Methods for canceling interfering wireless signals in cable customer premises equipment devices and outside plant

A noise reduction device for use with a cable signal distributed by an outside plant of a cable system. The device includes an antenna and a signal processing system. The outside plant receives an interfering radio frequency (“RF”) signal generated by one or more external wireless signal sources and combines the interfering RF signal with the cable signal to produce a noisy cable signal. The antenna receives the interfering RF signal as a copy signal. The signal processing system modifies the copy signal to produce a processed copy signal, and combines the noisy cable signal and the processed copy signal to produce a combined signal. The signal processing system also monitors error rate values of the combined signal, and adjusts the copy signal such that the copy signal at least partially cancels the interfering RF signal in the combined signal thereby reducing the error rate values of the combined signal.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed generally to systems and methods for reducing or eliminating effects of interfering radio frequency signals on cable customer premises equipment devices and outside plant.

2. Description of the Related Art

It has been reported that cable customer premises equipment (“CPE”) devices, such as cable set-top-boxes, cable modems, and embedded multimedia terminal adapters (“EMTAs”), are experiencing problems functioning properly in the presence of wireless telephones because wireless telephones introduce interfering radio frequency (“RF”) signals into the CPE devices. While many CPE devices include shielding that helps reduce such interfering wireless signals inside the CPE devices, the amplitudes of some strong wireless signals (e.g., RF signals used by wireless Long Term Evolution (“LTE”) cellular telephones) are large enough to cause signal-processing problems in the CPE devices. Further, retail grade cable and RF splitters used by some people in their homes can be highly susceptible to RF interference. Thus, cable and RF splitters may receive interfering signals and function as a point of ingress into CPE devices for interfering signals.

Currently available methods of dealing with problems caused by interfering RF signals involve either abandoning the use of some frequencies (e.g., those experiencing significant RF interference) by a cable system, and/or increasing the shielding of the CPE devices. Abandoning the use of some frequencies is undesirable because doing so reduces data bandwidth and the number of video channels available to customers. Unfortunately, increasing the shielding of the CPE devices simply does not provide enough isolation from the interfering RF signal in some cases.

A similar problem occurs in the outside plant portion of a cable television distribution systems. In recent years, the Federal Communications Commission has been allocating larger and larger portions of frequency spectrum used by cable television distribution systems to wireless service providers. Thus, wireless transmissions originating from such wireless service providers may interfere with cable signals distributed by the outside plant. Additionally, interfering signals (e.g., signals broadcast on the same frequency or frequencies used by cable television distribution systems) originating from other transmitting devices (such as broadcast television stations) may introduce noise into cable signals. While the various components of the outside plant may include shielding, some interfering signals may nevertheless be received by the outside plant and may introduce noise into the cable signals distributed by the outside plant. In some cases, it is not practical to increase the shielding to eliminate the interference.

Therefore, a need exists for methods of reducing and/or eliminating interfering signals in the outside plant and/or CPE devices. Noise reduction devices and/or CPE devices configured to operate in the presence of strong wireless signals would be particulary desirable. The present application provides these and other advantages as will be apparent from the following detailed description and accompanying figures.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1is a block diagram of a system100including an exemplary customer premises equipment (“CPE”) device110connected to an exemplary cable system120. WhileFIG. 1illustrates the single CPE device110, those of ordinary skill in the art appreciate that a plurality of CPE devices like the CPE device110may be connected to the cable system120. The cable system120may include any conventional cable system configured to transmit a cable signal (illustrated by the arrow112) to the CPE device110. The CPE device110may include or be connected to a recipient device130. The CPE device110receives the cable signal (illustrated as arrow112) from the cable system120, processes the cable signal to produce a processed signal (illustrated as arrow114), and provides the processed signal to the recipient device130. The recipient device130may be a display device configured to generate a display viewable by a user (not shown) based at least in part on the processed signal (illustrated as the arrow114). By way of a non-limiting example, the recipient device130may be implemented as a television set, a computing device (e.g., a personal computer), and the like. As is apparent to those of ordinary skill in the art, the CPE device110and the recipient device130may be combined into a single device (not shown).

One or more external wireless signal sources (e.g., a cellular telephone140, a cellular telephone141, and the like) may generate wireless or RF signals (e.g., RF signals142). Non-limiting examples of external wireless signal sources include cellular telephones and the like. By way of a non-limiting example, the cellular telephone140may be configured to communicate using the Long Term Evolution (“LTE”) standard, and the RF signals142may be LTE signals.

