Abstract
In this paper, we propose a multi-dimensional sparse-coded ambient backscatter communication (MSC-AmBC) system for long-range and high-rate massive Internet of things (IoT) networks. We utilize the characteristics of the ambient sources employing orthogonal frequency division multiplexing (OFDM) modulation to mitigate strong direct-link interference and improve signal detection of AmBC at the reader. Also, utilization of the sparsity originated from the duty-cycling operation of batteryless RF tags is proposed to increase the dimension of signal space of backscatter signals to achieve either diversity or multiplexing gains in AmBC. We propose optimal constellation mapping and reflection coefficient projection and expansion methods to effectively construct multi-dimensional constellation for high-order backscatter modulation while guaranteeing sufficient energy harvesting opportunities at these tags. Simulation results confirm the feasibility of the long-range and high-rate AmBC in massive IoT networks where a huge number of active ambient sources and passive RF tags coexist.
Highlights
In ambient backscatter communication (AmBC), batteryless tags utilize ambient radio frequency (RF) signals emitted from various RF sources including TV [1,2], Wi-Fi [3] or long-term evolution (LTE)signals for harvesting energy and transmitting data to the reader nearby such as smartphones [4].due to lack of coordination among the RF sources, tags and the reader, the AmBC system suffers low connectivity caused by limitations on channel as well as hardware
The weak ambient backscatter signals are vulnerable to various kinds of interferences such as direct-link interference (DLI) [2,11,12] from strong ambient sources and multiple access interference (MAI) [9,13] when concurrent backscatter transmissions are considered for non-orthogonal multiple access (NOMA)
We first provide a brief comparison of the TDMA-based AmBC (TD-AmBC) and the MSC-AmBC, and describe practical simulation environments reflecting massive Internet of things (IoT) networks with orthogonal frequency division multiplexing (OFDM) carriers
Summary
In ambient backscatter communication (AmBC), batteryless tags utilize ambient radio frequency (RF) signals emitted from various RF sources including TV [1,2], Wi-Fi [3] or long-term evolution (LTE)signals for harvesting energy and transmitting data to the reader nearby such as smartphones [4].due to lack of coordination among the RF sources, tags and the reader, the AmBC system suffers low connectivity caused by limitations on channel as well as hardware. In ambient backscatter communication (AmBC), batteryless tags utilize ambient radio frequency (RF) signals emitted from various RF sources including TV [1,2], Wi-Fi [3] or long-term evolution (LTE). Signals for harvesting energy and transmitting data to the reader nearby such as smartphones [4]. Due to lack of coordination among the RF sources, tags and the reader, the AmBC system suffers low connectivity caused by limitations on channel as well as hardware. The weak ambient backscatter signals are vulnerable to various kinds of interferences such as direct-link interference (DLI) [2,11,12] from strong ambient sources and multiple access interference (MAI) [9,13] when concurrent backscatter transmissions are considered for non-orthogonal multiple access (NOMA). To eliminate the DLI, successive interference cancellation (SIC)-based receiver structure can be considered [3,11,12] to resolve error floor problem in bit-error rate (BER) curves caused by the DLI, but they are only feasible for a local area network (LAN) scenario where a single tag Energies 2018, 11, 2855; doi:10.3390/en11102855 www.mdpi.com/journal/energies
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