equipping a complicated RAKE combiner at the mobile receiver. However, the performance of the Pre-Rake systems are significantly affected by channel estimation error so that the effect of the channel estimation error should be considered and analyzed for evaluating the system performance. In this paper, MISO(Multi-Input Multi-output) Pre-Rake CDMA system with channel estimation error is analyzed by numerical analysis and the results are compared with that of the computer simulation. From the numerical results, it is found that the performance of the Pre-Rake system is more affected by the phase error than the amplitude error.

• Journal of Satellite, Information and Communications
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• v.6 no.1
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• pp.86-96
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• 2011

In this paper we propose a Pre-rake system applied with a frequency domain equalizer in TDD/CDMA multi-code transmission. The Pre-rake system has been well known technique in TDD/CDMA to make a receiver simple. However, it still has residual losses of path diversity and signal to noise ratio (SNR). However, gathering all the residual paths demands an additional hardware such as a rake combiner at the receiver. For the reason Pre/Post-rake system has already been proposed at up/downlink correlated channel conditionunder the assumption of noisier channel. There is a trade-off between the first purpose of Pre-rake that makes hardware simple at the receiver and the performance improvement. From the point the frequency domain equalizer (FDE) can be considered in Pre/Post-rake to supply the receiver with the flexible equalizing methods with rather reduced complexity compared with time domain rake combiner or equalizers. Pre-rake itself increases the number of multipath, which results from the convolution of Pre-rake filter and wireless channel, and FDE must be well matched to Pre/Post-rake, while it considers the relationship of hardware complexity and the performance. In this paper, the Pre-rake/Post-FDE system is introduced at TDD/CDMA multi-code transmission. In addition, the cyclic prefix reduction method in the proposed system is introduced, and the theoretical analysis to the proposed system is given by assuming Gaussian approximation, and finally the numerical simulation results are provided.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.3 no.2
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• pp.25-31
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• 2004

Machinability in metal cutting processes depends on cutting input conditions such as cutting velocity, feed rate, depth of cut, types of work material and tool shape factors. In this study, to assess chip breaking characteristics of a turning process, an equivalent oblique cutting system to this has been established. And the equivalent effective rake angle was determined using side rake angle, back rake angle and side cutting edge angle of the tool. A non-dimensional parameter, Chip breaking index(CB), was used to assess Chip breaking characteristics of chip in conjunction with the equivalent effective rake angle. In case of positive rake angles of the equivalent effective rake, the back rake angle has little effect on the chip breaking characteristics however, in case of negative ones, the side rake angle has some effect on Chip breaking characteristics.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.6
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• pp.1510-1521
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• 1996

This paper presents acquisition algorithm and an improved detection technique for the DS/CDMA (direction sequence code division multiple access) RAKE receiver in multipath fading channel. The DS/CDMA systems use the RAKE receiver, an accurate code acquisition is required for the RAKE branches. The algorithmis able to findthe pseudonoise (PN) code delay estimates for the RAKE branches in a multipath fading channel. In this paper a numerical method and computer simulation simulation have been developed for the acquisition system. The detection probability and mean acquisition time are investigated asa performance measure of the system using the Monte Carlo method. And also in order to analyze the effect of the acquisition on the RAKE receiver this paper bring out the effect of integration time, doppler frequency, processing gain and the number of users on the acquired code phase.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.1
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• pp.123-131
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• 2007

This paper developed a FIR-Rake receiver which makes use of a pilot signal broadcast by the TD-SCDMA (division-synchronous code division multiple access) base station to estimate the channel parameters. The FIR-Rake receiver can reduce multipath interference for the mobile stations. The analysis in frequency and discrete domain and computer simulations confirm that the proposed FIR-Rake receiver achieves a better performance under typical multipath fading propagation conditions.

• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.253-256
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• 2008

In this paper, we analyze the performance of RAKE receiver for impulse radio-ultra wide band (IR-UWB) systems in indoor multipath radio channel. Pulse position modulation-time hopping (PPM-TH) signal is considered. And we also consider three types of RAKE receivers, which are ideal RAKE, selective RAKE, and partial RAKE receivers. The indoor channel is modeled as the modified Saleh and Valenzuela (SV) model which has been proposed as a UWB channel model by the IEEE group, IEEE 802.15.SG3a.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.10A
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• pp.952-959
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• 2006

In this paper, 2-D RAKE receiver simulator is made which beamforming technique is applied to in WCI)MA uplink basestation, and the performance is compared with that of 1-D RAKE receiver with varying the number of array elements, RAKE fingers and users. To model angular component of received signal and interfering signals due to multiple access, it is assumed that multiple users are located in the arbitrary direction of the same distance far from the basestation within a sector of the cell, and the channel simulator is made by using Geometry Based Single Bounce Elliptical Model(GBSBEM) suggested by Rappaport. BER performance is compared and analyzed with the various choise of the number of array elements, the number of RAKE fingers, the number of users and Eb/No. These results indicate that increasing the number of array elements eliminates efficiently multiple access interfering signals and improves dramatically BER performance.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.3
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• pp.179-184
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• 2010

In this paper, we analyze and simulate the performance of RAKE receiver for ultra wide band (UWB) systems in indoor multipath radio channel. Pulse position modulation-time hopping (PPM-TH) signal is considered. And we also consider three types of RAKE receivers, which are ideal RAKE, selective RAKE, and partial RAKE receivers. The indoor channel is modeled as the modified Saleh and Valenzuela (SV) model which has been proposed as a UWB channel model by the IEEE group, IEEE 802.15.SG3a.