Sangjin Ryoo

Channel estimation method using power control schemes in wireless systems

Green communication is a new paradigm of designing the communication system which considers not only the processing performance but also the energy efficiency. Power control management is one of the approaches in green communication to reduce the power consumption in distributed communication system. In this paper, we propose improved power control schemes for mobile satellite systems with ancillary terrestrial components (ATCs). In order to increase system capacity and reduce the transmitting power of the users equipment, we propose an efficient channel estimation method consisting of a modified open-loop power control (OLPC) and closed-loop power control (CLPC). The OLPC works well if the forward and reverse links are perfectly correlated. The CLPC is sensitive to round-trip delay and, therefore, it is not effective in a mobile satellite system. In order to solve the above problem, we added monitoring equipment to both the OLPC and CLPC to use information about transmitting power that has not yet been received by the receiver over the satellite/ATC channel. Moreover, we adapted an efficient pilot diversity of both OLPC and CLPC in order to get a better signal to interference plus noise ratio estimation of the received signal.

Improvement of the Combined AMC-MIMO Systems with Independent MCS Level Selection

In this paper, we propose and observe a system that adopts Independent MCS (Modulation and Coding Scheme) level for each layer in the combined AMC-V-BLAST (Adaptive Modulation and Coding-Vertical-Bell-lab Layered Space-Time) system. Also, comparing with the combined system using Common MCS level, we observe how much throughput performance is improved. As a result of simulation, Independent MCS level case adapts modulation and coding scheme for maximum throughput to each channel condition in separate layer, resulting in improved throughput compared to Common MCS level case. Especially, the results show that the combined AMC-V-BLAST system with Independent MCS level achieves a gain of 700kbps in 7~9dB SNR (Signal-to-Noise Ratio) range.

Cell Image Segmentation by Contour Following Method with Directional Angle

This paper proposes the new method based on contour following method with Directional angle to segment the cell image into the nuclei. The object image was the Thyroid Gland cell image that was diagnosed as normal and abnormal (two types of abnormal: follicular neoplastic cell, and papillary neoplastic cell), respectively. The nuclei were successfully segmented by proposed method in this paper. Improved method of digital image analysis required in basic medical science for diagnosis of cells was proposed. The object image was the Thyroid Gland cell image with difference of chromatin patterns. To segment the cell nucleus from background, the region segmentation algorithm by edge tracing was proposed. After construct a feature sample group of each cell, experiment of segmentation was executed with any verification cells. As a result of experiment using features proposed in this paper, Get a better segmentation rate than previously reported papers. And this method gives shape to get objectivity and fixed quantity in diagnosis of cells. The methods described in this paper can be used immediately for discrimination of neoplastic cells.

Quantization Error According to Bit Truncation Method in 4k-FFT Algorithm

In this paper, we compare a quantization error performance of FFT algorithm according to bit truncation method. 4k-FFT algorithm of OFDM is proposed and implemented in field programmable gate arrays (FPGAs). We analyze the quantization error performance according to bit truncation method. Measured results show the maximum quantization error of 6.042152/6.067595 (real/imaginary value in 12 stage MSB truncation), 3.112953/2.627594 (real/imaginary value in 12 stage LSB truncation), 0.006065/0.005448 (real/imaginary value in 6 stage LSB/6 stage MSB truncation) in 1st method. And measured results show the maximum quantization error of 0.001464/0.00129 (real/imaginary value in truncation after FFT) in 2nd method.

Feasibility Study of 32 Trellis-Coded OFDM Waveform for Tactical Information Communication

In this paper, the applicability of 32 trellis-coded OFDM waveform is studied for the tactical information communications system in NCW (Network Centric Warfare). In order to reduce received SNR in BER 1.0E-6 conditions, we proposed a 32-TCM. We also applied OFDM technologies such as timing recovery, carrier recovery, and equalizer, in order to reduce robust channel impairments caused by non-LOS environments where a signal is not received from another system. Simulation results show that coding gain of a 32 trellis-coded OFDM waveform has about 7 dB and 2 dB, compared to single-carrier 16-QAM waveform and OFDM (16QAM) waveform in tactical communication environments, respectively.

