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  • Communication Technologies

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    Tim Kannegieter

    Introduction:

    IOT communication technologies includes those at the local area network (LAN) level, typically on a premises, through to site or area level which would typically involve a wireless wide area networks (WAN). These networks provide an interface to the internet (hence into cloud services) and also to user interfaces typically supported by mobile device applications.

    Wired communications could be used for the "things" in the IoT, however it is not practical or affordable and wireless is preferred. "Wireless" refers to communication via electromagnetic radio frequency waves.

    Options

    There are a range of wireless and wired connection options. At the lowest level you have a personal area network, where typically consumer devices can connect typically to the internet via a mobile 3G or 4G device and can be controlled, accessed and monitored through that same device. Personal area networks can also include an intermediary wifi network in a home or premises providing internet connectivity. Bluetooth is an option in certain applications.

    Intermediate level networks cover the range of 100 meters to 1 kilometer, using technologies such as Zigbee or 6LoWPAN. The key to these technologies is that each radio node in the network can operate as a repeater or relay for the other nodes in the network, allowing devices to be deployed over a reasonably wide area that exceeds the connectivity capability of any one link, with the intermediary links providing a relay function. Connectivity from a hub in that network is by 3G or 4G.

    Wider level networks, until very recently, have used traditional cellular data networks (LTE - 3G, 4G), as well as a range of other wired technologies. These provide high capacity, low latency data connectivity over a wide geographic area, with automatic routing and redundant communications paths – ie the Internet. LTE stands for Long Term Evolution, and that encompasses 3G and 4G which are currently deployed. Cellular connection typically has high power consumption and hence energy requirements, and battery powered applications using cellular data modems on 3G or 4G are quite challenging. There's also a high cost per bit of data conveyed, particularly when the overhead of maintaining the connection is taken into account. The amount of data required to establish a connection and convey information grossly outweighs the information that one would typically want from a simple sensing device. Therefore the future of connectivity for IOT technologies is moving in the direction of a new range of technologies known as Low Power Wide Area Networks which are more suited to the low power, low data rate environment of the IOT.

    Other options include:

    • Optical fibre networks
    • Satellite links
    • Copper networks (ADSL, HFC)
    • WiFi (in CBD areas); Wimax (BigAir, IINET in SA)

     

    Wireless communication is possible using electromagnetic waves outside of the radio frequencies, such as optical wireless communications including infrared (IR) and ultraviolet (UV) light. However, the vast majority of current commercially available technologies likely to be deployed in the IoT use radio frequencies. Therefore the focus of content on IoT communication technologies is on Radio Frequency (RF) Bands.

    Design considerations:

    One design consideration is latency; how long would a device take to communicate; or to connect? By illustration, connecting a Bluetooth phone to a car might take up to ten seconds compared to Zigbee which might be up to only 30 milliseconds.

    Another consideration is how many nodes are required for an application, and whether that is possible using a given technology option. Zigbee, for example, supports up to 64,000 nodes per master.

    Range is also a consideration. How far apart can communications nodes be? WiFi distance is known, and could be improved using an antenna to get greater distances. Bluetooth is typically limited to around ten meters distance. Zigbee’s distance depends on the power level. Top recorded distances in Europe are 7300 meters and in the US 1.6 kilometers. The difference is explained by European regulation’s higher permissible power level.

    The types of things being deployed (sensors and embedded systems) and power usage can also affect the choice of communication technology. For example, the length time and proportion of time that devices may be in low power mode (i.e. sleeping) is important. As an example, when Zigbee has coordinators, routers and end devices, most importantly, only the end nodes can sleep. The other devices have to be powered at all times. For off-grid scenarios this usually necessitates a battery backed solar power source to support the power requirement of the routers and the coordinators. 

    Other considerations include whether a network needs to be extendable? Does it support roaming? What data rates are possible? What security levels are required. What RF topology is being used and what communication technology will support it?

    Standards and protocols

    Pictured blow are some of the protocols that anyone deploying an Internet of Things system will likely have to deal with.

    Protocols.JPG.aa01779d1a8bfc29cd38e7670d7427c5.JPG

    In the Wide Area Network we have the typical internet communications protocols, which are most useful for communications between gateways and cloud devices and they do require significant resources to implement. The protocols listed right are those typically found in Local Area Networks and not included in this list are all the low power WAN protocols. When NBIOT comes along the protocols at you see on the left and the right will then apply more broadly over that connection. 

    The IEEE standard for wireless LANs is 802.11. Devices are certified by the WiFi Alliance for interoperability. WiFi devices are ubiquitous. Bluetooth is also ubiquitous, based on IEEE 802.15.1, due to its implementation in high volume products such as smart phones and cars. Zigbee is based on IEEE standard IEEE 802.15.4, which is for low power wireless personal layer networks, which could be used for IoT.

     

    Sources: Material on this page has primarily been sourced from the following:

    Edited by Tim Kannegieter



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