A general algorithm for interference alignment and cancellation in wireless networks

Physical layer techniques have come a long way and can achieve close to Shannon capacity for single point to-point transmissions. It is apparent that, to further improve network capacity significantly, we have to resort to concurrent transmissions. Multiple concurrent transmission techniques (e.g., zero forcing, interference alignment and distributed MIMO) are proposed in which multiple senders jointly encode signals to multiple receivers so that interference is aligned or canceled and each receiver is able to decode its desired information. In this paper, we formulate the interference alignment and cancellation problem in multi-hop mesh networks. We show that the problem is NP-hard in general. We then propose a convex programming based algorithm to identify interference alignment and cancellation opportunities. Our algorithm effectively utilizes knowledge of both local network topology and overheard packets at the sender side as well as the receiver side. We implement our system using GNU Radio to evaluate key practical implementation issues.