Compiler & Microarchitecture Lab

Applying Passive RFID System to Wireless Headphonesfor Extreme Low Power Consumption

June 11th, 2008

Joon Goo Lee, Dongha Jung, Jiho Chu, Seok Joong Hwang, Jong-Kook Kim, Seon Wook KimSchool of Electrical Engineering, Korea University, Seoul, Korea

Janam KuSamsung Advanced Institute of Technology, Korea

Content

• RFID• Research Motivation• Design Possibility and Opportunity• Extended Gen2

– Features of the original Gen2 (ISO18000-6 Type C)– Added new commands for massive transferring to tags– Modified command and response: Write– Added new state and State transition of the EGen2

• EGen2 Prototype System– Overall verification system– EGen2 Sender System– EGen2 Receiver System

• Performance Evaluation• Conclusion

2

Content

• RFID• Research Motivation• Design Possibility and Opportunity• Extended Gen2

– Features of the original Gen2 (ISO18000-6 Type C)– Added new commands for massive transferring to tags– Modified command and response: Write– Added new state and State transition of the EGen2

• EGen2 Prototype System– Overall verification system– EGen2 Sender System– EGen2 Receiver System

• Performance Evaluation• Conclusion

3

RFID : Radio Frequency IDentificationRadio Frequency IDentification

• Identify objects from a distance by using a small IC with RF transponder

• RFID system is made up of three components– Transponder or tag, Interrogator or Reader, and Application

• Classification– SAW/Inductive/Modulated Backscatter/Active– Read Only/WORM/Reprogrammable/Read and Write– 125-135kHz/13.56MHz/UHF(300-1000MHz)/2.45GHz– Inductive/Electromagnetic (Narrowband, Spread Spectrum)

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General Use of RFID TechnologyGeneral Use of RFID Technology

• Inventory control• Container/Pallet Tracking• Access control• Equipment/Personal Tracking (In hospital, prison, etc.)• Product tracking through manufacturing, assembly,

and supply chain• Fleet maintenance• Various services by using mobile RFID

• Most applications are related to logistics and security.

5

Content

• RFID• Research Motivation• Design Possibility and Opportunity• Extended Gen2

– Features of the original Gen2 (ISO18000-6 Type C)– Added new commands for massive transferring to tags– Modified command and response: Write– Added new state and State transition of the EGen2

• EGen2 Prototype System– Overall verification system– EGen2 Sender System– EGen2 Receiver System

• Performance Evaluation• Conclusion

6

Motivation (1/2)

• When we use wireless communication device– Power consumption limits its usage!!!

Blu-ray Disc(54Mbps)

HDTV Video(15Mbps)

DVD Video(5Mbps)

MP3(192Kbps)

Bluetooth

10mW

50mW

100mW

200mW

Gen2/ NFC

Wibree

Zigbee20mW

30mW

40mW

150mW

250mW Wibro

750mW

500mW

1W

802.11x (Wi-Fi etc)

Low Power

Medium Power

High Power

PAN

WAN

LAN

3G HSDPA/ EVDO

DECT

Voice(64Kbps)

AC3(640Kbps)

Audio CD(1.4Mbps)

DTS Surround(1.5Mbps)

SBC(350Kbps)

10Kbps 1Mbps 10Mbps 100Mbps100Kbps

UWB

KleerSD H.264 Video

(1.5Mbps)

What is the wireless communication method which consumeslowest power?

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The answer is

Passive RFID!!

Motivation (2/2)

• A kind of energy harvesting technology is used in passive RFID system– However, RFID system has been only applied for

automatic data acquisition methods• Because of relatively lower data rate, security problem,

range of communication, power dissipation of memoryread/write, and so on

• What if a passive tag just bypasses the received data to other device, is it possible to use passive RFID technology for special purposes?– Data transmission system without storing the data– For an example, a headphone

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Content

• RFID• Research Motivation• Design Possibility and Opportunity• Extended Gen2

– Features of the original Gen2 (ISO18000-6 Type C)– Added new commands for massive transferring to tags– Modified command and response: Write– Added new state and State transition of the EGen2

• EGen2 Prototype System– Overall verification system– EGen2 Sender System– EGen2 Receiver System

• Performance Evaluation• Conclusion

9

Design Possibility and Opportunity (1/2)

