Patent ID: 7239650

Claim:
A central unit modem apparatus comprising: a framing circuit having a memory and circuitry to receive downstream data and store said downstream data in said memory organized as frames of data each frame comprising one or more symbols, and having circuitry to read data out of said memory and present said downstream data at an output; a transmitter coupled to receive said downstream data from said output and having circuitry to multiplex and modulate said downstream data onto a transmission media, said transmitter including a ranging means for transmitting ranging data to be received by a plurality of remote unit modems to assist them in performing a ranging process so as to achieve upstream frame synchronization; and a synchronous code division multiplexed receiver coupled to receive modulated upstream signals from a plurality of remote unit modems and having circuitry to demodulate and demultiplex said upstream signals and detect upstream data from said demodulated, demultiplexed upstream signals.