Performance Analysis of MultiACK-SFAMA for Underwater Acoustic Networks

MultiACK-Slotted Floor Acquisition Multiple Access (MultiACK-SFAMA) is a medium access control (MAC) protocol that has been proposed for underwater acoustic networks to overcome the problems of repeating the entire Request To Send (RTS) and Clear To Send (CTS) contention and DATA transmission cycle. In Slotted Floor Acquisition Multiple Access (S-FAMA), when an acknowledgement (ACK) fails to reach the transmitter, the entire cycle repeats. Multi-ACK mechanism has been analyzed in Shahabudeen et al. (IEEE J Ocean Eng 39(1):74–89, 2014). We chose to incorporate this mechanism in S-FAMA to enhance its performance. MultiACK-SFAMA is a modified version of S-FAMA and is aimed to avoid that a successful data transmission is wasted because the acknowledgement is lost, thus saving energy, by using a train of ACKs instead of a single ACK for each DATA packet. By using MultiACK, the probability that an ACK would be received successfully increases. In underwater acoustic networks, due to high propagation delay the cost of losing an ACK is very high and significantly impacts the performance of the protocol. The MultiACK mechanism has been proposed and analyzed to improve the S-FAMA performance. The MultiACK mechanism increases the probability of receiving at least one ACK packet by replying with a train of ACK packets. In this paper we present a mathematical analysis of MultiACK-SFAMA. The paper presents analysis of the performance of MultiACK-SFAMA as a function of transmission range, number of nodes and bit error rates. The results show that the throughput improvement (%) achieved is improved by using a MultiACK train instead of a single ACK. The MultiACK train improves the probability of receiving an ACK by 65.05%, for a BER of 0.005 and saves energy.