Time domain ingress noise detection and cancellation

An apparatus, comprising a receiver configured to receive a primary signal that comprises a narrowband noise component and a broadband noise component, a processor coupled to the receiver and configured to determine, in a time domain, an estimate of the narrowband noise component in real-time, determine a cancelled output signal in real-time that comprises an estimate of the broadband noise component, and determine an estimate of a power level of the narrowband noise component in real-time.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

Not applicable.

REFERENCE TO A MICROFICHE APPENDIX

Not applicable.

BACKGROUND

In certain signal processing schemes or communications systems, for example, Data-Over-Cable Service Interface Specifications (DOCSIS) and Ethernet passive optical network (EPON) over Coaxial (EPoC), an upstream band-limited data signal is corrupted with narrowband ingress noise and broadband additive white Gaussian noise (AWGN). Without compensation for the narrowband ingress noise, processing of the data signal by a receiver in the communications systems is impaired. Therefore, effectively and efficiently compensating the corrupted data signal is desirable.

SUMMARY

In some embodiments, the disclosure includes an apparatus, comprising a receiver configured to receive a primary signal that comprises a narrowband noise component and a broadband noise component, a processor coupled to the receiver and configured to determine, in a time domain, an estimate of the narrowband noise component in real-time, determine a cancelled output signal in real-time that comprises an estimate of the broadband noise component, and determine an estimate of a power level of the narrowband noise component in real-time.

in some embodiments, the processor further comprises a decorrelating adaptive line enhancer (ALE) comprising a first delay module configured to determine a reference signal according to the primary signal and a first amount of delay, a decorrelating adaptive filter coupled to the first delay module and configured to determine the estimate of the narrowband noise component, and a first summation module coupled to the decorrelating adaptive filter and configured to subtract the estimate of the narrowband noise component from the primary signal to determine the cancelled output signal.

In some embodiments, the decorrelating adaptive filter comprises a second delay module configured to determine a delayed reference signal according to the reference signal and a second amount of delay, a first multiplication module configured to determine a first multiplication result according to a relationship between a first filter coefficient and the reference signal, a second multiplication module configured to determine a second multiplication result according to a relationship between a second filter coefficient and the delayed reference signal, and a second summation module configured to determine the estimate of the narrowband noise component according to a relationship between the first multiplication result and the second multiplication result.

In some embodiments, the decorrelating adaptive filter is further configured to determine the first filter coefficient according to a relationship between the cancelled output signal, the reference signal, and a first preceding filter coefficient, and determine the second filter coefficient according to a relationship between the cancelled output signal, the delayed reference signal, and a second preceding filter coefficient.

In some embodiments the processor further comprises a comparator configured to compare the estimate of the power level of the narrowband noise component with a threshold value to form a first comparison output signal when the estimate of the power level of the narrowband noise component is less than or equal to the threshold value, and compare the estimate of the power level of the narrowband noise component with the threshold value to form a second comparison output signal when the estimate of the power level of the narrowband noise component is greater than the threshold value, a third delay module configured to determine a delayed primary signal according to the primary signal and a third amount of delay, and a multiplexer configured to receive the delayed primary signal, the cancelled output signal, and the first comparison output signal or the second comparison output signal, output the delayed primary signal when the first comparison output signal indicates that the estimate of the power level of the narrowband noise component is less than or equal to the threshold value, and output the cancelled output signal when the second comparison output signal indicates that the estimate of the power level of the narrowband noise component is greater than the threshold value.

In some embodiments, the primary signal further comprises a data component, and wherein the cancelled output signal further comprises an estimate of the data component. In some embodiments, the processor is further configured to determine the estimate of the power level of the narrowband noise component with respect to the data component. In some embodiments, the apparatus is a cable modem termination system (CMTS) receiver. In some embodiments, the communications network comprises a DOCSIS. In some embodiments, the processor is further configured to operate in the time domain and not operate in a frequency domain.

In another embodiment, the disclosure includes a method, comprising receiving, by a network element operating in real-time in a time domain, a data signal from an upstream source, determining in the time domain and by the network element operating in real-time, a reference signal according to the received signal, determining in the time domain and by the network element operating in real-time, an error signal according to the received signal, and determining in the time domain and by the network element operating in real-time, an estimate of a narrowband noise of the reference signal.

In some embodiments, the received signal comprises a datum, a broadband noise, and the narrowband noise. In some embodiments, the error signal comprises an estimate of the datum corrupted with the broadband noise. In some embodiments, the reference signal comprises the received signal delayed by a predetermined amount of delay. In some embodiments, the estimate of the narrowband noise is determined according to a relationship between the error signal and the reference signal.

In yet another embodiment, the disclosure includes a network element comprising a receiver configured to receive a signal from an upstream source, and a processor coupled to the receiver and configured to determine, in a time domain and operating in real-time, an estimate of a narrowband noise of the signal, and determine, in the time domain and operating in real-time, an estimate of a power level of the narrowband noise.

In some embodiments, the processor is further configured to manage the received signal according to the estimate of the power level of the narrowband noise. In some embodiments, managing the received signal comprises transmitting a desired signal parameter to the upstream source. In some embodiments, the estimate of the power level of the narrowband noise is greater than or equal to about −30 decibels relative to a power level of the signal. In some embodiments, the processor determines the estimate of the power level of the narrowband noise according to a relationship between an average of the estimate of the narrowband noise and an average of the signal.

DETAILED DESCRIPTION

Some hybrid access networks combine optical networks with coaxial (coax) networks. Ethernet over Coax (EoC) is a generic name used to describe all technologies that transmit Ethernet frames over a coaxial network. Examples of EoC technologies may include EPoC, DOCSIS, Multimedia over Coax Alliance (MoCA), G.hn (a common name for a home network technology family of standards developed under the International Telecommunication Union (ITU) and promoted by the HomeGrid Forum), home phoneline networking alliance (HPNA), and home plug audio/visual (A/V). EoC technologies have been adapted to run outdoor coax access from an Optical Network Unit (ONU) to an EoC head end with connected Customer Premises Equipment (CPEs) located in subscriber homes. In a coaxial network, physical layer transmission may employ orthogonal frequency-division multiplexing (OFDM) to encode digital data onto multiple carrier frequencies. Some advantages of OFDM transmission include high spectral efficiency and robust transmission (e.g., attenuation at high frequencies in long coaxial wires, narrow band interferers, frequency selective noise, etc.). A DOCSIS network may operate over a Hybrid Fiber Coax (HFC) network. The DOCSIS network may comprise a CMTS positioned in a local exchange or central office where the CMTS connects the HFC network to a backbone network. The CMTS may serve a plurality of cable moderns (CMs) positioned at end-user locations.

