Leveraging interleaved signal edges for concurrent backscatter

One of the central challenges in backscatter is how to enable concurrent transmissions. Most backscatter protocols operate in a sequential TDMA-like manner due to the fact that most nodes cannot overhear each other's transmissions, which is detrimental for throughout and energy consumption. Recent efforts to separate concurrent signals by inverting a system of linear equations is also problematic due to varying channel coefficients caused by system and environmental dynamics. In this paper, we introduce BST, a novel physical layer for backscatter communication that enables concurrent transmission by leveraging intra-bit multiplexing of OOK signals from multiple tags. The key idea underlying BST is that the reader can sample at considerably higher rates than the tags, hence it can extract time-domain signal edges that result from interleaved transmissions of several tags. Our preliminary experiment results show that BST can achieve 5× the throughput of Buzz and 10× the throughput of TDMA-based solutions, such as EPC Gen 2.