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| Technical FAQ |
| Q1. Do we really need yet another wireless technology? Q2. What is Ultra-wideband (UWB)? Q3. What is IEEE 802.15.3 and 802.15.3a? Q4. What is the MultiBand OFDM Alliance? Q5. What is CSM? Q6. Why CSM? Q7. What are the advantages and drawbacks of UWB technology? Q8. What are the potential commercial applications? Q9. When do you predict we’ll have the first multimedia products on the market with UWB inside? Q10. How different is UWB from other WLAN/WPAN technologies? Q11. What about Bluetooth? Q12. How much would a product with UWB cost versus one without it or with a competing wireless technology? Q13. How much would a product with CSM cost versus one without it or with just one alternate UWB PHY? Q14. What is the level of interference caused by an ultra-wideband system? Q15. How do you implement channelization or “multiple piconets” with UWB? Q16. Is UWB a replacement for wireless LAN? Or isn’t it powerful enough for those types of applications? Q1. Do we really need yet another wireless technology? A. In order to deliver on the promise of the unwired home…wireless distribution of everything from television programs, movies and games to megabit intensive data files, you need a “fat pipe.” That’s what UWB provides. You also need to be certain that the transfers won’t interfere with other wireless transmissions or be interfered with; and UWB provides that. Plus it’s low power. We need it because, while we’ve talked about routing video and other high bandwidth applications around the home without the pain of cables and wires, we haven’t been able to do it because the current technologies, like WLAN just aren’t fast enough.Ultra-wideband, also known as impulse or carrierless radio technology, is one of the most promising radio technologies of our time. Unlike conventional radio systems, which operate within a relatively narrow bandwidth, ultra-wideband operates across a wide range of frequency spectrum by transmitting a series of extremely narrow (10 – 1000ps) and low power pulses. The DARPA study panel, that coined the term ultra-wideband in the 1990’s, defines it as a system with the occupied bandwidth is greater than 25% of the center frequency. Ultra-wideband should not be confused with spread spectrum technology, which is used by other WLAN standards such as 802.11b. Q2. What is Ultra-wideband (UWB)? A new emerging radio design standard. The term “ultra-wideband,” comes from the fundamental physics benefits of radios designed to use coherent wide-relative-bandwidth propagation, which has no Rayleigh fading, which are different from many popular radio designs today which seriously degraded by fading. Because of this no-fading benefit, Ultra-wideband can operate further and faster than conventional wisdom would expect and results in extremely simple architectures that can deliver extremely high speed radios. Indeed, US regulatory events that allow commercial usage of this technology stemmed from a wireless system approach that proved that wide contiguous spectrum, coherently processed, could capture these unique benefits and provide utility unobtainable with narrowband. The efforts of the UWB Forum are to offer better performance (approaching theoretical aggregate limits) with less complexity, at lower prices and lower power consumption levels, hence better meeting the needs of the IEEE 802.15.3a Task Group and industry. Q3. What is IEEE 802.15.3 and 802.15.3a? A. 802.15.3 is the IEEE standard for high data rate WPAN designed to provide Quality of Service (QoS) for real time distribution of multimedia content, like video and music. It is ideally suited for a home multimedia wireless network. The original standard uses a “traditional” carrier-based 2.4 GHz radio as the physical layer (PHY). A follow-on standard, 802.15.3a, is still in the formative stages. It will define an alternative PHY, current candidate proposals are based on UWB, that will provide in excess of 110 Mbps at a 10m distance and 480 Mbps at 2m. This will allow applications requiring streaming of high-definition video between media servers and flat screen HD monitors and extremely fast transfer of media files between media servers and portable media devices. Q4. What is the Multi-Band OFDM Alliance? A. The Multi-Band OFDM Alliance (MBOA) is a trade alliance of proponents of a band hopping OFDM solution in IEEE 15.3a committee for a high data rate UWB Personal Area Network (PAN). MB-OFDM seeks to access the UWB spectrum by aggregating 122 QPSK modulated narrow band carriers to attempt to meet the FCC/NTIA mandated 500 MHz minimum bandwidth requirement. MB-OFDM is one of the possible modulations that are supported by the Common Signalling mode (CSM) proposed by the UWB Forum. Q5. What is CSM? A. A Common Signaling Mode (CSM) for Ultra-wideband Radios has been contributed to the IEEE. In general the UWB Forum is supportive of contributions that will move the down-selection process forward. In specific terms the UWB Forum is supportive of developing a single standard that allows compliant UWB devices to use various different radio designs, yet still allows all compliant devices to interoperate and coordinate their use of the shared UWB spectrum. Q6. Why CSM? A. In general, it is not possible for two different devices based on different UWB radio designs to inter-operate with each other because the PHY layer signals are so different. CSM is a technique that allows these two classes of devices to operate together to both avoid interference and allow inter-operability. The Common Signaling Mode (CSM) is a signaling technique that has been designed to allow these different devices to communicate with each other in order to coordinate their actions and interoperate within the same wireless network. This ability for two different classes of unlicensed devices to peacefully co-exist and even interoperate is an extremely powerful concept. The current situation with multiple classes of emerging UWB devices is really just a sign of things to come – some advocates have even described a vision of even more diverse radio devices sharing and coordinating spectrum usage between devices across wide frequency bands. This vision can only come to pass if co-existence mechanisms and inter-communication are built into devices from the beginning. Q7. What are the advantages and