The Internet of Things (IoT) is a network for implementing interconnection and interworking of human to machine and machine to machine (M2M). The 3rd Generation Partnership Project (3GPP) has set up special project teams to study low-cost machine type communication (MTC) based on long term evolution (LTE), where the communication type can be used in the Internet of Things.
The study on the low-cost MTC mainly considers enhancement or optimization that needs to be performed on an LTE network and an air interface with regard to introduction of an MTC device, where a coverage problem is one of key problems concerned by operators. An important application of an MTC terminal (also called user equipment, UE for short) is a smart meter. For example, the MTC terminal can be used to automatically read water, electricity, gas and other metering information and report the metering information to a data center. Generally, this kind of smart meter is installed in a basement of a house, isolated by a metal enclosure, or installed in an old-fashioned building with thick walls. In this case, path loss between an MTC UE and a base station is extremely severe, and the quality of communications between the base station and the MTC UE is relatively poor.
By taking cost and spectrum factors into account, operators do not want to add a new site and relay device. Therefore, the operators impose a new requirement, expecting that when an LTE system provides a service for an MTC UE, coverage of the LTE system needs to be enhanced by 20 dB compared to an existing LTE system.