Patent Publication Number: US-2016241437-A1

Title: Controller for network having substantially fixed topology

Description:
CROSS REFERENCE TO RELATED PATENTS/PATENT APPLICATIONS 
     The present U.S. Utility patent application claims priority pursuant to 35 U.S.C. §120 as a continuation of U.S. Utility application Ser. No. 14/673,905, entitled “CONTROLLER FOR NETWORK HAVING SUBSTANTIALLY FIXED TOPOLOGY”, filed Mar. 31, 2015, now U.S. Pat. No. 9,331,793, which is a continuation of U.S. Utility application Ser. No. 13/674,603, entitled “FAST WAKE-UP AND LINK ACQUISITION IN REDUCED-TWISTED PAIR GIGABIT ETHERNET APPLICATIONS”, filed Nov. 12, 2012, now U.S. Pat. No. 9,001,843, which claims priority pursuant to 35 U.S.C. §119(e) to U.S. Provisional Application No. 61/720,279, entitled “FAST WAKE-UP AND LINK ACQUISITION IN REDUCED-TWISTED PAIR GIGABIT ETHERNET APPLICATIONS”, filed Oct. 30, 2012, all of which are hereby incorporated herein by reference in their entirety and made part of the present U.S. Utility patent application for all purposes. 
    
    
     BACKGROUND 
     1. Field 
     This invention relates generally to fast wake-up and link acquisition, and more particularly to fast wake-up and link acquisition in reduced-twisted pair gigabit Ethernet applications. 
     2. Related Art 
     Automotive Area Networks (AANs) allow interconnection of multiple devices via a network implemented in an automobile. AANs are similar to more traditional local area networks (LANs), but often have more stringent startup time requirements for networked devices. Many AANs are currently implemented using controller area network (CAN) buses, which are considerably slower than LANs implementing any of the various forms of Ethernet, especially LANs implementing Gigabit Ethernet. Gigabit Ethernet traditionally requires four twisted wire pairs (“twisted pairs”), which would make automotive wiring harnesses prohibitively heavy. Thus, the IEEE has established the 802.3 Reduced Twisted Pair Gigabit Ethernet PHY study group to study using fewer than four twisted pairs to implement Gigabit Ethernet in AANs. 
     Gigabit Ethernet applications require the use of auto-negotiation between PHY devices to establish communication between two devices. During the auto-negotiation process, the devices attempting to communicate with each other via the AAN will each send each other information about their capabilities so that a proper communication mode can be established. During the auto-negotiation process, the PHY of one device is selected as the master, and the PHY of the other device is selected as the slave. 
     After exiting auto-negotiation, the PHY enters a training mode. Training begins with the SLAVE silent and the MASTER at a reduced transmit power until it receives a response from the slave. PHY training is coordinated by exchanges of information using 2-level pulse amplitude modulation (PAM) signaling in “Info fields,” which are used to convey state transitions, transmit power settings, transition synchronization information, receiver status, such as signal to noise ratio (SNR), and to exchange precoder coefficients. Additionally, the link integrity can be tested at the PHY level. 
     Because of the relatively large amount of information that must be passed back and forth as part of the link acquisition process, current technology can require a link acquisition time that is prohibitively long in the context of AANs. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating an Automotive Area Network (AAN) having a substantially fixed topology and including multiple networked devices capable of fast wake-up and link acquisition according to various embodiments of the disclosure; 
         FIG. 2  is a block diagram illustrating a controller or other device connected to the AAN according to various embodiments of the present disclosure; 
         FIG. 3  is a block diagram illustrating a PHY interface module that provides a physical interface between the AAN and a controller or other device according to various embodiments of the disclosure; 
         FIG. 4  is a diagram illustrating an AAN having multiple sub-systems, any or all of which can implement fast wake-up and link acquisition on a system level basis according to various embodiments of the disclosure; 
         FIG. 5  is a flowchart illustrating a method of generating and storing factory default compensation parameters, according to various embodiments of the disclosure; and 
         FIG. 6  is a flowchart illustrating a method of waking up and acquiring a data/communications link and updating compensation parameters during operation, according to various embodiments of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     As used herein, the following terms are to be given their ordinary meaning, unless otherwise specified or apparent from the context in which the terms are used. The term “Automotive Area Network” (“AAN”), refers generally to a network such as those found in various automobiles, but can also refer to networks in vehicles other than automobiles, for example a motorcycle, a bus, an airplane, a boat or ship, or the like. AANs have a substantially fixed network topology; the arrangement of devices in an AAN does not normally change over time. Even if devices are replaced, replacement devices are usually coupled to the AAN over the same physical pathway. 
