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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 & Issues
Volume 11, Issue 4 - Dec 2007
Volume 11, Issue 3 - Sep 2007
Volume 11, Issue 2 - Jun 2007
Volume 11, Issue 1 - Mar 2007
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Dataline Redundancy Circuit Using Simple Shift Logic Circuit for Dual-Port 1T-SRAM Embedded in Display ICs
Kwon, O-Sam ; Min, Kyeong-Sik ;
Journal of IKEEE, volume 11, issue 4, 2007, Pages 129~136
In this paper, a simple but effective Dataline Redundancy Circuit (DRC) is proposed for a dual-port 1T-SRAM embedded in Display ICs. The DRC designed in the dual-port
-bit 1T-SRAM is verified in a 0.18-um CMOS 1T-SRAM process. In the DRC, because its control logic circuit can be implemented by a simple Shift Logic Circuit (SLC) with only an inverter and a NAND that is much simpler than the conventional, it can be placed in a pitch as narrow as a bit line pair. Moreover, an improved version of the SLC is also proposed to reduce its worst-case delay from 12.3ns to 5.9ns by 52%. By doing so, the timing overhead of the DRC can be hidden under the row cycle time because switching of the datalines can be done between the times of the word line setup and the sense amplifier setup. The area overhead of the DRC is estimated about 7.6% in this paper.
The study on target tracking filter using interacting multiple model for tracking maneuvering target
Kim, Seung-Woo ;
Journal of IKEEE, volume 11, issue 4, 2007, Pages 137~144
Fire Control System(FCS) errors can be classified as hardware errors and software errors, and one of the software errors is from target tracking filter which estimates target's location, velocity, acceleration, and so on. It affects function of ballistic calculation equipment significantly. For gun to form predicted hitting point accurately and enhance hitting rate, we need status information of target's future location. Target tracking filter algorithms consist of Single Singer Model, Fixed Gain filter algorithm, IMM, PBIMM and so on. This paper will design IMM tracking filer, which is going to be! applied to domestic warship. Target tracking filter using CV model, Song model and CRT model for IMM tracking filter is made, and tracking ability is analyzed through Monte-Carlo simulation.
A Study for Frequency Characteristics of Solenoid-Type RF Chip Inductors
Kim, Jae-Wook ;
Journal of IKEEE, volume 11, issue 4, 2007, Pages 145~151
In this work, small-size, high-performance solenoid-type RF chip inductors utilizing a low-loss
core material were investigated. The size of the chip inductors fabricated in this work were
and copper (Cu) wire with
diameter was used as the coils. High frequency characteristics of the inductance, quality factor, and impedance of developed inductors were measured using an RF Impedance/Material Analyzer (HP4291B with HP16193A test fixture). It was observed that the developed inductors with the number of turns of 7 have the inductance of 13 to 100nH and exhibit the self-resonant frequency (SRF) of 6.4 to 1.1GHz. The SRF of inductors decreases with increasing the inductance and the inductors have the quality factor of 50 to 80 in the frequency range of 300MHz to 1.3GHz. In this study, small-size solenoid-type RF chip inductors with high inductance and high quality factor were fabricated successfully.
Reduction of gate leakage current for AlGaN/GaN HEMT by
Yang, Jeon-Wook ;
Journal of IKEEE, volume 11, issue 4, 2007, Pages 152~157
AlGaN/GaN high electron mobility transistors (HEMTs) were fabricated and the effect of
plasma on the electrical characteristics of the devices was investigated. The HEMT exposed to
plasma formed by 40 W of RF power in a chamber with pressure of 20 mTorr at a temperature of
, exhibited a reduction of gate leakage current from 246 nA to 1.2 pA by 10 seconds treatment. The current between the two isolated active regions reduced from 3 uA to 7 nA and the sheet resistance of the active layer was lowered also. The variations of electrical characteristics for HEMT were occurred within a short time expose of 10 seconds and the successive expose did not influence on the improvements of gate leakage characteristics and conductivity of the active region. The reduced leakage current level was not varied by successive
deposition and its removal. The transconductnace and drain current of AlGaN/GaN HEMTs were increased also by the expose to the
A novel TIGBT tructure with improved electrical characteristics
Koo, Yong-Seo ; Son, Jung-Man ;
Journal of IKEEE, volume 11, issue 4, 2007, Pages 158~164
In this study, three types of a novel Trench IGBTs(Insulated Gate Bipolar Transistor) are proposed. The first structure has P-collector which is isolated by
layer to enhance anode-injection-efficiency and enable the device to have a low on-state voltage drop(Von). And the second structure has convex P-base region between both gates. This structure may be effective to distributes electric-field crowded to gate edge. So this structure can have higher breakdown voltage(BV) than conventional trench-type IGBT(TIGBT). The process and device simulation results show improved on-state, breakdown and switching characteristics in each structure. The first one was presented lower on state voltage drop(2.1V) than that of conventional one(2.4V). Also, second structurehas higher breakdown voltage(1220V) and faster turn off time(9ns) than that of conventional structure. Finally, the last one of the proposed structure has combined the two structure (the first one and second one). This structure has superior electric characteristics than conventional structure about forward voltage drop and blocking capability, turnoff characteristics.
