The most comprehensive ever! Antenna solutions for various 5G scenarios (Part 2)

石榴姐

The most comprehensive ever! Antenna solutions for various 5G scenarios (Part 2) [Copy link]

Indoor 5G antenna solution

2.1 Typical digital indoor distribution system

Typical indoor distribution scenarios include government and enterprise office buildings, shopping malls, hotels, hospitals, etc. Generally, there are many internal partitions in buildings, and the obstruction is large. The deep coverage demand is mainly solved by the antenna distribution system. The traditional indoor distribution system (DAS) is difficult to meet the requirements of high frequency above 3.5 GHz and Massive MIMO in the 5G era. The shortcomings in engineering implementation, fault detection difficulty and single business continue to be prominent. Compared with the traditional DAS solution, the digital indoor distribution solution will gradually become the mainstream.

Traditional passive antenna distribution systems are difficult to implement MIMO, so new digital indoor distribution systems that integrate traditional RRU+antennas will be widely used in the 5G era. Indoor coverage requires low antenna power, small antenna size, small coverage distance, uniform signal distribution, and flexible capacity adjustment. Digital indoor distribution systems can better meet the needs of 5G indoor coverage, but digital indoor distribution system antennas are still mainly omnidirectional antennas to achieve full coverage of a certain space, so the beamforming characteristics will be lost, and the size and power consumption are also limited. The number of antenna channels can only reach 4 to 6 TRs.

Taking Huawei's 5G digital indoor distribution as an example, its composition diagram is shown in Figure 10

Figure 10 Schematic diagram of digital room division

RHUB is the RF remote CPRI data aggregation unit, and its main functions include:

RHUB is used together with BBU, DCU and pRRU to support indoor coverage.

Receive downlink data sent by BBU/DCU and forward it to each pRRU, and forward uplink data of multiple pRRUs to BBU/DCU.

Built-in DC power supply circuit to supply power to pRRU.

d. Supports pRRU networking via optical fiber links.

pRRU is a radio remote unit that implements radio frequency signal processing. Its main functions include:

The baseband signal is modulated to the transmission frequency band, filtered and amplified, and then transmitted through the antenna.

The RF signal is received from the antenna, filtered and amplified, down-converted, converted into a digital signal and sent to the BBU for processing.

Transmit CPRI data via optical fiber/network cable.

Supports built-in antenna (4T4R).

Supports power supply via PoE/DC.

Supports flexible configuration of multi-frequency and multi-mode.

2.2 Three-dimensional square wave shaped antenna for large venues

As a special indoor coverage, large venues have the characteristics of large space, dense personnel, concentrated users, and huge business demand. In order to ensure the capacity requirements in the venue, the traditional solution of using wall-mounted plate antennas + cell splitting is used to solve the coverage, but cell splitting will cause serious interference to neighboring cells in the same frequency network, affecting user experience. Drawing on the idea of shaped antennas in macro base station scenarios, special shaped antennas can be used for indoor coverage of large venues to control the radiation range of the beam to achieve precise coverage and partition cutting effects.

The three-dimensional square wave shaped antenna has excellent beam convergence and sidelobe suppression capabilities, which makes the signal decay rapidly outside the coverage area, with clear boundaries, and effectively avoids cross-area interference and weak coverage.

Table 1 Comparison of beam gain and beam width between 3D square wave shaped antenna and other antennas

The beam width of the three-dimensional square wave forming antenna is reasonably narrowed, which is more conducive to multi-cell segmentation in dense scenarios and achieves capacity improvement. Based on the fact that the signal source power is large enough, the antenna coverage range is calculated based on the antenna beam width and trigonometric functions.

Table 2 Comparison of coverage of 3D square wave shaped antenna and other antennas

5G Antenna Solution for High-speed Railway Scenarios

3.1 Traditional 33° and 65° high gain antennas

Compared with traditional high-speed rail signal coverage, 5G high-speed rail coverage faces greater challenges. On the one hand, 5G special services require higher network performance. On the other hand, the higher frequency of 5G and the faster speed of high-speed rail will bring more serious signal attenuation and distortion, affecting user experience. Traditional line coverage uses 33° horizontal narrow beam antennas or 65° horizontal wide beam high gain antennas, which are prone to black spots under the tower and zero coverage in the horizontal direction.

3.2 5G 8TR Beamforming Antenna

5G high-speed rail antennas can consider beamforming, and 5G technology supports beam time-division scanning. Beam time-division scanning can effectively improve the coverage range, that is, increase the equivalent beam width. Based on the principle of beam time-division scanning, beam shaping can be performed in the horizontal and vertical directions for high-speed rail application scenarios to make up for the coverage gaps caused by zero sinking and the problem of darkness under the tower.

The 5G high-speed rail shaped antenna consists of 4 columns of antenna elements, with 8 channels in the horizontal direction, which can achieve a scanning range of ±30°. Due to the increase in the number of antenna elements, the antenna gain has a 3 dB gain compared to the F band. With the MIMO function, it can compensate for the impact of the large attenuation of the D band signal.

According to the three-dimensional model, the gain values corresponding to the synthetic beam of the horizontal 8-channel antenna at different distances on the high-speed railway line are obtained. Compared with the traditional 33° antenna, the horizontal zero point is filled and the coverage effect is significantly improved.

Figure 11 Comparison of gain values between the horizontal 8TR time-division coverage solution and the traditional high-speed rail antenna at different distances from the high-speed rail line