  Two-way relaying can significantly improve performance of next generation
wireless networks. However, due to its dependence on multi-node cooperation and
transmission coordination, applying this technique to a wireless network in an
effective and scalable manner poses a challenging problem. To tackle this
problem without relying on complicated scheduling or network optimization
algorithms, we propose a scalable random access scheme that takes measures in
both the physical layer and the medium access control layer. Specifically, we
propose a two-way relaying technique that supports fully asynchronous
transmission and is modulation-independent. It also assumes no priori knowledge
of channel conditions. On the top of this new physical layer technique, a
random access MAC protocol is designed to dynamically form two-way relaying
cooperation in a wireless network. To evaluate the scalable random access
scheme, both theoretical analysis and simulations are carried out. Performance
results illustrate that our scheme has achieved the goal of scalable two-way
relaying in a wireless network and significantly outperforms CSMA/CA protocol.
