Many Iraqi and American officials are convinced that even a modest force would have been able to prevent chaos — not by fighting but by providing training, signals intelligence, and a symbolic presence.
All these cannot receive training signals.
Important findings revealed on optimal training signals are twofold: (i) the energies of the training signals on each subcarrier are equal, and (ii) on each subcarrier, the training signals transmitted from the different antennas are orthogonal and of equal energy.
Simulation results show that the training signals based on the optimality conditions outperform other non-optimal training signals in terms of channel estimation performance.
Given a constraint which effectively limits the transmit power of training signals, we also investigate the optimal design of training signals under both criteria.
The optimal training signals are usually obtained by minimizing the channel estimation error.
Five non-optimal training signals are also generated for performance comparisons.
Here, we consider the ZCZ sequences as optimal training signals without loss of generality.
Note that optimal designs of training signals are not limited to the following cases.
Section 4. formulates and solves the optimization problem that allows to find the optimal training signals.
In this section, we verify the optimality of the training signals through extensive computer simulations.