Disclosed herein are embodiments that provide for real-time determination and cancellation of narrowband, or ingress, noise in a received signal that includes narrowband noise, broadband noise, and data in a time domain. The narrowband noise is determined and cancelled in the presence of the data and without scheduling a quiet-time in a transmission during which data is not transmitted. To determine the narrowband noise, the disclosed embodiments decorrelate an oversampled signal according to a decorrelating adaptive filter of an ALE and process the signal further according to the ALE. Embodiments of the present disclosure further provide for real-time determination of narrowband noise power in the time domain for narrowband noise power levels greater than, or equal to, −20 dBc. Real-time determination of the determination and cancellation of the narrowband noise and determination of narrowband noise power is achieved in real-time by performing the determination and cancellations solely in the time-domain. Embodiments of the present disclosure further provide for a selectable narrowband noise cancellation unit that enables selective cancellation of narrowband noise in the signal according to a determination based on a comparison of the narrowband noise power and a threshold value.

FIG. 1is a schematic diagram of an embodiment of a DOCSIS network100. The DOCSIS network100comprises a DOCSIS 3.0 network as specified in DOCSIS CM-SP-PHYv3.0-112-150305 and CM-SP-MULPIv3.0-128-150827, which are incorporated herein by reference as if reproduced in their entirety. Alternatively, the DOCSIS network100comprises a DOCSIS 3.1 network as specified in DOCSIS 3.1 documents CM-SP-PHYv3.1-107-150910 and CM-SP-MULPIv3.1-107-150910, which are incorporated herein by reference as if reproduced in their entirety. The network100comprises a CMTS110, at least one HFC node130, and any number of CMs150and/or set-top boxes (STBs)152. The RFC node130is coupled to the CMTS110via an optical fiber114, and the CMs150and/or the STBs152are coupled to the HFC node130via electrical cables134, one or more amplifiers (e.g., amplifiers136and138), and at least one splitter140.

The CMTS110is any device configured to communicate with the CMs150via the HFC node130. The CMTS110acts as an intermediary between the CMs150and another network for example, a backbone network such as the Internet. The CMTS110forwards data received from the backbone network to the CMs150and forwards data received from the CMs150onto the backbone network. The CMTS110comprises an optical transmitter and an optical receiver transmitting and/or receiving messages from the CMs150via the optical fiber114. The CMTS110further comprises transmitters and/or receivers for communicating with the backbone network. Alternatively, the CMTS110comprises a transceiver that incorporates and performs the functions of both and optical transmitter and an optical receiver. When the backbone network employs a network protocol that is different from the protocol used in the network100, the CMTS110comprises a converter that converts the backbone network protocol into the protocol of the network100. The CMTS110converter also converts the network100protocol into the backbone network protocol. The CMTS110is further configured to schedule upstream and downstream transmissions across the network100, so that transmissions between the CMTS110and the CMs150are separated in the time and/or frequency domain, which allows the transmissions to be separated at an associated destination. An allocation of time and/or frequency resources is transmitted to the CMs150via an Uplink Media Access Plan (UL-MAP) messages and/or Downlink Media Access Plan (DL-MAP) messages.

The CMs150and the STBs152are any devices that are configured to communicate with the CMTS110and any subscriber devices in a local network. The CMs150and the STBs152act as intermediaries between the CMTS110and such subscriber devices. The CMs150and the STBs152may be similar devices, but may be employed to couple to different subscriber devices in some embodiments. For example, an SIB152may be configured to interface with a television, while a CM150may be configured to interface with any local network device with an Internet Protocol (IP) and/or Media Access Control (MAC) address, such as a local computer, a wired and/or wireless router, or local content server, a television, etc. The CMs150forward data received from the CMTS110to the subscriber devices, and forward data received from subscriber devices toward the CMTS110. Although the specific configuration of the CMs150may vary depending on the type of the network100, in an embodiment, the CMs150comprise an electrical transmitter configured to send electrical signals to the CMTS110via the HFC node130and an electrical receiver configured to receive electrical signals from the CMTS110via the HFC node130. Additionally, the CMs150comprise converters that convert the network100electrical signals into electrical signals for subscriber devices, such as signals in Institute of Electrical and Electronics Engineers (IEEE) 802.11 wireless local area network (WiFi) protocol. The CMs150further comprise a second transmitter and/or receiver that send and/or receive the converted electrical signals to the subscriber devices. In some embodiments, the CMs150and Coaxial Network Terminals (CNTs) are similar, and thus the terms are used interchangeably herein. The CMs150are typically located at distributed locations, such as the customer premises, but may be located at other locations as well. The CMs150transmit a configurable number of OFDM frames upstream toward the CMTS110via the HFC node130as part of a transmission burst. An OFDM frame is a communication burst of a specified duration comprising a signal with a plurality of frequency based subcarriers. An OFDM frame comprises a configurable number of OFDM symbols with smaller durations than the OFDM frame.

The HFC node130is positioned at the intersection of an Optical Distribution Network (ODN)115comprising the optical fiber114and an Electrical Distribution Network (EDN)135. HFC node130may include electro-optical signal translation capabilities (e.g., Open Systems Interconnection (OSI) model layer1capabilities). The MFC node130may not be configured to perform routing, buffering, or other higher layer functions (e.g., OSI model layer2-7). Accordingly, the HFC node130translates optical signals received from the optical fiber114into electrical signals and forwards the electrical signals toward the CMs150and the STBs152, and vice-versa. It should be noted that that the HFC node130may be remotely coupled to the CMTS110or reside in the CMTS110. In some embodiments, the CMTS110is equipped with part or all of the functionalities of the HFC node130.

The ODN115is a data distribution system that comprises the optical fiber114cables, couplers, splitters, distributors, and/or other equipment. In an embodiment, the optical fiber114cables, couplers, splitters, distributors, and/or other equipment are passive optical components. The optical fiber114cables, couplers, splitters, distributors, and/or other equipment are components that do not require any power to distribute data signals between the CMTS110and the HFC node130. It should be noted that the optical fiber114cables may be replaced by any optical transmission media. In some embodiments, the ODN115comprises one or more optical amplifiers. In some embodiments, data distributed across the ODN115are combined with cable television (CATV) services using multiplexing schemes. The ODN115extends from the CMTS110to the HFC node130as shown inFIG. 1, but may be alternatively configured as determined by a person of ordinary skill in the art. Signals transmitted across the ODN115may be transmitted as analog signals and/or as digital signals.

