Apparatus and method for bandwidth management in a multi-point OFDM/DMT digital communications system

In a multi-point communications system having an allocated total bandwidth, a method comprising:

• receiving OFDM/DMT (Orthogonal Frequency Division Multiplexing/Discrete Multi Tone) modulated data from a plurality of remote transceivers over a predetermined number of bins, the OFDM/DMT modulated data corresponding to a first data stream from a first one of the plurality of remote transceivers over one or more bins of a first subset of the predetermined number of bins and OFDM/DMT data corresponding to a second data stream from a second one of the plurality of remote transceivers over one or more bins of a second subset of the predetermined number of bins;
• monitoring actual bandwidth usage of the total allocated bandwidth;
• transmitting from the first transceiver the OFDM/DMT data over the one or more bins of the first subset of bins and receiving at the first transceiver one or more commands in response to monitoring the actual bandwidth usage to direct the transceiver to transmit in either an X QAM (Quadrature Amplitude Modulation) mode or a Y QAM mode on the one or more bins of the first subset of bins, where X and Y are different integer numbers reflecting a constellation size used for the data transmission in a bin and where X>Y, QAM mode switching occurring without substantially effecting the data rate of the first data stream;
• and
• transmitting from the second transceiver the OFDM/DMT data over the one or more bins of the second subset of bins and receiving at the second transceiver one or more commands from the head end unit in response to head end measurement of the bandwidth usage to direct the transceiver to transmit in either an X QAM mode or a Y QAM mode on the one or more bins of the second subset of bins, where X and Y are different integer numbers reflecting a constellation size used for data transmission in a bin and where X>Y, QAM mode switching occurring without substantially affecting the data rate of the first data stream.

In a multi-point communications system having an allocated bandwidth dedicated to communications for the multi-point communications system, apparatus comprising:

• means for transmitting from a primary site OFDM/DMT (Orthogonal Frequency Division Multiplexing/Discrete Multi Tone) modulated data over a predetermined number of bins to a plurality of remote transceivers, the OFDM/DMT modulated data corresponding to a first data stream transmitted to a first one of the plurality of remote transceivers over one or more bins of a first subset of the predetermined number of bins and the OFDM/DMT modulated data corresponding to a second data stream transmitted to a second one of the plurality of remote transceivers over one or more bins of a second subset of the predetermined number of bins, the primary site having at least an X QAM (Quadrature Amplitude Modulation) mode of transmission for transmitting X QAM modulated data in any given one of the first and second subsets of bins and a Y QAM mode of transmission for transmitting Y QAM modulated data in any given one of the first and second subset of bins, where X and Y are different integer numbers reflecting a constellation size used for data transmission in a bin and where X>Y, the primary site also monitoring bandwidth used in the system and comparing the used bandwidth to a predetermined bandwidth threshold value;
• means for receiving at the first transceiver the OFDM/DMT data over the one or more bins of the first subset of bins and transmitting one or more data segments to the primary site corresponding to measurements of signal-to-noise ratios for the one or more bins of the first subset of bins, the primary site using the one or more data segments to direct the first transceiver to receive in either the X QAM mode or the Y QAM mode on the one or more bins of the first subset of bins without substantially effecting the data rate of the received first data stream when the predetermined bandwidth threshold value is exceeded and the measured signal-to-noise ratios (SNR) in the one or more bins of the first subset of bins is above a predetermined SNR threshold value;
• and
• means for receiving at the second transceiver the OFDM/DMT data from the transmission medium over the one or more bins of the second subset of bins and transmitting one or more data segments to the primary site corresponding to measurements of signal-to-noise ratios for the one or more bins of the second subset of bins, the head end unit using the one or more data segments to direct the second transceiver to receive in either the X QAM mode or the Y QAM mode on the one or more bins of the first subset of bins without substantially affecting the data rate of the received first data stream when the predetermined bandwidth threshold value is exceeded and the measured signal-to-noise ratios in the one or more bins of the second subset of bins is above a predetermined SNR threshold value.

In a multi-point communications system having an allocated total bandwidth, apparatus comprising:

• means for receiving OFDM/DMT (Orthogonal Frequency Division Multiplexing/Discrete Multi Tone) modulated data from a plurality of remote transceivers over a predetermined number of bins, the OFDM/DMT modulated data corresponding to a first data stream from a first one of the plurality of remote transceivers over one or more bins of a first subset of the predetermined number of bins and OFDM/DMT data corresponding to a second data stream from a second one of the plurality of remote transceivers over one or more bins of a second subset of the predetermined number of bins;
• means for monitoring actual bandwidth usage of the total allocated bandwidth;
• means for transmitting from the first transceiver the OFDM/DMT data over the one or more bins of the first subset of bins and receiving at the first transceiver one or more commands in response to monitoring the actual bandwidth usage to direct the transceiver to transmit in either an X QAM (Quadrature Amplitude Modulation) mode or a Y QAM mode on the one or more bins of the first subset of bins, where X and Y are different integer numbers reflecting a constellation size used for the data transmission in a bin and where X>Y, QAM mode switching occurring without substantially effecting the data rate of the first data stream;
• and
• means for transmitting from the second transceiver the OFDM/DMT data over the one or more bins of the second subset of bins and receiving at the second transceiver one or more commands from the head end unit in response to head end measurement of the bandwidth usage to direct the transceiver to transmit in either an X QAM mode or a Y QAM mode on the one or more bins of the second subset of bins, where X and Y are different integer numbers reflecting a constellation size used for data transmission in a bin and where X>Y, QAM mode switching occurring without substantially affecting the data rate of the first data stream.