Patent ID: 7031344
Filing Date: 2006-04-18
Classification: H03M,H04B,H04H,H04J,H04L,H04N,H04W

Abstract:
1. A remote unit modem to transmit digital data upstream to a headend modem comprising: a digital data receiver for receiving downstream digital data transmitted from said headend modem modulated by a modulation scheme, said downstream digital data either encoding a master clock generated at said headend modem in payload data or other data, said master clock being used to transmit said downstream data, or said downstream data including said master clock as well as payload data, said digital data receiver functioning to recover said downstream payload data and said master clock and generating an upstream clock from said recovered master clock; a digital data transmitter for coupling to a source of upstream digital payload data from one or more sources, and coupled to receive said upstream clock generated from said recovered master clock and using said upstream clock to transmit known preamble data and, subsequently, transmitting said upstream digital payload data using a modulation method, and, if necessary to separate upstream payload data from several upstream data sources, using a multiplexing method, wherein said digital data receiver receives downstream payload data transmitted in frames from said headend modem and includes means to recover said master clock from downstream frame marker data transmitted to mark the beginning of every downstream frame, said downstream frame marker data encoding said master clock, and wherein said receiver or transmitter includes means to recover data transmitted by said headend modem from which a frame marker can be generated such that said downstream frames can be counted by said remote unit modem, and wherein said transmitter and/or receiver includes means for counting received downstream frames and for counting upstream frames transmitted by said remote unit modem, and for carrying out ranging by receiving a frame from said headend modem having any frame number and responding by sending back a response frame which includes a total turnaround time service request and the frame number of the downstream frame just received, and for receiving back a frame which includes the total turnaround time for said remote unit modem in the form of the difference between the headend modem's downstream frame count at the time said response frame is received and the downstream frame number included in the response frame, and said transmitter including means for using said total turnaround time along with spreading code assignments transmitted to said remote unit modem from said headend modem so as to use the proper spreading codes to spread the spectrum of data during specific upstream frames.