Integrated sensor nodes with GSM modems simplify the task of wireless data acquisition

January 11, 2012 // By Ajay Bharadwaj and Balaji Mamidala
A sensor network typically consists of a number of sensor nodes which each acquire signals from a sensor or multiple sensors and a system to transmit and process the data acquired from sensors. The sensor nodes can communicate the data within one another or to a centralized location over a wired or wireless network.

The sensor network can thus be classified as a data acquisition network and data distribution network. The data acquisition system typically consists of sensors and circuitry to handle the real-world information available and the data distribution network involves the communication protocols, network topology, and methodology to transmit and handle the data. The basic network topologies used are star, ring, bus, and mesh, as shown in figure 1.

Figure 1: Various network topologies. Click image to enlarge.

The choice of the sensor network topology depends upon the application and the kind of processing and data handling required. The need for improving connectivity from PCs to the real world is gaining momentum. There are a many sensors and actuators in use, and interconnecting them by integrating the data available is becoming a necessity. The numbers of nodes in a sensor network continues to increase and wired connectivity is often not an option since sensors must be placed in remote locations. The cost per node is also decreasing, enabling wider reach of sensor nodes. There are also many improvements in low power radio technologies which can be used to design more efficient systems.

Wireless networks also offer better scalability compared to wired networks and deploying a new node in a wireless network is easier. Sensor networks need to balance performance versus the lifetime of the sensor node. Wireless nodes can be configured dynamically to balance this tradeoff, as well as operate autonomously to permit local control of operation and power management. A number of wireless protocols can be considered for sensor networks namely Zigbee, Bluetooth, GSM, Wi-Fi, etc. The choice of wireless protocol depends upon the application needs for the sensor network.


Low power capability

Wireless sensor nodes require very little maintenance and must run for days and sometimes months using the same battery. Thus, low power design is critical for the design of real-world wireless sensor networks, and it is a primary

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