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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
Volume 25, Issue 10A - Oct 2000
Volume 25, Issue 9B - Sep 2000
Volume 25, Issue 9A - Sep 2000
Volume 25, Issue 8B - Aug 2000
Volume 25, Issue 8A - Aug 2000
Volume 25, Issue 7B - Jul 2000
Volume 25, Issue 7A - Jul 2000
Volume 25, Issue 6B - Jun 2000
Volume 25, Issue 6A - Jun 2000
Volume 25, Issue 5B - May 2000
Volume 25, Issue 5A - May 2000
Volume 25, Issue 4B - Apr 2000
Volume 25, Issue 4A - Apr 2000
Volume 25, Issue 3B - Mar 2000
Volume 25, Issue 3A - Mar 2000
Volume 25, Issue 1B - Jan 2000
Volume 25, Issue 1A - Jan 2000
Volume 25, Issue 9 - 00 2000
Volume 25, Issue 8 - 00 2000
Volume 25, Issue 7 - 00 2000
Volume 25, Issue 5 - 00 2000
Volume 25, Issue 4 - 00 2000
Volume 25, Issue 2B - 00 2000
Volume 25, Issue 2A - 00 2000
Volume 25, Issue 1 - 00 2000
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Volume 25, Issue 10 - 00 2000
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Analysis on the Cell Capacity and Coverage of 3GPP systems
양하영 ; 김주응 ; 정현민 ; 홍대식 ; 강창언 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1461~1461
Recently the mobile users seem to be rapidly increasing and then the capacity limit will be reached at close hand. In these situations to provide them with good quality of service in the coming future newly planned cell design is needed. In the next generation mobile communication system namely IMT-2000 good quality services will be possible only by designing the cell structure hierarchically with the help of appropriate cell planning. In the research process that are essential to cell planning are also researched. modeling of IMT-2000 radio link and the parameters that are essential to cell planning are also researched. Modeling of IMT-2000 radio link and the numerical analysis on that make it possible to calculate the forward/reverse link budget system capacity call blocking probability Erlang capacity and cell coverage. In planning the cell of IMT-2000 system various parameters are considered such as hierarchical cell structure number of users data service forms and propagation area environments. From the results efficient cell planning methods are proposed. through this thesis efficient cell planning and maximum capacity will be achieved in the beginning of commercial IMT-2000 service.
Performance Evaluation of Bandwidth Efficient Adaptive QAM Schemes in Flat and Frequency Selective Fading Channels
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1473~1473
This paper presents the performance evaluation of an adaptive QAM scheme under flat and frequency selective fading channels for indoor wireless communication systems. The QAM modulation is combined with differential encoding and the demodulation process is carried out noncoherently. The adaptation is performed by varying the modulation level of QAM depending upon received signal strength. The adaptation mechanism allows a 2- or 3-bit increase or decrease at a time if the channel condition is considered to be significantly good of bad. Simulation results show that the average number of bits per symbol (ABPS) for each symbol block transmitted over a flat fading channel is higher than 5.0 and the BER performance is better than 10-4 for a SNR value higher than 30 dB,. For frequency selective fading channels an oversampling technique in the receiver was employed. The BER performance obtained for frequency selective fading channels is better than 10-4 with a SNR value of 40 dB and ABPS is found to be approximately 5.5 Therefore this scheme is very useful in that it provides both very high bandwidth efficiency and acceptable performance with moderated SNR values over flat and frequency selective fading channels. In addition this scheme provides reduced receiver complexity by way of noncoherent detection.
Synchronization Sequence Design for Digital Cellular Mobile Communications
한영열 ; 안광진 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1480~1480
This paper presents and efficient synchronization sequence design for the digital cellular telephone. The class of synchronization sequences studied in this paper are sequences for synchronization that have the lowest out-of-phase values of the autocorrelation function with the two peak values equal in magnitude and opposite in polarity at zero and middle shifts. These synchronization sequences can be used to double-check synchronization timing and reduce the synchronization search time.