• What kind of passive RFID protocol is sufficient?– We need

• High data rate: NFC, ISO18000-6 Type C (Gen2)• Long working range: ISO18000-6 series, ISO18000-3• Small size of device: ISO18000-6 series, ISO18000-3

– ISO18000-6 Type C is the best for the first step

• Feasibility checking with Gen2– Friss transmission equation was used for the calculation of path loss

– Assumptions• Reader transmits 10dBm power to tags• Antenna gain of the reader is 6dBi and antenna gain of a tag is zero• Efficiency of a tag rectenna is 80%• Half of the rectified power is available to the digital parts of a tag

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Design Possibility and Opportunity (2/2)

• The result of channel modeling for the passive RFID of 860~960MHz band from Friss equation and our assumptions

0.00

20.00

40.00

60.00

80.00

100.00

120.00

140.00

0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8

Dig

ital P

ower

(uW

)

Distance (m)

MP3(192kbps)

Voice(64kbps)

Audio CD(1.4Mbps)

SD H.264 Video

(1.5Mbps)

• From the above result, voice data and low quality music transmission is enough with Gen2

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Content

• RFID• Research Motivation• Design Possibility and Opportunity• Extended Gen2

– Features of the original Gen2 (ISO18000-6 Type C)– Added new commands for massive transferring to tags– Modified command and response: Write– Added new state and State transition of the EGen2

• EGen2 Prototype System– Overall verification system– EGen2 Sender System– EGen2 Receiver System

• Performance Evaluation• Conclusion

12

Extended Gen2 (1/4)

• Features of the original Gen2– Uses UHF (860~960MHz) band, backscatter modulation

• Forward modulation: DSB-ASK, SSB-ASK or PR-ASK• Backward modulation: ASK and/or PSK

– Data encoding: PIE for R2T, FM0 or Miller for T2R– Operating range: Several meters (Depends on Reader’s Tx power)– Tag size: Sufficiently small (It depends on antenna design)– Data link frequency: Relatively high

• Forward: 26.7kHz~128kHz• Backward: 40kHz~640kHz

– Supports multi-reader environment Session concept– Has 4 kinds of memory banks (One of them is EPC code)– Error detect: CRC5 or CRC16

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Extended Gen2 (2/4)

• Added new commands for massive transferring to tags– Burst command format and description

– BurstAckVS command format and description and its response format

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Extended Gen2 (3/4)

• Modified command and response: Write

– Write command was modified for writing ShortID in temporal memory• After Select operation, issue Write command in Ready state• After setting Membank, WordPtr, and RN as zero, assign ShortID reader wants

with lower 7bit of Data• After writing ShortID to temporal memory of Tag, the Tag responds CRC check

result of Write command and written ShortID

– There is no TREPLY (about 20ms) Reduce the power consumptionof the Reader

– Automatic ShortID initialization when tag is out of reading zone

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Extended Gen2 (4/4)

• Added new state

: Data

• The state transition diagram of the EGen2 tag– Fully compatible with original Gen2

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Extended Gen2 (appendix)• Supported communication methods and their procedure with EGen2 protocol

1. Broadcast– Send Burst command with ShortID=0000000b

• All tags in the reading zone process the Burst and BurstAckVS commands– When retransmission is unnecessary, reader omits setting ShortID

2. Multicast– Procedure

i) Inventory (Recognizing Tag ID)ii) Assert SL flag of wanting tagiii) Assign a unique ShortID to the tagiv) Choose wanting tags by repeating ii)~iii)v) Send Burst command with ShortID!=0000000b SL asserted tags process Burst and

BurstAckVS

3. P2P– Procedure

i), ii), iii) are same as Multicast procedureiv) Send Burst command with ShortID=the unique ShortID The tag which has the unique

ShortID processes Burst and BurstAckVS

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Content

• RFID• Research Motivation• Design Possibility and Opportunity• Extended Gen2

– Features of the original Gen2 (ISO18000-6 Type C)– Added new commands for massive transferring to tags– Modified command and response: Write– Added new state and State transition of the EGen2

• EGen2 Prototype System– Overall verification system– EGen2 Sender System– EGen2 Receiver System

• Performance Evaluation• Conclusion

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EGen2 Prototype System (1/5)EGen2 Prototype System (1/5)

• Overall verification system

– Sender was modified from an original Gen2 tag reader– EGen2 tag in receiver was extended from an original Gen2 tag– Audio signal sampling rate was 14kHz and resolution of each

sample was 8-bit

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EGen2 Prototype System (2/5)EGen2 Prototype System (2/5)• EGen2 Sender System

