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1、.外文文献原文Ultra-Wideband Technology for Short-or Medium-RangeWireless CommunicationsJeff Foerster, Intel Architecture Labs, Intel Corp. Evan Green, Intel Architecture Labs, Intel Corp. Srinivasa Somayazulu, Intel Architecture Labs, Intel Corp. David Leeper, Intel Connected Products Division, Intel Corp
2、. Index words: UWB, wireless, communications, LAN, PAN ABSTRACTUltra-Wideband (UWB) technology is loosely defined as any wireless transmission scheme that occupies a bandwidth of more than 25% of a center frequency, or more than 1.5GHz. The Federal Communications Commission (FCC) is currently workin
3、g on setting emissions limits that would allow UWB communication systems to be deployed on an unlicensed basis following the Part 15.209 rules for radiated emissions of intentional radiators, the same rules governing the radiated emissions from home computers, for example. This rule change would all
4、ow UWB-enabled devices to overlay existing narrowband systems, which is currently not allowed, and result in a much more efficient use of the available spectrum. Devices could, in essence, fill in the unused portions of the frequency spectrum in any particular location. These recent developments by
5、the FCC give Intel a unique opportunity to develop equipment that could potentially take advantage of the vast amount of usable spectrum that exists in the wireless space, and that could provide an engine to drive the future high-rate applications that are being conceived throughout this industry. I
6、ntel® Architecture Labs (IAL) is currently researching UWB technology in order to better understand its benefits, limitations, and technical challenges when used for high-rate communications. This paper introduces the reader to this technology, from potential applications to regulatory hurdles,
7、 to possible implementations and future challenges.INTRODUCTIONUltra-Wideband (UWB) technology has been around since the 1980s, but it has been mainly used for radar-based applications until now (see 1 and the references therein), because of the wideband nature of the signal that results in very acc
8、urate timing information. However, due to recent developments in high-speed switching technology, UWB is becoming more attractive for lowcost consumer communications applications (as detailed in the “Implementation Advantages” section of this paper). Intel Architecture Labs (IAL) is currently workin
9、g on an internally funded research project whose intent is to further explore the potential benefits and future challenges for extending UWB technology into the high-rate communications arena. Although the term Ultra-Wideband (UWB) is not very descriptive, it does help to separate this technology fr
10、om more traditional “narrowband” systems as well as newer “wideband” systems typically referred to in the literature describing the future 3G cellular technology. There are two main differences between UWB and other “narrowband” or “wideband” systems. First, the bandwidth of UWB systems, as defined
11、by the Federal Communications Commission (FCC) in 2, is more than 25% of a center frequency or more than 1.5GHz. Clearly, this bandwidth is much greater than the bandwidth used by any current technology for communication. Second, UWB is typically implemented in a carrierless fashion. Conventional “n
12、arrowband” and “wideband” systems use Radio Frequency (RF) carriers to move the signal in the frequency domain from baseband to the actual carrier frequency where the system is allowed to operate. Conversely, UWB implementations can directly modulate an “impulse” that has a very sharp rise and fall
