Zero Correlation Zone Codes Based Multiple Access for Ambient Backscatter Communications

Backscatter communications and ambient Internet of Things (AIoT) arouse wide interest recently. One open challenge for AIoT is the multiple access for various tags. Traditional solution is Code division multiple access (CDMA) methods that encode different users with mutually orthogonal code sequences to avoid interference from multiple reflected signals. However, for AIoT, the presence of varying transmission delays among tags destroys the orthogonality between the coded sequences. To address this challenge, we propose a multi-user access method based on zero correlation zone (ZCZ) codes. Specifically, we first construct new ZCZ sequences through interleaving different versions of offset sequences. Next, we use the orthogonality of ZCZ sequences to eliminate interference among multiple reflected signals, even when there is a certain access time interval between users. Finally, we compares the performance of our method with that of the traditional CDMA schemes. Our simulation results confirm the feasibility and effectiveness of the our proposed multiple access scheme based on ZCZ codes.