Backscatter communication offers a promising solution to connect massive Internet-of-Things (IoT) devices with low cost and high energy efficiency. Nevertheless, its inherently passive nature limits transmission reliability, thereby hindering improvements in communication range and data rate. To overcome these challenges, we introduce a bistatic broadband backscatter communication (BBBC) system, which equips the backscatter device (BD) with multiple antennas. In the proposed BBBC system, a radio frequency (RF) source directs a sinusoidal signal to the BD, facilitating single-carrier block transmission at the BD. Meanwhile, without requiring channel state information (CSI), cyclic delay diversity (CDD) is employed at the multi-antenna BD to enhance transmission reliability through additional cyclically delayed backscattered signals. We also propose a receiver design that includes preprocessing of the time-domain received signal, pilot-based parameter estimation, and frequency-domain equalization, enabling low-complexity detection of the backscattered signal. Leveraging the matched filter bound (MFB), we analyze the achievable diversity gains in terms of outage probability. Our analysis reveals that spatial diversity is achievable under general Rayleigh fading conditions, and both frequency and spatial diversity are attainable in scenarios where the forward link experiences a line-of-sight (LoS) channel. Simulation results validate the effectiveness of the proposed BBBC system. As the number of BD antennas increases, our results show that the proposed scheme not only enhances array gain but also improves diversity order, significantly reducing both outage probability and bit error rate (BER). Consequently, it outperforms conventional schemes that yield only minor gains.

翻译：反向散射通信为连接大规模物联网设备提供了一种具有低成本和高能效前景的解决方案。然而，其固有的被动特性限制了传输可靠性，从而阻碍了通信距离和数据速率的提升。为克服这些挑战，我们提出了一种双基地宽带反向散射通信系统，该系统为反向散射设备配备了多天线。在所提出的BBBC系统中，射频源向BD发送正弦信号，以支持BD实现单载波块传输。同时，多天线BD在无需信道状态信息的情况下，采用循环延迟分集技术，通过附加的循环延迟反向散射信号来增强传输可靠性。我们还提出了一种接收机设计方案，包括对时域接收信号的预处理、基于导频的参数估计以及频域均衡，从而能够以低复杂度检测反向散射信号。利用匹配滤波界，我们从中断概率的角度分析了可实现的分集增益。分析表明，在一般瑞利衰落条件下可实现空间分集，而在前向链路经历视距信道的场景中，频率分集和空间分集均可实现。仿真结果验证了所提出的BBBC系统的有效性。随着BD天线数量的增加，我们的结果表明，所提方案不仅增强了阵列增益，还提高了分集阶数，显著降低了中断概率和误码率。因此，其性能优于仅能产生微小增益的传统方案。