Fujitsu Corporation

Keiichi Otani

Takaya Yamamoto

Masaharu Matsumoto

Atsuo Serikawa

Koji Yano

A system for communication via cable-television communication lines includes a center device which generates a loop-detection packet for detecting a loop that is a defect of a network configuration, and a cable modem which is situated between said center device and a subscriber end, and detects the loop by regarding a receipt of the loop-detection packet from the subscriber end as a detection of the loop.

Cable modem and cable modem system

A method for switching a plurality of central devices including N working central devices and one protection central device of a N&plus;1 redundancy structure provided on a LAN center, to the CATV transmission path side of which terminal devices are connected each through a cable modem, having router functions forming segments respectively at the sides of the LAN center and the CATV transmission path, and a working central device transmitting routing information of the segment on the CATV transmission path side to inform the LAN center segment of an existence of the segment on the transmission path side, so that the terminal devices are connected to appropriate networks via the LAN center, the method comprising the steps of maintaining control information of the plurality of working central devices and the protection central device to be monitored, detecting failure of a working central device by regularly polling the N working central devices, switching the detected, failed working central device to the protection central device to connect the plurality of central devices to the CATV transmission path, transferring the maintained control information of the failed central device to the protection central device, and setting the protection central device to an active status according to the transferred control information.

Method for switching central device and a cable modem system using the same

A TDMA in a CATV center and a CAU in a subscriber home communicate a B-ch idle/busy map indicating the idle/busy state of a B channel in synchronization with each other, so that the allocation of the B channel dedicated to sound and the C channel dedicated to data in a transmission frame can be dynamically changed according to the contents of the B-ch idle/busy map. Consequently, it becomes possible to effectively use a transmission bandwidth up to its maximum.

Growing community of inventors

Kawasaki, Japan

Keiichi Otani