Adaptive allocation for variable bandwidth multicarrier communication
DCFirst Claim
1. In a multicarrier transmission system including two communication units, a method for modulation bits onto subchannels of a communication channel between the two communication units, the method comprising:
- allocating bits to subchannels of the communication channel according to a first bit allocation table;
monitoring the communication channel during transmission of the bits allocated to the subchannels according to the first bit allocation table;
developing a second bit allocation table at one of the communication units in response to monitoring the communication channel;
transmitting the second bit allocation table to the other of the communication units over the communication channel; and
storing the first and second bit allocation tables at each of the communication units.
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Abstract
Data is distributed among the channels of an asymmetric data subscriber loop (ADSL) communications system in accordance with an adaptive algorithm which from time to time measures the signal to noise ratio of the various channels and finds a margin for each channel dependent on achievement (where possible) of a given bit error rate and a desired data transmission rate. The margin distribution is achieved by augmenting the constellation signal to noise ratio to enhance computational efficiency and allow redetermination of bit allocation tables during transmission as necessary. Pairs of bit allocation tables are maintained at the transmitter and receiver and one table of each pair at the transmitter and receiver is updated while the other pair is in use for controlling communication.
56 Citations
20 Claims
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1. In a multicarrier transmission system including two communication units, a method for modulation bits onto subchannels of a communication channel between the two communication units, the method comprising:
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allocating bits to subchannels of the communication channel according to a first bit allocation table;
monitoring the communication channel during transmission of the bits allocated to the subchannels according to the first bit allocation table;
developing a second bit allocation table at one of the communication units in response to monitoring the communication channel;
transmitting the second bit allocation table to the other of the communication units over the communication channel; and
storing the first and second bit allocation tables at each of the communication units. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. In a multicarrier transmission system including two communication units, a method for modulating bits onto subchannels of a communication channel between the two communication units, the method comprising:
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transmitting bits allocated to subchannels of the communication channel according to a first bit allocation table;
developing a second bit allocation table at one of the communication units;
transmitting the second bit allocation table to the other of the communication units over the communication channel; and
storing the first and second bit allocation tables at each of the communication units. - View Dependent Claims (13, 14)
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15. A transmitter in a multicarrier modulation system, comprising:
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a first bit allocation table specifying a first allocation of bits to subchannels used during current communication with a receiver;
a second bit allocation table specifying a different allocation of bits to subchannels than the first bit allocation table; and
a signaler transmitting a flag to synchronize from the first bit allocation table to the second bit allocation table for allocating bits to the subchannels, wherein the transmitter stores the second bit allocation table for use during subsequent communication with the receiver.
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16. A receiver in a multicarrier modulation system, comprising:
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a first bit allocation table specifying a first allocation of bits to subchannels used during current communication with a transmitter over a communication channel;
a second bit allocation table specifying a different allocation of bits to subchannels than the first bit allocation table; and
a control unit developing the second bit allocation table, wherein the receiver stores the second bit allocation table for use during subsequent communication with the transmitter.
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17. A receiver in a multicarrier modulation system, comprising:
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a first bit allocation table specifying a first allocation of bits to subchannels used during current communication with a transmitter over a communication channel;
a second bit allocation table specifying a different allocation of bits to subchannels than the first bit allocation table; and
a switch unit to receive a flag that synchronizes switching from the first bit allocation table to the second bit allocation table for allocating bits to the subchannels, wherein the receiver stores the second bit allocation table for use during subsequent communication with the transmitter.
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18. A multicarrier transmission system, comprising:
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a plurality of communication units in communication with each other over a communications channel having a plurality of subchannels, each communication unit storing a first bit allocation table that specifies a first allocation of bits to the subchannels for use during current communication with each other communication unit over the communication channel; and
a second bit allocation table, stored by each of the communication units, specifying a different allocation of bits to subchannels than the first bit allocation tables, for use during subsequent communication between the communication units, wherein one of the communication units comprises a transmitter that transmits the second bit allocation table stored by that communication unit to another of the communication units for use during the subsequent communication between the communication units.
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19. A multicarrier transmission system, comprising:
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a plurality of communication units in communication with each other over a communications channel having a plurality of subchannels, each communication unit storing a first bit allocation table that specifies a first allocation of bits to the subchannels for use during current communication with each other communication unit over the communication channel; and
a second bit allocation table, stored by each of the communication units, specifying a different allocation of bits to subchannels than the first bit allocation tables, for use during subsequent communication between the communication units, wherein one of the communication units comprises a signaler that transmits a flag to another of the communication units to synchronize switching from the first bit allocation tables to the second bit allocation tables for allocating bits to subchannels.
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20. A multicarrier transmission system, comprising:
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a plurality of communication units in communication with each other over a communications channel having a plurality of subchannels, each communication unit storing a first bit allocation table that specifies a first allocation of bits to the subchannels for use during current communication with each other communication unit over the communication channel; and
a second bit allocation table, stored by each of the communication units, specifying a different allocation of bits to subchannels than the first bit allocation tables, for use during subsequent communication between the communication units, wherein one of the communication units comprises a control unit that develops the second bit allocation tables.
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Specification