The CPE device110may receive the RF signals (e.g., the RF signals142) generated by the one or more wireless signal sources (e.g., the cellular telephone140, the cellular telephone141, and the like) as an interfering signal (illustrated as arrow254) that combines with the cable signal (illustrated as arrow112). This combination may negatively affect the quality of the processed signal (illustrated as arrow114) provided to the recipient device130. The interfering signal (illustrated as arrow254) may be received by the CPE device110and/or components connected to the CPE device110(such as RF splitters, cables, and the like) that transmit the interfering signal or a portion thereof to the CPE device110. For ease of illustration, the interfering signal (illustrated as arrow254) will be described as being received by the CPE device110.

By way of a non-limiting example, the CPE device110may be implemented as a cable set-top-box, a television set, a cable modem, an EMTA, a computing device (e.g., a personal computer), and the like. The CPE device110includes a processor205, memory207, a first RF tuner210, a fixed phase delay215, a RF combiner220, an antenna225, a second RF tuner230, and a signal adjustment block234.

Referring toFIG. 4, by way of a non-limiting example, the signal adjustment block234may include a phase adjustment235, and an amplitude adjustment240. In such embodiments, the signal adjustment block234is configured to adjust both phase and amplitude (or gain) of a signal. By way of another non-limiting example, referring toFIG. 1, the signal adjustment block234may be configured to enable multiple delay taps. Such implementations may be useful for canceling noise when the interfering signal (illustrated as arrow254) is received along multiple paths or when channel distortions are present (e.g., in the cable signal illustrated as arrow112).

The first RF tuner210, the fixed phase delay215, the RF combiner220, the second RF tuner230, the phase adjustment235, the amplitude adjustment240, the processor205, and the memory207may be characterized as being signal processing components. The first RF tuner210, and the signal adjustment block234may be characterized as being signal adjustment components.

The first RF tuner210determines the frequency or frequencies on which the CPE device110receives the cable signal (illustrated as arrow112) from the cable system120. The first RF tuner210supplies the received cable signal to the fixed phase delay215as an RF signal (illustrated as arrow242). The fixed phase delay215delays the RF signal (illustrated as arrow242) by a fixed amount, and outputs a phase delayed signal (illustrated as arrow244) to the RF combiner220. For ease of illustration, the phase delayed signal (illustrated as arrow244) will be referred to as a processed cable signal. As will be described in detail below, the RF combiner220outputs a combined signal (illustrated as arrow246) to the processor205.

Together the first RF tuner210, the fixed phase delay215, and the RF combiner220may be characterized as being a signal processing chain250. Unfortunately, the processing chain250also receives the interfering signal (illustrated as arrow254). Thus, the combined signal (illustrated as arrow246) includes the processed cable signal (illustrated as arrow244), and the interfering signal (illustrated as arrow254) received by the processing chain250.

The antenna225is configured to receive the RF signals (e.g., the RF signals142) generated by the one or more interfering wireless signal sources (e.g., the cellular telephone140, the cellular telephone141, and the like). Thus, the antenna225receives a copy of the same RF signals that are received by (and interfere with) the processing chain250. For ease of illustration, the signal(s) received by the antenna225will be referred to as a “copy signal” (illustrated as arrow258). As is apparent to those of ordinary skill in the art, the copy signal has a plurality of signal parameters, such as an amplitude value, an amount of phase shift, an amount of attenuation, and the like.

The antenna225supplies the copy signal (illustrated as arrow258) to the second RF tuner230. The second RF tuner230determines the frequency or frequencies on which the CPE device110receives the copy signal (illustrated as arrow258), and supplies the received copy signal to the signal adjustment block234as an RF signal (illustrated as arrow260). The signal adjustment block234adjusts the RF signal (illustrated as arrow260), and outputs a processed copy signal (illustrated as arrow264) to the RF combiner220.

Referring toFIG. 4, in embodiments in which the signal adjustment block234includes the phase adjustment235, and the amplitude adjustment240, the phase adjustment235adjusts the phase of the RF signal (illustrated as arrow260), and outputs a phase adjusted signal (illustrated as arrow262) to the amplitude adjustment240. The amplitude adjustment240adjusts the amplitude of the phase adjusted signal (illustrated as arrow262), and outputs a phase and amplitude adjusted signal as the processed copy signal (illustrated as arrow264) to the RF combiner220(seeFIG. 1).

