Abstract:
Network health monitoring and network failure detection prediction using opportunistic scheduling and measurement is contemplated. The health monitoring may be facilitated with opportunistic scheduling and measurement of pilot power in various bands to detect harmonics induced by equipment suffering from non-linearity or other distortions.

Description:
TECHNICAL FIELD 
     The present invention relates to facilitating network failure detection and prediction using measurements, such as but not necessarily limited to identifying non-linear performance as a function of energy measurements associated with multiple band pilot signals. 
     BACKGROUND 
     A wireless, wireline or combined wireless-wireline network may rely on any number of devices to process signals for transport. The health, operational status or other characteristics related to the performance of these devices may be important to maintaining proper operation of the network and desired levels of service. A service provider may be tasked with supporting larger, wide area networks, such as but not necessarily limited to those associated with a hybrid-fiber cable (HFC) network, a cable network, a cellular network, an optical network or other network providing long-haul signaling transport, as well as smaller, local area networks, such as a home wireless/wireline network, Wi-Fi hotspot or other network interconnecting user devices with the long-haul transport network. One non-limiting aspect of the present invention contemplates providing such service providers and other interested entities with an ability to identify health, operational status or other characteristics of devices within their networks, optionally identifying such characteristics for devices at an individual level. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a system for transporting signals in accordance with one non-limiting aspect of the present invention. 
         FIG. 2  illustrates measured energies in accordance with one non-limiting aspect of the present invention. 
         FIG. 3  schematically illustrates a diagram for detecting non-linear performance of the device in accordance with one non-limiting aspect of the present invention. 
         FIG. 4  illustrates a flowchart of a method for identifying device performance in accordance with one non-limiting aspect of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. 
       FIG. 1  illustrates a system  10  for transporting signals in accordance with one non-limiting aspect of the present invention. The system  10  is shown with respect to a transmitter  12  being configured to transport signaling over a network  14  for receipt at a receiver  16 . The receiver  16  may be configured to further process the transported signaling for output to a device (not shown) and/or interfacing with a user. The system  10  may be configured to facilitate transporting virtually any type of signaling between a first location/device (e.g., the transmitter  12 ) and a second location/device (e.g., the receiver  16 ). Optionally, the signaling transported over through the network  14  may traverse one or multiple wired and/or wireless mediums before reaching the receiver  16 , such as in the manner described in the patent applications referenced above and/or described in U.S. patent application Ser. No. 14/181,640, filed Feb. 15, 2014, and entitled Multiple-Input Multiple-Output (MIMO) Communication System, the disclosure of which is hereby incorporated by reference in its entirety. The relationship of the transmitter  12  and the receiver  16  is shown for exemplary non-limiting purposes as the present invention fully contemplates the transmitter  12  acting as a receiver or a client in some circumstances and the receiver  16  acting as a transmitter or a server in some circumstance. 
     The network  14  is shown to include a device  18  disposed between the transmitter and receiver  12 ,  16 . The device  18  may be one of many devices included as part of the network  14  or otherwise associated with one or both of the transmitter and/or the receiver  12 ,  16  to facilitate signaling. The device  18 , like the transmitter and the receiver  12 ,  16 , may be any type of element having capabilities sufficient to facilitate processing signaling traveling between the transmitter and receiver  12 ,  16  and/or any other device connected thereto or otherwise in communication therewith.  FIG. 1  illustrates an exemplary positioning of the device  18  relative to the transmitter and receiver  12 ,  16  in order to demonstrate an ability of present invention to assess the health, operational status or other characteristics of the device  18  when processing signals communicated from the transmitter  12  to receiver  16  over the network  14 . The device  16  may be disposed in any position within the network  14  and need not necessarily be disposed between the transmitter and the receiver  12 ,  16 . The network  14  also need not possess the capabilities to facilitate signaling or message routing and instead may be a testing environment where the transmitter  12  is a signaling source and the receiver  16  is a sink capable of enabling the device  18  to output the processed signaling, e.g., the present invention may be useful and testing devices  18  prior to being deployed within an operational network. 
     The present invention is predominantly described with respect to facilitating identifying performance of the device  18  when the network  14  is a fully operational network. The use of the present invention with fully operational networks  14  may be beneficial as such networks  14  may include many devices  18  and the present invention may be utilized to individually identify any improperly performing one or more of the devices  18 . The device  18  may be operable within any public or private network  14  and include capabilities sufficient to facilitate processing of signals transmitted according to but not limited to Orthogonal Frequency Division Multiplexing (OFDM), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier Frequency Division Multiple Access (SC-FDMA), and any other modulation technique that allow granular allocation of signals in narrow frequency bands. The device  18  may be configured to facilitate processing signals communicated according to any number of standards and/or protocols, such as but not necessary limited to Data Over Cable Service Interface Specifications (DOCSIS) 3.1, Long Term Evolution (LTE), LTE-Advanced (LTE-A), Wi-Max, Wi-Fi, Digital Video Broadcasting-Terrestrial (DVB-T), Digital Video Broadcasting-Handheld (DVB-H), etc., the disclosures of which are hereby incorporated by reference in their entireties. One non-limiting aspect of the present invention contemplates the device  18  being an amplifier configured to linearly amplify signaling. Of course, the present invention is not necessarily limited to amplifiers and fully contemplates its use and application of facilitating identifying performance of other devices  18 , including fiber optic transmitters and receivers, LEDs, Laser Transmitters, Laser Receivers and Photo diodes. 
     The system  10  may include a controller  20  to assess performance of the device  18 . The controller  20 , or other element tasked with undertaking the performance identification contemplated herein, may include a non-transitory computer-readable medium having a plurality of instruction operable with a processor and sufficient for identifying performance of the device  18 , including actual performance or predicted performance. The controller  20  is shown for exemplary non-limiting purposes as being in communication with the transmitter and receiver  12 ,  16 . The controller  20  may use this communication capability to facilitate instructing the transmitter  12  to transmit particular signaling to the receiver  16  and to determine the signals actually received by the receiver  16 , i.e., the signals as processed by the device  18 . In the event to the present invention is employed within a operational network or network  14  having a plurality of devices  18 , the controller  20  may include capabilities sufficient for selectively directing signaling to desired ones of the devices  18  and/or measuring signals output therefrom. Of course, the present invention is not necessarily so limited and fully contemplates the controller  20  being otherwise arranged relative to the transmitter  12 , the receiver  16  and/or the device  18 . Optionally, the controller  20  may be a more passive device, e.g., instead of actively instructing the transmitter  12  and/or the receiver  16  to transmit signals and to report received signals, the controller  20  may be configured to monitor signals input to or output from the device  18  and/or signals transmitted from the transmitter  12  and received at the receiver  16  independently of instructions from the controller. 
     The controller  20  may be configured in accordance in the present invention to facilitate identifying equipment failure or other equipment related performance, and is for exemplary non-limiting purposes predominantly described with respect to identifying performance for the device  18  being configured as an amplifier. The amplifier  18  may be configured to amplifier, attenuate or otherwise processed signaling communicated therethrough, e.g., the amplifier  18  may be a linear device configured to perform linear operations on the signaling. The controller  20  may be configured to identify the performance of the amplifier  18  or other linearly operating RF component using opportunistically placed pilots, such as but not necessary limited to those used within OFDM/OFDMA frames. The opportunistically placed pilots or test signals may be processed with the amplifier  18 , optionally along with any additional signaling passing therethrough, so as to enable the controller  20  to identify/predict performance, failure, non-linearity, etc. as a function of how the amplifier processes the pilots (nulls). OFDM/OFDMA and similar technologies may allow granular allocation of signals in narrow frequency bins whereby the overall signal is composed of parallel signal transmission across frequency bins that compose the complete bandwidth (spectrum), such as in the manner described in United States an application Ser. No. 13/759,908, filed Feb. 5, 2013, and entitled Transmission Opportunity Scheduling, the disclosure of which is hereby incorporated by reference in its entirety. 
