Collaborative multibeam transmitter and imaging receiver in realistic environment

Abstract

In this paper, we propose a collaborative mobile optical wireless (OW) system that employs a collaborative adaptive beam clustering method (CABCM) in conjunction with an imaging receiver. Collaborative maximum ratio combining ( ) scheme is used to collaboratively distribute the transmit power among diffusing spots. The main goal is to increase the received optical power and improve the signal-to-noise ratio (SNR) at each coexisting receiver when the system operates in a multiuser scenario under the constraints of background noise, multipath dispersion and mobility. Our proposed system (collaborative adaptive beam clustering method) is evaluated at 30 Mbit/s to enable comparison with previous work, and is also assessed at higher bit rates: 2.5 Gbit/s and 5 Gbit/s. Simulation results show that at a bit rate of 30 Mbit/s, a significant SNR improvement of 39 dB is achieved when a CABCM system replaces a multiuser line strip multibeam system (LSMS) at a 6 m transmitter-receiver horizontal separation. The results also show that the proposed system can achieve a 22 dB SNR when the system operates at 2.5 Gbit/s in a two-user scenario. Keywords: Optical wireless, collaborative multibeam transmitter, beam clustering, beam power adaptation. INTRODUCTIONThe optical spectrum has the potential to provide a high-speed transmission medium for short-range indoor wireless communication systems. The OW link provides a secure and a promising complement to radio frequency (RF) links as well as an abundant unregulated bandwidth that enables rapid deployment at low cost [1]. However, the design challenges of OW systems lie in two major impairments when employing intensity modulation with direct detection (IM/DD). These impairments include multipath dispersion and additive noise due to sunlight and artificial background light. The former degrades the signal-to-noise ratio (SNR) while the latter limits the link capacity. In addition, OW links are subjected to eye and skin safety regulations which restrict the maximum allowed optical power transmitted [2], [3]. OW links are often categorized into two basic classification schemes: direct LOS and diffuse systems. Direct LOS links improve power efficiency and minimize multipath dispersion, but inherently require transmitterreceiver alignment and can suffer from shadowing due to moving objects. Diffuse systems offer links that are robust in the presence of shadowing, but severely suffer from multipath dispersion in addition to higher path losses compared to direct LOS links. A possible efficient technique that can exploit the advantaged of direct LOS systems and overcome the drawbacks of diffuse links is a multibeam transmitter [4] - [9]. The multibeam transmitter was proposed to tackle the impact of multipath dispersion, mitigate the shadowing effects and improve SNR performance. The multibeam transmitter is used to generate multiple diffusing spots pointed in different directions in a room, which act as secondary transmitters [5], [9]. Another efficient and simple technique that ca...

Collaborative adaptive optical wireless system in realistic indoor environment

“…The proposed transmitter and receiver configuration helps mitigate the shadowing effect, reduces multipath dispersion, and improves the system performance under transmitter-receiver mobility at high data rates. In [23], we introduced a collaborative multibeam transmitter to the design of OW systems where high data rates were shown to be feasible. In this paper, we model our collaborative adaptive beam clustering method (CABCM) in conjunction with an imaging receiver considering two room scenarios: an empty room, and a real office environment.…”