Channel-Aware Multichannel Random Access for Energy-Limited Sensors and MTC Devices

In machine-type communications (MTC) or wireless sensor networks (WSNs), since MTC devices or sensors have limited supply of energy, energy efficient transmission schemes are important. In addition, transmission schemes should not be complicated for sensors of limited capabilities. In time-division duplexing mode, channel-aware random access schemes seem promising as they can be implemented with simple operations without coordination and exploit the channel state information for energy efficient transmissions. In this paper, we propose a channel-aware random access scheme with multiple slots where each slot's transmission probability can be optimized under long-term and short-term energy constraints. The proposed scheme outperforms a single threshold-based channel-aware random access scheme for a low maximum transmission power of sensors. Furthermore, due to multiple slots, sensors of low channel gains can also transmit their local signals as those of high channel gains, which improves the fairness.