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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of IKEEE
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Institude of Korean Electrical and Electronics Engineers
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Volume 5, Issue 2 - Dec 2001
Volume 5, Issue 1 - Jul 2001
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Optimization of Data Recovery using Non-Linear Equalizer in Cellular Mobile Channel
Choi, Sang-Ho ; Ho, Kwang-Chun ; Kim, Yung-Kwon ;
Journal of IKEEE, volume 5, issue 1, 2001, Pages 1~7
In this paper, we have investigated the CDMA(Code Division Multiple Access) Cellular System with non-linear equalizer in reverse link channel. In general, due to unknown characteristics of channel in the wireless communication, the distribution of the observables cannot be specified by a finite set of parameters; instead, we partitioned the m-dimensional sample space Into a finite number of disjointed regions by using quantiles and a vector quantizer based on training samples. The algorithm proposed is based on a piecewise approximation to regression function based on quantiles and conditional partition moments which are estimated by Robbins Monro Stochastic Approximation (RMSA) algorithm. The resulting equalizers and detectors are robust in the sense that they are insensitive to variations in noise distributions. The main idea is that the robust equalizers and robust partition detectors yield better performance in equiprobably partitioned subspace of observations than the conventional equalizer in unpartitioned observation space under any condition. And also, we apply this idea to the CDMA system and analyze the BER performance.
The Header Compression Scheme for Real-Time Multimedia Service Data in All IP Network
Choi, Sang-Ho ; Ho, Kwang-Chun ; Kim, Yung-Kwon ;
Journal of IKEEE, volume 5, issue 1, 2001, Pages 8~15
This paper remarks IETF based requirements for IP/UDP/RTP header compression issued in 3GPP2 All IP Ad Hoc Meeting and protocol stacks of the next generation mobile station. All IP Network, for real time application such as Voice over IP (VoIP) multimedia services based on 3GPP2 3G cdma2000. Frames for various protocols expected in the All IP network Mobile Station (MS) are explained with several figures including the bit-for-bit notation of header format based on IETF draft of Robust Header Compression Working Group (ROHC). Especially, this paper includes problems of IS-707 Radio Link Protocol (RLP) for header compression which will be expected to modify in All IP network MS's medium access layer to accommodate real time packet data service. And also, since PPP has also many problems in header compression and mobility aspects in MS protocol stacks for 3G cdma2000 packet data network based on Mobile IP (PN-4286), we introduce the problem of solution for header compression of PPP. Finally. we suggest the guidelines for All IP network MS header compression about expected protocol stacks, radio resource efficiency and performance.
Noise Reduction using Passive and Active Noise Control in the Closed Area
Cho Byung-Mo ;
Journal of IKEEE, volume 5, issue 1, 2001, Pages 16~23
Passive noise reduction is a classical approach to attenuate industrial noise, and an active noise cancellation has several advantages over the passive noise cancellation. The active noise reduction system offers a better low frequency performance with a smaller and lighter system. This paper presents a simple active closed loop control system which consists of an controller for inverting and compensating the phase delay, a microphone for picking up the external noise, and a loudspeaker for radiating the acoustic out of phase signal to reduce the external noise, and external noise can be reduced after compensating the phase difference to be
in the frequency of maximum value in the amplitude response. The noise of the phase delay covered from
tends to be reduced in the active noise control system and it is possible to obtain a noise cancelling of up to approximately 20[dB] at the ears in the enclosurer.
A High Speed IP Address Lookup using Pipelined CAM Architecture(PICAM)
Ahn, Hee-Il ; Cho, Tae-Won ;
Journal of IKEEE, volume 5, issue 1, 2001, Pages 24~34
IP address lookup is a major bottleneck of IP packet processing in high speed router. Existing IP lookup methods are focused only on lookup throughput without considering lookup table update. So their slow update can lead to lookup blocking or wrong routing decision based on obsolete routes. Especially existing IP lookup methods based on CAM(content addressable memory) have slow update of O(n) cycles in spite of their high throughput and low area complexity In this paper we proposes a new IP address lookup method based on pipelined CAM architecture(PICAM) with fast update of O(1) cycle of lookup table and high throughput and low area complexity.
