Earticle

통신 시스템의 설계 전력 여유분을 이용하여 기존 시스템의 구성을 변경하지 않고 시스템의 전반적인 전송효율을 증진시킬 수 있는 적응변조방식의 변환은 주로 전송량에 대한 관점에서 다루었으나, 변조방식의 변환 시 소모되는 순간 에너지는 이동통신 단말과 같이 밧데리가 필요한 장치의 효율을 낮춘다. 따라서 전송효율만을 고려하던 기존방식에 순간 에너지소비의 관점을 도입하여 에너지 효율을 고려한 변환기법을 제안한다.

In this paper, the effective transmission method is proposed to save the energy and to increase the throughput of the communication system using adaptive modulation. Traditionally, adaptive modulation has been used to improve the throughput using the power margin of the system design. Considering the instantaneous energy during the modulation method changing duration, the effective transmission method is proposed. By the simulation, the performance and effectiveness is validated.

이동통신 시스템에 적용되는 적응변조방식의 변환은 주변 환경을 고려한 변환을 사용하므로, 변환 조건 및 이에 따른 전송량의 변화에 대한 관점에서 다루었으나, 이동통신 단말기와 같이 에너지 효율이 좋아야 하는 경우에 는 이러한 적응방식이 성능을 낮게 할 경우가 발생한다. 따라서 전송효율만을 고려하던 기존방식에서 소비 에너지를 고려하고, 프레임 길이를 조절하여 사용하는 적응변조방식을 제어하는 최적화 방식을 제안한다.

In this paper, the optimum transmission method is proposed to save the energy and to increase the throughput of the adaptive modulation mobile radio system with frame length control. Traditionally, adaptive modulation has been used to improve the throughput using the power margin of the system design. Considering the frame length vs energy saving and adptive modulation, the optimum transmission method is proposed for hub and mobile station each.

Due to the influence of noise in the received signal in non-cooperative communication, it is difficult for existing Automatic modulation classification methods to balance classification accuracy and model complexity. This paper proposes a novel Convolutional Adaptive Noise Reduction (CANR) network, which consists of an Adaptive Noise Reduction (ANR) module and a Convolutional Feature Extraction (CFE) module. The ANR and CFE modules denoise the combined input and capture the spatiotemporal features in the time series. Experiments on benchmark datasets show that the proposed network has the fewest training parameters and state-of-the-art recognition accuracy under the same conditions.

본 연구는 감각통합치료놀이를 자폐스펙트럼장애 아동에게 적용하고, 연구참여 아동의 감각조절기능과 적응행동의 변화를 살펴보고자 하는 목적으로 실시되었다. 연구대상은 광주전라지역에서 감각조절장애 동반한 자폐스펙트럼장애 아동 30명을 대상으로 하였으며, 만 3세에서 5세 아동이었다. 본 연구에서 사용된 감각통합치료놀이 활동은 놀이치료 전문가 3인, 감각통합치료사 3인, 소아정신과 의사 2인으로 구성한 8인의 전문가 집단을 통해 내용타당도 검증의 과정을 거쳐, 프로그램의 목적에 맞게 수정 및 보완을 하였다. 연구설계는 실험 및 통제집단 사전사후 검사설계를 하여 효과를 살펴보았다. 회기진행은 60분씩 6주간 총 12회기가 진행되었다. 연구결과, 감각통합치료놀이에 참여한 아동은 통제집단과 비교 시, 감각조절기능 및 적응행동 개선에 유의미한 효과가 있었다. 따라서 감각통합치료놀이 활동은 자폐스펙트럼 장애 아동의 감각조절 기능과 적응행동 개선에 효과가 있는 것으로 나타났다. 연구결과를 바탕으로 자폐스펙트럼 장애 아동을 치료할 때, 중재 계획의 기초자료로서 활용되어진다면 자폐스펙트럼장애 아동의 감각조절 기능 및 적응행동 발달에 긍정적인 영향을 미칠 것으로 기대된다.

논문에서는 양방향 중계기 통신에서 사용자와 중계기의 채널 환경을 기준으로 중계기의 QoS(Quality of Service)를 만족시키도록 하는 적응형 변조 기법을 이용한 네트워크 부호화 기반 양방향 중계기 통신을 제안한다. 양방향 중계기 통신은 두 사용자가 중계기의 도움을 받아 서로의 데이터를 교환하는 통신 방식이다. 네트워크 부호화를 이용한 양방향 중계기 통신은 기존의 양방향 통신에 비해 데이터 전송에 필요한 시간을 줄임으로써 높은 처리량(throughput)을 얻을 수 있다. 본 논문에서는 사용자와 중계기간의 채널 환경를 기준으로 M-QAM(Quadrature Amplitude Modulation) 변조 기법을 이용하여 시스템의 QoS를 만족시키는 적응형 변조 방법을 제안한다. 모의 실험을 통해 제안한 방식이 시스템이 원하는 QoS를 만족시킴을 보인다.

