In this paper, we propose a distributed Alamouti

space-time code (DASTC) for two-way relay networks employing

a single amplify-and-forward (AF) relay. We first derive closedform

expressions for the approximated average sum-rate of

the proposed DASTC scheme. Our analysis is validated by

a comparison against the results of Monte-Carlo simulations.

Numerical results verify the effectiveness of our proposed scheme

over the conventional DASTC with one-way communication.