DS/MC-CDMA system performance through Rayleigh fading channel in the presence of partial band interference
김인겸 ; 안성준 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1486~1486
A Multicarrier system required a lower speed paralled-type of signal processing in contrast to a fast serial processing in a single carrier CDMA system. For the analysis we evaluate MC-CDMA system performance with that of a single-carrier CDMA system and a multi-carrier CDMA system based on the various jamming conditions. Also we studied to the capacity level against the threat environment through the performance comparison in commercial CDMA system and Limiting repeater system. as a result we found that M-CDMA system has a robustness to narrowband interference and multipath environments like as a Rayleigh fading.
An Improved Rayleigh Fading Compensation Algorithm with Modified Sinc Interpolation
이창재 ; 황성현 ; 최형진 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1492~1492
Pilot symbol aided modulation (PSAM) using the conventional sinc interpolation (CSI) achieves nearly the same BER performance as Caver' optimal Wiener interpolation but with much less complexity. The CSI however has to use a non-rectangular window function that is applied to the sinc function to smooth out the abrupt truncation of rectangular window. In this paper we propose the modified sinc interpolation (MSI). With the weighting factor the MSI scheme with no window has almost the same BER performance as the CSI scheme using window, In addition if we use the MSI with a window its BER performance gets close to that of the theoretical one. We assume the multicarrier QAM system and an optimal frame structure for performance evaluation
Synchronization Algorithms and Implementation of PC Based Receiver of Eureka-147 Digital Audio Broadcasting
조재희 ; 조남신 ; 방극준 ; 전희영 ; 박명희 ; 박현철 ; 홍대식 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1499~1499
We have designed and implemented a receiver of Eureka-147 Digital Audio Broadcasting (DAB) scheme. DAB (orthogonal frequency division multiplexing) as its transmission technique that is very sensitive to synchronization error. So reliable synchronization algorithm have been proposed and evaluated. With the algorithms we proposed a PC based real-time DAB receiver has been implemented. We find that the receiver performs satisfactorily to meet the specifications we determined.
Bandwidth Reservation scheme Using Mobile Tracking
정혜명 ; 전문석 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1512~1512
The wireless communication network is evolving toward IMT-2000 for providing various multimedia services. In order to accomplish this ultimate goal the effective schemes are required which can dynamically utilize the limited wireless resources based on different traffic characteristics of various services. This paper proposes a novel bandwidth allocation and call admission control scheme to transmit multimedia traffic based on the bandwidth reservation procedure using direction estimation in the IMT-2000 This scheme estimates the position of mobiles based on the mliticriteria decision making in which uncertain parameters such as RSS(Received Signal Strength) the distance between mobile and base station the moving direction and the previous location are participated in the decision process using aggregation function in fuzzy set theory. Its effectiveness is investigated by simulation.
Performance of CDMA System in the Extended Suzuki Model of LEO Satellite
박성조 ; 박상규 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1521~1521
In this paper we analyze the performance of a DS/CDMA system in LEO mobile satellite channels. The channel uses the Extended Suzuki model which is the product of a Rician distribution having a LOS component and a lognormal distribution due to shadowing. We assume that the signal transmitted from the satellite to the mobile undergoes the same fading for the whole coverage of signal's beam. The average bit error probabilities of double coverage system is calculated in this paper. The interference resulting from the reference satellite is calculated for mobile located in the middle of the double coverage region whereas the additive interference from next-satellite is included for mobile located in the edge of the double coverage region. The performance of the mobile's receiving signal is dependent on shadowing and the interference of the next-satellite. We can obtain an obtain an improved average bit error probability by using dual diversity over the conventional correlated receiver for similar shadowing conditions in the coverage area of the satellite channel.
Performance Analysis of Access Channel in CDMA Cellular Network
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1529~1529
The contact procedure of access channel necessary to set up the originating call has a close relation with the performance and capacity of the base station system in CDMA cellular network. This paper investigates the structure and the operation of the backward channel of IS-95 CDMA standard and explains the related system parameters. We can derive the throughput of the CDMA access channel depending on the arrivals of the access probes per access channel slot given the system parameters such as cell radius the maximum number of retransmission and the error rates of the access and paging channel. It shows that the performance in throughput is much better in the CDMA IS-95 access channel than in the slotted aloha channel. It also gives the reasonable number of the trafic channels in a cell with the given blocking probability.
Performance Analysis of Advanced MMSE Multi-User Detector for DS/CDMA systems
감두열 ; 박상규 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1540~1540
In this paper the performance of the MMSE multiuser detector is compared with the conventional detector with respect to the signal-to-noise ratio the number of users and the Nakagami parameter under AWGN as well as Nakagami fading channel. The results show that the MMSE multiuser detector is superior to the conventional detector with respect to cancelling the multiple access interference. However its drawback is the hardware's complexity. To solve this drawback the advanced MMSE multiuser detector is presented and its performance is analyzed. The number of taps in the advanced MMSE multiuser are independent of the processing gain. Thus the system engineer can choose the appropriate number of taps in the detector to achieve a optimal trade-off between the hardware complexity and the performance of system.
Peak-to-Average Power Ratio Reduction by Partial Parallel Transform in an OFDM-CDMA System
주양익 ; 이연우 ; 차균현 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1548~1548
In this paper an effective peak power reduction scheme for a downlink OFDM-CDMA system is proposed Using the partial parallel transform(PPT) structure peak-to-average power ratio(PAPR) can be reduced. The patterns of inputs of Inverse Fast Fourier Transform(IFFT) are more randomized in this structure by allotting the subcarriers to each users. At the cost of complexity we can obtain reduced PAPR and multiple access interference(MA) Computer simulations are carried out from the viewpoint of PAPR and demonstrated the improved PAPR performance
Multiplexing MPEG Video Streams Using Selective Buffering
김명균 ; 윤상호 ; 허정석 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1554~1554
On ATM network MPEG video stream is transferred using CBR or VBR services. But because the MPEG video traffic varies greatly from time to time it is very difficult to transfer the MPEG steam efficiently without loss of transmission bandwidth. Until now the study on the traffic analysis and control on a single MPEG video stream has been done by many researchers but the traffic analysis and control on a multiplexed traffic of multiple MPEG video streams has not been studied by any researcher. This paper proposes a multiplexing method to reduce the PCR and traffic variance of a multiplexed traffic of multiple MPEG video streams. By reducing the PCR of the multiplexed traffic the multiplexed VBR traffic can be transferred efficiently with less loss of transmission bandwidth
Expanding Generalized Hadamard Matrices over
by Using Generalized Hadamard Matrices over G
노종선 ; 송홍엽 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1560~1560
Over an additive abelian group G of order g and for a given positive integer λ, a generalized Hadamard matrix GF(g,λ) is defined as a gλ×gλmatrix [h(i,j)] where 1≤i≤gλ,1≤j≤gλ such that every element of G appears exactly λ times in the list h(i1-1)-h(i2.1), h(ii,2)-h(i2, 2)···h(ii,gλ)-h(i2, gλ) for any i≠j. In this paper we propose a new method of expanding a GH(gm ,λ1) =B=[Bij] over G by replacing each of its m-tuple Bij with Bij
GH(g,λ2) where m=gλ2. We may use gmλ1(not necessarily all distinct) GH(g,λ2)'s for the substitution and the resulting matrix is defined over the group of order g.