In this paper, we propose network-coding based two-way relay communication using adaptive modulation scheme for satisfying relay QoS(Quality of Service) according to channel environment between user and relay. Two-way relay communication is bidirectional cooperative communication that users exchange own signal with help of relay. Network-coding based two-way relay communication can achieve high throughput compared to conventional scheme through reducing time slots. we propose adaptive M-QAM modulation scheme in network-coding based two-way relay communication for satisfying QoS of relay. Simulation result shows that the proposed scheme satisfies goal QoS of system.

An uplink structure of convolution coded V-BLAST MC-CDMA system was analysed. The adaptive modulation techniques were applied to the system. The effective of adaptive modulation were set by simulation. The expected bit error rate (BER) were settled first, and then according to the BER simulation results, the conversion thresholds of modulation types of the system were determined. The BER performance of the adaptive modulation V-BLAST MC-CDMA system for a given various number of users was simulated. Simulation results show that adaptive modulation improves the spectrum efficiency of the system without sacrificing the expected BER performance.

Underwater Acoustic (UWA) channels are known as some of the most challenging communication media. Since the Underwater acoustic channels are time varying multipath channel achieving the high data rate, a low latency and a high throughput which often is a very difficult objective. In this work, we designed an OFDM transceiver system which is suitable for underwater acoustic communication with limited bandwidth to enhance the data rate at the receiver. To enhance the data rate at the OFDM receiver we have used efficient adaptive modulation scheme, channel estimation and channel equalization schemes for UWA communication. We have focused on the efficient modulation schemes like QPSK, DPSK and 16-QAM which is best suited for adaptive techniques based on the SNR of the Rayleigh fading channel to enhance the data rate. The simulation results show that the performance of the OFDM system with the use of Adaptive modulation is better when compared to the OFDM system without Adaptive modulation schemes. Also we have used the Kalman filter for channel estimation which minimizes the mean squared error and gives us the best estimation even in the presence of noise. From the simulation results, we have found that these modulation techniques and channel estimation method are best suited to achieve high data rate for underwater acoustic communication.

Aiming at the problem that the theoretical spectrum expression of the output voltage waveform in the space vector pulse width modulation strategy is often extremely complicated, most tedious and quite error-prone, the study develops a universal procedure and algorithm with adaptive precision to analyze the harmonic spectrum. The key steps and technique of the procedure and algorithm are given firstly. The algorithm steps include storing the switching states and the vector sequences, computing the basic space vector duration time, storing the duration time, sampling output voltage values and computing the spectrum using the fast Fourier transform algorithm. The sampling number doubles in each iteration for the next iteration. The adaptive precision is realized through controlling the amplitude or magnitude error between the current result and the previous result. The realization method and the key codes are presented secondly. Finally, three numerical experiments are presented to verify the developed algorithm, and the results verify its correctness, reliability and convenience.

A key requirement for packet based wireless communication systems is to provide a high data rate packet service and improved throughput. To achieve a high throughput, adaptive methods for adjustment of the modulation and coding can be used. In this paper, we propose and analyze a scheme which is a combination of an adaptive modulation and coding(AMC) and transmit diversity(TD). Two different TD schemes are analysed: STTD and STD. Proposed system provides significant improvement in the average throughput.

무선 스마트카드는 빌딩 보안 어플리케이션에 주된 역할을 하고 있다. 본 연구는 사용자에게 보다 편리함을 주고 스마트카드 시스템의 성능 개선을 제안한다. 스마트카드는 카드 리더기에 삽입을 하지 않고 장치에서 수센티미터 떨어져도 접근이 허용된다. 적응형 변조와 오류 제어를 통해 전력소비를 제어하는 성능은 필요하다. 본 논문에서는 적응형 리드 솔로몬 코드 기반의 FEC와 링크에서 M계수를 변화시킨 M-FSK변조에 대하여 연구한다. 적응형 변조와 적응형 오류 정정은 다른 다양한 정적스키마와 에너지 효율을 비교한 결과 50% 이상 에너지를 저장한다.

Since the wireless smart card has played a main role in the identification security application for the building access; this research has its purpose to improve the performance of the smart card system and aims to offer more convenient to user. The contactless cards do not require insertion into a card reader and can work up to centimeters away from the reading device. To be able to cope with this performance the controlling of power consumption through the adaptive modulation and error control is needed. This paper addresses a forward error control (FEC) scheme with the adaptive Reed-Solomon code rate and an M-ary frequency shift keying (M-FSK) modulation scheme with the varying symbol size M over the link. The result of comparing energy efficiencies of adaptive error correction and adaptive modulation to other various static schemes shows to save over 50% of the energy consumption.

