Wireless Sensor Networks, part 2: Limitations - Design challenges

I already mentioned some challenging areas in the first part of the article (energy saving algorithms, location discovery and security). In this section I’m going to list some more areas that pose a challenge to researchers and developers, who are called to bridge the gap between sensors’ limitations and their efficient functionality.

• Scalable and flexible architecture. The network should be scalable and flexible to the enlargement of the network’s size. The communication protocols must be designed in such a way that deploying more nodes in the network does not affect routing and clustering. Rather, the protocols must be adapted to the new topology and behave as expected. In other words, the network must preserve its stability. Furthermore, introducing more nodes into the network means that additional communication messages will be exchanged, so that these nodes are integrated into the existing network. This must be done in a way that a minimum number of messages needs to be exchanged among the sensor nodes, and thus battery is not wasted unreasonably.
  
  
• Error-prone wireless medium. Since sensor networks can be deployed in different situations, the requirements of each different application may vary significantly. Researchers must take into consideration that the wireless medium can be greatly affected by noisy environments, and thus the signal attenuates in regard to the noise. Note that an adversary can intentionally interfere and cause enough noise to affect the communication. In an environment such as healthcare, it is vital to ensure that communication is on time to respond to emergencies.
  
  
• Fault tolerance and adaptability. If a sensor node fails due to a technical problem or consumption of its battery, the rest of the network must continue its operation without a problem. Researchers must design adaptable protocols so that new links are established in case of node failure or link congestion. Furthermore, appropriate mechanisms should be designed to update topology information immediately after the environment changes so as to minimize unnecessary power consumption. 

Conclusions

In this article I covered the major limitations of sensor nodes. The hostile and remote environment at which sensors are often deployed and the limited computational and energy power along the limited storage are the factors that drive the adoption of security solutions. Since the limited resources affect the types of security algorithms and protocols that can be implemented in a WSN, lightweight security solutions should be addressed.

I also discussed some challenging directions that need special attention. Focus should be placed on designing protocols that are scalable, flexible, fault tolerant and adaptable to dynamic changes. However, the main challenge for researchers is to balance the trade off between resources spent for security and the protection offered. The target is to have a spherical security strategy with solutions that compensate each others' vulnerabilities, and provide an enhanced protection to the network and its information.