• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.23 no.1
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• pp.45-50
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• 2023

In order to improve a total system throughput when a base station (BS) transmits data to user equipments (UEs), we propose a scheme to apply multiuser multiple-input multiple-output (MU-MIMO), space-time block coding (STBC), and non-orthogonal multiple access (NOMA) together. An MU-MIMO is applied to two UEs near the BS and STBC is applied to a UE far from the BS because of the difficulty of obtaining the channel information. Also NOMA is applied to differentiate the data from the near UE and the far UE. Two orthognal precoding vectors are used for the MU-MIMO UEs and it causes no interference between them. The STBC technique with the two procoding vectors are also used for the far UEs. Through performance analysis and simulation, we show that the proposed scheme has higher total system throughput than the conventional ones.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.11
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• pp.2594-2603
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• 1997

A novel method of adaptive beam forming is presented in this paper. The proposed technique provides for a suboptimal beam pattern that increases the Signal to Noise/Interference Ratio (SNR/SIR), thus, eventually increases the capacity of the communication channel, under an assumption that the desired signal is dominant compared to each component of interferences at the receiver, which is precoditionally achieved in Code Division Multiple Access (CDMA) mobile communications by the chip correlator. The main advantages of the new technique are:(1)The procedure requires neither reference signals nor training period, (2)The signal interchoerency does not affect the performance or complexity of the entire procedure, (3)The number of antennas does not have to be greater than that of the signals of distinct arrival angles, (4)The entire procedure is iterative such that a new suboptimal beam pattern be generated upon the arrival of each new data of which the arrival angle keeps changing due tot he mobility of the signal source, (5)The total amount of computation is tremendously reduced compared to that of most conventional beam forming techniques such that the suboptimal beam pattern be produced at vevery snapshot on a real-time basis. The total computational load for generating a new set of weitht including the update of an N-by-N(N is the number of antenna elements) autocovariance matrix is $0(3N^2 + 12N)$. It can further be reduced down to O(11N) by approximating the matrix with the instantaneous signal vector.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.6
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• pp.115-121
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• 2013

This paper related with the DSE-MMA (Dithered Sign-Error MMA) that is the simplification of computational arithmetic number in blind equalization algorithm in order to compensates the intersymbol interference which occurs the passing the nonlinear communication channel in the presence of the band limit and phase distortion. The SE-MMA algorithm has a merit of H/W implementation for the possible to reduction of computational arithmetic number using the 1 bit quantizer in stead of multiplication in the updating the equalizer tap weight. But it degradates the overall blind equalization algorithm performance by the information loss at the quantization process compare to the MMA. The DSE-MMA which implements the dithered signed-error concepts by using the dither signal before qualtization are added to MMA, then the improved SNR performance which represents the roburstness of equalization algorithm are obtained. It has a concurrently compensation capability of the amplitude and phase distortion due to intersymbol interference like as the SE-MMA and MMA algorithm. The paper uses the equalizer output signal, residual isi, MD, MSE learning curve and SER curve for the performance index of blind equalization algorithm, and the computer simulation were performed in order to compare the SE-MMA and DSE-MMA applying the same performance index. As a result of simulation, the DSE-MMA can improving the roburstness and the value of every performance index after steady state than the SE-MMA, and confirmed that the DSE-MMA has slow convergence speed which meaning the reaching the seady state from initial state of adaptive equalization filter.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.11
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• pp.51-62
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• 2003

This paper presents a novel survivor memeory management and decoding techniques with sequential backward state transition control in the trace back Viterbi decoder. The Viterbi algorithm is an maximum likelihood decoding scheme to estimate the likelihood of encoder state for channel error detection and correction. This scheme is applied to a broad range of digital communication such as intersymbol interference removing and channel equalization. In order to achieve the area-efficiency VLSI chip design with high throughput in the Viterbi decoder in which recursive operation is implied, more research is required to obtain a simple systematic parallel ACS architecture and surviver memory management. As a method of solution to the problem, this paper addresses a progressive decoding algorithm with sequential backward state transition control in the trace back Viterbi decoder. Compared to the conventional trace back decoding techniques, the required total memory can be greatly reduced in the proposed method. Furthermore, the proposed method can be implemented with a simple pipelined structure with systolic array type architecture. The implementation of the peripheral logic circuit for the control of memory access is not required, and memory access bandwidth can be reduced Therefore, the proposed method has characteristics of high area-efficiency and low power consumption with high throughput. Finally, the examples of decoding results for the received data with channel noise and application result are provided to evaluate the efficiency of the proposed method.

• Science of Emotion and Sensibility
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• v.21 no.2
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• pp.137-144
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• 2018

The study figured out the operational conditions of a two-way movement actuator made of one-way shape memory alloy (OWSMA) for versatile ventilation intelligent garments. To develop a low-power actuator that consumes energy only when a garment changes its form such as opening and closing, multiple channels of OWSMA were used, and optimum diameter of the wires was examined. For the switch device, optimum voltage application unit time was determined. Optimum diameter of OWSMA wire was determined by applying 3.7V to the pre-determined candidate diameters, which demonstrated two-way operation in previous studies. In order to evaluate the optimum voltage application time, the internal diameter of the actuator was measured while increasing and decreasing by 50 ms from the unit time of voltage application. Delay time under two-way operation of the actuator was measured to minimize interference caused by heat between channels. Power of 3.7V was applied to OWSMA for assessment of optimal time, and the whole process from heating to cooling was video-recorded with a thermal image camera to determine the point of time at which the temperature of OWSMA wire dropped below the phase transformation temperature. The results showed that $0.4{\Phi}$ was the most suitable diameter, and the optimum unit time of voltage applied to open and close the actuator was 4100ms. It was also shown that the delay time should be more than 1.8 seconds between two-way operations of the actuator.

