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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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The Journal of Korean Institute of Communications and Information Sciences
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Volume 25, Issue 12B - Dec 2000
Volume 25, Issue 12A - Dec 2000
Volume 25, Issue 11B - Nov 2000
Volume 25, Issue 11A - Nov 2000
Volume 25, Issue 10B - Oct 2000
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Resonant Frequency in Rectangular Microstrip Patch Antenna on Uniaxial Substrates with Airgap
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 1759~1759
Resonant frequency in rectangular microstrip patch antenna on uniaxial substrates with airgap is studied by using a rigorous full-wave approach and a moment method calculation. Dyadic Green function is derived for selected uniaxial material by constitutive relation. From these results, integral equations of electric fields are formlated. The electric field integral equations are discretized into the matrix from by applying Galerkin's moment method. Sinusoidal functions are selected as basis functions, which have fast numerical convergence because they resemble in the actual standing wave on the patch. To verify the validity of numerical result, we compare our result with existing one and get a good agreement between them. From the numerical results, the resonant frequencies in the variation of air gap, patch length and anisotropy ratio are presented and analyzed.
Compensation of Laser Diode Nonlinearity in the Optical SCM System for CDMA RF Signal Transmission
최영우 ; 유진태 ; 이길성 ; 박진우 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 1766~1766
Optical SCM(Subcarrier Multiplexing) transmission system has earned more attention recently because it is required to adopt into the future mobile communications services such as voice, image and data services. In spite of the usefulness of SCM optical transmission system, some physical limitations of the system tends to be more serious for CDMA RF signal transmission, of which nonlinear characteristics of the LD(Laser Diode) is most serious. When many CDMA RF signals share a common frequency band, the cumulated RF signal power which is used to drive LD may often exceed the linear operation range of LD causing clipping and saturation in the converted optical signal. This paper analyzes the performance of optical SCM transmission system for CDMA RF signal transmission, and the limiting factors of the SCM system have been indentified. Based on the analyses, a new optical SCM transceiver system is designed and implemented. The performance of the proposed SCM transceiver including LD nonlinearity compensator is measured and its effectiveness is proved in terms of BER improvement of the optical SCM system for CDMA RF signal transmission.
A New FeedForward(FF) Timing Estimation Technique for High-Speed Transmission of Bursts
최윤석 ; 차균현 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 1774~1774
This paper proposes the new feedforward(FF) timing estimation technique using the over-sampled values of preamble for high-speed data transmission of bursts. Performance of the proposed FF timing estimation techinique is presented in terms of DEV(Detection Error Variance) and compared with the conventional several techniques and the MCRB(Modified Cramer-Rao Bound). The proposed scheme is applied to the symbol timing recovery block with the fixed sampling clock and the interpolating filter as a timing corrector. BER is compared with that of ideal case. As a result, it is shown that the negligible performance degradation exists when the proposed scheme is used.
The Adaptive Least Mean Square Algorithm Using Several Step Size for Multiuser Detection
최병구 ; 박용완 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 1781~1781
In this paper, we introduce an LMS algorithm with a modified step size for adaptive filtering. An adaptive feedback constant step size in the LMS algorithm controls the convergence rate of the filter coefficients and determines the final mean-square error. Since convergence time is inversely proportional to step size, a large step size is generally selected for fast convergence. This selection, however, results in increase of mean square error. The proposed detector uses the LMS algorithms with three different step size to reduce mean square error and to obtain fast convergence. In this structure, square errors obtained from each group are compared, and the minimum square error is applied to the selection block. In LMS algorithm, Filter coefficients for each group are upgraded using the output information of the corresponding selection block.
Performance Analysis of Hybrid Interference Cancellation Scheme with Timing or Phase Errors over Rayleigh Fading Channel
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 1787~1787
In this paper, we analyze the average bit error probability of a DS/CDMA system using a hybrid Interference Cancellation (IC) scheme with timing and phase errors under Rayleigh fading channel. We compare the performance of the proposed receiver with that of a conventional receiver with timing or phase errors in terms of the average bit error probability. The bit error probability is derived by using the Gaussian approximation. The performance of the hybrid IC scheme with respect to timing errors (fraction of chip), degree of phase errors, and Eb/No is evaluated. Although an increase of the average bit error probability of the hybrid IC scheme can be observed with increasing timing or phase errors, we obtain much better performance for small timing or phase errors compared to the conventional receiver with no errors.
