Method for equalization in a 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. A method for equalization in a single-carrier frequency division multiple access communication system, the method comprising:
receiving an input of a block of symbols, the block symbols being periodic transmitted symbols and being circularly convoluted by a channel;
calculating a digital Fourier transform of the input by applying an N-point discrete Fourier transform or an M-point inverse discrete Fourier transform,
filtering, using processing circuitry of an equalizer of a receiver, 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 a conjugate of an element wise multiplication between the error factor and the conjugate of the input in the frequency domain; and
outputting the filtered input, wherein updating the tap weights includes applying
Ω k+1 =Ω k −μD (Ψ k *εE 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 method of claim 1 , further comprising:
initializing the tap weights of the equalizer using central spike.
3. The method of claim 1 , further comprising:
normalizing each frequency bin as a function of the spectral power associated with input data associated with each frequency bin.
4. The method 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 equalizer output.
5. The method of claim 1 , wherein calculating the error factor includes applying
e k ( n )=4 z (| z ( n )| 2 −R )
where R is a constant, k is a number of blocks, n is a number of equalizer input, and z is the equalizer output.
6. The method 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 1 ( n )( z 1 2 ( n )− R 1,I )┘
where R is a constant, n is a number of equalizer input, k is a number of blocks, and z is the equalizer output.