  There is the long-standing assumption that radio communication in the range
of hundreds of meters needs to consume mWs of power at the transmitting device.
In this paper, we demonstrate that this is not necessarily the case for some
devices equipped with backscatter radios. We present LoRea an architecture
consisting of a tag, a reader and multiple carrier generators that overcomes
the power, cost and range limitations of existing systems such as Computational
Radio Frequency Identification~(CRFID). LoRea achieves this by: First,
generating narrow-band backscatter transmissions that improve receiver
sensitivity. Second, mitigating self-interference without the complex designs
employed on RFID readers by keeping carrier signal and backscattered signal
apart in frequency. Finally, decoupling carrier generation from the reader and
using devices such as WiFi routers and sensor nodes as a source of the carrier
signal. An off-the-shelf implementation of LoRea costs 70 USD, a drastic
reduction in price considering commercial RFID readers cost 2000 USD. LoRea's
range scales with the carrier strength, and proximity to the carrier source and
achieves a maximum range of 3.4 kilometre when the tag is located at 1 meter
distance from a 28 dBm carrier source while consuming 70 microwatts at the tag.
When the tag is equidistant from the carrier source and the receiver, we can
communicate upto 75 meter, a significant improvement over existing RFID
readers.
