Efficient & reliable data processing for scalable Internet of Things:
Innovative amplify-and-forward-based AirComp

One of the critical issues for the proliferation of Internet of Things (IoT) is the collection and computational analysis of wireless data from huge networks of smart sensors being implemented in applications that include smart transportation and cities. Recently, the technique of over-the-air computation (AirComp) has been proposed as an integrated approach for collection and processing of data from sensor networks transmitting Big-data simultaneously. Notably, although this method is efficient, it requires that all signals from nodes arrive simultaneously at the sink, aligned in signal magnitude so as to enable an unbiased estimation. However, for nodes far away from the sink with low channel gains, it is not possible to avoid misalignment in signal magnitude.

Now, Suhua Tang and colleagues at University of Electro-Communications, Tokyo, University of Science and Technology, China, and Xi’an Jiaotong University, China, describe their solution to the misalignment problem using the amplify-and-forward (AF) based relay mechanism.

In their paper, Tang and colleagues first present the general relay model for AirComp, and investigated the possibility of using a simple relay (SimRelay) approach in which a node either directly transmits its signal to a sink or via a relay node, but not both. They emphasize that, “relay transmission power increases with the number of nodes that use the relay node.”

The researchers also proposed a coherent relay (CohRelay) approach, in which a node can divide its power to transmit its signal to both the relay and the sink, and the replicas of its signal are coherently combined together at the sink. They also discuss the tradeoff between computation error and transmission power.

The CohRelay approach greatly reduced the computation error, as well as reducing the relay transmission power and the overall transmission power, which is a major step forward towards the practical applications of AirComp.

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