OrthZig: Concurrent Transmissions Based on Waveform Orthogonality in ZigBee

As one of the key technologies in the Internet of Things (IoT), Zigbee is widely used in industrial, agricultural, or medical scenarios due to its short distance, low delay, and high reliability of communications. However, the intensive deployment and concurrent transmissions of devices in ZigBee networks lead to severe collision and interference, reducing the throughput of the entire wireless network. Effective collision resolutions have been explored in the literature, but most of them use chip sequence as unit to decompose collision through waveform comparison and subtraction, which will cause issues such as error propagation, bit errors due to scarce samples, and high computational complexity. To make up for the above deficiencies, we propose a new physical layer design called OrthZig to achieve high-precision collision resolution in ZigBee networks without central controller. The key idea of OrthZig is to utilize the Direct Sequence Spread Spectrum adopted by ZigBee physical layer to achieve concurrent transmissions of multiple users based on the orthogonality of signal waveforms and distributed coordination. Additionally, we reduce the requirement for synchronization accuracy by partitioning the sync pair in the spread sequence, ensuring orthogonality for correct decoding. Extensive simulations are conducted from multiple dimensions to simulate the overall performance. Evaluation results demonstrate that OrthZig has lower average bit error rate and higher network throughput than the state-of-the-art.