Performance Analysis of Noncoherent Transimit Diversity System over Correlated Nakagami Fading Channel
여민기 ; 한영열 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 1796~1796
Signal Fading due to multipath propagation severely impairs the performance of high speed mobile communication systems. Effective diversity scheme for fading channel is STTD(Space Time Transmit Diversity) method. In this paper, we derive the new probability density function of the envelope of the received signal over correlated Nakagami fading channel. Using the new pdf of the envelope, we analyze the performance of noncoherent transmit diversity system on correlated Nakagami fading channel.
Erlang Capacity of CDMA Hierarchical Cellular Systems with Soft Handoff
성봉훈 ; 박상규 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 1806~1806
This paper analyzes the system's capacity and the interference resulting from mobiles around a base station depending on the soft handoff ratio for a hierarchical cellular CDMA system. Furthermore the ratio between high speed users in a macro cell and low speed users in a micro cell is studied. It can be seen that the systems's capacity decreases in the presence of more high speed users than low speed users due to an increase of interference. However the increase of the soft handoff region results in less interference and increases the system's capacity.
Development of a Framework for Distributed Learning using the Internet
이종화 ; 허미영 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 1815~1815
Domestic content developers, ISPs and educational institutions are trying to use the Internet and Information Technologies to develop distributed learning systems or services nowadays. In this paper, we present a framework that supports the development of various types of distributed learning services. For this, we analysed the functional requirements of available distributed learning services, defined a set of common functions and then developed it in Internet environment. The framework also provides a web based interface named Configuration Interface for customizing that permits a simple way to develop a specific distributed learning system or service. We developed that framework applying the concepts, components and operational scenario defined in the IEEE LTSA.
The choice of optimal threshold value of spread spectrum Slotted ALOHA network with CLSP method
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 1821~1821
The next generation mobile communication should support not only voice but also multimedia service. The CDMA ALOHA method with CLSP(Channel Load Sensing Protocol) is sensing the load of channel at Base Station's HUB and in case of the reception of packets over fixed threshold value(α) is improved in processing rate better than conventional ALOHA method because it send access improper order to all mobile station. But fixed threshold value indicates ineffective processing rate because of variable traffic load. This paper suggests a algorithm that it should improve processing rate due to choice optimal threshold value(α) by traffic load on the basis of CLSP method in order to improve processing rate of Spread Spectrum ALOHA network. When multimedia traffic mixed voice and data is received to base station, it improve processing rate about realtime traffic due to choice threshold value(γ) of data traffic according to voice with the use of proposed algorithm.
Effects of Non-Uniform Traffic Distribution on the Capacity of Reverse Link CDMA System
조춘근 ; 차균현 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 1828~1828
In this paper, we analyzed the other-cell interference characteristics for various non-uniform traffic distributions and their effects on the capacity of multi-cell CDMA system. We consider three different traffic distributions, i.e., linear, exponential and Gaussian traffic distribution with distribution parameters. Changing the distribution parameter, we can obtain the center-focused distributions or uniform distributions for each model. From the results of other-cell interference calculation we can see that the other-cell interference decreases, as the user concentrates on the base station. Also using frequency reuse efficiency indicating the capacity reduction of a multi-cell system when compared to a single cell system, we evaluate the effect of traffic distribution on the reverse link CDMA capacity. For linear case, the capacity of multi-cell system is reduced to 0.637∼0.867 times that of single cell system. On the other hand, for both exponential and Gaussian cases, the capacity under a multi-cell environment is equal to 70∼100% of that under a single cell. Therefore, we conclude that the average capacity of multi-cell CDMA system are increased when users are likely to be at near the cell base station due to reduced total other-cell interference and decreased when users exist at near the cell edge regardless of traffic distribution models.
