New antenna could vastly increase wireless net capacity
Researchers from Rice University, Yale University and Bell Labs have demonstrated an antenna technology that would enable mobile network operators to increase capacity without adding spectrum.
As a bonus, using the antennas would save on energy. Furthermore, they can be built using mostly off-the-shelf hardware. If there’s a catch, it’s that the technology is about five years away from being ready to be commercialized.
Researchers from Rice built a version of the multi-antenna system capable of multi-user beamforming (MUBF). The demonstration version included an array of 64 antennas integrated in a single base station, simultaneously communicating using focused beams with 15 users – all on the same frequency.
The researchers said that would translate to a 6.7-fold increase in network capacity, according to the paper. They also expect to be able to scale up the technology with a denser array of antennas, leading to further increases of capacity.
Rice U. presented a paper on the technology, called Argos, at the Association for Computing Machinery's MobiCom 2012 wireless research conference in Istanbul.
Argos project co-leader Lin Zhong, associate professor of electrical and computer engineering and of computer science at Rice, said, "The key is to have many antennas, because the more antennas you have, the more users you can serve."
As far as the researchers are aware, this is the first demonstration that MUBF is possible, according to their paper.
Implementing MUBF has been difficult for a number of reasons, according to Zhong. "There are all kinds of technical challenges related to synchronization, computational requirements, scaling up and wireless standards," he said. "People have really questioned whether this is practical, so it's significant that we've been able to create a prototype that actually demonstrates that this works."
"There's also a big payoff in energy savings," according to Clayton Shepard, the graduate student who built the demonstration antenna array. "The amount of power you need for transmission goes down in proportion to the number of antennas you have. So in Argos' case, we need only about one-sixty-fourth as much energy to serve those 15 users as you would need with a traditional antenna."
While the demonstration was accomplished using OTS WARP boards based on Xilinx FPGAs, implementing the technology would require new network hardware (the network-level challenges, according to the paper, include terminal paging, optimal grouping and scheduling of terminals, and handover between cells) and a new generation of smartphones and tablets. It might also require changes in wireless standards.
Current beamforming is not scalable, the researchers assert in their paper, so they had to devise a completely novel approach to the technique. Accomplishing MUBF is computationally complex and requires local computation, and that’s where the WARP boards come in.
Another initial problem is that the antenna array is currently very large, posing problems of mounting them.
"The bandwidth crunch is here, and carriers need options," Zhong said. "They're going to pay close attention to any new technologies that may allow them to serve more customers with fewer resources."
Research co-authors include Hang Yu and Narendra Anand, both of Rice; Li Erran Li and Tom Marzetta, both of Bell Labs; and Yang Richard Yang of Yale University. The research was supported by the National Science Foundation, Bell Labs, Alcatel-Lucent and the Air Force Office of Sponsored Research.