Transmitter and method for digital multi-carrier transmission

1. A transmitter employing a digital wavelet multi-carrier modulation, said transmitter comprising:

a preamble data generator that generates preamble data and outputs the preamble data;

a modulator that modulates the preamble data, generates a plurality of subcarriers, and outputs a composite wave of time waves of the plurality of subcarriers; and

a ramp processor that performs ramp processing on the composite wave by multiplying the composite wave with a ramp function comprising a first portion having a zero value and a second portion that ramps up from said first portion, wherein said second portion begins at a predetermined delay from a reference position of the composite wave in a manner such that the length of the composite wave is shortened.

2. The transmitter according to claim 1 , wherein said predetermined delay is one symbol interval delay or less from the reference position of the composite wave.

3. The transmitter according to claim 1 , wherein said predetermined delay is more than one symbol interval delay from the reference position of the composite wave.

4. The transmitter according to claim 1 , wherein the composite wave localizes in time and frequency domain.

5. The transmitter according to claim 1 wherein the modulator comprises:

a symbol mapper that transforms the preamble data to symbol data; and

an inverse wavelet transformer that performs an inverse wavelet transform of the symbol data, generates a plurality of subcarriers, and outputs a composite wave of time waves of the plurality of subcarriers.

6. The transmitter according to claim 5 , wherein said preamble data generator generates the preamble data by giving, for each subcarrier, the same bit value in a series of symbol intervals.

7. The transmitter according to claim 5 , wherein said ramp processor performs the ramp processing to the preamble data from the first symbol interval having a proper sine wave.

8. The transmitter according to claim 5 , wherein said ramp processor performs the ramp processing for one symbol interval or more.

9. The transmitter according to claim 8 wherein said ramp processor performs the ramp processing to the preamble data from the first symbol interval having a proper sine wave.

10. The transmitter according to claim 5 wherein:

said symbol mapper further maps the symbol data into complex coordinates and outputs mapped data,

said modulator comprises both a serial-to-parallel transformer that transforms the mapped data inputted serially into parallel data and a complex decomposer that decomposes the parallel data into in-phase component and quadrature component and outputs both the in-phase component and the quadrature component, and

said inverse wavelet transformer further comprises M real coefficient wavelet filters which are orthogonal with respect to each other (M being a positive integer) and that receives the in-phase and quadrature component as (2n−1)th and (2n)th inputted data, respectively, and performs a wavelet transform of the inputted data.

11. The transmitter according to claim 10 , wherein said inverse wavelet-transformer further comprises:

a fast discrete cosine transformer that performs a cosine transform on the inputted data to produce transformed data;

a prototype filter that comprises a real coefficient polyphase filter, an adder, and a multiplier, and that filters the transformed data to produce filtered data;

M up-samplers that perform an up-sampling on the filtered data to produce up-sampled data; and

M-1 delays that delay the up-sampled-data by a certain period.

12. The transmitter according to claim 5 wherein:

said symbol mapper further maps the symbol data into M/2 complex coordinates, where M is the number of subcarriers,

said modulator comprises a serial-to-parallel transformer that serially receives the mapped symbol data and transforms the mapped symbol data into parallel data and a complex decomposer that decomposes the parallel data into real and imaginary parts, and

said inverse wavelet transformer comprises M real-coefficient orthogonal wavelet filters that cooperate to inverse wavelet transform both the real and imaginary parts into the composite wave.

13. The transmitter according to claim 1 , wherein the modulator comprises:

a symbol mapper that modulates the preamble data to produce symbol data and maps the symbol data into M/2 complex coordinates, where M is the number of subcarriers;

a serial-to-parallel transformer that serially receives the mapped symbol data and transforms the mapped symbol data into parallel data; and

an inverse wavelet transformer comprising M real-coefficient orthogonal wavelet filters that cooperate to decompose the parallel data into real and imaginary parts and inverse wavelet transform both the real and imaginary parts into the composite wave.

14. The transmitter according to claim 13 , wherein the inverse wavelet transformer comprises:

a transformer comprising one of a discrete cosine transformer (DCT) and a discrete sine transformer (DST) that DCT or DST transforms the real and imaginary parts to produce transformed data;

up-samplers that each up-sample components of the transformed data after the components of the transformed data are each respectively filtered by a separate one of the M real-coefficient orthogonal wavelet filters; and

a combining device that combines all of the up-sampled components into the composite wave.

