| An introduction to Ultra Wideband (UWB) wireless |
by Rafael Kolic (Feb. 24, 2004)
Intel recently outlined plans to drive the development of a complete, standards-based, common platform for ultra wideband (UWB) wireless technology. Intel says future UWB technology-based products built on this platform will enable high-speed transfer of multimedia content between devices in the home or office, at lower costs and without the hassle of wires. This whitepaper by Rafael Kolic, a technology marketing manager in Intel's Corporate Technology Group, introduces Ultra Wideband (UWB) wireless, its applications, and its underlying technologies.
Ultra Wideband -- the Next-Generation Wireless Connection
by Rafael Kolic
Overview: Transitioning to the Real World
In the digital home of the not-too-distant future, people will be sharing photos, music, video, data and voice among networked consumer electronics, PCs and mobile devices throughout the home and even remotely. For example, users will be able to stream video content from a PC or consumer electronics (CE) device -- such as a camcorder, DVD player or personal video recorder -- to a flat screen HDTV (high-definition television) display without the use of any wires.
A leading candidate for enabling this capability is ultra wideband (UWB), a wireless technology designed for short-range, personal area networks, or PANs. This year, UWB is making the transition from laboratories to standardization, a key step toward the development of real-world products.
Recent industry achievements with UWB range from researchers showing proof-of-concept demos, to formation of industry working groups that will define the UWB physical layer (PHY) and MAC layer and applications that will run on top of the radio platform. In the U.S., the Federal Communications Commission (FCC) has mandated that UWB radio transmission can legally operate in the range from 3.1 GHz to 10.6 GHz, at a transmit power of –41 dBm/MHz. Japanese regulators have issued the first UQWB experimental license allowing the operation of a UWB transmitter in Japan.
Digital Home Requirements
Why is UWB considered by many to be the next "big thing" in the wireless space? For one thing, it allows for high data throughput with low power consumption for distances of less than 10 meters, or about 30 feet, which is very applicable to the digital home requirements. The fastest data rate publicly shown over UWB is now an impressive 252 Mbps, and a rate of 480 Mbps is expected to be shown in the not-too-distant future.
Requirements for the digital home include high-speed data transfer for multimedia content, short-range connectivity for transfer to other devices, low power consumption due to limited battery capacity, and low complexity and cost due to market pricing pressures and alternative wired connectivity options. Transfer of video from a camcorder to an entertainment PC is one scenario. Another model is the ability to view photos from the user's digital still camera on a larger display. Removing all the wires to the printer, scanner, mass storage devices, and video cameras located in the home office is another possible scenario.
Closely related is wireless connectivity for consumer electronics devices. Portable CE audio/video (A/V) devices such as DV camcorders, digital still cameras, portable MP3 audio players, HDTV displays, personal video recorders (PVRs), Entertainment PCs and emerging personal video players are likely candidates for the early UWB mainstream market.
Wider Applications of UWB
The concept of a UWB radio spans many different applications and industries and has been coined the "common UWB radio platform." The UWB radio, along with the convergence layer, becomes the underlying transport mechanism for different applications, some of which are currently only wired. Some of the more notable applications that would operate on top of the common UWB platform would be wireless universal serial bus (WUSB), IEEE 1394, the next generation of Bluetooth, and Universal Plug and Play (UPnP). You can see a diagram of this vision in Figure 1.
This concept has many potential applications since it creates the first high-speed wireless interconnects. UWB technology offers a combination of performance and ease of use unparalleled by other interconnect options available today.
Presently, wired USB has significant market segment share as the cable interconnect of choice for the PC platform. But the need for the cable itself points to convenience and usability challenges for users. By unleashing peripheral devices from the PC while still providing the performance users have come to expect from wired USB connections, wireless USB running on ultra wideband promises to gain significant volume in the PC peripheral interconnect market segment.
An example application for UWB would be bringing a mobile device like a portable media player (PMP) in proximity to a content source like a PC, laptop, or external hard disk drive. Once authentication and authorization is established, the device and PC can perform bulk data transfer of video files onto the PMP for later viewing.
Within the consumer electronics industry, there is demand for wirelessly connecting various devices such as DVDs, HDTVs, set-top boxes (STBs), PVRs, stereos, camcorders, digital cameras, and other CE devices. Wireless ease of use and data transfer performance is a key factor for adoption in this category.
For example, wireless connectivity would be ideal for a wall-mounted plasma display where, for aesthetic reasons, users prefer not to have cables from an STB or Entertainment PC visible. A variation on this usage model is the ability to stream content to multiple devices simultaneously. This would allow picture-in-picture functionality or viewing of the same or different content on multiple viewing devices.