An Energy-Efficient Clustering Protocol Based on The Cross-Layer Design in Wireless Sensor Networks
Kim, Tae-Kon ; Lee, Hyung-Keun ;
Journal of IKEEE, volume 11, issue 4, 2007, Pages 165~170
The main goal of research concerning clustering protocols is to minimize the energy consumption of each node and maximize the network lifetime of wireless sensor networks. However, most existing clustering protocols mainly focused on the design and formation of clusters, leaving the consideration of communication between the cluster head and the sink behind. In this paper, we propose efficient multi path routing algorithm by using MAC-NET Cross-layering. multi path needed only one tiny packet from sink to setup. In addition proposed algorithm can be used for any cluster-based hierarchical inter-clustering routing algorithm. The simulation results demonstrate that proposed algorithm extended the overall survival time of the network by reducing the load of cluster heads. The performance of proposed algorithm is less affected by the extension of sensing field than other inter-clustering operation.
Efficient Polling Scheduler for IEEE 802.11 WLAN
Kim, Tae-Kon ; Lee, Hyung-Keun ; Koh, Jin-Hwan ;
Journal of IKEEE, volume 11, issue 4, 2007, Pages 171~177
Although the Distributed Coordination Function is the fundamental access protocol of IEEE 802.11, it cannot meet the Quality of Service (QoS) requirements in general. So, the Point Coordinate Function is provided to support QoS related services. However, it has inherent problems. Access point (AP) has no knowledge of the queue status and instantaneous channel condition of stations in the system. In this paper we propose an efficient and versatile polling scheduler that shows excellent throughput and fairness performance. Comparison with well known polling schemes is provided through computer simulation under various channel situations including error prone environments.
A Study of Minimization of Network Overhead Using local Repair in Global-MAHN
Jang, Yang-Geun ; Kim, Jae-Ho ; Bae, Jin-Seung ; Ha, Jae-Seung ; You, Choong-Yeul ; Kim, Hyun-Wook ; Lee, Kwang-Bae ;
Journal of IKEEE, volume 11, issue 4, 2007, Pages 178~186
Recently, The importance of Ubiquitous network that can be supported useful information to MANET mobile device user through wired internet network in anywhere, anytime is growing rapidly. This proposed algorithm is the research on the algorithm, minimizing network overhead by preventing unnecessary network overhead previously and adapting Local repair mechanism to efficient data transmission when route error happens in network, in GMAHN environment.
An Image Mosaic Technique for Images Transmitted by Wireless Sensor Networks
Jun, Sang-Eun ; Eo, Jin-Woo ;
Journal of IKEEE, volume 11, issue 4, 2007, Pages 187~192
Since wireless sensor networks (WSN) have relatively narrow bandwidth and have limited memory space. Mosaic by inlaying images transmitted by adjacent sensors can provide wider field of view and smaller storage memory. Most WSN are used for surveillance purpose, image acquisition period should be sufficiently short, so that mosaic algorithm has to be run in real time. Proposed algorithm is derived by using the fact that position of sensor nodes are fixed and known. Transformation matrix can be calculated by using distance between sensor nodes and distance between sensor nodes and predefined object. Simulation result shows that proposed algorithm provides very short processing time whereas it preserves image quality.
