• Journal of KIISE:Databases
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• v.37 no.3
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• pp.171-175
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• 2010

This paper analyzes the tag data inconsistency problem caused by incomplete execution of the tag access operation to the RFID tag's memory and proposes a protocol to control consistent tag data accesses with finalizing the incomplete operation. Passive RFID tag cannot guarantee complete execution of the tag access operations because of uncertainty and unexpected disconnection of RF communications. This leads to the tag data inconsistency problem. To handle this, we propose a concurrency control protocol which defines incomplete tag operations as continuous queries and monitors the tags're-observation continuously. The protocol finalizes the incomplete operation when the tag is re-observed while it blocks inconsistent data accesses from other operations. We justify the proposed protocol by analyzing the completeness and consistency. The experiments show that the protocol shows better performance than the traditional lock-based concurrency control protocol.

• Proceedings of the KIEE Conference
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• 2008.04a
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• pp.67-68
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• 2008

본 논문에서는 수동 RFID 환경 아래서 공간/시간 정보를 효과적으로 활용하여, 기존 연구결과에 비해 추정 오차를 감소시킴과 동시에 경제성을 향상시키는 새로운 위치 추정 기법을 개발하고자 한다. 기본적으로 이동로봇이 일련의 직선 구간을 구간별로 정속 주행하며 또한 매 순간 이동로봇에 의해 감지되는 태그의 수는 한 개 이하라고 가정한다. 이러한 가정 아래서, 이동로봇이 위치 정보가 알려진 태그의 감지 범위를 경유하는 과정에서의 시간 정보를 이용하여, 주어진 구간에 대해서 이미 알려져 있는 지점을 출발하여 정속으로 직선 주행하는 이동로봇의 속도 및 위치를 추정하는 알고리즘을 개발한다.

• Proceedings of the KIEE Conference
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• 2008.10a
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• pp.109-110
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• 2008

본 논문에서는 900MHz RFID 수동형 태그 전치부를 설계하고 검증하였다. 문턱전압(threshold voltage) 제거 구조의 전압 체배기, 전류를 이용한 복조 회로로 설계되었으며 파워다운 회로를 추가하여 정류동작의 안정성에 중점을 두었다. PWM(Pulse Width Modulation)을 이용한 변조기를 구조로 입력단에 용량성 임피던스의 변화로 변조 동작을 검증하였다. 삼성 0.18um 공정을 이용하였고, 인식거리는 15m, 평균 소모 전력은 약 60uW이며, 패드를 포함한 칩 사이즈는 $1.22mm^2$이다.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.2
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• pp.32-43
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• 2004

RFID 시스템에서 태그는 리더와 전자기 에너지 교환에 의해 동작을 하며 배터리를 사용하는 active 형 태그와 배터리를 사용하지 않는 passive형 태그로 크게 구분된다. 또한 태그는 자체 회로구조에 의해 harmonic 태그, anharmonic 태그, sequenced amplifier 태그로 나뉜다. Passive 태그에서는 리더의 반송파 backscatter 방식을 이용하여 동작을 하며 active 태그는 자체 발진회로에 의해 태그정보를 송신한다. 태그의 변조방식으로 PSK, FSK, ASK 등을 사용하며 변조방법에 따라 회로 구성과 프로토콜 설계가 달라진다. 또한 리더의 전파 신호를 정류하기 위하여 렉테나(rectenna)가 필요하다. 본 논문에서는 태그의 분류, 동작, 구조 등에 관한 일반적인 내용을 기술하였다. 특히 UHF 대역 이상의 태그 기술 최근 추세가 안테나 부분을 제외하고 CMOS one chip화 하는 수준으로서 900 MHz UHF 대역, 2.45 GHz RFID 칩이 상용화 되어 있다. 칩의 내부구조와 태그의 변조방식에 의거한 동작에 관한 개괄적인 내용을 서술하였다.

• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.3145-3147
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• 2000

A passive RFID system consists of reader and tag. Reader is required the filter to modulate the data from backscattering signal which is transmitted by tag. The filter in the reader consists of envelope detector, amplifier, filter, and pulse shaping circuit, In this paper, design and analysis of filter in the RFID system which is operated at l3.56MHz carrier and 70KHz backscattering signal frequency is presented and is confirmed by simulation using Pspice.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.5C
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• pp.415-421
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• 2005

Passive RFID tag does not have its own power, so it has very poor computation abilities and it can deliver signals in very short range. From the facts, most RFID Tag security schemes assumed that the backward channel from tags to a reader is safe from eavesdropping. However, eavesdroppers near a tag can overhear message from a tag illegally. In this paper, we propose a method to protect the backward channel from eavesdropping by illegal readers. The proposed scheme can overcome the problems of conventional schemes such as randomized tree walking, which have been proposed to secure tag information in tree-walking algorithm as an anti-collision scheme for RFID tags. We showed the efficiency of our proposed method by using an analytical model, and it is also shown that the proposed method can provide the probability of eavesdropping in some standardized RFID tag system such as EPCglobal, ISO, uCode near to '0'.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.1
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• pp.63-70
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• 2015

In this paper, a receiver has been developed in a $0.11-{\mu}m$ CMOS technology for 900 MHz RFID communication system applications. The receiver is composed of an envelope detector, a low-pass-filter, a comparator, D flip-flops, as well as an oscillator to provide the clock for digital blocks. The receiver is designed for low power consumption, which would be suitable for passive RFID tags. In this circuit, a digital data slicer was employed instead of the conventional analog data slicer in order to reduce the power consumption. The clock frequency is 1.68 MHz and the circuit operates with a power consumption as small as $5{\mu}W$. The chip size is $325{\mu}m{\times}290{\mu}m$ excluding the probing pads.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2006.07a
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• pp.705-705
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• 2006

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.9
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• pp.67-74
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• 2016

This paper presents a novel multiple orthogonal subcarrier modulation based UHF band RFID communication system. In tag-to-reader communication, the demonstration system can deliver 1.6 Mbps through four subcarriers. To improve data rate while suppressing increase in circuit complexity, tag employs square-waves as the subcarriers and uses individual load modulators for each subcarrier. By using multiple orthogonal subcarrier based modulation, proposed communication system can be operated under existing UHF band RFID regulation. In reader, an OFDM demodulator is used. Since the tag backscatters the reader's CW carrier, carrier frequency offset compensation is not necessary in reader demodulator. Experimental results show that the demonstration system achieves a bit error rate of 10-5 at an Eb/N0 of 10.8 dB.

• Journal of Korea Multimedia Society
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• v.10 no.5
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• pp.623-630
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• 2007

With the development in IT technology and with growing demands of users, a ubiquitous environment is being made. Because of individuals identification is important in ubiquitous environment, RFID, a technology used frequently. RFID, a technology that radio frequency identification, reader send signer, then tag provide user information. RFID has various strengths, such as high recognition rates, quick recognition speed, but Eavesdropping is possible and problem that user information is revealed happens. To solve this, study is proceeded with activity, but, because of low-cost passive tag is limited operation capability, usually used hash function and random number. Also updates value that is used to present session and uses in next session. Therefore, this scheme protects user privacy using random number. And this sheme can offer synchronization by creating variable value without updating value.