Spatial modulation (SM) and generalized SM (GSM) are emerging low-complexity multiple-input and multiple-output (MIMO) schemes for wireless communications. The operating principle of SM/GSM is radically different from conventional spatial multiplexing (SMX) MIMO schemes like D-BLAST and V-BLAST. In SMX, typically all the transmitter (TX) antennas are activated for simultaneous transmission of multiple data streams. In SM/GSM, however, only a subgroup of TX antenna(s) are activated and switched for data transmission. In SM/GSM, in addition to the conventional IQ domain, information is carried also in a so-called spatial domain. The main benefits of using SM/GSM, as compared to SMX, include: 1) reduced hardware complexity especially at the TX, 2) improved energy efficiency at the TX, and 3) reduced signal processing complexity at the receiver (RX). In this thesis, we study SM/GSM and target the application to broadband indoor line-ofsight (LOS) millimeter-wave (mmWave) communications.