In the context of aging populations, maintaining persons at home represents one of the solutions seriously considered. In France, one person among three will be over 60 years in 2050, against one among five in 2005. Many works have investigated the monitoring of elderly peoples inside the institutions or homes (i.e. smart homes) but less in the outside. In this work, we investigate the outdoor monitoring for elderly in the context of smart cities. For this purpose, we focus our research on the problem of localizing the persons when they are outside. We propose an efficient algorithm in terms of rapidity, energy-saving, accuracy and cost. We improve the DV-Hop algorithm by using a genetic algorithm in the anchor selection step to efficiently recognize the location of the person and decrease the error rate.