On the optimal resource allocation for machine-to-machine communications in cellular networks

Cellular networks are an attractive option to handle growing number of sensing and monitoring devices due to their ubiquitous presence. While this growing popularity of cellular based machine-to-machine (M2M) communications is opening new avenues for the operators, it is also bringing forth new system design challenges primarily due to the huge difference in the operational regimes of the M2M and conventional cellular networks. In this paper, we study the problem of power optimal uplink scheduling both for TDMA and FDMA in the M2M regime characterized by large number of small transactions. We derive tractable results for the maximum load a BS can handle and the optimal transmit power for both access strategies and show that FDMA supports order of magnitude higher load than TDMA. We also show that the value of optimizing uplink schedules in the M2M parameter space of interest is typically insignificant and simpler access strategies, such as equal resource allocation, lead to near optimal performance. Lastly, we derive tight closed form approximations for the optimal power results that can be used as proxies for the actual results in this regime.