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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
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Performance Analysis of 16 star-QAM with Diversity Reception in Microcell Systems
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 1A, 2000, Pages 1~9
This paper presents the error performance of 16 star-QAM with diversity reception in microcell systems in the presence of additive white Gaussian noise(AWGN) and cochannel interference. The differential detection of 16 star-QAM is split into phase detection and amplitude detection. This technique can reduce the degradation of error performance which is due to fading and the complexity of receiver. Diversity reception is proposed to improve the degradation of error performance due to fading. Equal gain and maximal ratio combinings were adopted for the phase detection and the amplitude detection, respectively. The performance of 16 star-QAM was evaluated for various of Rician factor K, maximum Doppler frequency
, signal to cochannel interference ratio and diversity branch L.
The Correlation Parameters and the Optimization of a PN Sequence Phase for Variable Spreading Gain (VSG) Multi-Rate DS/CDMA System
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 1A, 2000, Pages 10~17
In this paper, we evaluate the correlation properties and the optimization of PN sequence phase for multi-media DS/CDMA system with variable spreading gain (VSG) scheme. In multi-media multi-rate DS/CDMA systems, the optimization of PN sequence phase is not a tractable problem, since the sequences should be optimized against both sequences of the same length and other sequences with different length. Hence, we verify the correlation properties of PN sequence phase in multi-rate system environment and furthermore, we propose the new phase criterion, MIN-AIP (minimum-average interference parameter), to minimize the bit error rate (BER). As the results of performance evaluations, it is shown that the performance of MIN-AIP criteria gives the best results.
An Improved Channel Management Technique in the Hierarchical Cellular Radio Systems
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 1A, 2000, Pages 18~26
Yeung suggested efficient channel management technique suitable for the mobility model in the hierachical cellular system. It improved the existing channel allocation techniques by additionally considering the user’s mobility, allocating the channel of microcell to low-speed mobiles, and the channels of macrocell to high-speed mobiles. In this paper, we have suggested new channel management technique, which is directly compared with those of Yeung’s system and existing model. Blocking probabilities for each model are found through the queuing analysis and we have shown that our proposed system outperforms the both.
The Performance of a Non-Decision Directed Clock Recovery Circuit for 256 QAM Demodulator
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 1A, 2000, Pages 27~33
Gardner’s algorithm is one of the useful algorithm for NDD(Non-Decision Directed) symbol synchronization in PAM communications. But the algorithm has a weak point such as pattern noises increasing in multi-level PAM. To insert a pre-filter in the algorithm is able to reduce timing jitter and pattern noise. In this paper, we analyze statistical properties of NDD algorithm to find an optimal parameter of the pre-filter for improving timing jitter and PLL locking. As a simulation result, optimum value of pre-filter parameter,
, is 0.3 and 0.5 at the roll off factor of the channel,
, is 0.5 and 1.0, respectively. Optimum parameters of the pre-filter for clock synchronization of all-digital 256-QAM demodulator is shown in the results.
Diversity Combining Techniques for DPSK Signals in Nakagami Fading Channels
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 1A, 2000, Pages 34~42
In this paper, the closed form expression for the average bit error probability(BER) is derived for diversity reception using an L-branch maximal ratio combining(MRC) system which has same fading index and different fading index. Also, the BER to have same average power and Nakagami m-distribution for a generalized selection combining(SC) is derived, whereby the signal with the largest amplitude is selected from the original diversity branches in the channel, the order statistics is applied. Especially, when L is 1 in a selective diversity, the derived expression leads to that of DPSK in which SC is not applied in Nakagami fading. Changing the diversity branch L and fading index m, we compare the performance of MRC and SC.
Performance Analysis of Hybrid Concatenated Convolutional Codes over AWGN and Rayleigh/Rician Fading Channels
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 1A, 2000, Pages 43~47
In regions of low signal-to-noise ratio (SNR), performance analysis uses simulations of hybrid concatenated coding systems. However, for higher SNR regions beyond simulation capabilities, average upper bounds to bit error rate (BER) and word error rate (WER) are used. In , all weight enumerating functions are needed to obtain average bounds. In this paper, we use RSC as constituent codes, by using effective free distances instead of WEF, we derive average BER and WER bounds of hybrid concatenated convolutional codes (HCCC) and analyze the BER and WER over AWGN and Rayleigh/Rician fading channels.
