Aircraft data link network routing

BACKGROUND

0001Flight phase measurements are already in common use in aircraft communication. A specific flight phase is often used to trigger certain communications messages. For example, many aircraft maintenance systems send their reports over an air-ground data link network when an aircraft is on final approach or immediately after touch-down. In addition, air-ground data links send information between an aircraft and air traffic control services when the aircraft is too far from an air traffic control tower to make voice radio communication and radar possible. For example, aircraft data link systems are used for long-distance flights operating over any substantial land and water routes.

0002Recurring costs of aircraft air-ground data link messages are significant. For example, message delivery rates (that is, upload and download speeds) vary considerably during certain flight phases between network service providers, the aircraft's location, and any applicable air-ground networks and sub-networks within the vicinity of the aircraft. Since connection rates for a specific air-ground network (sub-network) vary by service provider, any incremental improvement in network routing of the aircraft data links between various endpoints represents substantial cost benefits.

0003For the reasons stated above and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for improvements in aircraft data link network routing.

SUMMARY

0004The following specification discusses aircraft data link network routing in an avionics communications system. This summary is made by way of example and not by way of limitation. It is merely provided to aid the reader in understanding some aspects of one or more embodiments described in the following specification.

0005Particularly, in one embodiment, a method for routing aircraft data link messages over a plurality of communications networks is provided. The method assigns at least one data link message routing service for an aircraft having a first message processing application based on prescribed criteria, the prescribed criteria comprising preferred networks of the plurality of communications networks. As a first preferred communications network becomes available, the method selects a first message route from the assigned routing service and transmits each of the data link messages on the first message route while the first message route satisfies the prescribed criteria. When the prescribed criteria changes over a plurality of flight phases of the aircraft, the method reassigns the at least one data link message route to continue data link message transmissions to and from the aircraft based on the latest prescribed criteria.

DRAWINGS

0006These and other features, aspects, and advantages are better understood with regard to the following description, appended claims, and accompanying drawings where:

0007<figref idref="f0001">FIG. 1</figref> is a block diagram of an avionics communications system;

0008<figref idref="f0002">FIG. 2</figref> is a block diagram of an embodiment of a message routing portion of an avionics communications system;

0009<figref idref="f0003">FIG. 3</figref> is a block diagram of an embodiment of a network selection and management portion of an avionics communications system;

0010<figref idref="f0004">FIG. 4</figref> is a flow diagram illustrating an embodiment of a method for aircraft data link network routing; and

0011<figref idref="f0005">FIG. 5</figref> is a flow diagram illustrating an embodiment of a method for network selection and management in an avionics communications system.

0012The various described features are drawn to emphasize features relevant to the embodiments disclosed. Reference characters denote like elements throughout the figures and text of the specification.

DETAILED DESCRIPTION

0013Embodiments of the present invention describe aircraft data link network routing over various service provider networks through an aircraft communications management unit (CMU). In at least one embodiment, a plurality of wireless networks covering local, metropolitan and wide-area (collectively, of global or continental scales) are used based on an expanded set of programmable message routing rules to select the appropriate network(s) at any given time. The network routing discussed here provides appropriate data link services based on network availability and application needs to various aircraft data link applications. Moreover, message routing and network selections are based on current aircraft states and flight phases.

0014As discussed in further detail below, the message routing and network selection rules are separate from specific networking protocol interfaces. The programmable rules can be customized to meet individual customer requirements of (for example) commercial airlines or aircraft manufacturers, as further described below. In addition, the network routing discussed here provides an application framework that is independent of any present (or future) networking protocol architecture, including any bandwidth efficient (that is, non-spread spectrum) wireless communications networks, as further discussed below.

0015In one implementation, a message routing function block provides a uniform service interface to converging data link applications attempting to communicate over the plurality of wireless networks. Any specific data link application requests are analyzed and the message routing rules are defined based on network availability. A network selection and management function block monitors and selects the various wireless networks and sub-networks for the service interface of the message routing function block. The network selection and management function block analyzes various aircraft state inputs and applies the message routing and network selection rules. The network routing discussed here combines information about network availability, user preferences (as specified in the programmable message routing and network selection rules), and the various data link application requirements to select preferred communications networks for any aircraft data link message routing.