Autotuning of A PID Controller Using a Saturation function Having a Memory
Oh, Seung-Rohk ;
Journal of IKEEE, volume 11, issue 4, 2007, Pages 193~197
We use a saturation function with memory instead of a pure saturation function to generate a limit cycle in order to find one point information of a plant in the frequency domain. The saturation function with memory is useful in the presence of noise and/or a short duration of short duration of external disturbances. We analyze the error caused by the approximation that the saturation function with memory treated as a pure saturation function. We propose a new tuning formula for PID controller which can be applied a saturation function having memory with an arbitrary memory size. We show that the proposed method is more accurate than that of the approximation method via an example.
Improved Iterative Decoding of Parallel and Serially Concatenated Trellis Coded Modulation
You, Cheol-Woo ; Seo, Dong-Sun ;
Journal of IKEEE, volume 11, issue 4, 2007, Pages 198~204
For parallel and serially concatenated trellis coded modulation (TCM), improved iterative decoding schemes with a simple mechanism are proposed and their performances are compared with those of conventional decoding schemes. Simulation results have shown that the proposed schemes have provided a considerable decoding gain in additive white Gaussian noise (AWGN) channels and Rayleigh fading channels, even if they can be implemented by a simple modification of conventional decoding algorithms.
An Energy-Efficient Clustering Design Apply Security Method in Ubiquitous Sensor Networks
Nam, Do-Hyun ; Min, Hong-Ki ;
Journal of IKEEE, volume 11, issue 4, 2007, Pages 205~212
The ubiquitous sensor network consists of micro sensors with wireless communication capabilities. Compared to wired communication, wireless communication is more subject to eavesdropping as well as data variation and manipulation. Accordingly, there must be efforts to secure the information delivered over the sensor network. Providing security to the sensor network, however, requires additional energy consumption, which is an important issue since energy transformation is difficult to implement in a sensor network. This paper proposes a routing mechanism based on the energy-efficient cluster that features security functions capable of safely processing the data acquired from the sensor network. The proposed algorithm reduces energy consumption by fixing the clusters formed at the initial stage and using the pre-distribution scheme so that the cluster and node keys generated and exchanged at the initial stage are not re-generated or re-exchanged. Simulation experiments confirmed that the proposed approach reduces energy consumption compared to implementing security measures to the conventional cluster-based routing mechanism.
Web Tension Control Using Output Feedback
Oh, Seung-Rohk ;
Journal of IKEEE, volume 11, issue 4, 2007, Pages 213~218
We consider a web transport system. The objective of this paper is to design the output feedback controller such that the controller can track a desired tension and processing speed on web transport system. We propose the new design method using observer and feedback linearization technique. The proposed method use a nonlinear feedback to transform to linear system and high gain observer to estimate the state value. We show that the proposed controller can achieve the control object using only output. We show a performance of controller via the simulation.
Block Based Efficient JPEG Encoding Algorithm for HDR Images
Lee, Chul ; Kim, Chang-Su ;
Journal of IKEEE, volume 11, issue 4, 2007, Pages 219~226
An efficient block based two-layer JPEG encoding algorithm is proposed to compress high dynamic range (HDR) images in this work. The proposed algorithm separates an input HDR image into a tone-mapped low dynamic range (LDR) image and a ratio image, which represents the quotients of the original HDR pixels divided by the tone-mapped LDR pixels. Then, the tone-mapped LDR image is compressed using the standard JPEG scheme to preserve backward compatibility and the ratio image is encoded to minimize a cost function that models the perception of each block with different quantization parameters in the human visual system (HVS). Simulation results show that the proposed algorithm provides better performance than the conventional method, which encodes the ratio image without any prior information of blocks.
An Integrated QoS Support Architecture for Wireless Home Network Based on IEEE 802.11 Wireless LAN
Hong, Sung-Hwa ; Kim, Byoung-Kug ; Eom, Doo-Seop ;
Journal of IKEEE, volume 11, issue 4, 2007, Pages 227~234
In this paper, to support a QoS level appropriate to the user in Wireless Home Network based Wireless LAN, we propose a QoS support architecture which includes Wired Network and Wireless Network. Actually, an important problem to support QoS in Wireless Home Network is approached not only on a MAC level in Wireless LAN but also on a integrated method to combine Network layer with Datalink layer. By applying the integrated QoS support method, it is possible to provide QoS support architecture using a Wireless LAN terminal with a minimum changing, and the proposed scheme has advantage of QoS support method, which is more superior than a existing scheme to support QoS in MAC level of Wireless LAN. Simulations results show that overall performance of the proposed scheme can be improved.
