Encoding Scheme to Reduce Energy Consumption of Delivering Data in Radio Frequency Powered Battery-Free Wireless Sensor Networks

Abstract

Wireless sensor networks (WSNs) have been widely deployed in intelligent transportation systems. Battery-free WSN (BF-WSN) scavenges energy from the environment. In the BF-WSN, whose nodes harvest radio frequency (RF) energy, delivering data with low energy consumption is important for the BF-WSN nodes to have a longer runtime. Some existing baseband encoding or carrier-modulation schemes exhibit the energy consumption disparity (ECD) between transmitting bit 0 and bit 1. An example is FM0 (bi-phase space) baseband encoding, which is widely applied in the backscattering communications in radio frequency identification systems and wireless identification sensing platform. With FM0, transmitting bit 0 consumes much greater energy than bit 1. To achieve energy-saving in delivering data with the ECD, we, in this paper, formulate the optimization problem (OP) that maximizes percentage of energy saving. The solution of the OP leads to the optimal energy-efficient codebook. Based on the derived codebook, we present the energy-efficient data delivery scheme (EEDDS), with which the sender transmits the codewords in the codebook and the receiver recovers the corresponding original data blocks using the codebook. Simulation results show that the proposed EEDDS outperforms the traditional data delivery scheme in terms of energy consumption in the case when the applied baseband encoding or carrier-modulation schemes occupy the ECD.