SignalingFree Bit and Power Loading in MIMO OFDM Systems This manuscript proposes a novel bit and power loading algorithm for multipleinput multipleoutput orthogonal frequency division multiplexing systems in timedivision duplex mode, in which the modulation schemes are automatically classified at the receiver. Due to decoupling the spatial streams by linear precoding, an adaptation at the transmitter side is enabled which targets a constant minimum distance of all constellation sets at the receiver side. Indeed, this fact supports the distinctiveness of different modulation schemes at the receiver. Simulations of typical indoor propagation scenarios reveal an increased modulation classification reliability compared to previous methods. Furthermore, numerical results show that the proposed adaptive transmission scheme clearly outperforms both a signalingbased adaptive and a nonadaptive concept, especially at lower signaltonoise power ratios.

MultiMode Generalized SpaceTime Index Modulation: A HighRate Index Modulation Scheme for MIMOISI Channels In this paper, a new index modulation technique, referred to as the multimode generalized spacetime index modulation (MMGSTIM) is presented. MMGSTIM is a highrate index modulation scheme for multiantenna intersymbol interference (MIMOISI) channels. The proposed MMGSTIM is a single carrier scheme with zero padding (ZP). MMGSTIM performs xe2x80x98modeindexingxe2x80x99 to efficiently increase the spectral efficiency. In a given MMGSTIM frame, disjoint subsets of spacetime slots are used to transmit modulation symbols from disjoint modulation alphabets (referred to as the modes). The choice of which spacetime slots are used for transmission of a particular mode in an MMGSTIM matrix conveys information bits. Thus, MMGSTIM is a generalization of the wellknown index modulation schemes such as spatial modulation (SM), generalized spatial modulation (GSM), and spacetime index modulation. Here, an analytical characterization of the diversity order of the proposed MMGSTIM scheme and the conditions required to maximize the transmission rate of multimode index modulation schemes are derived. Through simulations, it is shown that the proposed MMGSTIM scheme can achieve better performance compared to other modulation schemes in MIMOISI channels.