Patent Publication Number: US-7904082-B2

Title: ACARS messages over iridium

Description:
This application is a divisional of U.S. patent application Ser. No. 11/767,128, filed in the U.S. Patent and Trademark Office on Jun. 22, 2007, which is a continuation-in-part of U.S. patent application Ser. No. 10/642,627, filed in the U.S. Patent and Trademark Office on Aug. 19, 2003, which claims the benefit of U.S. Provisional Application No. 60/404,388, filed in the U.S. Patent and Trademark Office on Aug. 20, 2002. The contents of U.S. patent application Ser. Nos. 10/642,627, 11/767,128 and U.S. Provisional Application No. 60/404,388 are incorporated by reference herein in their entireties. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to transmission of messages through the Iridium Short Burst Data Service. More specifically, this invention relates to transmission of ground to-air and air-to ground messages, conforming to Airlines Electronics Engineering Committee Specification 618, through the Iridium Short Burst Data Service. 
     2. Description of Related Art 
     Aircraft Communication Addressing and Reporting System (ACARS) is a well-known data protocol defined by Airlines Electronic Engineering Committee (AEEC) Specification 618. ACARS provides connectivity for character-based data between an aircraft and one or more ground-based service providers. 
     VHF communication provides only line-of-sight communication coverage while satellite communication provides oceanic and polar communication coverage. However, satellite communication has been expensive for use with ACARS. The Iridium Short Burst Data Service is a lower cost alternative to conventional satellite communication. The Iridium Short Burst Data Service is designed, such that small data messages or frequently transmitted data messages may be sent more economically compared with transmitting the messages via circuit switched data services. 
     Equipment on board commercial aircraft adhere to AEEC specifications. Systems have been developed which provide ACARS-like messages sent through the Iridium satellite network. However, these systems do not support ACARS air/ground protocol and therefore, the ACARS-like messages cannot be passed to existing avionic equipment aboard an aircraft. 
     The ACARS air/ground protocol provides for transmission of messages in pieces called blocks. According to the protocol, receipt of each block is acknowledged. Elements of the message blocks may convey information to the avionic equipment, such as, for example, peripheral addressing information or other information. The systems, which provide ACARS-like messages, do not provide the information conveyed by the elements of the message blocks to the avionic equipment. Commercial airlines, using the systems which provide ACARS-like messages, are incapable of conveying the information from the elements of the message blocks to the avionics equipment without either revamping or replacing the existing avionics equipment. However, such revamping or replacing of the existing avionics equipment may cause the equipment to no longer comply with AEEC specification 618. 
     SUMMARY 
     This Summary is provided to introduce a selection of concepts in a simplified form that is further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. 
     A system and a method are provided for sending and receiving messages, conforming to Airlines Electronic Engineering Committee (AEEC) Specification 618, between a point located on the ground and a point located on an aircraft. In one embodiment, a communication device aboard an aircraft may receive an Iridium Short Burst Data message, which may include at least a portion of a message conforming to AEEC Specification 618 and an added header including an application indicator for indicating one of a number of applications to which the at least a portion of the message conforming to AEEC Specification 618 pertains. The communication device aboard the aircraft may deliver the at least a portion of the message, without the added header, to avionics equipment aboard the aircraft. 
     In a second embodiment, a communication device for use aboard an aircraft is provided. The communication device may include an L-band transceiver to receive and send Iridium Short Burst Data messages from and to a ground-based communication device, a header stripper to discard a header from a received Iridium Short Burst Data message, which may include at least a portion of a message conforming to AEEC Specification 618. The header may include an application indicator for indicating one of a number of applications to which the at least a portion of the message pertains, a message identifier for associating a group of message portions of the message conforming to the AEEC Specification 618 with a particular message, and a segment offset indicating a placement of each of the group of message portions with respect to the message conforming to the AEEC Specification 618, and a communication interface to send the message conforming to the AEEC Specification 618 to avionics equipment aboard the aircraft. 
     In a third embodiment, a ground-based communication device is provided. The ground-based communication device may include a communication interface, a header adder, and an L-band transceiver. The communication interface may be used for receiving from and sending to a ground-based processing device, messages conforming to AEEC Specification 618. The header adder may add a header to at least a portion of a message conforming to AEEC Specification 618, received from the ground-based processing device. The header may include an application indicator for indicating one of a number of applications to which the at least a portion of the message pertains, a message identifier for associating a number of message portions of the message conforming to the AEEC Specification 618, and a segment offset indicating a placement of each of the number of message portions with respect to the message conforming to the AEEC Specification 618. The L-band transceiver may send an Iridium Short Burst Data message to an aircraft-based communication device. The Iridium Short Burst Data message may include the at least a portion of the message conforming to the AEEC Specification 618 and the added header. 
