Iterative Detection for Spatial Multiplexing with Adaptive Power Allocation

Inhalt:
In this contribution, bit and transmit power allocation are analyzed for spatial division multiplexing (SDM) schemes with iterative detection. Existing bit loading and transmit power allocation techniques are often optimized for maintaining both a fixed power and a fixed target bit-error rate while attempting to maximize the overall data-rate. However, delay-critical real-time interactive applications, such as voice or video transmission, may require a fixed data rate. Here, in addition to bit- and power loading we invoke channel coding and identify the most beneficial number of signalling levels that minimize the bit-error rate under the constraint of a given data throughput. The performance is analyzed by both computer simulations as well as EXIT charts. The results demonstrate that adaptive power allocation combined with an appropriate choice of a modulation scheme for each MIMO layer is highly effective in uncoded scenarios whereas in coded systems, a uniform distribution of the transmit power seems to be a better choice.