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Adaptive-modulation technique in wireless infrared indoor communications

: Grubor, J.; Jungnickel, V.; Langer, K.D.

Schäffer, C. ; Informationstechnische Gesellschaft -ITG-, Fachausschuß 5.3 Optische Nachrichtentechnik; Informationstechnische Gesellschaft -ITG-, Fachgruppe 5.3.3 Photonische Netze:
Photonische Netze : Vorträge der 7. ITG-Fachtagung vom 27. bis 28. April 2006 in Leipzig
Berlin: VDE Verlag, 2006 (ITG-Fachbericht 193)
ISBN: 3-8007-2959-8
Fachtagung Photonische Netze <7, 2006, Leipzig>
Conference Paper
Fraunhofer HHI ()
adaptives System; Infrarotübertragung; Kanalkapazität; Kurzstreckenfunktechnik; Letzte-Meile-Technik; Modellsimulation; Modulation von Licht; Strahlungsleistung; Systemoptimierung

The authors consider the idea of rate-adaptive transmission with multiple modulated sub-carriers in order to achieve broadband communication between fixed access point and mobile user terminal in an indoor non-directed infrared wireless system. This technique, known from DSL, and currently under discussion for RF wireless, seems also attractive for IR indoor systems, but needs to be examined under the specific conditions of the wireless optical channel. An ideal channel capacity analysis is performed to assess potential data rates in the multi-path IR channel typically present in rooms. Further on, by means of simulations, the authors investigate the throughput maximization for practical systems with the use of bit-loading. For capacity maximization, optimal allocation of the optical signal power over the sub-channels in the frequency domain is calculated, according to the channel state and optical power constraint (safety regulations for human eye and skin). Although still suboptimal, it could be considered as the most suitable bit and power allocation technique for the proposed adaptive system.