• Journal of Convergence for Information Technology
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• v.10 no.7
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• pp.33-40
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• 2020

This work tackles the problem of conventional reinforcement learning scheme which has a relatively long training time to reduce energy consumption in underwater network. The enhanced scheme adjusts the learning range of reinforcement learning based on distance estimation. It can be reduce the scope of learning. To take account the fact that the distance estimation may not be accurate due to the underwater wireless network characteristics. this research added noise in consideration of the underwater environment. In simulation result, the proposed AQ-NAV scheme has completed learning much faster than existing method. AQ-NAV can finish the training process within less than 40 episodes. But the existing method requires more than 120 episodes. The result show that learning is possible with fewer attempts than the previous one. If AQ-NAV will be applied in Underwater Networks, It will affect energy efficiency. and It will be expected to relieved existing problem and increase network efficiency.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.1
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• pp.51-56
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• 2019

This paper related with the performance comparison of CCA and RMMA blind adaptive equalization in order to reduce the intersymbol interference which is occurred in channel when transmitting the 16-QAM signal, high spectrum efficiencies of nonconstant modulus characteristic. The CCA possible to improve the misadustment and initial convergence by compacting the every signal constellation of 16 by using the sliced symbol of the decision device output, namely statistical symbol, but incresing the computational cost. The RMMA possible to minimize the fast convergence speed and misadjustment and channel tracking capability without increasing the computational cost by obtain the error signal after transform to 4 constant modulus signal based on the region of signal constellation located. In this paper, these algorithm were implemented in the same channel, and the blind adaptive equalization performance were compared using the equalizer output signal constellation, residual isi, MSE, SER. As a result of simulation, the RMMA has better performance in output signal constellation, residual isi and MSE compared to the CCA, but has slow convergence speed about 1.3 times. And the SER performance presenting the robustness to the noise signal, the CCA has more beeter in less SNR, but the RMMA has better in greater than 6dB in SNR.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.4A
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• pp.352-360
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• 2008

Recently Task Group (TG) 4 of the Institute of Electrical and Electronics Engineers (IEEE) 802.15a has been recommended a system with ranging capability in existence of multiple Simultaneous operating piconets (SOPs) as well as low-cost, low-power. According to the ranging service, coherent and non-coherent based ranging schemes using ternary code have been adopted as a standard. However it is hard to estimate an accurate time of arrival (TOA) in case of using direct sequence based TOA estimation method because pulse repetition interval (PRI) offered by TG is more limited than the maximum excess delay (MED) of channel. To mitigate inter pulse interference (IPI) problem, this paper proposes a non-coherent TOA estimation scheme using non-periodic transmission (NPT) pattern. The proposed receiver is based on a non-coherent energy detection considering with motivation of low rate wireless personal area network (LR-WPAN). TOA information is estimated via proper comparison with a prescribed threshold after the sliding correlation and search back window (SBW) process for reducing TOA error. To verify the performance of proposed ranging scheme, two distinct channel models approved by IEEE 802.15.4a TG are considered. According to the simulation results, we could conclude that the proposed scheme have performed better performance than the conventional method on the existence of multiple SOPs.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.5B
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• pp.859-870
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• 2000

In this paper, an efficient H/W implementation technique for guard interval in OFDM(Orthogonal Frequency Division Multiplexing) systems is proposed and applied to ASIC chip design of an OFDM-based 25 Mbps wireless ATM modem. In OFDM systems, a cyclic prefix, longer than the largest multipath delay spread, is usually inserted to maintain the orthogonality of subchannels, by making the linear convolution of the channel ok like circular convolution inherent to the discreate Fourier domain, as well as to prevent the ISI(Intersymbol Interference) within the OFDM block. However, the OFDM system using the cyclic prefix requires an additional H/W in transmitter in order to store the original samples and to append the cyclic prefix to the beginning of each block. In this paper, a new approach using a cyclic prefix, even with a significantly lower H/W complexity. Finally, the performance of the proposed approach is demonstrated by applying it to ASIC chip design of an OFDM-based 25 Mbps wireless ATM modem.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.4
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• pp.105-117
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• 2015

In this paper, we consider 19 cells with the two tiers for polar-rectangular coordinates (PRCs) and provide the cell edge performance of cellular networks based on distance from cell center i.e., BS (base station). When FFR is applied(or adopted) to cell edge, it is expected that BS cooperation, or a coordinated multipoint (CoMP) multiple access strategy will further improve the system performance. We proposed a new method to evaluate the sum rate capacity of the MIMO DC of multicell system. We improve the performance of cell edge users for intercell interference cancelation in cooperative downlink multicell systems. Simulation results show that the proposed scheme outperforms the reference schemes, in terms of cell edge SINR (signal-to-interference-noise ratio) with a minimal impact on the network path loss exponent. We show 13 dB improvements in cell-edge SINR by using reuse of three relative to reuse of one. BS cooperation has been proposed to mitigate the cell edge effect.