LTE Goes Green with Technical Innovation

Power consumption is one of the main expenses of running an LTE network, and energy-efficient network elements have become more and more important.

An LTE wireless network contains two main elements: RRUs and BBUs. With the development of hardware architecture, power consumption in network elements has decreased significantly. Digital predistortion and Doherty technologies have also decreased RRU power consumption lower than ever. In each RRU, the power consumed by a fan can be saved by using natural heat dissipation. With the development of advanced IC technology, high-density circuits can be integrated into an IC to greatly reduce the power consumption and size of the IC. This lowers the overall power consumption in a BBU. Advanced architecture, high-efficiency power amplification, and natural heat dissipation have greatly reduced equipment power consumption and operational cost without impacting normal network operation.

Although energy can be saved  through innovative architecture, hardware, and materials, new energy-saving techniques are yet to be tapped. By studying people's usage habits, researchers have found a new aspect to energy saving.

The NGMN Alliance has measured the daily average traffic distribution for an urban scenario (Fig. 1). In Fig. 1, there is no communication activity in the cell in the two hours between approximately 04:00 and 06:00, and traffic is lower than 20 percent in the seven hours between approximately 0:00 and 07:00.

Subscribers use more communication services during the day and very few in the small hours of the morning. Knowing such usage habits is useful to determine how resources should be allocated so that the maximum amount of power can be saved.

●    Dynamic PA voltage adjustment

If the RF power amplifier (PA) works at full power when there is no traffic or the load is very low, then power is wasted.

PA voltage can be dynamically adjusted according to the traffic load and required output power. When the output power is relatively low, the voltage required by a power amplifier is set lower than its maximum output voltage. In this way, power amplification is improved when the traffic load is light, and power consumption is reduced.

●    Intelligent OFDM symbol turn-off

When there is no traffic, power can be saved by adjusting the PA voltage. Power can also be saved in transmitting LTE OFDM subcarriers. OFDM symbols can be automatically turned off when there is no baseband data transmission. This reduces power in the PA. Turning off PA OFDM symbols is more efficient than keeping them turned on all the time, especially when there is light or no traffic. PAs, cells, and power supply can also be intelligently turned off in the same way as OFDM symbols.

●    SON energy management

In an LTE system, energy-saving technologies are managed by an SON server regardless of whether they are used individually or together.

All energy-saving functions are controlled by the SON server and can be automatically configured by the operator. The SON server is the central platform where energy is managed according to the operator’s strategies.

ZTE’s green LTE network solution reduces power consumption in base stations in several ways. A base station can save up to 40% of power usually consumed. The combination of dynamic PA voltage adjustment and intelligent turning off of OFDM symbols is unique in the industry and can save about 32% of power consumption. Suppose the average power consumed by each base station is 1500 W (configured with three sectors). A single station can save up to 5200 kWh each year. This means more than 5.2 million kWh can be saved for a network with 1000 base stations each year, which is a saving of 1730 tons of standard coal and a reduction of 4500 tons of carbon dioxide a year. If base station power consumption is reduced, then less auxiliary power and heat-dissipation devices are required and less network OAM is necessary. The power needed for these devices is also reduced. New energy sources such as solar, wind, and bioenergy can be used in conjunction with these innovative energy-saving technologies. In this way, network energy consumption can be cut by 50%.

ZTE has increased its contributions to LTE and future technologies and has secured a leading position in the LTE industry. The company is dedicated to providing customers with green, energy-saving products and solutions. ZTE aims for harmonious coexistence between networks and the environment.