The EDN135is a data distribution system that comprises electrical cables (e.g., coaxial cables, twisted wires, etc.), couplers, splitters, distributors, and/or other equipment. In an embodiment, the electrical cables, couplers, splitters, distributors, and/or other equipment are passive electrical components. The electrical cables, couplers, splitters, distributors, and/or other equipment are components that do not require any power to distribute data signals between the HIV node130and the CMs150. It should be noted that the electrical cables may be replaced by any electrical transmission media in some embodiments. In some embodiments, the EDN135comprises one or more electrical amplifiers. The EDN135extends from the HFC node130and the CMs150in a branching configuration as shown inFIG. 1, but may be alternatively configured as determined by a person of ordinary skill in the art.

A data transmission received by the CMTS110from a CM150can include broadband noise and narrowband noise in addition to intended data. The broadband noise and the narrowband noise, if left uncompensated for, for example if not cancelled, can inhibit processing of the data transmission. To cancel one or both of the broadband noise and the narrowband noise, the CMTS110implements noise cancellation and power estimation according to various embodiments of the present disclosure.

FIG. 2is a schematic diagram of an embodiment of a network element for operating in an optical communications network. For example, the network element200is the CMTS110in the DOCSIS network100in one example embodiment. At least some of the features/methods described in this disclosure are implemented in the network element200. For instance, the features/methods of this disclosure are implemented using hardware, firmware, and/or software installed to run on hardware. The network element200is a device (e.g., an access point, an access point station, a router, a switch, a gateway, a bridge, a server, a client, a user-equipment, a mobile communications device, etc.) that transports data through a network, system, and/or domain and/or any device that provides services to other devices in a network or performs computational functions. Moreover, the terms “network element,” “network node,” “network component,” “network module,” and/or similar terms may be interchangeably used to generally describe a network device and do not have a particular or special meaning unless otherwise specifically stated and/or claimed within the disclosure. In one embodiment, the network element200is an apparatus configured to implement the decorrelating ALE400, the decorrelating adaptive filter600, or the ingress noise cancellation unit700to perform the methods1000,1100, and1200.

The network element200comprises one or more downstream ports210coupled to a transceiver (Tx/Rx)220, which are transmitters, receivers, or combinations thereof. The Tx/Rx220transmits and/or receives frames from other network nodes via the downstream ports210. Similarly, the network element200comprises another Tx/Rx220coupled to a plurality of upstream ports240, wherein the Tx/Rx220transmits and/or receives frames from other nodes via the upstream ports240. The downstream ports210and/or the upstream ports240may include electrical and/or optical transmitting and/or receiving components in another embodiment, the network element200comprises one or more antennas coupled to the Tx/Rx220. The Tx/Rx220transmits and/or receives data (e.g., packets) from other network elements wirelessly via the one or more antennas.

A processor230is coupled to the Tx/Rx220and is configured to process a data transmission to determine and cancel narrowband ingress noise. In an embodiment, the processor230comprises one or more multi-core processors and/or memory modules250, which functions as data stores, buffers, etc. The processor230is implemented as a general processor or as part of one or more application specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), and/or digital signal processors (DSPs). Although illustrated as a single processor, the processor230is not so limited and alternatively comprises multiple processors. The processor230further comprises a determination and cancellation module260that is configured to determine and cancel narrowband ingress noise in a data signal, and a power estimation module270that is configured to determine a power level of the narrowband ingress noise in the data signal.

FIG. 2also illustrates that a memory module250is coupled to the processor230and is a non-transitory medium configured to store various types of data. Memory module250comprises memory devices including secondary storage, read-only memory (ROM), and random-access memory (RAM). The secondary storage is typically comprised of one or more disk drives, optical drives, solid-state drives (SSDs), and/or tape drives and is used for non-volatile storage of data and as an over-flow storage device if the RAM is not large enough to hold all working data. The secondary storage is used to store programs that are loaded into the RAM when such programs are selected for execution. The ROM is used to store instructions and perhaps data that are read during program execution. The ROM is a non-volatile memory device that typically has a small memory capacity relative to the larger memory capacity of the secondary storage. The RAM is used to store volatile data and perhaps to store instructions. Access to both the ROM and RAM is typically faster than to the secondary storage.

The memory module250may be used to house the instructions for carrying out the various embodiments described herein. For example, alternatively, the memory module250comprises the determination and cancellation module260and the power estimation module270both of which are executed according to instructions from processor230.

Any processing of the present disclosure may be implemented by causing a processor (e.g., a general purpose multi-core processor) to execute a computer program, in this case, a computer program product can be provided to a computer or a network device using any type of non-transitory computer readable media. The computer program product may be stored in a non-transitory computer readable medium in the computer or the network device. Non-transitory computer readable media include any type of tangible storage media. Examples of non-transitory computer readable media include magnetic storage media (such as floppy disks, magnetic tapes, hard disk drives, etc.), optical magnetic storage media (e.g., magneto-optical disks), compact disc read-only memory (CD-ROM), compact disc recordable (CD-R), compact disc rewritable (CD-R/W), digital versatile disc (DVD), Blu-ray (registered trademark) disc (BD), and semiconductor memories (such as mask ROM, programmable ROM (PROM), erasable PROM, flash ROM, and RAM). The computer program product may also be provided to a computer or a network device using any type of transitory computer readable media. Examples of transitory computer readable media include electric signals, optical signals, and electromagnetic waves. Transitory computer readable media can provide the program to a computer via a wired communication line (e.g., electric wires, and optical fibers) or a wireless communication line.

FIG. 3is a schematic diagram of an embodiment of an ALE300. The ALE300is implemented in a CMTS, such as the CMTS110, and extracts a narrowband ingress noise (Nkfrom broadband signal noise (Bk) that both exist in the same signal transmission, for example a primary signal (Pk) between two devices such as the CMTS110and the CM150. By definition, the broadband signal noise is an uncorrelated signal, and the narrowband ingress noise is a correlated signal. To extract the narrowband ingress noise from the broadband signal noise, the ALE300determines an estimate of the narrowband ingress noise ({circumflex over (N)}k). Estimating the narrowband ingress noise includes the ALE300determining a reference signal (ek) according to a delay module302, and processing the reference signal and an error signal (ek), using an adaptive filter304. The reference signal is a delayed signal that is based on the primary signal and delayed by the delay module302for an amount of time delta (Δ). The error signal is determined by a summation module306as an approximation of the broadband noise signal that is a result of removing the estimate of the narrowband ingress noise from the primary signal. Delaying the primary signal to form the reference signal decorreates the broadband noise signal between the primary signal and the reference signal, thereby facilitating processing of both the primary signal and the reference signal by the ALE300to determine the broadband noise signal of the primary signal and the narrowband ingress noise according to the reference signal.

