P1-18

Implementation of the ISO/IEC 18000-6 Type C Prototype Reader

Ki-Hwan Suh, Yong-Gu Jo, Young-Gon Hong, Kyung Sik Son, Hyoung-Nam Kim, Member, IEEEDept. of Electronics and Electrical Engineering, Pusan National University, Busan 609-735, Korea, E-mail:hnkim@pusan.ac.kr

Abstract Implementation of the ISO/IEC 18000-6 Type Cprototype reader is presented. The prototype reader may supportvarious RFID protocols and easily modify programs associatedwith communications between a reader and tags, such as an anti-collision algorithm, due to the function-based modular designwith the baseband board composed of FPGA and DSP.

I. INTRODUCTION

Radio frequency identification (RFID) systems haverecently drawn much interest in automatic identification fieldsfor replacing barcode systems. An RFID system consists of areading device called reader or interrogator and a number ofsmall devices known as tags which store data. An RFIDreader recognizes objects through wireless communicationswith tags attached to the objects [1]. Although RFIDtechnology is well-established at several different operatingfrequencies (e.g. 125 KHz, 13.56 MHz, 433 MHz), industryorganizations and standards bodies (e.g. EPC Global, ISO)around the world have given preference for adopting the UHFfrequency band (865-955 MHz) to most supply-chainapplications [2]-[4]. Compared with other automaticidentification systems, RFID possesses some advantages, suchas long-range, fast reading speed, low influence of directionand position, low operation cost, and no influence ofdegradation [ 1 ].

Despite the advantages, however, there still remains to besolved in practical use of UHF RFID systems. There havebeen two significant practical problems in UHF RFID systemsof the multi-tag identification time and the successful read rateof tags under severe RF environments [5]. To overcome thesetroublesome problems, a number of literatures have beenpresented [5]-[7].

However, most of these studies are based on computersimulation of UHF RFID systems. Since the computer-basedsimulation has some restrictions in reflecting diverse operatingRFID environments, developed algorithms or techniquesshould be verified through field tests of an actual RFIDsystem incorporating those developed methods. Though thereare a number of commercial UHF RFID readers in market,however, the commercial readers are not suitable for verifyingdeveloped algorithms or techniques because it is not allowedfor end users to upgrade the readers in firmware. To cope withthe practical problem in developing algorithms for enhancedRFID systems, we implemented a prototype reader which maysupport various RFID protocols and easily modify programsassociated with communications between a reader and tags.The flexibility of the implemented reader is due to thefunction-based modular design. There are two major modulesof FPGA and DSP in our reader. FPGA deals with various

This work was supported by the 2nd_Phase Brain Korea (BK) 21 Programfunded by the Ministry of Education, Korea.

Baseband Board

Command CRC Enoe_____ ,---~~--P- Enodr

Generator Encoder

DSP FPGA

IResponse CRC Decode

Unit Decodereoe-

RF BoardPulse

Shaping Modulator

Fig. 1. Block diagram of an ISO/IEC 18000-6 Type C reader and its classifiedmodules for hardware implementation.

protocols and DSP operates as a main processor by referringto programs in a programmable ROM. Since both the FPGAand the ROM can be repeatedly programmed, theimplemented prototype reader may provide an efficientplatform in developing enhancement algorithms for UHFRFID systems. Any developed anti-collision algorithms areeasily downloadable and verified by the field test using theimplemented prototype reader.

II. SYSTEM OF AN ISO/IEC 18000-6 TYPE C READER

A reader consists of digital part and analog part. Figure 1describes a data flow of an ISO/IEC 18000-6 type C readerand shows our classified modules for hardwareimplementation. The command generator produces propercommands which shall begin with either a preamble or aframe-sync. A CRC generator computes and adds either theCRC-5 or the CRC- 16 for the generated commands.Commands which are logical data sequences with CRC areencoded to pulse interval encoding (PIE) symbols. To satisfythe RF envelope of the ISO/IEC 18000-6 Type C protocol,output signal of the encoder passes through the pulse shapingfilter before RF up conversion. The modulator converts up thebaseband signals to double sideband amplitude shift keying(DSB-ASK), single sideband (SSB)-ASK or phase reversal(PR)-ASK modulation. After amplified by the power amplifierand driver amplifier, the modulated RF signal is transmitted totags by an antenna.

