Cellular machine-type comm unications: physical challenges and solutions.

Cellular communication technologies are developed mainly for \"human-type\" communications, while enabling machine-type communication (MTC) with cellular networks (e.g., 3GPP LTE) not only improves the accessibility, availability, and reliability of an MTC network, but also has the potential to further drive down the operation cost. However, the application of LTE to MTC poses some unique challenges due to the large performance mismatch between the LTE user equipment and the MTC device, caused mainly by the physical limitations of most MTC devices. This article addresses these limitations, and examines their impact on the link performance and the corresponding link budget. The focus of this article is on the physical control channels. We address the issues of the existing LTE control channels, and propose an enhanced design specifically tailored for overcoming the limitations of MTC devices and meeting the stringent link budget requirement by applying repeated transmissions, spatial precoding, frequency hopping, and joint channel estimation. Finally, the design concept is extended to other channels such as the random access channel and the data channels.