Wireless communication is both a blessing and a curse for sensor networks. On the one hand, it is key to their flexible and low-cost deployment. On the other hand, it imposes considerable challenges because wireless communication is expensive and wireless link conditions are often harsh and vary considerably in both space and time due to multi-path propagation effects.
Wireless communications have been studied in depth for several decades and entire books are devoted to the subject. The goal of this chapter is by no means to survey all that is known about wireless communications. Rather, we will focus on three sets of simple models that are useful in understanding and analyzing higher-layer networking protocols for WSN:
1. Link quality model: a realistic model showing how packet reception rate varies statistically with distance. This incorporates both an RF propagation model and a radio reception model.
2. Energy model: a realistic model for energy costs of radio transmissions, receptions, and idle listening.
3. Interference model: a realistic model that incorporates the capture effect whereby packets from high-power transmitters can be successfully received even in the presence of simultaneous traffic.
Figure 5.1 A realistic packet reception rate contour
Figure 5.2 Realistic packet reception rate statistics with respect to inter-node distance
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