1 research outputs found
Joint Orthogonal Band and Power Allocation for Energy Fairness in WPT System with Nonlinear Logarithmic Energy Harvesting Model
Wireless power transmission (WPT) is expected to play an important role in
the Internet of Things services by providing the perpetual operation of IoT
sensors. However, to prolong the IoT network's lifetime, the efficient resource
allocation algorithm is required, in particular, the energy fairness issue
among IoT sensors has been a critical challenge of the WPT system. In this
paper, considering energy fairness as the minimum received energy of all energy
poverty IoT sensors (EPISs), we allocate orthogonal frequency bands to several
EPISs and transfer the RF power on each orthogonal band, using energy
beamforming. Based on the energy poverty, we propose orthogonal frequency bands
assignment rule, granting the priority to the EPISs with less received energy.
We also formulate two transmission power allocation problems, incorporated the
nonlinear logarithm-energy harvesting (EH) model. First, the total received
power maximization (TRPM) problem is presented and solved by combining the
well-known Karush-Kuhn-Tucker (KKT) conditions with the modified water-filling
algorithm. Second, the common received power maximization (CRPM) problem is
formulated and the optimal solution is derived using the iterative bisection
search method. To apply the bisection search method to the problem, this paper
proposes a method of specifying the scope of the solution for the objective
function defined by the sum of monotonous functions. In numerical results,
assuming the mobility of EPISs by the one-dimensional random walk model, the
effectiveness of the mobility of EPISs on the minimum received energy of all
EPISs is presented. Finally, the performance of the proposed resource
allocation schemes is verified by comparing other resources allocation schemes,
such as Round robin and equal power distributionComment: 12 pages, 27 figure