Resource Allocations for Symbiotic Radio With Finite Blocklength Backscatter Link

Abstract

This paper exploits a generic downlink symbiotic radio (SR) system, where a Base Station (BS) establishes a direct (primary) link with a receiver having an integrated backscatter device (BD). In order to accurately measure the backscatter link, the backscattered signal packets are designed to have finite blocklength. As such, the backscatter link in this SR system employs the finite block-length channel codes. According to different types of the backscatter symbol period and transmission rate, we investigate the non-cooperative and cooperative SR (i.e., NSR and CSR) systems, and derive their average achievable rate of the direct and backscatter links, respectively. We formulate two optimization problems, i.e., transmit power minimization and energy efficiency maximization. Due to the non-convex property of these formulated optimization problems, the semidefinite programming (SDP) relaxation and the successive convex approximation (SCA) are considered to design the transmit beamforming vector. Moreover, a low-complexity transmit beamforming structure is constructed to reduce the computational complexity of the SDP relaxed solution. Finally, the simulation results are demonstrated to validate the proposed schemes.Index Terms-Symbiotic radio (SR), backscatter, finite blocklength channel codes, semi-definite programming (SDP), successive convex approximation (SCA)

Symbiotic Radio: Cognitive Backscattering Communications for Future Wireless Networks

“…By solving these optimization problems, the proposed SR not only enables the opportunistic transmission for the secondary system, but also enhances the primary transmission by properly exploiting the additional signal path provided by the secondary transmission. Moreover, the achievable rate of STx in finite block-length regime is considered in [57] and both of transmit power minimization and energy efficiency maximization optimization problems under the achievable throughput constraints are formulated to design the beamforming vector at the PTx.…”

Energy Efficiency Maximization for Symbiotic Radio Networks With Multiple Backscatter Devices

“…where W is the channel bandwidth. Assuming that the primary signal is perfectly removed from y(n) (1) by SIC [2], [16], [17], [18], [19], we have…”

“…Following [2], [16], [17], [18], [19], when γ s i → +∞, the expected throughput of the PT-PR link in a time block is given by…”

“…Since E|s(n)| 2 = 1, the symbol c i (l) can be decoded by performing maximal ratio combing (MRC) of y (n) (2) , n = 1, • • • , N , received in N consecutive primary symbol periods, and the throughput of BD i in the ith time slot can be approximately calculated as [2], [16], [17], [18], [19]…”

“…In [18], the PT transmission power was minimized by jointly designing the beamforming vector at the PT and the power splitting factor at the full-duplex BD, while guaranteeing the minimum BD rate requirement. The authors in [19] maximized the system EE subject to the throughput requirements of the direct and backscatter links as well as the PT transmit power constraint, by optimizing the PT beamforming vectors in an SR system with a finite block length backscatter link. Nevertheless, the above works considered only a single BD while ignoring the energy harvesting (EH) ability of the BD.…”