Approaching the Zero-Outage Capacity of MIMO-OFDM Without Instantaneous Water-Filling

Orthogonal-frequency-divisionmultiplexing(OFDM) transforms a frequency-selective multiple-input multiple-output (MIMO) fading channel into a MIMO-OFDM channel that has a well-defined outage capacity. A transmitter with channel knowledge can achieve this capacity by a combination of eigenbeamforming and water-filling; the eigenbeamforming transforms the MIMO-OFDM channel into a parallel bank of scalar channels, and the water-filling procedure optimally allocates rate and energy to the scalar channels--a form of adaptive modulation. This paper shows that the water-filling procedure is not necessary to approach the zero-outage capacity of the MIMO-OFDM channel; it is sufficient instead to use a combination of eigenbeamforming and a fixed (nonadaptive) rate allocation. The fixed allocation depends only on the statistics of the channel and is independent of the particular channel realization. This paper proves that the capacity penalty incurred by the fixed allocation approaches zero as the...

• Type: Journal
• Year: 2008
• Where: TIT
• Authors: Joon Hyun Sung, John R. Barry
• Keywords: MIMO-OFDM Channel, Scalar Channels, TIT 2008, Water-filling Procedure