The Research of Deep Junction Field Ring using Trench Etch Process for Power Device Edge Termination
Kim, Yo-Han ; Kang, Ey-Goo ; Sung, Man-Young ;
Journal of IKEEE, volume 11, issue 4, 2007, Pages 235~238
The planar edge termination techniques of field-ring and deep junction field-ring were investigated and optimized using a two-dimensional device simulator TMA MEDICI. By trenching the field ring site which would be implanted, a better blocking capability can be obtained. The results show that the p-n junction with deep junction field-ring can accomplish near 30% increase of breakdown voltage in comparison with the conventional field-rings. The deep junctionfield-rings are easy to design and fabricate and consume same area but they are relatively sensitive to surface charge. Extensive device simulations as well as qualitative analyses confirm these conclusions.
HVDC Application Considering Fault Current Characteristics
Park, Jung-Soo ; Jang, Gil-Soo ; Kim, Chan-Ki ;
Journal of IKEEE, volume 11, issue 4, 2007, Pages 239~246
One of the most serious problems in KEPCO power system is the load centralization in the capital area. The load capacity in the capital area is almost 40% of the total load. However, the generation capacity in this area is just 16% of the total generation. The inequality, between the power demand and supply, in this area needs the power transmission from other regions. The simplest method to solve the problem is the installation of power plants or the addition of high-capacity transmission line in the metropolitan area. However, because of the concentration of human and material resources, there is a difficulty in the installation of the generation and transformer facility. As a result, instead of the installation of large scale facilities, the approach to maximize the application of existing facilities is required. In this research, we will develop a scheme with an HVDC installation for enhancing power transfer capability by utilizing the existing transmission lines.
An analysis of new IGBT(Insulator Gate Bipolar Transistor) structure having a additional recessedwith E-field shielding layer
Yu, Seung-Woo ; Lee, Han-Shin ; Kang, Ey-Goo ; Sung, Man-Young ;
Journal of IKEEE, volume 11, issue 4, 2007, Pages 247~251
The recessed gate IGBT has a lower on-state voltage drop compared with the DMOS IGBT, because there is no JFET resistance. But because of the electric field concentration in the corner of the gate edge, the breakdown voltage decreases. This paper is about the new structure to effectively improve the Vce(sat) voltage without breakdown voltage drop in 1700V NPT type recessed gate IGBT with p floating shielding layer. For the fabrication of the recessed gate IGBT with p floating shielding layer, it is necessary to perform the only one implant step for the shielding layer. Analysis on the Breakdown voltage shows the improved values compared to the conventional recessed gate IGBT structures. The result shows the improvement on Breakdown voltage without worsening other characteristics of the device. The electrical characteristics were studied by MEDICI simulation results.
Effects of PCB Ground Plane and Case on Internal WLAN Patch Antenna
Kim, H.T. ; Heo, J.K. ; Jeong, K.J. ; Hwang, S.W. ;
Journal of IKEEE, volume 11, issue 4, 2007, Pages 252~256
We demonstrate that the effect of the PCB ground length and the cover is important in the performance of 2.4 GHz patch antennas. The Center frequency in the return loss shifts as much as 0.5 GHz, when the length of the PCB ground increases from 30 to 85 mm. The position of 10-dB bandwidth accordingly shifts to lower frequency region. Finally, the resonance at 2.4 GHz becomes stronger when the top cover exists. The radiation pattern of the patch antenna is also strongly affected by the ground structure and the existence of the top cover. In both the return loss and the radiation pattern, 3-dimensional simulations are shown to be an efficient tool.