15. The transmitter according to claim 13 , wherein the M real-coefficient orthogonal wavelet filters cooperate as a polyphase filter with an order of 2M.

16. The transmitter according to claim 13 , wherein the M real-coefficient orthogonal wavelet filters cooperate as a polyphase filter with an order greater than 2M.

17. The transmitter according to claim 13 , wherein the M real-coefficient orthogonal wavelet filters comprise:

filter banks of a length four times the symbol length that cooperate as a polyphase filter; And

the coefficient values of the M filter banks are selectively controllable to attenuate spectral components of the composite wave falling within a frequency range by 30 decibels.

18. The transmitter according to claim 1 , wherein the ramp processing comprises combining the composite wave with a linearly and monotonically increasing waveform to produce a smoothed waveform.

19. The transmitter according to claim 1 , wherein the ramp processing comprises combining the composite wave with a raised cosine waveform to produce a smoothed waveform,

20. The transmitter according to claim 1 , wherein the composite wave has a rising edge and the reference position is where the rising edge appears.

21. A transmitter employing digital wavelet multi-carrier modulation, said transmitter comprising:

a preamble data generating means for generating preamble data, and for outputting the preamble data;

a modulating means for modulating the preamble data, for generating a plurality of subcarriers, and for outputting a composite wave of the time waves of the plurality of subcarriers; and

a ramp processing means for performing ramp processing on the composite wave by multiplying the composite wave with a ramp function comprising a first portion having a zero value and a second portion that ramps up from said first portion, wherein said second portion begins at a predetermined delay from a reference position of the composite wave in a manner such that the length of the composite wave is shortened.

22. A transmitting method employing digital wavelet multi-carrier modulation, said transmitting method comprising:

generating preamble data and outputting the preamble data;

modulating the preamble data, generating a plurality of subcarriers, and outputting a composite wave of the time waves of the plurality of subcarriers; and

performing ramp processing on the composite wave by multiplying the composite wave with a ramp function comprising a first portion having a zero value and a second portion that ramps up from said first portion, wherein said second portion begins at a predetermined delay from reference position of the composite wave in a manner such that the length of the composite wave is shortened.

23. A transmitter employing a digital wavelet multi-carrier modulation, said transmitter comprising:

a preamble data generator that generates preamble data and outputs the preamble data;

a modulator that modulates the preamble data, generates a plurality of subcarriers, and outputs a composite wave of time waves of the plurality of subcarriers, said composite wave having a first length; and

a ramp processor that performs ramp processing on the composite wave by multiplying the composite wave with a ramp function comprising a first portion having a zero value and a second portion that ramps up from said first portion, wherein said second portion begins at a predetermined delay from a reference position of the composite wave such that the length of the composite wave is changed to have a second length shorter than said first length.

24. A transmitter employing digital wavelet multi-carrier modulation, said transmitter comprising:

a preamble data generating means for generating preamble data, and for outputting the preamble data;

a modulating means for modulating the preamble data, for generating a plurality of subcarriers, and for outputting a composite wave of the time waves of the plurality of subcarriers, said composite wave having a first length; and

a ramp processing means for performing ramp processing on the composite wave by multiplying the composite wave with a ramp function comprising a first portion having a zero value and a second portion that ramps up from said first portion, wherein said second portion begins at a predetermined delay from a reference position of the composite wave such that the length of the composite wave is changed to have a second length shorter than said first length.

25. A transmitting method employing digital wavelet multi-carrier modulation, said transmitting method comprising:

generating preamble data and outputting the preamble data;

modulating the preamble data, generating a plurality of subcarriers, and outputting a composite wave of the time waves of the plurality of subcarriers, said composite wave having a first length; and

performing ramp processing on the composite wave by multiplying the composite wave with a ramp function comprising a first portion having a zero value and a second portion that ramps up from said first portion, wherein said second portion begins at a predetermined delay from a reference position of the composite wave such that the length of the composite wave is changed to have a second length shorter than said first length.