Pro-active message acknowledgement collection for improved data link preformance over reliable transport media

A computer implemented method and computer program product for improved data link performance over reliable transport media in a satellite-based global telecommunications network (e.g., Short Burst Data (SBD) transaction network) to reduce downlink latency includes sending a message over reliable transport media in the satellite-based global telecommunications network, polling for a response to the sent message and receiving the response to the sent message. In an aspect of the embodiment, the method can further include polling when a message alert notification is not received. In another aspect of the embodiment, the method can further include polling a single time. In yet another aspect of the embodiment, the method can include polling when a message alert timeout counter elapses.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to satellite-based global telecommunications networks and more particularly to pro-active message acknowledgement collection for improved downlink performance over reliable transport media in satellite-based global telecommunications networks.

Description of the Related Art

With the development of a global economy, commercial satellite-based global telecommunications networks have been developed. These networks typically provide both voice (telephone) and data link (messaging) services. One of the first of such networks has been operated by Iridium LLC since Nov. 1, 1998. The international aviation community has been using the Iridium global satellite network to provide worldwide voice and data services between airlines, air traffic control centers, and aircraft.

The data link services of the Iridium satellite network can be either circuit-switched, using the voice system to set up a dial-up data link, or message-switched, using either the Short message Service (SMS) or the Short Burst Data (SBD) techniques. The international aviation community has selected the SBD service to build the satellite-based extension of the worldwide Aircraft Communications Addressing and Reporting System (ACARS). As this service matured and operational data became available on data link performance over Iridium SBD, some issues became apparent.

ACARS has been originally developed with unreliable transport media in mind. Traditional broadcast radio on Very High Frequency (VHF) radio bands by itself does not guarantee the correct and complete reception of any broadcast message. Therefore, ACARS implemented a two-phase message protocol, where each sent message must be individually acknowledged by a specific response. When this protocol was implemented on the reliable transport media of the Iridium SBD system, the same send-response mechanism was used. Under certain conditions, the selected implementation leads to sub-optimal performance of the overall data link. In particular, successfully transmitted messages may remain unacknowledged due to a peculiarity in the Iridium SBD signaling system. The current implementation of the ACARS-over-Iridium-SBD system does not handle this anomaly gracefully and reverts to the backup approach of re-sending the message after 180 seconds. During this waiting time, the complete data link is blocked. The present invention offers a solution to this data link blocking that (a) offers a significant improvement of the existing ACARS-over-Iridium-SBD performance, (b) offers a less costly alternative to the 180 second re-send approach, and (c) does not need any change in existing satellite or ground equipment, while allowing existing airborne equipment to remain unchanged at the operator's discretion.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the present invention address deficiencies of the art in respect to satellite downlink performance (e.g., short burst data (SBD) transactions) and provide a novel and non-obvious method, system and computer program product for reducing downlink latency in a satellite-based global telecommunications network using pro-active message acknowledgement collection. In an embodiment of the invention, a computer implemented method for pro-active message acknowledgment collection for improved data link performance over reliable transport media in a satellite-based global telecommunications network to reduce downlink latency, includes sending a message over reliable transport media in the satellite-based global telecommunications network, polling for a response to the sent message and receiving the response to the sent message. In an aspect of the embodiment, the method can further include polling when a message alert notification is not received. In another aspect of the embodiment, the method can further include polling a single time. In yet another aspect of the embodiment, the method can include polling when a message alert timeout counter elapses.

In another embodiment of the invention, a computer implemented method for reducing downlink latency in a satellite-based global telecommunications network by use of a virtual message waiting acknowledgement, includes receiving a message from a message client, performing a bi-directional transaction (e.g., SBD transaction) with the satellite-based global telecommunications network, validating the success of the bi-directional transaction (e.g., SBD transaction), determining if a message alert notification (e.g., SBD RING) was transmitted by the satellite-based global telecommunications network, performing a second bi-directional transaction (e.g., SBD transaction) with the satellite-based global telecommunications network and requesting a message receipt acknowledgement from a service provider and upon validating the success of the second SBD transaction; forwarding the message receipt acknowledgement from a service provider to the message client. In another aspect of the embodiment, the method can include setting a virtual message alert timeout counter. In yet another aspect of the embodiment, the method can include determining if the virtual message alert acknowledgement timeout counter has expired.