    
    
     
       DRAWINGS 
       In order to describe the manner in which the above-recited and other advantages and features can be obtained, a more particular description is provided below and will be rendered by reference to specific embodiments thereof, which are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments and are not therefore to be considered to be limiting of its scope, implementations will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
         FIG. 1  illustrates an exemplary operating environment in which embodiments consistent with the subject matter of this disclosure may operate; 
         FIG. 2  is a functional block diagram that illustrates an exemplary processing device, which may be used to implement an aircraft-based communication device or a ground-based communication device consistent with the subject matter of this disclosure; 
         FIG. 3  is a functional block diagram illustrating exemplary functions which may be performed by an aircraft-based communication device or a ground-based communication device; 
         FIG. 4  illustrates an exemplary layout of a message header, which may be included in an Iridium Short Burst Data message; 
         FIG. 5  is a flowchart illustrating exemplary processing, which may be performed in an aircraft-based communication device or a ground-based communication device in an embodiment consistent with the subject matter of this disclosure; and 
         FIG. 6  is a flowchart illustrating an exemplary process, which may be performed by an aircraft-based communication device or a ground-based communication device when receiving an ACARS message. 
     
    
    
     DETAILED DESCRIPTION 
     Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The features and advantages of the invention may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other features of the present invention will become more fully apparent from the following description and appended claims, or maybe learned by the practice of the invention as set forth herein. 
     Various embodiments of the invention are discussed in detail below. While specific implementations are discussed, it should be understood that this is done for illustration purposes only. A person skilled in the relevant art will recognize that other component configurations may be used without parting from the spirit and scope of the invention. 
     The invention comprises a variety of embodiments, such as a method and processing device and other embodiments that relate to the basic concepts of the invention. Note that while this disclosure discusses aircraft and airline uses for the attention, the invention by no means is limited to that area and may be applied to a wide variety of environments and uses. 
     Overview 
     In embodiments consistent with the subject matter of this disclosure, a system and method may be provided by which messages conforming to AEEC specification 618 may be passed between one or more ground-based data providers and avionics equipment aboard an aircraft via the Iridium Short Burst Data Service. The messages may be ground-to-air or air-to-ground messages. 
     In some embodiments, the messages conforming to the AEEC specification 618 may be ACARS messages and at least some of the messages may have a length exceeding a maximum payload of the Iridium Short Burst Data Service. In such embodiments, an ACARS message exceeding the maximum payload of the Iridium Short Burst Data Service may be segmented and each of the segments may be sent via the Iridium Short Burst Data Service in separate Iridium Short Burst Data messages. When the separate Iridium Short Burst Data messages are received, the segments may be combined to reconstruct the ACARS message for delivery to an intended destination. 
     Exemplary Operating Environment 
       FIG. 1  illustrates an exemplary operating environment in which embodiments consistent with the subject matter of this disclosure may operate. The environment may include an aircraft-based system  100  and a ground-based system  105 . 
     Aircraft-based system  100  may be located on an aircraft and may include avionics equipment  104  and an aircraft-based communication device  102 . Aircraft-based communication device  102  and avionics equipment  104  may be connected via a bus  103 , which in some embodiments may include an ARINC 429 communication bus. Aircraft-based communication device  102  may receive one or more Iridium Short Burst Data messages via the Iridium Short Burst Data Service. Each of the Iridium Short Burst Data Messages may include a complete ACARS message or a portion of a segmented ACARS message. If portions of a segmented ACARS message are received by aircraft-based communication device  102 , then aircraft-based communication device  102  may combine the segmented portions of the ACARS message to reconstruct the ACARS message. Aircraft-based communication device  102  may then deliver the ACARS message to avionics equipment  104 . Avionics equipment  104  may send an ACARS acknowledgment to ground-based system  105  via bus  103 , aircraft-based communication device  102 , and the Iridium Short Burst Data Service. Further, avionics equipment  104  may provide an ACARS message to aircraft-based communication device  102  for transmission through the Iridium Short Burst Data Service to ground-based system  105 . If the ACARS message exceeds a maximum payload capacity of the Iridium Short Burst Data Service, then aircraft-based communication device  102  may segment the ACARS message into a number of portions, each of which may be transmitted to ground-based system  105  in a separate Iridium Short Burst Data message. 
