12 Yafeng Yin et al. use the optimal powers instead of the maximum one (30.7dBm).PID and PIA mainly focus on the target tags,while avoiding identifying the interference tags. When we change the value of a,our solutions can also work well.For example, when d 1m,I 1m,s =80,u=70,we set a 80%.The coverage ratio of MaxPw.PID.PIA is respectively equal to 89%.82.5%.86%.which satisfy the constraint of p.The execution time of MaxPw,PID,PIA is respectively equal to 2.2s,1.45s,2.0s.Our solutions outperform the baseline solutions. 8 Conclusion In this paper,we investigate the problem of identifying the tags in the specified area.We conduct extensive experiments on the commodity RFID system in the realistic environments and present two efficient solutions.PID and PIA.Both PID and PIA work in a similar way of picture-taking in a camera,they first focus on the specified area and then identify the target tags efficiently.The realistic experiments show that our solutions outperform the baseline solutions Acknowledgement This work is partially supported by the National Natural Science Foundation of China under Grant No.61100196.61073028,61021062:the JiangSu Natural Sci- ence Foundation under Grant No.BK2011559;and NSF grants ECCS 1231461 ECCS1128209.CNS1138963.CNS1065444.and CCF1028167 References 1.Vogt,H.:Efficient object identification with passive RFID tags.In:Proc.of Per- vasive,pp.98-113.Springer(2002) 2.Maguire,Y.,Pappu,R.:An optimal q-algorithm for the iso 18000-6c rfid protocol. IEEE Transactions on Automation Science and Engineering.6,1,16-24 (2009) 3.Zhen,B.,Kobayashi,M.,Shimuzu,M.:Framed aloha for multiple rfid objects identification.IEICE Transactions on Communications.E80-B,3,991-999 (2005) 4.Lee.S.,Joo,S..Lee.C.:An enhanced dynamic framed slotted ALOHA algorithm for RFID tag identification.In:Proc.of MobiQuitous,pp.166-172.IEEE (2005) 5.Tan,C.C.,Sheng,B.,Li,Q.:How to Monitor for Missing RFID Tags.In:IEEE 、ICDCS,pp.295-302.IEEE(2008) 6.Li.T..Chen,S.,Ling,Y.:Identifying the Missing Tags in a Large RFID System. In:ACM MobiHoc,pp.1-10.ACM(2010) 7.Zheng.Y..Li.M.:Fast Tag Searching Protocol for Large-Scale RFID Systems.In: IEEE ICNP,pp.363-372.IEEE (2011) 8.Kodialam,M.,Nandagopal,T.:Fast and reliable estimation schemes in RFID systems.In:ACM MobiCom,pp.322-333.ACM(2006) 9.Qian.C.,Ngan,H.,Liu,Y.,Ni,L.M.:Cardinality Estimation for Large-scale RFID Systems.IEEE Transactions on Parallel and Distributed Systems.22.9.1441-1454 (2011) 10.Zheng,Y.,Li,M.,Qian,C.:PET:Probabilistic Estimating Tree for Large-Scale RFID Estimation.In:IEEE ICDCS,pp.37-46.IEEE (2011) 11.Buettner,M.,Wetherall,D.:An emprical study of uhf rfid performance.In:Proc. of MobiCom,pp.223-234.ACM(2008) 12.Arror,S.R.,Deavours,D.D.:Evaluation of the state of passive uhf rfd:An exper- imental approach.IEEE Systems Journal.1,2,168-176 (2007) 13.Jeffery,S.R.,Garofalakis,M.,Franklin,M.J.:Adaptive cleaning for rfid data streams.In:Proc.of VLDB,pp.163-174.ACM(2006) 14.Xu,X.,Gu,L.,Wang,J.,Xing,G.:Negotiate Power and Performance in the Reality of RFID Systems.In:IEEE PerCom,pp.88-97.IEEE (2010)12 Yafeng Yin et al. use the optimal powers instead of the maximum one (30.7dBm). PID and PIA mainly focus on the target tags, while avoiding identifying the interference tags. When we change the value of α, our solutions can also work well. For example, when d = 1m, l = 1m, s = 80, u = 70, we set α = 80%. The coverage ratio of MaxPw, PID, PIA is respectively equal to 89%, 82.5%, 86%, which satisfy the constraint of ρ. The execution time of MaxPw, PID, PIA is respectively equal to 2.2s, 1.45s, 2.0s. Our solutions outperform the baseline solutions. 