Variance Mismatched Quantization of a Generalized Gamma Source
구기일 ; 나상신 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1566~1566
This paper studies mismatched scalar quantization of a generalized gamma source by a quantizer that is optimally (in the mean square error sense) designed for another generalzied gamma source. Specifically it considers variance-mismatched quantization which occurs when the variance of the source to be quantized differs from tat of the designed-for source. The main result is the two distortion formulas derived from Bennett's integral. The first formula is an approximation expression that uses the outermost threshold of an optimum scalar quantized and the second formula in turn uses an approximation formula for this outermost threshold. Numerical results are obtained for Laplacian sources which are example of a generalized gamma source and comparisons are made between actual mismatched distoritions and the two formulas. These numerical results show that the two formulas become more accurate as the number of quantization points gets larger and the ratio of the source variance to that of the designed-for source gets bigger. For example the formulas are within 2-4% of the actual distortion for approximately 64 quantization points or more. In conclusion the proposed approximation formulas are considered to have contribution as closed formulas and for their accuracy.
New Proof of Minimum Distance for Binary Cyclic Codes with
정하봉 ; 노종선 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1576~1576
We investigated into the minimum distance of a primitive binary cyclic code C with a generator polynomial g(x)=m1(x)md(x). It is known that the necessary and sufficient condition for C to have minimum distance five is the fact that xd is an APN power function. In this paper we derived the new proof of minimum distance for the primitive binary cyclic codes with minimum distance five.
High Performance Dual-Modulus Prescaler with Low Power D-flipflops
민경철 ; 박성희 ; 김용대 ; 유영갑 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1582~1582
A dynamic D-flipflop is proposed aiming at low power and high frequency(GHz) operations. The proposed D-flipflop uses a smaller number of pmos transistors that it operates high speed in same dimensions. Also it consumes lower power than conventional approaches by a shared nmos with clock input. In order to compare the performance of the proposed D-flip-flop we perform simulation estimating power consumption and maximum operating frequency of each same dimension D-flipflop. A high speed dual-modulus prescaler employing the proposed D-flipflop. A high speed dual-modulus prescaler employing the proposed D-flipflop. A high speed dual-modulus prescaler employing the proposed D-flipflop is evaluated via the same method. The simulation results show that the proposed D-fliplflop has good performance than conventional circuits.
A CMOS Oversampling Data Recovery Circuit With the Vernier Delay Generation Technique
박준영 ; 강진구 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1590~1590
This paper describes a CMOS data recovery circuit using oversampling technique. Digital oversampling is done using a delay locked loop circuit locked to multiple clock periods. The delay locked loop circuit generates the vernier delay resolution less than the gate delay of the delay chain. The transition and non-transition counting algorithm for 4x oversampling was implemented for data recovery and verified through FPGA. The chip has been fabricated with 0.6um CMOS technology and measured results are presented.
FIR Filter Design for SSB/BPSK-DS/CDMA Using Look-Up Table
김명순 ; 김대익 ; 정진균 ; 임명섭 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1598~1598
n this paper an efficient pulse shaping filter architecture for SSB/BPSK-DS/CDMA is proposed. The filter satisfies the specifications in IS-95. The proposed architecture is based on polyphase decomposition and look-up table method. By exploiting the linear phase property of the decomposed filter coefficients the chip area required for look-up table can be reduced by half compared with the conventional methods. By Synopsys simulations it is shown that the use of the proposed method can result in reduction in the number of gates by 40%.
A Simultaneous Hardware Resource Allocation and Binding Algorithm for VLSI Design
최지영 ; 인치호 ; 김희석 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1604~1604
This paper proposes a simultaneous hardware resource allocation and binding algorithm for VLSI design. The proposed algorithm works on scheduled input graph and simultaneously allocates binds functional units interconnections and registers by considering interdependency between operations and storage elements in each control step in order to share registers and interconnections connected to functional units as much as possible. Also the register allocation is especially executes the allocation optima us-ing graph coloring techniques. Therefore the overall resource is reduced. This paper shows the effectiveness of the proposed algorithm by comparing experiments to determine number of functional unit in advance or to separate executing allocation and binding of existing system
Coverage and Capacity Analysis for the Multi-layer CDMA Macro/Indoor-Pico Cell
최승욱 ; 홍대형 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1641~1641
This paper presents an analysis of coverage and capacity for the multi-layer CDMA cellular system. The multi-layer CDMA system that shares a common frequency band consists of macrocells for outdoor users and picocells for indoor users. Though macrocells and picocells interfere with each other the capacity of the whole system can be increased, We have analyzed the effect of muual interference upon cell coverage soft handover areas and capacities. The parameters involved in the engineering of the system are discussed. The study results sow that we can control the service coverage of indoor picocells with the system parameters set properly. It is also show that the capacity of the whole system that the capacity of the whole system can be enhanced smoothly by deploying the indoor picocells within existing macrocells.