The adaptive filter304receives the reference signal from the delay module302and the error signal from the summation module306and, based on the reference signal, the error signal, and a plurality of filter coefficients (e.g., filter taps), determines the estimate of the narrowband ingress noise. The particular adaptive filter304that is used in the ALE300may be any suitable filter understood by one of ordinary skill in the art, for example, a least mean square (LMS) traversal filter. The summation module306receives the primary signal and the estimate of the narrowband ingress noise from the adaptive filter304and subtracts the estimate of the narrowband ingress noise from the primary signal to generate the error signal. The error signal is then transmitted by the summation module306to the adaptive filter304. The adaptive filter304updates the filter coefficients according to the error signal to improve accuracy of the estimate of the narrowband ingress noise. With each error signal transmitted to the adaptive filter304by the summation module306, the estimate of the narrowband ingress noise produced by the adaptive filter304converges to the narrowband ingress noise, for example, the estimate of the narrowband ingress noise progressively becomes closer to the narrowband ingress noise until the estimate of the narrowband ingress noise and the narrowband ingress noise are approximately the same. Correspondingly, as the estimate of the narrowband ingress noise converges to the narrowband ingress noise, the error signal converges to the broadband signal noise, for example, the error signal progressively becomes closer to the broadband signal noise until the error signal and the broadband signal noise are approximately the same.

FIG. 4is a schematic diagram of an embodiment of a decorrelating ALE400. The ALE400is implemented in a CMTS, such as the CMTS110, in place of the ALE300to provide expanded capabilities for processing a received signal. The ALE400extracts a Nkfrom Bkand band-limited data signal (Dk), and all of which exist in the same signal transmission, for example, a primary signal (Pk), between two devices such as the CMTS110and the CM150. The ALE400may further be implemented in a first stage of an ingress noise cancellation, such as at the step912of the method900. By definition, the broadband signal noise is an uncorrelated signal, the narrowband ingress noise is a correlated signal, and the oversampled band-limited data signal is a correlated signal. However, the broadband noise signal, the narrowband ingress noise, and the band-limited data signal are uncorrelated to each other in the primary signal. To extract the narrowband ingress noise from the broadband signal noise and the band-limited data, the ALE400determines an estimate of the narrowband ingress noise ({circumflex over (N)}k). Estimating the narrowband ingress noise includes the ALE400determining a reference signal xkaccording to a delay module402, and processing the reference signal and an error signal ekusing a decorrelating adaptive filter404. The reference signal is a delayed signal that is based on the primary signal and delayed by the delay module402for an amount of time Δ. The error signal is determined by a summation module406as an approximation of the broadband noise signal and the band-limited data signal that is a result of removing the estimate of the narrowband ingress noise from the primary signal. The error signal further comprises a cancelled output signal of the ALE400. Delaying the primary signal to form the reference signal decorrelates the broadband noise signal and the band-limited data signal between the primary signal and the reference signal, thereby facilitating processing of both the primary signal and the reference signal by the ALE400to determine the broadband noise signal and band-limited data signal of the primary signal and the narrowband ingress noise according to the reference signal.

The decorrelating adaptive filter404receives the reference signal from the delay module402and the error signal from the summation module406and, based on the reference signal, the error signal, and a plurality of filter coefficients (e.g., filter taps), determines the estimate of the narrowband ingress noise. The summation module406receives the primary signal and the estimate of the narrowband ingress noise from the decorrelating adaptive filter404and subtracts the estimate of the narrowband ingress noise from the primary signal to generate the error signal. The error signal is then transmitted by the summation module406to the decorrelating adaptive filter404. The decorrelating adaptive filter404updates the filter coefficients according to the error signal to improve accuracy of the estimate of the narrowband ingress noise. With each error signal transmitted to the decorrelating adaptive filter404by the summation module406, the estimate of the narrowband ingress noise produced by the decorrelating adaptive filter404converges to the narrowband ingress noise such that the estimate of the narrowband ingress noise progressively becomes closer to the narrowband ingress noise until the estimate of the narrowband ingress noise and the narrowband ingress noise are approximately the same. Correspondingly, as the estimate of the narrowband ingress noise converges to the narrowband ingress noise, the error signal converges to a combination of the broadband signal noise and the hand-limited data signal such that the error signal progressively becomes closer to the combination of the broadband signal noise and the band-limited data signal until the error signal and the combination of the broadband signal noise and the hand-limited data signal are approximately the same. The error signal that is output by the ALE400comprises the primary signal after cancellation of the narrowband signal noise, also referred to as the primary signal with noise cancellation, as determined by the summation module406.

FIG. 5is a schematic diagram of an embodiment of an adaptive filter500. The adaptive filter500is implemented in an ALE, such as the adaptive filter304in the ALE300, which may be implemented in the CMTS110. The adaptive filter500comprises an LMS traversal filter and is one embodiment of the adaptive filter304. The adaptive filter500determines the estimate of the narrowband ingress noise according to a filter algorithm, for example, an LMS algorithm that comprises a plurality of incremental steps. Alternatively, the adaptive filter500is any suitable filter type understood by one of ordinary skill in the art. The adaptive filter500is implemented in an ALE, such as the ALE300, and receives a reference signal that is a delayed version of a primary signal. The adaptive filter500additionally receives an error signal that is an output of the ALE. Using the error signal, the adaptive filter500determines a plurality of filter coefficients, which may also be referred to as filter taps. The adaptive filter500then determines the estimate of the narrowband ingress noise based on the reference signal and the filter coefficients, and according to:
{circumflex over (N)}k=Σi=1Mci,k*xk−i+1(1)
in which ci,kis the current filter coefficient, M is a total number of filter coefficients used, and is the reference signal delayed by an additional amount.

The adaptive filter500determines the filter coefficients according to a coefficient module (not shown). The coefficient module determines the filter coefficients based on the reference signal and the error signal, and according to:
ci,k+1=ci,k+μek*xk−i+1(2)
in which ci,k+1is a next filter coefficient as determined by the coefficient module, μ is a step size of the LMS algorithm, and ek* is a conjugate of the error signal. After the coefficient module determines the filter coefficients, the filter coefficients are transmitted to the multiplication modules504. The multiplication modules504receive the filter coefficients from the coefficient module and perform a multiplication of the filter coefficients with further delayed versions of the reference signal received from delay modules502according to a portion of equation 1. A summation module506receives the multiplication results from the multiplication modules504and determines a sum of the multiplication results of the multiplication modules504according to a portion of equation 1. The multiplication modules504and the summation module506are implemented as separate modules that together perform the complete functionality of equation 1. Alternatively, the multiplication modules504and the summation module506are both implemented in a single module that performs the functionality of equation 1. After determining the sum of the multiplication results of the multiplication modules504, the summation module506outputs the estimate of the narrowband ingress noise.