     The terms “compensation parameter,” “pre-compensation parameter,” and similar terms are used herein generally to refer to channel/link parameters used by a PHY or similar device to adjust transceiver variables to account for channel/link conditions or parameters. Thus, pre-compensation parameters can include threshold values indicating maximum or minimum parameter values, offset values used to adjust a base parameter, range values indicating an acceptable and/or unacceptable range of values, “set-to” values indicating particular values to assign values used in computations related to link wake-up and acquisition, actual/estimated channel/link performance values, or some combination of these. The terms “channel conditions,” “link conditions,” “channel parameters,” and “link parameters” include, but are not limited to, insertion loss, return loss, source clock offset, and crosstalk values measured or estimated as a function of mechanical, ingress, climactic, and environmental (“MICE”) variations. The term “channel response settings” refer generally to variables that are set according to pre-compensation parameters to satisfy a specified channel performance characteristic. 
     The terms “operating environment,” “environment,” and other similar terms, are used to refer to the general situations, conditions, and other factors that may affect a vehicle or AAN carried by a vehicle, and which can be detected or determined by any of various sensors and subsystems included in an AAN, or about which information can be provided by a driver or passenger. An operating environment can include channel and link conditions. 
     Referring first to  FIG. 1 , an automotive area network (AAN)  105  having a substantially fixed topology is illustrated and discussed according to various embodiments. In at least one embodiment, AAN  105  is implemented with Gigabit Ethernet protocols over reduced twisted-pair physical paths, and uses stored pre-compensation parameters to reduce wake up and link acquisition times. For a given PAM-4 modulation system over a CAT6A channel response, there can be significant time savings up for wake-up and link acquisition compared to an 802.3ab 1000BASE-T PHY start-up time. 
     AAN  105  includes entertainment device  110 , navigation device  120 , driver interface device  140 , safety device  170 , a communication device  160 , storage device  150 , and controller  130 . Controller  130  connects to communications bus  131 , which in turn connects to each of the endpoint devices via physical media having a fixed line length and type. Although each of the physical connections to the particular devices from controller  130  is fixed, the physical connections may be different from each other in many embodiments. For example, communications path  113  may have a different length than communication paths  123 ,  143 ,  153 ,  163 , and  173 . However, none of the individual communication paths will change in length or composition over time. For example, communications bus  131 , and each of the communications paths  113 ,  123 ,  143 ,  153 ,  163 , and  173 , can be included as part of an automotive wiring harness that uses twisted pair conductors to form communication paths. 
     In various embodiments, each of the devices includes a PHY module  112 ,  122 ,  142 ,  152 ,  162 , and  172 , respectively. These PHY modules can be used to communicate with PHY module  132  included in controller  130 . Although PHY  132  is shown as being coupled to communications bus  131 , other network configurations can be employed. For example, various gateways, routers, and other devices can be used to implement AAN  105 , such that each of the devices is connected either directly to each other, to controller  130  through a gateway or router, to a subsystem controller which is in turn connected to communications bus  131  through a fixed line length/type communication path. 
     Each of the devices in automotive area network  105  also includes a parameter memory. For example, entertainment device  110  includes parameter memory  116 ; navigation device  120  includes parameter memory  126 ; driver interface device  140  includes parameter memory  146 ; controller  130  includes parameter memory  136 ; storage device  150  includes parameter memory  156 ; communication device  160  includes parameter memory  166 ; and safety device  170  includes parameter memory  176 . Note that in various embodiments, including a parameter memory within each of the devices connected to AAN  105  allows each particular device to store default parameters to be used upon initiation of link acquisition, upon power up of the system, or when a particular device receives a wake-up command signal from controller  130  or some other device. 
     In various embodiments, the parameters stored in each of the parameter memories include pre-compensation parameters. Default pre-compensation parameters can be determined during the manufacturing process, either before or after all portions of AAN  105  are installed in a vehicle. It is anticipated that determining pre-compensation parameters in advance of installation of the wiring harness and devices into a vehicle, may result in less than optimal selection of default pre-compensation parameters, but may nevertheless, be useful in a fast-paced production environment. Furthermore, default pre-compensation parameters determined for each of the communication pathways prior to installation of the devices and communications bus  131  in a vehicle, can serve as starting points when measuring or estimating pre-compensation parameters after installation in a vehicle. Thus, estimated values for channel parameters, such as crosstalk impedance and the like, may simply serve as a starting point to increase the speed of a training process performed during the manufacturing process. 
     The channel response parameters used to obtain the pre-compensation parameters stored in the parameter memories can include, but are not limited to, insertion loss, return loss, source clock offset, crosstalk, signal-to-noise ratios, or the like. Most, if not all, of these channel parameter can be captured, measured, estimated, or otherwise determined as a function of mechanical and temperature variations. Thus, any one or more channel parameter may vary directly or indirectly with temperature, conductor length, age, vibration, and the like. The various parameters, measurements, and estimates used to establish pre-compensation parameters can also depend on location of the physical medium within a vehicle, quality of installation, material quality, and manufacturing quality of the wiring harness, connectors, shielding, connections, and the like. Even so, many of these parameters are substantially fixed for any particular communications channel once established. 
