Machine Type Communication (MTC) devices (sometimes referred to as Machine-to-Machine or M2M devices) are increasingly being used for a variety of applications. Their numbers are expected to grow at a high rate. MTC devices are typically automated data reporting systems such as utility meters or status reporting devices.
Thus, MTC devices are likely to have significantly different usage or operational characteristics from other types of User Equipment, UE. Such devices may be programmed to send data at a specific time, for example late at night. Also, other types of MTC devices may be triggered by specific events, such as a burglar alarm. Many of these may activated by the same event (for example, a power cut or earthquake). In any event, the volume of data transmitted and received by such devices is often low.
It has conventionally been understood that nearly all MTC devices (or at least 95%) will operate on their home cellular radio network, referred to as the Home Public Land Mobile Network (HPLMN). This is identified by the PLMN-ID of their International Mobile Subscriber Identity (IMSI). The possibility that MTC devices will use another network, also referred to as roaming or using a Visitor Public Land Mobile Network (VPLMN), has been previously considered to be a rare event. It has therefore been thought that network operators would be able to manage the large number of MTC devices by dimensioning their networks accordingly. Hence, MTC devices are generally expected to act and to be treated no differently from any other type of UE. This allows their introduction at minimum cost and without significant increase in network complexity.
The possibility that large numbers of MTC devices may require facilities for roaming has consequently not been considered. However, this possibility presents a significant challenge for network operation and is further described below.