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

Abstract

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 RTSKTS 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 resend the data packet or portions thereof. Statistics from an actual undersea acoustic network demonstrate the advantages of using RTSKTS handshaking and ARQ retransmissions.

Performance evaluation of forwarding protocols for the RACUN network

“…Channel characterization aspects are present in both projects but, unlike in RACUN, they are employed for basic propagation and Signal-to-Noise Ratio (SNR) prediction rather than for the simulation of physical transmission schemes. The pioneering SeaWeb [3] project focused on the creation and medium-term evaluation of an underwater network using simple MAC and routing protocols, and was among the first to show that underwater networking is in fact possible. Several underwater channel measurement campaigns have been carried out so far, recent examples including SPACE'08 and KAM'11.…”

An Energy-Efficient MAC Protocol for Underwater Wireless Acoustic Networks

“…SeaWeb 2000 favored a CSMA/CA solution with RTS/CTS exchange; however, the problem with the CSMA/CA solution is that it exacerbates the end-to-end delays that are incurred, especially in underwater sensor networks with a large number of nodes. In addition, in [12], the authors use both the RTC/CTS handshaking and ARQ retransmission at the MAC layer to minimize data loss, which increases the energy consumption.…”

The Underwater Selective Repeat Error Control Protocol for Multiuser Acoustic Networks: Design and Parameter Optimization

“…In this case, Automatic Repeat reQuest (ARQ) policies are needed to recover from packet errors. Such events are quite likely in real scenarios: for this reason, pioneering efforts in UW networking such as SeaWeb [2] incorporate some form of ARQ.…”

“…1536-1276/13$31.00 c 2013 IEEE or more kilometers, which turns into propagation delays of 1 s to 2 s. 2 The packet transmission times obtained with typical modem hardware in many underwater scenarios are shorter than these values [11], therefore employing S&W would turn into very low throughput.…”

“…With JSW, the sender transmits a fixed number of data packets as specified by a pre-calculated window size, and then waits for the related ACK/NACK before performing further transmissions. This does not allow a node to fall back to S&W cycles in the presence of low traffic (e.g., when a node has only one packet 2 Many modems available to date support transmissions over such distances. For instance, AquaComm supports ranges of 3 km [8], the LinkQuest UWM2000 and UWM3000 modems support 1.5 km and 3 km, respectively [9], and the Evologics S2C R 48/78 modem supports 3.2 km [10].…”