Indoor applications are the main battlefield of 5G services. It is predicted that about 85% of business traffic in the 5G era will occur in indoor scenarios. The quality of indoor coverage is directly related to the experience of 5G indoor applications. Today we will talk about indoor coverage in the 5G era. building.
Let's start with the simplest, such as covering a simple residential building. Some friends thought so and deployed a base station in the house. Is it possible? Of course it works, but... it's too expensive!
So is there a way to save money?
Can an outdoor base station be used to cover the house? This method is more cost-effective and can meet the needs of users.
In this way, the outdoor base station covers the room. As the name implies, the outdoor base station is used to take into account the indoor coverage. In the early stage of 5G network construction, this solution was favored by operators due to its fast network construction and low investment cost.
Is it possible to directly use this method for indoor coverage of high-rise buildings?
The passive antenna of the 4G macro station has only one beam, the horizontal lobe is very wide, and the vertical lobe is relatively narrow. The horizontal coverage is satisfied by the down-tilt angle, resulting in poor signal in high-rise buildings and unable to meet the requirements of high-rise building coverage.
5G introduces Massive MIMO technology, and macro stations have beamforming capabilities. Since operators generally use a horizontal 7/8 beam configuration, although the horizontal coverage is optimal, the vertical coverage is limited and cannot meet the coverage requirements of high-rise buildings. In addition, the complex wall structure of high-rise buildings will weaken the outdoor base station signal. In the 5G era, there are higher requirements for capacity, delay, and reliability, and the indoor solution for outdoor base station coverage will be incapable of meeting high-rise buildings.
Witty friends may think that since the signal is weakened by the wall, then we will introduce the signal, and the problem will be solved.
How to get it? We know that wireless signals are sent and received by antennas. If we deploy antennas indoors, the signals will not come in.
This is actually the idea of DAS (Distributed Antenna System). Passive devices such as couplers, power dividers, and combiners are used to split and transmit the RF signals of the RRU, and the signals are distributed as evenly as possible to on each antenna, so as to achieve uniform distribution and coverage of indoor signals.
In fact, the DAS method has been widely used in 2G/3G, and the technology has a high degree of maturity. However, in the 5G era, facing the large-capacity demand of 5G, it seems a little stretched. Some friends may disagree and think that increasing the capacity is not a matter of adding more antennas? The original antenna could not be satisfied, and now adding another antenna will solve the problem?
The idea is beautiful, but the reality is cruel! The actual construction cost of this kind of transformation is relatively high and the difficulty is relatively large.
So is there a way to improve the network capacity without changing or changing the existing DAS system? We want the horse to run and not to graze! However, there is really such a transformation idea, which is what ZTE launched. The multi-channel joint transceiver scheme.
This kind of thinking does not come out of thin air. Let's take an example from work.
If the size of the computer monitor in the office is relatively small, and there is no budget for purchasing a large-screen monitor for a while, then some small partners will use two monitors to form a dual-screen office, which greatly improves the office efficiency.
Similar to this, the multi-channel joint transceiver scheme utilizes different channels of one or more RRUs to combine multiple transceiver nodes of the DAS distributed system to build a multi-dimensional multi-antenna transceiver system to achieve more upstream/downstream MIMO. transmission to increase system capacity.
To put it simply, the previous antennas were used to send and receive data to users independently, but now several antennas are combined to send and receive data to users.
This multi-channel joint transceiver solution does not need to change the network architecture of the traditional DAS system, and avoids the problems of heavy workload, high cost, and difficulty in coordinating site resources for the DAS system. Only through the deployment of the software version, the performance of the traditional DAS network can be quickly realized. It can be upgraded and compatible with existing 5G terminals without any restrictions on terminals.
Can the DAS system perfectly solve all 5G indoor coverage problems with the support of the multi-channel joint transceiver solution?
In fact, there is still a difficulty. The passive components of the 4G DAS network can only support the sub 3G frequency band, and are helpless in the face of 5G high-frequency networks (sub 6G, etc.).
So is there any other way to improve indoor coverage?
Dedicated deployment of base stations for small buildings obviously has low input and output, but in some large-scale scenarios such as transportation hubs, stadiums, skyscrapers, etc., the balance of input and output is tilted. We can go back to the previous ideas and consider deploying indoor base stations for these large-scale scenarios, which is the active digital indoor distribution solution.
The active digital room adopts a three-level architecture of baseband unit (BBU) - convergence unit (PBridge) - radio frequency unit (Pico RRU). The difference from the outdoor macro station is that there are more aggregation units, and the RRU becomes a Pico RRU. Pico RRU is smaller in size, more convenient to deploy, large in capacity, and flexible in configuration. Therefore, the active room sub-scheme has become the first choice for high-value areas with large capacity and excellent experience.
The active digital room distribution solution has been widely used in the 4G era. In order to make a big difference in the 5G era, the active digital room distribution solution faces three major problems that need to be solved.
Cost is one of the important factors to consider in indoor coverage construction. If the cost of an indoor coverage solution is too high, operators will be discouraged.
Pico RRU is the main cost component of active digital room distribution. The more frequency bands and channels of Pico RRU, the higher the cost. Therefore, the key to reducing the cost is to reduce the cost of the Pico RRU in the network. Considering that the capacity requirements of different indoor coverage scenarios vary greatly, resulting in large differences in the frequency band and channel requirements of Pico RRU, if a single product configuration is used, it is obviously unable to meet the needs of indoor coverage. Products and solutions to achieve the most accurate investment.
In addition, another idea is to build and share. Multiple operators share the room distribution system, which can not only share the cost of 5G network construction, reduce resource waste, but also increase spectrum bandwidth and improve user experience.
Due to the characteristics of high integration, high transmit power and large number of Pico RRU, the active digital room sub-scheme faces the test of operation and maintenance and equipment energy consumption management. In the 5G era, active digital room distribution solves this problem through visual management and intelligent energy saving.
Visual management is to visually display the deployment location information of Pico RRU by floor by generating a building model, and at the same time generate performance data with Pico RRU unit as the granularity, and give targeted network optimization suggestions.
Intelligent energy saving is to use AI and big data technology to maximize the energy saving effect and achieve the best balance between energy consumption and performance on the basis of ensuring network KPIs. Expand new business
Operators hope that the active digital room distribution system can tap the network potential, open network capabilities, and expand new services. What are the countermeasures for this active digital room distribution system? This requires the combination of MEC mobile edge computing capabilities, which can further optimize service experience, enable value-added services, open network capabilities, and provide customized services.
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