Returning toFIG. 1, the RF combiner220combines the processed copy signal (illustrated as arrow264) with the processed cable signal (illustrated as arrow244) and, if present, the interfering signal (illustrated as arrow254) received by the processing chain250. Thus, the combined signal (illustrated as arrow246) may have three components: (1) the processed cable signal (illustrated as arrow244); (2) the processed copy signal (illustrated as arrow264); and (3) the interfering signal (illustrated as arrow254).

The processor205receives the combined signal (illustrated as arrow246) from the RF combiner220, and adjusts the processed copy signal (illustrated as arrow264) to at least partially cancel out the interfering signal (illustrated as arrow254). The processor205may be implemented by a microprocessor, microcontroller, application-specific integrated circuit (“ASIC”), digital signal processor (“DSP”), or the like. The processor205may be integrated into an electrical circuit, such as a conventional circuit board, that supplies power to the processor205. The processor205may include internal memory and/or the memory207may be coupled thereto. The present invention is not limited by the specific hardware component(s) used to implement the processor205and/or the memory207.

The memory207is a computer readable medium that includes instructions or computer executable components that are executed by the processor205. The memory207may be implemented using transitory and/or non-transitory memory components. The memory207may be coupled to the processor205by an internal bus209.

The memory207may comprise random access memory (“RAM”) and read-only memory (“ROM”). The memory207contains instructions and data that control the operation of the processor205. The memory207may also include a basic input/output system (“BIOS”), which contains the basic routines that help transfer information between elements within the CPE device110.

Optionally, the memory207may include internal and/or external memory devices such as hard disk drives, floppy disk drives, and optical storage devices (e.g., CD-ROM, R/W CD-ROM, DVD, and the like). The CPE device110may also include one or more I/O interfaces (not shown) such as a serial interface (e.g., RS-232, RS-432, and the like), an IEEE-488 interface, a universal serial bus (“USB”) interface, a parallel interface, and the like, for the communication with removable memory devices such as flash memory drives, external floppy disk drives, and the like.

In the embodiment illustrated, the processor205implements a demodulator270, and an error monitoring and control block272. While the demodulator270, and the error monitoring and control block272have been illustrated as separate functional blocks, in alternate embodiments, the demodulator270, and the error monitoring and control block272may be combined into a single functional block. Further, the functionality attributed to the demodulator270, and the error monitoring and control block272may be divided into any suitable number of separate functional blocks.

The processor205is configured to execute software implementing the demodulator270, and the error monitoring and control block272. Such software may be implemented by computer executable instructions stored in memory207. For example, the memory207may store instructions executable by the processor205that when executed cause the CPE device110to perform a method300(seeFIG. 2), a method330(seeFIG. 3), and/or a method400(seeFIG. 5) described below.

The demodulator270receives the combined signal (illustrated as arrow246), and demodulates the combined signal to produce a data stream (not shown). The processor205may process the data stream to produce the processed signal (illustrated as arrow114), which is transmitted by the processor205to the recipient device130. The processed signal (illustrated as arrow114) may include audio and video signals that are displayable by the recipient device130. The demodulator270may be configured to perform forward error correction on the combined signal (illustrated as arrow246). In such embodiments, the demodulator270may occasionally (e.g., periodically) calculate an error rate value, and transmit the error rate value to the error monitoring and control block272. Thus, a series of error rate values (illustrated as arrow282) may be received by the error monitoring and control block272as an error rate signal. While the demodulator270is described as implementing forward error correction, this is not a requirement. Alternatively, forward error correction processing may be implemented in a separate functional block in the CPE device110. By way of another non-limiting example, the error monitoring and control block272may determine the error rate values of the combined signal (illustrated as arrow246).

The error monitoring and control block272monitors the error rate values of the combined signal (illustrated as arrow246), and determines whether to modify the processed copy signal (illustrated as arrow264) in a manner that at least partially cancels the interfering signal (illustrated as arrow254) present in the combined signal to thereby reduce the error rate values of the combined signal. The error monitoring and control block272may modify the processed copy signal (illustrated as arrow264) by instructing the signal adjustment block234to modify one or more signal parameters of the RF signal (illustrated as arrow260). Together, the error monitoring and control block272and the signal adjustment block234may implement one or more adaptive filters. Examples of adaptive filters that may be implemented include filters configured to reduce or eliminate noise by adjusting phase, adjusting amplitude, implementing multiple delay taps, combinations thereof, and the like.

