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UWB: Still a Viable Wireless Option

UWB: Still a Viable Wireless Option

Multiple 528 MHz bands were invented to cover the FCC’s designated UWB spectrum from 3.1 to 10.6 GHz. (Image courtesy of Thinkstock)

In my blog of September 2ndWhatever Happened to Ultrawideband Wireless?   I only mentioned the WiMedia Alliance’s multi-band (MB)-OFDM form of UWB and its continued usefulness.  However, two other companies reminded me that there are other methods of UWB that are still around.  Here is a quick look at what else is happening in UWB.

UWB started out as an impulse form of wireless.  Short wavelets are transmitted to represent bits using pulse position or phase.  That form of UWB has its problems for some applications but it is still used in ground penetrating radar gear.  Then a group of manufacturers invented MB-OFDM UWB to fit the FCCs’ definition of UWB.  Known as WiMedia, this form structured OFDM to ensure it met the minimum of 500 MHz bandwidth requirement of the definition of UWB.  The WiMedia format uses 128 OFDM subchannels each 4.125 MHz wide to create a 528 MHz OFDM UWB signal modulated with BPSK or QPSK.  Multiple 528 MHz bands were invented to cover the FCC’s designated UWB spectrum from 3.1 to 10.6 GHz.

The standard received a huge amount of support and about a dozen companies started making chips.  The goal was to create a wireless USB device.  And most of them did but only a few were ever commercially successful.  Because of the complexity of the WiMedia UWB and its speed and range short comings, it never became mainstream.  With 802.11n Wi-Fi coming along about the same time, WiMedia UWB quickly faded away.  But, as I pointed out in the earlier blog, this form of UWB from Alereon has unusually good security characteristics so is now finding application in military and medical applications.

Paul Dillon of Pulse~LINK informed me that there is another promising UWB form is called CWave.  Invented by Pulse~LINK, this method is far simpler than the WiMedia standard and offers some interesting features and benefits that are worthy of note. CWave uses a continuous 4 GHz carrier modulated by a 1.35 Gb/s digital signal creating the familiar sin(x)/x shaped spectrum with the major nulls at 2.7 and 5.3 GHz.  This spectrum is then filtered into a band pass from 3.3 to 4.7 GHz meeting the FCC’s requirement.  The modulation is BPSK.  This arrangement supports a 1.35 Gb/s data rate.  CWave uses the popular Low Density Parity Check (LDPC) coding to provide some process gain.  This results in a 900 Mb/s net data rate over short ranges.

CWave is really simple compared to the WiMedia format.  It does not need all the super fast ADCs and DACs, equalization, or fast FFT/IFFT processing.  As a result, it features less circuitry and much lower power consumption.  It does not require a PA.  Power level is still the -41 dBm/MHz.  At this power level, the range is still restricted as with any UWB but up to 10 meters can be achieved under ideal conditions at lower speeds.

The neat thing about CWave is that the carrier can be placed anywhere within the UWB band.  In addition higher levels of modulation like QPSK or 8PSK can boost gross data throughput to 2.7 Gb/s or 4.05 Gb/s respectively. As for wireless applications, CWave is good for in-room video streaming or USB connections.  It also fits some medical and military uses.

A unique application of Pulse-Link’s CWave is UWB over cable.  Yes, cable.  It can carry Ethernet over coax for example.  CWave apparently operates well over the home-installed 75-ohm coax (RG-59/U and RG-6/U including splitters.  In addition it could find a way into cable TV or satellite TV systems as the signal can be positioned higher than the current DOCSIS or satellite spectrum (above 2 GHz) on the cable.  Pulse-Link has basic chipsets now with a GEN2 version on the way. 

Another interesting UWB still around is impulse radio (IR) UWB.  It uses the short Gaussian pulses for real time location systems (RTLS).  Dublin-based DecaWave as created both chips and modules using this method.  Their DW1000 IC operates on one of six channels in the 3.5 to 6.5 GHz range with a bandwidth of 500 MHz to meet the UWB definition.   Data rates of 110 kb/s, 850 kb/s and 6.8 Mb/s are available.  The chip is fully compliant to the IEEE’s 802.15.4-2011 standard that added the UWB PHY.  The chips, called ScenSor, are designed to build location-based devices.  With the short pulse technology, the chips and modules can locate items within 10 cm.  Amazing. 

CWave and ScenSor devices are certainly worth a look if you are considering fast short-range wireless technologies.

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