问题
单项选择题
In the following essay, each blank has four choices. Choose the best answer and write down on the answer sheet.
Spread spectrum simply means that data is sent in small pieces over a number of the (16) frequencies available for use at any time in the specified range. Devices using (17) spread spectrum(DSSS) communicate by (18) each byte of data into several parts and sending them concurrently on different (19) . DSSS uses a lot of the available (20) , about 22 megahertz(MHz).
A．rate
B．velocity
C．bandwidth
D．period
答案
参考答案：C
解析： 扩频，简单的说，就是通过一定范围内的任意时刻的连续的可用频率将数据用小片传送。使用直接序列扩频技术的设备通过将数据分解成几部分并且以不同的频率发送它们，来进行通信。DSSS使用许多可用带宽，大约是22Mhz。