Received tags' replies which are backscattered RF signalundergo the transmission processes reversely. Afterdemodulating the tags' backscattered signals, the comparatordecides that the signal is whether high or low. The comparatoroutput data are transferred to the baseband part for basebanddecoding. The tag's signal is either FMO baseband or Millermodulation of a subcarrier encoding which is chosen by areader. The baseband decoder is composed of a preambledetector and a decoder which is designed to decode both ofencoding types. Except the general decoding procedure, thebaseband decoder also detects collision occurrences and no

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DC Power Input

UART

/ \DSP Rom

Fig. 2. Baseband board for the ISO/JEC 18000-6 type C prototype reader

replies. This information delivered to the response unit isessential for changing the slot-count parameter Q of the anti-collision algorithm in the ISO/IEC 18000-6 type C [2].Logical data from the decoder is verified whether there is a biterror or not by the CRC decoder. The response unit analyzingthe tags' replies, sends the proper corresponding to thecommand generator. All the above decoding processes are

repeated until identification of all tags are completed in theinterrogation area.

III. IMPLEMENTATION OF THE ISO/IEC 18000-6 TYPE CPROTOTYPE READER

Implementation of the ISO/IEC 18000-6 type C prototypereader is focused on testing various techniques including anti-collision algorithms for UHF RFID systems. In order to easilyverify a new anti-collision algorithm, the baseband board can

download the anti-collision algorithm to the ROM without any

effect on other operations. In order to support the otherprotocols in UHF RFID systems, the data encoder and decoderalso can be separately updated.

Figure 2 shows a photograph of the implemented basebandboard of the ISO/IEC 18000-6 type C prototype reader.Newly-developed anti-collision algorithms can be verified byimplementing that DSP contains the command generator andthe response unit operated by the anti-collision algorithm.Various protocols are supported by FPGA which contains theencoder, the decoder and the CRC block. There are twocommunication data rates between tags and the reader. One isa Tari value which is the reference time interval for reader-to-tag signaling and the other is a tag's backscatter linkfrequency (BLF). Both of the two data rates can be controlledin the baseband board of the reader. Communications betweenthe reader and the higher layer (e.g. MAC, PC) are performedthrough a UART port equipped at the baseband board.

Several passes exist in RF board shown in Fig. 3 for thedifferent pulse shaping filters of the different protocols.

IV. FIELD TEST

We performed field tests to verify the performance of theISO/IEC 18000-6 type C prototype reader. The antennainstalled to RF board is a circular polarized antenna for a

higher probability of a successful link. The parameters in thefield test were that the local frequency of the RF signal was

Fig. 3. RF board for the ISO/IEC 18000-6 type C prototype reader

908.5 914 MHz and the output power was 1W effective

radiated power (ERP). The field tests were taken in a

laboratory, a usual small office environment with computers,metal cabinets. The tags were stably identified in 5.1 meterswith multi-tag environment. The maximum range of the readerwas 6 meters.

V. CONCLUSIONS

We implemented the ISO/IEC 18000-6 Type C prototypereader which can serve a valuable role as a testing tool fordeveloping, verifying, and debugging various techniquesincluding anti-collision algorithms of UHF RFID systems.The implemented reader may ultimately support maximizingthe multi-tag reading performance by comparing differentanti-collision algorithms and then adopting the best algorithmfor the real hardware system. Other standard protocols ofUHFRFID systems may also be easily implemented at theprototype reader. With firmware upgrade of the basebandboard and a little RF board tune up, the prototype reader can

also support multi-band RFID protocols

REFERENCES[1] Klaus Finkenzeller, RFID Handbook, John Wiley and Sons, Inc., New

York, 1997.[2] Radio-frequency identification for item management - part 6C:

parameters for air interface communication at 860 MHz to 960 MHz,ISO/IEC_CD 18000-6C, January 2005.

[3] Information technology automatic identification and data capturetechniques - Radio frequency identification for item management airinterface - Part 6: Parameters for air interface communications at 860-960 MHz, ISO/IEC 18000-6, 26 November, 2003.

[4] Rich Redemske, Rich Fletcher, "Design of UHF RFID Emulators withApplications to RFID Testing and Data TransportOin Proc. IEEE 4thworkshop on Automatic Identification Advanced Technologies, Buffalo,New York, October 17-18, 2005, pp.193-198.

[5] D.-K. Kwon, W.-J. Kim, H.-N. Kim, "Improvement of Anti-CollisionPerformance for the ISO 18000-6 Type B RFID System," in The 2006International Technical Conference on Circuits/Systems, Computers andCommunications (ITC-CSCC 2006), Chiang Mai, Thailand, July 10-13,pp.11-37.

[6] Y.-J. Lee, D.-K. Kwon, H.-N. Kim, "Improvement of Collision-Arbitration for the ISO 18000-6 Type C RFID System," in The 2006International Technical Conference on Circuits/Systems, Computers andCommunications (ITC-CSCC 2006), Chiang Mai, Thailand, July 10-13,pp.11-153.

[7] Hush, Don R. and Wood, Cliff, "Analysis of Tree Algorithms for RFIDArbitration,OIn IEEE International Symposium on Information Theory,pages 107-. IEEE, 1998.

RF boardconnector

FPGA

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