FIG. 6is a schematic diagram of an embodiment of a decorrelating adaptive filter600. The decorrelating adaptive filter600is implemented in an ALE, such as the decorrelating adaptive filter404in the ALE400. Which may be implemented in the CMTS110. The decorrelating adaptive filter600receives the reference signal that is the delayed version of the primary signal. Implementing the decorrelating adaptive filter600in the ALE400enables the ALE400to determine narrowband ingress noise of a signal in the time domain and in the presence of a data transmission. For example, the decorrelating adaptive filter600enables the ALE400to determine narrowband ingress noise without scheduling a quiet period in in the signal during which the data transmission is paused. The decorrelating adaptive filter600additionally receives an error signal that is an output of the ALE400. To decorrelate the oversampled band-limited data signal component of the reference signal of ALE400, the decorrelating adaptive filter600is configured to select a plurality of samples of the data symbols by selecting not more than one sample from each data symbol during an iteration k of filtering. Although selecting samples from different data symbols results in the band-limited data signal becoming uncorrelated, the narrowband ingress noise remains a correlated signal due to its slow variation in time. A number of samples selected from the data symbols is determined according to a number of coefficients of the decorrelating adaptive filter600. For example, for a decorrelating adaptive filter600having 3 filter coefficients, samples from 3 different data symbols are selected. For a decorrelating adaptive filter600having 4 filter coefficients, samples from 4 different data symbols are selected. Generally, for a decorrelating adaptive filter600having M filter coefficients, samples from M different data symbols are selected. For example, using the symbols of diagram800for exemplary purposes, in a first iteration of the decorrelating adaptive filter600having 5 filter coefficients, samples s1, s4, s7, s10, and s13are selected. In a second iteration, samples s2, s5, s8, s11, and s14are selected. In a third iteration, samples s3, s6, s9, s12, and s15are selected. It should be noted that an order of selection of symbols from which the samples are selected is a matter of design choice.

The decorrelating adaptive filter600determines the estimate of the narrowband ingress noise according to the error signal and the reference signal by determining a plurality of filter coefficients. The decorrelating adaptive filter600then determines the estimate of the narrowband ingress noise based on the reference signal and the filter coefficients, and according to:

N^k=∑i=1M⁢ci,k*xk-[∑j=0i-1⁢Pj](3)
in which M is a total number of filter coefficients used,

xk-[∑j=0i-1⁢Pj]
is the reference signal delayed by an additional amount, and Pjis the additional amount of delay.

The decorrelating adaptive filter600determines the filter coefficients according to a coefficient module (not shown). The coefficient module determines the filter coefficients based on the reference signal and the error signal, and according to:

ci,k+1=ci,k+μ⁢⁢ek*⁢xk-[∑j=0i-1⁢Pj](4)
in which ci,kis a preceding filter coefficient as determined by the coefficient module, μ is a step size of the LMS algorithm, and ek* is a conjugate of the error signal. After the coefficient module determines the filter coefficients, the filter coefficients are transmitted to the multiplication modules604. The multiplication modules604receive the filter coefficients from the coefficient module and perform a multiplication of the filter coefficients with additionally delayed versions of the reference signal received from delay modules602according to a portion of equation 3. The delay modules602implement the additional delay into the reference signal used in equations 3 and 4 to enable the decorrelating adaptive filter600to select the samples from different data symbols. The delay modules602delays the reference signal for filter coefficient i according to Pi−1where P0=0. Subsequent delays P1, P2, . . . , PM−1are chosen by the delay modules602such that the samples for the successive filter coefficients are not selected from the same data symbol.

A summation module606receives the multiplication results from the multiplication modules604and determines a sum of the multiplication results of the multiplication modules604according to a portion of equation 3. The multiplication modules604and the summation module606are implemented as separate modules that together perform the complete functionality of equation 3. Alternatively, the multiplication modules604and the summation module606are both implemented in a single module that performs the functionality of equation 3. After determining the such of the multiplication results of the multiplication modules604, the summation module606outputs the estimate of the narrowband ingress noise.

Although the foregoing descriptions have referred to an ALE, an LMS algorithm, and an LMS traversal filter structure, such descriptions serve only as exemplary implementation manners in which noise cancellation according to the present disclosure may be implemented. As would be understood by one skilled in the art, the noise cancellation of the present disclosure may be implemented in a plurality of applications, algorithms, and filter structures, all of which are within the scope of the present disclosure.

FIG. 7is a schematic diagram of an embodiment of an ingress noise cancellation unit700. The ingress noise cancellation unit700is implemented in a CMTS, such as the CMTS110, and performs cancellation of ingress noise in a signal received from an upstream source according to an estimate of ingress noise, for example, as determined by the ALE400. In some circumstances, coarse cancellation of the narrowband component noise, which is also referred to as the narrowband ingress noise, from a received signal, such as a primary signal, is not necessary due to a relatively low power level of the narrowband component noise. For example, when the power level of the narrowband component noise, such as the estimate of the relative power level of the narrowband component noise according to method1100, is below a threshold value, the narrowband component noise does not need to be cancelled from the received signal according to a coarse cancellation of a first stage, such as first stage902of the method900, of a CMTS, such as CMTS110. Accordingly, the ingress noise cancellation unit700facilitates selective first state coarse cancellation of narrowband component noise in the CMTS110.

A comparator702compares the estimate of the relative power level of the narrowband component noise to a known threshold value. The threshold value indicates a power level over which the first stage cancellation will be performed, and under which the first stage cancellation will not be performed. The comparator702receives the estimate of the relative power level of the narrowband component noise from an ingress noise power estimator704. When the estimate of the relative power level of the narrowband component noise does not exceed the threshold, the comparator702outputs a first control signal, for example, a digital logic “0,” When the estimate of the relative power level of the narrowband component noise does exceed the threshold, the comparator702outputs a second control signal, for example, a digital logic “1.” The ingress noise power estimator704is configured to estimate the relative power level of the narrowband component noise according to an estimation method, such as the method1100, and is implemented in the CMTS110.