A Real-time Dynamic Storage Allocation Algorithm Supporting Various Allocation Policies
정성무 ; 유해영 ; 심재홍 ; 박승규 ; 최경희 ; 정기현 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1648~1648
his paper proposes a real-time dynamic storage allocation algorithm QSHF(quick-segregated-half-fit) that provides various memory allocation policies. that manages a free block list per each word size for memory requests of small size good(segregated)-fit policy that manages a free list per proper range size for medium size requests and half-fit policy that manages a free list per proper range size for medium size requests and half-fit policy that manages a free list per each power of 2 size for large size requests. The proposed algorithm has the time complexity O(1) and makes us able to easily estimate the worst case execution time(WCET). This paper also suggests two algorithm that finds the proper free list for the requested memory size in predictable time and if the found list is empty then finds next available non-empty free list in fixed time. In order to confirm efficiency of the proposed algorithm we simulated the memory utilization of each memory allocation policy. The simulation result showed that each policy guarantees the constant WCET regardless of memory size but they have trade-off between memory utilization and list management overhead.
Study on Improvement of UBR Traffic Performance using ABT Block Scheduling in Multicast ATM Networks
임동규 ; 박용진 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1665~1665
This paper treats the interworking of LAN-based networks like TCP over the ATM protocol stack in an ATM multicast session. Multicast connection will cause CIP since multicast group members form a connection tree by some tree methods and share the connected tree. The paper solve the CIP problem through a block-by-block transmission using ABT/IT method. ABT/IT RM cell is modified and block scheduling algorithm considering the traffic types is applied to each ATM switch using the enhanced RM cell. Block scheduling algorithm will avoid the indiscriminate discard of UBR traffic when congestion occurs and it can provide an efficient and fair service. The paper builds a block scheduler system and suggests the block scheduling algorithm for a multicast session in an ATM switch. UBR traffics arriving at the switch trough each VC is classified by the traffic type and stored at class buffer and thereafter indisciminately transmitted. When block scheduling algorithm is applied it will improve the UBR traffic performance such as end-to-end delay cell block loss ration etc. This paper evaluated the performance of block scheduling algorithm through the simulation using the C language and data structure.
CReMeS: A CORBA COmpliant Reflective Memory based Real-time Communication Service
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1675~1675
We present CReMeS a CORBA-compliant design and implementation of a new real-time communication service. It provides for efficient predictable and scalable communication between information producers and consumers. The CReMeS architecture is based on MidART's Real-Time Channel-based Reflective Memory (RT-CRM) abstraction. This architecture supports the separation of QoS specification between producer and consumer of data and employs a user-level scheduling scheme for communicating real-time tasks. These help us achieve end-to-end predictability and allows our service to scale. The CReMeS architecture provides a CORBA interface to applications and demands no changes to the ORB layer and the language mapping layer. Thus it can run on non real-time Off-The-Shelf ORBs enables applications on these ORBs to have scalable and end-to-end predictable asynchronous communication facility. In addition an application designer can select whether to use an out-of-band channel or the ORB GIOP/IIOP for data communication. This permits a trade-off between performance predictability and reliability. Experimental results demonstrate that our architecture can achieve better performance and predictability than a real-time implementation of the CORBA Even Service when the out-of-band channel is employed for data communication it delivers better predictability with comparable performance when the ORB GIOP/IIOP is used.
