Energy-Efficient Paging for Duty-Cycled LTE Backscatter

Benefiting from the continuous and ubiquitous transmission from LTE base stations (eNodeBs), LTE backscatter is more efficient and reliable than traditional backscatter operating in ISM bands. However, ISM bands can utilize intermittent signals to synchronize low-duty cycle backscatter and receivers, a mechanism not available in LTE due to its continuous transmission. Consequently, LTE backscatter and receivers (UE) may not have overlapping operational periods, making it possible that the UE might never receive the backscattered data. To solve this issue, we use LTE-standard paging, one of the LTE power management mechanisms, to wake up the receiver and allow it and the tag to maintain a consistent sleep-wake schedule. Following LTE messages, our tag employs a new low-power state machine to accommodate different phases of the UE. We prototype PScatter using FPGAs, SDR eNodeBs, and UEs. Extensive results show that PScatter supports the paging mechanism similarly to active LTE devices and achieves better energy efficiency and more effective transmission than prior LTE backscatter. It consumes 21x lower power than active LTE radios for paging decoding. For end-to-end, PScatter achieves more than 6.7x better energy efficiency than previously reported LScatter+. Moreover, PScatter delivers an effective transmission ratio of up to 100%.