# A Cooperative MAC Protocol for a M2M Heterogeneous Area Network
## 1 Introduction  
With the rapid expansion of Machine to Machine (M2M) communication and Internet of Things (IoT) applications in different domains, such as smart city, smart grid, healthcare, and environmental monitoring, the need for the development of low-cost, energy-efficient reliable area network architectures is increasing [1]. For M2M and IoT applications, communication area networks play a very important role in moving data between various sensors, actuators, servers, and controllers. Many such applications will operate either in real-time or in delay-bounded conditions. For smart city and smart grid applications, network entities or devices, such as sensors, actuators, and controllers could be distributed over large geographical areas where devices could be located either in indoor or outdoor environments. In outdoor deployments, reliable data communication could be a challenging task due to the distributed nature of the system, heterogeneous radio propagation environments, as well as variable traffic conditions [2]. At the same time, communication service requirements for the M2M/IoT applications are different compared to traditional data networks. Questions might arise, such as why should we consider the communication needs of M2M and IoT systems together?Traditionally M2M solutions typically use point-to-point links using wired or wireless connectivity. On the other hand, IoT solutions rely on Internet Protocol (IP) networks to interface data to a cloud or middleware platform. M2M communication is more concerned with the lower-level networking functionalities [3]. The IoT represents connectivity beyond transmission from one machine to another. Obviously there is a certain overlap between these two systems; that is, the need to use lower-level network protocols and architecture. Hence, we explore the communication needs for both systems. Key requirements of IoT applications are listed below:  
* Need to serve medium to high network device density (devices/sq.km), generating small bursts of data with variable duty cycle. * Low energy availability for computing and communication needs. * Very high reliability with variable Quality of Service (QoS) requirements. * Low, or no, terminal mobility. * Asymmetric traffic flow with higher capacity requirements on the uplink (i.e., from an end device to a network-based data sink). To serve distributed IoT applications with the above requirements, different wireless network architectures can be used. Traditional cellular wide area networks could be used to support such applications which generally have higher capital expenditure (CAPEX) and operational expenditure (OPEX) costs. Another approach could be to use unlicensed band short range wireless networks where multi-hop or mesh wireless network architecture can be used to cover large geographical areas. Traditional cellular networks, such as 3G/4G-based standards may not efficiently support all of the needs of IoT applications due to high signaling requirements, infrastructure, and energy costs [4]. Additionally, cellular networks may not provide seamless connectivity to all devices due to spatial and temporal fading effects. The M2M communications functional model proposed by the European Telecommunications Standards Institute (ETSI) standard suggests that cellular networks could provide core network support and aggregated data from gateways could be transmitted over cellular networks [5]. Hence, to support the device level communication, it is necessary to develop a new wireless sensor network architecture that can deliver QoS requirements for different applications. The two main drawbacks of traditional wireless sensor networks are lack of deterministic QoS support and the scalability problem [6]. The main contribution of this paper is a new low-cost heterogeneous network architecture that can support IoT data transmission needs in a wide area with the necessary QoS requirements.