The main goal of this project is to realize seamless handover among cellular stations in a cellular system for emergency and disaster relief. Raspberry Pi with OpenWRT is chosen to become WiFi Access Point as the cellular station. Its limited weight, size and energy consumption enable it to be functional on a micro unmanned air vehicles (UAV). The overall design for WiFi seamless handover is the Wireless Distribution System (WDS) mode which is supported by several open source WiFi solutions including OpenWRT. The result is the switch over time within the same network is less than 0.3s. The phone call via Voice over IP (VoIP) software are not dropped during the handover.
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