     Ground-based system  105  may include data sources, such as, for example data provider  1   106 - 1 , data provider  2   106 - 2 , . . . data provider N  106 -N, a message processing device  108 , and a ground-based communication device  110 . Data providers  106  may include a number of data providers providing data such as, for example, weather data, navigation data, or other data. Message processing device  108  may receive data from one or more data providers  106 , may format the received data as a ground-to-air ACARS message and may provide the ground-to-air ACARS message to ground-based communication device  110  for transmission via the Iridium Short Burst Data Service to aircraft-based system  100 . When the ACARS message exceeds the maximum payload of the Iridium Short Burst Data Service, ground-based communication device  110  may segment the ACARS message into multiple portions and may transmit each of the multiple portions to aircraft-based system  100  in separate Iridium Short Burst Data messages. When multiple portions of an ACARS message are received by ground-based communication device  110  via the Iridium Short Burst Data Service, ground-based communication device  110  may combine the multiple portions to reconstruct the ACARS message. The ACARS message may then be provided to message processing device  108 , which may further provide an ACARS acknowledgment to ground-based communication device  110  for delivery to aircraft-based system  100  and avionics equipment  104  via the Iridium Short Burst Data Service. Message processing device  108  may then deliver the ACARS message to an intended destination, such as, for example, one of data providers  106 . 
     Exemplary Processing Device 
       FIG. 2  is a functional block diagram that illustrates an exemplary processing device  200 , which may be used to implement embodiments of aircraft-based communication device  102  or ground-based communication device  110  consistent with the subject matter of this disclosure. Processing device  200  may include a bus  210 , a processor  220 , a memory  230 , a read only memory (ROM)  240 , a transceiver  205 , and a communication interface  250 . Bus  210  may permit communication among components of processing device  200 . 
     Transceiver  205  may include one or more L-band transceivers for transmitting and receiving Iridium Short Burst Data messages via the Iridium Short Burst Data Service. Communication interface  250  may provide communications to message processing device  108 , when processing device  200  is used to implement ground-based communication device  110 , or may provide communications with avionics equipment  104 , when processing device  200  is used to implement aircraft-based communication device  102 . 
     Processor  220  may include at least one conventional processor or microprocessor that interprets and executes instructions. Memory  130  may be a random access memory (RAM) or another type of dynamic storage device that stores information and instructions for execution by processor  220 . Memory  230  may also store temporary variables or other intermediate information used during execution of instructions by processor  220 . ROM  240  may include a conventional ROM device or another type of static storage device that stores static information and instructions for processor  220 . 
     Processing device  200  may perform such functions in response to processing device  120  executing sequences of instructions contained in a tangible machine-readable medium, such as, for example, memory  130 , or other medium. Such instructions may be read into memory  130  from another machine-readable medium, such as a storage device (not shown), or from a separate device via a communication interface. 
       FIG. 3  is a functional block diagram which helps illustrate functions performed by the processing device  200  when implementing either aircraft-based communication device  102  or ground-based communication device  110 . As shown in  FIG. 3 , processing device  200  may include transceiver  205 , header stripper  304 , message combiner  306 , communication interface  250 , message segmenter  310 , and header adder  312 . 
     As mentioned previously, transceiver  205  may include one or more L-band transceivers for receiving and transmitting Iridium Short Burst Data messages via the Iridium Short Burst Data Service. Each received Iridium Short Burst Data Message may include at least a portion of an ACARS message and a message header, to be described below. That is, each received Iridium Short Burst Data message may include the message header and, either a complete ACARS message, or a segment or portion of an ACARS message. 
     Header stripper  304  may remove the above-mentioned message header, or may at least cause the message header to be discarded. Message combiner  306  may combine multiple portions or segments of a received ACARS message. Message segmenter  310  may segment an ACARS message into multiple portions or segments, each of the portions or segments to be transmitted in a separate Iridium Short Burst Data Message via the Iridium Short Burst Data Service. Header adder  312  may add the message header to an Iridium Short Burst Data message. The Iridium Short Burst Data Message may include either a complete ACARS message or a portion or segment of an ACARS message to be transmitted via the Iridium Short Burst Data Service. 
     As mentioned previously, communication interface  250  may provide communications to message processing device  108 , when processing device  200  is used to implement ground-based communication device  110 , or may provide communications with avionics equipment  104 , when processing device  200  is used to implement aircraft-based communication device  102 . 
       FIGS. 2 and 3  illustrate one exemplary embodiment in which processing device  200  may include processor  220  and memory  220 . In such an embodiment, message combiner  306 , header stripper  304 , header adder  312 , and message segmenter  310  may be included in modules as instructions for processor  220  to execute. In other embodiments, processing device  200  may be implemented via other means, such as, for example, an Application Specific Integrated Circuit (ASIC). In such embodiments, message combiner  306 , header stripper  304 , header adder  312 , and message segmenter  310  may be implemented by the ASIC. 
