DSL Advances

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 ...