ODIN - EPC Generation 2 - the next step

CONFIDENTIAL DRAFTODIN technologies lab – Reston, VA

Trusted, Turn-Key RFID Solutions

EPC Generation 2.0: The Next Step

Why is it Better?and

What Should you do to Prepare for it?

12 January 2004

ODIN technologies laboratoryReston, VA

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Three Protocols + No Standard = Confused Users

The recent developments of the Electronic Product Code (EPC) system and the EPC RFID protocol have created a tsunami of activity in a previously stagnant RFID industry. Along with future promise comes present-day confusion: three distinct and mutually incompatible versions of “EPC compliant” tags exist today, early 2004, plus an emerging ISO standard. Most RFID end-users will want to uniquely identify and track their items using the most cost effective and efficient means possible. Three protocols will militate against such ideals and create unnecessary implementation problems in a global trading environment.

The problems developing are apparent in the compliance and interoperability areas.Using three different protocols would illogically create three different forms of technology based on the same concept. Each protocol would need its own unique set of readers, tags, and potentially networking methods. R&D costs would be unnecessarily high for manufacturers and hardware would be expensive for integrators (as three systems would be needed to serve each protocol). However, if one protocol is used for all future RFID technology, these unnecessary costs will be eliminated, and most importantly, global RFID adoption will occur at a faster pace. As of now, one global standard does not exist. EPC tag protocol Class 1 Generation 2.0 is the solution to this problem.

Primary Problem – Three incompatible standards

1. Class 02. Class 13. ISO Standard

The “acceptable protocols” today are defined as either Class 0 or Class 1 Identity tags and are open standards that any vendor can use to identify products. Also emerging is ISO 18000 standard. However, these protocol standards are not interoperable.

Currently, the Class 0 tag is a factory programmable tag disallowing an end-user to write a new number to the tag. Manufacturers are being allocated specific blocks of EPC numbers; and adding their own product codes and serial numbers to their assigned manufacturer numbers to create a unique identifier. Factory written tags increase administrative and logistics cost of affixing the correct tag to the correct item and minimize a tag’s flexibility. Should the user attempt to use unused tags, they could be stuck with a disorganized EPC address space, creating a host of network and identification related problems. Therefore Class 0 is only acceptable for closed or tightly managed systems.

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Class1 tags allow end-users to write serial numbers to their tags, but current Class1Generation 1.0 reader technology does not enable the communication with Class 0 tags. The other problem with Class 1 Generation 1.0 tags is there is only 64 bits of memory on the tag, limiting potential numbering schemes.

The emerging ISO standard has four primary components, but ISO-18000-6 is the one dealing with UHF range. The ISO standard differs from the EPC in that the ISO standard only addresses the air interface, how the tags and readers talk to each other and the EPC standard addresses other components of the system. The good news is that it will be compatible with the emerging Generation 2.0 protocol.

Generation 2.0 Why is it better?

The next generation of EPC protocol is better for three primary reasons:

1. It creates an interoperable, global standard,2. There are additional features making it technically more advanced,3. It uses more advanced anti-collision protocols for faster, more accurate

performance.

The Class1 Generation 2.0 protocol will be backward compatible for Generation 1.0 Class 1 and Class 0, and incorporate the specifications for both classes of tags. Class1 Generation 2.0 protocol will also operate with the emerging ISO18000-6 standard protocol, creating one global standard and enabling an efficient solution to the current lack of interoperability between Class 0 and Class 1 tags.

The Generation 2.0 tags will utilize four distinct memory banks:

1. Tag Identification 2. Object Identification (OID) – EPC Data3. User Memory and4. Reserved Memory

The OID memory stores the identifier of the object to which the tag is affixed and consists of a 16-bit protocol-control parameter, a 16-bit Cyclic Redundancy Check (CRC16), which ensures no errors in data have been communicated from a tag to a reader (with an accuracy rate of 99.998%), and an object identifier that is an N-bit EPC code (“N” is a valid EPC length). The tag identification memory and user memory are incorporated within the Generation 2.0 Class 2 Higher Functionality tags that allow tag and vendor-specific data storage. The tag identification memory stores the unique identifier for the tag, and the user memory allows user-specific memory storage. Reserved memory is used for system parameters such as password.

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Generation 2.0 Identity tags incorporate simple privacy functionality in the form of the Conceal function. Concealed tags will not communicate any of their memory contents unless the reader authenticates itself by issuing the password stored on the tag. The tags can also be unconcealed only if authenticated by the password. Adding to the strength of the security is a 16-bit random number generator (RN16) used to generate numbers for encryption of data communicated to the tag.

