EchScatter: Enriching Codeword Translation for High-Throughput Ambient ZigBee Backscatter

We present EchScatter, a novel backscatter system that takes productive ZigBee signals as excitations and enables high-throughput ZigBee backscatter communication. Compared with the existing ZigBee backscatter, EchScatter does not need to control the carrier, ensuring the universality of the transmitter. EchScatter has realized chip-level modulation of productive ambient ZigBee backscatter for the first time. It is capable of transmitting more tag bits simultaneously, thus increasing the throughput of the system. We first design 16 different 32-chip phase modulation sequences to realize the translation of any two ZigBee symbols. Therefore, our system can transmit four tag bits through one symbol. After that, we use an average energy detection-based synchronization method to make sure the synchronization error of the EchScatter meets the requirements of chip-level modulation. We prototyped EchScatter using an off-the-shelf FPGA and commodity ZigBee transceivers. Through extensive experiments and field studies, we show that EchScatter can work universally on commodity ZigBee transceivers. In line-of-sight and non-line-of-sight scenarios, EchScatter is able to achieve 247 kbps and 245 kbps throughput at a signal strength of around -60 dBm, respectively. The throughput of EchScatter is 32 times higher than that of FreeRider. We believe it will have more pervasive applications.