Traffic Analysis of a CAN-based Control System
Kim, Dae-Won ;
Journal of IKEEE, volume 5, issue 1, 2001, Pages 35~42
This paper deals with an architecture of network-based control system using the CAN(Controller Area Network) protocol and its traffic analysis. It is difficult to determine an optimal network-based control architecture for a specific AGV(Autonomous Guided Vehicle) system with a manipulator arm. The fixed number of periodic messages to be occurred is pre-defined in the system. To determine whether the proposed system architecture is effective or not, we perform traffic analysis for the real-time communication of all messages. Through simulations, the range of transmission speed is found satisfying required conditions and the permissible number of additional sensors is investigated for improving the system performance, when the sampling periods of analog sensors are determined under fixed condition that the transmission speed is over 500Kbps.
A New Test Algorithm for Bit-Line Sensitive Faults in High-Density Memories
Kang, Dong-Chual ; Cho, Sang-Bock ;
Journal of IKEEE, volume 5, issue 1, 2001, Pages 43~51
As the density of memories increases, unwanted interference between cells and coupling noise between bit-lines are increased. And testing high-density memories for a high degree of fault coverage can require either a relatively large number of test vectors or a significant amount of additional test circuitry. So far, conventional test algorithms have focused on faults between neighborhood cells, not neighborhood bit-lines. In this paper, a new test algorithm for neighborhood bit-line sensitive faults (NBLSFs) based on the NPSFs(Neighborhood Pattern Sensitive Faults) is proposed. And the proposed algorithm does not require any additional circuit. Instead of the conventional five-cell or nine-cell physical neighborhood layouts to test memory cells, a three-cell layout which is minimum size for NBLSFs detection is used. Furthermore, to consider faults by maximum coupling noise by neighborhood bit-lines, we added refresh operation after write operation in the test procedure(i.e.,
). Also, we show that the proposed algorithm can detect stuck-at faults, transition faults, coupling faults, conventional pattern sensitive faults, and neighborhood bit-line sensitive faults.
A 3.3V/5V Low Power TTL-to-CMOS Input Buffer Controlled by Internal Activation Clock Pulse
Bae, Hyo-Kwan ; Ryu, Beom-Seon ; Cho, Tae-Won ;
Journal of IKEEE, volume 5, issue 1, 2001, Pages 52~58
This paper describes a TTL-to-CMOS input buffer of an SRAM which dissipates a small operating power dissipation. The input buffer utilizes a transistor structure with latch circuit controlled by a internal activation clock pulse. During the low state of that pulse, input buffer is disabled to eliminate dc current. Otherwise, the input buffer operates normally. Simulation results showed that the power-delay product of the purposed input buffer is reduced by 33.7% per one input.
Mobile Ad Hoc Routing Protocol Supporting Unidirectional Links
Lee, Kwang-Bae ; Kim, Hyun-Ug ; Jung, Kun-Won ;
Journal of IKEEE, volume 5, issue 1, 2001, Pages 59~66
In this paper, we propose a dynamic source routing protocol supporting asymmetric paths for mobile Ad Hoc networks that contain unidirectional links. At present, the existing dynamic source routing protocol supports only symmetric paths that consist of bidirectional links for routing. However, in fact, there can exist unidirectional links due to asymmetric property of mobile terminals or current wireless environment. Thus, we implement a mobile Ad Hoc routing protocol supporting unidirectional links, which is fit for more general wireless environment. Especially, the proposed protocol uses an improved multipath maintenance method in order to perform rapid route reconfiguration when route error due to mobility is detected. For performance evaluation, we consider the following factors: average route discovery time and average data reception rate. In order to obtain the factors of the performance evaluation, we did simulation for 900 seconds in the step of 100 seconds with the following scenarios: usage of route cache in intermediate nodes on route path, and different mobility/connection patterns.
An Enhanced DSR Routing Protocol for Mobile Ad Hoc Networks supporting Bidirectional Links
Lee, Kwang-Bae ; Kim, Hyun-Ug ; Kwag, Seung-Ug ;
Journal of IKEEE, volume 5, issue 1, 2001, Pages 67~74
In this paper, we propose a new method to improve tile processing of route recovery of the existing DSR algorithm on detection of route error. In mobile ad hoc networks, mobile nodes themselves have routing capability. Thus, a well-defined routing protocol is required for route set-up between two mobile nodes. However, the existing DSR routing protocol has problem with dropping of packets due to the recovery delay when a route error occurs. In order to alleviate tile problem, we propose an enhanced DSR protocol to reduce the route error recovery tine and evaluate the protocol through simulation. As tile result of evaluation, we found the proposed DSR protocol provided about 4 to 30 times faster route error recovery time according to the test scenario than the existing DSR protocol.
