An Energy Efficient Radio Base Station

Abstract

The mobile telecommunication network is growing year after year and it will soon move into the high speed 5G and Internet of Things technology. These new technologies will improve the throughput and data connectivity and due to that the energy consumption in radio and digital units may increase in a Radio Base Station (RBS). There are more than 500 000 off-grid RBSs in the world which are powered by diesel generators. This results in air pollution, green house gas emission and high fuel and maintenance costs for the operators. The main objective of this thesis is to find ways to bring down the energy consumption in radio and digital units and check the viability of a solar powered site instead of a diesel powered site. This has been done for an LTE network. The current power save features developed by Ericsson has been studied and two new power save features have been implemented. The first is an innovative algorithm that optimizes the
cooling in the baseband to obtain a minimal power consumption, this method was proved to work even in scenarios with large variations in ambient temperature. An Eco-mode algorithm was tried on few radio units, where the biasing of the power amplifiers was reduced in low load scenarios. This reduced the power consumption of each radio unit with up to 3.4% in the test cases described in the thesis. Finally,the design and economic analysis of a solar powered radio base station was performed, in order to recommend an energy efficient, sustainable and cost-effective option to mobile operators that would relieve the stress of regular maintenance
and increased expenses. It showed that a combination of solar panels and diesel generator is the most economical and environment friendly solution.

Popular Abstract

Towards Energy Efficient Mobile Networks
With the emergence of new mobile technologies and growing network, the necessity for energy efficient mobile networks becomes more and more significant.Energy efficient radio and digital units powered by environment friendly solar energy will be a better alternative to the current diesel generator powered base stations. As part of the thesis we have learned and worked with the hardware and software parts of the radio and baseband units. In order to come up with novel and innovative ideas to improve energy efficiency of radio and baseband units, a study of already available power save methods was done. There are different kinds of power save methods, some are pure optimizations where the base station uses less power without affecting the performance while others will intentionally reduce the performance in scenarios when and where maximum performance is not required. In the thesis there is one power save method of each kind, one that optimizes the use of cooling equipment in the baseband and one that reduces the power consumption in the radio at low load.

The baseband is the part of the radio base station that handles the logic and processing of the data. It contains electronic and electrical components within it and will therefore require a cooling equipment to protect it from overheating. For the baseband that was used in the thesis the cooling is performed by a fan connected to one side of the unit. The fan reads out the values from certain temperature sensors and will increase the fan speed if there is a risk of overheating. But another issue with high temperature is that it will increase the power consumption of the baseband due to thermal leakage. In order to decrease the temperature and
thus the power consumption, the fan speed can be increased. This will however result in a higher power consumption for the fan itself. It was seen that one can find a fan speed for each scenario where the total power consumption is at its lowest. An innovative algorithm was implemented that continuously adjusts the fan speed in order to minimize the total power consumption.

The radio unit uses a bandwidth which allows it to transmit data at different frequencies. There is a power amplifier that can amplify the signal at all the available frequencies. In a lot of cases this is unnecessary since the load is much lower than the maximum throughput of the base station. A power save feature named ECO-mode was implemented that will reduce the biasing of the power amplifier. This limits the available throughput and it was used to save power in scenarios where the maximum throughput is not needed. An algorithm was developed that can turn on or off this mode depending on the load.

Installation of an off grid base station powered with a diesel generator is not only a costly affair but also an environment concern in that area. This problem can be reduced by using renewable energy sources that are pollution free and has lower costs in the long run. The steps to design a solar powered base station has been explained and analyzed in the thesis. A cost analysis was done with the three different power options; a fully solar, fully diesel and a combination of both to find the best alternative among them. The combined option was found to be most cost-effective among them. The optimal portion of each power source would give the lowest cost and this is individual to each location and power requirement of the site.

• author: Prasad, Lakshmi
• supervisor: Johan Wernehag; Jonas Bengtsson; Joakim Persson; Ulf Morland
• organization: Department of Electrical and Information Technology
• course: EITM02 20181
• year: 2018
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• report number: LU/LTH-EIT 2018-663
• language: English
• id: 8957108
• date added to LUP: 2018-08-29 17:34:29
• date last changed: 2018-09-06 10:57:14