The ingress noise cancellation unit700also includes a delay unit708, a decorrelating adaptive filter710, and a summation module706which are substantially similar to the delay unit402, the decorrelating adaptive filter404, and the summation module406, respectively, as discussed above and not repeated here for the sake of brevity and simplicity. Collectively, the delay unit708, the decorrelating adaptive filter710, and the summation module706are referred to as a decorrelating ALE (D-ALE)718, which corresponds to the decorrelating ALE400in structure and function. A delay module714receives the primary signal and delays the primary signal prior to transmitting the primary signal to a multiplexer716. An amount of time by which the delay module714delays the primary signal corresponds to an amount of time consumed by the decorrelating ALE718and comparator702prior to providing other inputs to the multiplexer716. As a result of the delay implemented by the delay module714, an overall amount of delay of the ingress noise cancellation unit700is approximately equal regardless of whether the CMTS110performs first stage coarse cancellation of narrowband component noise.

The multiplexer716receives the delayed primary signal from the delay module714, an error signal that comprises the primary signal after first stage coarse cancellation of narrowband component noise from the decorrelating ALE718, and the first or the second control signal from the comparator702. According to the first or the second control signal received from the comparator702, the multiplexer716outputs either the delayed primary signal or the primary signal after first stage coarse cancellation of narrowband component noise. For example, when the multiplexer716receives the first control signal of “0,” the multiplexer716outputs the delayed primary signal. When the multiplexer716receives the second control signal of “1,” the multiplexer716outputs the primary signal after first stage coarse cancellation of narrowband component noise.

FIG. 8is a schematic diagram800of an embodiment of sampled data symbols. In various applications, oversampling data symbols, for example, sampling data symbols at greater than one sample, per data symbol is advantageous. The sampling is performed in a first stage of an ingress noise cancellation method, for example, by a CMTS110that is implementing the method900. As shown in diagram800, the symbols802,804,806,808, and810are sampled at a rate of 3 samples per symbol. For the sake of clarity, narrowband ingress noise and broadband signal noise are not shown on diagram800, though such noise would be present in the data symbols802-810as would be understood by one skilled in the art.

Each symbol802-810is uncorrelated with respect to another of the symbols802-810. However, each sample from one symbol802-810is correlated amongst the other samples of the same symbol802-810. For example, sample s1, s2, and s3are correlated, because the samples s1, s2, and s3are all from symbol802. Samples s1, s5, and s11are uncorrelated, because the samples s1, s5, and s11are each from different symbols—symbol802, symbol804, and symbol808, respectively. Generally, a set of samples from the data symbols802-810in which each sample of the set of samples is selected from a different one of the data symbols802-810results in a set of uncorrelated samples.

FIG. 9is a flowchart of an embodiment of a method900of ingress noise cancellation. The method900is implemented in a network element, such as the network element200to process signals that are received from an upstream source. The method900is implemented, for example, in a receiver in a communications system, such as the CMTS110in the DOCSIS network100. To cancel ingress noise, the method900comprises a plurality of stages. For example, a first stage902that performs coarse noise cancellation and a second stage904that performs fine noise cancellation. The first stage902is located in a digital front end portion of the network element and samples a data signal of a plurality of data symbols at a rate of two or more samples per symbol. The second stage904follows the first stage902in the network element and processes the data signal at a sampled rate of 1 sample per symbol.

At step906, a data signal is received from an upstream node in the network. For example, the data signal is received by the CMTS110from the CM150. The data signal comprises a plurality of symbols that make up the signal's data. At step908, the data signal is converted from an analog data signal to a digital data signal. For example, the data signal is converted from a continuous analog signal to a digital signal that comprises a plurality of discrete data points according to an analog-to-digital converter (ADC). At step910, the data signal is processed by a digital front end of the network element. Processing by the digital front end differs according to implementations of the method900and includes functions understood by one skilled in the art. For example, the step910includes sampling the data signal to form a plurality of samples, for example, 2 samples, per data symbol. Alternatively the data symbols are sampled at any other suitable sampling rate, such as 4 samples per data symbol. At step912, a first ingress noise canceller determines and cancels coarse noise in the data signal. Cancelling the coarse noise in the data signal at step912protects components that perform subsequent steps of the method900from damage resulting from the coarse noise which may have a high level of power. The step912is performed, for example, by an ALE such as the ALE400.

At step914, burst detection is performed on the data signal. The burst detection, for example, determines data bursts for processing that are contained in the data signal. At step916, timing recovery is performed. The timing recovery enables a network element to synchronize an internal clock rate with a frequency of the data symbols of the data signal, thereby enabling the network element to sample the data symbols at a time in which the data symbol has an optimum value, for example, a maximum, or peak, value. Synchronization is performed, for example, by compensating for a timing phase offset and a timing frequency offset of the data symbols in the digital signal. After the synchronization is established with the data symbols, the data symbols are sampled at a rate of 1 sample per data symbol

At step918, frequency and phase recovery are performed. A network element performs frequency and phase recovery by comparing a frequency and phase of the sampled data symbols to a frequency and phase of a local oscillator of the network element and performing compensation. Compensating the sampled data symbols for frequency and phase variations enables the network element to perform demodulation and processing of the data symbols in the digital signal. At step920, a second ingress noise canceller cancels fine, or low-level, ingress noise in the digital signal. Cancelling the fine ingress noise improves a MER of the digital signal. The step920is performed, for example, by a decision directed based linear predictor implemented in the network element. Alternatively, the step920is performed by an ALE such as the ALE300. At step922, forward error correction is performed on the data symbols of the data signal prior to the data signal being transmitted to another component for processing. Forward error correction reduces errors in data transmission, for example, through transmission lines that suffer from degradation, high levels of noise, or are unreliable, by introducing redundancy into the data signal. For example, in one implementation of forward error correction, each data symbol of a data signal is transmitted 3 consecutive times. In another implementation of forward error correction, a plurality of previously received data symbols is evaluated to determine how a present data symbol should be read.

FIG. 10is a flowchart of an embodiment of another method1000of ingress noise cancellation. The method1000is implemented in a network element, such as the CMTS110, to cancel ingress noise in signals received from an upstream source. At step1002, a signal is received from an upstream source. For instance, the CMTS110located in a central office receives the signal from a CM150located in a subscriber location. The received signal comprises a plurality of components, for example, a broadband component noise, a narrowband component noise, and a data component. At step1004, a reference signal is generated in a time domain according to the received signal. For instance, the CMTS110determines the reference signal according to the received signal by delaying the received signal by a predetermined amount of time delta. The CMTS110delays the received signal according to a delay module, such as the delay module402.

