• Proceedings of the KIEE Conference
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• 2005.05a
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• pp.215-217
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• 2005

There are two types of packet loss probabilities used in both the network layer and the physical layer within the wireless transmitter such as a queueing discard probability and transmission loss probability. We analyze these loss performances in order to guarantee Quality of Service (QoS) which is the basic of the future network. The queuing loss probability is caused by a maximum allowable delay time and the transmission loss probability is caused by a wireless channel error. These two types of packet loss probabilities are not easily analyzed due to recursive feedback which, originates as a result at a queueing delay and a number of retransmission attempts. We consider a wireless transmitter to a M/D/1 queueing model. We configurate the model to have a finite-size FIFO buffer in order to analyze the real-time traffic streams. Then we present the approaches used for evaluating the loss probabilities of this M/D/1/K queueing model. To analyze the two types of probabilities which have mutual feedbacks with each other, we drive the solutions recursively. The validity and accuracy of the analysis are confirmed by the computer simulation. From the following solutions, we suggest a minimum of 'a Maximum Allowable Delay Time' for real-time traffic in order to initially guarantee the QoS. Finally, we analyze the required service rate for each type utilizing real-time traffic and we apply our valuable analysis to a N-user's wireless network in order to get the fundamental information (types of supportable real-type traffics, types of supportable QoS, supportable maximum number of users) for network design.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.3
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• pp.167-167
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• 2004

The system combined layered space-time processing and space-time trellis codes (STTC) provide high transmission rate as well as diversity and coding gain without bandwidth expansion. In this paper, two layered receiver structures are proposed. One is the LSTT-MMSE in which received bit streams are decoupled by interference nulling and then decoded by separate STTC decoders. The decoded outputs are cancelled from the received signal before advancing to the next layer detection. The other is LSTT-Whitening employing whitening rather than nulling. The receiver employing whitening process shows several advantages on diversity gain and the required number of receive antennas compare to the convolutional coded space-time processing. The proposed receivers use different decoding order scheme according to each interference suwression. The (4, 3) LSTT-Whitening receiver still achieves 1㏈ gain over the (4, 4) LSTT-MMSE and the (4, 4) coded layered space-time processing.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.38 no.6
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• pp.692-702
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• 2001

In this paper, a new block-matching algorithm for standard video encoder is proposed. The algorithm finds a motion vector using the increasing SAD transition curve for each predefined candidates, not a coarse-to-fine approach as a conventional method. To remove low-probability candidates at the early stage of accumulation, a dispersed accumulation matrix is also proposed. This matrix guarantees high-linearity to the SAD transition curve. Therefore, base on this method, we present a new fast block-matching algorithm with the slice competition technique. The Candidate Selection Step and the Candidate Competition Step makes an out-performance model that considerably reduces computational power and not to be trapped into local minima. The computational power is reduced by 10%~70% than that of the conventional BMAs. Regarding computational time, an 18%~35% reduction was achieved by the proposed algorithm. Finally, the average MAD is always low in various bit-streams. The results were also very similar to the MAD of the full search block-matching algorithm.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.3
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• pp.9-14
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• 2004

The system combined layered space-time processing and space-time trellis codes (STTC) provide high transmission rate as well as diversity and coding gain without bandwidth expansion. In this paper, two layered receiver structures are proposed. One is the LSTT-MMSE in which received bit streams are decoupled by interference nulling and then decoded by separate STTC decoders. The decoded outputs are cancelled from the received signal before advancing to the next layer detection. The other is LSTT-Whitening employing whitening rather than nulling. The receiver employing whitening process shows several advantages on diversity gain and the required number of receive antennas compare to the convolutional coded space-time processing. The proposed receivers use different decoding order scheme according to each interference suwression. The (4, 3) LSTT-Whitening receiver still achieves 1㏈ gain over the (4, 4) LSTT-MMSE and the (4, 4) coded layered space-time processing.

• Proceedings of the Korea Contents Association Conference
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• 2005.11a
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• pp.529-532
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• 2005

In anomaly intrusion detection, how to model the normal behavior of activities performed by a user is an important issue. To extract the normal behavior as a profile, conventional data mining techniques are widely applied to a finite audit data set. However, these approaches can only model the static behavior of a user in the audit data set This drawback can be overcome by viewing the continuous activities of a user as an audit data stream. This paper proposes a new clustering algorithm which continuously models a data stream. A set of features is used to represent the characteristics of an activity. For each feature, the clusters of feature values corresponding to activities observed so far in an audit data stream are identified by the proposed clustering algorithm for data streams. As a result, without maintaining any historical activity of a user physically, new activities of the user can be continuously reflected to the on-going result of clustering.

