A Joint Power Allocation and Scheduling Algorithm Based on Quasi-Interference Alignment in Underwater Acoustic Networks

This work investigates a joint power allocation and transmission scheduling algorithm for underwater acoustic (UWA) networks to improve the throughput by leveraging the low sound speed in water. We consider a round-based UWA system where transmission links are active concurrently to send multiple signal blocks during each round. To mitigate the interference, a quasi-interference alignment (IA) method is proposed where the interference signals are aligned as much as possible while a low level of collisions between useful and interference signals is allowed. Specifically, the transmission starting time and transmission power are jointly optimized to maximize the total transmission capacity. Different from the conventional IA, the proposed mechanism intends to reduce the total reception time by tolerating slight collisions of useful signals while adapts the power allocation to compensate for the collisions, which could increase the transmission degrees of freedom (d.o.f.). To solve the optimization problem in a tractable way, we decompose the problem into two smaller sub-problems which optimize the transmission schedule and power allocation with a smaller feasible region. The simulation results show that, with an appropriate collision level, the proposed method could achieve decent throughput improvement, compared to the conventional IA and a benchmark method which solves the optimization problem by the genetic algorithm.