Filter for impulse response shortening with additional spectral constraints for multicarrier transmission

摘要

A channel in a multiple carrier communication system is equalized by computing a desired spectral response, shortening the impulse response of the channel so that a significant part of an energy of the impulse response is confined to a region that is shorter than a target length and filtering the signal based on the desired spectral response. A multiple carrier communication system may include a primary impulse shortening filter that receives an output signal of an analog to digital converter and accepts coefficients. A secondary impulse shortening filter may receive the output signal of the analog to digital converter, output an output signal, and pass coefficients to the primary impulse shortening filter. A reference signal generator may output a reference signal. A comparator may compare the output signal and the reference signal and output a resulting error signal. An adaptive processor may compute coefficients for the secondary impulse shortening filter based on the error signal.

主权项

1. A digital filter for a multiple carrier, multi-channel, communication system, the digital filter comprising:
a digital filter structure configured to apply a frequency characteristic according to a filter characteristic, g(n), to a digital Orthogonal Frequency Division Multiplexing (OFDM) signal; taps coupled to the digital filter structure and configured to receive digital filter coefficients,
the number of digital filter coefficients being less than or equal to a number of coefficients to set an effective length of convolution of the filter characteristic with an impulse response of the communication channel, g(n)*h(n), less than a target length; andthe filter structure configured to apply, via the taps, coefficients adjusted according to a cost function, to minimize a difference between a desired spectral response, Gd(ω), and an actual spectral response, G(ω), of the digital filter to adjust the filter characteristic, g(n).