Efficient Ambient LoRa Backscatter With On-Off Keying Modulation

Abstract

Backscatter communication holds potential for ubiquitous and low-cost connectivity among low-power IoT devices. To avoid interference between the carrier signal and the backscatter signal, recent works propose a frequency-shifting technique to separate these two signals in the frequency domain. Such proposals, however, have to occupy the precious wireless spectrum that is already overcrowded, and increase the power, cost, and complexity of the backscatter tag. In this paper, we revisit the classic ON-OFF Keying (OOK) modulation and propose Aloba, a backscatter system that takes the ambient LoRa transmissions as the excitation and piggybacks the in-band OOK modulated signals over the LoRa transmissions. Our design enables the backsactter signal to work in the same frequency band of the carrier signal, meanwhile achieving flexible data rate at different transmission range. The key contributions of Aloba include: i) the design of a low-power backscatter tag that can pick up the ambient LoRa signals from other signals; ii) a novel decoding algorithm to demodulate both the carrier signal and the backscatter signal from their superposition. We further adopt link coding mechanism and interleave operation to enhance the reliability of backscatter signal decoding. We implement Aloba and conduct head-to-head comparison with the state-ofthe-art LoRa backscatter system PLoRa in various settings. The experiment results show Aloba can achieve 39.5-199.4 Kbps data rate at various distances, 10.4-52.4× higher than PLoRa.

A Survey of mmWave-Based Human Sensing: Technology, Platforms and Applications

“…2) Sensing over backscatter: Backscatter technology [170]- [174] has been developed rapidly in the past few years to provide communication capability for low-end devices. Compared with active radios, backscatter [175]- [180] promises to be extremely low power, smaller and cheaper alternative. As the reflected signal of the backscatter tag is affected by both the modulation information and the channel state, we can sense the target state by attaching the tag to the target and analyzing the change of the reflected signal.…”

Development in ambient backscatter communications

“…In this PLoRa scheme, we can only modulate one bit per single LoRa symbol, but the communication link distance was more than 1 km. A more recent work in 2022 [59] applies OOK on ambient LoRa signals. However, at the receiver end the authors proposed some processing approach to convert the OOK modulation in magnitude domain to frequency domain so that it became more resilient to noise and interference.…”

Cross-Technology Communication for the Internet of Things: A Survey

“…In order to achieve a more ubiquitous cross-network, cross-frequency, and cross-media communication system, there have also been a lot of cutting-edge works to open a new direction for the development of CTC. CTC enables interpreting signals from other technologies with dedicated hardware as a helper in a backscatter communication system [110][111][112]. Although a basic backscatter communication system consists of dedicated hardware, it can still be a promising alternative to connect different technologies due to its low power consumption and simplicity.…”