For example, referring toFIG. 4, the error monitoring and control block272may modify the processed copy signal (illustrated as arrow264) by instructing the phase adjustment235to modify the amount of phase shift applied to the RF signal (illustrated as arrow260), and/or instructing the amplitude adjustment240to modify the amount of amplitude adjustment applied to the phase adjusted signal (illustrated as arrow262).

Returning toFIG. 1, the first RF tuner210, the fixed phase delay215, the RF combiner220, the second RF tuner230, the signal adjustment block234, the demodulator270, and the error monitoring and control block272are functional blocks. The functions of each of these functional blocks may be implemented in a number of different ways, such as in hardware and/or in software. Further, as is appreciated by those of ordinary skill in the art, the functions attributed to these functional blocks may be combined into one or more functional blocks, and/or distributed differently in any number of functional blocks.

FIG. 2is a flow diagram of the method300of modifying the processed copy signal (illustrated as arrow264) to at least partially cancel the interfering signal (illustrated as arrow254) in the combined signal (illustrated as arrow246). The method300may be performed by the processor205. For ease of illustration, the method300may be described as being performed by the error monitoring and control block272.

In first block310, the error monitoring and control block272monitors the error rate values (illustrated as arrow282) received from the demodulator270until an increase in the error rate values is detected. By way of a non-limiting example, the error monitoring and control block272may detect an increase has occurred when the error rate values exceeds a threshold amount.

In next block315, the error monitoring and control block272measures signal energy of the copy signal (illustrated as arrow258). By way of a non-limiting example, the second RF tuner230may measure the signal energy and provide it to the error monitoring and control block272.

In decision block320, the error monitoring and control block272determines whether the signal energy is large enough to be causing the increase in the error rate values. The decision in decision block320is “NO” when the error monitoring and control block272determines the signal energy is not large enough. In other words, when the decision is “NO,” the increase in the error rate values is being caused by factors other than local noise ingress. On the other hand, the decision in decision block320is “YES” when the error monitoring and control block272determines the signal energy is large enough to be causing to be causing the increase in the error rate values.

By way of a non-limiting example, the decision in decision block320may be “YES,” when the signal energy exceeds a predetermined threshold value. If the signal energy does not exceed the predetermined threshold value, decision in decision block320may be “NO.”

When the decision in decision block320is “NO,” the error monitoring and control block272returns to block310to continue monitoring the error rate values.

When the decision in decision block320is “YES,” the error monitoring and control block272advances to block325to begin a noise cancellation process327portion of the method300. In block325, the error monitoring and control block272sets the adjustable attenuation of the copy signal (illustrated as arrow258). By way of a non-limiting example, the signal adjustment block234may be configured to attenuate the copy signal (illustrated as arrow258) in response to an instruction from the error monitoring and control block272. In such embodiments, the error monitoring and control block272instructs the signal adjustment block234to set the amount of attenuation of the copy signal (illustrated as arrow258) such that the signal energy of the copy signal is approximately equal to the average signal energy of the interfering signal (illustrated as arrow254) received by the CPE device110at the operating frequency. In embodiments in which the signal adjustment block234includes the amplitude adjustment240(seeFIG. 4), the amplitude adjustment240may attenuate the copy signal.

In block326, the error monitoring and control block272evaluates a plurality of signal adjustment options and selects one or more signal adjustments. Then, in block328, the error monitoring and control block272instructs the signal adjustment block234to apply the selected signal adjustment(s) to the RF Signal (illustrated as arrow260).

At this point, the processed copy signal (illustrated as arrow264) and the interfering signal (illustrated as arrow254) components of the combined signal (illustrated as arrow246) are substantially canceling one another. To continue monitoring the combined signal, the error monitoring and control block272returns to block310. If at any point during the noise cancellation process327portion of the method300, the signal energy of the copy signal (illustrated as arrow258) goes to zero (or falls below a predefined threshold value), the error monitoring and control block272may return to block310.

By performing the method300, the error monitoring and control block272continuously monitors the combined signal (illustrated as arrow246), and when appropriate, adjusts the copy signal in a feedback loop based on the error rate values of the combined signal.

FIG. 3is a flow diagram of a method330that may be performed in block326of the method300. The method330may be performed by the processor205. For ease of illustration, the method330may be described as being performed by the error monitoring and control block272.

