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Competing for throughput in the local loop

机译:竞争本地环路中的吞吐量

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The voice-grade telephone channel is the communication medium most widely available throughout the world. Its limitations, a relatively narrow bandwidth and a moderate SNR figure, have challenged telecommunication researchers and engineers over several decades to develop technologies able to pass higher and higher data rates. The sophisticated combination of trellis coding and quadrature amplitude modulation increases the bandwidth utilization close to the Shannon limit of 10 b/s/Hz for the 3.1 kHz bandwidth voice channel. However, the resultant data rate of about 30 kb/s does not even begin to approach the throughput needed by multimedia applications. Fortunately, twisted pair bandwidth reaches up to several megahertz, so multilevel signaling implemented as in the xDSF family of modems enables data rates of several megabits per second to be reached. Standard ADSL modems are able to deliver 8 Mb/s to a subscriber in the best case. VDSL modems can deliver 52 Mb/s, but only up to 300 m, so their mass implementation will only become possible when fiber migrates into an access network closer to the user premises. Both broadband xDSL solutions approach the Shannon limit and the related spectral efficiency as well, so there is not much room left for a transmission improvement.
机译:语音级电话信道是全世界使用最广泛的通信介质。它的局限性,相对较窄的带宽和适中的SNR数,在过去的几十年中一直挑战着电信研究人员和工程师,以开发能够通过越来越高的数据速率的技术。网格编码和正交幅度调制的复杂结合提高了带宽利用率,接近3.1 kHz带宽语音通道的Shannon极限10 b / s / Hz。但是,大约30 kb / s的最终数据速率甚至没有开始接近多媒体应用程序所需的吞吐量。幸运的是,双绞线带宽可达到几兆赫兹,因此,如xDSF系列调制解调器中所实现的多级信令可以达到每秒几兆比特的数据速率。在最佳情况下,标准ADSL调制解调器能够向订户提供8 Mb / s的速度。 VDSL调制解调器可以提供52 Mb / s的速度,但只能达到300 m,因此,只有在光纤迁移到更靠近用户房屋的接入网络中时,它们的大规模实现才有可能实现。两种宽带xDSL解决方案都接近Shannon极限和相关的频谱效率,因此,没有多少空间可以改善传输。

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