Development of an Automatic Transverse and Longitudinal Road Profile Measurement System
Eom, Jung-Hyun ; Seo, Dong-Sun ; Huh, Woong ; Roo, Myong-Chan ; Kim, Joon-Bum ;
Journal of IKEEE, volume 5, issue 1, 2001, Pages 75~84
The reliable data relating to the condition of road surface is of increasing importance to deliver the road condition to driver and road management authority. This paper describes the development of a new high-speed. automatic, road data collection system, which collects the longitudinal road data with
interval covering full width of the road at 100km/h speed. The system calculates the international roughness index (IRI) from the collected data and displays the IRI and road profile data on the screen. To develope the system, we implement an optical range finder, advanced distance and motion detectors, and signal processing and display modules. The measurement accuracy of the system at 70km/h operation speed shows
in the IRI for the standard road. To confirm the performance of the developed system, we also measure the IRI of a deployed highway road and compare the results with a conventional system and human eye measurement results.
Envelope Correlation of Wideband Signals in Nakagami-Rice Fading Channel
Park, Byeong-Hoon ;
Journal of IKEEE, volume 5, issue 1, 2001, Pages 85~90
In this paper, we analyzed the envelope correlation of wideband signals modulated on two separate subcarriers in a Nakagami-Rice fading channel with exponential power delay profile. The results show that the envelope correlation of resolvable paths is implicated by the ratio of the specular wave power to the mean multipath power as well as the signal bandwidth and the rms delay spread of the multipath waves.
Spectral Domain Analysis of Resonant Frequency in Rectangular Microstrip Patch Antenna on Uniaxial Substrates with Airgap and Superstrate
Lee, Sang-Mok ; Yoon, Joong-Han ; Kim, Heung-Soo ;
Journal of IKEEE, volume 5, issue 1, 2001, Pages 91~99
Spectral domain of resonant frequency rectangular microstrip patch antenna on anisotropic substrates and superstrate with airgap are analyzed. First, we derive dyadic Green function for selected anisotropic material by constitutive relation and then formulate integral equations of electric fields using Fourier transform in space region. Using Galerkin's moment method, we discretize the electric field integral equations Into the matrix form and select sinusoidal functions as basis functions. We verify the validity of numerical results and compare the results with existing ones in showing a good agreement between them. The resonant frequencies in the variation of air gap, patch length and permittivity of superstrate anisotrpy ratio of anisotrpic superstrate are presented and analyzed.
A Study on Efficient Cell Queueing and Scheduling Algorithms for Multimedia Support in ATM Switches
Park, Jin-Su ; Lee, Sung-Won ; Kim, Young-Beom ;
Journal of IKEEE, volume 5, issue 1, 2001, Pages 100~110
In this paper, we investigated several buffer management schemes for the design of shared-memory type ATM switches, which can enhance the utilization of switch resources and can support quality-of-service (QoS) functionalities. Our results show that dynamic threshold (DT) scheme demonstrate a moderate degree of robustness close to pushout(PO) scheme, which is known to be impractical in the perspective of hardware implementation, under various traffic conditions such as traffic loads, burstyness of incoming traffic, and load non-uniformity across output ports. Next, we considered buffer management strategies to support QoS functions, which utilize parameter values obtained via connection admission control (CAC) procedures to set tile threshold values. Through simulations, we showed that the buffer management schemes adopted behave well in the sense that they can protect regulated traffic from unregulated cell traffic in allocating buffer space. In particular, it was observed that dynamic partitioning is superior in terms of QoS support than virtual partitioning.
On the Performance Enhancements of VC Merging-capable Scheduler for MPLS Routers by Sequence Skipping Method
Baek, Seung-Chan ; Park, Do-Yong ; Kim, Young-Beom ;
Journal of IKEEE, volume 5, issue 1, 2001, Pages 111~120
VC merging involves distinguishing cells from an identical merged VC label. Various approaches have been proposed to help this identification process. However, most of them incur additional buffering, protocol overhead and/or variable delay. They make the provision of QoS difficult to achieve. So it was proposed a merge capable scheduler to support VC-merging (VCMS). However, in situations where all VCs are to be merged or the incoming traffic load is very low, it could happen that there are not enough non-merging cells to snoop. In this situation the scheduler uses special control cells to fill the empty time slots out. Too many control cells can cause high cell loss ratio and an additional packet transfer delay. To overcome the drawbacks, we propose a Sequence Skipping(SS) method where the sequencers skip the empty queues and insert SS cells. We show SS method is suitable for VC-merging and can reduce the cell loss ratio and the mean packet transfer delay through simulations.