Energy-Efficient Design for Relay-Aided MIMO-OFDM Cognitive Radio Networks

With the explosive growth of high-rate multimedia services and promptly boomed energy consumption in wireless networks, energy-efficient design is become more and more important. In this paper, we investigate energy-efficient design for relay-aided multiple-input multiple-output-orthogonal frequency division multiplexing (MIMO-OFDM) cognitive radio networks. We formulate an energy-efficient power allocation problem, which takes a form of nonlinear fractional programming. To solve the problem, we first make a joint concave approximation to the original problem which facilitates the optimal algorithm development. Then, we derive an equivalent parametric optimization problem of the approximated problem. Finally, an iteration energy-efficient power allocation algorithm is presented. Numerical results reveal that the proposed algorithm can improve energy efficiency over traditional capacity maximization method

Optimal Transmit Power Allocation for MIMO Two-Way Cognitive Relay Networks with Multiple Relays using AF Strategy

In this letter, we consider a multiple-input multiple-output two-way cognitive radio system under a spectrum sharing scenario, where primary and secondary users operate on the same frequency band. The secondary terminals aims to exchange different messages with each other using multiple relays where each relay employs an amplify-and-forward strategy. The main objective of our work is to maximize the secondary sum rate allowed to share the spectrum with the primary users by respecting a primary user tolerated interference threshold. In this context, we derive an analytical expression of the optimal power allocated to each antenna of the terminals. We then discuss the impact of some system parameters on the performance in the numerical result section