Hybrid beamforming with spatial modulation in multi-user massive MIMO mmWave networks

Abstract

The cost of radio frequency (RF) chains is the biggest drawback of massive MIMO millimeter wave networks. By employing spatial modulation (SM), it is possible to implement lower number of RF chains than transmit antennas but still achieve high spectral efficiency. In this work, we propose a system model of the SM scheme together with hybrid beamforming at the transmitter and digital combining at the receiver. In the proposed model, spatially-modulated bits are mapped onto indices of antenna arrays. It is shown that the proposed model achieves approximately 5dB gain over classical multi-user SM scheme with only 8 transmit antennas at each antenna array. This gain can be improved further by increasing the number of transmit antennas at each array without increasing the number of RF chains.

Energy Efficient Transmit-Receive Spatial Modulation for Uplink-Downlink Large-Scale MIMO Systems

“…In hybrid TSM as proposed in [7], the UT antennas are divided into N groups each contains N g antennas. Incoming bit stream is divided into two parts where the first log 2 N bits are used to choose the antenna array index and the remaining log 2 M bits are modulated according to an M -ary modulation scheme.…”

“…The authors in [6] show that RSM based on minimum-meansquare-error precoding achieves better performance under both total power constraint and per-antenna power constraints. The hybrid hardware architecture is combined with transmit spatial modulation (TSM) in [7]. In this work, the spatial domain is exploited by adopting antenna arrays instead of single antennas, with the goal of benefiting from beamforming gain.…”

Energy efficiency in hybrid beamforming large-scale mmwave multiuser MIMO with spatial modulation

“…Finally, α aj ,i l , CN (0, 1), represents the channel gain and the path loss of the path. The analog beamformer and digital precoder vectors of user j are f aj ,j ∈ C N T ×1 and p aj ,j ∈ C 1×K , which are considered fixed and chosen as described in [29]. The vector s ∈ C K×1 contains the symbols of all the users, and finally n i ∈ C N R ×1 is the noise vector, modeled as a complex Gaussian vector with zero-mean and covariance matrix σ 2 I N R .…”

“…where the receive combiner w ai,i is chosen according to [29], and ρ is the total power transmitted by the BS. Assuming uniform power allocation, the transmit power allocated to each user is ρ i = ρ/K, and since the interference from other users is eliminated by employing transmit precoding, (3) simplifies to…”

Energy Efficient Transmit-Receive Hybrid Spatial Modulation for Large-Scale MIMO Systems

“…However, TSM schemes suffer from low antenna gain because most of the transmit antennas are silent which is an impairment at higher frequencies (28 GHz) where large beamforming gain is needed to combat the severe path-loss. Hybrid TSM (HTSM) schemes have been reported in [20], [21] to exploit the phase shifters in attaining high beamforming gain where SM bits are mapped into a group of antennas each connected to phase shifter instead of single antenna of TSM. However, outdoor propagation of mmWave signals exhibits poor scattering which entails spatially sparse and rank deficient channel matrices as explained in Sec.…”