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ANALYSIS OF MULTIPLE OBJECT IDENTIFICATION WITH
PASSIVE RFID

K. Penttila, L. Sydanheimo, M. Kivikoski

Tampere University of Technology, Institute of Electronics, Rauma Research Unit, Kalliokatu 2, FI-
26100 Rauma, Finland.

ABSTARCT

Ability to identify multiple items simultaneously, without errors is one of the major advantages
achievable with RFID (Radio Frequency Identification) technology. Current specifications and
standards include a wide range of different protocols that enable above. This paper analyses the
identification performance of multiple objects with two commonly used algorithms. Theoretical
results are supported by practical measurements done in laboratory conditions. Results show how
identification speed and reliability depends on the size of the tag population, the range, and tags'
mutual alignment.

KEYWORDS
Automation, Aloha Protocols, EPC Tree Algorithm, Multiple Object Identification, Passive tags,
RFID

INTRODUCTION
Multiple object identification is a benefit in several automation and mechatronics application cases.
Accurate item identification, high operation efficiency, reliable control and real time monitoring or
tracking are achievable. Furthermore, passive RFID (Radio Frequency Identification) technology
enables applications far from those that are possible with currently used item identification systems.
Application examples include supply chain management, item control and management during
manufacturing, warehousing, transportation, etc.

Current RFID standards and specifications include wide variety of different protocols enabling
multiple object identification. However, their operational performance within commercial devices
varies a lot, and therefore it is important analyse the operation of pure algorithms. In order to verify
the value of the theoretical results, we measure simultaneous identification up to 64 passive tags with
commercially available reader and tags, using 915 MHz frequency band, 4WEIRP transmission
power, and EPC tree algorithm (Auto-ID Labs 2001). The bit rates and the time slot intervals defined
in this specification are used in theoretical analysis in order to maintain consistent examination.