The Hi-SD CBS includes a termination unit and pluralities of distributed customer premise units connected through the cable TV (CATV) network. The radio signals in Hi-SD CBS are propagating inside the co-axial cable. To insure the linking quality between the termination unit and customer premise devices, preamble procedures are required to adjust the transmitting radio power, the receiver sensitivity, the channel equalization, and to synchronize the transceivers for data transmission between the termination unit and the customer premise devices. To guarantee a secure link between the termination unit and an individual customer premise device or a group of premise devices, the termination unit provides different encryption keys to different customer premise device groups.