Nuts and Volts - March 2015

64 March 2015

HOW IT WORKS

In most applications, the device to be monitored or controlled has an integrated sensor and wireless transceiver that connects via the cellular system, Wi-Fi, or other wireless link to the Internet. Cellular links connect directly to the Internet, while Wi-Fi or other wireless technologies connect by way of a gateway or router that links to the Web.

The Internet connection contacts a remote server that contains the application software. Then, the monitoring device (like a laptop, tablet, or smartphone) makes an Internet connection to the server to complete the service. Data is then captured and displayed or stored, or some control commands are issued.

All devices are assigned an Internet Protocol (IP) address.

Thanks to the latest IPv6 protocol, up to 2,128 addresses are possible. That should be more than enough to handle the largest collection of Io T devices possible.

In almost every case, a wireless link is used for communications. Cellular connections are common for M2M applications like vehicle tracking, pipeline monitoring, or the like. Wi-Fi is popular for home or business applications since home routers and office access points are common.

The fact is that any short-range wireless technology can be used. However, many of the most popular standards do not provide a convenient way to connect to the Internet.

That is now changing. Both of the widely used Bluetooth and ZigBee technologies now offer new versions that are tailored to Internet connectivity.

BLUETOOTH 4. 2

Bluetooth is a short-range radio technology that operates in the unlicensed 2. 4 GHz industrial-scientific-medical (ISM) band. Bluetooth is a standard of the Bluetooth Special Interest Group (SIG). It has a range up to about 30 feet. The basic output power is 1 m W (0 dBm), but you can use two other power levels for longer ranges: 2. 5 m W ( 4 dBm) and 100 m W ( 20 dBm). The 4 dBm version is the most popular, but the higher power version can reach out to about 100 meters under line-of-sight conditions.

Bluetooth has a raw data rate of 1 Mb/s, but some of that is overhead that goes to headers and error correction so the net data rate is 723 kb/s. The modulation is Gaussian FSK in a frequency hopping spread spectrum (FHSS) scheme. The carrier hops from one of the 79 channels to another in a random sequence.

The hop rate is 1,600 hops per second for a dwell interval of 625 microseconds. During each hop interval, some data is transmitted. The FHSS method makes the data very secure.

A newer version of Bluetooth is 2.1 -- called Enhanced Data Rate (EDR) -- and it uses π/4-DQPSK

he Internet of Things (IoT) movement is underway and already products are beginning to show up. It is still early in this trend, with billions more devices to be built and connected. However, now it is easier than ever thanks to some updated wireless standards.

First, if you are not familiar with IoT, you should see my June 2014 column on this topic. In way of review, IoT is a communications technology that is used to monitor and/or control practically any device by way of a communications link including the Internet. IoT or the Internet of Everything (IoE) — as some call it — includes machine-to-machine (M2M) communications, as well as machine-to-human or human-to-machine. While the IoT movement is just beginning, many in industry predict that from 20 to 100 billion devices could possibly be connected by 2018 or 2020.