A Study on an Improved LBG Algorithm to Design the Code Book of VQ
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 1A, 2000, Pages 48~55
In this paper, an assumption to design a quantizer, is proposed that if one small region of a probability density function is represented larger probability and bigger total error than another neighbour region, then the quantizer is not optimal. It is tested when the probability functions are Gaussian, Laplacian and uniform density function by the computer simulations. A new LBG algorithm which originates from this assumption in addition to LBG algorithm, is designed for the vector quantizer. The new LBG algorithm presents better performance than the original LBG algorithm in the average error and the variance of the error.
Design and Analysis of Distributed-Network-Based ATM Switch : Weaved GSN
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 1A, 2000, Pages 56~63
In this paper, we design new high performance ATM switch architectures based on a Generalized Shuffle network(GSN). The GSN is a distributed network topology with the number of nodes in O(N). To improve the throughput of the switch, a layering strategy called Weaved GSN(WGSN). WGSN has an additional connection links between switching elements which locate in the same position of adjacent GSNs. The analysis and simulation are performed under uniform and full load conditions, and the results show that the proposed switch has better throughput and cell loss performance when compared with other banyan-based switch architectures known so far.
Power Spectral Analysis-Based QoS Evaluation of VBR Video and Its Application to Fair-Pricing Scheme
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 1A, 2000, Pages 64~73
Since so many potentials of services, applications, marketing and regulation, it is difficult to decide the fair pricing scheme of network services. However, these considerations are not particular to the operation of a communications network, which is closely related to technological constraints for QoS guarantee. In this paper, the power spectral analysis of MPEG video based on the P-MMBBP model is discussed in the manner of the QoS degradation to the packet delay. As a consequence of the QoS-degradation, a new fair-pricing scheme with the discount factor is proposed. As a result, the proposed scheme shows good characteristics to guarantee the fairness of the charging in the Internet wide-area network
Performance Analysis of the fairmess MAC protocol under the CATV/LAN network
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 1A, 2000, Pages 74~80
In this paper, we proposed the MAC protocol and analyzed the performance for CATV/LAN network which was based upon HFC(hybrid optic coaxial) increased abruptly as alternative method of high speed network. Upstream channel which analyzed very deeply for CATV/LAN network have the preferential access property depending upon that position and unidirectional property. To solve this fairness problem, we propose the CSMA-CD/U/P protocol that transm it as
probability although data packets is immediately transmitted when it was occurred. As the analytic result and simulation, we obtained
value and its average delay time. Also, we get its variance value and queue length distribution. The mean delay time and queue length increase as the load and number of stations increase in the CATV/LAN network
Performance Analysis of the prioritized MAC protocol under the CATV/LAN network
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 1A, 2000, Pages 81~89
In this paper, we analyzed the performance for CATV/LAN added priority problem. Upstrea nm channel which analyzed very deeply for CATV/LAN network have the preferential access property depending upon that positionand unidirectional property. To solve that fairness problem and priority, we propose the CSMA-CD/U/P-P protocolthat transmit as P1 probability if data packets happen. We assumed 2-Class priority(high, low). As the analyticresult and simulation, we obtained P1, value and its average delay time under priority problem assumed twoscenarios. Also, we get its variance value and queue length. Especially, the mean delay time increases nearer thanposition from H/E
Distributed Hierarchical Location Placement of Core Nodes in the OCBT Multicast Protocol
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 1A, 2000, Pages 90~95
In the Ordered Core Based Tree(OCBT) protocol, a core location is the most important feature to affect the performance. In this paper, the location placement of multiple level cores is studied. The proposed algorithm isthat each node in the network evaluates a sum of shortest path costs from all the other nodes and the entirenetwork is divided into a hierarchy region to have 3-logical level(Small, Medium, Large). The node to have thelowest cost in each S-Region is decided to be a core node. Then, the core nodes in the each S-Region evaluatea sum of shortest path costs from all the other core nodes in the same M-Region. The core node to have thelowest cost is decided to be the upper level core node. Similarly the highest level core node is decided in theL-Region. The proposed algoritthm is compared with conventional two methods to put the core nodes in thenetwork One is the random method to put the core nodes randomly. The other is the center method to locatethe core node at the nearest node from the center of each S-Region and then to locate the highest level corenode at the nearest core node from the center of the entire network. Extensive simulations are performed in theview of mean tree cost and join latency. Simulation results show that the proposed algorithm has betterperformance than random method or center method.
