• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.1
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• pp.53-64
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• 2009

For a realization of the ubiquitous society, applying IT to vehicle industry has recently been an attractive issue to make wireless communication in body area network possible to everywhere. In this paper, we propose the physical layer symbol structure based on PPM scheme of the IEEE 802.15.4a for the off-body high data rate WBAN system. We propose four symbol structures which is classified according to the number of the chip and whether the channel coding is used or not. We calculate the required SNR through the link budget calculation and the recently proposed off-body WBAN channel environment was applied in the simulation. The results of four systems show that small number of burst's chip enhances the performance and the system is capable to achieve the data rate of 10 Mbps.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.2C
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• pp.145-152
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• 2009

Ultra-wideband communication systems for impulse radio have merits that are possible for either high resolution ranging system or radio determination. Conventionally, in order to accomplish these functions, the rapid analog to digital convertor (ADC) is necessary to apply radio determination system operating in time domain. However, considering that low rate - wireless personal area network (LR-WPAN) aims to low-cost hardware implementation, the expensive ADC converting GHz sampling per second is not appropriate. So, this paper introduces the high resolution ranging system operating in frequency domain with using low sampling rate ADC, and a new non-coherent ranging scheme utilizing analog Frequency Modulation (FM) mode for the frequency domain transformation. To verify the superiority of the proposed ranging algorithm working in frequency domain, the suggested IEEE 802.15.4a TG channel model is used to exploit affirmative features of the proposed algorithm with conducting the simulation results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.6C
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• pp.561-570
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• 2009

Ultra-wideband communication systems based on impulse radio have merits that are possible for the high data rate transmission, high resolution ranging are positioning system. Conventionally, in order to accomplish these features, the high-speed ADC (Analog to Digital Convertor) is necessary to apply radio determination system operating in time domain. However, considering low rate - wireless personal area network (LR-WPAN) aims to low-cost hardware implementation, the expensive ADC converting GHz sampling per second is not appropriate. So, this paper introduces a low complex AR (Auto Regressive) model based non-coherent ranging scheme operating in frequency domain with using low-speed ADC utilizing analog Voltage Control Oscillator (VCO) mode for the frequency domain transformation. To verify the superiority of the proposed ranging and location algorithm working in frequency domain, the suggested IEEE 802.15.4a TG channel model is used to exploit affirmative features of the proposed algorithm with conducting the simulation results.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.4 no.1 s.6
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• pp.63-71
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• 2005

This paper proposes the channel estimation method robust to severe frequency selective fading channels in O%M system using wide bandwidth for the high data rate transmission. DDCE, which uses data between the high correlated symbols, is usually used for channel estimation in the slow fading channels. DDCE can get high gains in the non-selective channels. As the bandwidth of system gets wider, it becomes more severe frequency selective fading environments so that the reliability of data becomes lower and error flow is occurred. FE method, this paper proposed, uses the relation between sub-carriers of OFDM in frequency selective fading channels so FE method gets some gains by adapting the power value at a target frequency to the mean value of channel estimated values of adjacent sub-carriers. Because FE uses only preamble unlike DDCE using data, it is independent of data rate related to the reliability of data and the number of multipath. Consequently, FE can obtain considerable gains in the wideband systems where the errorflow of DDCE is occurred, and FE is applicable to frequency selective fading environments.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.217-222
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• 2006