     In some embodiments, the pre-compensation parameters can be used as part of an overall control policy used to set various power and performance parameters for each of the devices. In some such embodiments, controller  130  can store information related to the parameters for each specific device connected to communications bus  131 , and send that information to each of the devices individually the first time a device is connected to AAN  105 . In this way, controller  130  can store a complete set of default pre-compensation parameters for each communication path for each device, and provide those parameters to each device. Upon receipt, each of those devices can store the parameters in its own respective parameter memory. Thus, if an entertainment device  110  fails and is replaced by another entertainment device, controller  130  can send the parameters for entertainment device  110  to the replacement entertainment device, thereby allowing the replacement entertainment device to immediately receive the benefits of having the parameters stored in its own memory. 
     In various embodiments, the pre-compensation parameters stored in parameter memories of each of the individual devices, can be used to facilitate fast wake-up and link acquisition each time a device is powered on. Thus, for example, instead of performing a full link negotiation, in which various channel parameters are set based on a training sequence performed at the conclusion of an auto negotiation process, a truncated version of a training procedure can be performed. Alternatively, a training portion of the link acquisition process can be completely bypassed, because the parameters that would normally be determined during the training process have previously been obtained, and stored in each of the devices. Even where default pre-compensation parameters are employed, however, the default pre-compensation parameters can be updated on a continuing, occasional, or periodic basis, based on current or historical measurements and estimates of channel response characteristics. 
     Referring next to  FIG. 2 , a controller/device  230  is illustrated, and will be discussed according to various embodiments of the disclosure. Controller/device  230  can be a controller that exercises control over other devices, including an AAN control module that controls an entire AAN, or only a subsystem controller that controls only a subsystem of the AAN. Controller/device  230  can also be an individual device, such as a network storage drive, connected to AAN. Controller/device  230  includes processor  234 , memory/storage  236 , and PHY module  232 . Status information  203  indicating the current operating environment of AAN  105 , including channel and link parameters, and current mechanical and temperature conditions, is received by controller/device  230 . In some embodiments, information  203  can be obtained by another network device and forwarded to controller/device  230 . Additionally or alternatively, controller/device  230  can deliver information  203  to other devices as information  205 . 
     Processor  234  includes one or more general-purpose processors, special-purpose processors, circuitry, hardware, and/or firmware and software, to implement various embodiments disclosed herein. Generally, processor  234  works in conjunction with memory/storage  236  to select appropriate pre-compensation parameters  245 , and provide those pre-compensation parameters to PHY module  232  for use in acquiring a communications link. In various embodiments, some or all of the memory/storage  236  is included as part of PHY module  232 , which can itself include a hardware or firmware processing module. Processor  234  can also be used to implement control policies, stored in control policies memory  241 . 
     Memory/storage  236  includes control policies  241 , control profiles  243 , network-based pre-compensation parameters  245 , and driver/user preferences  247 . Control policies  241  can include policies that govern, in conjunction with information  203  and other information stored in memory/storage  236 , the power state of PHY module  232  and other portions of controller/device  230 . Where multiple different groups of pre-compensation parameters are stored in memory/storage  236 , control policies  241  can also specify which pre-compensation parameters  245  to use under given mechanical, ingress, climactic, and environmental (MICE) conditions. Where multiple different control policies are stored in control policies  241 , control profiles  243  can be used to aid in selecting an appropriate control policy. In various embodiments, control policies  241  are implemented subject to driver/user preferences  247 . 
     Learning/adaptive databases  249  can include one or more databases used to record and track performance and performance estimates of one or more communication channels established using PHY module  232 . In various embodiments, MICE conditions contemporary to performance measurements and estimates are stored and linked to particular measurements and estimates. Learning/adaptive databases  249  can include measurements and estimates of a channel/link response made at different times and under various different operating environments. For example, information stored in learning/adaptive databases can represent information obtained periodically, occasionally, continually, or on an event-triggered basis. Information can be stored in learning/adaptive databases  249  as the measurements and estimates are obtained, they can be received from another device as information  203 , or they can be downloaded directly into controller/device  230 . 
     By analyzing the information in learning/adaptive databases  249 , processor  234  can determine whether links established using particular network pre-compensation parameters are optimal. In some embodiments, link acquisition parameters are considered optimal if link acquisition time is less than a threshold level, if acquired links operate at a speed above a threshold level, if a balance between power usage and link acquisition time meets a threshold requirement, or if there is no other set of pre-compensation parameters that would be likely to provide better link acquisition time, link performance, or more closely meet a power/performance balance. In instances where a given pre-compensation parameter, or set of pre-compensation parameters, is determined to be non-optimal, processor  234  can select different pre-compensation parameters for a current or subsequent communication based on past link performance information stored in learning/adaptive databases  249 . In some instances, one or more default pre-compensation parameters can be adjusted or replaced to achieve more desirable performance characteristics, even if the maximum achievable performance is determined to be less than optimal. 