A QoS-based Hierarchical Routing Algotihm for TINA-based Connection Management
서승호 ; 김영탁 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1690~1690
Connection management function of the TINA which is developed by TINA-C provides network connection services such as setup modification and release of connections. The connection management function provides these services to network operators to the fault management function that provides backup-path and to the performance management function that provides load-balancing. The connection management function necessarily requires a routing algorithm to set up a new connection. In this paper we propose a new routing algorithm named QTHR (QoS and Traffic parameter based Hierarchical Routing) for TINA based connection management of ATM/B-ISDN network. And we implemented the QTHR and analyzed the performance of the QTHR.
A Study on the Development of 38 GHz Hybrid Power Amplifier Module
윤양훈 ; 김홍득 ; 권영우 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1701~1701
In this work a 38 GHz hybrid 2-stage power amplifier module using GaAs pHEMTs and waveguide to microstrip transitions has been successfully developed. A 10 mil thickness duroid substrate was use for fabrication of the power amplifier and the waveguide to microstrip transitions. The fabricated waveguide to microstrip transition showed about 1 dB insertion loss(back to back) at 32-40 GHz. The measured results of power amplifier module showed 29 dBm output power(P1.5dB), 7,2 dB associated gain and 11.2% power-added efficiency(PAE) at 36.8-38.5 GHz.
Characteristics of A Tunable OADM Using A Fiber-Optic Delay-Line Transversal Filter
윤찬호 ; 신종덕 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1707~1707
We have proposed a tunable optical ADM using a fiber-optic transversal filter which is composed of fiber couplers and metal-film coated fiber-optic tapped delay-lines with a flat spectral response in abroad range of wavelength. Simulation results show that the optical loss at the DROP and PASS wavelengths of the OADM is negligible and the wavelength tunability is 0.78㎛/ps for the unit time delay of 2 ps. In order to investigate the effects of wavelength drift of the imput optical signal on the OADM the loss at the DROP port and the crosstalks to the other ports have been calculated. The maximum bit rates have been calculated at 46.26 Gb/s for the input Gaussian pulse width of 10 ps.
A Study on Direct Decision Blind Adaptive Interference Suppression for DS-CDMA Systems
우대호 ; 변윤식 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1714~1714
In the mobile communication using DS-CDMA systems the problem of multiple user interference which reduce the performance is generated by multiple user access. In this paper to solve this problem we proposed the direct decision blind adaptive receiver with knowledge of only the desired user's spreading sequence. Simulation result present that the total user's power has equal gain The gain of signal to interference ratio for the proposed blind DD-LMS receiver has about 6[dB] than conventional receiver at additive white Gaussian noise and large gain at multipath channels. And when interference user's power has more large gain than desired user's power the gain of SIR for the proposed receiver has large value. And simulation result of bit error rate present that DD-LMS receiver has higher performance than LCCMA receiver. Thus the proposed blind DD-LMS receiver has robustness against interference of high power user and multipath channels.
The Optical Cell Compressor and Decompressor using SOA Gates and Optical Feedback Loops
김광수 ; 정광원 ; 이정렬 ; 엄진섭 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1722~1722
In this paper we proposed a new type of the Optical Cell Compressor and Decompressor which are essential modules in TDM of TDM/WDM Hybrid OPtical ATM Switch structure. This proposed structure frastically lessens hardwares for realization by using SOA gates and optical feedback loops in the process of compression and decompression. Also it is able to compress and decompress the large capacity optical pulse stream just with a few of stages cascade connected. We proved it's possibility for systematic application through 4-bit compression experiment.
