Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Active_RFID_and_RTLS_MAC_and_PHY_Parameters] Date Submitted: [12 May, 2009”] Source: [Dalibor Pokrajac] Company [Guard RFID Solutions] Address [Add address Street, City, PC, Province/State, Country] Voice:[Add telephone number], FAX: [Add FAX number], E-Mail:[dalibor.pokrajac@guardrfid.com] Re: [Response to 802.15.4f Call For Applications] Abstract:[Discussion about active RFID MAC and PHY parameter requirements] Purpose: [To be considered during 802.15.4f standard development process] Notice: This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15. NOTE: Update all red fields replacing with your information; they are required. This is a manual update in appropriate fields. All Blue fields are informational and are to be deleted. Black stays. After updating delete this box/paragraph. Dalibor Pokrajac, Guard RFID Solutions

2. Active RFID / RTLSMAC/PHY Parameters Dalibor Pokrajac, Guard RFID Solutions

3. How is RFID / RTLS different than other communication technologies? • “Normal” comm. protocols provide a method (framework) for application data transfer. Active RFID / RTLS Tags often have little or no application data to transfer • There is very little content in communication layers above MAC • MAC (more or less) defines RFID/RTLS Tag functionality • Reliability of comm. channel is not always of utmost importance and can be sacrificed for communication efficiency and device simplicity • RTLS  Comm. reliability not critical • RFID  Reliability is critical for portal detection Dalibor Pokrajac, Guard RFID Solutions

4. Tag Density • Specifies number of tags per area or per Tag reader • Regardless of PHY used, it is desirable to minimize the time a Tag occupies a communication channel • To minimize interference with other Tags and other standards • To reduce transmit time (high current consumption mode) • It is not always desirable to maximize the link budget • Distant Tag transmissions may not contribute to location accuracy • Unnecessary Tag traffic contributes to Tag density • Tag traffic increase means increase in required Tag Reader processing power • Estimated maximum Tag Density requirements: • RTLS: 10 Tags per m2 • RFID Portal detection: 300 Tags per sec Dalibor Pokrajac, Guard RFID Solutions

5. Tag Blink Rate • Periodic Tag data transmission which provides Tag location information • Has significant impact on: • Location accuracy • Tag density • Battery life • Required Blink Rate is dependant on technology and use case: • UWB Tags tend to “blink” faster than UHF Tags • Some applications require faster Blink Rate than the others • Estimated requirements: Dalibor Pokrajac, Guard RFID Solutions

6. Data Rate • Very small amount of data is transferred in each transmission • Increase in data rate has consequences: • Realistic desirable data rate for narrowband UHF systems: • 250 – 500 kb/s • Faster  reduction in comm. range due to increase in PER • Slower  increase in current consumption due to longer TX time Dalibor Pokrajac, Guard RFID Solutions

7. Packet Length • Realistic packet length for active RFID systems : • < 10 bytes • Simplest MAC, only Tag ID, status bits and CRC are transmitted. • No preamble, no synchronization, no error correction. • Short Tag ID • 10-20 bytes • Contains elements of standard comm. protocol (synch, preamble, Tag ID, status byte(s), sensor data byte(s), CRC) • Realistic and most commonly used packet length for Beacon messages in UHF systems • > 20 bytes • Additional FEC, advanced addressing schemes, encryption, etc. • Packet length starts having negative effect on PER (and comm. range) • Potentially could be 15.4e packet Dalibor Pokrajac, Guard RFID Solutions

8. MAC Packet Fields • PHY related fields: • Synchronization • Preamble • Addressing fields: • Source address (Tag ID) is mandatory • Each Tag must have MAC address • Shortened MAC address (lower 3 bytes) can be used as Tag ID • Destination address is optional (2-way communication) • Additional data (Tag status and sensor data) • Optional with variable length • Data validation and security fields: • CRC  mandatory (validity of received data is critical) • FEC  optional (some message loss is acceptable) • Encryption  optional (Important for applications requiring data storage on a Tag) Dalibor Pokrajac, Guard RFID Solutions

9. MAC Requirements Summary The diversity of these requirements drives the need for Tag Classes • Optimal Blink rates for particular application • Fast (≤ 10 sec) • Medium (10 min) • Slow (6 hours) • Optional communication modes • “Transmit Only” Tags for systems closer to traditional RTLS and RFID systems • “2- Way” communication for systems bordering in functionality with sensor systems • Configurable packet length • Very short packets for traditional RTLS and RFID applications • Standard 802.15.4 packets for 2-way communication • Media access control is mandatory • CSMA • Clear Channel Assessment (for Transmit Only Tags) Dalibor Pokrajac, Guard RFID Solutions

10. Critical PHY Parameters • Pathloss • Higher pathloss  increase in power consumption  decrease of comm. range • Multipath and fading • Higher sensitivity to multipath impacts location accuracy • Modulation scheme • Increase in modulation complexity impacts cost and size • Appropriate PHY should provide reasonable location accuracy for realistic applications at reasonable cost Dalibor Pokrajac, Guard RFID Solutions

11. Thank You! Dalibor Pokrajac, Guard RFID Solutions

12. Backup Slides Dalibor Pokrajac, Guard RFID Solutions

13. Duty Cycle • Ratio between Tag’s “awake” mode and “sleep” mode • Duty cycle determines: • Tag acquisition time • Responsiveness to real time events (e.g. sensor data) • Location accuracy (beacon rate) • Typical active (UHF) RFID tag power consumption (3V battery): • Sleep mode: 0.5 µA • Average power consumption: 3V * 0.5 µA = 1.5 µW • Active mode: 3 µA in duration of 100 µs every 1 sec • Average power consumption: 3V * 3 µA * (100 µs / 1 s) = 0.9 nW • TX mode: 25 mA in duration of 1 ms every 10 sec • Average power consumption: 3V * 25 mA * (1 ms / 10 s) = 7.5 mW • Conclusion: • Tag Blink transmission current consumption is the dominant contributor to power consumption  Tag Blink Rate Dalibor Pokrajac, Guard RFID Solutions

14. Critical MAC Parameters • What Small and Inexpensive actually mean from technology point of view? • Minimized power consumption • Minimized processing power • Minimized hardware complexity • MAC defines critical active RFID / RTLS parameters: • Tag Density • Tag Beacon Rate • Tag Data Rate Dalibor Pokrajac, Guard RFID Solutions

15. Coexistence • Coexistence with other 802 standards : • Thousands and tens of thousands of Tags in small geographical area • Short, frequent, burst messages from RFID Tags do not mix well with long 802.11 messages or even 802.15 messages • “Listen Before Talk” is mandatory • CSMA • CCA • Global regulatory acceptability Dalibor Pokrajac, Guard RFID Solutions

16. Tag Classes Dalibor Pokrajac, Guard RFID Solutions