Patent Description:
Modern aircraft typically transmit data between sensors and systems positioned about the aircraft using wired aircraft data buses, such as serial or other wired data buses. Using the data buses, data is routed between producing systems and consuming systems for operational control of the aircraft, such as for prognostics and health management, determination of air quality, detection of pathogens, or other operations of the aircraft.

Recently, to decrease the space, weight, and cost associated with wired aircraft data buses, wireless communication between aircraft systems and/or sensors has been considered. Radio Frequency spectrum in the frequency range <NUM> and <NUM> is specifically reserved for aircraft use. This spectrum is now allowed for Wireless Avionics Intra-Communications (WAIC) by the International Telecommunications Union (ITU) resolution <NUM> at the World Radio Council <NUM>. Primary allocation of the <NUM> - <NUM> spectrum is for the Radio Altimeter (RA), a flight safety critical device that determines the altitude of the aircraft above ground.

Because of high power radio altimeter signals, WAIC communications can be affected by interference with radio altimeters. Accordingly, WAIC packets can be corrupted, resulting in errors in WAIC communications.

This issue is complicated by several factors. First, there are multiple radio altimeters on an aircraft. Second, an aircraft on the ground can be in the radio frequency range of radio altimeters of other aircraft. Third, radio altimeters transmit radio signals across the entire frequency range from <NUM> to <NUM>, making it impractical to simply divide the frequency spectrum so that radio altimeters use a sub-spectrum and WAIC communications use a different sub-spectrum. Fourth, many different types of aircraft have been using radio altimeters for years, meaning that it is impractical to modify the radio altimeters of legacy aircraft to co-exist with WAIC transmissions. <CIT> relates to a wireless device network.

In one example, a method for coordinating Wireless Avionics Intra-Communications (WAIC) communications with a radio altimeter signal is provided in claim <NUM> and includes monitoring a frequency band and recording a sequence of time stamps, each time stamp of the sequence of time stamps corresponding to a time at which a strength of the radio altimeter signal exceeds a threshold signal strength in the frequency band. The method further includes calculating time stamp intervals between successive time stamps to produce a sequence of time stamp intervals, and identifying a pattern of time stamp intervals in the sequence of time stamp intervals. The method further includes coordinating the WAIC communications with the pattern of time stamp intervals to avoid interference with the radio altimeter signal.

In another example, a system for coordinating WAIC communications with a radio altimeter signal is provided in claim <NUM> and includes a WAIC transceiver and a WAIC network controller. The WAIC network controller is configured to monitor a frequency band and record a sequence of time stamps, each time stamp of the sequence of time stamps corresponding to a time at which a strength of the radio altimeter signal exceeds a threshold signal strength in the frequency band. The WAIC network controller is further configured to calculate time stamp intervals between successive time stamps to produce a sequence of time stamp intervals, identify a pattern of time stamp intervals in the sequence of time stamp intervals, and coordinate the WAIC communications with the pattern of time stamp intervals to avoid interference with the radio altimeter signal.

<FIG> is a schematic block diagram illustrating WAIC network controller <NUM>, WAIC routers 12A and 12B, WAIC transceivers 14A, 14B, 14C, 14D, 14E, 14F, <NUM>, <NUM>, and radio altimeters 16A and 16B disposed on aircraft <NUM>.

In the example of <FIG>, WAIC network controller <NUM>, which can be a general network controller configured for WAIC communications, is wired for communications with WAIC routers 12A and 12B. In the example of <FIG>, WAIC routers 12A and 12B can communicate wirelessly with WAIC transceivers 14A-<NUM>. WAIC transceivers 14A-<NUM> can communicate with WAIC network controller <NUM> via WAIC routers 12A and 12B. Although illustrated as two WAIC routers 12A and 12B, it should be understood that any number of one or more WAIC routers can be used, such as one WAIC router, two WAIC routers, or three or more WAIC routers. Although illustrated as eight WAIC transceivers 14A-<NUM>, it should be understood that any number of one or more WAIC transceivers can be used and located at various positions throughout aircraft <NUM>, such as a single WAIC transceiver or any two or more WAIC transceivers. In the example of <FIG>, radio altimeters 16A and 16B are located on the bottom of aircraft <NUM> to transmit radio signals toward the ground during flight and to determine an altitude of aircraft <NUM> based on returns of the transmitted signals. Although illustrated as two radio altimeters 16A and 16B located on the bottom of aircraft <NUM>, it should be understood that any number of one or more radio altimeters can be used and located at various positions.

