Design of a block time bounded TDMA (BTB-TDMA) MAC protocol for UANets

In this paper, a Block Time Bounded Time Division Multiple Access (BTB-TDMA) medium access control (MAC) protocol is proposed for mobile underwater nodes (UNs) in underwater acoustic networks (UANets). The BTB-TDMA determines transmission schedule of UNs based on UNs' estimated propagation delays (EPDs), reflecting on UNs' mobility. Furthermore, the scheduling algorithm gives UNs time bound for data transfer with a unit of time block in order to reduce overall delay and avoid packet collisions among UNs. To analyze the protocol's performance, we divide BTB-TDMA into two cases, BTB-TDMA considering EPDs (BTB-TDMA1) and BTB-TDMA without considering EPDs (BTB-TDMA2), to show how the use of EPDs can improve overall network performance. In addition, we analytically derive the channel access delay and channel utilization of STUMP (Kredo II et al., 2009) and TDMA, and compare them with those of BTB-TDMA. The numerical analysis shows that BTB-TDMA1 can reduce channel access delay by 20% and increase channel utilization by 35% at the maximum compared to those of BTB-TDMA2. BTB-TDMA2 provides at least 14% lower channel access delay and 37% higher channel utilization than STUMP. Furthermore, BTB-TDMA significantly outperforms TDMA, regardless of the network environment.