Symbiotic Radio: A New Communication Paradigm for Passive Internet of Things

Abstract

In this paper, a novel technique, called symbiotic radio (SR), is proposed for passive Internetof-Things (IoT), in which a backscatter device (BD) is integrated with a primary transmission. The primary transmitter is designed to assist the primary and BD transmissions, and the primary receiver decodes the information from the primary transmitter as well as the BD. We consider a multiple-input single-output (MISO) SR and the symbol period for BD transmission is designed to be either the same as or much longer than that of the primary system, resulting in parasitic or commensal relationship between the primary and BD transmissions. We first derive the achievable rates for the primary system and the BD transmission. Then, we formulate two transmit beamforming optimization problems, i.e., the weighted sum-rate maximization problem and the transmit power minimization problem, and solve these non-convex problems by applying semi-definite relaxation technique. In addition, a novel transmit beamforming structure is proposed to reduce the computational complexity of the solutions. Simulation results show that when the BD transmission rate is properly designed, the proposed SR not only enables the opportunistic transmission for the BD via energy-efficient passive backscattering, but also enhances the achievable rate of the primary system by properly exploiting the additional signal path from the BD. This paper has been presented in part at

Resource Allocations for Symbiotic Radio With Finite Blocklength Backscatter Link

“…Practically, we can employ a two-step training-based channel estimation to obtain the CSI [2]. Specifically, the BD first turns its impedance into the matched state, where the BS adopts the channel reciprocity for the channel estimation of h. Then, the BD places its impedance into the backscatter state, where the backscatter channel f * g can be obtained via extracting the estimated direct channel h from the the estimated composite channel h + f * g [2]. In the n-th symbol period, we denote s u (n) ∼ CN (0, 1) as the transmitted signal from the BS during symbol period T u .…”

“…It leads to the fact that the devices in an IoT network cannot always connect with the IoT server over long time period and the fact that for most IoT applications, such as those enabling the smart city, the device life cycle is 10 to 20 years or more, which poses extremely demanding battery life constraints. Thus, energy efficiency and radio spectrum resource has been main challenges in IoT networks [1], [2].…”

“…Ambient backscatter communication (AmBC) were proposed to fix the energy-constrained issue in IoT networks, where a passive backscatter device (BD) carries on ambient radio frequency (RF) signals (i.e., cellular, WiFi, and TV signals) via modulating its own information [3]. This technique is different from the conventional IoT devices, which utilize active RF components, i.e., converters and oscillators, etc., leading to high cost and energy consumption [2]. The passive BD yields a great reduction of the energy consumption at the IoT network since no active RF components are required at the IoT device [4].…”

“…However, the backscatter link in AmBC is vulnerable to the interference from the direct link due to inefficient utilization in spectrum such that the backscatter transmission may suffer from a performance degradation [5]. In order to circumvent this problem, symbiotic radio (SR) can be considered as a promising solution, which is based on a cooperative AmBC system and aims to integrate the BD with a direct transmission [2], [6]. Unlike the aforementioned traditional AmBC systems, the direct link is also known as the primary link, which shares the radio spectrum with the backscatter link such that the receiver simultaneously decodes the messages from the transmitter and the BD.…”

“…Unlike the aforementioned traditional AmBC systems, the direct link is also known as the primary link, which shares the radio spectrum with the backscatter link such that the receiver simultaneously decodes the messages from the transmitter and the BD. Radio frequency identification (RFID), one typical backscatter communication system is a good application in a IoT network [2], [7]. The BDs in the IoT setup evolves the active Bluetooth or LoRa devices to collect the information transmitted from the BDs by aligning the frequency of the original signal emitted by the transmitter [8], [9].…”