Performance of undersea acoustic networking using RTS/CTS handshaking and ARQ retransmission

The performance of networked undersea acoustic communications is improved through implementation of handshaking between each pair of adjacent modems along the network route. The handshake begins with the sending modem transmitting a short request to send (RTS) packet to the receiving modem. On successful receipt of the RTS, the receiving modem replies with a short clear to send (CTS) packet. In the event of failure to complete the handshake, a timer in the transmitting modem triggers additional RTS transmissions. On successful completion of the RTS/CTS handshake, the sending modem transmits the data packet. Large data packets can require acoustic transmission times on the order of tens of seconds. During these long transmissions, there is increased potential for dropped packets as a result of unrecoverable bit errors. The automatic repeat request (ARQ) is a means of accomplishing a successful, error-free data transfer in the event of such dropped data. The receiving modem, upon receipt of a corrupted data packet, issues a short ARQ packet to the sending modem that acts as a request to re-send the data packet or portions thereof. Statistics from an actual undersea acoustic network demonstrate the advantages of using RTS/CTS handshaking and ARQ retransmissions.