The Emission and Characteristics Measurement of Electron Beam and Basis Construction for Education Usage
Lee, Dong-Hoon ;
Journal of IKEEE, volume 11, issue 4, 2007, Pages 257~264
The MM22 microtron has used as a cancer therapy machine from Nov. 1986 to Feb. 2006. This machine was moved and installed to a radiation research center to use as an education and research tool from treatment machine because of aging of MM22 microtron. In this paper, for extracting the electron beam from microtron, operation principle of the microtron, system characteristics of each module, and pulse structures were reviewed. The beam extraction and measurement were performed after measuring pulses of each major module and extraction trials in the beam line. After finishing the movement of MM22 microtron, the 30mA target current in the case of 10 MV X-ray beam was extracted and the beam flatness of radiation distribution was acquired within 3% error ratio after 100 MU was irradiated on X-omatV Film at SSD 100 cm and field size
. As a result, the microtron movement and new installation was performed with success.
Photonic Bandgap Structures with Arrays of Spiral metal Patches
Jho, Won-June ; Yeom, Dong-Hyuk ; Yoon, Chang-Joon ; Cho, Kyoung-Ah ; Kim, Sang-Sig ;
Journal of IKEEE, volume 11, issue 4, 2007, Pages 265~271
A new type of photonic bandgap(PBG) structures that consist of arrays of spiral metal patches is proposed in this paper. Reflection phases and radiation of these PBG structures are simulated by high frequency structure simulator(HFSS) to characterize their performance. The simulation results show that the resonant frequency of the proposed PBG structures gets significantly lower than those of the PBG structures with square metal patches, but that the radiation is nearly the same for both of the PBG structures. Analysis on reflection phases reveals that the lowering of the resonant frequency is associated with the increase in capacitance.
Simulation and analysis of DC characteristics in AlGaN/GaN HEMTs on sapphire, SiC and Si substrates
Kim, Su-Jin ; Kim, Dong-Ho ; Kim, Jae-Moo ; Choi, Hong-Goo ; Hahn, Cheol-Koo ; Kim, Tae-Geun ;
Journal of IKEEE, volume 11, issue 4, 2007, Pages 272~278
In this paper, we report on the 2D (two-dimensional) simulation result of the DC (direct current) electrical and thermal characteristics of AlGaN/GaN HEMTs (high electron mobility transistors) grown on Si substrate, in comparison with those grown on sapphire and SiC (silicon carbide) substrate, respectively. In general, the electrical properties of HEMT are affected by electron mobility and thermal conductivity, which depend on substrate material. For this reason, the substrates of GaN-based HEMT have been widely studied today. The simulation results are compared and studied by applying general Drift-Diffusion and thermal model altering temperature as 300, 400 and 500 K, respectively. With setting T=300 K and
=1 V, the
(drain saturation current) were 189 mA/mm for sapphire, 293 mA/mm for SiC, and 258 mA/mm for Si, respectively. In addition,
(maximum transfer conductance) of sapphire, SiC, Si was 38, 50, 31 mS/mm, respectively, at T=500 K.
The Framework to Support a Common Way for Context-aware Applications
Baek, Jong-Kwun ; Jung, Hae-Sun ; Jeong, Chang-Sung ;
Journal of IKEEE, volume 11, issue 4, 2007, Pages 279~282
In this paper, we introduce the general way for producing context information to support context-aware applications. It can fetch raw data from the service environments, translate it to reasonable context information, and provide to multiple applications. It is designed originally for the ubiquitous computing middleware and based on the ontology processing model. Automated service applications can use this system as the form of libraries or of web services for deciding its semantic cause of action.
SOA based BPIL workflow system to support multi integration
Yi, Ki-Ho ; Jeong, Chang-Sung ;
Journal of IKEEE, volume 11, issue 4, 2007, Pages 283~292
Due to the development and proliferation of internet technology, cooperation and interaction between companies have become very important. However, different heterogeneous systems have been used as information systems for companies because of various types of pressure in the business environment. Therefore, business process integration and interaction are recognized as essential elements, not optional elements. In addition, it is important to make a business process which is valuable as an intellectual property in a storable form and share. So, many business process languages for service integration and GUI type's automatic systems using the same and making business process easily have been introducing. However, to integrate previously created web service workflows, or to use a web service workflow for another workflow production like an activity, that is, research to support multi integration language and system is not ongoing except for research to make and connect adapter between workflow engines. Also, research for current languages and systems that integrate the BPEL process into a workflow in the industrial world does not exist. This means that integration between workflows being used at companies is difficult, and becomes the biggest obstacle to service integration, which is necessary for cooperation and interaction between companies. To solve this problem, in this paper, I defined BPIL based on XML, which can store business processes. Also, using this, BPIL workflow system based on SOA which supports multiple integration and workflow profiling was designed and prototype was embodied.
