To improve the outage performance of a bidirectional amplify and forward relaying system in an asymmetric Rayleigh fading channel

a new power allocation scheme based on minimizing the outage probability is proposed. First

the asymmetry factor is introduced

and under the theoretical analysis

the closed outage probability expressions of four cases asymmetric two-way relay channel with traditional three nodes network structure is derived. Simulation results show that downlink asymmetry is the worst case. Furthermore

in order to minimize the downlink asymmetry system outage probability

a power allocation scheme based on channel state information is proposed. In this scheme

the power allocation is a piecewise function of the asymmetry factor. The node can adjust the transmission power adaptively according to the variation of the channel state. Simulation results show that the proposed power allocation scheme can improve the outage performance of the downlink asymmetric two-way relay system. Compared with the equal power allocation scheme

the smaller the asymmetry factor is

the better the effect is.