Performance evaluation for the channel estimation of LMS adaptive algorithm using pilot symbols for IMT-2000 system
구제길 ; 최형진 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 1836~1836
This paper presents the performance evaluation of a channel estimation algorithm using LMS algorithm for IMT-2000 pilot symbol-assisted W-CDMA reverse link over Rayleigh fading channels. By obtaining BER performance through computer simulations, the LMS algorithm is compared with the WMSA(K=1,2,3), constant estimation gain, and RLS algorithms. The channel structure, modulation and pilot patterns are applied to the 3rd generation partnership project (3GPP) ITU-R proposal for the IMT-2000. The LMS performance with linear interpolation is similar to the WMSA(K=1), constant estimation gain, and RLS algorithm at low Doppler frequencies. However, with high Doppler frequencies, the BER performance of LMS with linear interpolation is more that of WMSA(K=1), constant estimation gain, and RLS algorithm at wide range of Doppler frequencies.
Analysis of Terrestrial Spectrum Requirements in the IMT-2000 Network
장희선 ; 전경표 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 1843~1843
We analyze the terrestrial spectrum requirements in the future IMT-2000 networks by using the ITU-R recommendation. Based on the reference traffic of a user and offered traffic in a cell, we calculate the number of channels and required spectrum in a cell for various traffic conditions. We also perform the sensitivity analysis for the delay time of the packet services. The scheduled services in the year 2010 are classified into circuit and packet switching modes, and three type of environments such as central business district(CBD), pedestrian(PED)and vehicle(VEH) are considered. To determine the number of service chaanels in a cell, the Erlang-B (Erlang loss)formula for the circuit switching services and Erlang0C(Erlang delay) model for the packet switching services have been adopted.
Low Power ASIC Design for IS-95 based CDMA Searcher
김산 ; 황인기 ; 조준동 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 1852~1852
This paper describes the low power design technique of IS-95 based CDMA(Code Division Multiple Access) Searcher. Searcher is composed of dispread, synchronous accumulator, energy computing, comparator, and asynchronous accumulator. The proposed technique consist of rescheduling with strength reduction, precomputation, and low power synchronous accumulator. The system is designed using VHDL, then simulated and synthesized using SYNOPSYSTM. Also, the dissipated power is measured using Design Power in SYNOPSYSTM. We achieved maximum 67% power saving and 41% area saving compared with conventional design.
A Smoothing Presentation Processing Mechanism for Multimedia Synchronization Model
이기성 ; 오해석 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 1861~1861
Real-time application programs have constraints which need to be met between media-data. These constraints represents the delay time and quality of service between media-data to be presented. In order to efficiently describe the delay time and quality of service, a new synchronization mechanism is needed. Multimedia synchronization manages a flexible playout without breaks when playing out media. Thus our proposed scheme handles flexible playout in a point of view of user in order for an audience to view movies more naturally, rather than discarding frames for strict playout. The model results in naturally playing out slave media stream as well.
Interleaving FEC Mechanism for Packet Loss Recovery of the Internet Phone Services
최승권 ; 안상규 ; 조용환 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 1869~1869
This paper proposes an interleaving FEC technique which has combined the advantages of media-specific FEC scheme and interleaving technique, which is being mainly used for wireless communications. By use of interleaving technique, the possibility to recover lost packets can be much increased due to the interleaving characteristics to disperse the effect of packet losses. Nevertheless, in case whole data packets were interleaved, the delay would become a major problem as per the increase of interleaved segments. In this context, the proposed interleaving FEC technique has adopted the interleaving of repair data only, while data packets are being sent in ordinary sequence, to minimize the delay time during transmission. The results of simulation show that the proposed interleaving FEC method has marked higher recovery rate than conventional FEC approach, which is widely being used for internet phone services. In particular, the proposed method will be more effective in case of burst packet losses and higher packet loss environment.
Load-Balanced Routing via Bounded Randomization
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 1879~1879
Future computer networks are expected to carry bursty traffic. Shortest-path routing protocols such as OSPF ans RIP have the disadvantage of causing bottlenecks due to their inherent single-path routing. That is, the uniformly selected shortest path between a source and a destination may become highly congested even when many other paths have low utilization. We propose a family of routing schemes that distribute data traffic over the whole network via bounded randomization; in this way, they remove bottlenecks and consequently improve network performance. For each data message to be sent from a source s to a destination d, each of the proposed routing protocols randomly chose an intermediate node a from a selected set of network nodes, and routes the data message along a shortest path from s to e. Then, it routes the data message via a shortest path from e to d. Intuitively, we would expect that this increases the effective bandwidth between each source-destination pair. Our simulation results indicate that the family of proposed load-balanced routing protocols distribute traffic evenly over the whole network and, in consequence, increases network performance with respect to throughput, message loss and message delay. Moreover, implementing our scheme requires only a simple extension to any shortest-path routing protocol.
ATM 멀티캐스트 스위칭을 위한 브로드캐스트 망 설계
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 1887~1887
In this paper, we present a new broadcast network, which uses a combination of broadcast parallel banyan networks and bypass lines, and evaluate its performance. Most of broadcast switches have been studied on the basis of T. T. Lee's network. Proposed broadcast networks overcome the output load limitations of Lee's copy network, so that achieve high expandability, easier construction and low cell loss rate. To implement proposed networks, we made use of parallelism of the parallel broadcast banyan networks and adopted bypass lines among banyan networks for a full utilization of network resources. Through these bypass lines, blocked cells in networks are-re-transmitted for successful cell transmission. Moreover, we provide CN(Copy Number) comparators for transmitting higher numbered CN cells prior to lower CN cells.
Development of the LCD Driver Interface for Industrial Color TFT LCD Panel Vision System
김남희 ; 조해성 ; 이상태 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 1897~1897
Industrial color TFT LCD vision system is necessary for monitoring to factory automation or highway state, etc. In this paper, we develop LDC driver interface card which receive input signals(NTSC, SECAM, PAL and RGB) and display LCD panel to project input signals on large screen with graphic processing in industrial TFT LCD vision system. Implemented interface card has a capacity of XGA(1024X768). And we test the conformance test of interface card to verify performance. Result shows good performance.
A Study on IDDQ Test Pattern Generation for Bridging Fault Detection
배성환 ; 김대익 ; 전병실 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 1904~1904
IDDQ Testing is a very effective testing method to detect bridging faults occurred in CMOS circuits. In this paper, we consider shorts between gates within circuit under test and implement IDDQ(quiescent power supply current) test pattern generator and fault simulator. Implemented test pattern generator and fault simulator use a new efficient test pattern generation algorithm and fault collapsing schemes to achieve fast run time, high fault coverage and short test sets. Experimental results for ISCAS benchmark circuits demonstrate its efficiency in comparison with results of previous methods.
Implementation of Built-In Self Test Using IEEE 1149.1
박재흥 ; 장훈 ; 송오영 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 1912~1912
In this paper, we describe the implementation of BIST(Built-In Self Test) technique, which is adopted to FLOVA, a floating point DSP core used for image processing and 3D graphics. Logic BIST is applied to data path of floating point module and Memory BIST is applied to both of data memory and program memory which are embedded in FLOVA. Furthermore, boundary scan(IEEE 1149.1) technique is adopted to support board-level testing and the BIST logic we implement.
EIS Processor Architecture for Enhanced Instruction Processing
전중남 ; 김석일 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 1967~1967
This paper proposes the EIS(Enhanced Individual Scheduling) processor architecture, which can individually schedule each unit instruction composing a long instruction word at run time. To process that, the EIS processor architecture has a number of functional unit-individual scheduler unit pairs. Every scheduler of the EIS processor individually determines whether to issue a unit instruction or to stall the functional unit due to resource collision or data dependencies. The EIS processor architecture also has an object code which includes dependency information for every unit instruction to allow synchronization between unit instruction. The EIS processor eliminates delayed processing cycles found in VLIW and SVLIW processors because each unit instruction within a given long instruction word is allowed to be processed independently. The result or simulation promise faster execution cycles of the EIS processor than those of a VLIW or a SVLIW processor. Especially, the EIS processor can significantly reduce the execution cycles of programs that have high ratios of floating-point instructions.
Performance analysis of random spreading and orthogonal spreading DS-CDMA systems in forward link
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 1979~1979
The forward link performance of the DS-CDMA system is affected by the characteristics of spreading sequences. In this paper, the bit error rate(BER) performance is analyzed in terms of the signal to interference ratio(SIR) when orthogonal codes and random codes are used as the spreading sequence. When the convolutional codes and no channel code are employed, the BERs are calculated by Monte Carlo analysis and the verified by computer simulation. Unlike the use of random codes, the use of orthogonal codes can suppress the interference signals with the same path delay. The BER performance with the use of orthogonal spreading codes is better than that with the use of random spreading codes. As the numbers of multipaths increases, the performance difference between the use of the two spreading codes decreases. However, it is shown that the number of users can be at least doubled with the use of orthogonal spreading codes compared to the use of random spreading codes.