In first block332, the error monitoring and control block272records the error rate value (e.g., in the memory207) received after the amount of attenuation of the copy signal is set in block325of the method300.

In decision block335, the error monitoring and control block272determines whether all available signal adjustment options have been evaluated. The decision in decision block335is “NO” when the error monitoring and control block272determines at least one available signal adjustment option has not been evaluated. On the other hand, the decision in decision block335is “YES” when the error monitoring and control block272determines all available signal adjustment options have been evaluated.

When the decision in decision block335is “NO,” in block340, the error monitoring and control block272instructs the signal adjustment block234to modify the RF signal (illustrated as arrow260) in accordance with a previously unevaluated signal adjustment option. Then, the error monitoring and control block272returns to block332, and records the error rate value (e.g., in the memory207) received after the RF signal was adjusted in block340.

When the decision in decision block335is “YES,” in block345, the error monitoring and control block272selects the signal adjustment option that produced the lowest error rate value recorded (in block332). Then, the method330terminates.

FIG. 5is a flow diagram of a method400that may be performed in block326of the method300when (as inFIG. 4) the signal adjustment block234includes the phase adjustment235and the amplitude adjustment240. The method400may be performed by the processor205. For ease of illustration, the method400will be described as being performed by the error monitoring and control block272.

In block430, the error monitoring and control block272records the error rate value (e.g., in the memory207) received after the amount of attenuation of the copy signal is set in block325of the method300illustrated inFIG. 2.

Referring toFIG. 5, in decision block435, the error monitoring and control block272determines whether all available phase values have been evaluated. The decision in decision block435is “NO” when the error monitoring and control block272determines at least one available phase value has not been evaluated. On the other hand, the decision in decision block435is “YES” when the error monitoring and control block272determines all available phase values have been evaluated.

When the decision in decision block435is “NO,” in block440, the error monitoring and control block272instructs the phase adjustment235to modify the amount of phase shift applied to the RF signal (illustrated as arrow260). Then, the error monitoring and control block272returns to block430, and records the error rate value (e.g., in the memory207) received after the amount of phase shift was adjusted in block440.

When the decision in decision block435is “YES,” in block445, the error monitoring and control block272selects the amount of phase shift that produced the lowest error rate value recorded (in block430). Then, the error monitoring and control block272instructs the phase adjustment235to apply the selected amount of phase shift to the RF Signal (illustrated as arrow260).

The process performed by blocks430-445tries to adjust the processed copy signal (illustrated as arrow264) such that the processed copy signal is approximately 180 degrees out of phase with the interfering signal (illustrated as arrow254). In other words, blocks430-445try to adjust the phase of the processed copy signal so that it at least partially cancels out the interfering signal in the combined signal (illustrated as arrow246).

By way of a non-limiting example, the amount of phase shift applied to the RF signal (illustrated as arrow260) may be set to an initial phase shift amount. Then, in block440, the initial phase shift amount may be increased (or decreased) by an incremental amount. Blocks430-440repeat until a final phase shift amount is reached. Then, in block445, the error monitoring and control block272selects the phase shift amount that provided the lowest error rate value.

To improve the amount of cancelation, the amplitude of the processed copy signal and the amplitude of the interfering signal should match (or be substantially similar). This is achieved by blocks450-465of the method400.

In decision block450, the error monitoring and control block272determines whether all available amplitude values have been evaluated. The decision in decision block450is “NO” when the error monitoring and control block272determines at least one available amplitude value has not been evaluated. On the other hand, the decision in decision block450is “YES” when the error monitoring and control block272determines all available amplitude values have been evaluated.

When the decision in decision block450is “NO,” in block455, the error monitoring and control block272instructs the amplitude adjustment240to modify the amplitude value applied to the to the phase adjusted signal (illustrated as arrow262). Then, the error monitoring and control block272advances to block460, and records the error rate value (e.g., in the memory207) received after the amplitude value was adjusted in block455.

When the decision in decision block450is “YES,” in block465, the error monitoring and control block272selects the amplitude value that produced the lowest error rate value recorded (in block460). Then, the method400terminates.

By way of a non-limiting example, after block445, the amplitude value may be set to an initial amplitude value. Then, in block455, the initial amplitude value may be increased (or decreased) by an incremental amount. Blocks450-460repeat until a final amplitude value is reached. Then, in block465, the amplitude value that is closest to the amplitude value of the interfering signal may be selected by selecting the amplitude value that provided the lowest error rate value.