drawbacks of UWB technology? A. The primary advantages of UWB are high data rates, low cost, and low power. UWB also provides less interference than narrowband radio designs, while yielding a low probability of detection and excellent multipath immunity. When combined with the 802.15.3 PAN standard, UWB will provide a very compelling wireless multimedia network for the home. It will have the ability to support multiple devices, and even multiple independent piconets, so nearby neighbors will not interfere with other UWB networks. An additional feature of UWB is that it provides for precise ranging, or distance measurement. This feature can be used for location identification in, for example, public safety applications. The basic drawback of UWB is that, under current FCC regulations, it is limited to 10, or a few 10s of meters, depending on the desired data rate. This is consistent with the intended application as a PAN technology. Whole home coverage in larger homes may require an additional networking technology, such as a metal backplane (i.e. cable, or power line) or mesh networking from room to room. Q8. What are the potential commercial applications? A. Ultra-wideband is capable of being used in a multitude of commercial applications ranging from wireless networks (scalable from low to ultra high speeds) to remote sensing and tracking devices, ground penetrating radars, as well as many more applications that have yet to be invented. Consumers will most immediately benefit from UWB that is optimized for wireless home networks. This architecture allows multimedia-enabled devices to send and receive multiple streams of digital audio and video at price points and power consumption levels currently unattainable with existing solutions. Q9. When do you predict we’ll have the first multimedia products on the market with UWB inside? A. Ultra-wideband products were on display at the Consumer Electronics Show in January 2004, and are expected to be commercially available some time later in 2005. Q10. How different Ultra-wideband from other WLAN/WPAN technologies? A. UWB is the only technology today that can achieve data rates significantly in excess of 54Mbps at power consumption levels and price points amenable to battery-powered consumer appliances, i.e. digital cameras, flat panel displays, etc. In addition, UWB presents some astonishing properties in terms of coexistence, multipath immunity for indoor environments, and security. Q11. What about Bluetooth? A. Bluetooth, like UWB is a wireless personal area networking technology. The data rates delivered are significantly different and therefore the application spaces addressed by each technology are different. Like other application-specific technologies, it is likely that UWB and Bluetooth could both be integrated into end-devices to serve these different application spaces. Q12. How much would a product with UWB cost versus one without it or with a competing wireless technology? A. One of the fundamental advantages of UWB is that it eliminates many of the analog and mixed signal components of traditional carrier wave based radios. It is an “all digital” radio and can take advantage of Moore’s Law scaling. Once it is fully developed, it is destined to become a very low cost solution, particularly considering the data rates it can support. Q13. How much would a product with CSM cost versus one without it or with just one alternate UWB PHY? A. It is expected devices would require only a little, if any, additional cost to support proposed CSM concepts. In nearly every case, both devices would already contain the required signal processing blocks to support the low-complexity common mode used for inter-operability. Q14. What is the level of interference caused by an ultra-wideband system? A. The levels of interference are low, due to the low power limitations set by the FCC. However, the level also depends on the type of UWB you’re talking about. The signals of most Ultra-wideband impulse radios generally appears as white noise to to other radios in operation in these lower spectrums. Other types of UWB, such as gated, or frequency hopped signals, can cause more noise, depending on the nature of the victim receiver. It is interesting to note that despite the hype, most UWB systems transmit power is lower than what a standard PC is allowed to radiate unintentionally. It then spreads the power over an extremely wide swath of radio spectrum. A UWB transmitter can distribute its energy over the equivalent of 1000 TV channels, or 30,000 FM channels, or a-half-million walkie-talkie frequencies. This makes the UWB signal at any one frequency extremely small. Because of their low power spectrum density, unlicensed UWB radios will cause no interference to other radio systems operating in dedicated bands. Q15. How do you implement channelization or “multiple piconets” with UWB? A. Multiple piconets refers to the mechanisms used to share the channel between multiple independent sets of networking devices, allowing those different systems to operate within the same space without interference. Here again, there are several different ways to implement multiple access. Besides the traditional Frequency Division Multiplexing (FDM) or Time Division Multiplexing (TDM), one could use Code-Division Multiplexing (CDM) or even Frequency Hopping (FH) schemes. DS-UWB uses a combination of code division, offset operating frequencies, and FDM to allow multiple piconets to appear as white noise to each other. This approach allows graceful sharing of common frequency bands while minimizing the interference potential to other systems. Q16. Is UWB a replacement for wireless LAN? Or isn’t it powerful enough for those types of applications? A. WLAN, (802.11) is becoming pervasive as a wireless data networking technology and will be around for a long time. It is well suited for these applications in terms of range and data rates. However, .11 is not well suited for the multimedia PAN applications that UWB is aimed at. The data rates are not high enough, the power consumption is too high, and the .11 network architecture can not support multiple independent networks. With multimedia, multiple streams of video, audio, etc., insuring high quality delivery is probably the most important element, and .11 does not address this. |
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