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INTERSECTOR CORRELATIONS FOR SWITCHED BEAMS DIVERSITY PERFORMANCE EVALUATION

INTERSECTOR CORRELATIONS FOR SWITCHED BEAMS DIVERSITY PERFORMANCE EVALUATION. Alain SIBILLE ( sibille@ensta.fr ), Stéphane FASSETTA* Laboratoire Electronique-Informatique ENSTA, 32 Bd Victor, 75739 Paris cedex 15, France * Now at THALES Communications , Colombes, France. Outline.

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INTERSECTOR CORRELATIONS FOR SWITCHED BEAMS DIVERSITY PERFORMANCE EVALUATION

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  1. INTERSECTOR CORRELATIONS FOR SWITCHED BEAMS DIVERSITY PERFORMANCE EVALUATION Alain SIBILLE (sibille@ensta.fr), Stéphane FASSETTA* Laboratoire Electronique-Informatique ENSTA, 32 Bd Victor, 75739 Paris cedex 15, France * Now at THALES Communications, Colombes, France

  2. Outline • context and motivation • antennas • intersector correlations: theory • computations assuming a model scenario • comparison with experimental results • angular vs. spatial diversity • conclusion

  3. Context and motivation • GENERAL CONTEXT: low-complexity beam-switched smart antennas for terminals, HIPERLAN 2 access points etc … • MOTIVATION: an attempt to quantify the potential benefit brought by beam-switched antennas prior to any experiment, intended for optimal antenna design. • PARTICULAR CONTEXT: experimental channel measurement campaigns and antenna design carried out within the European ADAMO project (1998-2000).

  4. Antennas 6 monopoles circular array 4 patches planar array

  5. Antennas 6 BSSA circular array 13 monopoles array

  6. Hi Hj Intersector correlations : theory i j Wideband intersector correlation: with rij is a measure of the diversity performance of a switched beams antenna for wideband radio link (single or multiple carriers)

  7. Intersector correlations : theory Discrete multipath channel model: f(t): receiver filter CIR Ail:path transmittance (Di: receiver antenna radiation pattern) tl: path delay gl: CIR of environment+ emitter : Fourier transform of

  8. Intersector correlations : theory Assuming perfect averaging of small-scale fading: Continuous approximation of the discrete sum (scenario averaging): Intersector correlation: Di,j: radiation patterns P(j,q): angular power spectrum for omni receiver antenna

  9. Intersector correlations : theory Extension to polarisation-dependent propagation The channel correlation contains the term: Continuous approximation: generalize is somewhat related to

  10. q / s q / s c c 4 patches array 6 BSSA array Dj Dj Computations assuming a V-V model scenario

  11. 13 monopoles array Dj Computations assuming a V-V model scenario Complex vs. Amplitude-only correlations (Phase behavior)

  12. Comparison with experimental results (ADAMO campaign 1, IMST indoor measurements) • 3 rooms: small , library, hall • 6 beams antenna at ceiling level • omnidirectional radiator at desk level • 5.2 GHz, 120° MHz BW • 31 locations, small-scale fading averaging every l/10 • 6 monopoles array and 4 patches array small office library

  13. c (°)  (°) =60° =120° =180° 0 5 0.46 0.13 0.15 0 10 0.46 0.12 0.16 0 20 0.48 0.10 0.16 model: 0 40 0.50 0.07 0.15 20 10 0.56 0.03 0.07 20 20 0.56 0.03 0.07 20 40 0.55 0.02 0.08 30 20 0.60 0.09 0.01 30 40 0.58 0.06 0.04 CAMPAIGN 1 (6 monopoles array) 0.23 0.009 0.05 small office 0.31 0.07 0.07 library 0.25 0.11 0.04 hall 0.46 0.07 0.09 Comparison with experimental results (ADAMO campaign 1, IMST measurements)

  14. 6 monopoles array d / l Dj Computations assuming a V-V model scenario ADDITIONAL SPATIAL DIVERSITY

  15. 60° 120° 180°  d/l 6Monop exp 0.290 0.069 0.030 6Monop model 0.292 0.071 0.030 40 40 0.18 4Patches exp 0.144 0.037 0.019 4Patches model 0.140 0.027 0.024 35 15 0.38 Comparison with experimental results INTERSECTOR CORRELATION: model vs. Experiment (ADAMO campaign 1) expected on account of the Tx-Rx LOS tilt in elevation

  16. Angular vs. spatial diversity • spatial diversity= spatial filtering of faded signals • angular diversity= angular filtering of incoming waves • IS THERE A FUNDAMENTAL DIFFERENCE BETWEEN BOTH ?IS THE DISTINCTION BETWEEN ANGULAR AND SPATIAL DIVERSITY SO CLEAR IN PRACTICAL ARRAYS ?

  17. Angular vs. spatial diversity ROLE OF THE PHASE CENTER 6 points in angular space, used to locally equate to zero the phase differential « local » phase center for a given (j,q) direction

  18. Angular vs. spatial diversity ROLE OF THE PHASE CENTER A SIMPLE INTERPRETATION: sectored arrays also exhibit spatial diversity due to sector dependent position of the phase center 6 MONOPOLES ARRAY

  19. Angular vs. spatial diversity ROLE OF THE PHASE CENTER 13 MONOPOLES ARRAY

  20. Conclusion • A simple tool has been proposed to evaluate the diversity performance of beam-switched antennas: intersector correlations assuming a model scenario • Comparison with indoor propagation channel measurements is favorable, on condition of the presence of extra spatial diversity • Evidence of hybrid spatial angular diversity in beam-switched circular arrays due to non central position of the phase center. • Perspective: evaluation of correlations for MIMO antennas

  21. Acknowledgements The authors are grateful to J. Kunisch, M. Schneider, J. Pamp, E. Zollinger, A. Winkelman and M. Gehrt of IMST for supplying CIR measurements

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