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Growing demands and key requirements for Machine-to-Machine (M2M) communications have raised concerns about the coexistence of various networks in unlicensed bands. Currently in unlicensed bands, Short Range Devices (SRD) are performing a part of the services that M2M aims to implement. SRD comply with European standards and therein two random access schemes, Duty Cycle (DC) Limit and Listen Before Talk (LBT), are specified. In fact, DC Limit and LBT can be regarded as pure ALOHA and non-persistent CSMA, respectively. Thus, it is likely that radio devices using ALOHA and CSMA coexist in a single network. However, in spite of the simple concepts of ALOHA and CSMA, there have been few research works on the accurate performance analysis for such heterogeneous networks due to high correlations among devices. To tackle this issue, we rigorously investigate the types of collisions that can occur in such networks and derive accurate formulas for related probabilities. We also provide new and accurate closed form expressions for the throughput and success probability associated with each channel access scheme. The accuracy of our results is validated by simulation. Taking advantage of the accuracy of our results, we provide a method to configure the network for optimal network throughput. Furthermore, we devise a distributed dynamic channel access mechanism in which each device adjusts its access scheme by learning the network state to achieve near-maximum network throughput and high fairness.

Performance Analysis and Fair Coexistence of Heterogeneous Radio Networks for Multiple Devices With Different Channel Access Schemes