As is further described below, WAIC network controller <NUM> can use WAIC transceivers 14A-<NUM> to identify patterns of time stamp intervals between time stamps corresponding to radio altimeter signals from radio altimeters 16A and 16B. WAIC network controller <NUM> can also be used, as described below, to coordinate WAIC communications with radio altimeter signals from radio altimeters 16A and 16B. WAIC network controller <NUM> can use WAIC routers 12A and 12B to send and receive data with WAIC transceivers 14A-<NUM>. WAIC transceivers 14A-<NUM> can be used, among other things, to monitor one or more frequency bands for radio altimeter signals, as described below.

Radio altimeters 16A and 16B are used to determine the altitude above ground level of aircraft <NUM>. To find the altitude above ground level of aircraft <NUM>, radio altimeters 16A and 16B emit radio signals and determine the altitude above ground based on returns of those signals. Because radio altimeters 16A and 16B are typically configured to emit signals in the <NUM> to <NUM> range (i.e., the frequency range also allocated for WAIC communications), the radio signals emitted by radio altimeters 16A and 16B can be detected by WAIC transceivers 14A-<NUM> as, e.g., interference. However, such detections can be utilized in combination with WAIC network controller <NUM> to identify timing of the interference for use in coordinating the WAIC communications to avoid the interference.

For instance, as is further described below, WAIC communications can be coordinated to avoid radio altimeter signals emitted by radio altimeters 16A and 16B, thereby reducing interference and increasing WAIC communications reliability. Coordination of WAIC communications (e.g., using WAIC network controller <NUM>), can be accomplished by adjusting the size of packets of WAIC communications and/or adjusting transmission timing of WAIC communications packets, so that WAIC communications take place in frequency bands during times that are not occupied by radio altimeter signals from radio altimeters 16A and 16B. For example, WAIC network controller <NUM> can use WAIC transceivers 14A-<NUM> to monitor one or more frequency bands for radio altimeter signals, register a time stamp in response to sensing a radio altimeter signal strength greater than a threshold, and calculate a time stamp interval between time stamps. The time stamp interval corresponds to a time during which a frequency band is not occupied by a radio altimeter signal.

Accordingly, WAIC network controller <NUM> can coordinate WAIC communications to avoid radio altimeter signals from radio altimeters 16A and 16B, thereby reducing interference between WAIC communications and radio altimeter signals. WAIC network controller <NUM>, implementing techniques of this disclosure, can therefore help to improve WAIC communications reliability.

<FIG> is a graph illustrating frequency axis <NUM> and time axis <NUM>. <FIG> also illustrates minimum frequency <NUM>, maximum frequency <NUM>, frequency band <NUM>, first altimeter sweep <NUM>, second altimeter sweep <NUM>, third altimeter sweep <NUM>, time stamps T<NUM>-T<NUM>, and time stamp intervals Δt<NUM>-Δt<NUM>. First altimeter sweep <NUM>, second altimeter sweep <NUM>, and third altimeter sweep <NUM> are respectively represented by a line, a line with long dashes, and a line with a pattern of long dashes and dots.

In the example of <FIG>, on frequency axis <NUM>, frequency increases from left to right; time axis <NUM> illustrates passage of time from top to bottom. In the example of <FIG>, minimum frequency <NUM> is <NUM> megahertz (MHz), and maximum frequency <NUM> is <NUM>. In other examples, minimum frequency <NUM> can be a frequency that is different than <NUM>, and maximum frequency <NUM> can be a frequency that is different than <NUM>.

Frequency band <NUM> is an adjustable frequency range (e.g., adaptive) and can be a subset of the frequency range between minimum frequency <NUM> and maximum frequency <NUM>. For purposes of clarity and ease of discussion, frequency band <NUM> is illustrated as a dotted line in the example of <FIG>. As is further described below in the example of <FIG>, frequency band <NUM> can be a bounded frequency range on frequency axis <NUM>. Frequency band <NUM> can have, for example, a range of <NUM>, <NUM>, or another range. Moreover, frequency band <NUM> is only an example of what can be a plurality of frequency bands, each of which can be an adjustable frequency range that is a subset of the frequency range between minimum frequency <NUM> and maximum frequency <NUM>. Accordingly, the entire frequency range between minimum frequency <NUM> and maximum frequency <NUM> can be divided into a plurality of frequency bands, each of which can have a range of, e.g., <NUM>, <NUM>, or another range.

