Optimal power allocation for multiple-input-multiple-output relaying system

In a cooperative relaying system, multiple-input-multiple-output (MIMO) capacity enhancement techniques are applied to mobile terminals (MT) with a limited number of antenna elements. The adaptive optimal power allocation (OPA) scheme among the relay stations (RSs) is an important issue to achieve power efficiency and maximum performance improvement. The paper proposes a cooperative relaying system model based on MIMO technology, where the RSs are utilized to emulate the multi-antenna environment. In addition, an OPA scheme, through singular value decomposition (SVD) of the channel matrix, is developed among the RSs under a certain power constraint to achieve the maximum channel capacity. Numerical results indicate that, compared with the uniform power allocation (UPA) scheme, the OPA scheme improves the capacity significantly when the RSs are close to the transmitter (TX). However, if the RSs are close to the receiver (RX), there is almost no difference between these two schemes, which is similar to the case in the traditional MIMO system.