The WiMedia UWB technology is a viable solution to provide high throughput for multimedia streams in future wireless multimedia home networks. The quality of experience for home users, however, could not be satisfactory due to the severe degradation of the TCP throughput caused by late TCP ACK-clocking. To solve the problem, we propose a cross-layer fast TCP ACK-clocking (FTAC) scheme, where a normal MAC ACK conveys a TCP ACK in both contention-based and reservation-based MAC protocols. With FTAC, it is shown by simulation that the utilization of UWB link by TCP is greatly enhanced and the TCP throughput approaches to that of UDP, which could be the upper bound of the utilization of UWB links by higher layers.