Nortel demonstrated wireless transmission using Uplink Collaborative MIMO, a technique that could enable operators to serve up to double the number of mobile broadband subscribers supported in a cell site as current wireless technologies allow. Developed by Nortel, Collaborative MIMO is part of the WiMAX industry standard and is also being proposed for 3GPP WCDMA Long-Term Evolution (LTE) and 3GPP2 CDMA EV-DO Rev-C standards.
"Uplink Collaborative MIMO creates a technological disruption that offers revolutionary improvement in wireless network capacity and provides a clear path to 4G Mobile Broadband - of which WiMAX is the first technology," said John Hoadley, chief technology officer, Mobility and Converged Core Networks, Nortel.
The demonstration at Nortel's Advanced Wireless Lab in Ottawa, combined Multiple-Input, Multiple-Output (MIMO) antennas at both the cell site and on 4G devices with orthogonal frequency division multiplexing (OFDM) transmission technology. Nortel said the combination of these two technologies offers the ability to deliver the highest network bandwidth and greatest spectral efficiency capabilities at the lowest cost.
With OFDM, a single channel within a spectrum band is divided into multiple, smaller sub-carriers that transmit information simultaneously without interference.
MIMO allows multiple data streams to be transmitted at the same time and on the same sub-carriers through interference-free MIMO spatial channels. Due to unique spatial channels that result for each antenna path, interference between data streams is reduced. As a result, OFDM-MIMO substantially increases the bandwidth and spectral efficiency.
Nortel describes Uplink Collaborative MIMO as a further enhancement that enables the use of the same channel sub-carriers by multiple devices and subscribers - effectively allowing them to share the same sub-carrier without interference. Without Collaborative MIMO, the traffic being carried on a single sub-carrier would not be maximized across multiple subscribers. The result would be that the traffic would be severely limited, preventing users from having a true broadband experience and limiting VoIP capacity such that conversations would be unintelligible.
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- In March 2005, Nortel was the first company to demonstrate OFDM-MIMO at 37 Mbps peak data rates in 5 MHz of spectrum in the downlink, with the transfer of a 128 MB file in just 30 seconds.