The flexibility of the EPC also ensures for future use and global uniqueness indefinitely. A 96-bit number enables the theoretical identification of nearly a million, trillion, trillion objects. To put this in perspective, if this many golf balls were placed next to each other, they would extend far beyond the edge of the known universe. If these golf balls were formed into a sphere, they would make an object six billion times larger than our sun. Considering that tagged items are most likely to be larger than golf balls, the industry believes that a 96-bit code will suffice for object identification.

Gen 2.0 Anti-Collision – No Hits, No Errors

Generation 2.0 EPC tags utilize an advanced and globally employable anti-collision technology enabling readers to identify tags in significantly shorter time periods than other existing protocols are capable of– this means faster, more accurate systems. When multiple RFID tags are communicating to a single reader and are in close proximity to each other, their signals can interfere with each other. This interference is called a “collision.”

Anti-collision methods can be broadly categorized into three domains: space, frequency, and time.1 The Generation 2.0 protocol development is based partially on a privately developed protocol from BTG, a British technology company credited with discovering interferon (a human protein) and magnetic resonance imaging. They have developed the “SuperTag” family of RFID protocols, which operates on the Aloha anti-collision principle, but incorporates further additions to make it amenable to RFID systems.

Passive RFID tags do not communicate with one another; therefore a tag cannot identify a collision of its communication. The reader must control the tags to “notify” them if the signal was successful or unsuccessful. In the SuperTags approach, tags continuously retransmit their identifier at random intervals until the reader acknowledges their transmission. After reception of tag data, tags can be muted or their repetition rate can be slowed. This method of muting a tag allows the proper counting of many tags in the same field. Another SuperTag variation involves the muting of all tags except the one being read. This ensures that no collision occurs. After a certain period, the muted tags are activated, one by one, until they are all counted. In other methods, the reader, by sending a gap or power burst, prompts the tags to respond after a randomly generated delay. Although high performance can be achieved via Aloha-based methods, they may not function as well as binary tree searches in high tag density environments.

1 See Appendix A

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Nearly all classes of anti-collision methods require the reader to detect tag communication collisions. Without such capability, even the best algorithms are useless. The new Generation 2.0 tags will use a slotted Aloha based algorithm to identify tags According to MIT’s Auto-ID Labs, this Generation 2.0 algorithm will enable a reader to interrogate greater than one thousand tags in less than a second with 100% accuracy, far better than any globally available solution today.

The Generation 2.0 protocol will revolutionize the RFID industry. There will be a single higher-performance protocol useable by all applications. If the technology is adopted, it will enable the interrogation of thousands of tags in seconds and make the older tags, which are still considered by the general public as advanced technology, obsolete. Generation 2.0 is faster, more universally accepted and will allow a global user base easier communication.

Tag protocols influence data transmission

The focus of this paper is on the tag protocol and the next generation of technology, however consideration must be given to how that data travels to various nodes. Effective long-term RFID architecture should be forward thinking in its design. For global adoption to be successful, users must implement a homogeneous network communication system using globally unique identifiers like the EPC protocol.

A much talked about, but so far still emerging solution is the “EPC network” using current Internet Protocol as its transmission layer. One credible alternative to EPC is to use address space from IPv6, the latest Generation of Internet Protocol. This address space is designed to use 128 bits. This lends the possibility of using IPv6 numbers as identifiers instead of EPC numbers; either 64-bit or 96-bit section would be allocated from the IPv6 address space specifically for use by EPC, or alternatively, companies could write tag IDs to RFID chips from their own IPv6 assignments. Regardless of which approach is taken, IPv6 would provide globally unique address space suitable for RFID tagging. Another simple strategy under consideration would be to create globally agreed upon headers that would identify the rest of the IPv6 number as an already-existing numbering scheme. For example a header of “01” may mean the next number will be a GTIN followed by a serial number, a “02” header could mean the Military’s Universal Identification protocol would be next. Through international registries of Internet numbers the header blocks would be assigned to ensure interoperability. This option is also under consideration within an EPC numbering scheme – adding just an identifying header followed by the UID, and is similar to how Wal-Mart wants their data formatted by applying specific values (16=GTIN, 17=SSCC, 18=GLN) as the header followed by GTIN, UPC, etc.2

2 ODIN technologies has patents pending for algorithms to automatically convert GTIN, SSCC, GLN, UID, etc. to EPC numbers and can provide software to fully automate the translation process.

