Adaptive bit swapping method and device for discrete multitone system

Claim 2

An adaptive bit swapping method in a discrete multitone (DMT) system for an asymmetric digital subscriber line (ADSL) which has a transmitter for encoding and converting data to be transmitted via a channel, and a receiver for restoring the transmitted data to the original form by conversion and decoding, said method comprising the steps of: (a) initializing said DMT system to transmit said data via said channel in a steady state; (b) selecting a frame having an inserted sync block from a frame structure of said transmitted data; (c) calculating the signal-to-noise ratios (SNRs) of respective sub-channels of the selected frame; (d) calculating first difference value between the present representative SNRs calculated in step (c) and the previous representative SNRs of each sub-channel; (e) selecting a maximum value and minimum value among the first difference values of said respective sub-channels; (f) obtaining the second difference value between said maximum value and said minimum value; (g) determining whether said second difference value is equal to or greater than the predetermined threshold value; and (h) correcting bit and power assigning tables of a transmitter and a receiver if said second difference value is greater than or equal to said threshold value.

Claim 3

An adaptive bit swapping method as claimed in claim 1, wherein said step (a) comprises the steps of: establishing the initial bits and power values of said DMT system; and starting a transmission of data in a steady state of said DMT system.

Claim 4

An adaptive bit swapping method as claimed in claim 1, wherein said step (c) comprises the steps of; measuring the signal power spectrum density (PSD) of each sub-channel by a deterministic least sequence (DLS) method; measuring a noise PSD of each sub-channel by a Welch method; and calculating the SNR of each sub-channel from said measured signal PSD and said noise PSD.

Claim 5

An adaptive bit swapping method as claimed in claim 1, wherein said steps (b) and (c) are repeatedly performed by a predetermined times, and representative SNR value of each sub-channel are calculated making use of said SNRs if a predetermined number of SNRs are obtained for each sub-channel.

Claim 6

An adaptive bit swapping method as claimed in claim 4, wherein said step (c) comprises the step of; feeding the procedure back to said step (b), if said predetermined number of SNRs of each sub-channel are not obtained.

Claim 7

An adaptive bit swapping method as claimed in claim 1, wherein said step (g) comprises the step of; feeding the procedure back to said step (b), if said second difference value is not greater than or equal to said predetermined threshold value.

Claim 8

An adaptive bit swapping device functioning as a receiver for restoring the transmitted data to the original form by conversion and decoding, said device being included in a discrete multitone (DMT) system for an asymmetric digital subscriber line (ADSL) which has a transmitter for encoding and converting data to be transmitted via a channel, said device comprising: A/D converting means for converting the analogue data signal received via said channel into a digital signal; time-domain equalizing means for receiving said digital signal and reducing a guard band used to remove an interblock interference; fast-Fourier transforming means for receiving the output of said time-domain equalizing means and demodulating said data signal modulated in said transmitter; frequency-domain equalizing means for receiving the output of said fast Fourier transforming means and compensating for a phase error of each sub-channel; SNR measuring means for obtaining the representative SNRs of respective sub-channels from the output of said A/D converting means using a frame having an inserted sync symbol from a frame structure of transmitted data, calculating first difference value between the previous representative SNR and present representative SNR for each sub-channel, comparing a threshold value with second difference between maximum and minimum value of said first difference values and outputting to a transmitter and a receiver the signal used for correcting a bit allocation table according to the compared result; and decoding means for receiving the outputs of said SNR measuring means and said frequency-domain equalizing means, resetting a slice value, and decoding the reset slice value.

Claim 9

An adaptive bit swapping device functioning as a receiver for restoring the transmitted data to the original form by conversion and decoding, said device being included in a discrete multitone (DMT) system for an asymmetric digital subscriber line (ADSL) which has a transmitter for encoding and converting data to be transmitted via a channel, said device comprising: A/D converting means for converting the analogue data signal received via said channel into a digital signal; time-domain equalizing means for receiving said digital signal and reducing a guard band used to remove an interblock interference; fast-Fourier transforming means for receiving the output of said time-domain equalizing means and demodulating said data signal modulated in said transmitter; frequency-domain equalizing means for receiving the output of said fast Fourier transforming means and compensating for a phase error of each sub-channel; SNR measuring means for obtaining the representative SNRs of respective sub-channels from the output of said A/D converting means using a frame having an inserted sync symbol from a frame structure of transmitted data, calculating first difference value between the previous representative SNR and present representative SNR for each sub-channel, comparing a threshold value with second difference between maximum and minimum value of said first difference values and outputting to a transmitter and a receiver the signal used for correcting a bit allocation table according to the compared result; and decoding means for receiving the outputs of said SNR measuring means and said frequency-domain equalizing means, resetting a slice value, and decoding the reset slice value.

Claim 10

An adaptive bit swapping device functioning as a receiver for restoring the transmitted data to the original form by conversion and decoding, said device being included in a discrete multitone (DMT) system for an asymmetric digital subscriber line (ADSL) which has a transmitter for encoding and converting data to be transmitted via a channel, said device comprising: A/D converting means for converting the analogue data signal received via said channel into a digital signal; time-domain equalizing means for receiving said digital signal and reducing a guard band used to remove an interblock interference; fast-Fourier transforming means for receiving the output of said time-domain equalizing means and demodulating the data signal modulated in said transmitter; frequency-domain equalizing means for receiving the output of said fast Fourier transforming means and compensating for a phase error of each sub-channel; SNR measuring means for selecting a frame having an inserted sync block from a frame structure of said transmitted data, calculating the signal-to-noise ratios (SNRs) of respective sub-channels of the selected frame, calculating first difference value between the present representative SNRs calculated above and the previous representative SNRs of each sub-channel, selecting a maximum value and minimum value among the first difference values of said respective sub-channels, obtaining the second difference value between said maximum value and said minimum value, determining whether said second difference value is equal to or greater than a predetermined threshold value and outputting to a transmitter and a receiver the signal used for correcting bit and power assigning tables of a transmitter and a receiver; and decoding means for receiving the outputs of said SNR measuring means and said frequency-domain equalizing means, resetting a slice value, and decoding said reset slice value.

Claim 11

An adaptive bit swapping device functioning as a receiver for restoring the transmitted data to the original form by conversion and decoding, said device being included in a discrete multitone (DMT) system for an asymmetric digital subscriber line (ADSL) which has a transmitter for encoding and converting data to be transmitted via a channel, said device comprising: A/D converting means for converting the analogue data signal received via said channel into a digital signal; time-domain equalizing means for receiving said digital signal and reducing a guard band used to remove an interblock interference; fast-Fourier transforming means for receiving the output of said time-domain equalizing means and demodulating the data signal modulated in said transmitter; frequency-domain equalizing means for receiving the output of said fast Fourier transforming means and compensating for a phase error of each sub-channel; SNR measuring means for selecting a frame having an inserted sync block from a frame structure of said transmitted data, calculating the signal-to-noise ratios (SNRs) of respective sub-channels of the selected frame, calculating first difference value between the present representative SNRs calculated above and the previous representative SNRs of each sub-channel, selecting a maximum value and minimum value among the first difference values of said respective sub-channels, obtaining the second difference value between said maximum value and said minimum value, determining whether said second difference value is equal to or greater than a predetermined threshold value and outputting to a transmitter and a receiver the signal used for correcting bit and power assigning tables of a transmitter and a receiver; and decoding means for receiving the outputs of said SNR measuring means and said frequency-domain equalizing means, resetting a slice value, and decoding said reset slice value.