An Improved Power Estimation for Mobile Satellite Communication Systems

In this paper, in order to increase system capacity and reduce the transmitting power of the users equipment, we propose a efficient power estimation algorithm consisting of a modified open-loop power control (OLPC) and closed-loop power control (CLPC) for mobile satellite communications systems. The improved CLPC scheme, combining delay compensation algorithms and pilot diversity, is mainly applied to the ancillary ter-restrial component (ATC). ATC link in urban areas, because it is more suitable to the short round-trip delay (RTD). In the case of rural areas, where ATCs are not deployed or where a signal is not received from ATCs, transmit power monitoring equipment and OLPC schemes using efficient pilot diversity are combined and ap-plied to the link between the users equipment and the satellite. Two modified power control schemes are ap-plied equally to the boundary areas where two kinds of signals are received in order to ensure coverage conti-nuity. Simulation results show that the improved power control scheme has good performance compared to conventional power control schemes in a geostationary earth orbit (GEO) satellite system utilizing ATCs.

Performance Analysis of an AMC System with an Iterative V-BLAST Decoding Algorithm

In this paper, the iterative Vertical-Bell-lab Layered Space-Time (V-BLAST) decoding algorithm of an Adaptive Modulation and Coding (AMC) system is proposed, and the corresponding MIMO scheme is analyzed. The proposed decoding algorithm adopts iteratively extrinsic information from a Maximum A Posteriori (MAP) decoder as an a priori probability in the two decoding procedures of the V-BLAST scheme of ordering and slicing in an AMC system. Furthermore, the performance of the proposed decoding algorithm is compared with that of a conventional V-BLAST decoding algorithm and a Maximum Likelihood (ML) decoding algorithm in the combined system of an AMC scheme and a V-BLAST scheme. In this analysis, each MIMO schemes are assumed to be parts of the system for performance improvement.

Adaptive Modulation and Coding Scheme with Independent MCS Level Selection in MIMO Systems

In this paper, we propose a system that adopts the independent MCS (modulation and coding scheme) level for each layer in the AMC (adaptive modulation and coding) scheme combined with the V-BLAST (vertical Bell lab layered space time) system. From the simulation results, we observe that since the independent MCS level case adapts modulation and coding rate for maximum throughput to each channel condition in separate layers, the combined AMC-V-BLAST system with the independent MCS level selection results in improved throughput compared to the combined AMC-V-BLAST system with the common MCS level selection and the conventional AMC system based on the 1x EV-DO standard. Especially, the combined AMC-V-BLAST system with the independent MCS level achieves a gain of 700 kbps in 7–9 dB SNR (signal-to-noise ratio) range.

Iterative Decoding Algorithm in the Adaptive Modulation and Coding System with MIMO Schemes

In this paper, we propose and analyze the adaptive modulation system with optimal Turbo Coded V-BLAST (Vertical-Bell-lab Layered Space-Time) technique that adopts extrinsic information from a MAP (Maximum A Posteriori) decoder with iterative decoding as a priori probability in two decoding procedures of V-BLAST scheme; the ordering and the slicing. Also, we consider the AMC (Adaptive Modulation and Coding) using the conventional Turbo Coded V-BLAST technique that simply combines the V-BLAST scheme with the turbo coding scheme. And we compare the proposed iterative decoding algorithm to a conventional V-BLAST decoding algorithm and a ML (Maximum Likelihood) decoding algorithm. In this analysis, the MIMO (Multiple Input Multiple Output) and the STD (Selection Transmit Diversity) schemes are assumed to be parts of the system for performance improvement. Results indicate that the proposed systems achieve better throughput performance than the conventional systems over the whole SNR (Signal to Noise Ratio) range. In terms of transmission rate performance, the suggested system is close in proximity to the conventional system using the ML decoding algorithm. In addition, the simulation result shows that the maximum throughput improvement in each MIMO scheme is respectively about 350kbps, 460kbps, and 740kbps. It is suggested that the effect of the proposed iterative decoding algorithm accordingly gets higher as the number of system antenna increases.

Performance Improvement of the Combined AMC-MIMO Systems with MCS Level Selection Technique

In this paper, we propose and observe a system that adopts independent MCS (modulation and coding scheme) level for each layer in the combined AMC-V- BLAST (adaptive modulation and coding-vertical- bell-lab layered space-time) system. Also, comparing with the combined system using common MCS level, the proposed system applied to Independent MCS level shows how much throughput performance is improved. As a result of simulation, Independent MCS level case adapts modulation and coding scheme for maximum throughput to each channel condition in separate layer, resulting in improved throughput compared to common MCS level case. Especially, the results show that the combined AMC-V-BLAST system with Independent MCS level achieves a gain of 700 kbps in 7~9 dB SNR (signal-to-noise ratio) range.