A radio altimeter, (e.g., radio altimeters 16A and 16B of <FIG>), emits a radio signal. In the present disclosure, the one or more radio signals from the one or more radio altimeters change frequency over time between minimum frequency <NUM> and maximum frequency <NUM>. In the example of <FIG>, there are three radio altimeters, each of which emits a corresponding radio signal. The change in frequency over time of the three radio altimeter signals is represented, respectively, by first altimeter sweep <NUM>, second altimeter sweep <NUM>, and third altimeter sweep <NUM>. Although <FIG>. illustrates three altimeter sweeps, it should be understood that there can be more or fewer than three altimeter sweeps corresponding to more or fewer than three radio altimeters.

In the example of <FIG>, one or more WAIC transceivers, (e.g., WAIC transceivers 14A-<NUM> of <FIG>), have been configured by a WAIC network controller, (e.g., WAIC network controller <NUM> of <FIG>), to monitor frequency band <NUM>. The one or more WAIC transceivers monitor frequency band <NUM> for a radio altimeter signal with a signal strength that is greater than an adjustable threshold strength, such as a threshold signal strength of -<NUM> decibel-milliwatts (dBm). As is further described below, a time stamp is recorded in response to the one or more WAIC transceivers sensing a radio altimeter signal with a strength greater than a threshold strength. In the example of <FIG>. , time stamp T<NUM> is recorded in response to sensing a radio altimeter signal corresponding to first altimeter sweep <NUM> that is greater than the threshold on frequency band <NUM>. As is further described below in the example of <FIG>, time stamp T<NUM> can also be described as comprising two time stamps: time stamp T1i and time stamp T1o, which correspond, respectively, to the time at which the radio altimeter signal enters and exits frequency band <NUM>.

Furthermore, in the example of <FIG>. , a sequence of time stamps T<NUM>-T<NUM> is recorded. Each of time stamps T<NUM>-T<NUM> is recorded in response to sensing the radio altimeter signal strength greater than the threshold on frequency band <NUM>. As illustrated in <FIG>, each of the time stamps in the sequence of time stamps T<NUM>-T<NUM> can represent a time at which a radio signal corresponding to any one of first altimeter sweep <NUM>, second altimeter sweep <NUM>, or third altimeter sweep <NUM> is sensed on frequency band <NUM>. So, regardless of the source of the radio altimeter signal, each time stamp of the sequence of time stamps T<NUM>-T<NUM> corresponds to a time at which a radio altimeter signal is actively transmitting on frequency band <NUM>.

As further described below, a WAIC network controller, (e.g., WAIC network controller <NUM> of <FIG>) can calculate a time stamp interval between successive time stamps. The WAIC network controller can further be configured to calculate a plurality of time stamp intervals between successive time stamps in a sequence of time stamps, resulting in a sequence of time stamp intervals. In the example of <FIG>, time stamp interval Δt<NUM> is calculated as the difference between time stamp T<NUM> and time stamp T<NUM>. Time stamp interval Δt<NUM> therefore represents the amount of time between time stamp T<NUM> and time stamp T<NUM>.

Furthermore, in the example of <FIG>, time stamp intervals Δt<NUM>-Δt<NUM> correspond to the differences between successive time stamps in time stamp sequence T<NUM>-T<NUM>. As such, time stamp intervals Δt<NUM>-Δt<NUM> correspond to periods of time during which there is no radio altimeter signal with a strength above a threshold on frequency band <NUM>. In other words, time stamp intervals Δt<NUM>-Δt<NUM> represent times that WAIC communications can take place on frequency band <NUM> without radio altimeter signals with a strength above a threshold also using frequency band <NUM>. Time stamps T<NUM>-T<NUM> and time stamp intervals Δt<NUM>-Δt<NUM> can, in this way, be used to avoid interference from radio altimeter signals on frequency band <NUM>.