13、time, thus resulting in a waveform that occupies several GHz of bandwidth. Although there are other methods for generating a UWB waveform (using a chirped signal, for example), in this paper, we focus on the impulse-based UWB waveform. but, first, a breakdown of how this paper is organized.WIRELESS
14、ALTERNATIVESIn order to understand where UWB fits in with the current trends in wireless communications, we need to consider the general problem that communications systems try to solve. Specifically, if wireless were an ideal medium, we could use it to send.1. a lot of data,2. very far,3. very fast
15、,4. for many users,5. all at once.Unfortunately, it is impossible to achieve all five attributes simultaneously for systems supporting unique, private, two-way communication streams; one or more have to be given up if the others are to do well. Original wireless systems were built to bridge large di
16、stances in order to link two parties together. However, recent history of radio shows a clear trend toward improving on the other four attributes at the expense of distance. Cellular telephony is the most obvious example, covering distances of 30 kilometers to as little as 300 meters. Shorter distan
17、ces allow for spectrum reuse, thereby serving more users, and the systems are practical because they are supported by an underlying wired infrastructure the telephone network in the case of cellular. In the past few years, even shorter range systems, from 10 to 100 meters, have begun emerging, drive
18、n primarily by data applications. Here, the Internet is the underlying wired infrastructure, rather than the telephone network. Many expect the combination of short-range wireless and wired Internet to become a fast-growing complement to next generation cellular systems for data, voice, audio, and v
19、ideo. 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
20、 licensed 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,
21、 but high spatial capacity1 as well, where spatial capacity is defined as bits/sec/square-meter. Just as the telephone network enabled cellular telephony, Trend 3 makes possible high-bandwidth, in-building service provision to low-power portable devices using short-range wireless standards like Blue
22、tooth () and IEEE 802.11 (http:/grouper.ieee.org/groups/802). 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 makes Ultra-Wideband (UWB) technology practical. When used as intended, the emergin
23、g short- and medium-range wireless standards 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
24、.11b systems can operate on a non-interfering 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-m
25、eter range and a peak over-the-air speed of 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 c
26、apacity of approximately 30,000 bits/sec/square-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 cir
27、cle with minimal degradation, for an aggregate 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 one UWB technology developer has measured peak speeds of over 50Mbps
28、at a range of 10 meters and projects that six 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 Loca
29、l Area Networks (WLANs) and Wireless Personal Area 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 appl
30、ications are the IEEE 802.11b (Wi-Fi)*, Bluetooth, and HomeRF* networking standards. As the IEEE 802.11 and ETSI BRAN HiperLAN/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 aud
31、io/video applications that are enabled by these 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 teleconferenc
