Hello, everyone!
Today, I would like to continue on the WLAN scenarios and challenges relating to Machine-to-Machine (M2M) communications.
The almost ubiquitous presence of sensor/actuator devices that are able to interact with the environment has fostered the creation of new services and applications. Concepts such as smart cities and smart grids are being developed on the basis of the existence of those sensor/actuator networks to achieve a more sustainable use of the environmental resources and provide citizens with a higher quality of life.
In a classic sense, Wireless Sensor Network (WSN) technologies are used to collect data from spatially distributed sensor nodes and to transmit the data over a multi-hop wireless network to a central sink. The M2M paradigm is broadening the scope of the WSN concept because it enables networked devices, wireless and/or wired, as well as services, to exchange information or control data seamlessly, without explicit human intervention.
Clearly, M2M communications face most of the technical challenges of WSNs. One of the main limitations of WSNs and M2M systems is that the network nodes are usually battery powered or have limited access to power sources. Designing mechanisms and protocols to reduce their power consumption with the goal of extending the network lifetime is therefore crucial for the successful commercial take-up of these kinds of networks.
Fortunately, devices in M2M systems typically generate or consume alimited amount of data per unit of time. Thus they can spend a large fraction of their time sleeping. This facilitates energy saving at the cost of additional complexity for the channel access and networking protocols.
Popular wireless protocol standards for M2M communications are Bluetooth, ZigBee and BT-LE. An alternative, promoted by mobile networks, is to connect devices in M2M systems directly to the Internet by using the cellular network infrastructure, for which specific protocols has been developed.
WLANs are envisioned as an alternative to both multi-hop WSNs and cellular networks. However, current WLANs are not able to satisfy the minimum requirements for M2M communications. Novel specific power-saving mechanisms are required to support the long periods of inactivity needed by the sensor/actuator devices and to manage the thousands of nodes associated with a single AP.
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