| 摘要 |
To alleviate the requirement to back-off all up-link performance, such as by limiting power spectral density, to overcome far-end cross-talk problems otherwise associated with relatively short loop-length wireline links, the present invention partitions the frequency spectrum based on an estimate of the loop length of a subscriber unit (CPE) modem from an exchange (LTE) modem. Up to a threshold frequency (f max) at which received transmissions from a subscriber having a longest loop length (115) become indistinguishable by the LTE modem from a noise floor (102), up-link performance on all loop lengths is limited to correspond to that of the longest loop. At frequencies above the threshold frequency (f max), subsets of subscribers (152-154) having relatively short loop lengths (116-119) use high frequency carriers that have signal to noise ratios sufficient to support information transmission in these elevated frequency bands. Within each subset of subscribers, backing-off of performance to that of the longest loop length within the subset is, however, necessary to avoid FEXT, as shown in FIG. 4. The higher frequency bands are used to support up-link transmission complementary to or mutually exclusive with up-link transmissions using frequencies below the threshold frequency (f max) and so, respectively, provide increased channel capacity or reduced cross-talk.
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