• Journal of Digital Convergence
• /
• v.10 no.3
• /
• pp.265-271
• /
• 2012

This paper proposes a communication distance performance evaluation method for mobility of service robots equipped with a Wi-Fi module. Service robots have function of mobile communication system according to classified services and utilize a (preferred) communication method, wireless lan(IEEE802.11 a/b/gin) communication method of ISM band(2.4GHz and 5.8GHz). For evaluating degradation performance of wireless data for the service robot's mobility. We measured and presented reference vectors obtained by utilizing a distance attenuation correlation method in the real world environment. To evaluate performance of the proposed method, path loss of reference vectors was assigned to the Azimuth 301W and then transmission rate and the transmit throughput of the test sample were measured by the Chariot. The proposed measurement method is necessary for securing wireless LAN communication distance for mobility of mobile smart device and service robots. In addition, if the proposed measurement method os adopted, It would be expected that mobile smart device vendors would utilize the method as an effective wireless LAN mobility communication distance performance evaluation method.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.1 no.4
• /
• pp.239-247
• /
• 2001

The Fluorescence-Activated Cell Sorter (FACS) is a well-established instrument used for identifying, enumerating, classifying and sorting cells by their physical and optical characteristics. For a miniaturized FACS device, a disposable plastic microchip has been developed which has a hydrodynamic focusing chamber using soft lithography. As the characteristics of the spatially confined sample stream have an effect on sample throughput, detection efficiency, and the accuracy of cell sorting, systematic fluid dynamic studies are required. Flow visualization is conducted with a laser scanning confocal microscopy (LSCM), and three-dimensional flow structure of the focused sample stream is reconstructed from 2D slices acquired at $1\mutextrm{m}$ intervals in depth. It was observed that the flow structure in the focusing chamber is skewed by unsymmetrical velocity profile arising from trapezoidal cross section of the microchannel. For a quantitative analysis of a microscopic flow structure, Confocal Micro-PIV system has been developed to evaluate the accelerated flow field in the focusing chamber. This study proposes a method which defines the depth of the measurement volume using a detection pinhole. The trajectories of red blood cells (RBCs) and their interactions with surrounding flow field in the squeezed sample stream are evaluated to find optimal shape of the focusing chamber and fluid manipulation scheme for stable cell transporting, efficient detection, and sorting

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.44 no.11
• /
• pp.19-24
• /
• 2007

This paper presents a performance analysis of dynamic channel allocation (DCA) based on the greedy approach (GA) for orthogonal frequency division multiple access (OFDMA) systems over Rayleigh fading channels. The GA-based DCA achieves its performance improvement using multi-user diversity. We analyze the statistics of the number of allocable users (NAU), which represents the multi-user diversity order at each allocation process. The derived statistics are then used to analyze the performance of GA-based DCA. The analysis results show that the number of subcarriers allocated to each user must be equal to achieve the maximum system performance (i.e., based on outage probability and data throughput).

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.17 no.3
• /
• pp.446-457
• /
• 2017

In order to reduce the size of frame memory or bus bandwidth, frame memory compression (FMC) recompresses reconstructed or reference frames of video codecs. This paper proposes a novel FMC design based on discrete wavelet transform (DWT) - set partitioning in hierarchical trees (SPIHT), which supports fine-scalable throughput and is area-efficient. In the proposed design, multi-cores with small block sizes are used in parallel instead of a single core with a large block size. In addition, an appropriate pipelining schedule is proposed. Compared to the previous design, the proposed design achieves the processing speed which is closer to the target system speed, and therefore it is more efficient in hardware utilization. In addition, a scheme in which two passes of SPIHT are merged into one pass called merged refinement pass (MRP) is proposed. As the number of shifters decreases and the bit-width of remained shifters is reduced, the size of SPIHT hardware significantly decreases. The proposed FMC encoder and decoder designs achieve the throughputs of 4,448 and 4,000 Mpixels/s, respectively, and their gate counts are 76.5K and 107.8K. When the proposed design is applied to high efficiency video codec (HEVC), it achieves 1.96% lower average BDBR and 0.05 dB higher average BDPSNR than the previous FMC design.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.10 no.1
• /
• pp.76-83
• /
• 2011

The IEEE WAVE-based communication systems do not provide handover services since most of the application layer messages of a small amount containing text data that are related to safe driving. Multimedia data service such as web pages and CCTV video clips, however, require a seamless handover for continuation of a session via multiple RSUs. In this paper, we propose a new proactive handover protocol based on IEEE WAVE. According to the proposed handover protocol, the OBU notifies the old RSU of its departure from the coverage such that the old RSU forwards to the new RSU the data heading towards the OBU to be cached for the further delivery upon its entry into the new RSU's coverage. The simulation results are presented which shows the performance of the proposed protocol in terms of throughput, delivery ratio and handover delay.