A WAIC network controller can also be configured, as further described below, to identify a pattern of time stamp intervals in a sequence of time stamp intervals. In the example of <FIG>, a pattern of time stamp intervals in time stamp interval sequence Δt<NUM>-Δt<NUM> can be identified. For instance, the WAIC network controller can identify the pattern of time stamp intervals as repeating sequences of intervals using, e.g., a depth-first or breadth-first search algorithm, a K-means clustering algorithm or another clustering algorithm, or other pattern recognition techniques. For instance, the WAIC network controller can identify a pattern of any two or more repeating time stamp intervals, such as two repeating time stamp intervals, three repeating time stamp intervals, or other numbers of repeating time stamp intervals.

In the example of <FIG>, a pattern of time stamp intervals can be identified as a repetition of time stamp intervals Δt<NUM>-Δt<NUM> and time stamp intervals Δt<NUM>-Δt<NUM>. As illustrated in <FIG>, the pattern of time stamp intervals corresponds to a pattern of radio altimeter signals on frequency band <NUM>. Accordingly, the WAIC network controller can identify a pattern of radio altimeter signals on frequency band <NUM> and identify a pattern of time stamp intervals corresponding to time between the radio altimeter signals. Furthermore, because radio altimeters are typically configured to vary (or sweep) frequencies at which they transmit the radio altimeter signal across the allocated frequency spectrum (e.g., <NUM> - <NUM>) at a constant rate, the WAIC network controller can plan WAIC communications (e.g., coordinate WAIC communications) on frequency band <NUM> by anticipating the repetition of the time stamp intervals. For instance, the WAIC network controller can anticipate the pattern as occurring indefinitely or for a fixed amount of time, thereby avoiding interference with the radio altimeter signals on frequency band <NUM>.

<FIG> is a graph illustrating a portion of the graph of <FIG> in further detail. The example of <FIG> provides a more detailed description of frequency band <NUM>, time stamps T<NUM>-T<NUM>, and time stamp intervals Δt<NUM>-Δt<NUM> of <FIG>. For purposes of clarity and ease of discussion, the numbering of elements in the example of <FIG> is similar to the numbering of elements in the example of <FIG>. Consequently, <FIG> illustrates frequency axis <NUM>, time axis <NUM>, minimum frequency <NUM>, frequency band <NUM>, first altimeter sweep <NUM>, second altimeter sweep <NUM>, third altimeter sweep <NUM>, and time stamp intervals Δt<NUM>-Δt<NUM>.

Unlike the illustration of frequency band <NUM> in <FIG>, frequency band <NUM> in <FIG> is illustrated as a frequency range on frequency axis <NUM>. As such, it is illustrated as bounded by two dotted lines, which represent the minimum and maximum of frequency band <NUM>. Frequency band <NUM> can have a range of, e.g., <NUM>, <NUM>, or any other range.

Another difference between the example of <FIG> and the example of <FIG> is the way that time stamps T<NUM>-T<NUM> are represented. Take, for example, time stamp T<NUM>. Like time stamp T<NUM>, time stamp T1i and time stamp T1o correspond to a radio altimeter signal, with a strength greater than a threshold signal strength, corresponding to radio altimeter sweep <NUM>. However, whereas time stamp T<NUM> in <FIG> generally corresponds to the time that the radio altimeter signal is sensed on frequency band <NUM>, time stamp T1i and time stamp T1o correspond, respectively, to the time that the radio altimeter signal has a frequency equal to the minimum and maximum of frequency band <NUM>. In other words, time stamp T1i corresponds to the time that the radio altimeter signal enters frequency band <NUM>, and time stamp T1o corresponds to the time that the radio altimeters signal exits frequency band <NUM>. In this way, time stamp T1i and time stamp T1o are a more detailed representation of time stamp T<NUM> of the example of <FIG>.

Likewise, each of time stamps T<NUM>-T<NUM> in the example of <FIG> are represented in more detail in the example of <FIG>. Each of time stamps T<NUM>-T<NUM> are represented as two time stamps: one that corresponds to a time that a radio altimeter sweep and a corresponding signal with a strength greater than a threshold enters frequency band <NUM>; and another that corresponds to the time that the same radio altimeter sweep and corresponding signal exits frequency band <NUM>.

Time stamp intervals Δt<NUM>-Δt<NUM> in the example of <FIG> correspond to differences between successive time stamps in time stamp sequence T<NUM>-T<NUM>, where each time stamp in time stamp sequence T<NUM>-T<NUM> is represented in more detail as comprising two time stamps. For example, time stamp interval Δt<NUM> in the example of <FIG> represents the difference between T1o and T2i. In other words, time stamp interval Δt<NUM> corresponds to the time after which the radio altimeter signal corresponding to time stamp T<NUM> has exited frequency band <NUM>, and before which the radio altimeter signal corresponding to time stamp T<NUM> has entered frequency band <NUM>. As such, time stamp interval Δt<NUM> corresponds to a time that there is no radio altimeter signal with a strength above a threshold on frequency band <NUM>.

