What is the 5G DAS system?
With the development of mobile Internet communication technology and user demand, more and more mobile services are taking place indoors, and as 5G commercialization is approaching, it is especially important to build a high-quality indoor 5G DAS system network.
In the traditional 2G/3G era, mobile communication worked in the low-frequency band, and the traditional indoor distribution DAS (Distributed Antenna System) system was a proven solution for indoor coverage with outdoor macro station signal coverage.
In the 4G era, traditional DAS is still the main means to solve indoor coverage, but with the development of mobile Internet and IoT technology, some business-intensive scenarios (such as transportation hubs, large venues, etc.) start to introduce a new digital room distribution system.
Compared with traditional DAS, the new digital room division system has the advantages of simple deployment, less difficulty in construction coordination, flexible capacity expansion, and visualization of operation and maintenance, which can greatly improve network capacity and enhance network operation and maintenance efficiency.
In the 5G era, because the passive devices and feeders of DAS do not support high-frequency bands, cannot monitor the devices, have high transformation costs, and cannot be expanded on a large scale, they can only be used in certain low-frequency bands and low capacity scenarios (such as tunnels, underground parking lots, elevators, etc.).
The new digital room distribution system is more suitable for a smooth transition to 5G due to simple deployment, operation, and maintenance visualization, support for large-scale MIMO, and other advantages, and will be the main character of the indoor 5G DAS system.
Analysis of the current situation of mobile communication indoor 5G DAS system
At present, domestic operators mainly use traditional DAS to solve indoor coverage problems. Traditional DAS mainly adopts passive devices and has a mature industry chain, with the advantages of small investment, low failure rate, simple and effective system, and multi-system expansion by merging later. However, with the change of mobile services, traditional DAS faces great challenges.
First, engineering construction is difficult and upgrading is difficult.
The traditional room division system requires the deployment of a large number of passive devices, engineering construction is difficult, many nodes, failure potential problems, and coordination with the property is difficult.
LTE room division for dual transformation, new nodes, some areas may have no transformation space, while due to different degrees of device aging, different construction techniques, etc., it is difficult to ensure that LTE dual balance, more unable to support large-scale MIMO.
Second, the difficulty of troubleshooting.
Indoor 5G DAS system installation and maintenance need to be coordinated with the property. The number of traditional room division devices, passive devices cannot be monitored, generally rely on complaints or inspection to find the problem.
For a large room distribution system, it is difficult to inspect every antenna end, especially the hidden room distribution system, it is more difficult to find the problem.
At the same time, due to the number of connection points, building transformation, drawings are not updated in a timely manner, etc., the troubleshooting of fault points often requires more manpower and material resources, which directly increases the cost of network operation and maintenance.
Third, the current devices do not support high-frequency bands.
The highest frequency band supported by the current traditional DAS passive devices is mostly about 2.7GHz, and it is basically impossible to use for 3.5GHz and above.
Due to the shortage of traditional DAS, some manufacturers have launched M-DAS (fiber distribution system), which is conducive to the visualization of operation and maintenance, but the fiber distribution system still needs to connect RRU as the source, and the nature of its repeater relay remains unchanged, which is not conducive to expansion and smooth evolution of the system.
The introduction and development of a new distributed room 5G DAS system
In response to the huge bottlenecks faced by traditional DAS and M-DAS, various manufacturers have launched new digital indoor distribution systems, such as Huawei’s Campsite, ZTE’s QCELL, Ericsson’s Radio DOT, Nokia’s FlexiZone, etc.
Compared with traditional DAS, the new digital indoor distribution system has the advantages of simple engineering implementation, visualized operation and multi-channel MIMO, easy expansion and evolution, etc. Major operators have deployed in large and medium-sized scenarios. It is proved that the traffic per unit area of LTE’s new digital indoor distribution is 4~10 times of traditional DAS.
With the high-speed development of mobile Internet, more and more new mobile services such as HD video, indoor positioning, AR/VR, etc. have put forward rigid requirements on the network such as large bandwidth, high capacity, and low latency.
This requires that the room system should have the characteristics of simple construction, easy coordination, smooth upgrade, operation, and maintenance visibility, and intelligent network management. In this regard, the new digital room system has obvious advantages.
First, the project implementation is simple and can be smoothly upgraded.
5G era mainly uses 3.5GHz, 4.9GHz, and another high-frequency band, affected by this, the number of room division system end will be a massive increase, which requires 5G room division equipment should be small, lightweight, simple installation, rapid deployment.
The new digital room division adopts a simple three-level architecture, base station side (similar to BBU), Hub, and remote RF transmitting unit, with fewer connection points, reducing the potential for failure.
The network cable and optical fiber replace the traditional coaxial cable, the network cable as a transmission medium at the same time also for the remote RF unit for power supply, the network cable quality is light, construction and deployment is easier, measured by the construction period than the traditional DAS shortened to 1/5 ~ 1/3. also reduce the visual impact, easier to communicate with the property.
At present, major operators have deployed new digital room division on a large scale in some large and medium-sized indoor scenes (such as transportation hubs, shopping malls, hospitals, etc.), and the system is running well, and the user experience rate has increased significantly.
At the same time, in consideration of minimizing operators’ repeated investment, 6A network lines are pre-built when deploying the new 4G digital room division, and 5G NR is quickly overlaid to ensure implementability while minimizing secondary entry costs.
Secondly, visualization of operation and maintenance, system maintenance, and troubleshooting is simple.
5G era, dense network networking has become the norm, and the number of ends RF transmitting units will increase significantly, so real-time monitoring of network equipment and end transmitting units is one of the basic functions of the network, and try to do not go to the site for non-hardware reasons.
The new digital room system basically adopts active devices, which can monitor the working status of all devices in real-time, quickly locate fault points, and realize the visualization of operation and maintenance.
At the same time, the new digital room system can also automatically realize self-diagnosis, self-optimization, and self-healing according to the surrounding channel situation and user density, minimizing manual intervention and effectively reducing maintenance costs.
Thirdly, it is convenient to upgrade and transform.
The new digital room system mainly adopts optical fiber and network cable to transmit digital signals and supports a high-frequency band, which is conducive to a smooth transition to 5G.
Massive MIMO is one of the key technologies of the 5G network, and the future 5G room system should support at least 4˟4 MIMO.
In summary, the new digital room distribution system is simple to deploy, operation and maintenance visibility, management intelligence, easy maintenance, can follow the standard, support 4G, 4.5G, 5G all stages of service, capacity, user experience, and other needs, can smoothly evolve, the maximum degree of protection of the operator’s investment, will be the main solution for indoor distribution system in the 5G era.
Traditional DAS will still occupy a place, mainly used in special scenarios (such as elevators, underground parking lots, tunnels, etc.) where capacity requirements are not high and coverage problems are solved.
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