     Referring next to  FIG. 3 , a PHY module  332  is illustrated and discussed according to various embodiments of the present disclosure. Although PHY module  332  is illustrated as being configured to interface with a device incorporating a backplane, PHYs that do not include backplane interface functionality can also be used to implement the techniques described herein. Furthermore, although the illustrated PHY is described as operating on non-return to zero (NRZ) data on the system side and pulse amplitude modulated (PAM) data on the device side, in other embodiments PHY can be configured to be coupled to a reduced, twisted-pair network employing PAM data encoding on the system side, consistent with various standard GbE protocols. Furthermore, although 40 Gb data rates are discussed, the techniques for using pre-compensation parameters and the general operating principles described herein can also be applied to 1 Gb or other data rates. 
     PHY  332  includes an egress path  301 , and ingress path  351 , control test module  371 , and auto negotiation and PHY configuration module (“configuration module”)  373 . In general operation, PHY  332  receives four lanes of non-return-to zero (NRZ) data, which can be clocked at 25.78 Gb/s. The four lanes of NRZ data are received at serializer/deserializer (serdes)  303 , which forms part of egress path  301 . Serdes  303  performs the serializer/deserializer functions and transmits the data, still in four-lane NRZ signaling format, to the 100G data path  305 , which includes 40 Gb attachment user interface (XLAUI) Rx PCS  306 , 100G Tx PCS  308 , FEC encoder  310 , and PAM4 Tx  312 . XLAUI Rx PCS  306  aligns, deskews, and descrambles the NRZ data, and serves as a retiming interface, which can change the number of lanes used to transmit the data, if needed. XLAUI Rx PCS  306  essentially decodes the NRZ data. 100G Tx PCS  308  inserts alignment blocks into the deskewed data for later use by a receiver in deskewing the data. The FEC encoder  310  applies forward error correction techniques to the data, and sends the data to PAM4 Tx  312 , which transcodes the FEC encoded data into the 256b/257b data blocks used by PAM4. 
     After the data has been encoded according to the PAM4 protocol, the data is sent to Tx AFE (analog front end)  307 , which can modulate the data at a rate of between about 26.5 Gbps/per lane to 27.2 Gbps/per lane and physically puts the data onto a backplane of a device. Thus, the data enters PHY  332  on the system side in an NRZ signaling format at 25.78 Gb/s, and leaves PHY  332  on the line side at between about 26.5 Gbps/per lane to 27.2 Gbps/per lane in a PAM4 format. 
     A similar procedure is performed, except in reverse, when PAM4 data is received on the line side of PHY  332  using ingress path  351  and converted to NRZ data for output on the system side of PHY  332 . PAM 4 data is received at RX AFE  357 , and sent through the 100G data path  355  for conversion to NRZ and output by serdes  353 . PAM4 RX  362  decodes the data from the PAM4 format, FEC decoder  360  uses the REC information as necessary to perform error correction functions, 100G RX PCS  358  transcodes the data from 512b/514b format to the 64b/66b format, and XLAUI TX PCS  356  adds alignment blocks to the data for later deskewing and adjusts the number of lanes as needed. 
     Control test module  371  can be used in conjunction with configuration module  373  to perform standard or modified auto-negotiation and link acquisition procedures as described herein. For example, memory  381  can be used to store control profile  383  and link parameters/info  385 . The link parameters include pre-compensation parameters, which can used in place of some or all parameters that conventional PHYs would normally determine during a conventional link acquisition process. For example, conventional systems exchange information about state transitions, transmit power settings, transition synchronization, receiver status, and precoder coefficients during the link acquisition process. The precoder coefficients for a particular channel can be pre-stored in link parameters/information  385 , which is particularly useful in fixed network topology automotive area networks (AANs). Furthermore, pre-compensation parameters associated with particular mechanical and temperature conditions can be used to adjust precoder coefficients stored in memory  381 . If any precoder coefficients are obtained during the link acquisition process, those precoder coefficients can likewise be adjusted or replaced using the stored pre-compensation parameters. Particular pre-compensation parameters or pre-adjusted precoder coefficients can be selected based on current measured or estimated mechanical and temperature variants. 