Time stamp intervals Δt<NUM>-Δt<NUM> in the example of <FIG> can likewise be determined. Each time stamp in the sequence of time stamps T<NUM>-T<NUM> comprises two time stamps. As such, each time stamp interval in the sequence of time intervals Δt<NUM>-Δt<NUM> represents the difference between a time stamp corresponding to a time that a radio altimeter signal exits the frequency band, and the following time stamp corresponding to a time that a radio altimeter signal enters the frequency band. It should be understood that determining the sequence of time stamp intervals in this way is not limited to the example of <FIG>. As was described more generally in the example of <FIG> and as is further described below, determining a sequence of time stamp intervals for a frequency band can continue in this way until a pattern of time stamp intervals is identified.

<FIG> is a flow chart illustrating example operations for identifying a pattern of time stamp intervals. For purposes of clarity and ease of discussion, the example operations are described below within the context of the examples of <FIG> and <FIG>; however, it should be understood that the context of <FIG> also includes the more detailed description provided in the example of <FIG>.

As illustrated in <FIG>, one or more WAIC transceivers are tuned by a WAIC network controller to monitor a frequency band between a minimum frequency and a maximum frequency (Step <NUM>). For example, WAIC network controller <NUM> can tune one or more of WAIC transceivers 14A-<NUM> to monitor frequency band <NUM>, which is a sub-set of the WAIC frequencies (<NUM> - <NUM>).

It is determined whether a radio altimeter signal with a strength greater than a threshold is sensed on the frequency band that is being monitored (Step <NUM>). For instance, WAIC network controller <NUM> sets a threshold signal strength of radio altimeter signals, and determines whether a radio altimeter signal sensed by one or more WAIC transceivers is greater than the threshold signal strength. Depending on, among other considerations, the locations and specifications of the one or more WAIC transceivers, the locations and number of altimeters, the strength of altimeter signals, and the location of the aircraft, the threshold signal strength can vary. In response to determining that a radio altimeter signal with a strength greater than the threshold signal strength has not been sensed on the frequency band ("NO" branch of Step <NUM>), the one or more WAIC transceivers continue to monitor the frequency band (Step <NUM>).

In response to determining that a radio altimeter signal with a strength greater than the threshold signal strength has been sensed on the frequency band ("YES" branch of Step <NUM>), a time stamp is recorded (Step <NUM>). The time stamp corresponds to a time at which the radio altimeter signal with the strength greater than the threshold is sensed on the frequency band being monitored. As described in the example of <FIG>, two time stamps can be recorded, one corresponding to the time at which the radio altimeter signal enters the frequency band and one corresponding to the time at which the radio altimeter signal exits the frequency band. The time stamps can, for example, be recorded by WAIC network controller <NUM>, and can be stored in any way that is accessible to WAIC network controller <NUM> (e.g., in computer-readable memory of WAIC network controller <NUM>). A plurality of recorded time stamps (e.g., time stamps T<NUM>-T<NUM> of <FIG>) defines a sequence of time stamps.

A time stamp interval is calculated between successive time stamps (Step <NUM>). For example, WAIC network controller <NUM> can subtract from a time value of a given time stamp the time value of a sequentially-previous time stamp to determine the time stamp interval between the successive time stamps. In an instance where more than one time stamp interval for a frequency band has been calculated, (i.e., an instance in which three or more time stamps have been recorded for a frequency band) there can be a sequence of time stamp intervals, (e.g., time stamp intervals Δt<NUM>-Δt<NUM> of <FIG>.

