| 单词 | 802.11a |
| 释义 | 802.11a Also known as Wi-Fi5 ( Wi reless Fi delity 5 GHz). The IEEE standard for an 802.11 wireless local area network (WLAN) operating in the 5-GHz range. 802.11a uses coded orthogonal frequency division multiplexing (COFDM), which sends a stream of data symbols in a massively parallel fashion across multiple subcarriers, each of which is 20 MHz wide and is subdivided into 52 subcarrier channels, each of which is approximately 300 KHz wide. Of those subcarrier channels, 48 are used for data transmission, and the remaining 4 for error control. The specific modulation scheme depends on link quality, with the highest link quality employing the most complex technique, which yields the greatest signaling rate.As the link quality deteriorates, the modulation technique ratchets down to the least capable. In order of complexity and yield, those techniques are as follows: • Binary phase-shift keying (BPSK) at 125 kbps per channel for a total of 6 Mbps (125 kbps × 48 channels = 6 Mbps), and 187.5 kbps for a total of 9 Mbps • Quadrature phase-shift keying (QPSK) at 250 kbps per channel for a total of 12 Mbps, and 375 kbps per channel for a total of 18 Mbps 74570cintro.qxd 9/11/07 12:17 PM Page 13 |
| 随便看 |
|
科学参考收录了5291条科技类词条，基本涵盖了常见科技类参考文献及英语词汇的翻译，是科学学习和研究的有利工具。