Enabling OFDMA in Wireless Backscatter

Wireless backscatter communication can provide ultra-low power backhaul to Internet-of-Things (IoT) devices, which usually have very limited energy budgets. With proliferation of IoT widgets into human activities, an important design goal for the backhaul is to connect as many devices as possible, which are featured by short bursts of data. The crux to achieve this goal is to enhance concurrency of the wireless backscatter network, so that many concurrent transmissions can be supported. Orthogonal frequency division multiple access (OFDMA) is a multiple access mechanism based on orthogonal frequency division multiplexing (OFDM), which is a multi-carrier modulation mechanism widely used in modern wireless systems including 802.11 a/g/n/ac, 4G and 5G. This talk focuses on how to enable OFDMA in the wireless backscatter network, which not only maintains the advantage of ultra-low power consumption but also improve the system concurrency. The major challenge for enabling OFDMA in wireless backscatter is to achieve the strict synchronization in both time and frequency domain. In fact, the synchronization is critical for all the OFDMA systems; however, in the OFDMA backscatter network, the signal at the receiver side is reflected from backscattering devices (tags), thus introduce more opportunities for offsets in both time and frequency domain, which incurs new challenges in the system design. This talk presents the major challenges in realizing OFDMA backscatter network, and provide our solutions to deal with those problems. The design for excitation signal transmitter, tag and receiver will be explained. The phenomena we observed in realizing the system will be illustrated. Moreover, the new issues discovered in existing OFDMA backscatter is to be revealed, and the preliminary result for the future work is also to be presented.