Power-Following Solution for Seamless User Experience

The 5G network has entered a phase of refined construction and operation, focusing on enhancing service quality and network efficiency. 5G network devices offer large bandwidth and high power, and in a user-centric network, inter-device coordination allows for efficient power sharing and distribution, ensuring an optimal user experience.

High-speed railway coverage is a high-value scenario for 5G network coverage. As high-speed trains become a symbol for China, telecom operators are committed to providing a high-quality service experience for passengers. ZTE is actively engaged in the construction of high-speed railway network coverage, continuously innovating in network construction practices.

The 5G network for high-speed railway must track users travelling at speeds up to 350 km/h in real-time, providing a continuous service experience. ZTE has introduced the RRU power-following solution to build an efficient high-speed railway communication network.

Innovative RRU Power-Sharing Design

In conventional RRU design, all RRU channels have independent power amplifiers and output channels, and the power cannot be shared between different RRU channels.

However, if the power from idle RRU channels could be shared with other channels, inter-channel power and carrier configurations could be performed more efficiently, and the maximum effective downlink transmit power of some channels can be increased to improve cell coverage.

With the innovative concept of internal power sharing in RRUs, ZTE breaks through the restriction of power sharing between common RRU channels through a new RRU hardware design, enabling greater flexibility in the use of RRU power.

In this design, two RRU channels are grouped, and coupling bridges are added between channels. Through system software control, the power of the two RRU channels can be converged or output through either channel.

Take an eight-channel RRU as an example. A conventional eight-channel RRU has a total power of 400W, with each channel supporting a maximum power output of 50W. In the hardware design for RRU internal power sharing, the maximum output power per channel is increased to 100W. Power can be converged into four channels, doubling the downlink transmit power to 4 × 100W. Through system design, two eight-channel RRUs can be configured to form a dual-sector network with a dynamic output of up to 8 × 100W.

RRU Power Sharing for High-Speed Railway Scenarios

The high-speed railway 5G network typically adopts a single-site, two-RRU sector networking mode. Given the linear movement of trains, only some RRUs provide coverage for high-speed trains within a certain period of time.

Based on the operational characteristics of high-speed trains, the power from RRUs with few or no users can be shared with the RRU covering high-speed trains at the same site. In high-speed railway line coverage, multiple RRU cells are combined, and power coordination between RRUs needs to be implemented in a large logical cell.

As the high-speed railway moves linearly, the two co-sited RRUs can dynamically adjust power allocation based on the UE’s position to implement power sharing and convergence across different coverage directions, enhancing downlink performance for high-speed train users.

ZTE has innovatively proposed the RRU power-sharing solution that utilizes the RRU internal power-sharing design (as shown in Fig. 1). In accordance with the UE’s position in the train’s incoming direction, the algorithm and hardware work in real-time precise coordination to ensure that the focus of the RRU’s transmit power follows the service direction, doubling the transmit power of a single-side antenna and meeting the 350 km/h high-speed movement requirement.

The ZTE RRU power-sharing solution ensures more reasonable energy utilization. Through real-time UE location identification and base station software control, UE-level and subframe-level RRU power sharing adjustments are implemented to maximize device energy efficiency.

Test results from the commercial high-speed railway network show that ZTE’s RRU power-sharing solution can achieve a coverage gain of 3 dB and increase the downlink user-perceived rate by 10% to 20%.

The ZTE high-speed railway RRU power-sharing solution uses the RRU internal power-sharing design, decouples from the antenna system, and can be connected to the conventional smart antennas of different antenna manufacturers, making network deployment easier for operators. Different types of antennas can be selected for different sites.

RRU Power Sharing for Multiple Scenarios

In traditional cellular networking solutions, the RRU for each sector is configured independently. While power can be shared between RRU carriers, RRU power cannot be shared between different sectors.

In a typical three-sector network, the service duration and load of each sector differ, creating opportunities for power sharing between sectors. When there is remaining RRU power in a low-load sector, it can be shared by a high-load sector. This increases the downlink transmit power and spectrum efficiency of the high-load sector, improving user experience and enhancing the downlink capacity of the cell.

In scenarios such as residential area coverage, subway coverage, and low-cost coverage, four-channel devices are commonly used. In these cases, it is possible to either use only some channels of the power-sharing RRU or split the eight-channel RRU into two 4TR cells. When only four RRU channels are used, the power from the four idle channels can be converged into the four working channels, doubling the power of the four transmit channels and improving the coverage and spectrum efficiency. In scenarios where an eight-channel RRU is split into two 4TR cells, the RRU power can be shared between the two groups of four channels based on the load and coverage of the two 4TR cells.

The ZTE power-following solution adopts an RRU internal power-sharing design, and has implemented innovative practices in both RF and base station software and hardware. Embracing the green network concept and expanding product compatibility, ZTE has made valuable explorations in improving overall network performance in the future.