     Referring next to  FIG. 4 , a system  400  including an automotive area network (AAN)  405  is illustrated according to various embodiments of the present disclosure. Automotive area network  405  includes entertainment systems  410 , navigation systems  420 , control system  430 , driver communication systems  440 , safety systems  450 , engine systems  460 , and other sensor systems  470 . The systems can communicate with each other, and in some cases other portions of the automobile and external systems and networks, via AAN  405 , using any of various suitable communication protocols. For example, in some embodiments each of the subsystems connected to AAN  405  are capable of communicating via communication links conforming to one or more of various standards such as: IEEE 802.3ab, which describes Gigabit Ethernet; IEEE 802.3ba, which describes 40 and 100 Gb Ethernet (GbE); IEEE 802.5, which defines token ring; IEEE 802.6, which defines Fiber Distributed Data Interface (FDDI); IEEE 802.11, which describes wireless Ethernet standards; and the like. In some embodiments, the various subsystems within AAN  405  are connected to allow direct communication between subsystems, with subsystem controllers (discussed subsequently with respect to  FIG. 3 ) handling communications within a subsystem using the same or a different protocol independent of the overall protocol used by AAN  405  for communication between subsystems. In other embodiments, subsystems and devices are connected to allow direct communication between devices or subsystems. Yet other embodiments employ various hubs, routers, gateways, or other intermediate data communication nodes to facilitate either direct or proxy type communications between devices and subsystems connected to AAN  405 . In embodiments employing hubs, routers, gateways or the like, any or all of the hubs, routers, gateways can be included as separate subsystems (not illustrated), or included in any or all of the various illustrated subsystems. 
     Each of the various systems illustrated in  FIG. 4  can provide dedicated functionality tailored to a particular purpose, or provide general functionality that can be altered based on network loading or other operational requirements. For example, entertainment system  410  can provide entertainment to passengers with the driver of the vehicle in which AAN  405  is implemented, while Navigation systems  420  can provide dedicated navigation functionality. In other embodiments, however, the display of media and navigation information can be shared between Entertainment systems  410  and Navigation systems  420 , or other systems, and resources from one system can be used by another system. Note that although not specifically illustrated, the various subsystems include network interface modules that allow the subsystems to be coupled to AAN  405 . 
     As illustrated in  FIG. 4 , entertainment system  410  can include radio  412  for receiving and presenting radio broadcasts; media players  414  for playing back stored media content; storage drives  416  for storing media to be played back; and media displays  418  for outputting media obtained from radio  412 , media players  414 , and storage drives  416 , to a driver or passenger. 
     Navigation system  420  includes global positioning system (GPS) processing  422 ; position, speed, location, and GPS sensors  424 ; storage drives  426 , for use in storing maps, favorite locations, and the like; and displays  428  for displaying maps routes or other navigation related information. 
     Driver communication systems  440  can include in-vehicle wireless interfaces  442 , which permit a driver and passengers to interface their personal communication devices, such as smart phones, wireless phones, laptops, personal digital assistants, or the like, to automotive area network  405 . In some embodiments, in-vehicle wireless interfaces  442  also enables interfacing user devices to media displays  418 , storage drives  416 , media players  414 , or radio  412  of entertainment systems  410 . Driver communication systems  440  also includes external communication interfaces  444 , which provides communications with networks external to AAN  405 , such as a mobile telecommunication network or an external hotspot established either within or outside of a vehicle implementing AAN  405 . External communication interfaces  444  can also include various plugs, cables, adapters, switches, or the like, used to facilitate hardwired connection of driver or passenger devices to automotive area network  405   
     Driver communication systems  440  also includes driver input/output modules  448 , which can include microphones to permit a driver or passenger to issue verbal commands to one or more devices, buttons, switches, knobs, or various user selectable objects presented on graphical user interfaces, displayed via media displays  418  included in entertainment systems  410 , displays  428  included in navigation systems  420 , or displays, keypad, and the like otherwise available via AAN  405 . Driver communication systems  440  also include driver notification/displays  446 , which can be used in place of, or in addition to, the various other displays, inputs, and outputs available via AAN  405 . 
     Safety systems  450  include safety sensors  452 , which can include airbag sensors, speed sensors, accelerometers, positional sensors and backup cameras, or the like. Driver notification module  454 , also included in safety systems  450 , can used in place of, or in addition to, other notification devices and modules included in other subsystems. Safety systems  450  also include various actuated devices  458 , such as airbags, and controllers  456 , such as traction control systems, adaptive steering and headlamps, cruise control, or the like. 
     Engine systems  460  can include operational sensors  462 , such as oxygen sensors fuel sensors voltage sensors and other sensors known to those of skill in the automotive parts. Driver notification devices or modules  464  can include various lights, gages or other similar devices, and may use displays in other subsystems, for example navigation  420  displays  428 , and entertainment systems  410  media displays  418 , to provide notifications to vehicle occupants. Controllers  466  can include control modules used to control various engine functions, and can include a microcontroller designed to adjust engine functionality based on information provided by various sensors and vehicle subsystems. Communication module  468  can include various receivers, transmitters, communication paths, amplifiers, buffers, or the like used to facilitate communication between engine systems  460  and automotive area network  405 . 
