COMMUNICATIONS between machines is becoming almost as important as communications between people, as evidenced by the proliferation of industrial automation. With growing reliance on automated equipment for quality of life in many areas, including in critical infrastructure cases, the need to increase machine-to-machine (M2M) communications is growing steadily with time. Some of the same communications devices and networks that work for people can also work for machines and devices, including Bluetooth, ZigBee, IEEE 802.11 Wi-Fi, cellular 2G/3G/4G systems, land-mobile radio systems, and ultrawideband (UWB) technologies. However, with the almost explosive growth of wireless devices communicating in license-free Industrial-Scientific-Medical (ISM) bands, congestion is becoming a serious concern, especially for mission-critical applications. One possible alternative lies within licensed radio spectrum and the LRS-455 UHF licensed-band radios from FreeWave. Designed to be used in the 435-to-470-MHz band in the United States, Europe, Australia, and New Zealand, and from 406 to 430 MHz in Canada, Mexico, and parts of Latin America, these serial data radios can achieve as much as 19.2 kb/s throughput over a single 12.5- kHz channel.
The LRS-455 licensed-band industrial radios combine robust radio transmitters with sensitive receivers in rugged industrial-grade enclosures (see figure), but are also available in board-level configurations for embedded applications by original-equipment-manufacturer (OEM) customers. The radio transmit output power is programmable in 10 steps to as much as 2 W (+33 dBm), while the receiver sensitivity is rated for -112 dBm for a data rate of 9.6 kb/s with a bit error rate (BER) of only 1 b error in 1,000,000 b transmitted, at a data rate of 9.6 kb/s. The RF link budget achieved by the 2-W transmit power and high receiver sensitivity translates into a line-of-sight (LOS) communications range of about 70 miles. This is comparable to radios requiring 5 W transmit power for the same range while drawing more electric current to support the higher transmit power.
The LRS-455 radios offer flexibility allowing users to configure a channel in 6.25-kHz steps, resulting in 56,000 possible selections. Because these radios are operating in licensed spectrum, they do not share the spectrum with other users. The radios are designed to meet communications standards in the US and international markets and are already certified per the European Telecommunications Standards Institute (ETSI) for use in more than 27 European countries, plus Canada, Mexico, Australia, and New Zealand.
The radios employ 32-b cyclic-recovery-code (CRC) error correction and manage link throughputs of 9.6 kb/s, with two-level Gaussian frequency-shift-keying (GFSK) modulation and 19.2 kb/s with four-level GFSK modulation. Both modulation formats are standard. The radios are designed for operating voltages from +6 to +27 VDC with low power consumption. Current draw at +12 VDC on transmit is 0.65 A and on receive is 92 mA (an idle mode requires 21 mA).
Matthias van Doorn, FreeWave's Product Manager, Ethernet & Licensed Radio Systems, explains: "Customers who deploy these radios in remote locations that typically aren't on the grid, and depend on battery power and solar charging for operation, will appreciate the industry-leading receive sensitivity and RF performance to support longer links, even without high RF output power and the associated high current draw that other products in the market exhibit. And unlike native-IP radios, the LRS Series does not get burdened with protocol overhead for its serial data communication, resulting in better throughput, faster polling cycles, and an increased number of remote radios that can be polled from the same master site. Smaller batteries and solar panels and fewer master radios result in significant savings for our customers that quickly add up in larger networks."
A board-level LRS-455 radio measures 128 x 61.8 x 19.7 mm (with SMA antenna connector) and the housed LRS-455 measures 173 x 112 x 35 mm (with TNC antenna connector). The board-level radios are equipped with 10-pin header for data connections, and a variety of control interfaces, including RS- 232, RS-485, RS-422, and TTL interfaces. The UHF radios can be configured in point-to-point or point-to-multipoint configurations, and each radio can act as a gateway (master), endpoint (slave), or repeater (slave repeater). The radios are UL Class 1, Division 2 certified for hazardous environments.