• ETRI Journal
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• v.45 no.4
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• pp.570-580
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• 2023

Sensor nodes are the most significant part of a wireless sensor network that offers a powerful combination of sensing, processing, and communication. One major challenge while designing a sensor node is power consumption, as sensor nodes are generally battery-operated. In this study, we proposed the design of a low-power, long range-based wireless sensor node with flexibility, a compact size, and energy efficiency. Furthermore, we improved power performance by adopting an efficient hardware design and proper component selection. The Nano Power Timer Integrated Circuit is used for power management, as it consumes nanoamps of current, resulting in improved battery life. The proposed design achieves an off-time current of 38.17309 nA, which is tiny compared with the design discussed in the existing literature. Battery life is estimated for spreading factors (SFs), ranging from SF7 to SF12. The achieved battery life is 2.54 years for SF12 and 3.94 years for SF7. We present the analysis of current consumption and battery life. Sensor data, received signal strength indicator, and signal-to-noise ratio are visualized using the ThingSpeak network.

• ETRI Journal
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• v.28 no.5
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• pp.684-687
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• 2006

In this letter, we evaluate the system performance of a space-time block coded (STBC) multicarrier (MC) DS-CDMA system over a time selective fading channel, with imperfect channel knowledge. The average bit error rate impairment due to imperfect channel information is investigated by taking into account the effect of the STBC position. We consider two schemes: STBC after spreading and STBC before spreading in the MC DS-CDMA system. In the scheme with STBC after spreading, STBC is performed at the chip level; in the scheme with STBC before spreading, STBC is performed at the symbol level. We found that these two schemes have various channel estimation errors, and that the system with STBC before spreading is more sensitive to channel estimation than the system with STBC after spreading. Furthermore, derived results prove that a high spreading factor (SF) in the MC DS-CDMA system with STBC before spreading leads to high channel estimation error, whereas for a system with STBC after spreading this statement is not true.

• The Journal of the Convergence on Culture Technology
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• v.3 no.4
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• pp.191-198
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• 2017

In this paper, we compare the transmission performance of Code Division Multiple Access (CDMA) and Orthogonal Frequency Division Multiplexing (OFDM) under long duration multipath channel environments. This paper generates underwater channels through Bellhop based on the underwater environmental data of the west sea. BER performance of CDMA and OFDM are analyzed through various underwater channels based on the channels. Computer simulations result show that CDMA has better performance than OFDM when multipath delay time of underwater channel is shorter than spreading factor (SF). However, OFDM has better BER performance than CDMA as multi-path delay time increases.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.10
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• pp.3-12
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• 2013

Wireless Sensor Network (WSN) is used in the railway field in terms of efficient management and maintenance. Sensor communication technology based on IEEE 802.15.4/ZigBee is used in low speed train. However, it is difficult to apply in the high speed train that exposed to severe wireless channel environments. In this paper, we propose the sensor communication algorithm for high speed train environment. we improve error rate and throughput using Equalizer, Multiple Input Multiple Output (MIMO), Flexible Spreading Factor (SF) and Modulation. Also, we have analyzed the performance of the IEEE 802.15.4/ZigBee based on the standard of physical layer of 2.4GHz band in each algorithms. Simulation results show that proposed algorithms can improve error rate and throughput of conventional system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.6
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• pp.479-485
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• 2013

Recently, interest for wireless communication technology with improved security and low eavesdropping probability is increasing rapidly recognizing that information security is an important. Chaos signal can be used encode information efficiently due to irregular phenomena. Chaotic signal is very sensitive to the initial condition. Chaos signal is difficult to detect the signal if you do not know the initial conditions. Also, chaotic signal has robustness to multipath interference. In this paper, we evaluate the performance of correlation delay shift keying (CDSK) modulation with different chaotic map such as Tent map, Logistic map, Henon map, and Bernoulli shift map. Also, we analyze the BER performance depending on the selection of spreading factor (SF) in CDSK. Through the theoretical analyses and simulations, it is confirmed that Henon map has better BER performance than the other three chaotic maps when spreading factor is 70.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.3
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• pp.22-30
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• 2010

This paper proposes a combination system of Adaptive Modulation and Coding (AMC) and Multiple Input Multiple Output (MIMO), which improves the throughput and has a better reliability. In addition, the system includes Precoding, Antenna Subset Selection and MIMO Mode Selection scheme. Finally, we make a performance analysis of the proposed system. The principal environmental parameters for the simulation experiment consist of a frequency non-selective rayleigh fading channel and a Spreading Factor (SF) of 16. Other parameters may be included in order to fulfill the requirements of the HSDP A Standard. The proposed system has a higher throughput and more reliability than the conventional system, which does not include MIMO Mode Selection scheme, Precoding or Antenna Subset Selection. According to the simulation results, the proposed system reaches the maximum throughput at 8dB, presentlng an improvement of 6dB and twice higher throughput, respect to the conventional system. Specifically, at the point of -6dB, the conventional system reaches 2.5Mbps, while the proposed system reaches 6.4Mbps at the same SNR. Also, at the point of 2dB, each system reaches 7.5Mbps (conventional system) and 15.3Mbps (proposed system), with near twice the difference. According to the results exposed above, we can conclude that the system proposed in this paper has, as the greatest contribution, the improvement of the throughput, especially, the average throughput.