• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.785-787
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• 2005

In the Bluetooth specification version 1.0, one specific frequency in one piconet was created depending upon the device clock and the Bluetooth native address at one specific time slot in the frequency hopping method. The basic hopping pattern was arranging the 79 ISM frequency band in pseudo-random fashion. Possible problem is the chance of collision of ownership of one specific frequency by more than 2 wireless devices when they are within the communication-active range. In this paper, we propose the adaptive frequency hopping method in order to resolve the possible problem so that more than 2 wireless devices communicates with their own client devices without being interfered. The proposed method was implemented with HDL later to be synthesized with an automatic EDA synthesizer and verified as well. The implemented adaptive frequency hopping circuit operated normally at 24MHz which will be the target clock frequency of the target Bluetooth device.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.1
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• pp.30-35
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• 2010

As of today, Frequency Hopping techniques are widely used for over-channel interference and anti-jamming communication systems. In this paper, analysis the performance of robustness on the focus of some general jamming channel. In FH/SS systems, usually SFH(Slow Frequency Hopping) and FFH(Fast Frequency Hopping) are took up on many special communication systems, the SFH, FFH are also combined with a channel diversity algorithm likes NED(Normalized Envelop Detection), EGC(Equal Gain Combines) and Clipped Combines to overcome jammer's attack. This paper propose Adaptive-NED and shows A-NED will be worked well than the others in the some general jamming environments.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.2
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• pp.237-241
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• 2005

In Bluetooth version 1.0, the frequency hopping algorithm was such that there was one piconet, using a specific frequency, resolving the frequency depending on the part of the digits of the device clock and the Bluetooth address. Basic pattern was a kind of a round-robin using 79 frequencies in the ISM band. At this point, a problem occurs if there were more than two devices using the same frequency within specific range. In this paper, we proposed a software-based adaptive frequency hopping method so that more than two wireless devices can stay connected without frequency crash. Suggested method was implemented with HDL(Hardware Description Language) and automatically synthesized and laid out. Implemented adaptive frequency hopping circuit operated well in 24MHz correctly.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.10 no.5
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• pp.396-401
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• 2017

In this paper, we propose a solution for interference with Bluetooth when connecting Bluetooth and other devices. The random frequency hopping technique is a technique of generating a hopping pattern using the entire Bluetooth channel without considering the interference of the wireless LAN. The proposed adaptive frequency hopping technique is a technique for generating a hopping pattern of Bluetooth channel considering periodic carrier sensing of Bluetooth and considering WLAN interference. Simulation results show that the use of adaptive frequency hopping reduces the packet error rate as the Bluetooth carrier sensing interval decreases even in the congestion of WLAN interference. Especially, the frequency hopping technique improves the average packet error rate by about 13% compared to the adaptive frequency hopping technique.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.7B
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• pp.706-718
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• 2002

In bluetooth system, there are two kinds of interference. One is the frequency static interference, for example 802.11 direct sequence, the interferer uses fixed frequency band. Another is frequency dynamic interference, for example other piconets or 802.11 frequency hopping, the interferer uses dynamic frequency channel and cant be estimated. In this paper we introduce a novel solution of hybrid method of Listen-Before-Talk (LBT) and Adaptive Frequency Hopping (AFH) to address the coexistence of bluetooth and Direct Sequence of wireless local area network (WLAN). Before any bluetooth packet transmission, in the turn around time of the current slot, both the sender and receiver sense the channel whether there is any transmission going on or not. If the channel is busy, packet transmission is withdrawn until another chance. This is the LBT in Bluetooth. Because of asymmetry sense ability of WLAN and bluetooth, AFH is introduced to combat the left front-edge packet collisions. In monitor period of AFH, LBT is performed to label the channels with static interference. Then, all the labeled noisy channels are not used in the followed bluetooth frequency hopping. In this way, both the frequency dynamic and frequency static interference are effectively mitigated. We evaluate the solution through packet collision analysis and a detail realistic simulation with IP traffic. It turns out that the hybrid method can combat both the frequency dynamic and frequency static interference. The packet collision analysis shows it almost doubles the maximal system aggregate throughput. The realistic simulation shows it has the least packet loss.

