• Journal of the Institute of Electronics Engineers of Korea TC
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• 제43권11호
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• pp.54-67
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• 2006

Low Rate WPAN (Wireless Personal Area Network) designed for low power and low cost wireless communication is an important technology to realize ubiquitous environment. IEEE 802.15.4 and ZigBee Alliance recommend the SKKE (Symmetric-Key Key Establishment) protocol for key establishment and management. The SKKE algorithm has security weakness such as the absence of authentication process or electric signature in key generation and exchange when devices join the role of coordinators. In this paper, we propose new key establishment and security algorithm based on public key encryption to solve low rate WPAN security problems. Also, to improve PLC AMR system's weaknesses in communication reliability and security, we propose a new AMR system model based on IEEE 802.15.4 and we apply our security algorithm to AMR profile for security enhancement.

• Journal of the Institute of Electronics Engineers of Korea TC
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• 제47권9호
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• pp.19-28
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• 2010

The GTS(Guaranteed Time Slot) of the IEEE 802.15.4 standard, which is the contention free access mechanism, is used for low-latency applications or applications requiring specific data bandwidth. But it has some problems such as delay of service due to FIFS(First In First Service) scheduling. In this paper, we proposes a weight based GTS allocation scheme for fair queuing in IEEE 802.15.4 LR-WPAN. The proposed scheme uses a weight that formed by how much more weight we give to the recent history than to the older history for a new GTS allocation. This scheme reduces service delay time and also guarantees transmission simultaneously within a limited time. The results of the performance analysis shows that our approach improves the performance as compared to the native explicit allocation mechanism defined in the IEEE 802.15.4 standard.

• Journal of Korea Society of Industrial Information Systems
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• 제19권1호
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• pp.53-60
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• 2014

IEEE 802.15.4 is one of the most widely adopted physical layer standards in the area of LR-WPAN(Low-Rate Wireless Personal Area Network). Numerous previous researches have contributed to deep insights on energy efficiency, transmission throughput, and reliability that IEEE 802.15.4 delivers to the LR-WPAN. As a research that is orthogonal and complementary to previous researches, we explore the implementation and practical performance evaluation of IEEE 802.15.4 MAC software. We implement the MAC software from the perspective of the networking stack, exploring the issues raised when the MAC software serves as a functional component in a complete networking stack consisting of MAC, network as well as well as application support layers. The performance is evaluated on a realistic experimental software environment integrated with operating system, networking stack, and applications.

• The Journal of the Korea Contents Association
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• 제9권2호
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• pp.10-17
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• 2009

This paper analyze the effect of frequency offset for the IEEE 802.15.4b LR-WPAN(Low-Rate Wireless Personal Area Network) with 915MHz bandwidth noncoherent DSSS O-QPSK based receiver system, and presents a compensation method with addition of differential filter to the system for compensation of frequency offset problem. DSSS PSSS-ASK and DSSS O-QPSK modulation techniques are accepted within the regularization of IEEE 802.15.4b. These new method can obtain 250kbps transmission rate. The DSSS O-QPSK modulation method that is used in this paper has no BER variation below 40ppm(frequency offset 36.6kHz), but if the offset frequency become high above 40ppm, then the system cannot have stable receiving condition due to worse BER. To solve this problem, we present a more stabilized receiver system at maximum frequency offset ${\pm}80ppm$ using MDDF unti a correlator of DSSS O-QPSK modulator. Moreover computer simulation results will be presented to evaluate the performance of the proposed algorithm unde various AWGN and frequency offset environment.

• Journal of Advanced Navigation Technology
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• 제18권5호
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• pp.476-482
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• 2014

Recently, with the growth of various sensor applications, the need of wireless communication systems which can support variable data rate is increasing. IEEE 802.15.4 LR-WPAN system using 2.45 GHz frequency band is very popular for the sensor applications. However, since LR-WPAN only supports the data rate of 250 kbps, it has a limit to be applied to various sensor networks. Therefore, we define the preamble structure which can support the data rates of 31.25 kbps, 62.5 kbps, 125 kbps, and present the low-complexity hardware architecture for time synchronizer based on double-correlation algorithm which can resist the CFO (carrier frequency offset). Implementation results show that the proposed time synchronizer include the logic slice of 18.36 K and four DSP48s, which are reduced at the rate of 79.1% and 99.4%, respectively, compared with existing architecture.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제34권3B호
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• pp.255-263
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• 2009

