OBID i-scan APPLICATION-NOTE ID ISC.LRU2000 Dense Reader Mode draft public (B) 2007-05-31 N70300-0e-ID-B.doc
Copyright 2007 by FEIG ELECTRONIC GmbH Lange Strasse 4 D-35781 Weilburg-Waldhausen Tel.: +49 6471 3109-0 http://www.feig.de Note With the edition of this document, all previous editions become void. Indications made in this manual may be changed without previous notice. Copying of this document, and giving it to others and the use or communication of the contents thereof are forbidden without express authority. Offenders are liable to the payment of damages. All rights are reserved in the event of the grant of a patent or the registration of a utility model or design. Composition of the information in this manual has been done to the best of our knowledge. FEIG ELECTRONIC GmbH does not guarantee the correctness and completeness of the details given in this manual and may not be held liable for damages ensuing from incorrect or incomplete information. Since, despite all our efforts, errors may not be completely avoided, we are always grateful for your useful tips. The instructions given in this manual are based on advantageous boundary conditions. FEIG ELECTRONIC GmbH does not give any guarantee promise for perfect function in cross environments and does not give any guaranty for the functionality of the complete system which incorporates the subject of this document. FEIG ELECTRONIC call explicit attention that devices which are subject of this document are not designed with components and testing methods for a level of reliability suitable for use in or in connection with surgical implants or as critical components in any life support systems whose failure to perform can reasonably be expected to cause significant injury to a human. To avoid damage, injury, or death, the user or application designer must take reasonably prudent steps to protect against system failures. Use Exclusion in Transportation Market: Devices which are subject of this document may NOT be sold, used, leased, offer for sale, or otherwise transferred, exported, and imported by anyone in the Transportation Market. Transportation Market means (i) Electronic Toll and Traffic Management (ETTM), (ii) Public Sector Vehicle Registration, Inspection and Licensing Programs, (iii) Railroad Locomotive and Wagon tracking, (iv) airport based ground transportation management systems (GTMS) and taxi dispatch, (v) revenue based parking, and (vi) vehicle initiated mobile payment applications, where the RFID sticker/tag is initially attached to the vehicle but not incorporated at the point of vehicle manufacture. FEIG ELECTRONIC GmbH assumes no responsibility for the use of any information contained in this manual and makes no representation that they free of patent infringement. FEIG ELECTRONIC GmbH does not convey any license under its patent rights nor the rights of others. OBID and OBID i-scan are registered trademarks of FEIG ELECTRONIC GmbH. I-CODE is a registered trademark of Philips Electronics N.V. Tag-it TM is a registered trademark of Texas Instruments Incorporated. FEIG ELECTRONIC GmbH Page 2 of 15 N70300-0e-ID-B.doc
Contents 1. Normative references 4 2. Abbreviated terms 5 3. Introduction 6 4. European Regulations 7 5. US Regulations 9 6. Dense Reader Mode 10 6.1 Dense Reader Mode in Europe...11 6.2 Dense Reader Mode in the United States...12 7. Dense Reader Mode and Radio Frequency Regulations 13 8. Using the Dense Reader Mode with the LRU2000 14 8.1 Configuration of the European Reader...14 8.2 Configuration of the US Reader...15 FEIG ELECTRONIC GmbH Page 3 of 15 N70300-0e-ID-B.doc