Orthogonal Frequency Division Multiplexing (OFDM), which employs orthogonal overlapping subcarriers to modulate the signals, has been attracted much attention in recent time as a favorable option for future generation wireless networks due to its ability to overcome many impairments in wireless channels. Since OFDM is a multi-carrier system adaptive modulation techniques can be effectively and efficiently used to enhance the system performance in terms of both BER and overall system capacity. This paper discusses a COFDM-CDMA system with adaptive modulation schemes for future generation wireless networks.

To realize the wireless packet scheduler which efficiently considers both the effect of adaptive modulation and coding (AMC) scheme due to variable wireless communication channel information from physical layer and the QoS differentiation of multimedia services from internet protocol (IP) layer, this paper proposes a new downlink AMC-based priority queuing (APQ) scheduler which combines AMC scheme and service priority method in multimedia services at the same time. The result of numerical analysis shows that the proposed APQ algorithm plays a role in increasing the number of services satisfying the mean waiting time requirements per each service in multimedia services because the APQ scheme allows the mean waiting time of each service to be reduced much more than existing packet scheduler having only user selection processor.

An adaptive modulation scheme is presented for multiuser orthogonal frequency-division multiplexing systems. The aim of the scheme is to minimize the total transmit power with a constraint on the transmission rate for users, assuming knowledge of the instantaneous channel gains for all users using a combined bit-loading and subcarrier allocation algorithm. The subcarrier allocation algorithm identifies the appropriate assignment of subcarriers to the users, while the bit-loading algorithm determines the number of bits given to each subcarrier. The proposed bit-loading algorithm is derived from the geometric progression of the additional transmission power required by the subcarriers and the arithmetic-geometric means inequality. This algorithm has a simple procedure and low computational complexity. A heuristic approach is also used for the subcarrier allocation algorithm, providing a trade-off between complexity and performance. Numerical results demonstrate that the proposed algorithms provide comparable performance with existing algorithms with low computational cost.

In this paper, an Adaptive Modulation (AM) system with an efficient turbo-coded Vertical-Bell-lab Layered Space-Time (V-BLAST) technique is proposed. The proposed decoding algorithm adopts iteratively the extrinsic information from a Maximum a Posteriori (MAP) decoder as a priori probability in the two decoding procedures of the V-BLAST scheme of ordering and slicing. In this analysis, each MIMO channel is assumed to be a part of the system of performance improvement.

In this paper, an Adaptive Modulation (AM) system with an efficient turbo-coded Vertical-Bell-lab Layered Space-Time (V-BLAST) technique is proposed. The proposed decoding algorithm adopts iteratively the extrinsic information from a Maximum a Posteriori (MAP) decoder as a priori probability in the two decoding procedures of the V-BLAST scheme of ordering and slicing. In this analysis, each MIMO channel is assumed to be a part of the system of performance improvement.

In this paper, an adaptive minimum transmit power modulation scheme under constant data rate and fixed bit error rate (BER) for the multiple-input multiple-output (MIMO) system is proposed. It adjusts the modulation order and allocates the transmit power to each spatial sub-channel when meeting the user's requirements at the cost of minimum transmission power. Compared to the other algorithm, it can obtain good performance with lower computational complexity and can be applied to the wireless communication system. Computer simulation results present the efficiency of the proposed scheme. And its performance under different channel condition has been compared with the other algorithm.

In this work, we consider imperfectness of feedback channels in the adaptive transmission scheme which was previously studied with an assumption of error-free feedback channels. New method of mapping the modulation index into the feedback channel symbols and quantifying feedback error over fading channels are proposed. The presented method and results are expected to offer valuable tools for the system designer to efficiently implement adaptive diversity schemes to compensate for the performance degradation due to feedback error.

We propose a sub-band spreading technique for adaptive modulation (AM) in orthogonal frequency division multiplexing (OFDM) systems in order to reduce signaling overheads and to average frequency selective fading channels causing different signal-to-noise ratio (SNR) values for subcarriers in each subband. The conventional sub-band based AM schemes can also reduce signaling overheads and complexity for allocating a resource per sub-band at a time. However, they may suffer from the channel variation in a sub-band when the sub-band size is larger than the channel coherence bandwidth (BW). The sub-band spreading at the transmitter enables the received symbols in each sub-band to have an identical reliability even in a frequency selective fading channel. We rigorously analyze the averaged SNR value at the receiver of the sub-band spreading system and the analyzed average SNR in a sub-band is used for an adaptation criterion. The proposed AM scheme outperforms the conventional sub-band based OFDM scheme without spreading, and it can yield better throughput performance than the conventional subcarrier based AM schemes when we consider the signaling overheads.