8 Conclusion In this paper, we investigate the problem of identifying the tags in the specified area. We conduct extensive experiments on the commodity RFID system in the realistic environments and present two efficient solutions, PID and PIA. Both PID and PIA work in a similar way of picture-taking in a camera, they first focus on the specified area and then identify the target tags efficiently. The realistic experiments show that our solutions outperform the baseline solutions. Acknowledgement This work is partially supported by the National Natural Science Foundation of China under Grant No. 61100196, 61073028, 61021062; the JiangSu Natural Sci￾ence Foundation under Grant No. BK2011559; and NSF grants ECCS 1231461, ECCS 1128209, CNS 1138963, CNS 1065444, and CCF 1028167. References 1. Vogt, H.: Efficient object identification with passive RFID tags. In: Proc. of Per￾vasive, pp. 98-113. Springer (2002) 2. Maguire, Y., Pappu, R.: An optimal q-algorithm for the iso 18000-6c rfid protocol. IEEE Transactions on Automation Science and Engineering. 6, 1, 16-24 (2009) 3. Zhen, B., Kobayashi, M., Shimuzu, M.: Framed aloha for multiple rfid objects identification. IEICE Transactions on Communications. E80-B, 3, 991-999 (2005) 4. Lee, S., Joo, S., Lee, C.: An enhanced dynamic framed slotted ALOHA algorithm for RFID tag identification. In: Proc. of MobiQuitous, pp. 166-172. IEEE (2005) 5. Tan, C.C., Sheng, B., Li, Q.: How to Monitor for Missing RFID Tags. In: IEEE ICDCS, pp. 295-302. IEEE (2008) 6. Li, T., Chen, S., Ling, Y.: Identifying the Missing Tags in a Large RFID System. In: ACM MobiHoc, pp. 1-10. ACM (2010) 7. Zheng, Y., Li, M.: Fast Tag Searching Protocol for Large-Scale RFID Systems. In: IEEE ICNP, pp. 363-372. IEEE (2011) 8. Kodialam, M., Nandagopal, T.: Fast and reliable estimation schemes in RFID systems. In: ACM MobiCom, pp. 322-333. ACM (2006) 9. Qian, C., Ngan, H., Liu, Y., Ni, L.M.: Cardinality Estimation for Large-scale RFID Systems. IEEE Transactions on Parallel and Distributed Systems. 22, 9, 1441-1454 (2011) 10. Zheng, Y., Li, M., Qian, C.: PET: Probabilistic Estimating Tree for Large-Scale RFID Estimation. In: IEEE ICDCS, pp. 37-46. IEEE (2011) 11. Buettner, M., Wetherall, D.: An emprical study of uhf rfid performance. In: Proc. of MobiCom, pp. 223-234. ACM (2008) 12. Arror, S.R., Deavours, D.D.: Evaluation of the state of passive uhf rfd: An exper￾imental approach. IEEE Systems Journal. 1, 2, 168-176 (2007) 13. Jeffery, S.R., Garofalakis, M., Franklin, M.J.: Adaptive cleaning for rfid data streams. In: Proc. of VLDB, pp. 163-174. ACM (2006) 14. Xu, X., Gu, L., Wang, J., Xing, G.: Negotiate Power and Performance in the Reality of RFID Systems. In: IEEE PerCom, pp. 88-97. IEEE (2010)