A Study on the Delay Adaptive Traffic Scheduling for QoS of Traffic Type
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 1988~1988
A service offer from ATM network is variety service as voice, video, data. It should be premised on acceptance of user's satisfaction. For satisfaction of fundamental demand, resource management in node to node and applicable determination of the transmition sequence consider traffic characteristic in variety traffic for the scheduling method could be required. At follow technical request. this thesis presents the adaptive scheduling method of occurrence transfer delay time from network about traffic characteristics and QoS information offered from traffic creation phases. This kind of method makes an offer of very adaptable and effective control from mixed traffic characteristic structure adapted to the delay margin of traffic arrangement rate alike the multimedia service which gets into the emerging method. I measured a performance of compared with two scheduling method's result equation in mathematical analysis of WFQ existing scheduling method and accomplish mathematical analysis of suggested scheduling method for suggested performance analysis scheduling method. Finally, we compared the normal case and that of the proposed algorithm in a worst case to verify the performance by using the Arena 3.0.
A Priority Scheme for IEEE 802.11 Wireless LAN
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 1996~1996
This paper investigates a priority scheme for IEEE 802.11 Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) protocol in order to provide short access times for priority frames (e.g. time-deadline traffic) even when the overall traffic on the wireless channel is heavy. Under the compatibility constraint for the IEEE 802.11 wireless LANs, two priority systems are simulated: no priority (current IEEE 802.11 standard) for time-deadline traffics and dynamic time-deadline priority. We evaluate algorithms to improve the time-deadline traffic performance using discrete event simulation (DES)
Traffic Shaper in consideration of UPC/NPC in ATM Networks
조태경 ; 최병욱 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 2003~2003
In this paper, we propose a traffic shaper which does not occur the cell loss caused by the Usage Parameter Control/Network Parameter Control at the input link of the receiving ATM node. The proposed traffic shaper is for the non real time-Variable Bit Rate(nrt-VBR) traffic and has an independent queue for each ATM connection. For the selection of a proper queue which has cells for transmission to the output link, we execute the GCRA for each queue, As a result of the GCRA, all the queues in the transmit enable state are selected first. Then, a proper queue among the queues in the transmit enable state is selected by using the time-dependent probability scheduling algorithm proposed in this paper. To evaluate the performance, we simulate the proposed shaper with the other shapers using the WRR scheduling algorithm and the WFQ scheduling algorithm. The results show that the proposed shaper is superior to the other shapers in terms of the cell loss rate for the nrt-VBR traffic.
Design of AVTMR system and Evaluation of RAM (Reliability, Availability, Maintainability)
김현기 ; 이기서 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 2016~2016
In this paper, we developed AVTMR(All Voting Triple Modular Redundancy) system which is operated correctly in case of a fault and evaluated AVTMR system in failure rate based on MILSPEC-217F. AVTMR system is designed in a triplicated voter and MC68000. Markov model is designed to evaluate the reliability, availability, maintainability and MTTF(Mean Time To Failure) and AVTMR system will be compared with SS(Single system) as the commercial element and the Milspec. We can see that AVTMR system has a higher dependability than single system by evalution, and because of fault-tolerant characteristic, AVTMR system can be applied to the airplane and the railway system.
The method of frequency offset estimation and frame synchronization with chirp signal in OFDM system
Park, Jong Uk ; Hwang, In Ho ; Yun, Jang Hong ; Hong, Jae Geun ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 2025~2025
Efficient Huffman decoder using octal tree search algorithm
우광희 ; 한헌수 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 2033~2033
Huffman coding which has been used in many data compression algorithms is popular data compression technique to reduce statistical redundancy. It has been proposed that Huffman decoding algorithm can decode efficiently using characteristics of Huffman tables and patterns of Huffman codewords. We propose a new Huffman decoding algorithm which used octal tree search technique, and present efficient hardware implementation method. This algorithm has a small logic area and memory space, and is optimized for high speed decoding. Proposed Huffman decoding algorithm can be applied for many multimedia systems such as MPEG audio decoder.
