Symbiotic radio (SR) has emerged as a spectrum- and energy-efficient paradigm to support massive Internet of Things (IoT) connections. Two multiple access schemes are proposed in this paper to facilitate the massive IoT connections using the cellular network based on the SR technique, namely, the simultaneous access (SA) scheme and the selection diversity access (SDA) scheme. In the SA scheme, the base station (BS) transmits information to the receiver while multiple IoT devices transmit their information simultaneously by passively backscattering the BS signal to the receiver, while in the SDA scheme, only the IoT device with the strongest backscatter link transmits information to the receiver. In both of the schemes, the receiver jointly decodes the information from the BS and the IoT devices. To evaluate the above two schemes, in this paper, we have derived the closed-form expressions of the ergodic rates and the outage probabilities for the cellular and IoT transmissions. Finally, numerical results are provided to verify the theoretical analysis and compare the two proposed multiple access schemes. When the number of IoT devices is small, the SDA scheme is more appealing since it can significantly reduce the computational complexity while achieving equivalent performance to the SA scheme. When the number of IoT devices is large, the SA scheme is preferable since it guarantees a significantly better rate performance and a lower outage probability.

翻译：共生无线电（SR）已成为一种支持大规模物联网（IoT）连接的频谱和能量高效范式。本文基于SR技术提出了两种多址接入方案，以利用蜂窝网络促进大规模IoT连接，即同时接入（SA）方案和选择分集接入（SDA）方案。在SA方案中，基站（BS）向接收器传输信息，同时多个IoT设备通过被动反向散射BS信号向接收器发送各自的信息；而在SDA方案中，仅具有最强反向散射链路的IoT设备向接收器传输信息。在这两种方案中，接收器联合解码来自BS和IoT设备的信息。为评估上述两种方案，本文推导了蜂窝和IoT传输的遍历速率和中断概率的闭式表达式。最后，通过数值结果验证了理论分析，并比较了所提出的两种多址接入方案。当IoT设备数量较少时，SDA方案更具吸引力，因为它能在实现与SA方案等效性能的同时显著降低计算复杂度。当IoT设备数量较多时，SA方案更优，因为它能保证显著更优的速率性能和更低的中断概率。