Achievable energy efficiency in cooperative transmission system with frequency-selective power allocation

In this paper, we study the energy efficiency in the multiple access points (AP) coherent cooperative transmission (CCT) system with frequency-selective fading. Supposing the per antenna power constraint is sufficient, we derive the achievable optimal energy efficiency by distributing the transmit power among subchanels and cooperative APs, aiming at minimizing the Joule consumed per transmission bit of the CCT system. Based on Dinkelbach´s theory, we solve our main problem with the associated parametric programming problem, and prove that the problem for the CCT can be transformed into an equivalent problem for the single AP transmission (SAT), which is much easier to be solved. The analytical solution is derived, along with an optimal power allocation algorithm. Numerical results are given to verify our analysis, and demonstrate that with the proposed scheme, the CCT outperforms the SAT in terms of the energy efficiency.