A Simple GMSK Modulator Using the Combined Gaussian Lowpass Filter and Integrator
오성근 ; 황병대 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 2039~2039
In this paper, we propose two computationally simple Gaussian minimum shift-keying(GMSK) modulators. In the proposed methods, we can significantly reduce the computational complexity by pre-computing phase quantities at the integrator output due the input data sequence to be filtered and by using a read only memory(ROM) table, instead of the sequential processing of Gaussian filtering and consecutive integration. In the first method, the phase variations at sample times due to data symbols to be filtered are pre-computed, and a phase sample is obtained by computing and accumulating a total phase variation at the sample time due to the input data sequence to be filtered. In the second method, the total phase variations at all possible sample times due to all the possible data sequences are pre-computed and stored, in which a phase sample is obtained by selecting and accumulating a total phase variation at the sample time corresponding to the input data sequence. In addition, for the second method, exploiting symmetric property of the total phase variations according to data sequence patterns can reduce the required memory size.
Speech Quality Measure in a Mobile Communication System using PLP Cepstral Distance with CMS
박영철 ; 안동순 ; 윤대희 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 2046~2046
In this paper, we propose a new speech quality measure, PLP-CMS(Perceptual Linear Predictive-Cepstral Meal Subtraction) that has a better and robust performance for the speech of various channel effects than the conventional speech quality measure. PLP-CMS has a high correlation with subjective speech qualities owing to PLP analysis and show a robust performance not being influenced by PSTN channel effects due to CMS(Cepstral Mean Subtraction).
A CSD linear phase FIR filter architecture using artificial common sub-expression
장영범 ; 이혜림 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 2052~2052
Multiplierless CSD(canonical signed Digit) filter architectures are widely investigated for the application of high-speed and low-power wireless communication systems like digital IF(Intermediate Frequency) filters. In this paper, we propose a CSD architecture with minimum adders for linear phase FIR(Finite Impulse Response) filters. Reduction of the number of adders through sharing the common sub-expression has been used in fast filter application. We propose new techniques to make artificial common sub-expression through the bit shift, bit add, and bit complement. As an example, we utilize the 73 taps FIR filters with specification in the first version of CDMA cellular. It is shown that the proposed CSD format architecture achieves 9.2% adder reduction comparison to the conventional common sub-expression sharing architecture.
Channel Identification and Predistorter Design Using Stochastic Gradient Method
인민교 ; 은창수 ; 김용진 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 2060~2060
We present the identification and compensation method for non-linear systems with memory which arise due to the transmit/receive filters and the non-linearity of a power amplifier. Such a non-linear system can be modeled as a linear system, a memory-less nonlinear system, and a linear system cascaded sequentially. We obtain the filter coefficients of the linear systems and the coefficients of a polynomial approximating the memory-less non-linear system through the stochastic gradient method(SGM). We compensate for a non-linear communication system that can be modeled as above with a predistorter using the same method SGM and the indirect learning architecture. The non-linear compensation method presented here does not need a specific modeling scheme and can be applied adaptively.
An Efficient Structure of a Baseband Predistorter and Its Implementation for OFDM Systems
Sin, Yo An ; Im, Seong Bin ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 2069~2069
The content-based ultrasound image retrieval by wavelet transform and spatial histogram
Kim, Beom Su ; Gwak, Dong Min ; Won, Jong Un ; Kim, Nam Cheol ; Park, Gil Heum ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 2085~2085
A Study on the Reliable Video Transmission Through Source/Channel Combined Optimal Quantizer for EREC Based Bitstream
김용구 ; 최윤식 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 2094~2094
Current outburst needs for multimedia communication over error prone network such as mobile channel pose many challenging problems. One of the most important issues is the error handling technique for transmitted bitstream including video because the errors severely propagate through spatio-temporal direction in video and thus may cause serious degradation in reconstructed video quality. In order to prevent such devastating error effects, error resilient entropy coding (EREC) technique was applied to the proposed scheme in this paper. We analyze the error propagation in EREC based on a specific searching pattern, and then develop an estimation technique for the probability of a basic coding unit being in error at its decoding. Then we approximate the estimated probability to model the end-to-end degradation by the function of generated number of bits for each basic coding unit. Based on the approximation, we propose a new optimal quantization scheme, in order to make the transmitted video more resilient to the channel erros. Our method is optimal in the sense that the distortion
