Intra-Band LTE Backscatter

Due to the continuity of long term evolution(LTE)downlink traffic,LTE signal has been considered as a promising excitation signal for ubiquitous backscatter communication.But this continuity also brings challenges in performing self-interference cancellation.Existing backscatter designs commonly use frequency shifting to move backscattered signal away from the entire excitation band to avoid self-interference.However,due to the continuity of LTE signal,LTE bands are occupied continuously.So,there is no enough white spectrum for frequency shifting.To solve this problem,we in this paper propose a novel LTE backscatter design,which can avoid self-interference without leveraging extra spectrum.Our idea is proposed based on a full understanding of the LTE resource grid,where we find that although a band is occupied by an excitation signal,there are still reserved resource elements in the traffic.We can leverage such resource elements as in-band white space to transmit backscatter signal.Meanwhile,we address the self-cancellation issue caused by double sideband modulation,and deal with the aligning issue.Our design is evaluated using a testbed of backscatter hardware and software defined radio(SDR).The results show that our system achieves a distance of 24 m for line-of-sight(LOS)transmit-to-tag communication.Besides,we demonstrate that our system can operate on off-the-shelf eNodeB.It can achieve reliable backscatter in multi-path scenarios,with a power consumption 6.3 times less than its least counterpart.