6.6 SHDSL Performance

   


For SHDSL the PSD in the downstream direction is the same as that in the upstream direction. This is also true for 2B1Q SDSL. When the upstream and downstream channels use the same PSD shape, the PSDs are termed symmetric PSDs.

For the case of symmetric PSDs, the total transmit power is fixed to maximum value of 13.5 dBm. When these systems are deployed in the cable, the worst case disturbance is near-end crosstalk from the same system. Specifically, for an echo canceled system with symmetric PSD, assuming that all of the systems in the cable have the same transmit power, the worst-case disturbance is near-end crosstalk from other systems with exactly the same spectrum. Figure 6.18 shows the bit-rate versus distance of 26-gauge wire for both SHDSL using 16-level TC-PAM and 2B1Q SDSL in the presence of 49 self-near-end crosstalk (SNEXT) disturbers. These simulation results assume 6 dB of margin in all cases. The better performance of TC-PAM is due to inclusion of a trellis code with 5.1 dB of coding gain.

Figure 6.18. SHDSL and 2B1Q SDSL bit rates versus 24-gauge distance in presence of 49 SNEXT.

graphics/06fig18.gif


   
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DSL Advances
DSL Advances
ISBN: 0130938106
EAN: 2147483647
Year: 2002
Pages: 154

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