     Other sensors and systems  470  can include various sensors, switches, and measurement devices, for example door open/close sensors, thermostats, thermometers, resistance or conductivity sensors used to detect the failure of a headlamp, overhead light, or other illumination device, current sensors, voltage sensors, tire pressure sensors, light sensors used to activate headlights during periods of low light, and so on. Note that many of the other sensors/systems  470  can also be included in operational sensors  462 . 
     Control system  430  can include network interface modules  432 , one or more processors  434 , memory/storage  436 , and control policy module  438 . In various embodiments, control system  430  operates to implement a control policy for AAN  405 , in which a balance between performance and power usage is established for each device individually, for each subsystem individually, for devices within each subsystem as an aggregate, and/or for all subsystems as a whole. 
     Control policy module  438  can be used to select and implement a control policy based on a number of factors including link acquisition speed thresholds, the current operating environment of the vehicle, an operating history of the vehicle, an environmental history, a performance or power usage history of AAN  405 , data types, data usage, user preferences, the type of traffic being carried within any or all particular subsystems of AAN  405 , response time requirements for particular devices, or the like. Memory/storage  436  can be used to store a history of the vehicle operation, one or more control policies, pre-compensation parameters, sensor information, driver and passenger preferences, factory defaults, network configurations, and other information that can be used to allow control policy module  438  to select and implement one or more control policies based on the current conditions or operating environment of AAN  405 . 
     Network interface modules  432  can include one or more modules used to communicate with the various subsystems or devices coupled to automotive area network  405 . In some embodiments, a control policy may dictate that a standby or low power state includes a state in which the frequency and type of communications with a particular device or subsystem are limited by turning on PHY circuitry of a communications module only periodically. In other embodiments, a low power state allows power-up of the PHY, but prevents power up of some or all of the higher-level circuitry of the device. When leaving a low power state, a PHY can acquire a link using pre-compensation parameters provided by control system  430  during a previous communication session. In some embodiments, each device can include at least a part of a control policy designated as a default control policy, and boots to the power state specified by the default control policy, using pre-compensation parameters previously stored in the device. 
     Control policy module  438  can both select and implement control policies using control processor  434  and/or circuitry included in control policy module  438 . Thus, for example, if control system  430  receives information from a subsystem of AAN  405 , e.g. from an operational sensor  462  included in engine systems  460  subsystem, control policy module  438  can select a different control policy than it would select under different environmental conditions as indicated by operational sensor  462 . 
     Referring next to  FIG. 5 , a method  500  illustrating a training process which can be used during a vehicle manufacturing process to determine default compensation parameters to be stored in a device connected to automotive area network (“AAN”), according to various embodiments of the disclosure. At block  503  initial, or default, pre-compensation parameters and control policies, which can be used to facilitate improved wake up and link acquisition times, are loaded into a device. Initial pre-compensation parameters can be selected, in some cases, based on manufacturing information associated with cables, wiring harnesses, or the like used to construct an AAN. For example, initial pre-compensation parameters, to be used for establishing base precoder coefficients for use in a link acquisition process, can be established for an AAN based upon the model number of a wiring harness. Thus, each device to be connected to a wiring harness associated with a particular AAN can be stored into each of the devices as a default pre-compensation parameter to use for the initial link acquisition training process performed when the device attempts to establish a communication link for the first time after being connected to the AAN at block  505 . 
     At block,  507  operating variables are determined. Operating variables can be determined by receiving information at the device from other devices or subsystems of the AAN, or based on information pre-stored in the device. These operating variables can include temperature, humidity, vibration, or the like. 
     At block  509 , upon establishing a communications link, the time needed to establish communication with another device on the AAN can be measured, or estimated based on measurements, as well as various link or channel performance parameters. These link or channel performance parameters can include, but are not limited to, insertion loss, return loss, source clock offset, cross talk, and the like. In many instances, the training communications link is established with a controller, bridge, gateway, router, switch, or the like. 
     At block  511 , a determination is made about whether the startup time and link acquisition performance measured or estimated during the initial link acquisition process meets performance criteria using the default parameters. If not method  500  proceeds to block  515 , where updated compensation parameters or control policies are selected and then to block  517  where the updated compensation parameters and control policies are stored into the device for use during subsequent link acquisition events. In some embodiments, the compensation parameters are immediately adjusted, and additional measurements are made using the newly updated parameters. 
     If the link acquisition time and other link performance parameters measured at block  509  meet specified thresholds were criteria for acceptable or optimal performance, method  500  proceeds to block  513 , where the default compensation parameters currently stored in a device at block  503  are left unchanged. By leaving the default, station parameters unchanged, the same default pre-compensation parameters used in establishing a communications link previously will be used again the next time the device being configured is powered up and needs to acquire a communications link. 
