Spread spectrum bit allocation algorithm
First Claim
1. A method for use in a data modulator for allocating bits to data channel frequencies comprising the steps of:
- storing mask power level data representing a respective maximum power level for each of said data channel frequencies;
storing aggregate power level representing a total amount of signal power to be applied in all of said data channel frequencies;
allocating bits, such that bits are allocated up to said respective maximum power level for each of said data channel frequencies and such that each of said bits is allocated to a single respective one of said data channel frequencies; and
when said aggregate power level is not substantially reached in said step of allocating, further allocating bits to multiples of said data channel frequencies for transmission at reduced power rates per channel frequency, to permit further bits to be allocated, until an aggregate power limit is substantially reached and said respective maximum power level is reached.
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Abstract
High transmission capacity in a twisted pair signal line, where power is limited by a power spectral-density mask and an aggregate signal power constraint, is obtained by: (1) allocating data to multitone sub-bands according to a lowest marginal power-cost per bit scheme and (2) in an environment where an aggregate power budget remains after all bits have been allocated to all sub-bands with sufficient margins to carry a bit, assigning additional bits to sub-bands with otherwise insufficient power margins to carry a single bit, by frequency-domain-spreading a single bit across several sub-bands at correspondingly reduced power levels, to permit the otherwise unacceptable noise levels to be reduced on average by despreading at the receiving end. Another feature of the invention, applicable in an environment in which multiple interfering channels are employed, provides increased signal throughput by (3) transmitting coherently in a number of multitone sub-bands, identical blocks of data, with the number of multitone sub-bands being equal to a number of interfering channels and multiplying the signal carried by corresponding sub-bands in the separate interfering channels by a different respective vector from an orthonormal basis set so that near-end cross-talk is eliminated upon despreading at the receiving end.
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Citations
7 Claims
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1. A method for use in a data modulator for allocating bits to data channel frequencies comprising the steps of:
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storing mask power level data representing a respective maximum power level for each of said data channel frequencies; storing aggregate power level representing a total amount of signal power to be applied in all of said data channel frequencies; allocating bits, such that bits are allocated up to said respective maximum power level for each of said data channel frequencies and such that each of said bits is allocated to a single respective one of said data channel frequencies; and when said aggregate power level is not substantially reached in said step of allocating, further allocating bits to multiples of said data channel frequencies for transmission at reduced power rates per channel frequency, to permit further bits to be allocated, until an aggregate power limit is substantially reached and said respective maximum power level is reached. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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Specification