Low-SNR Capacity of Parallel IM-DD Optical Wireless Channels

Anas Chaaban, Zouheir Rezki, Mohamed-Slim Alouini

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


The capacity of parallel intensity-modulation and direct-detection (IM-DD) optical wireless channels with total average intensity and per-channel peak intensity constraints is studied. The optimal intensity allocation at low signal-to-noise ratio (SNR) is derived, leading to the capacity-achieving onoff keying (OOK) distribution. Interestingly, while activating the strongest channel is optimal if (i) the peak intensity is fixed, this is not the case if (ii) the peak intensity is proportional to the average intensity. The minimum average optical intensity per bit is also studied, and is characterized for case (i) where it is achievable at low SNR. However, in case (ii), the average optical intensity per bit grows indefinitely as SNR decreases, indicating that lower optical intensity per bit can be achieved at moderate SNR than at low SNR.
Original languageEnglish (US)
Pages (from-to)484-487
Number of pages4
JournalIEEE Communications Letters
Issue number3
StatePublished - Nov 29 2016

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: This work was supported in part by the Qatar National Research Fund (a
member of Qatar Foundation) under Grant NPRP 9-077-2-036. The statements
made herein are solely the responsibility of the authors


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