Studies are geared towards the planar antenna that can be integrated with the WSN node [25–27]. WSN in-built antennas allow longtime monitoring but also provide extensive coverage in the sensor node. Most compact antennas in WSN nodes consume more power which reduces the lifetime of the node. For lower energy consumption, the antenna integrated with a node needs to operate for a longer time while consuming minimum power. Due to space constraints, the antenna also needs to be compact with acceptable gain. This indicates that the sensor nodes need highly miniaturized antennas for minimizing node complexity. The high gain antenna will consume less power in the desired direction. Therefore, the proposed antenna meets the above challenges. To validate the proposed antenna, it has been deployed in the sensor node and its performance is analyzed.
An Arduino based WSN is employed to validate the performance of the proposed antenna. Microcontroller ATmega328P and the CC2530 transceiver are chosen because of their high transmission power, size, low cost, and compatibility. Figure 10 shows the block diagram of transmitting and receiving sensor nodes with the proposed antenna. The wireless data communication is performed by using the proposed antenna as either receiving or transmitting side. The proposed antenna is attached to the sensor node instead of the default antenna on the transmission side. In destination, the in-built (internal) antenna acts as a receiver. Besides, the destination node is connected to the laptop through the UART cable. Figure 11 shows an experimental setup of the sensor node and the proposed antenna. Data exchange between the nodes occurs after configuration is complete.
To validate the proposed antenna, the RSSI value is measured as a function of time. The RSSI value of the receiver provides the signal strength of the proposed antenna (in dBm). Figure 12 compares the RSSI values of the antenna with and without EBG for each received data at a distance of 1m. It can be clearly shown that the antenna with an EBG provides more power levels than without EBG structure. Inaccurate, the EBG loaded antenna provides up to -65dBm power when compared to -70dBm for the antenna without EBG. Also, due to multipath fading and NLOS between the nodes, the RSSI value may change at any given time.
Moreover, the calculation of RSSI has been studied in both indoor and outdoor environments. The distance between nodes has an impact on RSSI value while keeping the destination node's position fixed. Figure 13 shows the relationship between RSSI and the distance of the nodes in an indoor environment. The proposed antenna gives greater power around − 70dBm at short distances.
Figure 14 shows the variation on RSSI about the distance between the node in an outdoor environment. It is shown that in comparison to long distances, the proposed antenna offers more power − 65dBm at a distance of 3m. The results show that the proposed antennas can provide satisfactory precision in both indoor and outdoor environments. The designed sensor node's position can be adjusted to the building's layout to improve the results of indoor positioning. Because buildings do not have a blocking effect in an outdoor environment, the outdoor method is even more accurate.
Sensors are mainly characterized depending on the value of their important parameters such as accuracy, response time, accuracy, sensitivity, Precision, Sensitivity, Linearity, Repeatability, etc.., Among them, some of the important parameters are analyzed. The same configuration is used to calculate the sensing parameter such as failure rate and accuracy of the sensor node. By varying the distance between the transmitting and receiving nodes, the failure rate is calculated. Figure 15 depicts the failure rate calculated by varying the distance between the transmitter and receiving nodes. In both indoor and outdoor environments, the distance between the nodes increases, and the failure rate gets increases.
The most significant parameter in sensor node analysis is accuracy, which ensures that the sensor's readings are as near as possible to the known value. Figure 16 depicts the accuracy calculation of the designed sensor node. A better accuracy value is observed in both the indoor and outdoor environments, for example, at a distance of 4 m between the sensor nodes, the accuracy value is 94% for the outdoor environment and 90% for the indoor environment is observed. In summary, the results confirm that the proposed antenna can provide good reliability and is suitable for short-range WSN applications.
The power usage depends strongly on the node's mode of operation. The average energy consumption in sleep mode is less than 10µW. In active mode, the estimated power consumption of the sensor node is 78mW while the proposed antenna loaded without an EBG structure on the transmission side. For the experiments, a proposed EBG reflector is loaded with the antenna, causing an additional power consumption of about 12mW. Table IV explains the average power consumption of the sensor node. It confirms that the proposed EBG loaded antenna provides more power consumption in both modes. In summary, the proposed antenna can provide good power consumption and is suitable for short-range communications.
TABLE IV
Average Power Consumption of the Designed Node
Mode of operation | Without EBG | With EBG |
SLEEP | 10.2µW | 10µW |
ACTIVE | 90mW | 78mW |