A System View on Iterative MIMO Detection: Dynamic Sphere Detection versus Fixed Effort List Detection

Multiple-antenna systems are a promising approach to increase the data rate of wireless communication systems. One efficient possibility is spatial multiplexing of the transmitted symbols over several antennas. Many different MIMO detector algorithms exists for this spatial multiplexing. The major difference between different MIMO detectors are the resulting communications performance and implementation complexity, respectively. Especially closed loop MIMO systems have attained a lot of attention in the last years. In a closed loop system, reliability information is fed back from the channel decoder to the MIMO detector. In this paper, we derive a basic framework to compare different soft-input soft-output MIMO detectors in open and closed loop systems. Within this framework, we analyze a depthfirst sphere detector and a breadth-first fixed effort detector for different application scenarios and their effects on area and energy efficiency on the whole system. We present all system components under open and closed loop system aspects and determine the overall implementation cost for changing an open loop system in a closed loop system.