On Antenna Subset Modulation: Its Single and Multi-beam Capabilities

Due to the increasing demand for wireless communications, both millimeter-wave band and spectral efficiency of transmission schemes have gained a great concern recently. Also, achieving secure wireless communications is of high importance. Recently, physical layer security has been intensively investigated as an extra layer of protection for wireless communications. Directional (DM) has been proposed as a mean to implement physical layer security. A special type of DM suitable for millimeter-wave wireless communications is antenna subset modulation (ASM) in which the small wavelength nature in millimeter-wave band is exploited to equip a transmitter with a large antenna array. By randomly choosing few elements of the array for transmitting a symbol, secure communication in a single direction is obtained. Using only a few portion of the antenna array in transmission makes this large array underutilized. the unused portion of the antenna array can be exploited to increase the spectral efficiency of ASM. In this paper, we introduce a survey on last advances on ASM and address its multi-directional transmission capabilities. An architecture for multi-directional ASM is introduced. Randomized and optimized antenna subset selection techniques are introduced and demonstrated by simulations.