Serious wireless efficiency gains in the pipeline

18 Nov 2012

Two reports from the wireless-tech academic research front: how to double spectrum efficiency in MIMO wireless networks, and how to improve Wi-Fi performance 700% with a software upgrade.

1. Doubling spectrum efficiency with full-duplex radio

Two researchers at the University of California Riverside Bourns College of Engineering have published a paper on a new technique for MIMO that essentially doubles spectrum efficiency by enabling full-duplex transmission of broadband data.

Currently cellular networks use half-duplex radios – which means the uplink and downlink transmit and receive on separate bands. Full duplex radios, which transmit signals at the same time in the same frequency band, have been around for some time, but the challenge of using them in mobile broadband networks is dealing with the interference between the transmit and receive channels. Base stations transmit at much higher power levels, which drowns out incoming signals from devices in the same band.

The solution, according to a paper from professors Yingbo Hua and Ping Liang, is “time-domain transmit beamforming” (TDTB), which “digitally creates a time-domain cancellation signal, couples it to the radio frequency frontend to allow the radio to hear much weaker incoming signals while transmitting strong outgoing signals at the same frequency and same time”, according to UCR Today:

“We believe the future applications of full duplex radios are huge, ranging from cell towers, backhaul networks and wireless regional area networks to billions handheld devices for data intensive application such as FaceTime,” said Liang, who added that the researchers have had discussions with several major wireless telecommunication equipment companies.

Liang and Hua believe their research has commercial potential in part because most of the core components required are digital and therefore costly new components won’t need to be added to existing infrastructure.

You can find the technical details here.

2. Up to 700% better throughput for Wi-Fi

Researchers at North Carolina State University have developed a new software program that they claim can improve data throughput in Wi-Fi access points in heavy-usage areas by up to 700%.

The software – called WiFox – targets the problem of Wi-Fi congestion in high-population environments such as cafes and airports, which occurs when lots of people try to download data at the same. The problem isn’t so much the capacity of the downlink to send data as the ability of the AP to field data requests from users being sent upstream. The more users send data requests on the same channel, the harder it is for the AP to keep up with them all.

What WiFox does is monitor WiFi channel traffic and prioritizes data based on the size of the data backlog on that channel.

From the press release:

The amount of priority the access point is given depends on the size of the backlog – the longer the backlog, the higher the priority. In effect, the program acts like a traffic cop, keeping the data traffic moving smoothly in both directions.

The research team tested the program on a real WiFi system in their lab, which can handle up to 45 users. They found that the more users on the system, the more the new program improved data throughput performance. Improvements ranged from 400 percent with approximately 25 users to 700 percent when there were around 45 users.

Arpit Gupta, a Ph.D. student in computer science at NC State and lead author of a paper on WiFox, says the software can be incorporated into existing Wi-Fi networks as a software update.

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