0016Examples of applicable aircraft data link processing applications suitable for use with the network routing discussed here include, but are not limited to, flight management system (FMS) database information, avionics display data downloads, aircraft engine data, electronic flight bag (EFB) data, Quick Access data, Flight Operations Quality Assurance (FOQA) data, in-flight entertainment data, Aeronautical Operational Control (AOC) data, Air Traffic Control (ATC) data, Aeronautical Telecommunications Network (ATN) data, and Aircraft Communications Addressing and Reporting System (ACARS) data.

0017<figref idref="f0001">FIG. 1</figref> is a block diagram of an avionics communications system 100. The system 100 comprises a CMU 102 having a processing unit 104. In the example embodiment of <figref idref="f0001">FIG. 1</figref>, the processing unit 104 is at least one of a programmable microprocessor, a field-programmable gate array (FPGA), a field-programmable object array (FPOA), an application-specific integrated circuit (ASIC), and a programmable logic device (PLD). Communicatively coupled to the processing unit 104 within the CMU 102 are a converged service interface 106 and a network adaptation interface 108. The converged service interface 106 serves as an on-board routing function for data link messages to (from) the message processing applications 110. In one implementation, the converged service interface 106 transfers the data link messages between the appropriate message processing applications 110. Moreover, the converged service interface 106 translates between various data types of the message processing applications 110 for a plurality of routers (discussed below with respect to <figref idref="f0002">FIG. 2</figref>) to establish connectivity between the aircraft and any requested endpoints. The network adaptation interface 108 provides network-specific adaptation functions to transmit specific application information over certain communications networks as further discussed below with respect to <figref idref="f0003">FIG. 3</figref>.

0018The system 100 further comprises message processing applications 110₁ to 110_K communicatively coupled to the CMU 102. It is understood that the system 100 is capable of accommodating any appropriate number of message processing applications 110 (for example, at least one message processing application 110) in a single system 100. As further discussed below with respect to <figref idref="f0002">FIG. 2</figref>, the message processing applications 110₁ to 110_K include, but are not limited to, an FMS, aircraft traffic services, an aircraft condition monitoring system, an EFB, and similar combinations of CMU-hosted message processing applications thereof. In addition, the system 100 comprises a plurality of network interfaces 112₁ to 112_K communicatively coupled to the CMU 102. It is understood that the system 100 is capable of accommodating any appropriate number of network interfaces 112 (for example, at least one network interface 112) in a single system 100. As further discussed below with respect to <figref idref="f0002">FIG. 2</figref>, each of the network interfaces 112₁ to 112_K are responsive to at least one wireless communications network including, but not limited to, a very high frequency (VHF) data link, a high frequency (HF) data link, a satellite communications (SATCOM) data link, a local area network (LAN) such as a Wi-Fi network, a wide area network (WAN) such as a cellular radio network, a metropolitan area network (MAN) such as a Worldwide Interoperability for Microwave Access (WiMAX) network, and similar bandwidth efficient wireless communications networks employing, among others, Orthogonal Frequency Division Multiplexing (OFDM)-based 802.11g, 802.11n, 802.16d, 802.16e networking protocols.

0019In operation, the processing unit 104 assigns at least one data link message routing service for a first message processing application 110 based on prescribed criteria (for example, from at least one set of programmable message routing rules). As a first communications network becomes available, the processing unit 104 selects a first message route on at least one of the network interfaces 112 from the assigned routing service. In one implementation, the processing unit 104 detects the available wireless communications networks from the plurality of bandwidth efficient communications networks supported by the CMU 102 that satisfy the prescribed criteria. Moreover, the processing unit 104 dynamically allocates any required bandwidth for the converged service interface 106 to support any communication endpoint requirements independent of data format and transport media for the data link network routing discussed here.

0020As instructed by the processing unit 104, the at least one network interface 112 transfers data link messages for the first message processing application 110 on the first message route that satisfies the prescribed criteria. In one implementation, the processing unit 104 activates at least one network interface 112 to transfer each of the messages according to a set of programmable network selection rules. If network availability changes over a plurality of flight phases of the aircraft, the processing unit 104 reassigns the at least one data link message route to continue data link message transmissions to and from the aircraft based on the prescribed criteria for each of the message processing applications 110. In one implementation, the processing unit 104 reassigns the first message route to select at least a second preferred network from the plurality of networks responsive to the network interfaces 112.

