# A Generalized Spatial Modulation System Using Massive MIMO Space Time Coding Antenna Grouping
## 1 Introduction  
In modern communication systems, network traffic and the demand for a greater data rates are growing rapidly due to the rapid increase of using smart devices and cloud computing. Due to users increasing demand for high data rates all over the world, a lot of research is being done to achieve their requirements. The multiple input multiple output (MIMO) techniques are highly recommended, as they can achieve higher throughput compared to the single input single output systems (SISO) [1]. Increasing the number of transmitting antennas has the ability to enhance system performance due to introducing a diversity gain in the received data symbols which is enhanced by increasing the number of transmit antennas [2]. The MIMO system can also reduce the effect of channel on the information data sent from a transmitter to a receiver end [3]. On the other hand, the MIMO system suffers from high complexity during implementation. The MIMO wireless communication system is overviewed in [4], which shows that the new massive MIMO system is an emerging base station (BS) technology that deploys a very large number of BS antennas to enhance spectral efficiency, communication reliability and increase the transmission data rate. Another approach to enhanced data rate is using beamforming (BF) to perform transmit diversity and enhance the average BER (bit error rate), especially in correlated fading channels, but this still does not achieve the nowadays required high data rates [5]. The MassiveMIMO reduces the inter user interface and enhances the physical security due to transmission over orthogonal MIMO channels [6]. This essential tradeoff between the diversity gain and the multiplexing gain is critical to the performance of MIMO systems [7]. So, another technique has to be proposed. A lot of research has been done to enhance the performance of a massive MIMO system. In order to increase the spectral efficiency and to reduce the inter-channel interference (ICI), a spatial multiplexing MIMO technique is proposed called spatial modulation (SM) [8]. In general, SM using MIMO can achieve rate improvement and thus higher spectral efficiency. However, one of the chronic problems is that it gives a higher BER when fixing the signal-to-noise ratio (SNR). A specified procedure is performed in [9] to enhance the BER by activating only one antenna at the transmitter side at each instance to transmit a certain data symbol. In order to increase the overall spectral efficiency, the base-two logarithm of the number of transmit antennas is used by [PERSON] et al. [10] using an active antenna index. Furthermore, the data sent depends on the incoming random data bits, taking into consideration that the total number of transmit antennas must be a power of two. At the receiver side, a detector should be added that can jointly estimate the active antenna index and the sent data symbol [11]. In [12], the proposed SM decoder is performed. Then, in [13], an SM combined with trellis-coded modulation (TCM) was recently proposed. Another approach is done in [14] by using antennas grouping at the transmitter with SM to increase the data rate by setting antennas in more than one group and antennas in the same group to be planned at equal distances. Recently, when the spatial dimension was introduced, a capacity gain could be achieved. It is coordinated by the antenna indices to be introduced for the developed MIMO schemes. In order to avoid the ICI and the inter antenna interference (IAI), only one antenna must be active at transmitter, which results in a further reduction in decoding complexity and flexibility in system design [15]. Furthermore, a novel scheme approaching even higher capacity by combining the amplitude/phase modulation techniques with antenna index modulation, named multiple access spatial modulation (SM), is proposed by [PERSON] et al. in [16] in order to expand the constellation symbols for a three dimensional one (the spatial dimension and the complex plane are included).