Efficient and reliable low-power backscatter networks

Abstract

-There is a long-standing vision of embedding backscatter nodes like RFIDs into everyday objects to build ultralow power ubiquitous networks. A major problem that has challenged this vision is that backscatter communication is neither reliable nor efficient. Backscatter nodes cannot sense each other, and hence tend to suffer from colliding transmissions. Further, they are ineffective at adapting the bit rate to channel conditions, and thus miss opportunities to increase throughput, or transmit above capacity causing errors. This paper introduces a new approach to backscatter communication. The key idea is to treat all nodes as if they were a single virtual sender. One can then view collisions as a code across the bits transmitted by the nodes. By ensuring only a few nodes collide at any time, we make collisions act as a sparse code and decode them using a new customized compressive sensing algorithm. Further, we can make these collisions act as a rateless code to automatically adapt the bit rate to channel quality -i.e., nodes can keep colliding until the base station has collected enough collisions to decode. Results from a network of backscatter nodes communicating with a USRP backscatter base station demonstrate that the new design produces a 3.5× throughput gain, and due to its rateless code, reduces message loss rate in challenging scenarios from 50% to zero.

Energy-efficient active tag searching in large scale RFID systems

“…Generally, the existing RFID tag identification protocols can be classified into two categories [10,11]: ALOHA-based protocols [27][28][29][30] and tree-based protocols [19,31]. In ALOHA-based protocols, on average a tag needs to transmit its ID e times to the reader before being successfully identified [10,27], where e is the base of natural logarithm whose value is approximately equal to 2.72.…”

Exploiting joint sparsity in compressed sensing-based RFID

“…This bears several advantages over FSA-based schemes, as reported in, e.g., [9,14]. In particular, CS enables a quicker identification and provides an increased noise robustness.…”

“…The compressed sensing (CS)-based identification protocols [9][10][11][12][13][14], on the other hand, cope with simultaneously responding tags and exploit collisions. This bears several advantages over FSA-based schemes, as reported in, e.g., [9,14].…”

A SDR Prototype for Backscatter Sensor Networks

“…2) Since the backscattered sensor signal changes slowly and the low sensor data rate is mostly 10 bps order [21], it can reduce the power consumption of the sensor nodes and increase the transmission distance.…”