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Dense networks for energy-efficient 5G networks

Over the next decade, mobile traffic is expected to grow by a factor of 1 000, but this revolution should not come with an equivalent increase in energy consumption if we want to avoid causing any adverse effects on the environment. An EU-funded project investigated how to simultaneously increase network throughput and energy efficiency by deploying small cells and large-scale antenna systems.
Dense networks for energy-efficient 5G networks
The major challenge facing the next generation of wireless communication systems (5G) is to provide high data rate access to multiple mobile users while ensuring end-to-end quality of service. Although 5G promises to deliver higher speeds and ubiquitous connectivity, it inevitably presents a number of challenges: energy consumption and carbon dioxide emissions are sharply increasing as customers increase their digital usage.

Small-cell access points and massive multiple antenna (MIMO) technology are two promising routes to achieving dense deployments of links and promise huge improvements in throughput and energy efficiency. Within the project DENSE4GREEN (Dense deployments for green networks), scientists used advanced mathematical tools and developed new models to simulate the performance of such dense networks and evaluate robustness to interference.

First, scientists derived a new model of the total power consumption of small-cell and MIMO networks, including all analogue and digital components. This model then served to maximise the network energy efficiency as a function of the density of base stations, transmission power, the number of base station antennas and users per cell, and the pilot reuse factor for channel acquisition. Results showed that small cells can undoubtedly boost energy efficiency – however, electronic circuit power should not exceed cell transmission power. The addition of extra antennas in MIMO led to further improvements in energy efficiency.

The DENSE4GREEN team developed new linear algorithms that make it possible to minimise the total network power consumption, considering different degrees of base station cooperation: no cooperation at all or full cooperation, and exchange of channel state information. Base station cooperation was further classified on whether base band processing is performed locally at individual base stations or at a single central unit (centralised and decentralised processing).

Another focus was to investigate the impact of user mobility on the network power consumption. Scientists studied the power consumption of a heterogeneous network in which a dense tier of small-cell access points overlays a massive MIMO macro tier, using a wireless backhaul for traffic. Results demonstrated that when user mobility reaches a critical value, the power of all transmitters rapidly increases.

The DENSE4GREEN team developed also a framework to understand how a cellular network designed for maximal energy efficiency should look like. The analysis shows that reducing the cell size is undoubtable the way towards high energy efficiency, but the positive effect of increasing the base station density saturates when the circuit power dominates over the transmission power. A further leap in energy efficiency can typically be achieved by adding extra base station antennas to multiplex several users per cell showing that dense deployment of small cells and massive MIMO can significantly boost network capacity, ensuring that network energy consumption will not be proportional to the volume of the handled traffic.

Related information


Dense networks, 5G, small cells, energy efficiency, DENSE4GREEN, massive MIMO
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