Exposure optimization in indoor wireless networks by heuristic network planning

Due to the increased use of indoor wireless networks and the concern about human exposure to radio-frequency sources, exposure awareness has increased during recent years. However, current-day network planners rarely take into account electric-fleld strengths when designing networks. Therefore, in this paper, a heuristic indoor network planner for exposure calculation and optimization of wireless networks is developed, jointly optimizing coverage and exposure, for homogeneous or heterogeneous networks. The implemented exposure models are validated by simulations and measurements. As a flrst novel optimization feature, networks are designed that do not exceed a user-deflned electric-fleld strength value in the building. The in∞uence of the maximally allowed fleld strength, based on norms in difierent countries, and the assumed minimal separation between the access point and the human are investigated for a typical o-ce building. As a second feature, a novel heuristic exposure minimization algorithm is presented and applied to a wireless homogeneous WiFi and a heterogeneous WiFi-LTE femtocell network, using a new metric that is simple but accurate. Field strength reductions of a factor 3 to 6 compared to traditional network deployments are achieved and a more homogeneous distribution of the observed fleld values on the building ∞oor is obtained. Also, the in∞uence of the throughput requirement on the fleld strength distribution on the building ∞oor is assessed. Moreover, it is shown that exposure minimization is more efiective for high than for low throughput requirements and that high fleld values are more reduced than low fleld values.