A voice communication system over WiFi 802.11 network includes: WiFi phone devices, subscription servers and wireless access points. Through voice and data gateways the system can transfer both voice and data streams through WiFi; Phone devices with both wired and WiFi wireless interfaces can automatically switches between wired network and wireless network through WiFi access points. Subscription server maintains the current status of each device every time it changes location. Voice packets are prioritized over regular data packets and dispatched to different network interface by smart packet dispatcher. Quality of service for voice conversation over WiFi is achieved by various methods: piggy-tail method and ACK enhancements and other improvements to reduce delay and latency of real time voice packets.