Single carrier frequency division multiple access communication system
A method and apparatus for equalization in a communication system. The method includes receiving an input of a block of symbols, filtering the input in the frequency domain, calculating an error factor in the time domain based on the filtered input, updating tap weights of the equalizer in the frequency domain using circular correlation based on the error factor and the conjugate of the input in the frequency domain, and outputting the filtered input.
1. An apparatus for equalization in a single carrier frequency division multiple access communication system, the apparatus comprising:
processing circuitry configured to
receive an input of a block of symbols, the block symbols being periodic transmitted symbols and being circularly convoluted by a channel,
calculate a digital Fourier transform of the input by applying an N-point discrete Fourier transform or an M-point inverse discrete Fourier transform,
filter the input in the frequency domain based on tap weights,
calculate an error factor in the time domain based on the filtered input,
update the tap weights in the frequency domain using circular correlation based on a conjugate of an element wise multiplication between the error factor and the conjugate of the input in the frequency domain, and
output the filtered input, wherein updating the tap weights includes applying
k+1 = k −μD ( * k k )*
where Ω is a tap weight vector in the frequency domain, Ψ is the input in the frequency domain, E is an error factor in the frequency domain, D is a predefined matrix, ε is element wise multiplication, k is a number of blocks, and μ is a predetermined factor.
2. The apparatus of claim 1 , wherein the processing circuitry is configured to:
initialize the tap weights using central spike.
3. The apparatus of claim 1 , wherein the processing circuitry is configured to:
normalize each frequency bin as a function of the spectral power associated with input data associated with each frequency bin.
4. The apparatus of claim 1 , wherein calculating the error factor includes applying
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where R is a constant, k is a number of blocks, n is a number of equalizer input, and z is the filtered input.
5. The apparatus of claim 1 , wherein calculating the error factor includes applying
e k ( n )=4 z ( n )(| z ( n )| 2 −R )
where R is a constant, k is a number of blocks, n is a number of equalizer input, and is the filtered input.
6. The apparatus of claim 1 , wherein calculating the error factor includes applying
e k ( n )=2 └z R ( n )( z R 2 ( n )− R 1,R )+ jz I ( n )( z I 2 ( n )− R 1,I )┘
where R is a constant, k is a number of blocks, n is a number of equalizer input, and z is the filtered input.