• Journal of Microbiology and Biotechnology
• /
• v.27 no.10
• /
• pp.1798-1807
• /
• 2017

The differentiations in nitrogen-converting activity and microbial community structure between granular size fractions in a continuous completely autotrophic nitrogen removal over nitrite (CANON) reactor, having a superior specific nitrogen removal rate of $0.24g/(g\;VSS{\cdot}h)$, were investigated by batch tests and high-throughput pyrosequencing analysis, respectively. Results revealed that a high dissolved oxygen concentration (>1.8 mg/l) could result in efficient nitrite accumulation with small granules (0.2-0.6 mm in diameter), because aerobic ammonium-oxidizing bacteria (genus Nitrosomonas) predominated therein. Meanwhile, intermediate size granules (1.4-2.0 mm in diameter) showed the highest nitrogen removal activity of $40.4mg/(g\;VSS{\cdot}h)$ under sufficient oxygen supply, corresponding to the relative abundance ratio of aerobic to anaerobic ammonium-oxidizing bacteria (genus Candidatus Kuenenia) of 5.7. Additionally, a dual substrate competition for oxygen and nitrite would be considered as the main mechanism for repression of nitrite-oxidizing bacteria, and the few Nitrospira spp. did not remarkably affect the overall performance of the reactor. Because all the granular size fractions could accomplish the CANON process independently under oxygen limiting conditions, maintaining a diversity of granular size would facilitate the stability of the suspended growth CANON system.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.40 no.11
• /
• pp.2169-2177
• /
• 2015

This paper proposes a new pattern matching module to overcome the increased runtime of previous algorithm using RAM, which was designed to overcome cost limitation of hash-based algorithm using CAM (Content Addressable Memory). By adopting Merge FSM algorithm to reduce the number of state, the proposed module contains state block and entry block to use in RAM. In the proposed module, one input string is compared with multiple entry strings simultaneously using entry block. The effectiveness of the proposed pattern matching unit is verified by executing Snort 2.9 rule set. Experimental results show that the number of memory reads has decreased by 15.8%, throughput has increased by 47.1%, while memory usage has increased by 2.6%, when compared to previous methods.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.44 no.9
• /
• pp.9-16
• /
• 2007

In the multiuser OFDM systems, an efficient resource allocation is necessary in order to provide the service to more users. This paper proposes u improved subcarrier allocation algorithm, satisfying each user's QoS under the limited resources, to maximize total transmission data rate and spectral efficiency. The proposed algorithm is divided into two steps. In the first step, users who are eligible for services are determined by using BER, user's minimum data rate requirement, and channel information. In the second step, first, subcarriers are allocated to users on the basis of channel state. And then, reallocation is fulfilled so that the total transmission data rate is maximized and the least reduction in the overall throughput is caused.

• Journal of Internet Computing and Services
• /
• v.12 no.4
• /
• pp.1-14
• /
• 2011

This paper analyzes the fairness and efficiency of channel sharing when heterogeneous wireless networks that have different transmission power and/or coverage coexist with the contention-based channel access protocol. First, we show that the existing CSMA (carrier sensing multiple access) protocol, that is a prevailing contention-based mechanism, results in significant unfairness of channel access because of (1) the asymmetric capability of carrier sensing and (2) the blindness of binary exponential backoff and link adaptation mechanisms to the interference-driven transmission failures. Next, we derive the feasible region of carrier sensing thresholds that assures spatial reuse and fair channel sharing simultaneously. Moreover, we establish an analytical model for per-system throughput and investigate the effect of contention window size and transmission rate on the fairness and efficiency of channel sharing. Finally, we compare the performance of several approaches for fair channel sharing via simulations under various network configurations.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.36 no.5B
• /
• pp.429-436
• /
• 2011

The G-PON is an efficient solution to implement the FTTH and have GEM frame to accomodate various protocols like Ethernet frames, IP packets, and TDM signals. Above all, the Ethernet is one of the most widely used 2nd layer protocol in the campus, the subscriber access, and the carrier service. So G-PON system has to provide an Ethernet interface with top priority. In this paper, we implement a gigabit Ethernet adapter based on Ethernet over GEM in the ITU-T G.984.3 to accommodate Ethernet protocol in the G-PON TC chip. The adapter maps each Ethernet frame to a single or multiple GEM frames and has several functions including generation of the GEM header, encapsulation of frames and the SAR. In particular, the adapter have converter (LUT) MAC address to port-ID which is a key to identify logical connections though it is not defined in specification but important. We implement the adapter with a FPGA and verify the functions of segmentation and reassembling, MAC address learning, and throughput with the logic analyzer and the Ethernet analyzer.