• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.8 s.350
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• pp.91-96
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• 2006

High efficiency switching mode circuits such as class I amplifiers have been well known in the MHz frequency range. The class E amplifier is a type of switching mode amplifier offering very high efficiency approaching 100%. In this paper, the class E amplifier has been designed by using the harmonic balance method of circuit simulator. The designed amplifier is realized by using pHEMT and microstrip line, shows 66% power added efficiency (PAE) at 2.4GHz with 17.6dBm output power. With -3dBm input power of wireless LAN, measured output spec01m can meet the required IEEE 802.11g standard spectrum mask. That means the required amplifier back off of 9dB from $P_{ldB}$ to satisfy the required wireless LAN spectrum mask.

• Journal of Internet Computing and Services
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• v.9 no.4
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• pp.85-96
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• 2008

An authentication procedure on wired and wireless network will be done based on the registration and management process storing both the user's IP address and client device's MAC address information. However, existent MAC address registration/administration mechanisms were weak in MAC Spoofing attack as the attacker can change his/her own MAC address to client's MAC address. Therefore, an advanced mechanism should be proposed to protect the MAC address spoofing attack. But, existing techniques sequentially compare a sequence number on packet with previous one to distinguish the alteration and modification of MAC address. However, they are not sufficient to actively detect and protect the wireless MAC spoofing attack. In this paper, both AirSensor and AP are used in wireless network for collecting the MAC address on wireless packets. And then proposed module is used for detecting and protecting MAC spoofing attack in real time based on MAC Address Lookup table. The proposed mechanism provides enhanced detection/protection performance and it also provides a real time correspondence mechanism on wireless MAC spoofing attack with minimum delay.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.9
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• pp.799-808
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• 2012

Bit operation of scrambler in the WAVE System become less efficient because parallel processing is impossible in terms of hardware and software. In this paper, we propose algorism to find the starting position of the matrix table. Also, when bit operation algorithm of scrambler and algorithms for matrix table, algorithm used to find starting position of the matrix table were compared with the performance as 8 bit, 16bit, 32 bit processing units. As a result, the number of processing times per second could be done 2917.8 times more in an 8-bit, 5432.1 times in a 16-bit, 10277.8 times in a 32 bit. Therefore, algorithm to find the starting position of the matrix table improves the speed of the scrambler in the WAVE and the receiving speed of a variety of information gathering and precision over the Vehicle to Infra or Vehicle to Vehicle in the Intelligent Transport Systems.

• Journal of Communications and Networks
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• v.18 no.2
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• pp.218-226
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• 2016

Coordination among users is an inevitable but time-consuming operation in wireless networks. It severely limit the system performance when the data rate is high. We present FC-MAC, a novel MAC protocol that can complete a contention within one contention slot over a joint frequency-code domain. When a node takes part in the contention, it generates randomly a contention vector (CV), which is a binary sequence of length equal to the number of available orthogonal frequency division multiplexing (OFDM) subcarriers. In FC-MAC, different user is assigned with a distinct signature (i.e., PN sequence). A node sends the signature at specific subcarriers and uses the sequence of the ON/OFF states of all subcarriers to indicate the chosen CV. Meanwhile, every node uses the redundant antennas to detect the CVs of other nodes. The node with the minimum CV becomes the winner. The experimental results show that, the collision probability of FC-MAC is as low as 0.05% when the network has 100 nodes. In comparison with IEEE 802.11, contention time is reduced by 50-80% and the throughput gain is up to 200%.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.2
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• pp.422-429
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• 2007

Location awareness is one of the key functionalities to build an U-city. Recently, many of works of the location-aware systems are emerging to commercially apply to on-going large-scale apartment complex based on U-city. As dwellers or cars being attached with active tags are moving in the U-city complex, the active tags periodically broadcast their own identifiers and receivers fixed along the street or in building use those information to calculate location of them. There are several issues to be considered for such an environment. The first is that the number of active tags operating in the same region are large as much as tens of thousands, and the second is that the active tags should be alive without change of batteries more than a year, hence low power consumption is very important. In this paper we propose i) a new architecture for location-aware system considering such issues, ii) technical issues to implement it using active tags, and iii) a mathematical analytic model to investigate overall performance and verify it by comparing with actual experimental results. Through the analysis we can show the theoretical boundary of the lowest packet loss rate and the maximum number of tags with acceptable performance for the systems based on active tags. The results can be applied to practical design of location-based systems of U-City projects.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.4A
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• pp.324-329
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• 2009

In this paper, a novel Snowflake-shaped microstrip patch antenna for application in the WLAN(5.2/5.8GHz) band is designed and fabricated. The size of antenna is $21.2{\times}16mm^2$ and substrate is used Taconic-RF30. To obtain sufficient bandwidth in Return loss <-10dB and dual resonance characteristic, the Short-pin is inserted on the patch and the coaxial probe source is used. The measured results of fabricated antenna show 220MHz and 135MHz bandwidth in Return loss <-10dB referenced to the WLAN(5.2/5.8GHz) band. The measured antenna gain is $4.7{\sim}6.9dBi$ in the WLAN(5.2/5.8GHz) band. The experimental 3-dB beam width in I-plane and H-plane are $73.2^{\circ}/82.75^{\circ}$ for 5.1500Hz, $74.56^{\circ}/83.63^{\circ}$ for 5.3500Hz, and $86.24^{\circ}/85.15^{\circ}$ for 5.7850Hz, respectively.