At step1006, an error signal is determined in the time domain based on the received signal. For instance, the CMTS110determines the error signal based on the received signal. For example, the CMTS110determines the error signal according to a decorrelating ALE, such as the ALE400, by subtracting an estimate of the narrowband component noise from the received signal. After the CMTS110subtracts the estimate of the narrowband component noise from the received signal, the error signal is approximated by the broadband component noise and the data component of the received signal. At step1008, the estimate of the narrowband component noise of the reference signal is determined in the time domain. For instance, the CMTS110determines the estimate of the narrowband component noise according to a decorrelating adaptive filter, such as the decorrelating adaptive filter600, according to the equations 3 and 4, discussed above. Through processing the received signal in subsequent iterations, the CMTS110converges a value of the estimate of the narrowband component noise to an actual value of the narrowband component noise such that the estimate of the narrowband component noise is about equal to the actual value of the narrowband component noise.

FIG. 11is a flowchart of an embodiment of a method1100of ingress noise power estimation. According to an estimate of a narrowband component noise of a signal having a narrowband component noise, a broadband component noise, and a data component, an estimate of a power level of the narrowband component noise can be determined by the CMTS110. The CMTS implements the method1100when a signal is received from an upstream source and determines the estimate of the power level of the narrowband component noise, which may also be referred to as an estimate of a power level of ingress noise, according to an output of a decorrelating adaptive filter, such as the ALE400. Alternatively, the method1100is implemented by another adaptive filter understood by one skilled in the art. The method1100is implemented in a first stage, a second stage, or both of an ingress noise canceller. For example, the method1100is implemented in the first stage902, the second stage904, or both, of the method900. Implementing the method1100in both the first stage902and the second stage904and combining the estimate of the power level of the narrowband component noise according to the estimate of the power level of the narrowband component noise from the first stage902and the estimate of the power level of the narrowband component noise from the second stage904may increase an accuracy level of the method1100.

At step1102, a signal is received from an upstream source. For instance, a CMTS110located in a central office receives the signal from a CM150located in a subscriber location. The received signal comprises a plurality of components, for example, a broadband component noise, a narrowband component noise, and a data component. At step1104, an estimate of narrowband component noise is determined in a time domain. For instance, the CMTS110determines the estimate of narrowband component noise according to embodiments of the present disclosure as previously discussed. For example, the CMTS110determines the estimate of narrowband component noise by implementing the ALE400and decorrelating adaptive filter600to perform the method1000and estimate the narrowband component noise.

At step1106, an estimate of a power level of the narrowband component noise is determined in the time domain. For instance, the CMTS110estimates the power level of the narrowband component noise according to the estimation of the narrowband component noise. Because the value of the estimate of the narrowband component noise converges to the actual value of the narrowband component noise, a variance of the narrowband component noise is approximately equal to a variance of the estimate of the narrowband component noise according to:
var{Nk}≅var{{circumflex over (N)}k}  (5)
in which var indicates a variance operation. The CMTS110estimates the power level of the narrowband component noise in decibels (dB) according to:
Estimate in dB=10*log 10[var{{circumflex over (N)}k}]  (6)
in which log is a logarithmic function. Because the estimate of the power level of the narrowband component noise according to equation 6 is not determined with respect to any other component of the received signal, the estimate of the power level of the narrowband component noise may be referred to as an estimate of the absolute power level of the narrowband component noise.

In a communications system having a signal that comprises a data component and a narrowband component, an estimate of a relative power level of the narrowband component noise with respect to the data component of the received signal, indicated in dBc, is desirable. The CMTS110estimates the relative power level of the narrowband component noise in dBc, also referred to as the power level of the narrowband component with respect to the data component, by determining a relationship of the narrowband component noise Nkto the data component Dkaccording to:

var⁢{Nk⁢w·r·t⁢⁢Dk}=var⁢{Nk}var⁢{Dk}(7)
and substituting the equation 7 into the equation 6 as will be shown below. To facilitate processing of the received signal to determine the relative power, the received signal is represented according to:
Pk+Dk+Nk+Bk(8)

As discussed above, each component of the received signal is by definition uncorrelated with respect to the other components of the received signal. As a result, a variance of the received signal equals a sum of the variances of each component of the received signal according to:
var{Pk}=var{Dk}+var{Nk}+var{Bk}  (9)
Rearranging equation 9 to isolate the variance of the data component, and substituting the variance of the estimate of the narrowband component noise for the variance of the narrowband component noise according to equation 5, results in the variance of the data component being approximately equal to:
var{Dk}≅var{Pk}−var{{circumflex over (N)}k}−var{Bk}  (10)

The equation 10 and the equation 5 are substituted into the equation 7 to enable processing according to the equation 7 using available results calculated by the CMTS110. The modified equation 7 with the substituted equations 10 and 5 determines the relationship of the narrowband component noise to the data component according to:

Estimate⁢⁢in⁢⁢dB⁢c=10*log⁢⁢10⁡[var⁢{N^k}var⁢{Pk}-var⁢{N^k}-var⁢{Bk}](12)
In communications systems, for example the DOCSIS network100, a power level of the broadband component noise of a received signal is substantially lower than a power level of the data component of the received signal. For example, the power level of the broadband component noise is 25+ dB lower than the power level of the data component. As a result, the equation 12 is modified to ignore the variance of the broadband component noise and simplify the determination of the estimate of the relative power level of the narrowband component noise. The CMTS110estimates the relative power level of the narrowband component noise in dBc based on the simplified equation 12 according to:

Optionally, the method1100includes a step1108in which the CMTS110manages the DOCSIS network100in the time domain according to the estimate of the relative power level of the narrowband component noise. For instance, according to the estimate of the relative power level of the narrowband component noise, the CMTS110dynamically adapts signal parameters to control modulation order, forward error correction, and modulation rate. For example, the CMTS110transmits one or more signal parameters to the CM150that define desired characteristics of a signal received by the CMTS110from the CM150. Additionally, according to the estimate of the relative power level of the narrowband component noise, the CMTS110dynamically adds or removes data channels in a set of data channels being processed by the CMTS110. Additionally, according to the estimate of the relative power level of the narrowband component noise, the CMTS110schedules data channels in the DOCSIS network100according to quality of service requirements in the DOCSIS network100. Additionally, according to the estimate of the relative power level of the narrowband component noise, the CMTS110increases a Proactive Network Management capability of the DOCSIS network100. Additionally, according to the estimate of the relative power level of the narrowband component noise, the CMTS110determines whether to perform cancellation of the narrowband component noise or not perform cancellation.