After the method400has terminated, in block328of the method300illustrated inFIG. 2, the error monitoring and control block272instructs the phase adjustment235to apply the amount of phase shift selected in block445to the RF Signal (illustrated as arrow260), and instructs the amplitude adjustment240to apply the amplitude value selected in block465to the phase adjusted signal (illustrated as arrow262).

By performing the method400in block326of the method300illustrated inFIG. 2, the error monitoring and control block272continuously monitors the combined signal, and when appropriate, adjusts the amplitude value and/or the amount of phase shift of the copy signal in a feedback loop based on the error rate values of the combined signal (illustrated as arrow246).

By using the CPE device110, cable companies may continue effectively using RF spectrum in their cable systems that coincides with licensed wireless spectrum. Use of this spectrum by the cable companies may be critical to business models that include providing a desired amount of data bandwidth and/or a desired number of video channels to customers.

Referring toFIG. 6, the exemplary cable system120may be characterized as including a headend610and an outside plant620. The headend610receives signals (e.g., television signals), and processes them for distribution over the outside plant620. InFIG. 6, an exemplary cable signal delivered to the outside plant620by the headend610is illustrated by arrow612. For ease of illustration, the cable signal illustrated by arrow612will be referred to as an “original cable signal.”

The outside plant620delivers cable signals (illustrated by arrows622) to a plurality of CPE devices630. The CPE device110illustrated inFIG. 1may be used to implement one or more of the CPE devices630. For ease of illustration, the cable signals illustrated by arrows622will be referred to as “delivered cable signals.” The delivered cable signals may include the cable signal illustrated by the arrow112inFIG. 1.

The outside plant620includes hardware components, such as cables, optical nodes, RF amplifiers, signal splitters, RF taps, other electrical components, and the like. While the various components of the outside plant620may include shielding (not shown), some interfering signals may nevertheless be received by the outside plant620. Thus, like the CPE device110(seeFIG. 1), one or more components of the outside plant620may receive interfering signals640from one or more external wireless signal sources (e.g., radio towers642-646).

Non-limiting examples of external wireless signal sources that may interfere with the outside plant620include broadcast television stations, cellular phone systems, other transmitting devices, combinations thereof, and the like. Some of these external wireless signal sources transmit RF signals at the same frequency or frequencies used by the outside plant620. While inFIG. 6, the exemplary external wireless signal sources have been illustrated as the radio towers642-646, the outside plant620may receive interfering signals from other sources of interference (e.g., the cellular telephone140and the cellular telephone141illustrated inFIG. 1).

For ease of illustration, inFIG. 6, the outside plant620is illustrated receiving an interfering signal (illustrated as arrow650) from the radio tower644. However, as is appreciated by those of ordinary skill in the art, the outside plant620may receive multiple interfering signals. Further, as is also apparent to those of ordinary skill in the art, the outside plant620may be large and encompass many square miles. Therefore, different portions of the outside plant620may receive different interfering signals.

Inside the outside plant620, the interfering signal (illustrated as arrow650) combines with the original cable signal (illustrated by arrow612) received by the outside plant620. Thus, the delivered cable signals (illustrated by arrows622) include both the interfering signal and the original cable signal. This combination may negatively affect the quality of the delivered cable signals.

As mentioned above, different portions of the outside plant620may receive different interfering signals.FIG. 7depicts a non-limiting example of a portion700of the outside plant620. The portion700includes a first cable702that receives the original cable signal (illustrated by arrow612) from the headend610(directly or via one or more intervening components) and conducts a noisy cable signal (illustrated as arrow612N) to a noise reduction device710. The portion700also includes a second cable706that receives the delivered cable signals (illustrated as arrow622) from the noise reduction device710and conducts the delivered cable signals to one or more of the CPE devices630. For ease of illustration, the first cable702will be described as receiving the interfering signal (illustrated as arrow650) from the radio tower644. Thus, the noisy cable signal (illustrated as arrow612N) includes both the original cable signal (illustrated by arrow612) and the interfering signal (illustrated as arrow650).

An antenna720may be positioned to receive a copy of the interfering signal (illustrated as arrow650). For example, the antenna700may be positioned at or near a location in the outside plant620experiencing interference. In this example, the antenna720is positioned near the first cable702at a location whereat the antenna can receive wireless signals generated by the radio tower644. The signal received by the antenna720will be referred to as the copy signal (illustrated as arrow258). The antenna720may be connected to or a component of the noise reduction device710. The antenna720may be substantially identical to the antenna225(seeFIG. 1) of the CPE device110. The antenna720may be configured for outdoor use and/or configured to receive wireless signals of the type typically received by the outside plant620.

