Demo Abstract: Smart Antennas Made Practical: The SPIDA Way
Erik Öström, Luca Mottola, Martin Nilsson, Thiemo Voigt · 2010
Smart antennas are a specific type of directional antenna able to dynamically control the gain as a function of direction. This contrasts with more traditional directional antennas, where the dynamic ability is missing, and with omnidirectional antennas, which are designed to have equal gain in all directions. Because of these characteristics, smart antennas may provide increased communication range by dynamically concentrating the transmitted power towards the intended receiver(s). This also reduces the contention on the wireless medium, as devices not involved in transmissions are less affected. Both features yield increased reliability at the physical level, an asset for network functionality such as routing protocols. Moreover, localization mechanisms may also take advantage of angle-of-arrival information [1]. However, applying smart antennas in real-world sensor networks remains an issue, due to the lack of practical prototypes that can be easily integrated with existing sensor network platforms. Some experiments are reported with prototypes that tend to be large, costly, or impractical because of the need of external power [2]. A few solutions also exist that require advanced signal processing techniques, which are generally difficult to implement on resource-constrained devices. As a result, most sensor network research involving smart antennas has been hitherto carried out in simulation. Confronted with these issues, we design and build a smart antenna that is sufficiently inexpensive and practical to allow its integration with existing sensor network hardware. We also developed the software functionality to enable its use in a standard sensor network stack. 2. THE SPIDA SMART ANTENNA We design the SPIDA 1 smart antenna to operate in the 2.4 GHz ISM band aboard a TMote Sky device, using a CC2420 radio. The current prototype is shown in Figure 1, attached to the sensor node through a standard SMA connector. We describe next the hardware/software characteristics,