A Space-frequency Power Allocation Algorithm for MIMO OWC Systems over Low-Pass Channels

Thiago Elias Bitencourt Cunha, W. X. Fan, X. Deng, J. M. G. Linnartz Eindhoven University of Technology, South China Normal University, Signify (Philips Lighting) Research

Abstract
Due its advantages, LEDs are commonly used for illumination and are strong candidates to drive data transmission in optical wireless communication (OWC) systems. However, the modulation bandwidth of this source is limited. An alternative is to deploy multiple LEDs in a Multiple Input Multiple Output (MIMO) scheme. In further boosting the bit rate, the low-pass frequency response of the LEDs poses further limitations. The impact of the low-pass effect on the performance of LED-based MIMO OWC systems has not yet been fully addressed. To compensate this behaviour, Orthogonal Frequency Division Multiplexing (OFDM) is often used. By using OFDM, power loading strategies can be used to appropriately distribute power over the subcarriers. Different power loading schemes are proposed, mainly the uniform loading and the optimized waterfilling loading . In this paper, we present an analytical model for the channel and we derive expressions for the achievable rate considering common low-pass frequency responses. Based on an indoor LED-based MIMO OWC setup, we investigate system performance for different power loading strategies. We point out that the resource allocation optimization only in the frequency domain may not be satisfactory and we propose a new algorithm considering the spatial and frequency domains to load power over the MIMO channels and OFDM subcarriers.

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The conference focuses on leading edge research on Optical Wireless Communication in its different forms and gathers experts from academia and industry to show their latest technical results and showcase their products and services. The application scope is broad and it ranges from Ultra-short range to Ultra-long range.

Conference topics cover visible light communication, infrared optical and ultraviolet communication. These different forms of OWC can potentially be employed in a diverse range of communication applications ranging from optical interconnects within integrated circuits through outdoor inter-building links to free-space satellite communications.

The following topics are being covered during the conference:

  • Ultra-short range: for instance chip-to-chip communications in stacked and closely packed multi-chip packages
  • Short range: For instance wireless personal area network (WPAN) applications under standard IEEE 802.15.7 and underwater communications.
  • Medium range: indoor IR and visible light communications (VLC) for wireless local area networks (WLANs) and inter-vehicular and vehicle-to-infrastructure communications.
  • Long range: inter-building connections, also called free-space optical communications (FSO).
  • Ultra-long range: Laser communication in space especially for inter-satellite links and establishment of satellite constellations

This paper was presented during the conference which took place during the Photonics Applications Week.

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