     Exemplary Message Header 
       FIG. 4  illustrates an exemplary message header, which may be included in an Iridium Short Burst Data message having a complete ACARS message or a portion of an ACARS message. The message header may include a segment version ID  402 , an application type  404 , a message ID  406 , a segment offset  408 , a segment total  410 , a compression indicator  412 , reserved- 1   414 , and reserved- 2   416 . 
     Segment version ID  402  may be a one byte field identifying a version of the header. A later version of the header may include more, fewer, or different fields, and a particular format of the header may be indicated by a value of segment version ID  402 . 
     Application type  404  may be a one byte field identifying an application for which the data included in the Iridium Short Burst Data message is intended. Application type  404  may indicate that the data is intended for a weather application, an e-mail application, an ACARS application, or another application. In one embodiment, an application type of 1 may indicate a weather application, an application type of 2 may indicate an e-mail application, and an application type of 3 may indicate an ACARS application. In other embodiments, other values of application type  404  may indicate other or different applications. 
     Message ID  406  may be a one byte field used to associate multiple portions, or segments, of an ACARS message. For example, an ACARS message, which is segmented and transmitted within separate Iridium Short Burst Data messages, may include a message header in each of the separate Iridium Short Burst Data messages. Each of the message headers may have a same value for message ID  406  to indicate that the segments are associated with one another (i.e., each of the segments are associated with a same ACARS message). 
     Segment offset  408  may be a one byte field used to indicate an offset of a portion, or segment, of an ACARS message with respect to the complete ACARS message. For example, a value of segment offset  408  may be  200  indicating that the portion or segment of the ACARS message, included in an Iridium Short Burst Data message with the message header, begins at a 200 th  character of the complete ACARS message. 
     Segment total  410  may be a one byte field used to indicate a total number of segments or portions of the complete ACARS message. For example, when an ACARS message is segmented into four portions, segment total  410 , with respect to message headers associated with each of the segments or portions included in separate Iridium Short Burst Data messages, may have a value of 4. 
     Compression indicator  412  may be a one byte field used to indicate use of a compression algorithm with respect an ACARS message in the Iridium Short Burst Data message. In one embodiment, a compression indicator value of 0 may indicate no compression, a compression indicator value of 1 may indicate compression by a first compression algorithm, a compression indicator value of 2 may indicate compression by a second compression algorithm, and so on. 
     One or more fields may be reserved for future use, such as, for example, reserved- 1   414  and reserved- 2   416 , which may each be one byte fields. 
     Exemplary Processing 
       FIG. 5  is a flowchart which illustrates exemplary processing performed in aircraft-based communication device  102  or ground-based communication device  110 , and an embodiment consistent with the subject matter of this disclosure. The process described in  FIG. 5  illustrates processing of a received Iridium Short Burst Data message. The process may begin with aircraft-based communication device  102  or ground-based communication device  110  (hereinafter, referred to as the processing device) receiving an Iridium Short Burst Data message via transceiver  205 . The Iridium Short Burst Data message may include at least a portion of a message conforming to AEEC specification 618, such as, for example, an ACARS message (act  502 ). 
     The processing device may then examine a message header, included in the Iridium Short First Data message, to determine whether the received Iridium Short Burst Data message includes a segmented ACARS message (act  504 ). The header may have a format as shown in  FIG. 4 . In one embodiment, the processing device may determine whether the received Iridium Short Burst Data message includes a segmented ACARS message by examining segment total  410  of the message header. If segment total  410  has a value of a 1, then the received Iridium Short Burst Data message may include a complete ACARS message. Otherwise, the received Iridium Short Burst Data message may include a portion, or segment, of the ACARS message. 
     If, at act  504 , the processing device determines that the received Iridium Short Burst Data message includes a complete ACARS message, then header stripper  304  of the processing device may discard the message header and the processing device may deliver the received ACARS message (act  522 ). If the processing device implements aircraft-based communication device  102 , then communications interface  250  of the processing device may deliver the ACARS message to avionics equipment  104 . If the processing device implements ground-based communication device  110 , then communications interface  250  of the processing device may deliver the ACARS message to message processing device  108 , which may return an ACARS acknowledgment to the processing device and may deliver the ACARS message to an intended destination, such as, for example, one of data providers  106 . 
