Researchers at Rice University have tested an array of 64 antennas that use their Argos technology to create a multi-user beam-forming MIMO array that’s able to communicate with 15 devices simultaneously on the same frequency.
The experiment is detailed in the paper Argos: Practical Many-Antenna Base Stations. The system uses commercial off-the-shelf radio modules from Rice University's WARP (Wireless Open-Access Research Platform operating in the 2.4 GHz band. Single-user (or single-beam) beam forming antennas have been widely used in radar and satellite applications (see last week's article on Kymeta), but this is the first demonstration I've seen of a large multi-user beam forming (MUBF) antenna able to serve multiple users with independent beams (and nulls, to reduce interference) that is able to use MIMO techniques to increase spectral efficiency.
The paper, by Clayton Shepard, Hang Yu, Narendra Anand, Li Erran Li, Thomas Marzetta, Richard Yang and Lin Zhong (with Rice University, Bell Labs and Yale University), provides yet another reason to question the FCC's push to reallocate UHF TV spectrum. As I've written previously, the value of this “low frequency” spectrum for wireless broadband is decreasing, and by the time the incentive auctions are completed, the main value of the spectrum to the wireless carriers is likely to be in removing a competitor in the content delivery business. Technology that depends on a large number of antennas and beam steering works best at higher frequencies where antennas are smaller. Note that at 85 bps/Hz, one 20 MHz channel would be able to provide 1.7 Gbps of capacity.
Is UHF TV spectrum really needed to solve the looming “spectrum crisis?”