| 摘要 |
A digital communications network system for multiple access has a head-end node and at least one station node at at least one other end node; the system comprises a head-end controller (3) capable of transmitting data and medium-access control information to at least one station (6), preferably a plurality of station means, over a set of downstream channels within a first frequency range, and receiving information from the station or stations over an upstream channel within a second frequency range; the upstream channel comprises at least one upstream subchannel, preferably a plurality of upstream subchannels; the system further comprises at least one connection, preferably a plurality of connections, for connecting the head-end controller with the station or stations; each station includes means for receiving data and medium-access control information from the head-end controller; further means are provided for sending a data stream at a first signal level over at least one upstream subchannel, preferably a plurality of upstream subchannels; the station further includes means for sending at least one ranging request message to the head-end controller over at least one upstream subchannel; the ranging request message of messages has/have a signal level that is lower than the first signal level of the data stream; the ranging request message or messages is/are being transmitted using repetition coding enabling the head-end controller to detect the ranging request message or messages having a signal level lower than the first signal level of the data stream; the repetition coding is selected for enhancing the level of spectral containment of the ranging request message(s) and for reducing interference with transmission over adjacent upstream subchannels.
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