0021<figref idref="f0002">FIG. 2</figref> is a block diagram of a message routing portion of an avionics communications system 200, similar to the system 100 of <figref idref="f0001">FIG. 1</figref>. The message routing portion of the system shown in <figref idref="f0002">FIG. 2</figref> comprises the processing unit 104, the network adaptation interface 108, the message processing applications 110, and the network interfaces 112. The processing unit 104 further comprises a message routing function block 202 communicatively coupled to an ATN router 204, an ACARS router 206 and an Internet Protocol (IP) router 208. It is understood that additional routers for additional networking protocols are possible, and the network routing discussed here is not limited to any particular networking protocols. In at least one alternate implementation, the routers 204 to 208 form at least a portion of the processing unit 104.

0022In the example embodiment of <figref idref="f0002">FIG. 2</figref>, the message routing function block 202 is further responsive to the message processing applications 110₁ to 110₅. The message processing applications 110 comprise a flight management system 110₁, aircraft traffic services 110₂, an aircraft condition monitoring system 110₃, an electronic flight bag (EFB) 110₄, and a CMU-hosted message processing application 110₅. As discussed above with respect to <figref idref="f0001">FIG. 1</figref>, alternate message processing applications 110 are possible. The message routing function block 202 is further operable to receive a plurality of programmable message routing rules from the CMU 102. As further discussed below with respect to <figref idref="f0003">FIG. 3</figref>, the message routing rules comprise network selection based on current aircraft equipment configurations, aircraft flight phase, current aircraft position and trajectory, message priority, network availability relative to other networks, relative cost of networks at a given point in time, and the like.

0023The routers 204 to 208 are further responsive to the network interfaces 112₁ to 112₆ through a plurality of adaptation and control blocks 212₁ to 212₆ of the network adaptation interface 108 as shown in <figref idref="f0002">FIG. 2</figref>. The network interfaces 112₁ to 112₆ comprise at least one of a VHF data link radio interface 112₁, an HF data link radio interface 112₂, a SATCOM data link radio interface 112₃, a LAN interface 112₄, a WAN interface 112₅, and a MAN interface 112₆. The adaptation and control blocks 212₁ to 212₆ include a VHF data link (VDL) radio adaptation and control block 212₁, an HF data link (HDL) radio adaptation and control block 212₂, a SATCOM data link radio adaptation and control block 212₃, a LAN adaptation and control block 212₄, a WAN adaptation and control block 212₅, and a MAN adaptation and control block 212₆.

0024In operation, the messaging routing rules from the CMU 102 are analyzed by the message routing function block 202. As data link messages from the message processing applications 110 are received in the message routing function block 202, the message routing function block 202 determines which of the routers 204 to 208 will transfer the message over the applicable network interface 112. In the example embodiment of <figref idref="f0002">FIG. 2</figref>, the message routing rules from the CMU 102 are evaluated by the message routing function block 202 and each of the data link messages pass through the network adaptation interface 108 for any additional network selection adaptation functions that may be required to complete the data link transmission, as further discussed below with respect to <figref idref="f0003">FIG. 3</figref>.

0025<figref idref="f0003">FIG. 3</figref> is a block diagram of a network selection and management portion of an avionics communications system 300, similar to the system 100 of <figref idref="f0001">FIG. 1</figref>. The network selection and management portion of the system shown in <figref idref="f0003">FIG. 3</figref> comprises the processing unit 104, the network interfaces 112, and the adaptation and control blocks 212₁ to 212₆ of the network adaptation interface 108. The processing unit 104 further comprises a network selection and management function block 302 responsive to the message routing function block 202 of <figref idref="f0002">FIG. 2</figref>. In the example embodiment of <figref idref="f0003">FIG. 3</figref>, the network selection and management function block 302 is operable to receive a plurality of aircraft state inputs based on a current flight phase of an aircraft hosting the system 100, as further described below with respect to <figref idref="f0005">FIG. 5</figref>. In one implementation, the plurality of aircraft state inputs comprise aircraft flight phase, aircraft location, network access level, message priority level, and the like.