FPGA Implementation of an FDTrS/DF Signal Detector for High-density DVD System
정조훈 ; 양원영 ; 조용수 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1732~1732
In this paper a fixed-delay trellis search with decision feedback (FDTrS/DF) for high-density DVD systems (4.7-15GB) is proposed and implemented with FPGA. The proposed FDTrS/DF is derived by transforming the binary tree search structure into trellis search structure implying that FDTrS/DF performs better than the signal detection techniques based on tree search structure such as FDTS/DF and SSD/DF. Advantages of FDTrS/DF are significant reductions in hardware complexity due to the unique structure of FDTrS composed of only one trellis stage requiring no traceback procedure usually implemented in the Viterbi detector. Also in this paper the FDTS/DF and SSD/DF orginally proposed for high-density magnetic recording systems are modified for the DVD system and compared with the proposed FDTrS/DF. In order to increase speed in the FPGA implementation the pipelining technique and absolute branch metric (instead of square branch metric) are applied. The proposed FDTrS/DF is shown to provide the best performance among various signal detection techniques such as PRML, DFE, FDTS/DF and SSD/DF even with a small hardware complexity.
Analysis of Transmission Performance Using Frame Domain Interleaving and Group Domain Interleaving on a Radio Encryption System
홍진근 ; 황찬식 ; 윤장홍 ; 강건우 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1744~1744
In this paper a synchronized stream cryptosystem for secure link layer communication on a radio channel is designed. We have proposed new interleaving schemes to randomize a burst error and experimented with different types of interleaving schemes. The proposed techniques of interleaving schemes are : (1) interleaving scheme based on frame(2) interleaving scheme based on group. The proposed schemes are very robust in randomizing
A Study on Channel Equalization for Asynchronous DS-CDMA Systems
민장기 ; 박노진 ; 강철호 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1760~1760
Blind Equalization Method without training sequences is proposed for channel efficiency in mobile communication system for asynchronous multi-user DS-CDMA. the risk of mis-convergence of weak-power users is increased because of small regions of convergence in case of near-far effect in CMA(Constant Modulus Algorithm) which is the simplest has high performance and widely implemented. In despite the problem a equalization using Newton method has higher performance than a conventional method in squared error and eye-pattern.
Automatic Identification of Digital Modulation Methode Using an Artification Neural Network
신용조 ; 진용옥 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1769~1769
In this paper a new method is proposed to identify a modulation method in the case of unknown digitally modulated input signals. The proposed identification method is implemented with an artificial neural network which is based on characteristic feature extracted from the instantaneous amplitude the instantaneous phase and the instantaneous frequency of the input signals. The proposed method was simulated with 9 type signals (ASK2, FSK2, FSK4, PSK2, PSK4, PSK8, QAM8, QAM16) in a noisy communication environment. The results show that the artificial neural network can accurately recognize all kinds of patterns
Chirp Stitching Technique for Wideband Signals of the Spaceborne High Resolution Synthetic Aperture Radar
권오주 ; 가민호 ; 하영호 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1777~1777
In this paper we suggested the chirp stitching algorithm and transmitter/receiver channel to a spaceborne high resolution SAR which enables wideband signal generation and processing with minimum hardware requirement. The transmitter channel generates two sub-band signals and then generate a wideband signal using chirp stitching algorithm and the receiver channel divides a wideband signal into two sub-band signals in order to overcome the high speed data handling capability of this spaceborne systems. We generated and processed a 100 MHz wideband signal evaluated the performance and verified the feasibility of the application of this chirp stitching algorithm and transmitter/receiver channel to spaceborne high resoultion SAR.
Multi-rate Non-recursive Architecture for Cascaded Integrator-Comb Decimation Filters with an Arbitrary Factor
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1785~1785
In this paper multi-rate non-recursive architecture for CIC(Cascaded Integrator-Comb) decimation filters with an arbitrary factor is proposed. The CIC filters are widely used in high speed wireless communication systems since they have multiplier-less and multi-rate low-power structure. Even conventional non-recursive CIC structure is multi-rate this architecture can be structured only in case of M-th power-of-two decimation factor. This paper proposes that muli-rate non-recursive CIC architecture can be structured with an any decimation factor of product form. Power consumption of the proposed architecture is compared with that of the conventional non-recursion architecture.