     If, at act  504 , the processing device determines that the received Iridium Short Burst Data message includes a portion or segment of an ACARS message, then the processing device may obtain a message ID  406  from the message header (act  506 ). In embodiments consistent with the subject matter of this disclosure, all portions or segments of a single ACARS message may have a same value for message ID  406  in respective headers included in received Iridium Short Burst Data messages. 
     The processing device may then determine whether the received portion or segment of the ACARS message is a first segment (act  508 ). The processing device may determine whether the received portion or segment is the first segment by examining segment offset  408  of the header. If segment offset  408  has a value of 0 then, the received portion or segment of the ACARS message is the first segment. 
     If the processing device determines that the received portion or segment of the ACARS message is the first segment, then the processing device may save the value of message ID  406  from the message header in order to associate other received segments with a same ACARS message (act  510 ). Next, processing device may save a value of segment total  410 , which may indicate a total number of segments comprising the ACARS message (act  512 ). The processing device may then set a message segment counter to 1 (act  514 ). Header stripper  304  of the processing device may discard the message header and the processing device may save the message segment in order to later reconstruct the complete ACARS message (act  518 ). 
     If, at act  508 , the processing device determines that the portion or segment of the ACARS message included in the received Iridium Short Burst Data message is not the first segment of the ACARS message, then the processing device may increment the message segment counter (act  516 ), header stripper  304  may discard the message header and the processing device and may save the message segment in order to later reconstruct the complete ACARS message (act  518 ). 
     The processing device may then determine whether the ACARS message is complete (act  520 ). In one embodiment, message combiner  306  of the processing device may determine whether the ACARS message is complete by comparing the message segment counter, for counting the received message segments of the ACARS message, with a value of segment total  410  of the header. If the message segment counter equals the value of segment total  410  of the header, then all segments for the ACARS message have been received, message combiner  306  may reconstruct the message, and communication interface  250  of the processing device may deliver the reconstructed message (act  522 ). 
       FIG. 6  is a flowchart illustrating an exemplary process, which the processing device may perform when receiving an ACARS message from avionics equipment  104  (when the processing device implements aircraft-based communication device  102 ), or when receiving an ACARS message from message processing device  108  (when the processing device implements ground-based communication device  110 ). The process may begin with communication interface  250  of the processing device receiving the ACARS message (act  602 ). Message segmenter  310  of the processing device may determine whether the ACARS message is to be segmented in order to send the ACARS message via the Iridium Short Burst Data Service (act  604 ). Message segmenter  310  may determine that the ACARS message is to be segmented when a size of the ACARS message exceeds a maximum payload size of an Iridium Short Burst Data message, taking into account a message header to be included in the Iridium Short Burst Data message, such as, for example, the message header previously described with respect to  FIG. 4 . 
     If message segmenter  310  determines that the ACARS message is not to be segmented, then header adder  312  of the processing device may include the message header with the ACARS message in the Iridium Short Burst Data message and transceiver  205  may transmit the Iridium Short Burst Data message via the Iridium Short Burst Data Service (act  606 ). As previously discussed, the processing device may set a value of segment offset  408  to 0 and a value of segment total  410  to 1 in the header to indicate that the included ACARS message is not segmented. 
     If message segmenter  310  of the processing device determines that the ACARS message is to be segmented, at act  604 , then message segmenter  310  may segment the ACARS message into multiple portions or segments (act  608 ). Each of the portions or segments may be included in separate Iridium Short Burst Data messages with respective message headers (added by header adder  312 ) indicating an offset of the segment, with respect to the complete ACARS message, as well as a total number of segments, and a message ID, as previously discussed. Transceiver  205  of the processing device may then transmit each portion, or segment, of the ACARS message in the separate Iridium Short Burst Data messages, with the respective message headers, via the Iridium Short Burst Data Service. 
     In the exemplary processes of  FIGS. 5 and 6 , ACARS messages may include data to be sent to avionics equipment  104 , data received from avionics equipment  104 , or ACARS acknowledgements (acknowledging receipt of an ACARS message) from avionics equipment  104  or message processing device  108 . ACARS messages including ACARS data or ACARS acknowledgments may be treated in a same manner by processing device  200  when implementing aircraft-based communication device  102  or ground-based communication device  110 . 
     Conclusion 
     Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms for implementing the claims. 
     Although the above descriptions may contain specific details, they should not be construed as limiting the claims in any way. Other configurations of the described embodiments are part of the scope of this disclosure. Further, implementations consistent with the subject matter of this disclosure may have more or fewer acts than as described, or may implement acts in a different order than as shown. Accordingly, the appended claims and their legal equivalents should only define the invention, rather than any specific examples given.