Chapter 1 Performance of Passive UHF RFID

Systems in Practice RFID Systems: Research Trends and

ChallengesSlides prepared by Dr. Miodrag Bolic

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

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

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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RECEIVING AREARECEIVING AREA

STORAGE AREASTORAGE AREA

DOCK 1

RRRR

RRRR

Reader-to-Reader Interference Zone

Reader-to-Tag Interference Zone

Interrogation Zone

LEGEND

Reader Density

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 => Susceptible to interference

– From far-away readers– On channel or in different channels

From: Presentation by Reva Systems

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

– “Kill”command can permanently disable the Tag• Protected by 32-bit kill password

• BUT…Security really depends on us– How much information do we want exposed?– Public policy will decide the limits

Study questions

1. How can one carry the item through the portal without being detected?

2. What is the blind spot? 3. Why don’t 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?

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