     The output of non-linear operating amplifiers may be described by a Taylor series:
 
 f ( x )= Ax+Bx   2   +Cx   3 + . . .
 
     Based on this, the output of the non-linear operating amplifier  18  may include higher order harmonics ( 2   nd , 3 rd , etc. order harmonics) due to the mixing of frequencies. For example, the mixing of two frequencies (f 1 ,f 2  such that f 2 &gt;f 1 ) due to second order non-linearity will generate signals at f 1 +f 2 , f 2 −f 1 ,  2   xf   1 , 2   xf   2 , and similarly, 3 rd  order non-linearity will generate signals at  3   xf   1 ,  3   xf   2 ,  2   xf   1 −f 2 ,  2   xf   2 −f 1 , etc. The present invention contemplates facilitating performance identification for wired or wireless systems using OFDM/OFDMA modulation (such as DOCSIS 3.1, LTE, LTE-A, WiMAX, WiFi, DVB-T, DVB-H, etc.) to detect whether an RF front end amplifier or other linearly operational device is failing or over-driven and operating in the non-linear region and thus requires maintenance/repair. The controller  20  may be configured in accordance with the present invention to facilitate this assessment by instructing the transmitter  12  (CMTS/eNode-B, Base Station, Access point, etc.) to select one or more frequency bins (f 1 ,f 2 , . . . fn) and two symbol slots (t 1 ,t 2 ) for the pilots, optionally back to back, that shall be monitored by the receiver  16 , i.e., following processing by the device  18  under test. 
     The controller  20  may be configured to schedule or otherwise enable the transmitter  12  to send no energy in certain allocations [(t 1 ,f 1 ), (t 1 ,f 2 ), . . . (t 1 ,fn)], i.e. the no energy allocations may be nulled to include essentially no energy, and to schedule or otherwise enable the transmitter  12  to send a known symbol or pilot in certain allocations [(t 2 ,f 1 ), (t 2 ,f 2 ), . . . (t 2 ,fn)], i.e., the energized allocations may include a known amount of energy. The controller  20  may be configured to schedule or otherwise enable the transmitter  12  to send no energy at allocations that correspond to the second and third harmonic components, or other harmonics, during t 1  and t 2  such as the allocations  24  shown in  FIG. 2  if possible (if the allocation falls within the operating spectrum). To detect network impairments due to amplifier problems, the receiver  18  may be configured to measure the energy levels at allocations that correspond to the second and third harmonic components, or other harmonics, during t 1  and t 2 . (The harmonic components being monitored may be dependent on the selected frequency bins.) If the transmitter  12  decides to use two frequency bins (f 1 ,f 2  such that f 2 &gt;f 1 ), then the receiver  18  may be configured to measure the energy in some or all of the allocations  24  shown in  FIG. 2  if possible (if the allocation falls within the operating spectrum). If the signal energy in the t 2  symbol slots are measured to be higher than the signal energy in the t 1  symbol slots, then this may be an indication that the amplifier  18  is causing signal distortion and generating second and third order harmonics (e.g., composite triple beat and composite second order distortions). 
