6.5. SHDSL Transceiver Operations
6.5.1. SHDSL PMD Layer
The core technology for SHDSL is based on that of HDSL2, namely, 16-level trellis coded PAM (16TC-PAM). The fundamental difference is that HDSL2 was designed to optimize performance for the transport of 1.544 Mb/s in support of provisioning T1 service on a single wire pair. SHDSL uses 16TC-PAM technology for the provisioning of multirate symmetric services, where the loop distance and noise environment determines the maximum bit rate to be supported on a single wire pair. The payload bit rates defined by SHDSL range from 192 kb/s to 2.312 kb/s in increments of 8 kb/s. The overhead may be either 8 kb/s or 16 kb/s. Generally, the use of 16 kb/s as overhead is a carryover from HDSL. Because ...
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