An in-Depth Survey of Visible Light Communication Based Positioning Systems <s> Correlation <s> An indoor positioning system based on white LED communications is proposed and demonstrated. This positioning system shows that mean of distance errors is 0.651 cm in the space of 30 cm × 30 cm × 50 cm. <s> BIB001 </s> An in-Depth Survey of Visible Light Communication Based Positioning Systems <s> Correlation <s> We proposed an optical wireless position sensing system using light emitting diodes (LEDs), demonstrating it via experiment.During experiment, we used four LED lamps composed of 16 LED chips with a view angle of 65° at half power. Further, we assigned a unique address for each LED lamp, being transmitted using LED properties such as lighting and switching. Afterward, we used correlation to locate the target. The proposed positioning system displayed 4.38 cm of mean distance error among 36 points with dimensions of 1 × 1 × 1.2 m3. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1622–1626, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26880 <s> BIB002
Correlation is a new technique for fingerprinting matching. This technique is based on the idea that the correlation of the mixed received signal from all base stations and the transmitted signal of a specific base station is higher when the mobile device is closer to that base station. The performance of this technique depends on choosing the pattern of the signal transmitted from the base stations so as to yield high correlation with the received signal. A VLC based positioning system using fingerprinting correlation to determine the location was proposed in BIB001 BIB002 Assuming that all base stations are synchronized to transmit at the same time, the received signal R will be: R = [P rB + P rD , P rA + P rC , P rC + P rD , P rA + P rB ] where P rA , P rB , P rC , and P rC are received power from the base stations A, B, C, and D. The correlations between the received data and each pattern are: The correlation sum ratios for x (CSR X ) and the correlation sum ratios for y (CSR Y ) are calculated as: For any values (x, y) of the receiver coordinate, the value of CSR X is related only to x, independent of y, and vice versa for CSR Y . During the offline phase, the values of CSR X and CSR Y are collected from all over the environment to create the reference CSR X corresponding to x and the reference CSR Y corresponding to y as shown in Figure 4 . On the online phase, the value of CSR X and CSR Y are calculated and compared to the reference CSR X and CSR Y to find the coordinate (x, y). The experimental was conducted in a space measuring 1 × 1 × 1.2 m 3 and the result showed that the maximum and mean distance errors were 12.46 and 4.38 cm, respectively. 