Ring type non-invasive glucose sensor
Lee, Ki-Hyuck ; Lee, Kook-Joo ; Lee, Dong-Ho ; Kim, Moon-Il ; Park, Gil-Hong ;
Journal of IKEEE, volume 11, issue 4, 2007, Pages 293~296
A novel sensitive and non-invasive ring-type glucose probe was designed and measured. The magnitude and phase of return loss change with different concentration of the glucose solution inside the loop structure. Ring type probe is more advantageous than open ended probe to measure electrical characteristics under the skin. The maximum difference of return loss was 0.94 for the concentration difference of 0% and 20% at 285MHz and more sensitive in low frequency.
Localization Algorithm without Range Information in Wireless Sensor Networks
Lee, Byoung-Hwa ; Lee, Woo-Yong ; Eom, Doo-Seop ;
Journal of IKEEE, volume 11, issue 4, 2007, Pages 297~306
A sensor network is composed of a large number of sensor nodes that are densely deployed in a field. Each sensor performs a sensing task for detection specific events. After detecting this event, location information of the sensor node is very important. Range-based scheme of the proposed approaches typically achieve high accuracy on either node-to-node distances or angles, but this scheme have a drawback because all sensor nodes have the special hardware. On the other hand, range-free scheme provides economic advantage because of no needed hardware even if that leads to coarse positioning accuracy. In this paper, we propose a range-free localization algorithm without range information in wireless sensor networks. This is a range-free approach and uses a small number of anchor nodes and known sensor nodes. This paper develops a localization mechanism using the geometry conjecture (perpendicular bisector of a chord). The conjecture states that a perpendicular bisector of a chord passes through the center of the circle.
Image Contrast Enhancement Based on Tone Curve Control for LCD TV
Kim, Sang-Jun ; Jang, Min-Soo ; Kim, Yong-Guk ; Park, Gwi-Tae ;
Journal of IKEEE, volume 11, issue 4, 2007, Pages 307~314
In this paper, we propose an image contrast enhancement algorithm for an LCD TV. The proposed algorithm consists of two processes: the image segmentation process and the tone curve control process. The first process uses an automatic threshold technique to decompose an input image into two regions and then utilizes a hierarchical structure for real-time processing. The second process generates a gray level tone curve for contrast enhancement using a weighted sum of average tone curves for two segmented regions. Experimental result shows that the proposed algorithm outperforms the conventional contrast enhancement methods for an LCD TV.
Fast Charging Photoflash Capacitor Charger with Wide Range Current Limiter
Choi, Won-Ho ; Lee, Woo-Kwan ; Kim, Soo-Won ;
Journal of IKEEE, volume 11, issue 4, 2007, Pages 315~321
The fast charging photoflash capacitor charger with wide range current limiter is presented. By using proposed control logic block and wide range current limiter, the photoflash capacitor charger can reduce charging time and control life of battery for user convenience. The proposed photoflash capacitor charger has 3s charging time at 3.3V battery voltage, 1.2A current limit condition. It is well-suited for portable device application like digital camera, digital video camera, and mobile phone with camera.
EETS : Energy- Efficient Time Synchronization for Wireless Sensor Networks
Kim, Soo-Joong ; Hong, Sung-Hwa ; Eom, Doo-Seop ;
Journal of IKEEE, volume 11, issue 4, 2007, Pages 322~330
Recent advances in wireless networks and low-cost, low-power design have led to active research in large-scale networks of small, wireless, low power sensors and actuators, In large-scale networks, lots of timing-synchronization protocols already exist (such as NTP, GPS), In ad-hoc networks, especially wireless sensor networks, it is hard to synchronize all nodes in networks because it has no infrastructure. In addition, sensor nodes have low-power CPU (it cannot perform the complex computation), low batteries, and even they have to have active and inactive section by periods. Therefore, new approach to time synchronization is needed for wireless sensor networks, In this paper, I propose Energy-Efficient Time Synchronization (EETS) protocol providing network-wide time synchronization in wireless sensor networks, The algorithm is organized two phase, In first phase, I make a hierarchical tree with sensor nodes by broadcasting "Level Discovery" packet. In second phase, I synchronize them by exchanging time stamp packets, And I also consider send time, access time and propagation time. I have shown the performance of EETS comparing Timing-sync Protocol for Sensor Networks (TPSN) and Reference Broadcast Synchronization (RBS) about energy efficiency and time synchronization accuracy using NESLsim.
