A computing device operating according to a frequency division multiplexed protocol in which communication occurs over a signal formed from a plurality of sub-channels selected from anywhere in a frequency spectrum. A computing device may select sub-channels cognitively by using information about sub-channels previously deemed suitable or unsuitable by that computing device or other computing devices. A described technique for determining sub-channel suitability includes analyzing radio frequency energy in the sub-channel to detect signals generated by another computing device or high noise levels. Information may also be used to cognitively select sub-channels to be analyzed, such as by first selecting for analysis previously-used sub-channels.

A computing device operating according to a frequency division multiplexed protocol in which communication occurs over a signal formed from a plurality of sub-channels selected from anywhere in a frequency spectrum. A computing device may select sub-channels cognitively by using information about sub-channels previously deemed suitable or unsuitable by that computing device or other computing devices. A described technique for determining sub-channel suitability includes analyzing radio frequency energy in the sub-channel to detect signals generated by another computing device or high noise levels. Information may also be used to cognitively select sub-channels to be analyzed, such as by first selecting for analysis previously-used sub-channels.

In some aspects, the disclosure is directed to methods and systems for improving signal to noise ratios of signals from multiple communication links. In some embodiments, a system includes a first frequency transformation circuit configured to transform a first signal in a time domain received from a first device into a corresponding second signal in a frequency domain. The system further includes a second frequency transformation circuit configured to transform a third signal in the time domain received from a second device into a corresponding fourth signal in the frequency domain. The system further includes a leg combining circuit configured to select, for a group of subcarriers, one of the first frequency transformation circuit and the second frequency transformation circuit, and cause, for the group of subcarriers, the selected frequency transformation circuit to output one of the second signal and the fourth signal, according to the selection.

In some aspects, the disclosure is directed to methods and systems for improving signal to noise ratios of signals from multiple communication links. In some embodiments, a system includes a first frequency transformation circuit configured to transform a first signal in a time domain received from a first device into a corresponding second signal in a frequency domain. The system further includes a second frequency transformation circuit configured to transform a third signal in the time domain received from a second device into a corresponding fourth signal in the frequency domain. The system further includes a leg combining circuit configured to select, for a group of subcarriers, one of the first frequency transformation circuit and the second frequency transformation circuit, and cause, for the group of subcarriers, the selected frequency transformation circuit to output one of the second signal and the fourth signal, according to the selection.

Frequency independent isolation of duplexed ports in distributed antenna systems (DASs) is disclosed. Instead of providing a duplexer in a DAS that provides frequency dependent separation between downlink and uplink communications signals, an isolation circuit is provided. The isolation circuit is coupled to a duplexed port that provides downlink communications signals to the DAS and receives uplink communications signals from the DAS. To isolate uplink communications signals from the downlink communications path, the isolation circuit includes a directional coupler. The directional coupler provides frequency independent isolation between uplink communications signals and a downlink communications path in the DAS. Further, to isolate downlink communications signals from the uplink communications path, the isolation circuit includes at least one circulator isolator. The circulator(s) acts as a one-direction device, allowing uplink communications signals to flow to the directional coupler with minimal attenuation while significantly attenuating downlink communications signals flowing from the directional coupler.

Frequency independent isolation of duplexed ports in distributed antenna systems (DASs) is disclosed. Instead of providing a duplexer in a DAS that provides frequency dependent separation between downlink and uplink communications signals, an isolation circuit is provided. The isolation circuit is coupled to a duplexed port that provides downlink communications signals to the DAS and receives uplink communications signals from the DAS. To isolate uplink communications signals from the downlink communications path, the isolation circuit includes a directional coupler. The directional coupler provides frequency independent isolation between uplink communications signals and a downlink communications path in the DAS. Further, to isolate downlink communications signals from the uplink communications path, the isolation circuit includes at least one circulator isolator. The circulator(s) acts as a one-direction device, allowing uplink communications signals to flow to the directional coupler with minimal attenuation while significantly attenuating downlink communications signals flowing from the directional coupler.

An FDM communication system in which encoding/decoding settings for different sets of tones are specified using index values assigned to different sets of tones by selecting suitable respective values from a fixed set of index values. Each of the specified index values causes the corresponding digital signal processor to use a respective predefined pair of encoding or decoding settings that includes a respective predefined constellation and a respective predefined shaping code. In some embodiments, the used shaping codes are configured to operate as block codes, with the block sizes being selected such that a multi-code frame generated using multiple shaping codes can be matched to exactly one DMT symbol or to a desired number of whole DMT symbols.

An FDM communication system in which encoding/decoding settings for different sets of tones are specified using index values assigned to different sets of tones by selecting suitable respective values from a fixed set of index values. Each of the specified index values causes the corresponding digital signal processor to use a respective predefined pair of encoding or decoding settings that includes a respective predefined constellation and a respective predefined shaping code. In some embodiments, the used shaping codes are configured to operate as block codes, with the block sizes being selected such that a multi-code frame generated using multiple shaping codes can be matched to exactly one DMT symbol or to a desired number of whole DMT symbols.

Example embodiments describe means (200) for performing i) pre-compensating (210, N sets of K.sub.1 tone data values (220) for crosstalk between N communication lines; the N sets of K.sub.1 tone data values pertaining to respective N terminal nodes of a digital communication system; ii) calculating (215) from the pre-compensated N sets of K.sub.1 tone data values (221) N sets of first time domain symbols (225); iii) calculating (283) a second time domain symbol (284) from a set of K.sub.2 tones values (280); the K.sub.2 tone data values pertaining to a selected one of the N terminal nodes; and iv) adding (212) the second time domain symbol in a weighted manner to the first time domain symbols such that the second time domain symbol is added to the first time domain symbol for the selected terminal node and to at least one other of the first time domain symbols for the respective other terminal nodes.

Example embodiments describe means (200) for performing i) pre-compensating (210, N sets of K.sub.1 tone data values (220) for crosstalk between N communication lines; the N sets of K.sub.1 tone data values pertaining to respective N terminal nodes of a digital communication system; ii) calculating (215) from the pre-compensated N sets of K.sub.1 tone data values (221) N sets of first time domain symbols (225); iii) calculating (283) a second time domain symbol (284) from a set of K.sub.2 tones values (280); the K.sub.2 tone data values pertaining to a selected one of the N terminal nodes; and iv) adding (212) the second time domain symbol in a weighted manner to the first time domain symbols such that the second time domain symbol is added to the first time domain symbol for the selected terminal node and to at least one other of the first time domain symbols for the respective other terminal nodes.