Witnessing the first step of 5G network construction: antenna and feeder integration

The coexistence of multiple standards and frequency bands of 2G/3G/4G/5G has resulted in limited space and load-bearing capacity for towers and rooftops. Therefore, the primary challenge facing 5G construction is network transformation while ensuring that network performance does not decline.

In order to reserve space for the 5G active antenna AAU (Active Antenna Unit), the mainstream passive antennas of the existing 2G/3G/4G networks will be replaced with multi-frequency and multi-port antennas as needed, thus forming an "n+1" layout of passive plus active antennas, where n+1 is equal to the number of antennas in the original network, keeping the number of antennas as unchanged as possible and improving deployment feasibility.

Antenna and feeder integration, a must-have for network transformation, is the first step in building a 5G network.

Figure 2. Some typical scenarios of multi-antenna merging when 5G technology is introduced into existing networks

However, antenna and feeder integration affects the entire network. How can we accurately formulate transformation strategies? How can we ensure that the performance of the existing network is not affected after the transformation?

Recently, 5G network planning and optimization engineer Lao Li received a new task...

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Figure 1. Antenna feeder structure: antenna + feeder + jumper + combiner = "antenna feeder system" or "antenna system"

Operator A plans to start deploying 5G in Area B in 2019. Limited by the fact that there is not enough space in the existing network to deploy 5G antennas, it decided to complete the integration of multiple antennas in Area B with the base station equipment manufacturer before April. How to transform and optimize the antennas to ensure that the coverage performance does not decrease compared with the original network is a difficult problem. Lao Li, the project leader on the equipment vendor side, rushed to the airport with a difficult task and officially joined the wave of 5G network construction.

Lao Li first walked around Area B to assess the situation on site. Operator A's 5G field site involved in this project is located in the central area of ​​the city: distributed in financial centers, commercial areas, high-end residential areas, universities and software parks, etc., including several sites such as Band 1*, Band 2, and Band 3. Newly built 5G sites will encounter a series of problems such as multiple frequency bands, limited space, limited load-bearing capacity, and high tower rentals. Based on Lao Li's many years of experience, it is estimated that the sites that need to merge antennas and feeders this time account for nearly half of the total number of antennas and feeders. (*Note: Bands 1, 2, and 3 are used instead of the actual different frequency bands of the existing network)

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Where should 5G be placed when facing space or load-bearing limitations?

Lao Li has done antenna feeder integration in the 4G era and has a lot of experience. However, he knows that the 5G antenna feeder integration is extremely difficult. The antenna feeder integration in the 4G era is mainly the integration of 2G and 3G, involving at most four frequencies and two systems; the antenna feeder integration in the 5G era involves 2G, 3G, and 4G, and 4G is divided into TDD, FDD, and NB, involving seven frequencies and four systems. The coverage performance of multiple frequencies and multiple networks varies greatly, and the dimensions of adjustment influence increase, resulting in a doubling of the difficulty of optimization. At present, it is an industry trend to integrate 2G/3G/4G multi-frequency antennas into one physical antenna. In this way, the adjustment and optimization space becomes smaller, the mutual influence during the adjustment process intensifies, and the degree of freedom of adjustment is greatly reduced.

In order to solve various difficult problems in antenna and feeder integration in the 5G era as soon as possible, Lao Li, a senior network planning and optimization expert, has already prepared his "trump card" - three tricks and six methods for antenna and feeder integration.

The best trick: set a strategy

Decomposition method: current network survey

Existing network survey refers to extracting the existing network antenna and feeder configuration scenarios, and then restoring the antenna and feeder system based on the existing database or typical site antenna survey information, and evaluating the original network antenna surface site by site.

Generally, two 5G antenna feeder deployment plans are determined based on the antenna feeder system evaluation results: if there are space sites on the antenna, 5G antenna feeders can be deployed directly; if there are no space sites on the antenna, the existing antenna feeders need to be merged to free up the poles for 5G deployment. This antenna feeder fusion is implemented for the latter case.

Figure A: Sampling analysis of the antenna space of 100 operators’ sites

Decomposition 2 - Developing a Fusion Strategy

It is of utmost importance to keep the network stable during the modification process. To this end, Lao Li determined the principles of this operation: small impact on the original network, small engineering transformation, good optimization independence, and excellent multi-frequency and multi-system comprehensive performance. It is far from enough to rely on people alone to meet the high-difficulty requirements. If you want to be fast, accurate and good, of course you have to use a tool platform! The network planning and optimization tool platform used by Lao Li this time can quickly combine ten typical merging solutions for the current thirty mainstream scenarios.

