Backscatter Directional Modulation Communication Using Time Modulated Van-Atta Arrays

The data transmission security and power consumption are the main challenges for Internet of Things (IoT) devices. Backscatter directional modulation (DM) techniques have emerged as a promising approach for secure, ultra-low-power wireless communication in IoT applications. However, the reported backscatter DM transmitters can only establish secure wireless links in free space oriented towards the direction of the radio frequency (RF) sources. Consequently, the confidential information transmitted to legitimate users in other directions might be at risk of eavesdropping. To address this issue, this paper introduces a backscatter DM transmitter utilizing a time-modulated Van-Atta array, which can synthesize DM symbols for both multiple access and broadcasting applications. Compared with conventional broadcasting communication schemes, the proposed scheme can secure information along the users' directions and the higher-order modulation schemes can be flexibly controlled to synthesize backscatter symbols, enabling high data rate broadcasting communication. The efficacy of the proposed backscatter DM scheme in different application scenarios is demonstrated through bit-error-rate (BER) analysis at the user receivers.