The impact and benefits of infrastructure support are shown by introducing an achievable throughput scaling law of a ultra-wide band (UWB) ad hoc network in which m base stations (BSs) are regularly located. The existing multi-hop scheme consisting of two variants, with and without BS help, is utilized with a slight modification. Our result indicates that the derived throughput scaling depends on the path-loss exponent due to the power-limited characteristics for all operating regimes examined. Furthermore, it is shown that the total throughput scales linearly with parameter m as m is larger than a certain level. It thus turns out the use of infrastructure is also helpful in improving the throughput scaling of UWB networks in some conditions.