Chapter 1 Performance of Passive UHF RFID Systems in Practice

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Chapter 1 Performance of Passive UHF RFID
Systems in Practice

• RFID Systems Research Trends and Challenges
• Slides prepared by Dr. Miodrag Bolic

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Study objectives

• Problems with RFID systems from simple to complex
• We will focus mainly on long-range UHF systems
• Understand interference, sensitivity to
  orientation and environment, missed tags,
  unwanted reads

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Problems in RFID system

• Consider the following situations with increasing
  levels of complexity
• One stationary reader and one stationary tag
• One stationary reader and multiple stationary
  tags
• Two stationary readers and one or more stationary
  tags
• One mobile reader and several stationary tags
• Large system with several mobile and stationary
  readers and many tags

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Problems

• Read ranges
• Read rates
• Tag separation
• Interference
• Deployment of large RFID systems
• Analysis of data
• Software and integration
• Security

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Problems stationary systems

• One stationary reader and one stationary tag
• Problems
• Lack of well defined reading zone
• physical orientation of tags
• nature of the object the tag is placed on
• the environment

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Read range

• Maximum distance between the tag and the antenna
  where the tag can be read by the reader.
• Blind spot is defined as the tag is in the
  reading range but unable to response
• Affected by the following parameters of reader
  and tag
• Reader antenna gain
• Tag antenna gain
• Reader output power
• Appropriate data coding scheme and modulation
• Environment
• ...

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Sensitivity to tag orientation
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Problems stationary systems 2

• One stationary reader and multiple stationary
  tags
• Problems
• Previously introduced non-idealities
• Effect of collisions among tags
• Sensitive to proximity of other tags

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Problems stationary systems 3

• Multiple stationary readers and one or more
  stationary tags
• Problems
• Previously introduced non-idealities
• Reader-to-reader interference
• Reader-to-tag interference
• Unwanted reads

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Reader Density
DOCK 1
RECEIVING AREA
LEGEND
R
STORAGE AREA
From Presentation by Reva Systems
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Interference

• Reader to reader
• Dense-Reader Mode readers can detect weak tags
• amongst many strong readers
• Reader to tag
• Typical tags are not selective gt Susceptible to
  interference
• From far-away readers
• On channel or in different channels

From Presentation by Reva Systems
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Problems mobile readers

• One mobile reader and multiple stationary tags
• Problems
• Previously introduced non-idealities
• Missed tags
• Increased level of interference

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Problems complex RFID systems

• Multiple readers and many tags
• Complexity issues
• Software integration
• Networking
• Deployment
• Synchronization

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Analysis of information

• Functionality of RFID system
• Capture information.
• Manage information.
• Analyze information.
• Access information.
• Act on information and events.
• The amount of information is overwhelming
• Example major retail chain tagged all the items.
  If there are 10 billion items read every 5
  minutes, they will generate 15 Terabytes of data
  per day.

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Security

• Technical security is addressed in the Gen 2
  protocol
• Reader does not transmit electronic product
  code(EPC)
• Tag memory can be locked
• Access is password protected
• 32-bit access password
• Killcommand can permanently disable the Tag
• Protected by 32-bit kill password
• BUTSecurity really depends on us
• How much information do we want exposed?
• Public policy will decide the limits

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Study questions

1. How can one carry the item through the portal
   without being detected?
2. What is the blind spot?
3. Why dont RFID systems work reliably?
4. If we want to make sure that tags are read and
   deploy multiple redundant readers, what kind of
   problems will we introduce?