32、ing applications place tough demands on the latency and jitter performance. Audio/video applications require large amounts of bandwidth and may need close synchronization (e.g., connecting stereo speakers in a surround sound system). Ultra-Wideband (UWB) systems, with their potential for extremely l
33、arge data rates over short distances, are naturally going to be used for networking these kinds of high-bandwidth/delaycritical data sources and sinks. Hence, it would be natural to look at the approaches to the MAC design undertaken in these other standards when considering the MAC layer design for
34、 UWB systems. The most important functions of the MAC layer for a wireless network include controlling channel access, maintaining Quality of Service (QoS), and providing security. 外文文献翻译 超宽带技术的短期或中期范围内的 无线通信 杰夫福斯特，英特尔架构实验室，英特尔公司 埃文格林，英特尔架构实验室，英特尔公司 斯里尼瓦萨，英特尔架构实验室，英特尔公司 大卫利珀，英特尔部连接的产品，英特尔公司关键字：超宽带，无
35、线，通讯，局域网，无源光网络摘要超宽带（UWB）技术可以大致的被定义为一个占有超过25中心频率的带宽，或者涨幅比为1.5GHz的带宽的任何无线传输方案。美国联邦通讯委员会（FCC）目前正在制定措施限制超宽带通信系统的辐射排放量，与家用电脑管理的辐射排放量相同，在无牌经营的基础上部署第15.209有目的的散热辐射规则。这一规则的改变将使UWB的可以启用的频谱更有效地利用现有的窄带系统来覆盖，并使得有用的频谱更为有效，但目前这是不允许的。本质上这些设备可以在任何特定地点频谱的未使用的部分中使用。 通过FCC最近的这些发展给了英特尔一个独特的机会来发展硬件设施，它们可以依靠存在于无线领域大量的潜在的
36、优势来利用巨大的可用频谱，而且正在提供一个用来驱动未来的高速率应用引擎的整个行业的构思。 英特尔®架构实验室（的IAL）目前正在研究超宽带技术，以更好地了解它的好处、缺陷和使用高速率通信带来的技术挑战。本文从潜在的应用程序的监管障碍到可能的实现和未来的挑战向读者介绍了这项技术。 简介 宽带（UWB）的技术流行于20世纪80年代，因为信号的宽带性质使它具有非常准确的计时信息，使它仅用于基于雷达的应用程序，然而由于在高速交换技术的最新发展，使UWB对于低成本的消费通信应用变得更加有吸引力的。英特尔架构实验室（IAL）目前正在内部资助研究项目，其目的是进一步探讨延伸到高速率通信领域超宽带技
37、术的潜在好处和未来的挑战。虽然短期超宽带（UWB）不是很有说服性，但它确实有助于从传统的“窄带”系统技术以及新的“宽带”系统通常描述中提到的未来3G蜂窝技术中分离出这种技术。UWB和其他“窄带”或“宽带”系统之间有两个的主要区别。首先，超宽带系统的带宽，如美国联邦通讯委员会（FCC）的定义，是25%以上的或超过1.5GHz的中心频率。显然，这种带宽远远大于目前任何技术所采用的通信带宽。其次，UWB是一个典型的实施载波方式。传统的“窄带”和“宽带”系统使用无线电频率（RF）基带运载在频域中的信号，并且这些系统允许被操作。相反，超宽带的实现可以直接调节一个“脉冲”，这种脉冲有一个非常尖锐的上升和下
38、降时间，因此，在占用的波形产生几个GHz的带宽。虽然产生一个UWB波形有许多其他的方法，但在本文中，我们着重叙述脉冲的超宽带波形。无线替代的手段 为了了解在无线通信中超宽带无线通信适用于哪些目前的趋势，我们需要考虑一般通信系统试图解决的问题。尤其是，如果无线是一个理想的媒介，可以用它来传送 1.大量的数据，2.远距离传输，3.传输速度快，4.多用户，5.同时性。 不幸的是，不可能寻在实现一个同时具备这五种特性的通信和双向通信流系统，如果其他的要做好，必须放弃一个或多个特性。原来的无线系统用于测量大型桥梁的距离，以便使双方联系在一起。然而，最近的一个无线电历史显示了对于其他四个属性的距离费用存在
39、明显提高的趋势。蜂窝电话系统就是最明显的例子，覆盖300米到30公里的范围。短距离允许频谱再利用，从而服务更多的用户，并且系统是可行的，因为它们是由一个基本的有线基础设施中的移动电话网络来支撑的。在过去数年，甚至更短距离系统，从10到100米，已经开始出现,带动了以数据应用为主。在这里，有线互联网是基础设施，而不是电话网络。许多人期待短距离无线和有线互联网结合成一个快速增长的补充数据，语音，音频和视频的下一代的蜂窝系统。四大趋势正在推动短距离尤其是超宽带无线通信的普及：(1)对于无线数据能力的便携式设备日益增加的对高带宽需求，以及低于目前可用技术的成本和功耗。（2）拥挤的频谱分割却以传统的方式
40、被监管部门分段和控制。（3）高速有线接入的企业，家庭上网速度，和公共空间的增长。 （4）信号处理半导体成本和功耗的收缩。趋势1和2要求系统不仅仅是提供高比特率峰值，而且还需要高容量，以及空间，其中空间容量被定义为/秒/平方米/位。正如电话功能的蜂窝电话网络，趋势3使高带宽成为可能，包括在建的服务提供低功率短距离如使用蓝牙和IEEE 802.11成为可能。最后，趋势4让这些本来在几年前不切实际技术的信号处理的使用成为了可能。，使超宽带（UWB）技术实用成为最终的趋势。按预期，新兴的短期和媒介变化无线标准各有不同，隐含的空间容量大小分配使用。例如：（1）IEEE802.11b有100米额定工作范围
41、。在2.4GHz ISM频段，可用频谱大约为80MHz。因此，在一个有100米，3 22MHz IEEE 802.11b的系统能在不干扰的基础上，各有一峰值为11Mbps的速度半径。该合计速度33Mbps，由圆的面积划分，产量约1000比特/秒/平方米的空间容量。 （2）蓝牙，是一种低功耗模式，具有在额定10米范围内，峰值在空中的1Mbps的速度。研究表明，大约10蓝牙“微网”能以最小的退化同时操作在同一个10米的圆一个10Mbps的产生总的速度。除以圆的面积这个速度产生约30,000比特/秒/平方米的空间容量。 （3）IEEE802.11a是预计有一个50米的工作范围和54Mbps的峰值速度
42、的项目。由于在5GHz范围内的U型国家信息基础设施带下部的200MHz的可用频谱，12这种系统可以同时运行在一个50米环路中，并可以聚集648Mbps的速度。预计该系统的空间容量约为83,000比特/秒/平方米。 （4）UWB系统按照他们的预测具有很大的不同功能，但有超宽带技术的开发商已经测量在10米范围和项目等六大系统可以在同一个10米半径有超过50Mbps的峰值并且只有很少的操作降解速度 。按照同样的程序，预计该系统的空间能力将超过100万比特/秒/ 平方。目前的低数据速率无线局域网（WLAN）和无线个人区域网络（WPAN）能够达到1-10Mbps的数据传输速率，通常用于诸如分组交换数据和
43、无线语音电话应用，使用时分多址（TDMA）语音电路。例如技术支持这些应用的IEEE 802.11（Wi-Fi的）蓝牙和HomeRF网络标准。由于802.11和ETSI BRAN HiperLAN / 2 *标准（相当于欧洲的802.11）已添加原始数据的物理层速率高达54Mbps规格，应用空间扩大到包括音频/视频这些数据应用的更高速率。这些不同类型的流量对于服务参数的不同有不同的条件要求，量化为每个应用程序对这些用户的网络性能。因此，例如，语音电话和视频电话会议应用在延迟和抖动性能方面有严格要求。音频或者视频的应用需要大量带宽，可能需要关闭同步（例如，连接立体声扬声器环绕声系统）。超宽带（UWB）系统，与他们在短距离上相比具有非常大的数据速度的潜力，自然是要为网络的数据源和汇聚高宽带这类使用。因此，这将是在向MAC设计时考虑这些超宽带系统的MAC层设计等标准进行。 MAC层最重要的无线网络功能，包括信道接入控制，保持服务质量（QoS），并提供安全性。:15