Joint Design of the Spatial and of the Classic Symbol Alphabet Improves Single-RF Spatial Modulation

Pranav S Koundinya,Lajos Hanzo,K.V.S Hari

doi:10.1109/access.2016.2600246

Abstract

A new joint spatial and classic symbol alphabet is designed for spatial modulation (SM)-based multiple-input multiple-output systems. The employment of multiple active antennas instead of a single active antenna is proposed for increasing the achievable throughput and the joint design of the antenna selection and classic transmit symbol is explored, while maintaining the compelling advantages of SM. This framework combines the bit-to-antenna mapping and classic bit-to-constellation mapping into a single function, which defines the joint-alphabet and the joint optimization of the amplitude-phase modulation and its constellation for transmission over multiple active antennas. The conventional SM system is also interpreted within our framework. An example design is proposed, which aims for a high spectral efficiency of 11 b per channel use, achieving a gain of up to 5 dB over generalized SM (GSM).

Highlights

Multiple-input multiple-output (MIMO) wireless systems exhibit an increased performance
SIMULATION RESULTS This section characterizes the performance of the proposed alphabet design for our Joint Spatial & Classic Symbol Alphabet (JS&CSA) framework associated with PSK and the appropriately modified star-QAM (Appendix B) using both the model derived from Section V and from Monte-Carlo simulations
The results shown for the proposed joint alphabet design have been obtained using a twin-ring star-QAM with a ring-ratio of α = 1.3, which was observed to provide the best performance for the configuration considered

Summary

INTRODUCTION

MIMO wireless systems exhibit an increased performance. SM proposed by Mesleh et al [1], where each APM symbol (QAM or PSK) is transmitted over one of the transmit antennas (TAs), constitutes a recent MIMO scheme developed for using a single Radio Frequency (RF) chain. This is achieved by arranging for the spatial-vector entries of the alphabet to have only a single non-zero component. We note that having more active TAs reduces the MED (and the overall performance) as mentioned earlier in the context of Fig. 3 Each of these spatial vectors is multiplied by the corresponding MNa APM constellation values in order to obtain the entire set of spatial-symbol vectors. The proposed scheme transmits the same APM symbol aMl on all the active TAs in a given spatial vector (i.e., uses a single RF-chain), the IAI is completely avoided at the receiver. These results are used for obtaining the theoretical SER performance through an i.i.d Rayleigh channel in the following sub-sections

IDENTICALLY DISTRIBUTED FADING

SIMULATION RESULTS

CONCLUSIONS