Abstract
Integrating ambient backscatter communications into RF-powered cognitive radio networks has been shown to be a promising method for achieving energy and spectrum efficient communications, which is very attractive for low-power or no-power communications. In such scenarios, a secondary user (SU) can operate in either transmission mode or backscatter mode. Specifically, an SU can directly transmit data if sufficient energy has been harvested (i.e., transmission mode). Or an SU can backscatter ambient signals to transmit data (i.e., backscatter mode). In this paper, we investigate the performance of such systems. Specifically, channel inversion power control and an energy store-and-reuse mechanism for secondary users are adopted for efficient use of harvested energy. We apply stochastic geometry to analyze coverage probability and achievable rates for both primary and secondary users considering both communication modes. Analytical tractable expressions are obtained. Extensive simulations are performed and the numerical results show the validity of our analysis. Furthermore, the results indicate that the performance of secondary systems can be improved with the integration of both communication modes with only limited impact on the performance of primary systems.
Highlights
In recent years, the demand for smart systems is growing fast
When performing IT, the available energy is energy harvesting (EH) − EC, but for ease of analysis, in this paper we adopt the setting that a portion ξ of the harvested energy EH can be used for active information transmission [31] and energy not used is ignored in different time slots
To generate uniformly distributed points in an annular region, we use a native method of generating a random point within a circle with radius RM, and if the random value is smaller than the inner radius Rm, the point will be generated repeatedly until it is in the annular region
Summary
The demand for smart systems (e.g., on-body sensing for e-Healthy) is growing fast. We consider the integration of ambient backscatter communications into RF-powered cognitive radio networks in a similar way to [8] In this case, these two techniques could complement each other to jointly achieve the Wireless Communications and Mobile Computing advantages while overcoming the individual shortcomings. In our cognitive radio network, the transmission of secondary transmitters falls into interweave paradigm to utilize white spaces of specific channels [9], and the needed energy is harvested from existing signals. In [19], a backscatter network is analyzed by using stochastic geometry, but dedicated power beacons are deployed to support the communication, while, in [20, 21], a single hybrid transmitter harvests energy from multiple ambient transmitters, transmits its own signal, or backscatters existing signals to a hybrid receiver, and its performance is analyzed.
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