Said Benaissa

Characterization of the On-Body Path Loss at 2.45 GHz and Energy Efficient WBAN Design for Dairy Cows

Wireless body area networks (WBANs) provide promising applications in the healthcare monitoring of dairy cows. The characterization of the path loss (PL) between on-body nodes constitutes an important step in the deployment of a WBAN. In this paper, the PL between nodes placed on the body of a dairy cow was determined at 2.45 GHz. Finite-difference time domain simulations with two half-wavelength dipoles placed 20 mm above a cow model were performed using a 3-D electromagnetic solver. Measurements were conducted on a live cow to validate the simulation results. Excellent agreement between measurements and simulations was achieved and the obtained PL values as a function of the transmitter-receiver separation were well fitted by a lognormal PL model with a PL exponent of 3.1 and a PL at reference distance (10 cm) of 44 dB. As an application, the packet error rate (PER) and the energy efficiency of different WBAN topologies for dairy cows (i.e., single-hop, multihop, and cooperative networks) were investigated. The analysis results revealed that exploiting multihop and cooperative communication schemes decrease the PER and increase the optimal payload packet size. The analysis results revealed that exploiting multihop and cooperative communication schemes increase the optimal payload packet size and improve the energy efficiency by 30%.

Experimental characterisation of the off-body wireless channel at 2.4GHz for dairy cows in barns and pastures

Off-body path loss in indoor (barn) and outdoor (pasture) environments.Path loss was well fitted by a one-slope log-normal model.Cow body shadowing presented maximum value of 7dB.Temporal fading can be described by a Ricean distribution in the considered environments. Wireless Sensor Networks (WSNs) provide promising applications in healthcare monitoring of dairy cows. After sensors measure the data in or on the cows body (temperature, position, leg movement), this information needs to be transmitted to the farm manager, enabling the evaluation of the health state of the cow. In this work, the off-body wireless channel between a node placed on the cows body and an access point positioned in the surroundings of the cows is characterised at 2.4GHz. This characterisation is of critical importance in the design of reliable WSNs operating in the industrial, scientific and medical (ISM) band (e.g., Wi-Fi, ZigBee, and Bluetooth). Two propagation environments were investigated: indoor (inside three barns) and outdoor (pasture). Large-scale fading, cow body shadowing, and temporal fading measurements were determined using ZigBee motes and spectrum analysis measurement. The path loss was well fitted by a one-slope log-normal model, the cow body shadowing values increased when the height of the transmitter and/or the receiver decreased, with a maximum value of 7dB, and the temporal fading due to the cow movement was well described by a Rician distribution in the considered environments. As an application, a network planning tool was used to optimise the number of access points, their locations, and their power inside the investigated barns based on the obtained off-body wireless channel characteristics. Power consumption analysis of the on-cow node was performed to estimate its battery lifetime, which is a key factor for successful WSN deployment.

Numerical assessment of EMF exposure of a cow to a wireless power transfer system for dairy cattle

Abstract In this paper, we assessed the exposure of a cow to the electromagnetic fields (EMFs) induced by a wireless power transfer (WPT) system working at 92 kHz in a dairy barn. Cow exposure to the radiated EMFs was evaluated and compared to safety guidelines. We modeled a realistic WPT system for dairy cows in Sim4Life, a 3D electromagnetic simulation tool. We validated the model with electric field measurements; simulated fields deviated on average 6% from measured fields. We used the proposed WPT model to evaluate the stimulation and thermal effects based on the internal electric field and the specific absorption rate (SAR), respectively. Results showed that the exposure mainly varied with the distance of the transmitter to the body: variation of 5 dB of the induced electric field when the transmitter was set at 20 cm and 10 cm from the body. The distance of the receiver to the body influenced the exposure less (10%). We also compared the exposure with the limits provided by the International Commission on Non-Ionizing Radiation Protection (ICNIRP). The internal electric fields were more conservative than SAR, which showed values far below exposure limits.