0026In operation, each of the adaptation and control blocks 212 route aircraft data link messages through a preferred network interface 112 based on the programmable message routing and network selection rules managed by the network selection and management function block 302. The network selection and management function block 302 monitors and controls the network interfaces 112 based on message routing decisions provided by the message routing function block 202 and on the aircraft state inputs received from the CMU 102. As illustrated in Tables 1 to 3 below, the network selection and management function block 302 selects the appropriate network based on the aircraft state inputs and informs the appropriate adaptation and control blocks 212₁ to 212₆ to perform the necessary additional network selection adaptation functions to complete the data link transmission through the appropriate network interfaces 112₁ to 112₆. For example, the WiMAX adaptation and control block 212₆ will format an ACARS message to be transmitted as an IP message by the WiMAX network interface 112₆.

Aircraft State Inputs

0027A partial listing of aircraft state inputs from the CMU 102, including examples, appears below with respect to Table 1. <tables id="tabl0001" num="0001"><table frame="all"><title><u style="single">Table 1 - Aircraft State Inputs</u></title><tgroup cols="2"><colspec colnum="1" colname="col1" colwidth="67mm" /><colspec colnum="2" colname="col2" colwidth="99mm" /><thead><row><entry align="center" valign="top"><b>Aircraft State Inputs</b></entry><entry align="center" valign="top"><b>Examples</b></entry></row></thead><tbody><row><entry valign="middle">Flight Phase</entry><entry>Pre-flight; Climb; Cruise; Descent; Takeoff; Approach; Go-Around and Done</entry></row><row><entry valign="middle">Flight Event</entry><entry>Out; Off; On and In (OOOI)</entry></row><row><entry valign="middle">Aircraft Position and Trajectory</entry><entry>latitude; longitude; mapping coordinates</entry></row><row><entry valign="middle">Aircraft State</entry><entry>Derived from on-board sensors, including but not limited to, strut switch/weight-on-wheels; parking brake; engine speed; engine oil pressure; air speed; ground speed; radio altimeter altitude; barometric altitude</entry></row><row><entry valign="middle">Aircraft distance from specific ground stations</entry><entry>Distance to an ACARS VDL ground station; Distance to WiMAX or Wi-Fi access points</entry></row><row><entry valign="middle">Application Network Type</entry><entry>ACARS High Availability; ATN ATC communications; IP High Availability</entry></row><row><entry valign="middle">Network Access Level and Relative Cost</entry><entry>ACARS Low Cost; ACARS Low Latency; IP Low Cost</entry></row><row><entry valign="middle">Message Priority Level</entry><entry>High, Urgent, Low</entry></row></tbody></tgroup></table></tables>

0028As provided by Table 1 above, each of the aircraft state inputs are evaluated along with the network selection rules and the programmable message routing rules to route each of the data link messages to the proper network. The routing rules are evaluated dynamically as aircraft state inputs are updated by the CMU 102. It is understood that the aircraft state inputs presented here are not meant to be an exhaustive listing and that any aircraft state input that may affect aircraft data link message routing can be used. In one implementation, the flight phase and the flight event inputs are adapted from Aeronautical Radio, Incorporated (ARINC) and ATC standards.

Programmable Message Routing and Network Selection Rules

0029A partial listing of programmable message routing rules from the CMU 102, including examples, appears below with respect to Table 2. <tables id="tabl0002" num="0002"><table frame="all"><title><u style="single">Table 2 - Programmable Message Routing Rules</u></title><tgroup cols="2"><colspec colnum="1" colname="col1" colwidth="98mm" /><colspec colnum="2" colname="col2" colwidth="68mm" /><thead><row><entry align="center" valign="top"><b>Message Routing Rules</b></entry><entry align="center" valign="top"><b>Examples</b></entry></row></thead><tbody><row valign="middle"><entry>Application 1, type 1 messages can use any ACARS or IP sub-network</entry><entry>High priority AOC messages</entry></row><row valign="middle"><entry>Application 1, type 2 messages can only use ACARS VHF or IP</entry><entry>Moderate priority AOC messages</entry></row><row valign="middle"><entry>Application 1, type 3 are held until Wi-Fi network detected</entry><entry>Low priority AOC messages</entry></row><row valign="middle"><entry>Application 2, type 1 messages use ATN network, VHF sub-network only</entry><entry>ATN ATC messages</entry></row><row valign="middle"><entry>Application 2, type 2 messages use ACARS network, VHF or SATCOM sub-networks only</entry><entry>FANS messages</entry></row><row valign="middle"><entry>Application 3, all types of messages can use ACARS or IP networks and any sub-network</entry><entry>External user of converged network service(s)</entry></row><row valign="middle"><entry>Application 4, all types of messages can use ACARS network and any ACARS sub-network</entry><entry>External ACARS application(s)</entry></row><row valign="middle"><entry>Application 5, type 1 messages can use any IP sub-network</entry><entry>High priority EFB messages</entry></row><row valign="middle"><entry>Application 5, type 2 messages can use only low cost IP sub-networks</entry><entry>Low priority EFB messages</entry></row></tbody></tgroup></table></tables>