In this paper, we propose an adaptive beacon scheduling algorithm to control a reception period of actual data according to variation of amount of traffic in IEEE 802.15.4 LR-WPAN(Low Rate-Wireless Personal Area Network) with the cluster-tree topology. If a beacon interval is shortened, the amount of the traffic a node receives can be increased while consumption of the energy can be also increased. In this sense, we can achieve optimal on orgy consumption by controlling the beacon interval when the amount of data to be received is being decreased. The result of simulation using NS-2 shows that the proposed algorithm improves performances in terms of packet loss rate and end-to-end delay compared with algorithm using a fixed beacon interval. For a design of cluster-tree based LR-WPAN managing delay-sensitive services, the proposed algorithm and the associated results can be applied usefully.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제35권1B호
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• pp.95-105
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• 2010

IEEE 802.15.4 is the one of the protocols for radio communication in a personal area network. Since it aims to provide low cost and low power communication for ubiquitous communication, it requires high level of optimization in implementation. Recently, there have been many studies on the performance evaluation of IEEE 802.15.4 MAC protocol. According to the results of the studies, it is tendency that the transceiver is implemented to SoC type. On the implementation, the specific functions of MAC like CSMA-CA and MAC frame handling is designed to hardwired functions. In this paper, we implemented the protocol with hardwired low MAC (HL-MAC) and its state machine for the optimization from the physical layer and MAC layer. it has the characteristics of the small code size and the enhanced power consumption.

• Journal of the Institute of Electronics Engineers of Korea TC
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• 제44권11호
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• pp.1-10
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• 2007

In this paper, we proposed channel estimation scheme for LR-UWB system which has low data rate for WPAN in IEEE 802.15.4a. At the transmitter, we proposed dynamic power level allocation depends on channel condition in specific period when we modulate signal. We use two orthogonal code to estimate channel at once. It can estimate channel more accurately by using two code which shows good correlation characteristic then it can estimate more accurately by spreading gain. Using estimated channel condition, we synchronize symbol timing of transmitted signal. Then determined power allocation scheme and channel information is transmitted to transmiter side. Finally, using these information, transmiter side change the power level of repeated pulse to adopt to channel condition. Simulation is performed under S-V channel for LR-WPAN in IEEE 802.15.4a and we compare the performance with a different type of receiver type. We use coherent and non-coherent method at the receiver. Simulation result shows us at the NLOS channal performance evaluation is greater than that of LOS channel and the result is independent of receiver type. In the NLOS channel, as the signal delay spreading is big, performance evaluation is also increased.

• Proceedings of the IEEK Conference
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• 대한전자공학회 2009년도 정보 및 제어 심포지움 논문집
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• pp.296-298
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• 2009

In this paper, we are performance analysis of IEEE 802.15.4b LR-WAPN(Low-Rate Wireless Personal Area Network; Zigbee) system noncoherent receivers at 915MHz under Jamming. IEEE 802.15.4b concerns itself with devices at 915MHz, which employ a higher data rate of up to 250 kbps, and which use O-QPSK(Offset Quradrature Phase Shift Keying modulation with DSSS(Direct Sequence Spread Spectrum). Communication between devices can still be hampered by the presence of interferers outside the network, whether the interference be intentional or not. Hence the receivers can not have stable receiving condition due to worse BER. To solve this problem, we present a mere stabilized receiver system of using noncoherent detection. In this paper, we look instead at the effect of jamming, i.e. intentional interference, on the BER performance of IEEE 802.15.4 devices.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제13권2호
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• pp.215-220
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• 2009

LR-WPAN(Low-Rate Wireless Personal Area Network) hewn as IEEE 802.15.4 is considered as one of the most suitable specifications published until now to accomplish USN(Ubiquitous Sensor Network). In this paper we simulate interference effects to other systems if LR-WPAN will be used in 900MHz. In considering the current usage situation of 900MHz frequency band, we can think LR-WPAN shares the frequency band of $908.5{\sim}914MHz$ assigned for RFID/USN. The simulation results of the case of LR-WPAN and RFID/USN sharing the frequency band show that the probability of interference of LR-WPAN to CT1 and RFID is 2.5% and 2.1%, respectively. In order to avoid interference effects to public communications, simulations results show that the protection distance of about loom is needed.