• International Journal of Contents
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• v.15 no.4
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• pp.27-35
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• 2019

In this paper, we propose an advanced Minimum Mean Square Error (MMSE) channel estimation method for IEEE 802.11p/Wireless Access in Vehicular Environments (WAVE) systems. To improve the performance of MMSE method, we apply the Weighted Sum using Update Matrix (WSUM) scheme to the step of calculating the instantaneously estimated channel and then, a time domain selectively averaging method is applied after the WSUM scheme. Based on that, the accuracy of instantaneously estimated channel increases and then, the accuracy of auto covariance matrix also increases. Consequently, we can achieve the performance gain over the conventional MMSE method. Through simulations based on the IEEE 802.11p standard, it is confirmed that the proposed scheme can outperform the existing channel estimation schemes.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.12
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• pp.4584-4599
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• 2021

In IEEE 802.11p-based wireless access in vehicular environments (WAVE) communication systems, channel estimation (CE) is one of the important issues to provide stable communication service. It is hard to apply conventional CE schemes based on data pilot to real systems, because error propagation occurs in high mobility and modulation order environments, resulting in degrading the CE performance. In this paper, we propose one data pilot using multiple receive antennas (ODPM) CE scheme based on the weighted sum using update matrix (WSUM) with time-domain averaging (TDA) to overcome this problem. Within the process of WSUM-TDA in the proposed scheme, the maximum ratio combining (MRC) technique is applied so as to create more accurate one data pilot. Moreover, a new reliability test criterion is proposed as the fashion of utilizing MRC, which makes it possible to apply selective TDA that guarantees performance improvement. In simulation results, the packet error rate (PER) performance of the proposed ODPM is compared with that of conventional CE methods and its superiority is demonstrated.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.17 no.1
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• pp.51-59
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• 2006

Objectives : Present study compared the characteristics in Rorschach responses and Sandplay between ADHD and normal children group. Method : ADHD (excluded inattention type & emotional problem) group and normal group was composed of 10 children respectively. All of them were controlled by Intelligence Quotation. Rorschach responses were scored by Exner system and compared by t-test. For sandplay work, the time was measured and photo was taken. Results : 1) ADHD group showed that the reaction time in Rorschach was significantly fast and they easily failed to recall the responses. The statical significances are 3r+ (2)/R, X-%, Xu%, (2), AG, Afr, SCZI, Wsum 6, FD, Zd, Blends, a. 2) ADHD group showed that the reaction time in Sandplay was significantly fast, they used low materials (total numbers of toy, vehicles) and the work was less coordinated. Conclusion : This results suggest that ADHD children are apt to react, think and coordinate impulsively. Also, Sandplay could be used fur diagnostic method as Rorschach test.