Identifying boundaries of dominant regions dictating spectrum sharing opportunities for large secondary networks

An important parameter in determining a spectrum sharing opportunity is the level of interference power that secondary users may generate towards primary users. It is indicated in literature that the aggregate interference power of an infinite network (such as a very large secondary network) is bounded under certain conditions. However, to the best of our knowledge, no work has been devoted to determining the boundary of the dominantly interfering region. In this paper, we identify the smallest portion (dominant region) of the secondary network that would impact spectrum sharing opportunities. Our results show that the dominant region is not necessarily a small region encompassing a few interferers within the proximity of the primary user. Far interferers may tangibly contribute to spectrum sharing decisions when a higher approximation accuracy is required or when a wide exclusion region (within which no secondary users are allowed to transmit) is considered. On the other hand, the dominant region shrinks with the increase in the path-loss exponent or in the level of the interference threshold specified by the primary user or a regulator. Some implications of these results are highlighted. Moreover, the results are anticipated to inspire new ideas for designing MAC protocols for secondary networks.