0030As provided by Table 2 above, each of the programmable message routing rules are evaluated dynamically as aircraft state inputs are updated by the CMU 102. It is understood that the message routing rules presented here are not meant to be an exhaustive listing and that any programmable message routing rules can be used. For example, the programmable message routing rules illustrated in Table 2 apply to routing applications that implement AOC and Future Air Navigation System (FANS) messaging standards. In order to route the data link messages using programmable message routing rules described above in Table 2, the system 300 actively manages the network (protocol) stacks and sub-networks in the network selection and management function block 302. The network selection and management function block 302 uses the programmable network selection rules that are also executed dynamically as aircraft and network state changes. Examples of network selection rules are shown below with respect to Table 3. <tables id="tabl0003" num="0003"><table frame="all"><title><u style="single">Table 3 - Programmable Network Selection Rules</u></title><tgroup cols="2"><colspec colnum="1" colname="col1" colwidth="83mm" /><colspec colnum="2" colname="col2" colwidth="83mm" /><thead><row><entry align="center" valign="top"><b>Network Selection Rules</b></entry><entry align="center" valign="top"><b>Examples</b></entry></row></thead><tbody><row valign="middle"><entry>Selection based on network types supported by aircraft</entry><entry>Activate ACARS VHF sub-networks always using existing network selection rules</entry></row><row valign="middle"><entry>Selection based on current aircraft state AND other network availability</entry><entry>Activate ACARS SATCOM sub-network in (OOOI state OFF) OR (when no other ACARS sub-network is available)</entry></row><row valign="middle"><entry>Selection based on aircraft flight phase</entry><entry>Activate Wi-Fi when OOOI state is IN</entry></row><row valign="middle"><entry>Selection based on aircraft flight phase AND other network availability</entry><entry>(Activate WiMAX when flight phase IS NOT Cruise) AND (Wi-Fi is not available)</entry></row><row valign="middle"><entry>Selection based on aircraft flight phase AND other network availability</entry><entry>(Activate Cellular WAN when OOOI state is IN) AND (Wi-Fi is not available) AND (WiMAX is not available)</entry></row><row valign="middle"><entry>Selection based on aircraft flight phase</entry><entry>Deactivate WiMAX during a Cruise flight phase</entry></row><row valign="middle"><entry>Selection based on aircraft flight phase AND selection based on current aircraft position and trajectory</entry><entry>(Activate WiMAX when flight phase is Descent) AND (within 15 miles of destination airport)</entry></row><row valign="middle"><entry>Selection based on current aircraft position and trajectory</entry><entry>Activate ATN in an airspace defined by latitude/longitude region</entry></row></tbody></tgroup></table></tables>

0031It is understood that the network selection rules of Table 3 are not meant to be an exhaustive listing and that any programmable network selection rules can be used. The programmable network selection rules within the scope of user data link messages can be refined by the customer and loaded in the CMU 102 independent of software that implements the network protocols. In one implementation, each set of the programmable message routing and network selection rules form at least a portion of a customizable feature set of known aircraft communications management systems. The programmable message routing and network selection rule sets that pertain to specific air traffic services can also be loaded independently of the operational software in the CMU 102, but would be controlled by standard aircraft certification processes.

0032<figref idref="f0004">FIG. 4</figref> is a flow diagram illustrating a method 400 for routing aircraft data link messages over a plurality of wireless communications networks. The method 400 addresses providing appropriate data link services based on network availability and application needs to the various on-board aircraft message routing applications discussed above with respect to <figref idref="f0001 f0002 f0003">FIGS. 1 to 3</figref>. The method 400 routes the appropriate data link services over the plurality of wireless communications networks, including the bandwidth efficient wireless networks discussed above with respect to <figref idref="f0001 f0002 f0003">FIGS. 1 to 3</figref>.