Like reference numerals have been used inFIGS. 1 and 7to identify like components of the CPE device110and the noise reduction device710, respectively. Like the CPE device110, the noise reduction device710includes the processor205, the memory207, the first RF tuner210, the fixed phase delay215, the RF combiner220, the second RF tuner230, and the signal adjustment block234.

The first RF tuner210determines the frequency or frequencies on which the noise reduction device710receives the noisy cable signal (illustrated as arrow612N). The first RF tuner210supplies the received cable signal to the fixed phase delay215as the RF signal (illustrated as arrow242). The fixed phase delay215delays the RF signal (illustrated as arrow242) by a fixed amount, and outputs the phase delayed signal (illustrated as arrow244) to the RF combiner220. For ease of illustration, the phase delayed signal (illustrated as arrow244) will be referred to as a processed cable signal. As will be described in detail below, the RF combiner220outputs the combined signal (illustrated as arrow246) to the processor205. The RF combiner220also outputs the same combined signal as the delivered cable signal (illustrated as arrow622) to the second cable706.

The antenna720supplies the copy signal (illustrated as arrow258) to the second RF tuner230. The second RF tuner230determines the frequency or frequencies on which the noise reduction device710receives the copy signal (illustrated as arrow258), and supplies the received copy signal to the signal adjustment block234as the RF signal (illustrated as arrow260). The signal adjustment block234adjusts the RF signal (illustrated as arrow260), and outputs the processed copy signal (illustrated as arrow264) to the RF combiner220. The RF combiner220combines the processed copy signal (illustrated as arrow264) with the processed cable signal (illustrated as arrow244) to produce the combined signal (illustrated as arrow246) that is supplied to the processor205, and supplies the same combined signal to the second cable706as the delivered cable signal (illustrated as arrow622).

The processor205receives the combined signal (illustrated as arrow246) from the RF combiner220, and adjusts the processed copy signal (illustrated as arrow264) to at least partially cancel out the interfering signal (illustrated as arrow650). The demodulator270demodulates the combined signal (illustrated as arrow246) to produce a data stream (not shown). The demodulator270may calculate the series of error rate values (illustrated as arrow282) and send them to the error monitoring and control block272as an error rate signal.

The error monitoring and control block272monitors the error rate values of the combined signal (illustrated as arrow246), and determines whether to modify the processed copy signal (illustrated as arrow264) in a manner that at least partially cancels the interfering signal (illustrated as arrow650) present in the combined signal to thereby reduce the error rate values of the combined signal. The error monitoring and control block272may modify the processed copy signal (illustrated as arrow264) in any manner described above with respect to modifying the processed copy signal illustrated as arrow264inFIG. 1.

For example, the error monitoring and control block272of the noise reduction device710may perform the method300illustrated inFIG. 2to continuously monitor the combined signal (illustrated as arrow246), and when appropriate, adjust the copy signal based on the error rate values of the combined signal. When the error monitoring and control block272of the noise reduction device710performs the method300, the processed copy signal (illustrated as arrow264) is modified to at least partially cancel the interfering signal illustrated as arrow650(instead of the interfering signal illustrated as arrow254inFIG. 1). In block325, the error monitoring and control block272may instruct the signal adjustment block234to set the amount of attenuation of the copy signal (illustrated as arrow258) such that the signal energy of the copy signal is approximately equal to the average signal energy of the interfering signal (illustrated as arrow650) received by the noise reduction device710at the operating frequency. Optionally, the method330illustrated inFIG. 3or the method400illustrated inFIG. 5may be performed in block326of the method300. If at any point during the noise cancellation process327portion of the method300, the signal energy of the copy signal (illustrated as arrow258) received by the antenna720goes to zero (or falls below a predefined threshold value), the error monitoring and control block272may return to block310.

Multiple noise reduction devices like the noise reduction device710may be coupled to portions of the outside plant620to reduce noise.

The noise reduction device710and/or the CPE device110may be used by cable television multi-service operators to enable them to continue to use frequency spectrum that is also occupied by wireless transmitters (e.g., the radio tower644). This allows cable television multi-service operators to provide revenue generating services on the impacted frequencies, and therefore may provide financial benefits for such operators.