A Zipper-based VDSL Modem with an Efficient Cyclic Extension
위정욱 ; 양원영 ; 유영환 ; 백종호 ; 조진웅 ; 조용수 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1793~1793
In this paper we propose an efficient implementation technique for cyclic extension in VDSL(Very High bit-rate Digital Subscriber Line) systems using Zipper duplexing and analyze its performances under typical telephone channel environments. In Zipper-based VDSL systems each DMT(discrete-multitone) block is appended by both cyclic prefix(CP) and cyclic suffix(CS). The CP is inserted to prevent both intersymbol interference (ISI) and iterchannel interference (ICI) while the CS is appended to ensure orthogonality between the upstream and downstream carriers thus preventing near-end crosstalk (NEXT). However in order to implement the CP in the transmitter side of the VDSL system an additional hardware is required to append the latter part of each DMT symbol to the beginning of the DMT symbol. In this paper we propose a VDSL system with Zipper duplexing using only CS to reduce hardware complexity (memory and processing delay) required for implementation of CP. It is shown by computer simulation that the proposed approach has the same capacity under typical channel environments as the previous Zipper-based VDSL system using both CP and CS. even with a significantly lower hardware complexity.
ISAR Motion COmpensation based on Accumulation and Limitation of Consecutive Radar Returns
서동신 ; Guolin Wang ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1803~1803
A new motion compensation method for ISAR is presented in this paper. It employs amplitude limiting and integration of consecutive range profiles to improve the range and phase alignment accuracy and to alter the propagation properties of compensation errors. These allow the image quality to be significantly improved. It is shown from the imaging results that the new motion compensation algorithm can get images of targets in field situations with much better quality than the traditional cross-correlation algorithm
Selective Multiresolution Motion Estimation Using Half-pixel Accuracy and Characteristics of Motion Vectors
권성근 ; 이종원 ; 반성원 ; 이승진 ; 하인성 ; 정원식 ; 이건일 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1813~1813
In this paper we proposed an efficient multiresolution motion estimation(MRME) algorithm using half-pixel accuracy motion estimation (HPAME) and characteristics of motion vectors in the baseband. Conventional MRME method needs exact motion vectors in the baseband because those are used as initial motion vectors in higher frequency subbands. Therefore the proposed method uses HPAME to estimate the motion vectors exactly in the baseband. Based on the characteristics of these motion vectors the motion vectors in the higher frequency subbands are selectively estimated. That is motion vectors in the higher frequency subbands are estimated only for the blocks which have the half-pixel accuracy motion vectors in the baseband. In the proposed method by using HPAME in the baseband and selective motion estimation in the higher frequency subbands we can obtain reconstructed image with the similar quality with the conventional method though we reduce the computational complexity and the bit rate considerably.
Real-Time Stereo Object Tracking System using Area-based SAD Algorithm and Optical BPEJTC
이재수 ; 서춘원 ; 김은수 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1821~1821
In this paper we propose a new adaptive stereo object tracking system that can extract the object from the complex background and foreground noises by using the image-based SAD algorithm and control the convergence angle and pan/tilt of cameras by using optical BPEJTC. From the experimental results the proposed stereo tracking system is found to track the object adaptively under the circumstance of complex and changing background noises and the possibility of real-time implementation of the proposed system by using the optical system is also suggested.
Edge Enhanced Error Diffusion based on Gradient Shaping of Original Image
강태하 ; 황병원 ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 10, 2000, Pages 1832~1832
The error diffusion algorithm is good for reproducing continuous images to binary images. However the reproduction of edge characteristics is weak in power spectrum an analysis of display error. In this paper an edge enhanced error diffusion method is proposed to improve the edge characteristic enhancement. Spatial gradient information in original image is adapted for edge enhance in threshold modulation of error diffusion. First the horizontal and vertical second order differential values are obtained from the gradient of peripheral pixels(3x3) in original image. second weighting function is composed by function including absolute value and sign of second order differential values. The proposed method presents a good visual results which edge characteristics is enhanced. The performance of the proposed method is compared with that of the conventional edge enhanced error diffusion by measuring the edge correlation and the local average accordance over a range of viewing distances and the RAPSD of display error.