Multicarrier systems with cross-layer adaptive frequency diversity

Among the many varieties of multicarrier, code-division multiplex orthogonal frequency-division multiplex (CDM-OFDM) has received considerable attention due to its superior resilience against subcarrier fading in comparison with conventional OFDM. More recently, group-orthogonal CDM-OFDM (GO-CDM-OFDM) has been considered as a suitable method to extract the maximum frequency diversity of the wireless channel by splitting the available subcarriers into (orthogonal) groups and applying optimum detection at the receiver on a per-group basis. One critical parameter of this scheme is the group size as it can effectively act like a complexity-performance trading knob. In this work an adaptive technique to dynamically adjust the group size as a function of the instantaneous operating scenario is presented. It is shown how this adaptivity can bring along important reductions in complexity without compromising error performance.