Upgrading from Global System for Mobile Communications (GSM) to Universal Mobile Telecommunications System (UMTS) and then to Long Term Evolution (LTE) is easy thanks to the following factors:
A BBU3900 is equipped with different boards, among which some work in one mode and the others work in another mode. The BBU3900 can process services for both of these modes. With two BBUs, the triple-mode application can be achieved.
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