3D coverage pattern in 5G TDD: What you need to know to be an expert

3D coverage pattern in 5G TDD is one of the most important features for any RF engineer looking to optimize coverage and quality of a 5G-NR cluster.

The New Radio (NR) system uses the beamforming technology to allow all types of channels and signals to use narrow beams with higher density and better directivity.

In LTE, a unique wide beam is used. A narrow beam provides limited coverage and is unable to cover all UEs in a cell.

For this reason, vendor providers incorporate beam management in 5G to enable the gNodeB to separately manage beams for each type of channel and signal based on their respective characteristics, and select the best beams for UEs. This enhances performance in coverage as well as user experience.

3D coverage pattern comparison 4G and 5G

As you may know, 5G deployments deploys in low bands and high bands (mmWave). In this post we will focus our analysis on TDD low bands.

Following list shows the two types of beams divided based on the weight policy used for beamforming

  • Static beams: Use predefined weights for beamforming to ensure that characteristics, such as quantity, widths and directions are fixed. The best beam set is then selected for each type of channel and signal according to information such as cell coverage, UE distribution, and system load.
  • Dynamic beams: Use weights calculated based on channel quality for beamforming to adapt widths and directions to factors such as UE positions and channel status.

Understand Beam classification for 3D coverage pattern

  • Static beam
    • Broadcast beam: Used by physical broadcast channel (PBCH) and synchronization signal (SS).
    • Control beam: Used by physical uplink control channel (PUCCH), physical downlink control channel (PDCCH), channel state information-reference signal (CSI-RS), and tracking reference signal (TRS).
  • Dynamic beam: Used by physical uplink shared channel (PUSCH) and physical downlink shared channel (PDSCH).

3D Coverage Pattern in 5G TDD

3D coverage pattern applies only to broadcast channels. This feature enables gNodeB to support beams for multiple coverage scenarios, to extend coverage area of broadcast channels and synchronization signals in different networking scenarios. This will better match the cell coverage scope and UE distribution.

Mobile operators can select the beam configuration best suited to their own coverage requirements. Allowing them to resolve issues such as limited cell coverage and neighboring cell interference (Goodbye antenna twist to improve coverage for tall buildings 😀)

This means that RF engineers can modify the radiation pattern of the broadcast channel through parameter configuration in the gNodeB. Some of the most common scenarios available are:

Horizontal 3 dB BeamwidthVertical 3 dB Beamwidth

Radiation pattern configurations may vary by vendor and RF module.

Let’s review a basic example on how to determine the best setting based on physical conditions and requirements.

In following example, we have 2 buildings next to each other, together they have a width of 30m. The maximum height is 70m. Operator plans to install a 5G gNodeB 70m from the buildings. The height of the AAU will be 20m.

  1. Calculate the horizontal 3 dB beamwidth

If B is 30 m and D is 70 m, α is 24°, as show below, then the horizontal could be 25°.

2. Calculate the vertical 3 dB beamwidth

If D is 70 m, h is 20 m, and H is 30 m, β is 23°, as show below, then the vertical beam could be between 25° to 110°.

3. Based on the intersection of scenario choices, we can conclude that the best configuration would be (25°, 25°).

Beam tilt and azimuth

In addition to radiation pattern changes, the Active Antenna Unit (AAU) also provides capabilities to adjust tilt and azimuth. Depending on the type of antenna (8T, 16T, 32T, 64T etc.) engineers can adjust those parameters to modify coverage radius and coverage shape of the cell.

These operations run remotely through parameter adjustments on the gNodeB. This can reduce difficulty in site selection planning and site optimization, decrease the optimization and manpower coordination costs, and better address inter-cell interference issues. The gNodeB supports the tilt or azimuth adjustment of broadcast beams in the unit of 1°.

Depending on the equipment, some of the most common ranges of configurations are:

Tilt adjustment RangeAzimuth adjustment range
-2° to 15°-47° to 47°

Considerations to implement 3D coverage pattern optimization

Before activating this feature, record the RSRP value in the default configuration, then observe the RSRP changes in the same position but in different coverage scenarios before and after the modification to check the coverage performance

Some interesting links for RF optimization:

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