0033The method of <figref idref="f0004">FIG. 4</figref> assigns at least one data link message routing service for an aircraft having a first message processing application based on prescribed criteria at block 402. In one implementation, the at least one data link message routing service receives instructions from a set of programmable message routing rules and a set of network selection rules (similar to the rules discussed above with respect to <figref idref="f0001 f0002 f0003">FIGS. 1 to 3</figref>) as the prescribed criteria. Moreover, the method of <figref idref="f0004">FIG. 4</figref> incorporates each set of the message routing rules and the network selection rules as functions of a CMU of the aircraft.

0034If a first (that is, a preferred) communications network is available at block 404, the method 400 selects a first message route from the assigned routing service at block 406 for the preferred network based on at least one aircraft state input. The method 400 detects available networks from the plurality of bandwidth-efficient wireless communications networks that satisfy the prescribed criteria defined in block 402. In one implementation, the method 400 translates at least one data type of the first message processing application for at least one router to establish connectivity between the aircraft and any requested endpoints using the first message route. Moveover, the method 400 uses a converged service interface to dynamically allocate any required bandwidth for at least the first message route.

0035While the preferred network is available, the method 400 transmits each of the data link messages on the first message route that satisfies the prescribed criteria at block 410. When the prescribed criteria changes over a plurality of flight phases of the aircraft (block 408), the method 400 reassigns the at least one data link message route at block 402 to least one second preferred network selected from the plurality of bandwidth-efficient wireless communications networks. The reassigned data link message route continues data link message transmissions to and from the aircraft based on the latest prescribed criteria. For example, when the preferred network changes over the plurality of flight phases of the aircraft, one or more network application interfaces are activated (deactivated) as discussed below with respect to <figref idref="f0005">FIG. 5</figref>.

0036<figref idref="f0005">FIG. 5</figref> is a flow diagram illustrating an embodiment of a method 500 for network selection and management in an avionics communications system. The method 500 manages the various network application interfaces discussed above with respect to <figref idref="f0004">FIG. 4</figref> based on network availability and application service needs (for example, current aircraft states). The method of <figref idref="f0005">FIG. 5</figref> periodically evaluates at least one aircraft state at block 502. If the at least one aircraft state has changed since a previous evaluation (block 504), each of the programmable network selection rules (for example, network selection rules 1 to N) are individually evaluated at blocks 506₁ to 506_N. Periodic monitoring of the programmable network selection rules ensures that the prescribed message routing criteria in a network selection and management function block (for example, the network selection and management function block 302) continue to be satisfied. In one implementation, a current network interface (for example, the network interfaces 112₁ to 112_K) is activated (deactivated) at blocks 508₁ to 508_N based on the programmable rule under evaluation. The method of <figref idref="f0005">FIG. 5</figref> resumes after a prescribed time period elapses at block 510.

0037The methods and techniques described herein may be implemented in a combination of digital electronic circuitry and software residing in a programmable processor (for example, a special-purpose processor, or a general-purpose processor in a computer). An apparatus embodying these techniques may include appropriate input and output devices, a programmable processor, and a storage medium tangibly embodying program instructions for execution by the programmable processor. A process embodying these techniques may be performed by a programmable processor executing a program of instructions that operates on input data and generates appropriate output data. The techniques may be implemented in one or more programs that are executable on a programmable system including at least one programmable processor coupled to receive data and instructions from (and to transmit data and instructions to) a data storage system, at least one input device, and at least one output device. Generally, a processor will receive instructions and data from at least one of a read only memory (ROM) and a random access memory (RAM).

0038Storage media suitable for tangibly embodying computer program instructions and data include all forms of non-volatile memory, and include by way of example, semiconductor memory devices; ROM and flash memory devices; magnetic disks such as internal hard disks and removable disks; magneto-optical disks; optical disks such as compact disks (CDs), digital video disks (DVDs), and other computer-readable media. Any of the foregoing may be supplemented by, or incorporated in, a specially-designed ASIC. When information is transferred or provided over a network or another communications connection (either hardwired, wireless, or a combination of hardwired or wireless) to a computer, the computer properly views the connection as a computer-readable medium. Thus, any such connection is properly termed a computer-readable medium. Combinations of the above are also included within the scope of computer-readable media.

0039This description has been presented for purposes of illustration, and is not intended to be exhaustive or limited to the embodiments disclosed. Variations and modifications may occur, which fall within the scope of the following claims.