Codebook design of generalized space shift keying for FDD massive MIMO systems in spatially correlated channels

The massive multiple-input multiple-output (MIMO) system is one of the most promising techniques for beyond fourth-generation (B4G) wireless communication systems. However, supporting a downlink (DL) frequency-division duplex (FDD) massive MIMO system for backward compatibility might be a bottleneck problem because the number of feedback bits for the FDD system is proportionate to the number of transmit antennas. In this perspective, the well-known generalized space-shift keying (GSSK) can be a suitable candidate to support the DL FDD massive MIMO system. In this paper, the GSSK activating all transmit antennas at once is named as port modulation (PM). PM has enormous potential to utilize the spatial resources of the massive MIMO system by linking precoding and the well-known spatial modulation (SM). In this paper, we propose a codebook design for PM, which makes it possible to improve the average bit error probability (ABEP) of PM without instantaneous channel state information (CSI) at the transmitter (CSIT) or additional efforts to design shaping filters. Simulation results show that when the base station consists of a large number of spatially correlated transmit antennas, the proposed codebook design offers lower ABEP than other limited feedback or open-loop systems, such as spacen-time-block-coded SM (STBC-SM).