In accordance with another aspect, the present invention provides a computer program product for reducing downlink latency in a satellite-based global telecommunications network by use of a virtual message acknowledgement. The method includes performing a bi-directional transaction (e.g., SBD transaction) with the satellite-based global telecommunications network, validating the success of the bi-directional transaction (e.g., SBD transaction), determining if a message alert notification (e.g., SBD RING) was transmitted by the satellite-based global telecommunications network, performing a second bi-directional transaction (e.g., SBD transaction) with the satellite-based global telecommunications network and upon validating the success of the second bi-directional transaction (e.g., SBD transaction); forwarding a message receipt acknowledgement from a service provider to the message client. In another aspect of the embodiment, the method can include requesting a message receipt acknowledgement from a service provider. In yet another aspect of the embodiment, the method can include setting a virtual message alert timeout counter. In yet another aspect of the embodiment, the method can include determining if the virtual message alert acknowledgement timeout counter has expired.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the invention provide for method, system and computer program product for reducing SBD downlink latency in a satellite-based global telecommunications network using pro-active message acknowledgement collection. In an embodiment of the invention, a computer implemented method for pro-active message acknowledgment collection for improved data link performance over reliable transport media in a satellite-based global telecommunications network to reduce downlink latency, includes sending a message over reliable transport media in the satellite-based global telecommunications network, polling for a response to the sent message and receiving the response to the sent message. In an aspect of the embodiment, the method can further include polling when a message alert notification is not received. In another aspect of the embodiment, the method can further include polling a single time. In yet another aspect of the embodiment, the method can include polling when a message alert timeout counter elapses

In an embodiment of the invention, a computer implemented method for reducing downlink latency in a satellite-based global telecommunications network by use of a virtual message waiting acknowledgement, includes receiving a message from a message client, performing a bi-directional transaction (e.g., SBD transaction) with the satellite-based global telecommunications network, validating the success of the bi-directional transaction (e.g., SBD transaction), determining if a message alert notification (e.g., SBD RING) was transmitted by the satellite-based global telecommunications network, performing a second bi-directional transaction (e.g., SBD transaction) with the satellite-based global telecommunications network and requesting a message receipt acknowledgement from a service provider and upon validating the success of the second SBD transaction; forwarding the message receipt acknowledgement from a service provider to the message client. In another aspect of the embodiment, the method can include setting a virtual message alert timeout counter. In yet another aspect of the embodiment, the method can include determining if the virtual message alert acknowledgement timeout counter has expired.

To understand the method for a computer implemented method for reducing downlink latency (e.g., Short Burst Data (SBD)) in a satellite-based global telecommunications network by use of a virtual message alert notification (e.g., a virtual SBD RING acknowledgement) in accordance with the present invention, first an embodiment of the telecommunications system which may use the present invention needs to be described.

FIG. 1illustrates a telecommunications system which may be used with the present invention. The system100includes low earth orbiting satellites105, gateways110, and system control115. System Control115serves as the central management component for the system100. Gateways110interconnect the satellite constellation105with public switched telephone networks125(PSTN), making communication possible between system wireless subscriber units (WSU)130, such as a wireless phone or a fixed wireless device, and any other telephone in the world. Telecommunications services may also be provided to pagers135, aircrafts140, and automobiles145. Satellite Data Units (SDU)402may reside in the pagers135, aircrafts140, and automobiles145. SDUs402pass message envelopes from a message client401to a satellite-based global telecommunications network403(e.g., the Iridium satellite network). In the Iridium satellite network403, the downlink and uplink messages are combined in bi-directional transactions416a,416band466a,466b.

The satellites105of the system100employ intersatellite links150, or “crosslinks”, to communicate directly with each other. These crosslinks150provide reliable, high-speed communications between neighboring satellites, allowing call routing and administration to occur efficiently.

