Analog network coding (ANC) is an effective scheme for increasing network throughput by simultaneously transmitting packets from sources to a relay and amplifying and forwarding the superposition of the packets from the relay to the corresponding destinations. The ANC scheme theoretically reduces half of the required transmission phases in cooperative relaying networks, including two source-destination pairs and a single relay. Such an advantage can be obtained only when the impact of the quality of overhearing links (OLs) on the decoding results of the desired signals at the targeted destinations is negligible. However, in practical wireless environments, the network throughput of the ANC scheme may not be doubled and may be even worse than that of a conventional amplify-and-forward (AF) relaying scheme due to poor channel quality of the OLs. In this paper, we investigate the impact of the channel quality of OLs on the power allocation strategy and relay location to improve the sum rate.