Helicopter satellite communication system, helicopter-mounted communication apparatus, terrestrial station communication apparatus, communication method, and non-transitory computer-readable recording medium storing computer program

摘要

A helicopter-mounted communication apparatus encodes video data at a compression rate based on a percentage of time a transmission beam is blocked by rotor blades. When a number of video packets is less than a specified number, the helicopter-mounted communication apparatus inserts null packets to keep a packet rate constant, then deletes the null packets and attaches additional information to another packet indicating the number of deleted null packets, and after buffering modulates and transmits a signal toward a communication satellite at transmittable-time points. A terrestrial station communication apparatus receives and demodulates the transmitted signal via the communication satellite, generating a packet stream, and based on the additional information included in the generated packet stream, inserts null packets in the packet stream and buffers the packet stream, thereby keeping the packet rate constant, and then separates the video packets from the packet stream and decodes the separated video packets.

主权项

1. A helicopter satellite communication system that performs communication between a helicopter-mounted communication apparatus and a terrestrial station communication apparatus via a communication satellite, wherein
the helicopter-mounted communication apparatus includes: a blocked-time-rate estimator that estimates a blocked-time rate, which is the percentage of the time that a transmission beam that is transmitted from the helicopter-mounted communication apparatus toward the communication satellite is blocked by rotor blades; a video-encoding-parameter selector that selects video-encoding parameters based on the blocked-time rate that is estimated by the blocked-time-rate estimator; a video encoder that encodes video data according to the video-encoding parameters selected by the video-encoding-parameter selector, and outputs video packets; a data selector that, when the number of video packets that are output from the video encoder is less than a specified number, inserts null packets to keep the transmission packet rate substantially constant; a null-packet deleter that deletes null packets in a packet stream that is output from the data selector and attaches information indicating the number of the deleted null packets to another packet; a buffer that buffers packets after deleting of null packets by the null-packet deleter; and a modulator/transmitter that modulates packets that are stored in the buffer and transmits those packets toward the communication satellite during a transmittable period; and the terrestrial station communication apparatus includes: a receiver that receives a signal that is transmitted from the helicopter-mounted communication apparatus via the communication satellite; a demodulator that demodulates the signal received by the receiver and generates a packet stream; a null-packet inserter that, based on attached information that is included in the packet stream that is reproduced by the demodulator, inserts null packets into the packet stream and deletes the attached information; a rate-fluctuation compensator that keeps the packet rate substantially constant by buffering a packet stream after inserting of null packets by the null-packet inserter; a data separator that separates video packets from the packet stream that is output from the rate-fluctuation compensator; and a video decoder that decodes the video packets that are separated out by the data separator.