
132 Energy-Efficient Cooperative Wireless Communication and Networks
higher number of antennas is used. In comparison, the problem dimension of
the proposed JPA I and II in this chapter is linear with the number of antennas.
Furthermore, due to the fact that the sum-rate is non-concave for any fixed
source beamformers, the s earching algorithms in Xu and Hua [65] have to
be repeated multiple times with dif ferent starting points in order to increase
the probability of finding the global optimal relay beamformer. This further
increases the computational overhead.
In order to obtain the simulation results for A-Opt, the weighted mini-
mum MSE algorithm ...