Hemispherical Lens Based Imaging Receiver for MIMO Optical Wireless Communications

Transcription

1 Hemisperical Lens Based Imaging Receiver for MIMO Optical Wireless Communications Dr. Tomas. Q. Wang, Dr. Y. Amet Sekercioglu and Prof. Jean Armstrong Department of Electrical and Computer Systems Engineering Monas University, Melbourne, Australia {Tom.Wang, Amet.Sekercioglu, Tis work was supported under an Australian Researc Council s (ARC) Discovery funding sceme (DP 0948).

2 Outline Introduction System description and analysis Simulation results Summary

3 Introduction MIMO Optical Wireless System wit Imaging Receiver MIMO as potential to increase te data rate and te robustness of optical wireless systems Non imaging receiver -- evenly distributed power --very little diversity Imaging receiver using conventional lens -- significant spatial diversity -- small field of view (FoV) Can we increase te FoV wit a different lens? Given a different lens, can we still ave spatial diversity?

4 Imaging Receiver Using Hemisperical Lens Introduction Hemisperical lens -- gives wide field of view, used for cloud recording as early as 90s -- forms distorted images -- not a problem for IM/DD Contribution of tis work -- Study te MIMO cannel gain wit emisperical lens based receiver -- Calculate total received power as a function of angle of incidence and sow te wide FoV of te receiver -- Demonstrate spatial diversity by observing te images of te LEDs and calculating te cannel matrix.

5 System Description System Description and Analysis Nt Generalized Lambertian LEDs installed on te celling, pointing down -- LED is placed at Terefore is te angle of incidence -- emitting un-polarized ligt -- Radiation pattern: R were m ln lncos S : lsin cos, lsin sin, lcos o m cos Te receiver put on te floor, pointing up -- Lens is of radius R and refraction index n -- Nr potodetectors m l -- A Nr X Nt Cannel Matrix

6 Analysis System Description and Analysis Ray tracing -- reflection and refraction on te surface of te lens -- two refractions: cange te direction te ray travels and are governed by Snell s Law n sin n sin n n : refractve index of media and media, respectively. : angle of incidence : angle of refraction -- two reflections: results in te loss of optical power governed by Fresnel equations R, p n cos n cos n cos n cos R, s n cos n cos n cos n cos --For un-polarized ligt, te power transmission coefficient is Cannel gain P m mcos cost o air-lens Pt l arcsin n n 3 T, lens-air 3 4 rdrd receiver T R R s p

7 Cannel gain Simulation Results Calculated total received power as a function of angle of incidence Settings -- 5 m X 5 m X.5 m room -- One LED on te ceiling pointing down 0-5 wit semi-angle -- Receiver put on te floor pointing up wit 5 mm lens and a potodetector. -- Terefore te maximum angle of incidence available is 70.5 degrees.5 m 5 m 5 m / =5 o / =30 o / =45 o / =60 o Angle of incidence (degree) Cannel gains versus te angle of incidence for Lambertian emitters wit varying alf power semi-angles Cannel gain drops at different rates Adequate gain provided by some of LEDs at large angel of incidence Field of view depends on alf power semi angles of transmitters: -- Large alf power semi-angle = Greater field of view Large alf power semi-angle -- Adequate gain out to 70 degrees angle of incidence

8 y (mm) Power Density on Imaging Plane Simulation Results Settings -- 5 m X 5 m X.5 m room -- four Lambertian LEDs, wit semi-angles 60 degrees, on te ceiling making 30 degrees of angle wit te receiver -- Receiver put at te center of te floor pointing up wit 5 mm lens and four potodetectors. Eac covers one quadrant x (mm) Four LEDs wit 30 degrees of angle of incidence m 3 5 m 5 m Images of four LEDs are clearly separated -- System wit four potodiode receivers would ave significant diversity H Little correlation between rows or columns -- Good diversity 4 6

9 y (mm) Effect of more widely spaced transmitters Simulation Results x x (mm) 0 Four LEDs wit 45 degrees of angle of incidence H Wit more widely spaced transmitters Angle of incidence increases Overall received power decreases -- Completely separated images No correlation between rows and columns -- Full diversity

