Undersea Sensor Networks for Intrusion Detection:
Foundations and Practice
Challenges and design issues
We consider sensor dispersal patterns that result in a random distribution in a 3-dimensional (3D) ocean space of interest. For example, sensors may be dispersed from an aircraft or artillery ordinance, as shown in Figure 1. Previous work on sensor networks for intrusion detection has primarily focused on 2-dimensional (2D) terrestrial strips. In 2D strip sensor networks, a chain of sensors from one end of the strip to the other end with overlapping sensing areas of adjacent sensors can detect any intruders regardless which paths they choose to follow (see Figure 1(c)). Constructing a 3D undersea sensor network to detect undersea intrusions, however, is much more complicated. Even if an unbroken chain of overlapping sensor clusters from one side to the other side exists in a cuboid, intruders may still evade detection by passing through such a chain. Thus, an overlapping sensor chain no longer meets the requirement of detection. Instead, we require that a certain curved
Figure 1: (a) Sensors are dispersed from artillery ordinance on a ship. (b) Sensors are dispersed from an aircraft. (c) A 2D barrier on a plain surface.
surface that cuts across the space of interest (i.e., a 3D cross section) be fully covered by sensors. Figure 2 illustrates this requirement, where a sensor is denoted by the solid red dot and its sensing range by the cloud-like red sphere with the sensor in the center. In Figure 2(a), the coverage of sensors does not contain 3D cross section, where holes exist to allow intruders to pass through undetected. In Figure 2(b), the coverage of sensors contains a 3D cross section, which can detect any intruders.
Figure 2: (a) The sensor coverage does not contain a continuous cross section and intruders may pass through undetected. (b) The sensor coverage contains a continuous cross section that can detect any intruders regardless their moving paths.
The unique characteristics of underwater acoustic channels make the 3D intrusion detection even more challenging. Due to the quick absorption of radio in water, acoustic communication has been the most viable method for underwater environments. Such a transmission medium change, however,