Herarchical Cellular Multihop Networks分层多跳蜂窝网络

1、localization by rfidpercom032021/11/7by hlwu, hscc2rfid background the current (2003) rfid system does not provide the transmission strength of tags to readers. readers only report the power level of the tag being detected.2021/11/7by hlwu, hscc3goal landmarc: location identification based on dynami

2、c active rfid calibration a location sensing prototype system that uses rfid technology for in-building use. improves localization accuracy by utilizing the concept of reference tags.2021/11/7by hlwu, hscc42021/11/7by hlwu, hscc5landmarc approach (i) in the sensing field: n readers m fixed tags (i.e

3、., reference tags) u tracking tags (i.e., moving objects) readers are all configured with continuous mode and a detection-range of 1-8 level. signal strength vector of a tracking tag: signal strength vector of a fixed tag:12(,.,)nss ss 12(,.,)n 2021/11/7by hlwu, hscc6landmarc approach (ii) definitio

4、n: euclidian distance between a tracking tag and a reference tag j : definition: the location relationship vector between the m reference tags and the tracking tag:21()njiiies12(,.,)mee ee2021/11/7by hlwu, hscc7landmarc approach (iii) the placement of the unknown tag is surrounded by k most likely r

5、eference tags. weighted location (x, y) of the unknown tag: where weights are defined as1( , )(,)kiiiix yyw x22111kiiiiewe2021/11/7by hlwu, hscc8experimental environment spider system: reader: 308mhz, has an 802.11b interface to communicate, detection range of 150 feet, detect up to 500 tags in 7.5

6、seconds, 8 different power levels active tag: read range of 150 feet and can be increased to 1000 feet with the addition of a special antenna, send signal in random with an average of 7.5 seconds performance metric: location estimation error2021/11/7by hlwu, hscc9experiment environment2021/11/7by hl

7、wu, hscc10effect of k (number of nearest neighbors)1( , )(,)kiiiix yyw x2021/11/7by hlwu, hscc11environmental factors: daytime vs. night2021/11/7by hlwu, hscc12effect of n (number of readers)2021/11/7by hlwu, hscc13effect of placement of reference tags2021/11/7by hlwu, hscc14the accuracy is improved with a higher reference tag density. however, it is not as great as expected.15conclusions a new rfid-based location system. major advantages: no need for a large number of expensive rfid readers the environmental dynamics can easily be accommodated. the accuracy can be greatly imp