A multi-objective optimization algorithm aims at producing (1) solutions as close as possible to the POS and (2) solutions as diverse as possible in the obtained non-dominated set. This diverse set of optimal solutions expresses trade-offs between different objectives. Routing protocols for WMSN must take into account a set of QoS requirements like bandwidth, delay, energy consumption. The ETX metric allows finding high throughput paths on a multi-hop wireless network, and incorporates the effects of link loss ratios, asymmetry in the loss ratios between the two directions of each link, and the interference among the successive links of a path.