29 January 2018 Indoor communications networks realized through hybrid free-space optical and Wi-Fi links
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Abstract
Recently, free-space optical (FSO) networks have been investigated as a potential replacement for traditional WiFi networks due to their large bandwidth potentials. However, FSO networks often suffer from a lack of mobility. We present a hybrid free-space optical and radio frequency (RF) system that we have named WiFO, which seamlessly integrates free-space optical links with pre-existing WiFi networks. The free-space optical link in this system utilizes infrared LEDs operating at a wavelength of 850nm and is capable of transmitting 50Mbps over a three-meter distance. In this hybrid system, optical transmitters are embedded periodically throughout the ceiling of a workspace. Each transmitter directs an optical signal downward in a diffuse light cone, establishing a line of sight optical link. Line of sight communications links have an intrinsic physical layer of security due to the fact that a user must be directly in the path of transmission to access the link; however, this feature also poses a challenge for mobility. In our system, if the free-space optical link is interrupted, a control algorithm redirects traffic over a pre-existing WiFi link ensuring uninterrupted transmissions. After data packets are received, acknowledgments are sent back to a central access point via a WiFi link. As the demand for wireless bandwidth continues to increase exponentially, utilizing the unregulated bandwidth contained within optical spectrum will become necessary. Our fully functional hybrid free-space optical and WiFi prototype system takes full advantage of the untapped bandwidth potential in the optical spectrum, while also maintaining the mobility inherent in WiFi networks.
Conference Presentation
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Spencer Liverman, Qiwei Wang, Yu-Chung Chu, Anindita Borah, Songtao Wang, Arun Natarajan, Thinh Nguyen, Alan X. Wang, "Indoor communications networks realized through hybrid free-space optical and Wi-Fi links", Proc. SPIE 10559, Broadband Access Communication Technologies XII, 105590H (29 January 2018); doi: 10.1117/12.2292292; https://doi.org/10.1117/12.2292292
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