1. Normative references EPCglobal TM : EPC TM Radio-Frequency Identity protocols Class-1 Generation-2 UHF RFID Protocol for Communications at 860MHz 960MHz, Version 1.1.0 European Telecommunications Standards Institute (ETSI), EN300220 (all parts): Electromagnetic compatibility and radio spectrum matters (ERM); Short Range Devices (SRD); Radio e- quipment to be used in the 25MHz to 1000MHz frequency range with power levels ranging up to 500mW European Telecommunications Standards Institute (ETSI), EN302208: Electromagnetic compatibility and radio spectrum matters (ERM) Radio-frequency identification equipment operating in the band 865MHz to 868MHz with power levels up to 2W, Part1 Technical characteristics and test methods European Telecommunications Standards Institute (ETSI), EN302208: Electromagnetic compatibility and radio spectrum matters (ERM) Radio-frequency identification equipment operating in the band 865MHz to 868MHz with power levels up to 2W, Part2 Harmonized EN under article 3.2 of the R&TTE directive U.S. Code of Federal Regulations (CFR), Title 47, Chapter I, Part 15: Radio-frequency devices, U.S. Federal Communications Commission FEIG ELECTRONIC GmbH Page 4 of 15 N70300-0e-ID-B.doc
2. Abbreviated terms CW DRM FDM ITF LBT RFID UHF Continuous Wave Dense Reader Mode Frequency Division Multiplexing Interrogator Talks First Listen Before Talk Radio-Frequency Identification Ultra High Frequency FEIG ELECTRONIC GmbH Page 5 of 15 N70300-0e-ID-B.doc
3. Introduction This document gives a short description of the Dense Reader Mode, which is used for communication in a radio-frequency identification (RFID) system, operating in a frequency range from 865MHz to 868MHz and 902MHz to 928MHz. A modulated RF signal in the named frequency range contains the information which are transmitted from the Reader to the Tag. The Tag receives the information as well as its operating energy from the UHF antenna. While the Reader is waiting for the Tags response, he is transmitting a continuous-wave RF signal to the Tag. The Tag response is formed by modulating the reflection coefficient of its antenna, at the same time backscattering an information signal to the interrogator. Only after being directed by an Reader the Tag modulates its antenna reflection coefficient with an information signal. This is called ITF - Interrogator Talks First. First this document explains the local regulations for Europe and the United States. After that it illustrates the need for a Dense Reader Mode and shows some theorectical basics. At the end the conformance with local regulations and the required settings for the LRU2000 are displayed. FEIG ELECTRONIC GmbH Page 6 of 15 N70300-0e-ID-B.doc
4. European Regulations The regulations for the use of an UHF RFID system in Europe are written down in the following document: ETSI EN302208 Electromagnetic compatibility and Radio spectrum Matters (ERM); Radio Frequency Identification Equipment operating in the band 865 MHz to 868 MHz with power levels up to 2 W; This document specifies, that in europe radio-frequency identification systems operating in the UHF range are only allowed to use 15 channels in a frequency range from 865MHz to 868MHz. The channels must be centered between 865,1MHz and 867,9MHz. The channel bandwith has to be 200KHz. In Channel 1 (865,1MHz), channel 2 (865,3MHz) and channel 3 (865,5MHz) the radiaded power should not rise over a level of 0,1 Watt (+20dBm). From channel 4 to channel 13 a maximum radiaded power of 2 Watt (+33dBm) is allowed. The channels 14 and 15 can transmit the information from Reader to Tag with an RF power of 0,5 Watt (+27dBm). Channel Number Center Frequency Maximum Power Level 1 865,1 MHz 0,1 Watt = +20dBm 2 865,3 MHz 0,1 Watt = +20dBm 3 865,5 MHz 0,1 Watt = +20dBm 4 865,7 MHz 2,0 Watt = +33dBm 5 865,9 MHz 2,0 Watt = +33dBm 6 866,1 MHz 2,0 Watt = +33dBm 7 866,3 MHz 2,0 Watt = +33dBm 8 866,5 MHz 2,0 Watt = +33dBm 9 866,7 MHz 2,0 Watt = +33dBm 10 866,9 MHz 2,0 Watt = +33dBm 11 867,1 MHz 2,0 Watt = +33dBm 12 867,3 MHz 2,0 Watt = +33dBm 13 867,5 MHz 2,0 Watt = +33dBm 14 867,7 MHz 0,5 Watt = +27dBm 15 867,9 MHz 0,5 Watt = +27dBm Table1: Channel plan for Europe FEIG ELECTRONIC GmbH Page 7 of 15 N70300-0e-ID-B.doc
