Spatial modulation (SM) and generalized spatial modulation (GSM) are emerging low-complexity multiple-input and multiple-output (MIMO) schemes for wireless communications. The operating principle of SM/GSM MIMO systems are radically different from that of conventional spatial multiplexing (SMX) MIMO systems like the wellknown D-BLAST and V-BLAST. In SMX MIMO, typically all the transmitter (TX) antennas are activated simultaneously for simultaneous transmission of multiple data streams. The same number of TX chains (from baseband to RF) as the number of data streams are needed in SMX MIMO thus introducing significant hardware and signal processing complexity. However, in SM/GSM MIMO, only one/one sub-group of all TX antennas are activated for in-phase and quadrature (IQ) domain transmission. Meanwhile, the activated group of TX antennas is switched for so-called spatial domain transmission, i.e., information is transmitted both in the conventional IQ domain and a so-called spatial domain, where the latter is achieved by antenna switching. In this thesis, we consider the case of SM/GSM that transmits one IQ stream and one spatial stream. More specifically, we consider fixed-Nu generalized spatial modulation (FGSM) and variable-Nu generalized spatial modulation (VGSM). In contrast to conventional SMX MIMO schemes, the benefits of using the SM/GSM schemes to be considered lies in, but not limited to: 1) reduced hardware complexity especially at the TX, 2) improved energy efficiency due to use of only a single IQ chain at the TX, and 3) reduced signal processing complexity a the receiver (RX) due to the avoidance of inter-channel interference. Extensive research has been conducted on SM/GSM. However, so far, almost all works in the literature are concerned with SM/GSM at low-GHz frequencies (below 6 GHz). In this thesis, we target the application of SM/GSM to broadband indoor line-of-sight (LOS) millimeter-wave (mmWave) communications, and the major contributions are as follows: Considering that the indoor LOS mmWave channel is dominated by the LOS component and the non-line-of-sight (NLOS) components contribute only a very small portion to the total received power, we first neglect the NLOS components of the channel and seek to optimize the symbol error probability (SEP) and channel capacity of GSM based on the pure LOS component of the channel. Then we derive SEP and channel capacity expressions for LOS GSM and conduct numerical analysis based on the expressions derived. In the analysis, beamforming (BF) and SMX MIMO schemes are used as benchmarks. Another major contribution of this thesis lies in the proposal of hardware architectures for possible implementations of GSM at mmWave frequencies. We introduce different TX structures to address the different switching challenges of FGSM and VGSM. A power allocation optimization to the TX of VGSM will be performed and the energy efficiencies of the two TXs will be studied and compared. In addition, a hybrid digital/RF RX is proposed for both of the GSM schemes. We study the SEP and channel capacity performances of GSM using measured real-word 60 GHz indoor channel data. The channel measurement was carried out in an office environment at Brno University of Technology, Czech Republic. Since the theoretical studies mention above are mainly based on pure LOS channel models, the purpose of the study using measure channel data is therefore two-fold: 1) to validate the major claims of the theoretical studies, and 2) to study the impact of NLOS on the performance of LOS GSM. ] Over all, GSM will be shown to be a promising candidate for broadband indoor LOS mmWave communications.