FIG. 12is a flowchart of an embodiment of a method1200of bypassing a first stage of ingress noise cancellation. The method1200is implemented in a CMTS, such as the CMTS110to process a signal received from an upstream source by cancelling ingress noise in the signal prior to transmitting the signal to a next signal processing block of the CMTS, or by transmitting the signal to the next signal processing block of the CMTS without performing ingress noise cancellation. At step1202, a signal is received from an upstream source, for instance a CMTS110located in a central office receives the signal from a CM150located in a subscriber location. The received signal comprises a plurality of components, for example, a broadband component noise, a narrowband component noise, and a data component. At step1204, an estimate of the narrowband component noise is determined. For instance, the CMTS110determines the estimate of the narrowband component noise according to an ALE, such as the ALE400that is configured to implement the method1000, discussed above. At step1206, an estimate of a relative power level of the narrowband component noise is determined. For instance, the CMTS110determines the estimate of the relative power level of the narrowband component noise according to the ALE400that is further configured to implement the method1100, discussed above.

At decision diamond1208, a determination is made based on the estimate of the relative power level of the narrowband component noise and a threshold power level. When the estimate of the relative power level of the narrowband component noise does not exceed the threshold power level, at step1210, the CMTS110outputs the received signal after a delay, for example, according to the signal received by the multiplexer716from the delay unit714in the ingress noise cancellation unit700. When the estimate of the relative power level of the narrowband component noise exceeds the threshold power level, at step1212, the CMTS110outputs the received signal after first stage coarse cancellation of narrowband component noise, for example, according to the signal received by the multiplexer716from the decorrelating ALE.718in the ingress noise cancellation unit700.

FIG. 13is a graph1300of a MER versus filter length in number of taps according to an embodiment of the present disclosure. The MER can also be referred to as a signal-to-noise (SNR) ratio. The graph1300illustrates performance according the present disclosure, for example, according to the decorrelating ALE400, the decorrelating adaptive filter600, the ingress noise cancellation unit700, and the methods1000,1100, and1200, compared with performance of a non-decorrelating or traditional ALE and adaptive filter cancellation scheme. In the graph1300, the X-axis represents a length of a filter, for example a number of filter taps or a number of filter coefficients, used for noise determination and cancellation, and the Y-axis represents the MER measured in dB. As shown in the graph1300, for a data signal having a plurality of data symbols sampled at a rate of 4 samples per data symbol and an in-band ingress tone level of +10 dBc, processing of the data signal according to the present disclosure results in a MER that is improved over the traditional ALE scheme by an amount ranging from 2.5 dB to 5.5 dB, depending on the filter length.

FIG. 14is a graph1400of a magnitude of predicted ingress noise according to an embodiment of the present disclosure. The graph1400illustrates a magnitude of estimated narrowband component noise versus time according to processing as disclosed in the present disclosure, for example, according to the decorrelating ALE400, the decorrelating adaptive filter600, the ingress noise cancellation unit700, and the methods1000,1100, and1200, compared with a traditional ALE noise determination and cancellation scheme, and an actual value of the narrowband component noise, in the graph1400, the X-axis represents an amount of time measured in samples taken of a data signal and the Y-axis represents a linear magnitude of the estimate of the narrowband component noise. As shown in graph1400, for a data signal at an in-band ingress level of +10 dBc, processing of the data signal according to the present disclosure results in a magnitude of the estimated narrowband component noise that represents the actual narrowband component noise more closely than the traditional ALE scheme.

FIG. 15is a graph1500of ingress noise power estimation accuracy according to an embodiment of the present disclosure. The graph1500illustrates accuracy of an estimate of a power level of narrowband component noise in dBc for a plurality of broadband noise levels in a filter with 16 filter taps and a signal level of 0 dB, as determined according to the present disclosure. In the graph1500, the X-axis represents an actual value of a power level of the narrowband component noise in dBc and the Y-axis represents an estimated value of the power level of the narrowband component noise in dBc, for example, the estimate according to the method1100. As shown in the graph1500, for narrowband component noise power levels greater than −20 dBc, the present disclosure provides for a high degree of accuracy in estimating the power level of the narrowband noise component. It should be noted that the lower limit of −20 dBc in the graph1500is a limitation of the exemplary 16-tap filter used in simulation and is not limited according to the present disclosure. Increasing the number of taps in the filter results in an increased range of measurement that allows narrowband component noise below −20 dBc to be determined and cancelled.

FIG. 16is another graph1600of ingress noise power estimation accuracy according to an embodiment of the present disclosure. The graph1600illustrates accuracy of an estimate of a power level of narrowband component noise in dB for a plurality of broadband noise levels in a filter with 16 filter taps and a signal level of 0 dB, as determined according to the present disclosure. In the graph1600, the X-axis represents an actual value of a power level of the narrowband component noise in dB and the Y-axis represents an estimated value of the power level of the narrowband component noise in dB, for example, the estimate according to the method1100. As shown in the graph1600, for narrowband component noise power levels greater than 0 dB, the present disclosure provides for a high degree of accuracy in estimating the power level of the narrowband noise component. Again, it should be noted that the lower limit of −20 dBc in the graph1600is a limitation of the exemplary 16-tap filter used in simulation and is not limited according to the present disclosure. Increasing the number of taps in the filter results in an increased range of measurement that allows narrowband component noise below −20 dBc to be determined and cancelled.

FIG. 17is yet another graph1700of ingress noise power estimation accuracy according to an embodiment of the present disclosure. The graph1700illustrates narrowband component noise power level estimation accuracy over a range of signal power levels in a filter with 16 filter taps and a broadband component noise of −25 dBc. In the graph1700, the X-axis represents an actual value of a power level of the narrowband component noise in dBc and the Y-axis represents an estimated value of the power level of the narrowband component noise in dBc. As shown in the graph1700, for signal power levels ranging from −30 dB to +30 dB, the present disclosure provides for a high degree of accuracy in estimating the power level of the narrowband component noise. It should be noted that processing according to the present disclosure is not limited to processing a signal less than +30 dB. For example, according to embodiments of the present disclosure, a signal having a power level of +40 dB, +50 dB, +60 dB, or any other power level greater than +30 dB are also be processed.

The use of the term “about” means a range including at least ±10 percent (%) of the subsequent number, unless otherwise stated. While several embodiments have been provided in the present disclosure, it should be understood that the disclosed systems and methods might be embodied in many other specific forms without departing from the spirit or scope of the present disclosure. The present examples are to be considered as illustrative and not restrictive, and the intention is not to be limited to the details given herein. For example, the various elements or components may be combined or integrated in another system or certain features may be omitted, or not implemented.