Power Allocation for Cognitive Radios Based on Primary User Activity in an OFDM System

Efficient and reliable power allocation algorithm in Cognitive Radio (CR) networks is a challenging problem. Traditional water-filling algorithm is inefficient for CR networks due to the interaction with primary users. In this paper, the authors consider reliability/availability of subcarriers or primary user activity for power allocation. They model this aspect mathematically with a risk-return model by defining a general rate loss function. They then propose optimal and suboptimal algorithms to allocate power under a fixed power budget for such a system with linear rate loss. These algorithms as they will see allocate more power to more reliable subcarriers in a water-filling fashion with different water levels.