The pathloss model in the literature suffers from two major deficiencies: First, it is distance dependent, whereas the distance of an interior link is unknown to outsiders. Second, it suffers from line-of-sight (LOS) uncertainty with channel parameters fluctuating sharply between LOS and non-LOS conditions. In this paper, we address these problems by taking the distance as a random variable and by introducing a room-density index that combines the LOS and non-LOS conditions. We then modify the widespread IEEE 802.15.4a pathloss model into a unified pure statistical pathloss model that is a function of the room size and the room-density index. This pure statistical model supplements the conventional pathloss model and can help cognitive users infer pathloss information of the non-cognitive without knowing the latter's link distance.