       FIG. 3  schematically illustrates a diagram  26  for detecting non-linear performance of the device  18  in accordance with one non-limiting aspect of the present invention. The diagram  26  illustrates the controller  20  selecting two frequency bands f 1  and f 1  and two symbol slots t 1  and t 2  to facilitate transmission of a first null  30  and a second null  32  and a first pilot  34  and a second pilot  36 . The first and second nulls  30 ,  32  may correspond with the transmitter  12  transmitting a pilot with essentially no energy during a time associated with t 1  for frequencies f 1  and f 2  and the first and second pilots  34 ,  36  may correspond with the transmitter  12  transmitting a pilot with a sufficient amount of energy, which may be selectable, during a time associated with t 2  for frequencies f 1  and f 2 . In the event the transmitter  12  is associated with a cable modem termination system (CMTS) and/or a cable modem (CM), the first and second nulls  30 ,  32  and the first and second pilots  34 ,  36  may be scheduled for transmissions over the network  14  or other medium associated with the device  18 , such as in the manner described in U.S. Pat. No. 8,351,465, filed Jun. 30, 2010, and entitled System and Method of Decoupling Media Access Control (MAC) and Physical (PHY) operating layers, the disclosure of which is hereby incorporated by reference in its entirety. 
     A sample of the energy resulting from the amplifier  18  processing the first and second nulls  30 ,  32  and the first and second pilots  34 ,  36  is shown to correspond with a plurality of energies  38 ,  40 ,  42 ,  44 ,  46 ,  48 , each of the plurality of energies  38 ,  40 ,  42 ,  44 ,  46 ,  48  may be represent energy within the amplifier processed signaling. The energy may represented random noise associated within the first and second nulls  30 ,  32 . Also the energy may represent higher order harmonics associated with the corresponding first and second pilots  34 ,  36 . A first energy (E 1 , 1 )  38  is shown to represent energy within a second order harmonic for time t 1 , a second energy (E 1 , 2 )  40  is shown to represent energy within a second order harmonic for time t 1  and a third energy (E 1 , 3 )  42  is shown represent energy within a second order harmonic for time t 1 . In this manner, any energy present in the higher order harmonics of the nulls  30 ,  32  may be determined by measuring the corresponding harmonic. A fourth energy (E 2 , 1 )  44 , a fifth energy (E 2 , 2 )  46  and a sixth energy (E 2 , 3 )  48  for time t 2  may be measured to represent any energy within the corresponding harmonics of the first and second pilots  34 ,  36 . While measurement of harmonics is shown for each of the first and second times t 1 , t 2 , additional harmonics may be similarly measured at a corresponding frequency in order to identify mixing occurring at other higher order harmonics. 
     The controller  20  may be configured in accordance with the present invention to analyze the energies for the purposes of identifying performance of the amplifier  18  or other device under test. In the event the amplifier  18  is configured to linearly operate, the energies found within any of the higher order harmonics (e.g., second, third, fourth, etc.) should be essentially zero. In other words, the first energy  38  should equal the fourth energy  44 , the second energy  40  should equal the fifth energy  46 , and the third energy  42  should equal the sixth energy  48  if the amplifier is operating properly (residual or other energy may still be present in the harmonics even when operating properly due to interference or other signaling leakage such that the energies may not be zero). The controller  20  may calculate a difference in each of the energies  38 ,  40 ,  42 ,  44 ,  46 ,  48  and analyze that difference to predict and/or identify non-linear performance of the amplifier  18  in order to compensate for leakage or other interferences preventing a zero energy determination. This may be accomplished by determining a difference between the first and fourth energy  38 ,  44 , the second and fifth energy  40 ,  46  and the third and sixth energy  42 ,  48  If any one of the corresponding differences are greater than a threshold, the amplifier  18  may be determined to be performing non-linearly. The threshold may be set to a value greater than zero in order to enable the presence of interference, leakage or other acceptable energies within the measurements. 