     Referring next to  FIG. 6 , a method  600  illustrating waking up and acquiring a data/communications link and updating compensation parameters during operation, will be discussed according to various embodiments of the present disclosure. At block  603 , a device connected to the automotive area network (“AAN”) receives a wake-up command via the AAN. In some embodiments, this wake-up command includes an implementation delay, such that the device is instructed to wake-up the communication channel after a predetermined delay. In other embodiments, waking up communication channel, illustrated by block  603 , can be performed at vehicle power up, device power up, upon changing from a low-power state to fully active state, or the like. 
     At block  605 , the default operating parameters are obtained by the device. The default operating parameters are, in at least one embodiment, the same parameters established during the initial and initial training process, and can be obtained from memory local to the device. In other embodiments, the default operating parameters can be obtained from various other sources, including user input databases, or the like. The default operating parameters generally specify pre-compensation parameters that can be used to adjust the signal processing performed by the device while establishing a link. 
     As illustrated by block  607 , the operating conditions of the AAN are determined. Part of determining the operating conditions at block  607  can include, in some embodiments, selecting certain of the default operating parameters based on a control policy or otherwise. Determining operating conditions at block  607  can also include adjusting the default operating parameters to account for various mechanical ingress, climactic, and environmental (MICE) variations. 
     After determining the operating conditions at block  607 , a communication channel is established at block  609  between the device and another device on the AAN. In at least some embodiments, the device on the AAN with which communications are to be established is a network controller or subsystem controller. However, in other embodiments, communications can be established with any other authorized device on the AAN. For example, if the device in question is a network storage device, the communications between network storage devices can be established with a media player requesting access to information stored on a network storage device. 
     At block  613  after the communications channel is established, link performance metrics can be obtained, and associated with the current operating parameters used in establishing the communications channel or link. Obtaining a link performance metrics can include measuring or estimating various channel characteristics. In at least one embodiment, the current performance metrics are associated with both the operating conditions and the default operating parameters, to help establish a relationship between operating conditions, parameters, and link performance. 
     At block  615 , a check is made to determine whether the link/channel performance metrics meet threshold specified by a control policy, preset factory thresholds, user defined thresholds, or the like. If it is determined at block  615  that the link performance is acceptable, or optimal, depending on the threshold specified by the control policy, method  600  proceeds to block  619  were a record is made of the parameters, the control policy, the performance, and operating conditions. By reporting this information, and associating each of the separate pieces of information with each other, a history can be developed. This history can be used to help set default operating parameters under similar conditions in the future, or in some cases to alter the default operating parameters. After the information is recorded at block  619 , a check is made at block  625  to determine whether the communications over the link established have been completed, and if they have been completed, the method  600  proceeds to end. However, if the communications are not completed the link or channel can be continuously monitored by returning to block  613 . Monitored variations in the overall channel response include, but are not limited to, frequency drift, and return loss variation as a function of temperature. 
     If it is determined at block  615  that performance criteria for the link or channel are not satisfying the required threshold performance metrics, updated compensation parameters and/or control policies are selected at block  621 . These updated compensation parameters and control policies can be chosen based on previous link performance under particular conditions. Thus, if link or channel performance is not satisfactory, a performance history can be checked to identify compensation parameters in control policies that may be better suited to the operating conditions identified at block  607 . 
     After determining and selecting updated compensation parameters or control policies the updated parameters and control policies can be applied and stored, as illustrated by block  623 . After applying and storing the updated compensation parameters, method  600  returns to block  613 , where channel/link performance metrics for the current parameters are determined. 
     As may be used herein, the terms “substantially” and “approximately” provides an industry-accepted tolerance for its corresponding term and/or relativity between items. Such an industry-accepted tolerance ranges from less than one percent to fifty percent and corresponds to, but is not limited to, component values, integrated circuit process variations, temperature variations, rise and fall times, and/or thermal noise. Such relativity between items ranges from a difference of a few percent to magnitude differences. As may also be used herein, the term(s) “operably coupled to”, “coupled to”, and/or “coupling” includes direct coupling between items and/or indirect coupling between items via an intervening item (e.g., an item includes, but is not limited to, a component, an element, a circuit, and/or a module) where, for indirect coupling, the intervening item does not modify the information of a signal but may adjust its current level, voltage level, and/or power level. As may further be used herein, inferred coupling (i.e., where one element is coupled to another element by inference) includes direct and indirect coupling between two items in the same manner as “coupled to”. As may even further be used herein, the term “operable to” or “operably coupled to” indicates that an item includes one or more of power connections, input(s), output(s), etc., to perform, when activated, one or more its corresponding functions and may further include inferred coupling to one or more other items. As may still further be used herein, the term “associated with”, includes direct and/or indirect coupling of separate items and/or one item being embedded within another item. As may be used herein, the term “compares favorably”, indicates that a comparison between two or more items, signals, etc., provides a desired relationship. For example, when the desired relationship is that signal  1  has a greater magnitude than signal  2 , a favorable comparison may be achieved when the magnitude of signal  1  is greater than that of signal  2  or when the magnitude of signal  2  is less than that of signal  1 . 
