One of the big issues facing designers of Internet of Things (IoT) products is deciding upon one of the dozen or so wireless technologies vying for adoption. Here is one more to consider: ultrawideband (UWB). While UWB has not been widely adopted, it is nevertheless still around. This unique wireless technology has some major benefits that you may be ignoring while seeking an optimum wireless method. It occurred to me that it could be an undiscovered option for some IoT applications.
Two Basic Types
There are two primary forms of UWB: impulse and multiband. To be considered as UWB, the technology has to meet the definition that says the signal must have a bandwidth of at least 20% of the center frequency, or 1.5 GHz minimum. Or the signal must occupy at least 500 MHz of bandwidth. The impulse method typically uses very short (< 1ns) Gaussian-shaped impulses with pulse position of pulse phase modulation. The center frequency is roughly defined as the reciprocal of the pulse width.
The multiband form uses 128 subcarrier OFDM in a 528-MHz band. These forms of wireless are authorized to operate in a license-free spectrum from 3.1 to 10.6 GHz in the U.S. with a power level not to exceed −41 dBm/MHz.
Primary advantages are:
- License-free spectrum
- Power efficient. Very low power consumption.
- Very high data rates from 100 Mb/s to many Gb/s.
- Immunity to multipath propagation effects.
- Superior resolution in radar, ranging, and location applications.
- Non-interfering signals to others in the same band. UWB signals appear as noise to other receivers.
- Natural multiple access as many signals can share the same wide spectrum without interference, as coherent receivers can sort out the multiple transmissions.
- Simple circuitry and low cost.
- Generally secure because of the unique format.
- Efficient use of the spectrum and spectrum sharing.
The disadvantages are:
- Short range. Low power and high frequencies limit the range to roughly 10 to 100 meters under the best conditions.
- Antennas are hard to design and implement because they not inherently broadband devices. Unique designs are necessary.
One of the newer UWB products is a wireless microphone system using the impulse method. It is made by a company called Alteros. Its GTX Series uses 2 ns pulses with a 6.5-GHz center frequency, and can accommodate up to 24 channels with a TDMA scheme. The audio frequency response is 20 Hz to 20 kHz with a latency of less than 3 ms. This is an interesting use case, as it shows what can be done.
One of the oldest impulse-based UWB vendors is TimeDomain. Its PulsON modules are used mainly for radar, ranging, and general data communications.
The only vendor of multiband UWB is Alereon. Its OFDM chip has been built into cameras, video monitors, TV sets with HDMI, docking stations, and military communications.
One interesting UWB variation is Pulse~LINK’s CWave technology. It uses a continuous sine wave carrier modulated with BPSK. One version uses a 4 GHz carrier with 750 ps phase shifts to give a data rate of 1.35 Gb/s. Pulse~LINK chips can implement this in wireless or wired form. One wired version uses coax cable and two channels or bands—one at 2.7 GHz and another at 4 GHz. It works at up to 500 ft. and is an alternative for carrying gigabit Ethernet payloads. Worth a look.
Just recently, I received a copy of a new book on UWB entitled Ultrawideband Short-Pulse Radio Systems by authors V.I. Koshelev, V.P. Belichenko, and Y.I. Buyanov. Recently published by Artech House Publishers, the book is a detailed text on the impulse method of ultrawideband wireless. Chapter 1 is an excellent introduction to the topic. The book then goes on to give comprehensive coverage of methods, analysis, and practice of UWB. Topics include sources, antennas, propagation, electromagnetic theory, and practical systems. There is good emphasis on antenna design and high power applications. It’s a must-have reference if you are going to design in this area.
IoT Option or Not?
I’m just asking: Is UWB really an alternative for IoT applications? It has high speeds, low power consumption, good security, and a range generally suitable for multiple applications. It could become the method of choice as more and more IoT devices flood the market. The airwaves will continue to get cluttered as signals interfere with one another and get buried in the noise, and co-existence methods fail to work. Something like UWB may be just the solution. Just keep it in mind in case you need a unique wireless solution.