In [4], a fuzzy logic-based optimization of lifetime and source-to-sink delay is proposed. The membership function is very complicated and the encountered complexity goes beyond the processing capabilities of each node. Minimizing the error probability and the energy consumption is presented in [5]. A sub-optimal solution is obtained by converting the MOPT into SOPT sub-problems. This sub-optimal approach achieves better performance in terms of energy consumption, but has worse performance in terms of the delay.
In [6], Martins et al. introduce a solution for the dynamic coverage and connectivity using an evolutionary algorithm. The MOPT approach provides a feasible solution for extending the WSNs lifetime but with the loss of the network mean coverage. The authors in [7] introduce a hybrid geographical routing (HGR) algorithm, as a multi-objective approach that combines the distance-based routing and the direction-based routing. Distance-based routing chooses a neighbor with the largest distance progress toward the sink, while the directionbased routing prefers a neighbor with the lowest angle of deviation toward the sink. The algorithm performance depends
heavily on the choice of a fixed weighting factor based on empirical results. HGR ignore the cost and the complexity associated with the switch between the two approaches based on the distance and the direction.