用英语帮我描述一下世界通讯的发展史

It can be said that mobile radio communication from the date of the invention came into being. In 1897, M.G. Marconi completed by the wireless communications test is a fixed point and a tugboat between, a distance of 18 sea miles.
Modern mobile communications technology began in the 1920s, more or less gone through five stages of development.
The first phase of this century from the age of 20 to 40 years, for the early stage of development. During this period, the first in a number of short-wave band on the development of a dedicated system for mobile communications, the United States on behalf of the Detroit police's use of on-board radio system. The system operates at 2MHz, to the age of 40 to 30 ~ 40MHz that at this stage of modern mobile communications of the initial stage, characterized by a specific system development, low operating frequency.
The second phase from 40 to the mid-60s early. In the meantime, the public mobile communications business began t