• Journal of information and communication convergence engineering
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• v.7 no.3
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• pp.399-403
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• 2009

In IEEE 802.15.1 (Bluetooth) Ad-hoc networks, the frequency is resolved by the specific part of the digits of the Device clock and the Bluetooth address of the Master device in a given piconet. The piconet performs a fast frequency hopping scheme over 79 carriers of 1-MHz bandwidth. Since there is no coordination between different piconets, packet collisions may occur if two piconets are located near one another. In this paper, we proposed a software/hardware co-design of an adaptive frequency decision mechanism so that more than two different kinds of wireless devices can stay connected without frequency collision. Suggested method was implemented with C program and HDL (Hardware Description Language) and automatically synthesized and laid out. The adaptive frequency hopping circuit was implemented in a prototype and showed its operation at 24MHz correctly.

• Proceedings of the Korea Information Processing Society Conference
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• 2006.05a
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• pp.1159-1162
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• 2006

본 논문에서는 Adaptive Frequency Hopping (AFH) 알고리즘을 사용하는 블루투스로 이루어진 피코넷이 Wireless Local Area Network (WLAN) 과 공존할 때 피코넷(Piconet) 패킷(Packet)간의 충돌 (Interference) 과 통합 처리량을 분석하였다. 동일한 주파수 대역의 Unlicensed ISM(Industrial, Scientific, Medical) Band를 사용하는 WLAN은 22MHz대역을 사용하기 때문에 AFH 알고리즘을 사용하는 블루투스와 공존할 경우 WLAN의 개수에 따라 홉 수가 달라진다. 본 논문에서는 멀티플 슬롯(Multiple-slot) 패킷을 사용하는 피코넷 클러스터(Piconet Cluster)의 패킷 충돌 모델을 가지고 AFH 알고리즘에 의해 서로 다른 홉(hop) 수를 갖게 된 피코넷의 패킷 충돌 확률과 통합 처리량을 전체 피코넷의 수를 증가시키면서 분석하였다.

• Proceedings of the IEEK Conference
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• 2002.06a
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• pp.137-140
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• 2002

2.4Ghz ISM 대역에서 동작하는 Bluetooth는 동일한 대역에서 동작하는 WLAN(802.11.b), Cordless phone, microwave oven등의 신호가 interference로 작용하여, 성능이 크게 저하된다. 특히 Bluetooth과 WLAN은 상호간 interference로 작용하여 상호 성능 저하를 초래한다. 따라서, 두 장치간의 coexistence를 위한 방안으로 adaptive hopping frequency(AFH)이 제안되었다. 이 논문에서는 3 channel status를 이용한 AFH 방식을 제안하고, 그 성능을 검증하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.8B
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• pp.1532-1539
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• 1999

In this paper, we propose a bit synchronizer which is suitable for frequency hopping systems. The proposed bit synchronizer is an ADPLL in which the digial loop filter is combined with an error symbol detecting circuit using an adaptive window. Suppressing the tracking process when hop mute and impulse noises are detected improves the performance of the digital loop filter and enhances the probability of the frequency hopping system. The simulation results demonstrate an improved performance of the proposed bit synchronizer compared with existing ones.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.9B
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• pp.604-611
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• 2007

In this paper, we present an analysis of the throughput when there are multiple piconets and WLAN sharing the ISM bands. The analysis takes channel propagation characteristics and the capture effect. We also propose an algorithm which can be used to reduce the amount of channel scanning. By using traffic prediction of the interfering WLAN, we are able to maintain a reasonable performance in terms of fraction of time channel is wasted due to collisions or unused channel. Through computer simulation, we demonstrate that the proposed algorithm achieves reduced scanning frequency.