Space Shift Keying Modulations for Low Complexity Internet-of-Things Devices
Résumé
—The new MIMO schemes commonly referred to as spatial modulations (SM) use the index of the transmit (resp. the receive) antenna to transmit additional data and hereby increase the spectral efficiency of digital communication systems. Most of proposed SM schemes allow for simultaneously transmitting two types of symbols, the classical IQ-symbols of a M-order modulation, and a spatial information related to the index of the transmit or targeted receive antenna(s). In this paper, we propose a complete uplink and downlink transmission system between a Base Station and a Connected Device for Internet-of-Things application based on SM. We thus concentrate on SM schemes only conveying spatial information for both downlink (from a base station to a connected device) and uplink (from a connected device to a base station) transmissions and leading to low complexity at the device. For the downlink we propose the use of an existing receive SM, the ERASK that is an extension of a very simple receive spatial modulation known as RASK (Receive Antenna Shift Keying) which aims at increasing the spectral efficiency. For the uplink, we firstly propose a new scheme which analogy with ERASK is highlighted. Both ERASK and ESSK can be efficiently used in the global system while keeping very low complexity at the device side. All complexity is reported at the base station with pre-processing function used to concentrate the signal energy towards the device targeted antenna(s). The channel estimation is also only needed at the base station for pre-processing of the ERASK and detection process of the ESSK.