# A Cooperative MAC Protocol for a M2M Heterogeneous Area Network
## 7 Conclusions  
This paper has presented a new cooperative MAC protocol for an M2M heterogeneous area network to support IoT applications using low-cost wireless networking standards that operate in the unlicensed spectrum. The work specifically focused on eliminating the inter-network collision problem to improve the throughput of an M2M area network in a dense networking environment. Simulation results show that the proposed blank burst signaling algorithm reduces the number of inter-network collisions significantly and maintains a stable delay profile. The BB signaling structure has no negative impact on the access network's delay due to the introduction of silence periods. The BB signaling architecture improves the PSR value, as well as offers a stable delay and makes the end-to-end delay less dependent on the traffic load. The BB signaling design can accommodate different traffic QoS requirements by adjusting the BB signaling period. The proposed signaling structure requires no additional signaling traffic since the BB signal is propagated by using the beacon field of the superframe.  
Figure 14: Blank Burst signaling frequency for different aggregation factors at a traffic load of 2 packets/s/device.  
Figure 13: End-to-end delay for three different networking scenario.  
The design presented here is also scalable where both networks can share the common transmission spectrum without intra- and inter-network collisions. The proposed network architecture is suitable for a dense network deployment where the frequency hopping technique may not be useful to avoid inter-network collisions or interference. The proposed solution is also energy efficient compared to 3G/4G cellular networks since the short range networking standards use lower transmission power, as well as have lower signaling load. The developed BB signaling does not require any additional transmission resources as the BB signal is mapped onto the existing IEEE 802.15.4 superframes; hence, no additional transmission energy is necessary. It is well known that IEEE 802.15.4 networks are far more energy efficient than 4G/LTE networks [29]. The proposed heterogeneous network will maintain the same level of energy efficiency while providing M2M area networking support over a wide area. Other works have shown that cooperative MAC protocols in a random access network can improve the energy efficiency. [30] proposed a distributed information sharing (DISH) cooperative approach for a multichannel MAC to improve the energy efficiency.  
The proposed network will be further extended to incorporate multiple MFDRRs to support increased node density in a geographical area. Future research will also concentrate on the heterogeneous network architecture using the IEEE 802.11 ah standard.  
[PERSON] conceived the idea of a heterogeneous network architecture and the blank burst algorithm. [PERSON] implemented the idea and developed simulation models and obtained performance results. [PERSON] developed a unique OPNET simulation model to analyze the heterogeneous network performance. [PERSON] was involved in developing the simulation model and further enhanced the performance analysis model.  
The authors declare no conflict of interest.