A WATM MAC Protocol for the Efficient Transmission of Voice Traffic in the Multimedia Environment
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 1A, 2000, Pages 96~103
The voice traffic is one of the most important real-time objects in WATM(Wireless Asynchronous Transfer Mode) networks. In this paper, we propose a new MAC(Medium Access'Control) protocol for the efficienttransmission of voice traffic over WATM networks in the multimedia environment and compare the performanceto existing similar protocols. The new protocol separates the reservation slot period for voice and that for data toguarantee some level of QoS(Quality of Service) in voice traffic. This is denoted by a slot assignment functiondepending on the frame size. According to the characteristics of voice traffic which is repeatedly in silent states,the protocol allocates voice reservation request slots dynamically with respect to the number of silent(off state)voice sources and also sends the first block of talkspurt restarted after silent period with a reservation requestslot to reduce the access delay.The simulation results show that the proposed protocol has better performance than Slotted Aloha in bandwidthefficiency, and can serve a certain level of QoS by the given slot assignment function even when the number ofvoice terminals varies dynamically. This means we can observe that the new MAC protocol is much better thanthe NC-PRMA(None Collision-Packet Reservation Multiple Access) protocol.
Design and Analysis of Reliable Multicast Protocol using Meta-Groups
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 1A, 2000, Pages 104~113
In this paper, we propose a protocol that makes use of a concept of a meta-group based on propagation trees to deal with duplicated members of the same multicast group. It is shown that, if multicast tree is composed ofthese meta-groups, the depth of the tree can be shortened and the ordering of the multicast that communicatesbetween multiple senders and receivers can be easier. In the protocol, we assign a Designated Manager(DM) toeach meta-group and make each DM do the role of the representative receiver of the meta group. In this Paper,the DM's are supposed to handle ACK and retransmission for the members in the same meta group. Hence, theDM's distribute the ACK from senders, and they can reduce the burden of senders by shortening commit delaytime. We also show, through a simulation analysis, that the new multicast protocol outperforms the existing onesnot only in message costs but also in commit delay times.
A Reserved Band-Based Probabilistic Cell Scheduling Algorithm for Input Buffered ATM Switches
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 1A, 2000, Pages 114~121
The problem of an input-buffered switch is the HOL(head-of-line) blocking which limits the maximum throughput but it is easy to implement in hardware. However, HOL blocking can be eliminated using aVOQ(virtual-output-queueing) technique. 0 this paper, we propose a new cell-scheduling algorithm for aninput-buffered ATM switch. The proposed algorithm, called PPIM(Probabilistic Parallel Iterative Matching), imposesa weight to every request based on the reserved bandwidth. It is shown that the input-buffered ATM switch withthe proposed PPIM algorithm not only provides high throughput and low delay but it also reduces the jitter,compared with the existing WPIM(Weighted PIM),
An Effective Cell Scheduling Algorithm for Input Queueing ATM Switch
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 1A, 2000, Pages 122~131
In this paper, we propose a cell scheduling algorithm for input queueing ATM switch. The input queueing architecture is attractive for building an ultra-high speed ATM (Asynchronous Transfer Mode) switch. We proposea WMUCS (Weighted Matrix Unit Cell Scheduler) based on the MUCS which resolves HOL blocking and outputport contention. The MUCS algorithm selects an optimal set of entries as winning cells from traffic matrix (weightmatrix). Our WMUCS differs from the MUCS in generating weight matrices. This change solves the starvationproblem and it reduces the cell loss variance. The performance of the proposed algorithm is evaluated by thesimulation program written in C++. The simulation results show that the maximum throughput, the average celldelay, and the cell loss rate are significantly improved. We can see that the performance of WMUCS is excellentand the cost-effective implementation of the ATM switch using proposed cell scheduling algorithm.
