Pulse or digital communications – Systems using alternating or pulsating current – Plural channels for transmission of a single pulse train
Reexamination Certificate
1999-02-24
2003-06-03
Corrielus, Jean (Department: 2631)
Pulse or digital communications
Systems using alternating or pulsating current
Plural channels for transmission of a single pulse train
C370S464000
Reexamination Certificate
active
06574282
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a multi-carrier transmission system a transmission unit and a transmission method. More particularly, the invention relates to a multi-carrier transmission system, a transmission unit and a transmission method known as a Discrete Multi-Tone (DMT) modulation system.
2. Description of the Related Art
As an example of the conventional DMT type multi-carrier transmission system of this kind, there is a technology disclosed in U.S. Pat. No. 5,479,447. Such multi-carrier transmission system measures a signal to noise ratio (SNR) of respective carriers for bit distribution of a plurality of carriers, and for deriving bit distribution according to the measured SNR.
A problem in such prior art resides in small transmission amount. The reason is that when a periodically varying noise is generated and if communication is to be established at a certain error rate, bit distribution and power distribution is performed with reference to an average value of SNR of each carrier. Thus, bit distribution and power distribution are limited to only one kind of average value of SNR to inherently make the data transmission amount small.
SUMMARY OF THE INVENTION
Therefore, the present invention has been worked out for solving the drawback in the prior art. An object of the present invention to provide a multi-carrier transmission system, a transmission unit and a transmission method, which can efficiently perform data transmission in a condition where a noise is generated periodically.
According to one aspect of the present invention, a multi-carrier transmission system is characterized by performing data transmission by deriving a bit distribution of each carrier of multi-carrier depending upon a periodically varying noise period. Then, the bit distribution of each of the carrier is derived by using a clock synchronized with the periodically varying noise and depending upon a period of the clock. A transmission power distribution of each of the carrier is derived together with the bit distribution of each of the carrier.
Another multi-carrier transmission system according to the present invention, comprises:
a first unit performing quadrature amplitude modulation using each of the carrier and multiplexing modulated carrier using inverse Fourier transformation; and
a second unit demodulating each of the carrier from the signal multiplexed in the first unit using Fourier transformation.
On the other hand, the first unit comprises a circuit for transmitting a tone synchronized with the clock with varying level and a circuit for transmitting a pseudo random signal having all components of respective carriers, and
the second unit comprises a circuit for detecting a period of noise on the basis of the level of the tone from the first unit, a circuit for deriving a signal to noise ratio of the pseudo random signal per detected period and a circuit for deriving one of a transmission power distribution and bit distribution, and bit distribution of the carrier on the basis of the signal to noise ratio. Then, the second circuit comprises a circuit for transmitting any one of derived transmission power distribution and the bit distribution, and the bit distribution of each of the carrier to the first unit, and the first unit comprises a circuit for performing data transmission to the second unit according to one of the transmission power distribution and bit distribution, and the bit distribution per the noise period from the second unit. The second unit comprises a circuit for transmitting a pseudo random signal having all components of each of the carriers, and the first unit comprises a circuit for deriving a signal to noise ratio of the pseudo random signal from the first unit per each noise period, and a circuit for deriving one of a transmission power distribution and bit distribution, and bit distribution of the carrier on the basis of the signal to noise ratio. The first unit comprises a circuit for transmitting the transmission power distribution and the bit distribution of each of the carriers derived to the second unit, the second unit comprises a circuit for performing data transmission to the first unit according to one of the transmission power distribution and bit distribution, and the bit distribution per the noise period from the first unit. The first unit initiates transmission operation in response to a transmission start command for own unit from the second unit. A data transmission through a digital subscriber line is performed between the first unit and the second unit. The bit distribution is effected to distribute greater number of bits when the noise periodically varying between large and small is small than that when the noise is large. The bit distribution is effected to distribute greater number of bits when the noise periodically varying is far end crosstalk than that when the noise is near end crosstalk.
According to the second aspect of the present invention, a multi-carrier transmission unit performing transmission by multi-carrier, characterized by performing data transmission by deriving a bit distribution of each carrier of multi-carrier depending upon a period of periodically varying noise. The bit distribution of each of the carrier is derived by using a clock synchronized with the periodically varying noise and depending upon a period of the clock. A transmission power distribution of each of the carrier is derived together with the bit distribution of each of the carrier. The multi-carrier transmission unit performs quadrature amplitude modulation using the each carrier and multiplies the modulated carrier using inverse Fourier transformation.
On the other hand, the multi-carrier transmission unit further comprises a circuit for transmitting a tone synchronized with the clock with varying level and a circuit for transmitting a pseudo random signal having all components of respective carriers.
The multi-carrier transmission unit further comprises a circuit for detecting a period of noise on the basis of the level of the tone from another unit, a circuit for deriving a signal to noise ratio of the pseudo random signal per detected period and a circuit for deriving one of a transmission power distribution and bit distribution, and bit distribution of the carrier on the basis of the signal to noise ratio. The multi-carrier transmission unit further comprises a circuit for transmitting any one of derived transmission power distribution and the bit distribution, and the bit distribution of each of the carrier to the another unit. The multi-carrier transmission unit further comprises a circuit for deriving a signal to noise ratio of the pseudo random signal from the another unit per each noise period, and a circuit for deriving one of a transmission power distribution and bit distribution, and bit distribution of the carrier on the basis of the signal to noise ratio. The multi-carrier transmission unit further comprises a circuit for transmitting one of the transmission power distribution and the bit distribution, and the bit distribution of each of the carriers derived, to the another unit.
The multi-carrier transmission unit initiates transmission operation in response to a transmission start command for own unit from the another unit. A data transmission through a digital subscriber line is performed between own unit and the another unit. The bit distribution is effected to distribute greater number of bits when the noise periodically varying between large and small is small than that when the noise is large. The bit distribution is effected to distribute greater number of bits when the noise periodically varying is far end crosstalk than that when the noise is near end crosstalk.
According to the third aspect of the present invention, a multi-carrier transmission method characterized by performing data transmission by deriving a bit distribution of each carrier of multi-carrier depending upon a periodically varying noise period. The bit distribution of each of the carrier is deriv
Corrielus Jean
NEC Corporation
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