Performance Analysis of Packet CDMA R-ALOHA for Multi-media Integration in Cellular Systems with Adaptive Access Permission Probability
허경 ; 엄두섭 ; 차균현 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 2109~2109
In this paper, the Packet CDMA Reservation ALOHA protocol is proposed to support the multi-traffic services such as voice and videophone services with handoff calls, high-rate data and low-rate data services efficiently on the multi-rate transmission in uplink cellular systems. The frame structure, composed of the access slot and the transmission slot, and the proposed access permission probability based on the estimated number of contending users for each service are presented to reduce MAI. The assured priority to the voice and the videophone handoff calls is given through higher access permission probability. And through the proposed code assignment scheme, the voice service can be provided without the voice packet dropping probability in the CDMA/PRMA protocols. The code reservation is allowed to the voice and the videophone services. The low-rate data service uses the available codes during the silent periods of voice calls and the remaining codes in the codes assigned to the voice service to utilize codes efficiently. The high-rate data service uses the assigned codes to the high-rate data service and the remaining codes in the codes assigned to the videophone service. Using the Markov-chain subsystem model for each service including the handoff calls in uplink cellular systems, the steady-state performances are simulated and analyzed. After a round of tests for the examples, through the proposed code assignment scheme and the access permission probability, the Packet CDMA Reservation ALOHA protocol can guarantee the priority and the constant QoS for the handoff calls even at large number of contending users. Also, the data services are integrated efficiently on the multi-rate transmission.
Construction Schemes of Cyber low System in Art Image Contents
최종호 ; 고덕영 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 2120~2120
An important issue in image contents industry is to construct the flow systems of new art image contents. In recent years, a number of flow systems have been developed in art image contents industry. Specially, the flow of art sensibility-based image contents is very important subject in field of animation, game, advertisement, broadcasting, cinema, video industry. But the study on flow systems of art image contents is not performed in Korea. Accordingly, we performed the study on the flow systems of art sensibility-based image contents. This research may provide a way of developing the intrinsic model for process, editing, distribution, and flow of art sensibility-based image contents. It also will contribute to development of korean art image contents, reduction of system import, construction of virtual studio, and growth of art image contents industry.
Economic Issues arising from sharing the Network of IMT-2000
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 2131~2131
Third-generation mobile telecommunication systems(IMT-2000) will be an essential element of the future telecommunication infrastructures. the characteristics of IMT-2000 such as lumpy investment and vast initial investment would require to set up appropriate plans and strategy for IMT-2000, which consider the national competitive advantages and benefits of end-users. The aim of this study is to investigate the validity of sharing network of IMT-2000. Specifically, this study discusses the validity of introduction of sharing the network and suggests a reasonable way of share the network overcoming the problems generated by sharing the network. Spectrum allocated for IMT-2000 is a finite resource and therefore the number of IMT-2000 license holders will be limited and market will be closed oligopoly. In Korea, three licenses are currently planned in view of the spectrum available. Therefore, sharing the network between service providers would be resonable in the view of promoting competition in the market and reducing investment to build out a network.
Non-synchronized Sampling Techniques for DMT-based xDSL Modems
김재권 ; 백종호 ; 유영환 ; 조진웅 ; 조용수 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 12, 2000, Pages 2141~2141
In this paper, we analyze timing errors (sampling phase-offset and sampling frequency-offset) occurring in DMT-based xDSL systems and then propose non-synchronized sampling (full digital PLL) techniques to compensate the sampling errors at the digital receiver. In the previous paper, the non-synchronized sampling technique with the frequency-domain rotor was proposed to compensate the sampling phase-offset in the DMT-based xDSL systems using delay-rotor property. However, the delay-rotor property dose not hold any longer if the signal passed through an analog low-pass filter is sampled with phase errors. In this paper, a non-synchronization sampling technique, which can compensate the sampling phase-offset perfectly by making data portion cyclic-convolutionized even in the case of sampling phase-offset present, is proposed. Also, an improved hybrid time-domain/frequency-domain correction technique is proposed for the case where both sampling phase-offset and sampling frequency-offset exist. A time-domain correction technique which does not require any additional overhead for the case with both offsets is proposed. Finally, the performances of the proposed non-synchronized sampling techniques are investigated by applying them to a DMT-based ADSL system and compared with the ones of the previous techniques through computer simulations.