It is determined whether there is a pattern of time stamp intervals in the sequence of time stamp intervals (Step <NUM>). WAIC network controller <NUM> can, for example, analyze the sequence of time stamp intervals for a pattern using, e.g., a search algorithm (e.g., a depth-first search algorithm, a breadth-first search algorithm, or other search algorithm), a clustering algorithm (e.g., a K-means clustering algorithm or other clustering algorithm), or other pattern recognition techniques. In examples where no pattern of time stamp intervals is identified in the sequence of time stamp intervals ("NO" branch of Step <NUM>), the one or more WAIC transceivers continue to monitor the frequency band (Step <NUM>). In response to identifying a pattern of time stamp intervals in the sequence of time stamp intervals ("YES" branch of Step <NUM>), the pattern of time stamp intervals can be stored (e.g., in computer-readable memory of WAIC network controller <NUM>), and it is determined whether an additional frequency band is to be monitored (Step <NUM>).

By monitoring an additional frequency band ("YES" branch of Step <NUM>), Steps <NUM>-<NUM> are repeated using the new frequency band, starting at Step <NUM>. By monitoring a plurality of additional frequency bands, i.e., taking the "YES" branch of Step <NUM> multiple times and iterating through Steps <NUM>-<NUM> multiple times, a plurality of patterns of time stamp intervals corresponding to a plurality of frequency bands can be identified. In some examples, (e.g., <FIG>), the frequency range between minimum frequency <NUM> and maximum frequency <NUM> can be analyzed by repeating Steps <NUM>-<NUM> for a plurality of frequency bands. Each frequency band can be a subset of the frequency range from minimum frequency <NUM> to maximum frequency <NUM>. Accordingly, repeating Steps <NUM>-<NUM> can result in a plurality of patterns of time stamp intervals corresponding to a plurality of frequency bands, which, together, can represent the entire frequency range from minimum frequency <NUM> to maximum frequency <NUM>.

In other examples, a plurality of patterns of time stamp intervals corresponding to a plurality of frequency bands is calculated by extrapolating from one or more patterns of time stamp intervals identified at Step <NUM>. This calculation can be done, for example, by using, among other factors, the minimum and maximum frequency of the radio altimeters signals that are being monitored, and by assuming that the number of radio altimeters is constant and the slope of the radio altimeter sweeps is constant. By doing this calculation, the frequencies of the radio altimeter signals over time, i.e., the radio altimeter sweeps, are known, and a plurality of patterns of time stamp intervals corresponding to a plurality of frequency bands can be identified.

In response to determining no additional frequency band is to be monitored ("NO" branch of Step <NUM>), WAIC communications are coordinated with the one or more patterns of time stamp intervals in order to avoid interference with radio altimeter signals (Step <NUM>). In one example, WAIC network controller <NUM> coordinates the WAIC communications to avoid the interference with the radio altimeter signals.

In the present invention, coordinating WAIC communications to avoid interference with the radio altimeter signals includes adjusting the size of one or more WAIC communication data packets. For instance, WAIC network controller <NUM> can adjust the size of the one or more WAIC communication packets such that transmission of the packets reliably occurs within time stamp intervals without occurring at times identified as corresponding to the pattern of radio altimeter signals.

In the present invention, coordinating the WAIC communications to avoid interference with the radio altimeter signals includes adjusting packet transmission timing of WAIC communications. For instance, WAIC network controller <NUM> can adjust transmission timing of one or more WAIC communications packets such that the packets are sent and received within time stamp intervals without occurring at times identified as corresponding to the pattern of radio altimeter signals.

As another example, coordinating the WAIC communications to avoid interference with the radio altimeter signals can include reordering packets based, at least in part, on packet size. For instance, WAIC network controller <NUM> can reorder packets depending on the size of the packets that are being reordered, so that packets are sent and received during time stamp intervals and thereby avoid interference with radio altimeter signals. For example, the transmission timing of a relatively small data packet and a relatively large data packet can be reordered so that transmission of the relatively small data packet can take place during a relatively small time stamp interval and the transmission of the relatively large data packet can take place during a relatively large time stamp interval.

As another example, coordinating the WAIC communications to avoid interference with the radio altimeter signals can include selecting a frequency band for WAIC communications. For instance, WAIC network controller <NUM> can select a pattern of time stamp intervals favorable to reliable WAIC communications and select the frequency band corresponding to that pattern of time stamp intervals. More specifically, WAIC network controller <NUM> can select a pattern of time stamp intervals, and the corresponding frequency band, in which there are, e.g., relatively large time stamp intervals, time stamp intervals with a relatively consistent size, or time stamp intervals that are in any other way favorable to coordinating WAIC communications with the radio altimeter signals.

