OSPG-MAC: An OFDMA-Based Subcarrier Pregrouping MAC Protocol for Underwater Acoustic Wireless Sensor Networks

Algorithm 1

OSPG-MAC algorithm.

Initialization:

Estimate the water-filling level by Formula (11), estimate

the discrete values of the transmit power , the bits , and

the total transmit power by Formulas (12), (3), and (5),

respectively.

Step 1: Calculate the additional power required for each

subcarrier to add one bit. For all , calculate ,

let , .

Step 2: If , go to Step 3. Otherwise, go to Step 4.

Step 3: If, end. Otherwise, load

one bit on the subcarrier that requires the least power:

, , return to Step 1.

Step 4: Remove one bit from the subcarrier that requires the

most power: , .

If, end. Otherwise, return to Step 1.