Ultra wideband is a wireless radio technology originally developed for secure military communications and radar that is now declassified. It is a high speed, short range wireless technology- nearly 10 times faster than IEEE802.11b. It can be used for transferring data content between devices in different entertainment and computing clusters in home, such as digital video recorders, set to boxes, televisions and PC’s. It also offers much higher bandwidth to support multimedia data streams at very low power. UWB can communicate both relative distance and position; hence it can also be used as an indoor alternate of GPS.
Unlike conventional radio systems, which operate within a relatively narrow bandwidth, the UWB radio systems operates across a wide range of the frequency spectrum by transmitting a series of extremely narrow (10-1000 per sec.) and low pulses. The low power signalling is accomplished by reusing previously allocated RF bands by hiding the signals under the noise floor of the spectrum. When properly implemented, UWB systems can share this spectrum with other traditional radio systems without causing noticeable interference & provide a highly desirable way of easing the bottleneck due to the scarcity of the radio-spectrum.
HISTORY OF ULTRAWIDEBAND TECHNOLOGY:
The development of UWB technology stems from work that was undertaken by US military into defining the behaviour of microwave networks to impulse or transients: started in 1962. The new approach of testing for UWB is to take advantage of impulse response. As UWB uses a huge bandwidth, however testing equipment with a sufficiently high bandwidth was not available at that time. Therefore R&D in this field got very less acceleration. But in 1968 it soon become obvious that UWB technology could be used for radar and communication applications, when these technologies were applied to radiating systems.
The main development in the field of UWB take place around 1970&80’s as supporting technologies become available. At that time it was known as zero-carrier or impulse technology because it does not require a dedicated radio frequency. The term Ultrawideband was later suggested by US Department of defence in 1980’s. Till this time the use of this technology was restricted for commercial use. However in 1998, the FCC recognized the significance of UWB technology and began the process of regulatory review. In May of 2000, the FCC issued a notice of proposed Rulemaking, accepting comments through the current period. Throughout early 2002, comments and review from FCC, NITA, Department of Defence and Department of Commerce were received. The FCC on 14th February 2002 decided some formal rule changes permitting UWB to operate under some restrictions. The ruling approved the limited use of unlicensed wireless systems that transmit high-speed data across a broad portion of the UWB spectrum band & allowed this technology to compete with existing WLAN & WPAN technologies.
UWB is only becoming commercially viable now through decreased costs and recent advancements in chip development, the evolution of the marketplace, and FCC recognition. What is driving UWB into the consumer market is the ability to render UWB circuitry into CMOS technology. Therefore as CMOS scales say from .25 to .18 to .13 microns so does the UWB circuitry. As a matter of fact we will see smaller and smaller UWB devices over the next few years.
UWB chipsets are currently under development and testing by several companies, including INTEL, Time Domain, XtremeSpectrum, Texas Instruments, Motorola, and STMicroelectronics and others.
UWB presents a compelling solution to many of the challenges facing today’s wireless industry.
- Limited RF spectrum availability for the evolution of wireless technologies is the real bottleneck for upcoming technologies; UWB doesn’t use an RF carrier, which opens up vast new horizon for the development of wireless technologies.
- A variation in RF spectrum assignments from one country to the next essentially prohibits the possibility of global interoperability for RF based devices. Without such RF limitations, UWB offers the promise of global interoperability.
- RF spectrum is so extensively allocated that there is no RF bandwidth available to match UWB bandwidth potential.
- Device using RF Spectrum are more complex, cost more, and consume more power than UWB.
- UWB, as it operates in “noise floor” offers greater security.
- UWB offers inexpensive Geographic Positioning.
UWB differs substantially from conventional narrowband radio frequency (RF) and spread spectrum technologies (SS), such as Bluetooth Technology and 802.11a/g. UWB uses an extremely wide band of RF spectrum to transmit data. In so doing, UWB is able to transmit more data in a given period of time than the more traditional technologies.
The potential data rate over a given RF link is proportional to the bandwidth of the channel and the logarithm of the signal-to-noise ratio (Shannon’s Law). RF design engineers typically have little control over the bandwidth parameter, because this is dictated by FCC regulations that stipulate the allowable bandwidth of the signal for a given radio type and application. Bluetooth Technology, 802.11a/g Wi-Fi, cordless phones, and numerous other devices are relegated to the unlicensed frequency bands that are provided at 900 MHz, 2.4 GHz, and 5.1 GHz. Each radio channel is constrained to occupy only a narrow band of frequencies, relative to what is allowed for UWB.
UWB is a unique and new usage of a recently legalized frequency spectrum. The UWB signal is defined as a signal with bandwidth greater than 25% of the center frequency. UWB radios can use frequencies from 3.1 GHz to 10.6 GHz—a band more than 7 GHz wide. Each radio channel can have a bandwidth of more than 500 MHz, depending on its center frequency. To allow for such a large signal bandwidth, the FCC put in place severe broadcast power restrictions. By doing so, UWB devices can make use of an extremely wide frequency band while not emitting enough energy to be noticed by narrower band devices nearby, such as 802.11a/g radios. This sharing of spectrum allows devices to obtain very high data throughput, but they must be within close proximity. UWB’s combination of broader spectrum and lower power improves speed and reduces interference with other wireless spectra. In the United States, the Federal Communications Commission (FCC) has mandated that UWB radio transmissions can legally operate in the range from 3.1 GHz up to 10.6 GHz, at a limited transmit power of -41dBm/MHz. Consequently, UWB provides dramatic channel capacity at short range that limits interference. Strict power limits mean the radios themselves must be low power consumers. Because of the low power requirements, it is feasible to develop cost-effective CMOS implementations of UWB radios. With the characteristics of low power, low cost, and very high data rates at limited range, UWB is positioned to address the market for a high-speed WPAN.
UWB technology also allows spectrum reuse. A cluster of devices in proximity (for example, an entertainment system in a living area) can communicate on the same channel as another cluster of devices in another room (for example, a gaming system in a bedroom). UWB-based WPANs have such a short range that nearby clusters can use the same channel without causing interference. An 802.11g WLAN solution, however, would quickly use up the available data bandwidth in a single device cluster, and that radio channel would be unavailable for reuse anywhere else in the home. Because of UWB technology’s limited range, 802.11 WLAN solutions are an excellent complement to a WPAN, serving as a backbone for data transmission between home clusters.
Comparison of narrowband (NB), spread spectrum (SS), and ultra-wideband (UWB) signal concepts..