As another example, coordinating the WAIC communications to avoid interference with radio altimeter signals can include changing the selected frequency band (i.e., the selected subset of frequencies) for WAIC communications. For instance, WAIC network controller <NUM> can change the frequency band for WAIC communications depending, at least in part, on the patterns of time stamp intervals corresponding to the frequency bands. In the case where WAIC communications is taking place on a frequency band with a corresponding pattern of time stamp intervals that are unfavorable to coordinating WAIC communications with radio altimeter signals, (e.g., time stamp intervals that are short and/or inconsistent), WAIC network controller <NUM> can change the frequency band for WAIC communications. WAIC network controller <NUM> can change WAIC communications to a frequency band with a corresponding pattern of time stamp intervals that is more favorable to reliable and efficient WAIC communications, e.g., a pattern with large, consistent, or in any other way favorable time stamp intervals. In this way, WAIC network controller <NUM> can, for example, change WAIC communications from one frequency band to another so that WAIC communications can, irrespective of the frequency band, take place during time stamp intervals without occurring at times corresponding to the pattern of radio altimeter signals.

In some examples, WAIC network controller <NUM> can monitor integrity of the WAIC communications and adjust the WAIC communications in response to identifying an error rate above a threshold error rate. Errors in WAIC communications can be detected e.g., by using an error detection method, such as by in a parity bit, a checksum, or a multi-bit cvclic redundancy check (CRC). A threshold for the error rate in WAIC communications can be, for example, a number of errors per unit time, a number of errors per number of packets, or any other measure of digital communications integrity. An increase in error rate can be caused by, among other reasons, the aircraft being in range of radio altimeters from other aircraft (e.g., when the aircraft is on or near the ground). In some examples, a detected increase in error rate (i.e., decrease in integrity) can be caused by a desynchronization of the WAIC communications with the one or more determined patterns of time stamp intervals.

In response to determining that WAIC communications error rate is above a threshold error rate, WAIC communications can be adjusted. WAIC communications can be adjusted by performing one or more of Steps <NUM> - <NUM>. For example, a frequency band can be monitored for radio altimeter signals to update a pattern of time stamp intervals that correspond to times during which there is no interference from radio altimeter signals. This pattern of time stamp intervals can be compared, for example, with the previous pattern of time stamp intervals for that frequency band. The amount that WAIC communications are desynchronized with the pattern of time stamp intervals can then be identified, and WAIC communications can be adjusted accordingly. In another example, updating a pattern of time stamp intervals, by performing one or more of Steps <NUM>-<NUM>, can be repeated for a plurality of frequency bands, resulting in a plurality of updated patterns of time stamp intervals. WAIC communications can therefore be coordinated with the updated plurality of patterns of time stamp intervals.

The one or more patterns of time stamp intervals are communicated to one or more WAIC routers (Step <NUM>). The one or more WAIC routers, (e.g., WAIC routers 12A and 12B of <FIG>), can be wired to, e.g., WAIC network controller <NUM>, and the one or more WAIC routers can communicate wirelessly with the one or more WAIC transceivers (e.g., WAIC transceivers 14A-<NUM>). The one or more WAIC routers can be used for communication between the WAIC network controller and the one or more WAIC transceivers. Accordingly, by communicating the one or more patterns of time stamp intervals to the one or more routers, the WAIC network controller can coordinate WAIC communications, which include the one or more WAIC transceivers, with the one or more patterns of time stamp intervals.

Claim 1:
A method for coordinating Wireless Avionics Intra-Communications (WAIC) communications with a radio altimeter signal, the method comprising:
monitoring (<NUM>) a frequency band, wherein the frequency band is an adjustable range between <NUM> and <NUM>;
recording (<NUM>) a sequence of time stamps, each time stamp of the sequence of time stamps corresponding to a time at which a strength of the radio altimeter signal exceeds a threshold signal strength in the frequency band;
calculating (<NUM>) time stamp intervals between successive time stamps in the sequence of time stamps to produce a sequence of time stamp intervals;
identifying (<NUM>) a pattern of time stamp intervals in the sequence of time stamp intervals; and
coordinating (<NUM>) the WAIC communications with the pattern of time stamp intervals to avoid interference with the radio altimeter signal; and characterized in that
coordinating the WAIC communications with the pattern of time stamp intervals to avoid the interference with the altimeter signal further comprises one or more of: adjusting a packet size of the WAIC communications; and adjusting packet transmission timing of the WAIC communications.