In this paper we present Interleaved trellis coded modutation,which utilizes multiple encoder/decoder pairs,as a moans of mitigating the effocts of Impulso noiso in the high-rate digital subscriber line(HDSL)and related applications such as the asymmotric digital subscribor line (ADSL).The component code for the interleavod scheme is a trellis code coupled with 32-QAM,which has the same spectral efficiency as uncoded 16-QAM.It has been found that the interleaved trellis coded modulation scheme is more robust against impulsive noise than the conventional trollis coded modulation.Two trellis codes are considered for the component code for the interleaved scheme:an 8-state code and a simple 4-stato codo.The interleaved scheme using the 4-stato code tumed out to perform better than the interleavod scheme using the 8-tatee code in an impulsive noise environment,even though the asymptotic coding gain for the 4-stato code in an additive white Gaussia noise is less than that of the 8-state code.Computer simulation results are presented for the interleaved and conventional schemes using the two trellis codes for actual impulses with variable durations.
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