Figure 1. Network planning and optimization tool platform output antenna and feeder integration strategy

Lao Li took the solution output by the tool platform and combined it with the actual situation of the existing network to formulate an integration strategy for this project: This antenna and feeder frequency integration transformation mainly involves the multi-frequency and multi-port antennas and feeds of frequency bands 1, 2, and 3. The solution needs to design the RF (Radio Frequency) parameters and optimize the shared antenna and feed for frequency bands 1 and 2 on the basis of ensuring the network performance of frequency band 3, or design the RF parameters and optimize the shared antenna and feed for frequency band 2 on the basis of ensuring the network performance of frequency band 1.

The second step: set parameters

Decomposition Formula 3 – Merger Impact Assessment

Use the network planning and optimization tool platform to merge antennas and feeders based on the antenna and feeder fusion strategy in the previous step. Then, perform a preliminary assessment of the performance impact based on the fusion results, identify sites with significant impact, and revise the fusion plan.

Figure 1. Preliminary evaluation of the impact of antenna and feeder merging performance

Decomposition of the fourth formula - RF parameter design optimization

After completing the antenna and feeder merging and pre-evaluation, it is necessary to perform iterative optimization to match the network coverage target, and finally obtain a set of RF parameters after the antenna and feeder fusion, so as to ensure that the network quality does not decrease after the transformation is implemented. However, parameter adjustment must also have a certain priority. For this project, Lao Li determined the following priority order for construction optimization.

The diagram determines the priority of power downshift and power, and the parameter priority can be flexibly set

Tip 3: Network Optimization

Decomposition of the fifth method - network coverage assessment

For network planning and optimization personnel, the biggest concern is whether the coverage performance of the original network can be achieved after construction. This requires further geographical assessment of network coverage. The network planning and optimization tool platform is used again. Its 15~25m AGPS/MDT MR (Assisted GPS/ Minimization Drive Test Measurement Report) positioning accuracy can accurately present the geographical coverage and traffic distribution, and accurately identify weak coverage areas, interference areas and high-load areas.

Figure 1. Network planning and optimization tool platform for accurate coverage assessment

Decomposition of Formula 6 - RF parameter optimization of co-antenna feed

Based on the data from the network coverage assessment, Lao Li has identified areas with weak coverage, high interference, and high load, and has optimized and adjusted RF parameters through the network planning and optimization tool platform to continue to reduce the impact on the existing network. A total of two rounds of adjustments were implemented, the first round was the optimization of the antenna and feeder transformation sites, and the second round was the optimization of surrounding sites.

Graph Iterative Optimization Algorithm

The effect of the antenna-feeder fusion solution after implementation is very obvious. Not only does the coverage performance of the reconstructed area not decrease compared with the original network, some major indicators remain relatively stable, and some key indicators have been improved. For example, the frequency sweep coverage performance of the antenna-feeder transformation is improved by 3%~5% compared with the original network, the MR coverage rate is increased by 2.88%, and the proportion of CQI (Channel Quality Indicator) less than 7 is improved by 2.13% (20.56% -> 18.43%) compared with the transformation. The task is completed, and Lao Li has submitted a satisfactory answer.

Note: MR (measurement report) is a key indicator of signal coverage commonly used in existing networks.

Figure MR coverage is significantly improved after antenna and feeder fusion

After this battle, Lao Li's new trick - the three tricks and six methods of antenna and feeder integration solution, has begun to show benefits, and is indeed a powerful weapon for operators in the first stage of 5G network construction. Why Lao Li can succeed is that the three tricks and six methods have visible benefits, which can be summarized in nine words: low cost, fast deployment, and good network.

What is cost saving? It rationally utilizes existing network resources and saves investment, thus maintaining a balance between network construction and network maintenance costs; what is fast deployment? It customizes antenna and feeder integration planning and design according to the scenario, one site one solution, improves implementation efficiency, and supports the rapid commercial implementation of the project; what is a good network? It provides accurate planning and design to meet network coverage, capacity and quality requirements, ensuring good network quality after opening. Saving, speed and quality are the unremitting pursuits of operators in network construction, and the unique advantages of this solution allow operators to lay a solid foundation for 5G networks in the early stages of 5G network construction.

Where will the new 5G network be born in the next second? The answer is unknown, because there will be too many. In 2019, 5G pilots have sprung up all over the world. Network planning and optimization experts like Lao Li have also taken their skills to a new level. Their experience and Huawei's three tricks and six methods of antenna and feeder integration in the 5G era will be continuously replicated in multiple 5G network construction sites. The "expert + tool platform" model will effectively help operators successfully take the first step in 5G network construction.