Collision resolution based on pulse shape diversity

A two-user wireless uplink scenario is considered, in which the users transmit simultaneously over the same channel. In the networking literature the result of such transmission is referred to as collision. It has been recently shown that small user delays and carrier frequency offsets (CFO) between the users allow for blind collision resolution based on the measurements of a single receive antenna. This is achieved by oversampling the collision signal, and exploiting the information on the collided packets that is contained in the signal´s polyphase components. In this paper, user pulse-shape diversity is investigated for separating collided users even when delays and CFOs are small. In particular, an iterative pulse shape design is proposed that enforces several desirable characteristics to each user´s pulse shape function. The proposed approach is tested on a software defined radio testbed and also via simulations. Both simulations and testbed evaluation suggest that the proposed approach can be very successful in resolving the users under realistic signal-to-noise ratio scenarios. Resolving collisions can significantly improve throughput in wireless networks.