学了多年通信，但很多概念其实是有混淆的，记录一点，没事重温一下，概念用英文写，算练手吧。。。
1、关于带宽
Bandwidth in signal processing [1]: the difference between the upper and lower frequencies in a continuous set of frequencies. Depend on the lower frequency, there are baseband bandwidth (the lower frequency is 0) and passband bandwith (the lower frequency is not 0). It is typically measured in Hertz (HZ).
Bandwidth in computing [2]: the bit-rate of available or consumed data communication resources expresed in bits per second.
There is a relationship between bandwidth in signal processing and that in computing. According to Hartley's law, the digital data rate limit (or channel capacity) of a physical communication link is proportional to its bandwidth in HZ[2].
[1] wikipedia, http://en.wikipedia.org/wiki/Bandwidth_(signal_processing)
[2] wikipedia, http://en.wikipedia.org/wiki/Bandwidth_(computing)