OTP: An Overlay Transport Protocol for End-to-end Congestion and Flow Control in Overlay Networks
Kim, Kyung-Hoe ; Kim, Pyoung-Yun ; Youm, Sung-Kwan ; Seok, Seung-Joon ; Kang, Chul-Hee ;
Journal of IKEEE, volume 11, issue 4, 2007, Pages 331~339
The problem of architecting a reliable transport system across an overlay network using split TCP connections as the transport primitive is mainly considered. The considered overlay network uses the application-level switch in each intermediate host. We first argue that natural designs based on store-and-forward principles that are maintained by split TCP connections of hop-by-hop approaches. These approaches in overlay networks do not concern end-to-end TCP semantics. Then, a new transport protocol-Overlay Transport Protocol (OTP)-that manages the end-to-end connection and is responsible for the congestion/flow control between source host and destination host is proposed. The proposed network model for the congestion and flow control mechanisms uses a new window size-Ownd-and a new timer in the source host and destination host. We validate our analytical findings and evaluate the performance of our OTP using a prototype implementation via simulation.
Pseudo-Orthogonal Space-Time Block Codes for MIMO-OFDM Systems over Frequency-Selective Channels
Lee, Heun-Chul ; Park, Seok-Hwan ; Lee, In-Kyu ;
Journal of IKEEE, volume 11, issue 4, 2007, Pages 340~347
This paper proposes a new class of Space-Time Block Codes, which is manipulated from the existing transmit diversity schemes. We analyze the performance and the receiver complexity of the proposed scheme and confirm that the new diversity scheme can yield performance gain over other existing four-transmit antenna cases. By relaxing the diversity criterion on code designs, the proposed space-time code provides a full transmission rate for four-transmit antennas and makes it possible to approach the open-loop Shannon channel capacity. Outage capacity and simulation results are used to show that substantial improvements in performance while maintaining a simple linear processing receiver structure are obtained in frequency selective channels.
Voronoi-Based Search Scheme for Road Network Databases
Kim, Dae-Hoon ; Hwang, Een-Jun ;
Journal of IKEEE, volume 11, issue 4, 2007, Pages 348~357
Due to the improved performance and cost of personal mobile devices and rapid progress of wireless communication technology, the number of users who utilize these devices is increasing. This trend requires various types of services be available to users. So far, there have been many solutions provided for the shortest path problem. But, technologies which can offer various recommendation services to user depending on user’s current location are focused on Euclidean spaces rather than road network. Thus, in this paper, we extend the previous work to satisfy this requirement on road network database. Our proposed scheme requires pre-computation for the efficient query processing. In the preprocessing step, we first partition the input road network into a fixed number of Voronoi polygons and then pre-compute routing information for each polygon. In the meantime, we select the number of Voronoi polygons in proposition to the scale of road network. Through this selection, the required size of pre-computation is linearly increasing to the size of road network. Using this pre-computated information, we can process queries more quickly. Through experiments, we have shown that our proposed scheme can achieve excellent performance in terms of scheduling time and the number of visited nodes.
A design of a floating point unit with 3 stages for a 3D graphics shader engine
Lee, Kwang-Yeob ;
Journal of IKEEE, volume 11, issue 4, 2007, Pages 358~363
This paper presents a floating point unit(FPU) with 3 stages for a 3D graphics shader engine. It targeted to accelerate 3D graphics in portable device environments. In order to design a balanced architecture for a shader engine, we analyzed shader assembly instructions and estimated the performance of FPU with the method we propose. The proposed unit handles 4-dimensional data through separated two paths that are lead to general operation module and special function module. The proposed FPU is compiled as a form of the cascade FPU with 3 stages to efficiently handle a matrix operation with relatively low hardware overhead. Except some complex instructions that are executed using macro instructions, all instructions complete an operation in a single instruction cycle at 100MHz frequency. A special function module performs all operations in a single clock cycle using the Newton Raphson method with the look-up table.