## 3 Proposed System Model
### DAWPC-MAC Model Overview  
The DAWPC-MAC primary design objectives is to reduce energy consumption by controlling when nodes wake up and when they enter sleep mode. These main aspects of the protocol are the receiver-initiated wake-up, adaptive power control, an adaptive scheduling mechanism in the case when more than one node wants to send data, and a dynamic response where important data transmissions take priority. Receiver-initiated wake up mechanism is where the Rx node actively takes part in control of a communication cycle. Only a periodic low-power Wake-Up signal (WS) is transmitted at regular intervals by the Rx node instead of nodes that must be continually listening for incoming transmissions. This indicates to other Tx nodes the timing for the next communication window. Minimizing wakeups and hence energy usage, only Tx nodes wishing to send data in that time window respond to the Rx node. First, the wake-up signal is transmitted at a low power level to minimize its coverage area. If no responses are received by the Rx node, adaptive power control is employed, progressively increasing the transmission power to extend the coverage and reach more distant Tx nodes. Once a Tx node responds, communication continues with minimal power usage to ensure energy conservation. The adaptive power control mechanism optimizes well the energy consumption efficiency, and do well in limiting the transmission power. This also helps in avoiding the under-utilization of the communication channel. Besides, given the importance of influence of depth and density of all the different types of considered nodes either receiving or transmitting, Figure 2.  
The timer mechanism is crucial for optimizing energy usage. After broadcasting a wake-up signal (WS), a timer is started by the Rx node to await a response from Tx nodes. If a transmit signal (TxS) is received within the allotted time frame, the timer is stopped, and a response signal (RxS) is immediately sent to all neighboring Tx nodes, informing them of the communication parameters (e.g., Network Allocation Vector (NAV), transmission slots). If no TxS signal is received within the timer duration, sleep mode is entered by the Rx node, conserving energy until the next scheduled wake-up. This response system  
Figure 2: Schematic of node locations and density within the considered environment: This figure shows the distribution of nodes within the underwater environment, depicting the varying density of nodes and how they are spatially distributed to optimize network performance. prevents unnecessary power consumption and idle listening, a common source of energy drain in traditional MAC protocols. Upon receiving critical data packets (time-sensitive and critical data, such as object-tracking information or other emergency data, which require immediate processing to ensure application functionality), communication with the corresponding Tx node is prioritized by the Rx node to ensure timely delivery of these critical data packets. This prioritization ensures that high-priority traffic is always delivered with minimal delay, even under high network load, without compromising the energy-efficient operation of the network. An adaptive schedule-based TDMA is used for more nodes to transmit data for slot allocation in a frame, while if a frame has too many slots, channel capacity is wasted because some slots remain unused. On the other hand, if the frame size is too small, enough time is not given for nodes to avoid collisions. The right frame size must be found to make the best use of the channel [37]. A smaller frame initially improves channel use, but beyond a certain size, an increase in the frame leads to more collisions, reducing efficiency. The allocated communication slots sizes are determined based on the energy status, node position, high-priority traffic, and high traffic demands of each node.