Spectrally efficient broadband transmission system

A communication system comprising a plurality of node devices, each one of said node devices having means for

• accepting a packet of digital data from a controlling unit, modulating the data onto a radio frequency carrier, and inserting a hole in the transmission at a predetermined location relative to the start of the packet whereby no data from the packet is lost by inserting the hole, recovering a digital bit stream from a continuous radio frequency signal, identifying the beginning a data packet, locating and removing the hole from the packet and transmitting the reconstructed packet to the controlling unit, and detecting the presence of a collision alarm in the received signal, indicated by a specific pattern of phase shift in the recovered bit stream,
• a first broadband communication medium coupled to said node device,
• a second broadband communications medium coupled to said node device, and
• a headend device having demodulator means coupled to said first broadband communications medium for receiving signals upstream from said node devices, and having modulator means coupled to said second broadband communications medium for transmitting continuous signals downstream to said node devices, the demodulator means comprising means for recovering the transmitting data packet, identifying the beginning of the packet, locating the transmitted hole, and detecting the signal level present on the said first medium during the transmission of the hole, a signal level which exceeds a minimum threshold being interpreted as a collision of a plurality of transmitted signals, said modulator means comprising means for transmitting a continuous bit pattern as downstream in the absence of a received signal, remodulating and transmitting the received data packet when an upstream signal is present, and transmitting an alarm signal when a collision is detected, the alarm signal being pseudosilence with a specific pattern of phase shift imposed on the transmitted bit stream.

A method of communicating a baseband signal over a broadband transmission medium comprising the steps of

• establishing a packet of baseband digital data to be transmitted, said packet including a signal with a phase shifted bit stream indicating a collision of transmitted packets,
• inserting a gap in said packet of digital data, modulating a first radio frequency carrier with said packet of digital data to provide a modulated first radio frequency carrier,
• transmitting said modulated first radio frequency carrier over the broadband transmission medium,
• receiving and demodulating said modulated first radio frequency carrier to obtain said packet of digital data, monitoring said gap in said packet of digital data for the presence of digital data thereby determining if a plurality of packets of data have been transmitted simultaneously and a collision of data packets has occurred,
• modulating a second radio frequency carrier with said packet of digital data to obtain a modulated second radio frequency carrier, and
• transmitting said modulated second radio frequency carrier over the broadband transmission medium.