17、llow for spectrum reuse, thereby serving more users, and the systems are practical because they are supported by an underlying wiredin frastructure- the tele phone n etwork in the case of cellular. I n the past few years, even shorter range systems, from 10 to 100 meters, have begun emerging, driven 。

18、 primarily by data applications. Here, theInternet is the underlying wired infrastructure, rather than the telephone network. Many expect the combination of short-range wireless and wired Internet tobecome a fast-growing complement to next generation cellular systems for data, voice, audio, and vide 。

19、o. Four trends are driving short-range wireless in general and ultra-wideband in particular:1. The growing demand for wireless data capability in portable devices at higher bandwidth but lower in cost and power consumption than currently available.2. Crowding in the spectrum that is segmented and li 。

20、censed by regulatory authorities in traditional ways.3. The growth of high-speed wired access to the Internet in enterprises,homes, and public spaces.4. Shrinking semiconductor cost and power consumption for signal processing.Trends 1 and 2 favor systems that offer not just high-peak bit rates, but。

21、high spatial capacity1 as well, where spatial capacity is defined asbits/sec/square-meter. Just as the telephone network enabled cellulartelephony, Trend 3 makes possible high-bandwidth, in-building service provision to low-power portable devices using short-range wireless standards like Bluetooth ( 。

22、) and IEEE 802.11 (). Finally, Trend 4 makes possible the use of signal processing techniques that would have been impractical only a few years ago. It is this final trend that makesUltra-Wideband (UWB) technology practical. When used as intended, the emerging short- andmedium-range wireless standar 。

23、ds vary widely in their implicit spatial capacities. For example :1.IEEE 802.11b has a rated operating range of 100 meters. In the 2.4GHz ISM band, there is about 80MHz of useable spectrum. Hence, in a circle with a radius of 100 meters, three 22MHz IEEE 802.11b systems can operate on a non-interfer 。

24、ing basis, each offering a peak over-the-air speed of 11Mbps. The total aggregate speed of 33Mbps, divided by the area of the circle, yields a spatial capacity of approximately 1,000 bits/sec/square-meter.2. Bluetooth, in its low-power mode, has a rated 10-meter range and a peak over-the-air speed o 。

25、f 1Mbps. Studies have shown that approximately 10 Bluetooth “piconets ” can operate simultaneously in the same 10 meter circle with minimal degradation yielding an aggregate speed of 10Mbps 3. Dividing this speed by the area of the circle produces a spatial capacity of approximately 30,000bits/sec/s 。

26、quare-meter.3.IEEE 802.11a is projected to have an operating range of 50 meters and a peak speed of 54Mbps. Given the 200MHz of available spectrum within the lower part of the 5GHz U-NII band, 12 such systems can operate simultaneously within a 50-meter circle with minimal degradation, for an aggreg 。

27、ate speed of 648Mbps. The projected spatial capacity of this system is therefore approximately 83,000 bits/sec/square-meter.4.UWB systems vary widely in their projected capabilities, but oneUWB technology developer has measured peak speeds of over 50Mbps at a range of 10 meters and projects that six 。

28、 such systems could operate within the same 10-meter radius circle with only minimal degradation.Following the same procedure, the projected spatial capacity for this system would be over 1,000,000 bits/sec/square-meterCurrent low data-rate Wireless Local Area Networks (WLANs) andWireless Personal A 。

29、rea Networks (WPANs), which have data rates of 1- 10Mbps, are typically used for applications such as packet-switched data and cordless voice telephony, using Time Division Multiple Access (TDMA) voice circuits. Example technologies supporting these applications are the IEEE 802.11b (Wi-Fi)*, Blueto 。

30、oth?, and HomeRF*networking standards. As the IEEE 802.11 and ETSI BRANHiperLAN/2* standards (the European equivalent of 802.11) have added physical layer specifications with raw data rates up to 54Mbps, the application space is enlarging to include audio/video applications that are enabled by these 。

31、 higher data rates. These diverse traffic types all have different requirements in terms of the service parameters that quantify the network performance for a user of each of those applications. Thus, for example, voice telephony and video teleconferencing applications place tough demands on the lat 。

【外文|外文翻译-超宽带技术的短期或中期范围内的无线通信】32、ency and jitter performance. Audio/video applications require large amounts of bandwidth and may need close7synchronization (e.g., connecting stereo speakers in a surround sound system). Ultra-Wideband (UWB) systems, with their potential for extremely large data rates over short distances, are natur 。

来源：(未知)

【学习资料】网址：/a/2021/0322/0021748020.html

标题：外文|外文翻译-超宽带技术的短期或中期范围内的无线通信( 二 )