Before a Reader starts transmission on a channel, he has to Listen if this channel is still available Listen Before Talk (LBT). This standard was developed under the assumption that the transmit and the receive signal of a system are located in the same channel. If two or more Readers would communicate on the same channel they would interfere each other and a proper data transfer between Tag and interrogator is not possible. Because there are only 10 channels for communication with high power (2 Watt), only 10 Readers can operate simultaneously in one area. Theoretical a distance of 7 kilometers has to be between two Readers using the same channel simultaneous. But through the attenuation of buildings and other hindrances the distance between two Readers using the same channel simultaneously and following the LBT rule is reduced to approximately 400 meters. Depending on the surrounding area this value would be different for each case. FEIG ELECTRONIC GmbH Page 8 of 15 N70300-0e-ID-B.doc
5. US Regulations In the United States the problem of multiple interrogator environments is already solved by the FCC. 50 channels are allocated in a frequency range between 902MHz and 928MHz. Each channel has a bandwith of 500KHz. The center frequencies are located between 902,75MHz (channel 1) and 927,25MHz (channel 50). On each channel a maximum power level of 1 Watt = +30dBm (4W EIRP) is allowed. Channel Number Center Frequency Maximum Power Level 1 902,75 MHz 1 Watt = +30dBm 2 903,25 MHz 1 Watt = +30dBm...... 1 Watt = +30dBm 50 927,25 MHz 1 Watt = +30dBm Table2: Channel Plan for the United States After a maximum time of 0,4 seconds the reader has to change his channel and starts hopping at random through the 50 channels. Nevertheless there is also a need for a Dense Reader Mode in the United States. The current existing regulations allow it to run more then ten Readers in an environment, but through the Hopping System the risk of channel collisions is rising with an increasing number of Readers. If a Reader wants to block a channel which is already used by another, the Reader will recognize an allocation and stops transmission for 0,4 seconds. This fact leads to a decline of the systems performance. FEIG ELECTRONIC GmbH Page 9 of 15 N70300-0e-ID-B.doc
6. Dense Reader Mode To solve the problem of operating a large number of Interrogators in an environment the Dense Reader Mode has been developed. In Dense Reader Mode all Interrogators use the same channel to transmit their information to a Tag. This fact requires that the Tag backscatter has to be seperated spectrally from the interrogators transmit signal. The Tag backscatter is seperated from the Interrogator transmit signal by a methode called Frequency Division Multiplexing (FDM). The information from the Tag is transmitted Miller coded on a subcarrier frequency. In this case every Bit, either 0 or 1,has to be confirmed and transimitted four times (M=4), until the Reader accepts it. To achieve the Return Link Bitrate the subcarrier Frequency has to be devided by four. With the LRU2000 operating in Dense Reader Mode a Return Link Bitrate of up to 80kbps can be achieved (320KHz / 4 = 80kbps). Figure1: Miller coded data Example: Center Frequency: Subcarrier: Backscatter Frequency: 865,7 MHz 320 KHz 865,38 MHz and 866,02 MHz Figure2: Separation of Interrogator transmit signal and Tag response FEIG ELECTRONIC GmbH Page 10 of 15 N70300-0e-ID-B.doc
A separation of Reader to Tag and Tag to Reader signaling is quite necessary, because not every Reader will send the same protocol with the same length and duration. If a Reader and a Tag are transmitting their data simultaneous with the same frequency both signals would interfere each. 6.1 Dense Reader Mode in Europe Because of the small channel bandwith in Europe the Tag response has to be located in the adjacent channels of the transmit channel. This assumes, that the adjacent channels could not be used for transmission from a Reader to a Tag. This leads up to a four channel plan, which says that only four channels instead of ten shall be used to transmit a signal from the Interrogator to a Tag. All Interrogators will use only one of these four channels (preferred channel). The other three channels act as fallback channel. The four channels are: Number Channel EN302208 Center Frequency 1 4 865,7 MHz 2 7 866,3 MHz 3 10 866,9 MHz 4 13 867,5 MHz Table3: 4 channel plan These high power channels are at least 600KHz away from each other. This frequency range is reserved for the Tag backscatter. Figure3: 4 channel plan FEIG ELECTRONIC GmbH Page 11 of 15 N70300-0e-ID-B.doc
