Enhanced Capacity for Multi-Tag Concurrent Backscatter Communication Systems under Spectrum Constraints

Passive backscatter communication technology, due to its microwatt-level power consumption, makes IoT devices easy to be deployed and maintenance-free. The multi-tag concurrent communication technology enables tags to avoid complex protocols such as collision avoidance, thus reducing device power consumption while increasing the system throughput and scale. However, the limited spectrum resources available to backscatter tags lead to issues of mutual interference and low spectrum utilization in multi-tag concurrency. To this end, we propose CamScatter, a capacity-enhanced multi-tag parallel backscatter communication system. We design strategies for maximizing channel division and efficient allocation with limited spectrum resources, avoiding interference among tags, and significantly enhancing the system capacity. In the preprocessing phase, a bandwidth-maximized channel division algorithm is proposed, providing multiple interference-free channel division schemes for system communication. In the initialization phase, an optimized channel and rate allocation scheme is proposed, assigning the most suitable channels and rates to tags based on the signal-to-noise ratio (SNR) of all tags in the system, thereby mitigating signal interference caused by tag energy differences and improving system throughput. Additionally, during system working, it uses sideband aggregation and matched filtering techniques to enhance signals strength of the tags to be demodulated, reducing interference from other tags. The bandwidth range that this system utilizes is from 142.4 kHz to 773.5 kHz. Due to harmonic interference limitations, the theoretical maximum spectrum utilization rate is 81.1%, and the maximum system capacity without interference is 2925 kbps. Extensive simulation experiments indicate that the algorithm proposed in this paper can achieve a spectrum utilization rate of 78.6%, with a maximum system capacity of up to 1914 kbps. Actual deployment experiments verify that our system CamScatter supports a maximum throughput of 305 kbps and can handle concurrent communication with up to 30 tags, effectively resolving the issue of mutual interference between tags.