• The KIPS Transactions:PartB
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• v.12B no.5 s.101
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• pp.607-616
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• 2005

Due to the limited resources in thin-client and the large amount of computation for decoding MPEG media, it is not easy to support the QoS stream media to clients. To solve the problems, the terminal servers would be charged for decoding the MPEG media and thin-clients have a role to update only the changed areas in their screen. However, these previous approaches cause severely low video quality. In addition, since servers perform all procedures to decode MPEG media, they are easily saturated even under a small number of clients. In this paper, the sources of the low video duality are investigated in the previous thin-clients' solutions working in wireless and wired environments. From the detailed experiments, an intelligent media player is proposed to achieve the QoS streams by supporting both the enhanced video duality and the audio synchronized with video frames.

• Journal of KIISE:Databases
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• v.32 no.3
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• pp.285-296
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• 2005

In mobile distributed systems the data on the air can be accessed by a lot of mobile clients. And, we need an indexing scheme in order to energy-efficiently access the data on the wireless broadcast stream. In conventional indexing schemes, they use the values of primary key attributes and construct tree-structured index. Therefore, the conventional indexing schemes do not support content-based retrieval queries such as partial-match queries. In this paper we propose an indexing scheme, called B2V-Tree, which supports partial match queries on wireless broadcast data stream. For this purpose, we construct a tree-structured index which is composed of bit-vectors, where the bit-vectors are generated from data records through multi-attribute hashing.

• The KIPS Transactions:PartC
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• v.14C no.1 s.111
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• pp.55-64
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• 2007

Behind the popularity of VoIP in these days, it may present significant security challenges in privacy and accounting. Authentication and message encryption are considered to be essential mechanisms in VoIP to be comparable to PSTN. SIP is responsible for setting up a secure call in VoIP. SIP employs TLS, DTLS or IPSec combined with TCP, UDP or SCTP as a security protocol in VoIP. These security mechanisms may introduce additional overheads into the SIP performance. However, this overhead has not been understood in detail by the community. In this paper we present the effect of the security protocol on the performance of SIP by comparing the call setup delays among security protocols. We implement a simulation of the various combinations of three security protocols and three transport layer protocols suggested for SIP. UDP with any combination of security protocols performs a lot better than the combination of TCP. TLS over SCTP may impose higher impact on the performance in average because TLS might have to open secure channels as the same number of streams in SCTP. The reasons for differences in the SIP performances are given.

• Parasites, Hosts and Diseases
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• v.56 no.3
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• pp.247-257
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• 2018

The aim of this study was to conduct a freshwater snail survey in Mae Lao agricultural basin to assess the diversity with a focus on habitat types and their larval trematode infections. Snails were collected and examined in 14 sites of Mae Lao agricultural basin from August 2016 to October 2017. A total of 1,688 snail individuals were collected and classified into 7 families, 8 genera, and 12 species. Snail diversity and habitat types were higher in rice paddies than irrigation canals and streams. The most abundant species was Bithynia siamensis siamensis, representing 54.6% of the sample. Three species of snails act as first intermediate host were found with cercarial infections. They were Filopaludina sumatrensis polygramma, B. s. siamensis, and Melanoides tuberculata. The cercariae were categorized into 7 types; echinostome, monostome, gymnocephalous, virgulate, parapleurolophocercous, pleurolophocercous and megalurous cercariae. Parapleurolophocercous cercariae constituted the most common type of cercariae recovered, contributing 41.2% of all infections in snails. Echinostome metacercariae infections were found in 6 snail species with 7.6% prevalence. In addition, the metacercaria of avian trematode, Thapariella sp. were found in Filopaludina spp. snails and B. funiculata with a prevalence of 0.5%. This is the first report for Thapariella metacercariae in the snail host, B. funiculata, and also confirmed that viviparid and bithyniid snails act as the second intermediate hosts of this trematode. This work will provide new information on the distribution and intermediate host of trematode in this area.

• Journal of Korean Society on Water Environment
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• v.26 no.1
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• pp.10-18
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• 2010

Water quality and the distribution of ammonia oxidizing bacteria were characterized in constructed wetland of Shihwa lake. Both physico-chemical parameters and fecal indicator microorganisms including total coliforms, E.coli, Enterococcus spp. were measured. In addition, denaturant gradient gel electrophoresis (DGGE) was carried out after PCR amplification of amoA gene from input, output, and wetland sites of the Banwol, Donghwa, and Samhwa stream in Shihwa lake area. Physico-chemical parameters were in proper range for typical nitrifying bacteria to grow and perform their biological activities. Average concentrations of fecal indicator microorganisms of wetland samples were lower than those of input sites. These results suggested that microbial water quality improved by the process of constructed wetland. According to phylogenetic information obtained from DGGE from study sites, distribution of nitrifying bacteria from each of input, output, and wetland were generally distinctive one another. In addition, distribution of nitrifying bacteria between Banwol and Donghwa streams showed higher similarity (52.6%) than this of Samhwa stream (15.2%). These results indicated that characteristics of ammonia oxidizing bacteria in Samhwa were unique in comparison with those of Banwol and Donghwa stream.