摘要:
A communication system includes a hybrid fibre/coax distribution network. A head end generates a master clock signal and derives a head end RF clock signal locked in frequency to the master clock signal. A head end symbol clock signal is derived, locked in frequency to the master clock signal, and multiple strings of downstream digital data are converted to sequences of symbols at times determined by the symbol clock signal. The symbols are modulated onto multiple orthogonal carriers having frequencies determined by the RF clock signal. The modulated orthogonal downstream carriers are transmitted over the distribution network to remote locations.
摘要:
The communication system includes a hybrid fiber/coax distribution network. A head end provides for downstream transmission of telephony and control data in a first frequency bandwidth over the hybrid fiber/coax distribution network and reception of upstream telephony and control data in a second frequency bandwidth over the hybrid fiber/coax distribution network. The head end includes a head end multicarrier modem for modulating at least downstream telephony information on a plurality of orthogonal carriers in the first frequency bandwidth and demodulating at least upstream telephony information modulated on a plurality of orthogonal carriers in the second frequency bandwidth. The head end further includes a controller operatively connected to the head end multicarrier modem for controlling transmission of the downstream telephony information and downstream control data and for controlling receipt of the upstream control data and upstream telephony information. The system further includes service units, each service unit operatively connected to the hybrid fiber/coax distribution network for upstream transmission of telephony and control data in the second frequency bandwidth and for receipt of the downstream control data and telephony in the first frequency bandwidth. Each service unit includes a service unit multicarrier modem for modulating at least the upstream telephony information on at least one carrier orthogonal at the head end terminal to another carrier in the second frequency bandwidth and for demodulating at least downstream telephony information modulated on at least a band of a plurality of orthogonal carriers in the first frequency bandwidth. Each service unit also includes a controller operatively connected to the service unit multicarrier modem for controlling the modulation of and demodulation performed by the service unit multicarrier modem. A method of monitoring communication channels, a distributed loop method for adjusting transmission characteristics to allow for transmission of data in a multi-point to point communication system, a polyphase filter technique for providing ingress protection and a scanning method for identifying frequency bands to be used for transmission by service units are also included.
摘要:
In a point to multipoint network, which uses multicarrier transmission, the upstream transmission are so synchronised that they are orthogonal when they arrive at the head end.
摘要:
A communication system includes a hybrid fibre/coax distribution network. A head end generates a master clock signal and derives a head end RF clock signal locked in frequency to the master clock signal. A head end symbol clock signal is derived, locked in frequency to the master clock signal, and multiple strings of downstream digital data are converted to sequences of symbols at times determined by the symbol clock signal. The symbols are modulated onto multiple orthogonal carriers having frequencies determined by the RF clock signal. The modulated orthogonal downstream carriers are transmitted over the distribution network to remote locations.