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The evolution of microfabrication has allowed silicon chips to become very small (on the micron scale) with a lot of intelligence capabilities. One of the applications of these small chips has been for wireless sensor networks and smart dust. The limitations of these devices is that they have small batteries with small amounts of available power; thus limiting the lifespan of the sensors. An attractive solution to making the wireless sensors more energy efficient is to use cooperative beamforming.
Cooperative beamforming uses the concept from smart antennas that using an array of antennas the radiation pattern can be focus its transmission energy to desired direction. Thus, the required transmission power and propagation loss is reduced. In wireless sensor networks, the array of antennas are not organization in a known structure. The sensors first collaborate their received data with other locally located sensors. Then each participating sensor must determine the complex weight needed to allow transmitted packets to add coherently at the same destination.
Implementing cooperative beamforming clearly comes with power and time overhead for the data sharing among the collaborative sensors. In addition, mitigating synchronization issues and determining precise position locations of the collaborating sensors creates further overhead. Despite these overheads using cooperative beamforming can save energy. The amount of energy saved is dependent on the size of the network, the data rate, and the design transmitter and receiver circuits. For a given transceiver design and data rate, as the number of collaborating sensors increase so does the energy savings over single sensor transmission, but there becomes a point where the beamforming directivity gain saturates while the energy related to the overhead continues to grow linearly.
Implementing cooperative beamforming is a multi-variable optimization problem, but when optimized can achieve 90% energy savings over single sensor transmission.