The concept of Cognitive Radio (CR) is meant to be utilised by both licensed and license-exempt users that coexist in a shared spectrum area whenever they need to avoid causing unaffordable interference to each other by following some rules. In fact, primary users should be protected by any license-exempt transmission. To this end, power control is a pivotal mechanism to be used for interference management in these scenarios. Especially, transmit power control is a vehicle to mitigate interference, in presence of CR technology, when primary receivers are attempting to reach a desired Signal-to Interference Noise Ratio (SINR) level. In this work we assume that a CR network relies on the same spectrum area with a primary network. Our scope is to measure the introduced interference level caused by the CR transmitter and to properly modify its power to allow a legacy user to reach a required SINR according to location of the primary user in presence of interference. A series of results are presented to prove the efficiency of our proposed scheme.