FIG. 2is a graph of the typical downlink latency of a global telecommunications network. As illustrated byFIG. 2, the downlink performance206(solid line) was much better than the end-to-end downlink plus uplink performance208(dotted line), indicating an issue with the uplinked acknowledgements. Both downlink and uplink are exactly the same kind of bidirectional transaction (e.g., SBD transaction); however, a difference in the performance is noticeable. In addition, the uplink performance208(dotted line) catches up to the downlink performance206(solid line) at about 210 seconds. An analysis of the ACARS protocol (ARINC618) indicates that the bump at 210 seconds came from the downlink message retry timer at 180 seconds. If for whatever reason the downlinked message was not acknowledged by the ground within 180 seconds, the same message would be downlinked again, which typically would successfully trigger an acknowledge (message waiting notification or alert (e.g., virtual SDB RING)). The graph200has an x-axis204to denote time in seconds and a y-axis202to denote the delivery rate of the messages. The horizontal gap214between the uplink performance208and the downlink performance206is approximately 15 seconds and within the expected range. The vertical gap216between the uplink performance208and the downlink performance206illustrates a significant drop off in performance of the uplink end-to-end message waiting notification or alert (e.g., virtual SDB RING). There are two delivery cliffs illustrated inFIG. 2, a 95%-within-90-seconds cliff210and a 99.9%-within-180-seconds cliff212, which are the targets of the industry.

FIG. 3is a graph of the downlink latency of a global telecommunications network using the virtual message waiting notification or alert (e.g., virtual SDB RING) of the present invention. As illustrated byFIG. 3, the generation of a mailbox check (e.g., a poll for a response) (uplink) 20 seconds after a successful downlink conditioned on no message waiting notification or message alert notification (e.g., SDB RING) being received, which is called a virtual message waiting notification or alert (e.g., virtual SDB RING), resulted in the acknowledgement uplinks performance line308to vertically match the downlink performance line306, which indicates the same performance for acknowledgement uplinks as for message downlinks. In order to keep operational costs down and prevent unnecessary system load, the Data Service Providers (DSPs) currently prohibit unsolicited mailbox checks (e.g., mailbox polling or polling for a response). Unlike VHF ACARS, Iridium bi-directional transactions (e.g., SBD transactions) are not a blind unidirectional broadcast. Once we verify that a downlink bi-directional transaction (e.g., SBD transaction) has succeeded, then it is known that an acknowledgement will be ready for retrieval in a few seconds. In about 98% of all cases, a SDU402receives a bi-directional transaction (e.g., SBD transaction) within 5-10 seconds and retrieves the acknowledgement uplink. In the remaining 2% of the time, however, the bi-directional transactions (e.g., SBD RINGS) are not received due to the well-known Iridium R/F dropout. Such an acknowledgement (ACK) failure leads to a retransmission of the downlink 180 seconds later. Thus, a complete SBD transaction must occur. On the other hand, if a mailbox check is forced a certain time after expected SBD RING is missed, then no increase in the message traffic would occur. Notably, the virtual SBD RING would actually save one SBD transaction by pro-actively hunting for the mailbox in well-defined cases as the Data Service Provider (DSP), such as SITA, would not need to acknowledge the message twice.

FIG. 4is a flow chart illustrating a process for reducing downlink latency (e.g., SBD transaction) in a satellite-based global telecommunications network by using a virtual message alert notification (e.g., SBD RING acknowledgement) in the satellite-based global telecommunications network. Beginning in block405, a message client401can desire to send a message over the satellite-based global telecommunications network. In block410, a composed message from the message client401is received by the satellite data unit (SDU)402. In block415, the SDU performs a SBD transaction with the satellite-based global telecommunications network403via a bi-directional link416that is a combined downlink416aand uplink416b. In block420, the success of the SBD transaction is validated and the exclusive event gateway430is accessed. Otherwise, if the SBD transaction was unsuccessful, then the SDU402will re-try the SBD transaction in block415. In block440, the satellite-based global telecommunications network403sends the message to a data service provider (DSP). When the satellite-based global telecommunications network403receives an acknowledgement message from the DSP in block445, the satellite-based global telecommunications network403sends a SBD RING to the SDU402in block450. Thereafter, in block455, a SBD RING can be received by the SDU402. However, if the SDU402does not receive the SBD RING, then in block460a virtual SBD RING timeout counter can be set when the exclusive event gateway430is accessed. In an embodiment, the virtual SBD RING timeout counter can be set for 20 seconds. Once either the SBD RING is received or the virtual SBD RING timeout counter expires, a second SDB transaction (such as a mailbox check) can be generated at block465and sent to the satellite-based global telecommunications network403via a bi-directional link466that is a combined downlink466aand uplink466b. In block470, the success of the SBD transaction is validated and the message is retrieved. Otherwise, if the SBD transaction was unsuccessful, then the SDU402will re-try the SBD transaction in block475. In block480, the SDU402sends the retrieved message to message client401. Once the message client401receives the retrieved message, a resend timeout counter of the message client can be disabled.