Toward More Adaptive UAV-to-UAV GBSMs: Introducing the Extended vMF Distribution

An extension of the von Mises-Fisher (vMF) distribution is introduced into the two-sphere geometrical model for unmanned aerial vehicle (UAV) air-to-air channels. Under this new distribution, the space-time correlation function (ST-CF) is obtained as a closed-form expression, which has better adaptability than the previous one under the traditional vMF distribution. The correctness of the derived expression is validated by the good agreement with numerical results. Based on the new ST-CF, the UAV-to-UAV channel capacities are analyzed for a more general scattering environment.