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The Department of Defense has mandated that computing systems be IPv6 compliant by 4, 2006, and the Japanese government has mandated all Japan-based businesses to compliant by Q4, 2005. Much of Europe has also begun adoption of IPv63

making the protocol a credible global alternative to the current IPv4.

Although the future of technology is always unknown, EPC or a combination of EPC and IPv6, will be the most probable solution to RFID object labeling. The more bits a tag uses, the more expensive the tag is to produce. Therefore, it is imperative to create an economical global standard protocol for RFID technology; and the Class 1 Generation 2.0 EPC Identity protocol is the most realistic solution to the deadlines set by government agencies and large retailers.

User Recommendations

Based on what we know today about the change in protocol ODIN technologies recommends that as you refine your project plan for compliance, you pose the following four questions:

1. Have I started a dialogue with the older more established chip manufacturers?

2. Does my vendor(s) have a demonstrable path for upgrading to the Generation 2.0 protocol?

3. Does my contract with my vendor(s) have a Service Level Agreement, which protects me from additional cost associated with Generation 2.0?

4. Do I have a plan for translating my existing numbering scheme to EPC numbers and what is the cost in time and dollars for that migration?

Some estimates predict EPC Generation 2.0 tag technology will be available for production in less than a year. However since a new chip design is required, which is a significant process, that timing is unlikely. ODIN technologies’ lab estimates that broadly obtainable Generation 2.0 tags will not be available until sometime in early to mid ’05.

Established chip manufacturers will be the ones leading the way with Generation 2.0 tags since there is significant cost associated with designing this Generation 2.0 chip ($1-5 million according to various estimates). This design cost is much easier for a multi-billion dollar company to absorb than a new, venture-backed company. Therefore ODIN recommends opening a dialogue with the larger chip manufacturers if your project strategy calls for early deployment of Generation 2.0 tags. The newer companies, which have shown better tag performance, are working hard to be at the forefront but may be “out spent” by the larger better capitalized competitors.

3 ODIN technologies Director of IT, Nick Hilliard, deployed the first country-wide IPv6 network in Ireland in 2002.

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With Generation 2.0 tags likely becoming available after several looming deployment deadlines (Jan ’05 for Wal-Mart and potentially DoD), careful consideration should be given today to choosing a reader systems. Time should be spent over the 6-10 months designing and implementing the optimal reader architecture and tag placement to meet the 100% case and pallet read requirements that Wal-Mart and the DoD are mandating.

As part of a production system architecture, companies should choose reader manufacturers that can demonstrate today that their readers can be upgradeable via firmware to accept the new Generation 2.0 protocol. Several large companies have already made significant capital investments in hardware that is soon to be obsolete.

A system upgrade provision should also go into the purchase contract Service Level Agreement (SLA) either with the hardware manufacturer, or the integrator performing the installation, to ensure the timeliness of being Generation 2.0 compliant.

Once systems have been designed, tested, and deployed in the field with 100% accuracy, a structured plan should be implemented for translating existing numbering schemes (UPC, GTIN, SSCC, UID, etc) to EPC and then creating an infrastructure for management of the numbers and monitoring of the system.

The last step should be to evaluate how EPC will impact your current systems and what the costs of integration and scalability are. ODIN technologies will continue to leverage its portfolio of patent- pending technologies to create solutions to make these tasks easy for the end users.

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Appendix A: Anti-Collision DomainsA more detailed explanation of how anti-collision works

Space Domains

In space-domain methods, tags are placed in specific locations to achieve isolation. Tags in space-domain methods are identified by variation of reader range (variation of power is transferred to passive tags) and/or by using directional antennas (as opposed to omnidirectional antennae). Triangulation, using ultra-wide band communications and positioning methods, poses another possibility of locating individual tags. RFID identification using only space-domain methods drastically hinders the effectiveness of the technology. Directional antennas limit the space in which readers can communicate with tags; and without directional antennas, isolating a tag emitting a broad three-dimensional electromagnetic field limits the amount of tags that can be placed in a certain area. Space-domain methods rely on the amount of tags in a reader’s range—if there are too many tags in the area, collision will result and reduce the reader’s ability to interpret signals.

