Keeping Wireless Access Networks Energy Efficient

August 15, 2013

By Ashok Bindra - Power Protection Contributor

With Internet traffic exploding, data centers around the world are only getting bigger and bigger. At this rate, they are responsible for 2 percent of the world's electric consumption today, leaving 1.5 percent of the global carbon footprint. Hence, there is a lot of pressure on facility managers (FMs) to reduce power consumption wherever possible.

Because data centers use lot of power to keep the servers cool, the operators are adopting highly efficient servers, cooling systems, and backup generators. Additionally, they are deploying energy efficient IT equipment and developing networks that deliver maximum throughput with minimum use of power.

According to a report by TMC (News - Alert), globally data centers consume 30 billion Watts of power. If that number is divided with the 2.4 billion Internet users around the world, it only comes down to less than 15 W per each user. This number can be further reduced if the access networks themselves are made more power efficient.

A recent study by the researchers from the University of Thessaly and Centre for Research and Technology Hellas in Greece have shown that the energy consumption of 802.11n wireless protocol is up to 75 percent lower than that of the older standards. The researchers attribute this improvement to innovative ‘frame aggregation’ mechanisms.

According to this report, frame aggregation is a feature of the 802.11e and 802.11n wireless LAN standards that increases throughput by sending two or more data frames in a single transmission. It turns out that besides improving network performance, it also reduces energy usage. The researchers believe that it is a significant improvement as tens of billions of devices will connect to the Internet during the next decade. According to some sources, by 2015, access networks around the world will consume ten times more power than data centers.

Although, the evolution in the 802.11 wireless network standard improved data throughput and reliability with each introduction of 802.11 protocols, there was no reduction in power because all them use the same Media Access Control (MAC) architecture. However, the case is different with 802.11n, which features two types of frame aggregation--MAC Service Data Unit (MSDU) aggregation and MAC Protocol Data Unit (MPDU) aggregation.

 To demonstrate the impact of frame aggregation on energy efficiency, the researchers set up an experiment in which they compared the older 802.11a/g networks to 802.11n. According to the results, with A-MPDU aggregation active, the energy consumption per transmitted bit is 75 percent lower than without aggregation.

Edited by Rich Steeves