| 摘要 |
An improved digital bi-directional communications transceiver in which the upstream and downstream portions of the frequency spectrum are allocated different bandwidths and positioned at different locations on the frequency spectrum in response to transmission line conditions and impairments such as system provisioning, background noise, radio frequency interference (RFI), crosstalk and reflected signals. The movement of the upstream and downstream carrier frequencies are elastic in that they may be adjusted in near real-time involving methods for determining the signal quality parameter(SQP) of the received signal. The SQP is used to estimate the bit error rate (BER) margin on the received data and also takes into account the total signal to interference ratio (SIR), where the interference includes crosstalk, RFI, and residual echo from the neighboring upstream or downstream channel. Because the carrier frequencies of the upstream and downstream channels are being dynamically allocated, it is necessary to implement a robust carrier acquisition, recovery and lock algorithm. The robust carrier algorithms allow carrier recovery of the transmitted upstream and downstream signals independent of the particular modulation or symbol rate.
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