Frequency Domains

Frequency-domain anti-collision methods allow for robust wireless communications, but can add excessive complexity and cost to the tag. Frequency Division Multiple Access (FDMA) systems divide the total available bandwidth into fixed width channels. FDMA is costly because it requires accurate frequency sources and band-pass filters. One company has implemented a system combining FDMA with Time Domain Multiple Access (TDMA). While this system would undoubtedly perform well, the cost-effectiveness of this system is unclear. Code Division Multiple Access (CDMA) systems have many advantages over FDMA systems. CDMA offers better adaptability to varying traffic load, increased capacity to read tags, and processing gain. CDMA and other Spread Spectrum (SS) methods are currently difficult and costly to implement because of their increased complexity. Additionally, there are bandwidth limitations, and for this reason SS methods (including Frequency Hopping (FF) and Direct Sequence (DS)) are generally confined to operation in UHF and microwave bands.

Time Domains

Most RFID anti-collision methods are time-domain. In these methods, fractional communications from tags are varied in time. Time-domain methods can be classified into synchronous and asynchronous schemes. Synchronous schemes are those where a reader transmits a query to a specific tag using its UID (unique ID). This is an effective anti-collision method because tags do not have to “take turns” communicating to the reader, and tags do not have to rely on a complete “uncollided” transmission to be identified. A reader can poll through a list of tags, but the polling method, also known as

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tree walking or binary tree, is relatively time-consuming and depends on the tag’s UID number being known. Binary tree searches4 use binary code (groups of 0’s and 1’s) for communication and basically involve the reader actively sending a signal of a 1 or 0 to a tag. If the reader sends the correct number, the tag acknowledges it by transmitting the signal back to the reader. If the reader sends the wrong signal, the tag mutes itself and awaits another signal. Eventually, the computer deciphers the code of the tag.

To simplify the method of binary tree searching, imagine there is one tag in the field of an antenna. If the reader sends the correct number, either a 1 or 0, the tag acknowledges it by transmitting a signal back to the reader, and awaits another signal from the reader. The reader has two commands when sending out bit numbers—“DOWN” and “TOGGLE.” The “DOWN” command prompts the reader to send the same bit number as the last bit number, and the “TOGGLE” command prompts the reader to send the opposite bit number. The reader interrogates the tag randomly, resetting to zero when it sends the wrong bit. However, it only has to interrogate the tag 8 bits at a time, because after each byte (set of 8 bits) has been identified, the memory is stored, and the tag sets the next bytes first number to zero.

The binary tree searching method is more advanced when multiple tags are in an antenna’s field. Both the reader and tags act differently. In this method, a tag does not acknowledge the reader’s signal if the reader sends the wrong bit number. The reader will recognize this lack of communication and the tag will mute, reducing the chance of collision. When a tag is muted with the “FLAG” command, it sets a pointer to the beginning of the last byte identified. This way, the reader can partially interpret tags, 8 bits at a time. If a reader tried to decipher Generation 2.0 tags, 96 bits in a row, it would take an extraordinary amount of time. Eventually, through the random binary tree process, one tag remains un-muted, and the reader deciphers the code of this tag based on the method previously explained. Once this tag’s code is deciphered, it mutes itself and the reader subsequently sends an “UP” command to tell all muted tags (except the identified tag) to become active again. Another tag is discovered and the cycle repeats until all tags are read. Some binary tree searches use a more complex method of signaling groups of bits to detect tags. In deciphering code, this algorithm is surprisingly fast when compared to many time domain methods. Matrics tags use this anti-collision algorithm and ODIN technologies lab research has shown it to be an effective method for interrogating multiple tags at a fast rate. Matrics tags use this anti-collision algorithm and ODIN technologies lab research has shown it to be an effective method for interrogating multiple tags at a fast rate largely because of the wide bandwidth Matrics utilizes. This creates a problem, however in Europe where the constraints on the frequency band is much greater.

Asynchronous schemes are those in which tags in the reader’s field respond at randomly generated times. This helps to reduce the chance of collisions. The “Aloha5” scheme is asynchronous and involves a node transmitting a data packet after receiving a data packet. If a collision occurs, a node becomes saturated and transmits the packet again

4 See Appendix B for diagrams5 See Appendix B for diagrams

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after a random delay. The reader transmits continuously until a collision does not occur. In “slotted Aloha6,” transmission is performed in slotted times by making small restrictions in the transmission freedom of individual data packets. When packets collide under slotted Aloha protocol, they overlap completely instead of partially, and this significantly increases the efficiency of data transfer.

