Simplified Cross-Layer Optimization for Power Allocation in MIMO-OFDM Systems

This paper suggests an efficient power allocation scheme for multiple input and multiple output - orthogonal frequency division multiplexing (MIMO-OFDM) systems achieving near-optimum. We deal with power allocation problem with low complexity. It is well known that the conventional waterfilling algorithm runs repetitive calculations and logarithm operations to find out an optimal water level over whole time and spatial dimensions. To cope with this complexity problem, we investigate the problem structure originated from the characteristic of optimal waterfilling in MIMO-OFDM system through convex analysis, which leads to a unique step structure for optimal power allocation. Taking advantage of this structure, we propose a successive waterfilling algorithm with low complexity. The proposed algorithm calculates the allocated power of each subchannel recursively after setting an initial power by the step structure. Underlying assumption is that the perfect channel state information is available to both transmitter and receiver sides.