What Technologies Are Making In-Building Wireless Systems Greener?

In-building wireless like a Distributed Antenna System (DAS), a Distributed Radio System (DRS), small cells, and repeaters are designed to improve network coverage, network capacity, or both. With 2G/3G/4G, outside-in coverage is typically adequate on a low band; however, outside-in typically does not provide adequate indoor coverage in mid and high bands for 5G. This means that current outdoor 5G systems deployed in the 3.5 Gigahertz (GHz) bands will likely suffer in indoor environments.

The energy consumption of an indoor 5G network is estimated to be 87.6-Kilowatt hour/m2/year or higher, depending on the different types of buildings, and studies reveal that there is an increasing trend of power consumption of wireless networks. With 6G expected to be 10X to 100X more energy efficient than 5G, energy efficiency of in-building wireless has become one of the concerns in the building design industries and the wireless communication.

There is a general trend toward prioritization of green and sustainability aspects in vendors’ development plans. Huge efforts have been achieved by investing in more power-efficient hardware and software over the years, and some of them are:

• Smart Features to Reduce Energy Consumption: One commonly used green feature is the development of deep dormancy mode, which is activated by switching off various components to optimize energy usage in the network when traffic is low. The feature can be applied under timing mode or Artificial Intelligence (AI) mode. This green feature has proven to be effective in reducing energy usage; for instance, Huawei’s PowerStar2.0 helps cut 25% of the power consumption at a Pico Remote Radio Unit (pRRU) on a workday.
• Solutions to Support Multi-Band and Multi-Operator: In places like shopping malls and arenas, it can be challenging to ensure all users receive the same level of service regardless of who their service provider is. Deploying in-building wireless can be expensive to achieve sufficient coverage. Operators may deploy different spectrum, so solutions supporting multi-band and multi-operator are desirable. Vendors like Ericsson offer such indoor solutions that support multi-band and multi-operator over a single cable and the absolute power consumption is less than 55 watts. They are cost-effective, more efficient, and reduce equipment footprints. By leveraging a shared indoor radio infrastructure, operators can achieve 50% Total Cost of Ownership (TCO) saving. This type of solution has been deployed by Ooredoo Qatar in stadiums across the country and achieves speeds beyond 1 Gigabit per Second (Gbps).
• Solutions to Reuse Existing Architecture: In-building solutions, such as passive DAS face a challenge in capacity expansion, but this creates a problem for operators in countries like China where a good amount of passive DAS is used. To help operators solve this issue, ZTE proposed eDAS, which makes use of the traditional DAS architecture to achieve low-cost requirements in low-value scenarios. eDAS has been deployed in major cities and provinces, including Guangdong, Shandong, and Beijing, and it was found that downlink and uplink performance can improve by 35% and 25%, respectively. eDAS can also help cut deployment cost by 80% compared to a new DAS.

Most operators today still focus on macrocell deployments because operators set priorities to serve their subscribers who are mainly in the consumer domain, connected by public networks. Eventually, macro networks will no longer cope with the increasing data traffic alone, and this is when indoor solutions, such as small cells, are expected to accelerate around 2025. Then, macro and micro sites will share coverage in plenty of areas, which creates opportunity for energy saving with optimal macro-micro coordination. Huawei is currently testing a future technology macro-micro coordination, which is perfectly suitable for these applications. Macro sites cover the streets during the daytime and adjust their beam toward indoor during nighttime to help indoor sites save energy by shutting down the related LampSites. Initial results reveal that 4% of energy can be saved with 20% pRRUs in deep dormancy for 8 hours in a building of 20 Square Kilometers (km2). Huawei continues to advance this technology and operators should help test it, allowing the software to reach the market faster and reduce the energy burden for many.

Intelligent sensing is another technology expected to help reduce energy consumption further. When a visitor moves toward the border pRRU, the neighboring pRRUs will go into service mode, and then all the pRRUs along the visitor’s pathway are activated in sequence. Once the visitor moves away, the border pRRU goes back to sensing mode and the other pRRUs go into energy-saving mode. This feature is being explored Huawei. ZTE has a similar kind of feature; its PowerPilot enables sensor point control to help save energy at the pRRU level. In a trial with Shaanxi Mobile, it helped reduce energy consumption by 20%. 5G enables connecting a massive number of sensors, and a building becomes greener through a massive amount of IoT sensors.

Although in-building wireless is already energy efficient, it will be helpful if vendors can provide more clear information on energy utilization of their products, as a percentage figure is abstract and subjective. Transparency may create more competition that could accelerate product development. Furthermore, vendors can improve their sustainability efforts by participating in platforms like EcoVadis, which provides business sustainability ratings to help businesses better assess the social, environmental, and ethical performance of their own operations and those in their supply chain. Having s sustainable plan that outlines actions to ensure energy efficiency is a Key Performance Indicator (KPI) in the design process and also helps result in greener system implementations.