– Software processes the modified protocol– Command packet generation and response packet processing are done in hardware– Audio sampler was added to RFID reader for audio transmission– Analog part was omitted for fast verification

2020

EGen2 Prototype System (3/5)EGen2 Prototype System (3/5)• EGen2 Receiver System (1/3)

– EGen2 tag is for wireless communication– The rest parts are tag peripheral system for processing bypassed data from the

EGen2 tag

2121

EGen2 Prototype System (4/5)EGen2 Prototype System (4/5)• EGen2 Receiver System (2/3)

– EGen2 Tag architecture

• EGen2 tag was extended from the Gen2 tag which satisfies EPC Class-1 Generation-2 UHF (860~960MHz) RFID Protocol 1.1.0 version

• A power management unit generates 7 local clocks with clock-gating scheme and differentiates each clock phase to minimize the peak current

• We assumed that an analog front-end provides clock of 1.28MHz or 1.92MHz

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An

alo

g F

ron

t-E

nd

CLK(1.28/1.96MHz)

DIN

DOUT

Matched Filter/PIE Decoder

Miller Encoder(Miller <- NRZ)

Power ManagementUnit (clock gating)

Command Decoder/State Controller

Response Gen

EE

PR

OM

co

ntr

olle

r

CRC16

CRC16 CRC5

EEPROM RN16 Gen

PIE DecoderEngine

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EGen2 Prototype System (5/5)EGen2 Prototype System (5/5)

• EGen2 Receiver System (3/3)– Hardware Scheduler for low power

• Minimizing power consumption of receiver system by changingthe CPU’s power mode

• After AVR finishing the system initialization job as a general processor, the AVR changes its power mode to ‘Power-down Mode’ or‘Power-save mode’

• H/W Scheduler wakes up AVR by using external interrupt andresumes a job with the AVR

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Content

• RFID• Research Motivation• Design Possibility and Opportunity• Extended Gen2

– Features of the original Gen2 (ISO18000-6 Type C)– Added new commands for massive transferring to tags– Modified command and response: Write– Added new state and State transition of the EGen2

• EGen2 Prototype System– Overall verification system– EGen2 Sender System– EGen2 Receiver System

• Performance Evaluation• Conclusion

24

Performance Evaluation (1/2)

• Measurement Setup– We didn’t analyze the sender

– Gate level simulator was used for EGen2 tag and tag peripheral system• Synopsys Design Compiler and Synopsys VCS under Anam CMOS 0.18um

technology• We used Prime Compiler with 25% toggle rate for the EGen2 tag power estimation

• The number of gates and the power consumption of tag components except for EEPROM*– Gate increase: 3.5%

– Power increase: 3.8%

– Available distance: 1.8m

*: It is acceptable because EGen2 tag just bypasses the received data to tag peripheral system without writing the data into EEPROM

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Performance Evaluation (2/2)

• Tag peripheral system– Consists of AVR, DAC, hardware system which includes DAC FIFO,

two wrappers and a communication unit• The DAC FIFO consists of 8-bit 256 entries: 12K gates

• The rest of the hardware system: 5K gates

– The power consumption of the hardware system was 44uW– When wake-up duty of AVR processor was 1% (1% active, 99%

power save), 614uW was consumed

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Content

• RFID• Research Motivation• Design Possibility and Opportunity• Extended Gen2

– Features of the original Gen2 (ISO18000-6 Type C)– Added new commands for massive transferring to tags– Modified command and response: Write– Added new state and State transition of the EGen2

• EGen2 Prototype System– Overall verification system– EGen2 Sender System– EGen2 Receiver System

• Performance Evaluation• Conclusion

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ConclusionConclusion

• Contribution– EGen2 protocol

• EGen2 is a ultra low power wireless communication protocol which is based on passive RFID technology

– Feasibility of new use of passive RFID systems with EGen2 protocol• Digital parts of EGen2 tag consume 3.33 ㎼ (25% toggle rate) when the

tag receives audio data from a sender

– Prototype system by adding new hardware modules to the Gen2 reader and tag for our proposal

– Proposal of a hardware control interface, an inter-IP communication unit, and a hardware IP scheduler in order to achieve the low power consumption of whole receiver system

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Q&AQ&A

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