     The difference values may also be analyzed to determine or predict future behavior and performance of the amplifier  18 . The illustrated energy measurements  38 ,  40 ,  42 ,  44 ,  46 ,  48  may be repeated for additional times/minislot (optionally including both nulls and pilots and/or multiple pilots occurring after a single or benchmarked null) with the same frequency parameters so as to measure performance of the amplifier  18  over time. A graph or trend made be developed based on the differences measured over time in order to gauge whether the differences are steady, increasing, decreasing, etc. over time. In the event the differences are increasing, it may be assumed that amplifier performance is degrading. A useful life of the amplifier  18  may be known or estimated such that the trend may be utilized to predict a percentage of life remaining in the amplifier prior to failure or non-linear performance, e.g., if the differences are 50% more than when the amplifier  18  was originally deployed, then it may be assumed that the amplifier  18  has 50% of its useful life remaining. The difference values may also be analyzed to determine a harmonic most responsible for the determined non-linear performance or predicted non-linear performance. This dominant harmonic may correspond with the one of the higher order harmonics associated with the greatest difference, i.e., the one of the higher order harmonics exhibiting the greatest difference between time t 1  and time t 2  or over some other interval of time. 
     The controller  20  may be configured to facilitate directing the transmitter  12  to test multiple devices  18  with the use of opportunistically selected nulls and pilots being unicasted or otherwise targeted to particular devices  18 , optionally by way of directing signals to an associated receiver  16 , and/or being multicasted or otherwise targeted to multiple devices  16  simultaneously. The controller  20  may include capabilities to determine the energy measurement for each device  18  in response to the opportunistic nulls and pilots from an associated receiver  16 , and in the event energy measurements cannot be ascertained from one of the receivers  16 , a sensor or other means may be used to measure the processed signaling. By comparing the results from various receivers, and identifying which ones are observing distortions in the network  14  and which are not, the location of the network element  18  that is causing distortion can be identified. In DOCSIS 3.1 or wired systems, the knowledge of the geographical locations of various CMs may be used to provide accurate pinpointing to which amplifier  18  is causing the distortion. For LTE/LTE-A systems, the ability to identify performance for individual devices  18  may be beneficial with dense, small cell/femto cell/picocell/DAS deployments, as this will enable the operator to track and check performance of the RF front ends without the need to have a technician check every cell site  18  manually. 
       FIG. 4  illustrates a flowchart  50  of a method for identifying device performance in accordance with one non-limiting aspect of the present invention. The method is described with respect to a controller being configured to facilitating instructing a transmitter to opportunistically transmit nulls and pilots to a receiver in order to identify performance of one or more devices positioned therebetween. The method is described for exemplary non-limiting purposes with respect identifying non-linear performance, such as in accordance with the above described Taylor series where non-linear performance may be identified when higher order harmonics are recognized. The non-linear performance may be assumed in the event higher order harmonic energies for a pilot exceed a corresponding null or other non-energy marker. The use of opportunistic nulls and pilots may be particularly beneficial with devices operating according to a transmission schedule having the capabilities to selectively transmit nulls and pilots are different frequencies and units of time. The pilots, or non-nulled portions of the test signals, may consume little bandwidth and may be selectively transmitter during periods in which their usage is unlikely to strain the capabilities of a corresponding network. 
     Block  52  relates to scheduling one or more nulls for processing with the device being tested. The nulls may correspond with selectable portions of the signaling being processed by the device, such as at the above-identified frequencies f 1  and f 2  for time t 1 , being transmitted with no energy. Block  54  relates to scheduling one or more pilots for processing with the device being tested. The pilots may correspond with selectable portions of the signaling being processed by the device, such as at the above-identified frequencies f 1  and f 2  for time t 2 , being transmitted with at least some measurable energy. Block  56  relates to determining energies generated with the device in response to the signaling at particular frequencies for the time periods associated with the nulls and pilots, e.g., time t 1  and t 2 . While any frequency may be measured, the frequencies associated with the higher order harmonics, i.e., the harmonics of frequencies f 1  and f 2 , may be targeted in order to identify non-linear performance. Block  58  relates to identifying performance. The performance may be identified by comparing energies or other measurables to determine differences while the device processes signals during a time period having the contemplated nulls and while the device processes signaling during a time prior having the contemplated pilots, e.g., determining non-linearity if a sufficient difference in energy exists for one or more of the higher order harmonics when comparing nulled signaling to non-nulled signaling. 
     While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.