A novel hierarchical architecture for hybrid wireless sensor and access networks has been proposed based on cost-effective radio-over-fiber (ROF) links with the coarse wavelength-division-multiplexing (CWDM) technique. Wireless fidelity (WiFi) signals are distributed to the remote radio units transparently over optical fibers in a star-shaped network topology. The wireless access traffic together with the perceiving usage scenarios including video monitoring and temperature sensing has been successfully demonstrated in the hybrid IEEE 802.11 and 802.15.4 networks. The transmission performance of the CWDM-ROF links is evaluated in terms of the error-vector magnitude (EVM) and data throughput for both uplinks and downlinks. The results show that the WiFi signals are successfully delivered through the CWDM-ROF links including a 4.5 km fiber and a 7 m wireless channel with a 3% EVM penalty. This CWDM-ROF technology can expand the application range of wireless sensor networks with the advantages of better capacity, larger coverage area, and lower investment on wired infrastructure.
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