To find a location, GPS has been wildly used. But, it is hard to use in indoor because of very weak signal level. To meet indoor requirements, there have been many studies applying wireless communication networks such as WLAN, UWB and ZigBee. Among these, ZigBee is widely adopted in many WSN applications because it has an advantage of low-power and low-cost. In ZigBee, the RSSI is used as range measurement for ad-hoc network. The RSSI are converted to ranges using the signal attenuation model and these ranges become inputs of positioning methods. The obtained position with RSSI has large error because of its poor accuracy. To overcome this problem, ultrasonic sensors are added in many researches. By measuring the arrival time difference of ZigBee and ultrasound as a range measurement, the precise position can be found. However, there are still many problems: scheduling of beacons to transmit signals in a correct order, addition and synchronization of beacons and low-rate positioning rate. At this paper, an efficient method to solve these problems is proposed. In the proposed method, a node transmits ZigBee and ultrasound signal simultaneously. And beacons find the range with the received signals and send it back to a node with ZigBee. The position is computed in a node with the received ranges. In addition, a new positioning algorithm to solve the risk of the divergence in the linearization method and the singularity problem in the Savarese method is presented. Both static and dynamic experimental results show 0.02m RMS errors with high output rate.

• ETRI Journal
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• v.37 no.5
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• pp.929-939
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• 2015

Ultra-high-frequency radio-frequency identification (UHF RFID) is widely applied in different industries. The Frame Slotted ALOHA in EPC C1G2 suffers severe collisions that limit the efficiency of tag recognition. An efficient full-duplex anti-collision scheme is proposed to reduce the rate of collision by coordinating the transmitting process of CDMA UWB uplink and UHF downlink. The relevant mathematical models are built to analyze the performance of the proposed scheme. Through simulation, some important findings are gained. The maximum number of identified tags in one slot is g/e (g is the number of PN codes and e is Euler's constant) when the number of tags is equal to mg (m is the number of slots). Unlike the Frame Slotted ALOHA, even if the frame size is small and the number of tags is large, there aren't too many collisions if the number of PN codes is large enough. Our approach with 7-bit Gold codes, 15-bit Gold codes, or 31-bit Gold codes operates 1.4 times, 1.7 times, or 3 times faster than the CDMA Slotted ALOHA, respectively, and 14.5 times, 16.2 times, or 18.5 times faster than the EPC C1 G2 system, respectively. More than 2,000 tags can be processed within 300 ms in our approach.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.5
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• pp.32-39
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• 2009

Compressed Sensing is a method to sample analog signals at a rate under the Nyquist rate. With this scheme, it is possible to represent signals with a relatively smaller number of measurements than that of the conventional sampling method, and the original signals are reconstructed with high probability from the acquired measurements using the linear programming. Compressed sensing allows measurement time and/or the amount of ADC (analog-to-digital converter) resources for the signal acquisitions to be reduced. In this paper, we presents the backgrounds of the compressed sensing, a way to acquire measurements from an analog signal with a random basis, and the signal recovery method. Also we introduce applications of compressed sensing in wireless communications.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.11
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• pp.1159-1166
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• 2014

In this paper, a resource management scheme for enhancing the network connectivity and reliability in wireless USB system is proposed. Wireless USB protocol is suitable for the application that supports the real-time multimedia service in Ship Area Network since it supports high speed data transfer. However, the device's mobility is caused the dramatic change of link state and network topology, and is occurred the degradation of network performance. Therefore, a resource management scheme for wireless USB system is proposed in this paper. The proposed technique can intelligently treat the change of link state, and solve the degradation of network performance. The simulation results show that proposed protocol can enhance the throughput and delay performance by selecting relay device with better link state.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.12A
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• pp.1174-1182
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• 2005

This paper, we propose a new channel Estimation method for MB-OFDM(Multi-Band OFDM) system that is suggested as one of standards in IEEE 802.15 TG3a for high data rate(110Mbps${\~}$480Mbps) WPAN system. The proposed method uses correlation characteristic of the PS(Packet Synchronization) sequence for timing synchronization. It can reduce the influence of noise compared with the conventional algorithm which based on LS(Least square) algorithm is redundancy without using the CE(Channel Estimation) Sequence for channel Estimation. We simulate both conventional method and proposed method for performance analysis in S-V channel environment which proposed by IEEE 802.15.3a. Simulation results show the proposed algorithm outperforms conventional algorithm about 1${\~}$1.5dB of Eb/NO.