EURASIP Journal on Wireless Communications and Networking
Volume 2007 (2007), Article ID 18730, 13 pages
doi:10.1155/2007/18730
Research Article

ASAP: A MAC Protocol for Dense and Time-Constrained RFID Systems

Girish Khandelwal,1 Kyounghwan Lee,2 Aylin Yener,2 and Semih Serbetli3

1Qualcomm, San Diego 92121, CA, USA
2Wireless Communications and Networking Laboratory, Department of Electrical Engineering, Pennsylvania State University, University Park 16802, PA, USA
3Philips Research, Eindhoven 5621, The Netherlands

Received 16 October 2006; Revised 10 March 2007; Accepted 21 June 2007

Academic Editor: Alagan Anpalagan

Copyright © 2007 Girish Khandelwal et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

We introduce a novel medium access control (MAC) protocol for radio frequency identification (RFID) systems which exploits the statistical information collected at the reader. The protocol, termed adaptive slotted ALOHA protocol (ASAP), is motivated by the need to significantly improve the total read time performance of the currently suggested MAC protocols for RFID systems. In order to accomplish this task, ASAP estimates the dynamic tag population and adapts the frame size in the subsequent round via a simple policy that maximizes an appropriately defined efficiency function. We demonstrate that ASAP provides significant improvement in total read time performance over the current RFID MAC protocols. We next extend the design to accomplish reliable performance of ASAP in realistic scenarios such as the existence of constraints on frame size, and mobile RFID systems where tags move at constant velocity in the reader's field. We also consider the case where tags may fail to respond because of a physical breakdown or a temporary malfunction, and show the robustness in those scenarios as well.