Optimal pilot patterns considering optimal power loading for Cognitive Radios in the two dimensional scenario

In Orthogonal Frequency Division Multiple Access (OFDMA) based Cognitive Radio (CR) systems, optimal power loading schemes are devised such that the transmission rate is maximized while maintaining interference from Secondary Users (SUs) to Primary Users (PUs) below a specified threshold. The power loading algorithms however do not distinguish between data and pilot symbols. A similar situation exists for optimal pilot patterns where pilots are placed in the optimal positions to achieve the lowest Mean Squared Error (MSE) but no consideration is given to power loading schemes. This paper investigates this scenario and proposes an optimal solution based on the Least Squares (LS) estimator which could be applied to future CR algorithm implementations as well as a possible standardization aspect to ensure an optimal solution to a crucial problem in practical implementations.