Power Allocation for Improved DF Relayed OFDM Transmission: The Individual Power Constraint Case

We consider an OFDM (orthogonal frequency division multiplexing) point to point transmission scheme improved by a relay. For each carrier, symbols sent by the source may be retransmitted during a second time slot by the relay, which is assumed to be of the decode-and-forward (DF) type. For each relayed carrier the destination implements maximum ratio combining. Assuming perfect CSI (channel state information) knowledge the paper investigates the power allocation problem in order to maximize the rate offered by the scheme. Compared to, the second time slot is better used. The source is allowed to transmit a new symbol during this second time slot when the relay is inactive. For this improved protocol, the optimization has been conducted for a sum power constraint and reported in. The present paper is devoted to the case of individual power constraints at the source and at the relay. The theoretical analysis is illustrated by numerical results.