     As may also be used herein, the terms “processing module”, “module”, “processing circuit”, and/or “processing unit” may be a single processing device or a plurality of processing devices. Such a processing device may be a microprocessor, micro-controller, digital signal processor, microcomputer, central processing unit, field programmable gate array, programmable logic device, state machine, logic circuitry, analog circuitry, digital circuitry, and/or any device that manipulates signals (analog and/or digital) based on hard coding of the circuitry and/or operational instructions. The processing module, module, processing circuit, and/or processing unit may have an associated memory and/or an integrated memory element, which may be a single memory device, a plurality of memory devices, and/or embedded circuitry of the processing module, module, processing circuit, and/or processing unit. Such a memory device may be a read-only memory, random access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, cache memory, and/or any device that stores digital information. Note that if the processing module, module, processing circuit, and/or processing unit includes more than one processing device, the processing devices may be centrally located (e.g., directly coupled together via a wired and/or wireless bus structure) or may be distributedly located (e.g., cloud computing via indirect coupling via a local area network and/or a wide area network). Further note that if the processing module, module, processing circuit, and/or processing unit implements one or more of its functions via a state machine, analog circuitry, digital circuitry, and/or logic circuitry, the memory and/or memory element storing the corresponding operational instructions may be embedded within, or external to, the circuitry comprising the state machine, analog circuitry, digital circuitry, and/or logic circuitry. Still further note that, the memory element may store, and the processing module, module, processing circuit, and/or processing unit executes, hard coded and/or operational instructions corresponding to at least some of the steps and/or functions illustrated in one or more of the FIGS. Such a memory device or memory element can be included in an article of manufacture. 
     The present disclosure has been described above with the aid of method steps illustrating the performance of specified functions and relationships thereof. The boundaries and sequence of these functional building blocks and method steps have been arbitrarily defined herein for convenience of description. Alternate boundaries and sequences can be defined so long as the specified functions and relationships are appropriately performed. Any such alternate boundaries or sequences are thus within the scope and spirit of the claimed invention. Further, the boundaries of these functional building blocks have been arbitrarily defined for convenience of description. Alternate boundaries could be defined as long as the certain significant functions are appropriately performed. Similarly, flow diagram blocks may also have been arbitrarily defined herein to illustrate certain significant functionality. To the extent used, the flow diagram block boundaries and sequence could have been defined otherwise and still perform the certain significant functionality. Such alternate definitions of both functional building blocks and flow diagram blocks and sequences are thus within the scope and spirit of the claimed invention. One of average skill in the art will also recognize that the functional building blocks, and other illustrative blocks, modules and components herein, can be implemented as illustrated or by discrete components, application specific integrated circuits, processors executing appropriate software and the like or any combination thereof. 
     The present disclosure may have also been described, at least in part, in terms of one or more embodiments. An embodiment of the present invention is used herein to illustrate the present invention, an aspect thereof, a feature thereof, a concept thereof, and/or an example thereof. A physical embodiment of an apparatus, an article of manufacture, a machine, and/or of a process that embodies the present invention may include one or more of the aspects, features, concepts, examples, etc. described with reference to one or more of the embodiments discussed herein. Further, from figure to figure, the embodiments may incorporate the same or similarly named functions, steps, modules, etc. that may use the same or different reference numbers and, as such, the functions, steps, modules, etc. may be the same or similar functions, steps, modules, etc. or different ones. 
     Unless specifically stated to the contra, signals to, from, and/or between elements in a figure of any of the figures presented herein may be analog or digital, continuous time or discrete time, and single-ended or differential. For instance, if a signal path is shown as a single-ended path, it also represents a differential signal path. Similarly, if a signal path is shown as a differential path, it also represents a single-ended signal path. While one or more particular architectures are described herein, other architectures can likewise be implemented that use one or more data buses not expressly shown, direct connectivity between elements, and/or indirect coupling between other elements as recognized by one of average skill in the art. 
     The term “module” is used in the description of the various embodiments of the present invention. A module includes a functional block that is implemented via hardware to perform one or module functions such as the processing of one or more input signals to produce one or more output signals. The hardware that implements the module may itself operate in conjunction software, and/or firmware. As used herein, a module may contain one or more sub-modules that themselves are modules. 
     While particular combinations of various functions and features of the present invention have been expressly described herein, other combinations of these features and functions are likewise possible. The present invention is not limited by the particular examples disclosed herein and expressly incorporates these other combinations.