The need to deploy large number of wireless devices, such as electricity or water meters, is becoming a key challenge for any utility. Furthermore, such a deployment should be functional for more than a decade. Many cellular operators consider LTE to be the single long-term solution for wide area connectivity serving all types of wireless traffic. GSM/GPRS is a well-adopted technology and represents a valuable asset to build M2M infrastructure due to the good coverage, device maturity, and low cost. We recently submitted a paper in which we assess the potential of GSM to operate as a dedicated network for M2M communications. In order to enable M2M-dedicated operation in the near future, we reengineer the GSM/GPRS/EDGE protocol in a way that requires only minor software updates of the protocol stack. We propose different schemes to boost the number of M2M devices in the system without affecting the network stability. We show that GSM a single cell can support simultaneous low-data rate connections (e. g. to smart meters) in the order of 10^4 devices.
Ideally, a TDMA system should be able to allocate as many as possible devices as long as the quality of service is guaranteed. However, in practice, systems are typically not able to operate in this manner. GSM and GPRS are an example of a TDMA system limited by the protocol rather than the application requirements of the smart meters. Specifically, for smart metering, a payload below 1000 bytes is expected. Moreover, the traffic patters corresponds to device originated with periodical reporting in the range of 5 mins, 15 mins, 1 hour and 6 hours. These devices tolerate a delay up to the next scheduled transmission opportunity if the message was not successfully delivered.
The main idea is that resources are pre-allocated according the application needs. In this manner, thousands of simultaneous connections can take place in a single cell (a single frequency is considered). In addition, we analyze the probability of reports exceed the deadline. This probability is presented in the following figure, where it is noticeable that for the most demanding case when RI=1min, a single cell could provide service for up to 5 · 10^3 simultaneous connections with a reliability of 99.99%. This number rises to outstanding value of 5 · 10^4 simultaneous connections that are served with 99.99%, if the reporting interval is set to 15 min.