The difficulty is primarily due to the lack of line of site between base stations, or towers, and the subscriber.

困难主要是在基站（或者发射塔）与用户之间缺乏直达线路。

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A wireless communications network (100) includes various base stations (100) and subscriber-stations (114).

一无线通信网络(100)包括多个基站(100)和订户站(114)。

youdao

While political ad spending, the Superbowl and ad pricing growth lifted the results for CBS-owned TV stations and CBS Radio, cable networks benefited from continued subscriber growth and higher subscription pricing.

FORBES: CBS's Ad Growth And Better Margins Lift Outlook

Instead of trying to maintain a constant stream of communications with a subscriber, the satellites simply receive short messages and zap them down to one of their ground stations on earth.

FORBES: Iridium for truck trailers