6.2 Dense Reader Mode in the United States Because of the larger channel bandwith of 500KHz in the United States a separation of the Tag backscatter from the Interrogator transmit signal is possible inside the channel. The Interrogator transmit signal is centered in the channel, while the Tag backscatter is located at the edge of the channel. To avoid problems with the local regulations the hopping system keeps implemented. Each Interrogator has to change his transmit frequency after at least 400 milliseconds by hopping arbitrarily through the 50 channels. FEIG ELECTRONIC GmbH Page 12 of 15 N70300-0e-ID-B.doc
7. Dense Reader Mode and Radio Frequency Regulations The European Regulation (ETSI standard EN 302 208 [1]) says that certain rules have to be observed before a Reader is allowed to occupy a channel. First an Interrogator has to listen for a period of 5ms to make sure a channel is free. If the channel is available the Interrogator is allowed to occupy this channel and to transmit information for a maximum time of 4 seconds. The full requirement for this operation (LBT) is described in clause 4.1 of the standard (EN302208). This circumstance prohibits that a Reader can start transmission on the channel anytime when it is used by another RFID Reader. To solve this problem the Listen Before Talk process has to be synchronized for all Readers in the environment. The ETSI standard TS 102 562 Electromagnetic compatibility and Radio Matters (ERM); Improved spectrum efficiency for RFID in the UHF band; offers some possible solutions for synchronization. FEIG ELECTRONIC GmbH has developed a technique to synchronize the Listen Before Talk process for all Readers in the environment called the In-band radio approach. This methode is written down in the ETSI standard TS 102 562. The pre-pulse of the In-band radio approach is mandatory for all methods described in the standard. All Readers start listening at the same time and recieve the information that the channel is free at the same time, too. A precondition is that there are not any interferences on the channel from other devices like mobile phones. So each Reader will block the selected prefered channel at the same time and use it for transmitting information to a Tag. If the channel is already blocked, the Reader will select one of the available fallback channels. As the FEIG methode is described as In-band radio approach in TS 102 562 it is clearly shown that this methode is conforming to the EN 302208. FEIG ELECTRONIC GmbH Page 13 of 15 N70300-0e-ID-B.doc
8. Using the Dense Reader Mode with the LRU2000 The ID ISC.LRU2000 from FEIG Electronic is the first Reader on the market which supports the Dense Reader Mode. 8.1 Configuration of the European Reader To configure the Reader for operation in Dense Reader Mode please open ISO Start and go to the Configuration Register CFG3. In CFG3 select Mode 6: EN302208 4 Channel plan as region specific RF Regulation. Additional you have the possibility to select the number of used channels and to specify which channels should be used as preferred channels. Figure4: ISO Start CFG3 Channel Configuration for Dense Reader Mode FEIG ELECTRONIC GmbH Page 14 of 15 N70300-0e-ID-B.doc
To adjust the Bitrates for the Forward Link and the Return Link please go to CFG4. The Forward Link Bitrate could be set to the default value of 40 kbps. For the Return Link Bitrate it is necessary to select a Bitrate which is marked with DRM:. By choosing one of these Bitrates Miller Coding for the spectral seperation of Reader transmit signal and Tag backscatter is activated. The Reader will only run in Dense Reader Mode if Miller Coding is activated. For European Readers we recommend to use the Return Link Bitrate DRM:80kbps. Figure5: ISO Start CFG4 Bitrate Configuration for Dense Reader Mode 8.2 Configuration of the US Reader The settings for the operation of the LRU2000 FCC Reader in the Dense Reader Mode are quite simple. Configuration Register 3 (CFG3: RF-Interface) has to be configured in the same way as it was done before. In CFG4: Transponder Parameters a Return Linkk Bitrate of DRM: 64kbps is recommended. FEIG ELECTRONIC GmbH Page 15 of 15 N70300-0e-ID-B.doc