<font color=orange>UWB Exceeds 1 Gbps
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The pace of development is picking up for the next generation in wireless communication technology, such as high-speed wireless local area networks (LAN) over 100Mbps and Ultra-Wideband (UWB) for short-range, ultra-high speed communications. This stance is well expressed in recent standardization activity at the IEEE802 LAN/MAN Standards Committee. At the meeting in March 2003 three major developments attracted attention, namely (1) IEEE802.15.3a, in charge of UWB standardization, received technology proposals from over 20 manufacturers and research institutions, including Sony Corp of Japan (Table 1); (2) IEEE802.11n, working on high-speed LAN offering throughputs of 1,000Mbps (effective data transfer rate) began work; and (3) IEEE802.20, investigating next-generation mobile communications, began technology evaluation.
Utilization Wavebands
Individual firms are taking entirely different approaches to controlling UWB interference, which has been viewed as a major problem. The scheme is to avoid using the 5GHz waveband already in use by IEEE802.11a for datacom at rates up to 54Mbps. Numerous technical proposals recommend using multiple sub-bands to avoid the 5GHz band.
XtremeSpectrum, Inc of the US has submitted a technology proposal using two wavebands, the "low band" from 3.1 to 5.15GHz with a peak throughput of 400Mbps, and the "high band" from 5.825 to 10.6GHz with double the throughput. When both bands are used at once, the peak data transfer rate hits 1.2Gbps (Fig 1).
XtremeSpectrum apparently chose to use two wavebands to make it possible to use a simpler transceiver circuit. The firm points out that a transceiver circuit is required for every waveband used, and that circuit scale and complexity increase with the number of frequencies.
The method proposed by XtremeSpectrum calls for different modulation schemes above and below 400Mbps. In the low band they use binary phase shift keying (BPSK), while quadrature phase shift keying (QPSK) is used for high-speed transfers. Due to the relation between waveband and range, a transfer rate of 114Mbps works out to a 22.4 meter range in the low band, and 11.1 meters (about half) in the high band.
3Gbps Possible
Sony has defined three channels within the total bandwidth, cleverly avoiding the 5GHz waveband entirely. In his presentation, Robert Huang of Sony Electronics of the US (one of the people making the proposal) expressed his expectations for the future, commenting, "We will never again have the opportunity to use this level of resources. We have to utilize them effectively."
The three center frequencies are 4, 7 and 9GHz, and each channel has a bandwidth of 1.8GHz. The throughput can be extended as high as 3Gbps depending on encoding selection. Signals at various frequencies are transferred via signal carrier, because the signal carrier scheme transmits high energy levels. The firm compared a number of modulation techniques for multipath interference, finally selecting direct sequence spread-spectrum (DSSS) technology. The firm cited the major reasons for its choice were that the technology is understood, easy to implement and easy to tweak for high performance.
Sony also commented on productization, demonstrating its high interest in UWB with a roadmap calling for a 2-chip implementation in the 2nd quarter of 2005 and a single-chipped design in the 4th quarter of the same year.
Multiband Solutions
Multiband technology, the most common solution to interference, has been adopted already by Intel Corp of the US and four other firms, and recently three companies followed suit: Focus Enhancements, Inc of the US, Philips Electronics of the Netherlands, and Samsung of Korea. At the meeting one source revealed that the number of supporters has reached 13, including a few who haven't gone public yet. The goal is to become the standard through weight of numbers, because only standard proposals supported by at least 75% of participants will survive. Other than the multiband group, XtremeSpectrum will be cooperating with Motorola, Inc of the US, but no other official tie-ups have been announced.
Robert Heile, chairman of IEEE802.15.3a, said, "The current schedule calls for an intermediate meeting in May 2003 to announce additional details and hold a Q&A session, with voting in July 2003." The past meeting allotted each firm 40 minutes for its presentation, and Heile mentioned that discussion was not complete because some Q&A sessions had to be cut short for lack of time.
From HTSG to 11n
IEEE802.11n, which is investigating next-generation high-speed wireless LAN standards, evolved from the High Throughput Study Group (HTSG) after about a year of preparation.
The key goal is to achieve throughput of 100Mbps, and once that is attained, according to a Japanese engineer in the field, "We will need data transfer rates equivalent to 200 or 250Mbps." He explained that throughput is the primary development target here because of the large difference between transfer rate and perceived speed. HTSG chairman Jon Rosdahl of Micro Linear Inc of the US explained, "Neither the IEEE802.11b standard at 11Mbps nor the IEEE802.11a/g standards at 54Mbps actually hit those nominal rates. The perceived speed is quite a bit different, and users aren't satisfied. That's why we set the standard for a throughput close to what we want for the perceived speed." In actuality, the rate defined in IEEE802 is the speed of the media access control (MAC) data at the data frame service access point (SAP). There are still a number of points to be hammered out, though, such as frequency utilization waveband.
For point (3), next-generation mobile, IEEE802.20 was launched in January 2003 and has already begun investigation of new mobile technologies. Mark Klerer of Flarion Technologies of the US, serving as provisional chairman, commented, "The third-generation mobile phone systems being installed in Japan were originally designed to handle voice, with circuit switching. IEEE802.20 is designed to standardize a mobile communication technology running on datacom systems." The group has not yet started work on utilization frequency or data rate.
by Takahiro Kikuchi
Websites:
Discrete Time Communications: discretetime.com
Flarion Technologies: flarion.com
Focus Enhancements: focusinfo.com
Intel: intel.com
Micro Linear: microlinear.com
Motorola: motorola.com
Philips Electronics: philips.com
Sony Electronics: sonystyle.com
XtremeSpectrum: xtremespectrum.com
(June 2003 Issue, Nikkei Electronics Asia)
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