Optimisation of Radiation Beam in Linear Nodes Array of Wireless Sensor Network for Improved Performance

Introduction

Wireless sensor networks (WSN) is a new monitoring and control capability for applications such as precision agricultural (to monitor the pesticides level in the drinking water; to check the air pollution in real time); industrial (transportation; health care; managing inventory; monitoring product quality) (Akylidiz, et al., 2002) and in military for surveillance, reconnaissance, and combat scenarios (Chen, et al., 2002). A representation of sensor network communication architecture is depicted in Figure 1.

Figure 1.

Sensor networks communication architecture (Akylidiz, et al., 2002)

WSN is a compact system that combines microsensor technology and low-power signal processing, computation, and low-cost wireless networking. It represents a significant improvement over traditional sensors, networks and wireless communications. There are large numbers of small sensor nodes being deployed over an area. The sensor nodes are small, with limited processing and computing resources, and inexpensive devices. The nodes can sense various physical attributes such as temperature, light, humidity, velocity, and magnetic field. The nodes then measure, and collect desired information from the area of interest. Based on some local analyzing and processing, they will establish communication and transmit the sensed data to the end user for further analysis as shown in Figure 1.

The sensor nodes in WSN are low power devices equipped with one or more sensors, a processor, a transceiver and a power supply that typically use the battery as the power source. Since the sensor nodes have limited memory and usually deployed in hazardous areas, a transceiver is implemented for wireless communication to transfer the data to the base station. The battery is the main power source in the sensor node. It has very restricted lifetime thus contributes to the issues of restricted communication limited memory and computing capabilities (Chen, et al., 2002). Consequently, the sensors should be designed to be smaller, cheaper, intelligent and highly energy efficient. At the same time, the sensors should be efficient in terms of transmitted power and coding in order to reduce any unnecessary extra transmission power and to improve the overall system performance.

WSN has its own design and resource constraints. Resource constraints include a limited amount of energy, short communication range, low bandwidth, and limited processing and storage in each node (Culler, et al., 2004). Obstruction in the environment can also limit communication between nodes, which in turn affects the network connectivity or topology (Yick, et al., 2008).

In order to improve the WSN’s performance, beamforming capability is integrated in all sensor nodes (Elmusrati & Hasu, 2007; Yao, et al., 1998). The sensor nodes can intelligently organise themselves to cooperate with each other, and perform a radiation beam optimisation. The radiation beam reconfiguring technology has a potential to intelligently coordinate the radiation transmission of the sensor nodes into a narrow beam, thus increases the desired transmission range.

Beamforming In Wireless Sensor Networks

Beamforming is a process of joining the signal from different antenna elements in order to come out with single output of the antenna array. It has been discussed that antenna array can improve the channel capacity and expand the range of signal’s coverage (Van Veen, & Buckley, 1988; Litva, et al., 1996). Besides, an antenna array also can overcome the multipath fading problem and then decrease the bit error rate (Godara, 1997).