Aloha is more easily understood with an analogy. For the purposes of the analogy, imagine there are fifty tags in an interrogation zone. Imagine fifty railway stations as tags, a railroad car as a tag’s transmission, and two tunnels which represent the antenna/reader. A train gets loaded with supplies at its respective station (which is representative of the data being delivered) and once supplies are delivered through the tunnel, they are no longer needed, and thus the next train does not need to leave the station. One tunnel (the reader output tunnel) has trains coming out on one track, one behind the other, at constant speeds (this represents the electromagnetic waves being emitted by the antenna). At the fifty stations, the trains stop simultaneously, pick up their supplies, which takes a random amount of time (analogous to the random delay of Aloha protocol), and take off for the next tunnel. The tracks all converge at the one tunnel, however, and the trains cannot touch each other while merging, or the “collision” will destroy them; and thus no supplies will reach the other side (no data will be transferred to the reader). Trains will continue to leave stations until the supplies are delivered, and the station, receiving word from the “antenna/reader” tunnel, shuts down (representing a tag shutting off, or “muting” itself). The trains are long, and even though they move extremely fast, they sometimes overlap by random distances. The more trains there are leaving at random times, the more chance for collision.

This is representative of pure Aloha protocol. In slotted Aloha protocol, trains are only allowed to leave at certain times (slots). Imagine the stations have stoplights, and that all turn green and red at intervals just long enough to prevent partial train collision. If a train is ready to go at green, it goes, but if it is not, it must wait for the next light. This ensures that if two trains (signals) do go at the same time, they completely collide. If they overlapped (as they do with pure Aloha), the lagging train would still have the ability to collide with a train behind it. Now imagine the light flickers on and off multiple times per second, and the trains instantly accelerate to light speed. It may be easier to see how slotted Aloha is superior to pure Aloha. As stated before, once the train has delivered its supplies, it sends a signal so no train leaves its respective station; thus ensuring a smaller chance of collision.

6 See Appendix B for diagrams

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Appendix B - Diagrams

Diagram 1.1 gives a visual representation of binary tree searches.

Diagram 1.1ACK stands for “acknowledge”(FLAG) means the tag mutes itselfThe Up command prompts the reader to begin a tree search againThe Down command prompts to move down the command list (tree) and send a bitThe Toggle command prompts the reader to send a different bit

This diagram represents a hypothetical binary tree search when only two tags are in the field. The first tag mutes itself when it fails to receive the correct bit transmission from the reader. Once Tag2 is muted, it will not send any response to the reader, and will not react to any signal except the “Up” command, which will unmute it, and prepare it for data transmission. Note that the tags are only 8 bits long - any “Flag” command will bring the tag back to zero.

STEP 1

Tag 1 Tag2 Reader Command Tag1 Tag2

Down ACK ACK

1 Down ACK (FLAG)

Down ACK

Toggle ACK

Down ACK

Toggle ACK

Down ACK

Up ACK

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0

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0

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0

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0

0

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Diagram 1.2ACK stands for “acknowledge”The Down command prompts to move down the command list (tree) and send a bitThe Toggle command prompts the reader to send a different bitThe Done command prompts the reader to stop sending signalsThe “x” in the Tag1 bit locations represent that the tag is muted

STEP2

Tag1 Tag2 Reader Command Tag2

Down ACK

Toggle ACK

Toggle ACK

Down ACK

Down ACK

Toggle ACK

Down ACK

Toggle Done

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0

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x

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x

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Diagram 1.3- Representations of Pure Aloha ProtocolBlack rectangle represents successful transmissionWhite rectangle represents collision

Rectangles are Transmissions from tags traveling toward a reader

Tag 1 Transmission

Tag 2 Transmission

Tag 3 Transmission

Tag 4 Transmission

Time

Diagram 1.4- Representations of Slotted Aloha ProtocolBlack rectangle represents successful transmissionWhite rectangle represents collision

Rectangles are Transmissions from tags traveling toward a reader

Slot 1 2 3 4 5 6 7 8

Tag 1 Transmission

Tag 2 Transmission

Tag 3 Transmission

Tag 4 Transmission

Time

These diagrams show the difference between Pure Aloha protocol and Slotted Aloha protocol. To reiterate, in pure Aloha protocol, the transmissions overlap by random distances during collision, leaving the chance for infinitesimally small distances to completely disrupt tag interrogation. In slotted Aloha, transmissions overlap completely or not at all, and this increases the efficiency of data transfer.

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RE

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No overlap No overlap No overlap


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