A Closer Look at UWB Technology
A traditional UWB transmitter works by sending billions of pulses across a very wide spectrum of frequency several GHz in bandwidth. The corresponding receiver then translates the pulses into data by listening for a familiar pulse sequence sent by the transmitter. Specifically, UWB is defined as any radio technology having a spectrum that occupies a bandwidth greater than 20 percent of the center frequency, or a bandwidth of at least 500 MHz.
Modern UWB systems use other modulation techniques, such as Orthogonal Frequency Division Multiplexing (OFDM), to occupy these extremely wide bandwidths. In addition, the use of multiple bands in combination with OFDM modulation can provide significant advantages to traditional UWB systems. The MultiBand OFDM approach allows for good coexistence with narrowband systems such as 802.11a, adaptation to different regulatory environments, future scalability and backward compatibility. This design allows the technology to comply with local regulations by dynamically turning off subbands and individual OFDM tones to comply with local rules of operation on allocated spectrum.
With the formation of the MultiBand OFDM Alliance (MBOA) in June 2003, OFDM for each subband was added to the initial multiband approach in order to develop the best technical solution for UWB. To date, the MultiBand OFDM Alliance has more than 60 participants (and growing) that support a single technical proposal for UWB.
In the MultiBand OFDM approach, the available spectrum of 7.5 GHz is divided into several 528-MHz bands. This allows the selective implementation of bands at certain frequency ranges while leaving other parts of the spectrum unused. The dynamic ability of the radio to operate in certain areas of the spectrum is important because it can adapt to regulatory constraints imposed by governments around the world.
The band plan for the MBOA proposal has five logical channels (see Figure 2). Channel 1, which contains the first three bands, is mandatory for all UWB devices and radios. Multiple groups of bands enable multiple modes of operation for MultiBand OFDM devices. In the current MultiBand OFDM Alliance's proposal, bands 1–3 are used for Mode 1 devices (mandatory mode), while the other remaining channels (2–5) are optional. There are up to four time-frequency codes per channel, thus allowing for a total of 20 piconets with the current MBOA proposal. In addition, the proposal also allows flexibility to avoid channel 2 when and if U-NII (Unlicensed-National Information Infrastructure) interference, such as from 802.11a, is present.
OFDM Modulation
The information transmitted on each band is modulated using OFDM. OFDM distributes the data over a large number of carriers that are spaced apart at precise frequencies. This spacing provides the orthogonality in this technique, which prevents the demodulators from seeing frequencies other than their own. The benefits of OFDM are high-spectral efficiency, resiliency to RF interference, and lower multipath distortion.
By using OFDM modulation techniques coupled with multibanding, it becomes easier to collect multipath energy using a single RF chain and allows the receiver to deal with narrowband interference without having to sacrifice subbands or data rate. These advantages relate to the ability to turn off individual tones and also easily recover damaged tones through the use of forward error-correction coding.
Manufacturing Considerations
Although this adds complexity to the design of the radio, it is important to note that the key signal-processing block in OFDM (the FFT/IFFT) has been shown to require around 50K gates, which contribute only a very small area to the total silicon real estate. Furthermore, the functionality can be integrated in deep submicron CMOS processes, resulting in Moore's Law scaling for the majority of the receive-path functions.
Summary
Researchers and engineers are working to deploy UWB technology in the near future. With the standardization of a common UWB development platform, device manufacturers in the PC, mobile, and consumer electronics industries will have the opportunity to choose UWB as a physical layer. By doing so, they will be able to take advantage of the low power and high bandwidth this technology provides.
Intel researchers are working on a variety of UWB technologies, including a platform for next-generation development efforts, and believe it will be a critical step in enabling advanced communications for a wide range of uses in the future.
More Info
Intel announced plans to drive the development of a complete, standards-based, common platform for ultra wideband at the Spring 2004 Intel Developer Forum.
Read the following Intel articles and white papers for more detailed explanations of the underlying technology: You can also visit these sites to explore more information:
 About the author: Rafael Kolic is a technology marketing manager in the Communications Technology Lab, part of Intel's Corporate Technology Group. Since joining Intel in 2000, he has worked on a number of projects involving ultra wideband, wireless USB, USB 2.0, UPnP, and several other technologies. Kolic has also performed research in the area of power electronics. He holds an M.E. in electrical and computer engineering and a B.S. in electrical engineering from the University of Florida.
Copyright © Intel Corporation 2003-2004. All rights reserved. Reproduced by DeviceForge.com with permission. This article was originally published in Intel's Technology@Intel Magazine.
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