• Proceedings of the IEEK Conference
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• 2007.07a
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• pp.481-482
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• 2007

This paper demonstrates OFDM with adaptive modulation applied to Multiple-Input Multiple-Output (MIMO) systems. We apply an optimization algorithm to obtain a bit and power allocation for each subcarrier assuming instantaneous channel knowledge. The analysis and simulation is considered in two stages. The first stage involves the application of a variable-rate variable-power MQAM technique for a Single-Input Single-Output(SISO) OFDM system. This is compared with the performance of fixed OFDM transmission where a constant rate is applied to each subcarrier. The second stage applies adaptive modulation to a general MIMO system by making use of the Singular Value Decomposition to separate the MIMO channel into parallel subchannels. For a two-input antenna, two-output antenna system, the performance is compared with the performance of a system using selection diversity at the transmitter and maximal ratio combining at the receiver.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.4C
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• pp.330-335
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• 2008

This paper proposes a packet detection algorithm for IEEE802.11n system. IEEE802.11n is a multiple input multiple output (MIMO) system and we have to consider several combining techniques which are used in multiple receive antenna system. In this paper, we propose a hybrid packet detection algorithm which combines double sliding window algorithm or delay and correlation algorithm, that is used in single input single output (SISO) system, and multiple receive antenna combining algorithms, and simulated their performances in Iin system environments and shows the results.

• Animal Systematics, Evolution and Diversity
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• v.24 no.1
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• pp.9-16
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• 2008

Cerapus longicervicum, a new species of ischyrocerid amphipods, was isolated from the vicinal sea of Deokjeokdo-Island, Incheon (South Korea). This species is characterized by a narrower coxal plate width of gnathopod 1 in male, which is 0.39 times as broad as pereonite 1, and antenna 2, which is longer than antenna 1. This paper also provides the partial sequence of the mitochondrial cytochrome c oxidase subunit 1 (CO1) of the new species, which was obtained from a specimen that was preserved in 4% formalin solution.

• Animal Systematics, Evolution and Diversity
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• v.36 no.4
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• pp.363-371
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• 2020

A taxonomic study on bdelloid rotifers collected from mosses and/or leaf litter at four different locations in Korea resulted in five new Korean records and a new species, Philodina wonkimi n. sp. Philodina wonkimi n. sp. is easily distinguished from its congeners by the very long antenna which is much longer than the height of the pseudosegment carrying a dorsal antenna in creeping. Among the five new Korean records, two species- and two subspecies-level taxa are new to Asia as well. Adineta rhomboidea Bērzinš, 1950 has been reported from only three European countries including the type locality, and is recorded outside Europe for the first time. Present study is the fourth record for Philodina eurystephana Schulte, 1954. In addition, a partial sequence of mitochondrial cytochrome c oxidase subunit I gene (mtCOX1) for P. wonkimi n. sp. is provided here.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.12
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• pp.4600-4616
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• 2021

In cognitive radio networks where unlicensed secondary users opportunistically access to licensed spectrum unused by licensed primary users, spectrum sensing is one of the key issues in order to effectively use the frequency resource. For enhancing the sensing performance in energy detection-based spectrum sensing, spatial diversity based on multiple antennas is utilized. However, the sensing performance can be degraded when antennas are spatially correlated, resulting in inducing the harmful interference to primary users. To overcome this problem, in this paper, an advanced energy detector is proposed. In the proposed sensing method, a weight matrix based on the eigenvalues of the spatial channels without any prior information on the primary signals is defined and utilized. In numerical simulations, it is shown that the proposed detector outperforms the conventional detector with regard to false-alarm and detection probabilities when antenna are spatially correlated.

• Animal Systematics, Evolution and Diversity
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• v.22 no.2
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• pp.127-138
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• 2006

An ovigerous hair crab, Telmessus acutidens, was collected in South Korean waters and its larvae were reared in the laboratory. The larval development consists of four zoeal (including an extra zoeal stage) and one megalopal stages. Four zoeal stages are described and illustrated in detail. The zoeas of the present material show some differences from Kurata (1963)'s plankton-collected zoea of T. acutidens in the characteristics of the carapace spines, an endopod and an exopod of the antenna, and the posterolateral process of the abdominal somite. Kurata's zoea agreed well with that of T. cheiragonus. So, it is suggested that Kurata's zoea may be the second zoea of T. cheiragonus.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.2
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• pp.265-275
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• 2004

In this paper, an OFDM-CDMA broadband system is considered for a possible candidate of fixed wireless broadband access network applications. With an emphasis on a preamble design for multi-channel separation, we address a channel estimation based on the time-domain windowing and its imperfectness in OFDM-based multiple-antenna transmission systems. By properly designing each preamble for multiple antennas to be orthogonal in the time domain, the channel estimation can be applied to the ETSI HlPERLAN/2 and IEEE-802.11a standards in the case of more than two transmit antennas. Also, an effect of diversity techniques on the performance of OFDM-CDMA based broadband wireless access networks is investigated and the maximum achievable diversity gain for a two-path Rayleigh fading environment is evaluated Simulation results show that the OFDM-CDMA system applying a space-time-frequency diversity with a full-rate full diversity code can give the diversity of D = 4 and D = 8 for both multi-user cases of maximum user and half user capacities, respectively.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.15-18
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• 2005

Cooperative diversity is a transmission technique, in which multiple terminals pool their resources to form a virtual antenna array that realizes spatial diversity gain in a distributed fashion. In this paper, we propose a new type of cooperative transmission protocol with a full rate and show that its BER performance is improved by 8dB over the existing protocol under the AF (amplify-and-forward) mode of relaying.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.85-88
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• 2005

Space-time code is a good solution to get transmit diversity. During the last years a number of space-time block codes have been proposed for use in multiple transmit antenna systems. This code, however, was presented only for the special case of the certain numbers of transmit antennas and the certain modulation schemes. and designed under the assumption that the transmitter has no knowledge about the channel. In this work, on the other hand, we consider the case when the transmitter has partial, but not perfect knowledge about the channel. This system can have full diversity for arbitrary number of the transmit antennas with a little bits of feedback.

• 한국정보통신설비학회:학술대회논문집
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• 2009.08a
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• pp.329-332
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• 2009

In this paper, performance of cooperative communication system is analyzed with various relay conditions for mobile communication system using OFDM. We research mainly on the performance analysis of amplify-and-forward scheme. First, we analyzed the diversity gain between the number of antenna on the relay is one and two. And then, in this paper, we analyzed difference of the performance with distance between relay and mobile. Amplify-and-forward scheme has the problem that the noise components are also amplified in low sinal-to-noise (SNR) condition. The results of this paper can be applicable to the cooperative relay systems.