An Efficient MAC Protocol for Supporting Multimedia Services in APON
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 1A, 2000, Pages 132~141
In this paper, we proposed the MAC protocol of APON supporting multi-class traffic such as CBBUVBR, ABR, UBR, to guarantee the required QoS of each service. For this, we analyze the performance of variousrequest mechanisms and employee the different request mechanism for each traffic classes. Upstream anddownstream frame structures to minimize transmission overhead are proposed based on our request mechanism.The proposed MAC protocol applies the different priority to permit distribution process. CBBWBR traffic, withthe stringent requirements on CDV or delay, is allocated prior to any other class. ABR traffic, which hasnon-strict CDV or delay criteria, uses flexibly the available bandwidth but ensures a minimum cell rate (MCR).UBR traffic is allocated with lowest priority for the remaining capacity. The performance of proposed protocol isevaluated in terms of transfer delay and 1-point CDV with various offered load. The result of simulation showsthat the proposed protocol guarantees the required QoS of the corresponding category, while making use of theavailable resources in both an efficient and dynamical way.
A New Policing Method for Markovian Traffic Descriptors of VBR MPEG Video Sources over ATM Networks
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 1A, 2000, Pages 142~155
In this paper, we propose an efficient policing mechanism for Markov model-based traffic descriptors of VBR MPEG video traffic. A VBR video sequence is described by a set of traffic descriptors using a scene-basedMarkov model to the network for the effective resource allocation and accurate QoS prediction. The networkmonitors the input traffic from the source using a proposed new policing method. for policing the steady statetransition probability of scene states, we define two representative monitoring parameters (mean holding andrecurrence time) for each state. For frame level cell rate policing of each scene state, accumulated average cellrates for the frame types are compared with the model parameters. We propose an exponential bounding functionto accommodate dynanic behaviors during the transient period. Our simulation results show that the proposedpolicing mechanism for Markovian traffic descriptors monitors the sophisticated traffic such as MPEG videoeffectively and well protects network resources from the nalicious or misbehaved traffic.
A RFI Cancellation Technique for DMT-based VDSL Systems
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 1A, 2000, Pages 156~166
In discrete multi-tone (DMT)-based very high bit-rate digital subscriber line (VDSL) systems, the ingressed RFI (Radio Frequency Interference) accompanied by transmitted signal at the receiver is known to cause the spectralleakage by the finite-point FFT, resulting in significant performance degradation.0 this paper, we propose a RFIcancellation technique which can compensate the ingressed RFI efficiently, especially for a high data-rate VDSLsystem. The proposed technique compensates the performance degradation of e VDSL system due to RFI byusing a time-domain RFI canceller whose coefficients are obtained from the estimated center frequency of RFI inthe frequency domain under the assumption that the ingressed RFI is a narrow-band signal compared to VDSLsampling frequency. The proposed technique requires no training symbol and convergence period, and worksproperly even when spectral shape of the ingressed RFI is unknown or arbitrary. Feasibility of the proposedtechnique is demonstrated via a computer simulation by comparing its performance with the performance of theprevious RFI cancellation technique.
Time-domain Equalization Algorithm for a DMT-based xDSL Modem
Kim, Jae-Gwon ; Yang, Won-Yeong ; Jeong, Man-Yeong ; Jo, Yong-Su ; Baek, Jong-Ho ; Yu, Yeong-Hwan ; Song, Hyeong-Gyu ;
The Journal of Korean Institute of Communications and Information Sciences, volume 25, issue 1A, 2000, Pages 167~177
In this paper, a new algorithm to design a time-domain equalizer (TEQ) for an xDSL system employing the discrete multitone (DMT) modulation is proposed. The proposed algorithm, derived by neglecting the terms whichdo not affect the performance of a DMT system in ARMA modeling, is shown to have similar performance tothe previous TEQ algorithms such as matrix inverse algorithm, fast algorithm, iterative algorithm, and inversepower method, even with the significantly lower computational complexity. In addition, since the proposedalgorithm requires only the received signal, the information on the channel impulse response or training sequenceis not needed. It is also shown that for the case where bridged tap is not included, the number of TEQ tapsrequired can be reduced to half(from 16 to 8) without affecting the overall performance. The performances of theproposed and previous TEQ algorithms are compared by applying them to ADSL environment.