| 摘要 |
The performance of digital subscriber loops is tested through transmission, reception and analysis of a multi-tone power ratio (MTPR) waveform, containing plural discrete tones having equal spectral spacings and notches periodically distributed among the tones. The noise floor at a missing sub-carrier spectral location is integrated and compared to signal power of an adjacent sub-carrier within the test vector waveform. From these two values, MTPR is determined for various carrier locations, so that maximum theoretical loop payload can be calculated. To generated a figure of merit (FOM) under test, a data modem is placed at each end of the loop. The FOM obtained from MTPR analysis is channel based, not equipment based, and is independent of receiver implementation. Before placing a new customer in service, the MTPR FOMs for a number of loops are compared to bit rate information in a database, which correlates MTPR with a bit rate for a specific modem. Given the terminal equipment, MTPR FOMs, and the customer's data rate, one or more cable pairs that satisfy or exceed the FOM within an available cable bundle may be selected.
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