10 Simulation Results Imaging wit Hemisperical lens vs Non Imaging Imaging Non-imaging Optical power distributes unevenly in eac image Various LEDs form separated images H,,, N,,, N N, N, N, N r r r t Te cannel matrix is of full rank Terefore provides full diversity order t t Te optical power distributes evenly among te potodetectors H Unitranked Terefore no diversity provided N N N t t t

11 Summary In tis work, we ave answered te following questions: Can we increase te FoV wit a different lens? Te imaging receiver as large field of view wit a emisperical lens as large as 70 degrees for a Lambertian LED Given a different lens, can we still ave spatial diversity? Spatial diversity is also provided by te lens full ranked cannel matrix

12 Reference [] J. R. Barry, J. M. Kan, E. A. Lee and D. G. Messerscmitt, Hig-speed nondirective optical communication for wireless networks, IEEE Network Magazine, vol. 5, no. 6, pp , Nov. 99. [] M. Kaverad and S. Jivkova, Indoor broadband optical wireless communications: optical subsystems designs and teir impact on cannel caracteristics, IEEE Wireless Communications, vol.0, no., pp , Apr [3] L. Zeng, D. C. O Brien, H. L. Min, G. E. Faulkner, K. Lee, D. Jung, Y. O and E. T. Won, Hig data rate multiple input multiple output (MIMO) optical wireless communications using wite led ligting, IEEE Journal on Selected Areas in Communications, vol. 7, no. 9, pp , Dec [4] K. D. Dambul, D.C. O'Brien and G.. Faulkner, Indoor Optical Wireless MIMO System Wit an Imaging Receiver, IEEE Potonics Tecnology Letters, vol. 3, no., pp , Jan. 0. [5] S. Hranilovic and F.R. Ksciscang, A pixelated MIMO wireless optical communication system, IEEE Journal of Selected Topics Reference in Quantum Electronics, vol., no. 4, pp , July/Aug [6] J. M. Kan and J. R. Barry, Wireless Infrared Communications, Proceedings of te IEEE, vol. 85, no., pp , Feb, 997. [7] J.M. Kan, R. You, P. Djaani, A. G. Weisbin, B. K. Teik and A. Tang, Imaging diversity receivers for ig-speed infrared wireless communication, IEEE Communications Magazine, vol. 36, no., pp , Dec [8] D. C. O Brien, Multi-Input Multi-Output (MIMO) indoor optical wireless communications, Signals, Systems and Computers, 009 Conference Record of te Forty-Tird Asilomar Conference on, pp , Nov [9] S. D. Perli, N. Amed, and D. Katabi, PixNet: Interference-Free Wireless Links Using LCD- Camera pairs, In Proceedings of MOBICOM'00, Cicago, pp.37-48, 00.

13 Reference [0] W. Yuan, K. Dana, M. Varga, A. Asok, M. Gruteser and N. Mandayam, Computer vision metods for visual MIMO optical system, in Computer Vision and Pattern Recognition Worksops (CVPRW), 0 IEEE Computer Society Conference on, pp , 0. [] M. J. Langford, A. Fox, and R.S. Smit, Langford's basic potograpy te guide for serious potograpers 9t Edition, Focal Press. [] L. Zeng, D. C. O Brien, H. Le-Min, L. Kyungwoo, J. Daekwang, and O. Yunje, Improvement of Date Rate by using Equalization in an Indoor Visible Ligt Communication System, in Proc. IEEE ICCSC, pp , 008. [3] F. R. Gfeller and U. H. Bapst, Wireless in-ouse data communication via diffuse infrared radiation, Proc. IEEE, vol. 67, pp , Nov [4] K. D. Möller, Optics, University Science Books, Mill Valley, California. [5] J. R. Barry, J. M. Kan, W. J. Krause, E. A. Lee, and D. G. Messerscmitt, Simulation of multipat impulse response for wireless optical cannels, IEEE J. Select. Areas in Commun., vol., no. 3, pp , Apr. 993.

14 Tank you!

15 Cannel Gain Cannel Gain Additional Graps degrees 30 degrees 60 degrees 80 degrees Total cannel gain versus distance Total received power on potodetector/power transmitted by LED LED semi-angle 5 degrees LED pointing directly at receiver Distance from LED to te lens (m) metre metres 3 metres 4 metres Angle of incidence Total cannel gain versus angle of incidence Total received power on potodetector/power transmitted by LED LED semi-angle 5 degrees LED pointing directly at receiver