Traditional in‑depth coverage solutions: BBU+RRU or digital optical fiber repeater.

Challenges of in‑depth coverage Due to different transmission losses across frequency bands, traditional coverage solutions struggle to achieve dual‑network balance. Meanwhile, it is difficult to properly coordinate the capacity and coverage radius of FDD‑LTE networks.

Passive components are widely deployed in traditional indoor distributed systems. Such components are prone to aging, which may lead to degraded network coverage performance and blind zones.

Difficulties in project deployment High dependency on signal sources. However, lead‑time for main equipment procurement is long with low flexibility. The whole process of traditional indoor distributed systems, from design to construction, reconstruction and delivery, takes a long cycle, without support for subsequent capacity expansion and evolution.

Multiple management pain points A large number of passive components are adopted in traditional indoor distributed networks. Without centralized network management, network faults cannot be detected in a timely manner. Indoor coverage and outdoor in‑depth coverage are isolated, bringing obstacles to collaborative fault management.

Traditional coverage solutions can hardly meet requirements in the LTE era. Accordingly, the digital optical fiber distributed system (DAS) emerges as the times require.

The DAS system consists of three parts: master unit (signal source access), expansion unit and remote unit. The detailed specifications are shown as follows: