1. a Symbol Technologies , 401 Hackensack Avenue, Hackensack, NJ, 07601, USA E-mail:
2. b Department of Industrial and Manufacturing Engineering , Oregon State University , 118 Covell Hall, Corvaliis, OR, 97331, USA E-mail:
3. c Department of Industrial Engineering , University of Pittsburgh , 1048 Benedum Hall, Pittsburgh, PA, 15261, USA E-mail:
4. d Department of Information Sciences and Telecommunications , and Hewlett-Packard Laboratories, HP Laboratories , 1501 Page Mill Road, Palo Alto, CA MS 1U-17, 94304, USA E-mail: