A STUDY ON LOW-COMPLEXITY TRANSMIT ANTENNA SELECTION FOR GENERALIZED SPATIAL MODULATION

ABSTRACT: Generalized spatial modulation (GSM) maps its information to the index of the transmit antenna combination, making simultaneous transmission of multiple symbol possible. However, SM outperform GSM scheme in terms of error performance of the same data rate, due to average power effect. Transmit and receive diversity or the combination of both allow huge improvement in mimo systems in  terms of error performance. In this paper, we investigate a near optimal low-complexity Euclidean distance antenna selection (LC-EDAS) technique in GSM system, to further improve the performance of the conventional GSM system. The LC-EDAS technique independently search across signal and spatial dimension to eliminate the worse channel prior to transmission. Secondly, we investigate a sub-optimal low-complexity transmit antenna selection (LCTAS) in the GSM system to further reduce the computational complexity (CC) imposed by LC-EDAS. The Monte Carlo simulation results obtained reveals a trade-off between the GSM scheme with LC-EDAS and GSM scheme with sub-optimal transmit antenna selection in terms of error performance and CC. ABSTRAK: Modulasi Spatial Keseluruhan (GSM) menghubung informasi kepada indeks kombinasi antena yang dipancarkan, membuatkan pemancaran keseluruhan simbol dapat dilakukan. Walau bagaimanapun, SM lebih bagus daripada skim GSM pada prestasi kesilapan pada kadar data yang sama, kerana kesan purata kuasa. Kepelbagaian penghantaran dan penerimaan ataupun kombinasi keduanya memberi pembaharuan yang lebih besar dalam sistem mimo pada prestasi kesalahan. Penyelidikan ini akan mengkaji optima terdekat Euclidean kurang rumit, melalui teknik (LC-EDAS) pilihan jarak antenna dalam sistem GSM, bagi menambah prestasi sistem GSM sedia ada. Teknik LC-EDAS secara sendiri mencari signal dan dimensi separa bagi mengurangkan saluran lebih teruk semasa penghantaran. Kedua, kami mengkaji sub-optima proses pemilihan kurang rumit penyebaran antena (LCTAS) dalam sistem GSM bagi mengurangkan kerumitan pengiraan (CC) yang dikenakan oleh LC-EDAS. Keputusan simulasi Monte Carlo yang diperoleh menunjukkan timbangan antara skim GSM dan LC-EDAS dan skim GSM bersama sub-optima proses pemilihan penyebaran antena berdasarkan kesilapan prestasi dan CC

Transmit antenna selection for multiple-input multiple-output spatial modulation systems

The benefits of transmit antenna selection (TAS) invoked for spatial modulation (SM) aided multiple-input multiple-output (MIMO) systems are investigated. Specifically, we commence with a brief review of the existing TAS algorithms and focus on the recently proposed Euclidean distance-based TAS (ED-TAS) schemes due to their high diversity gain. Then, a pair of novel ED-TAS algorithms, termed as the improved QR decomposition (QRD)-based TAS (QRD-TAS) and the error-vector magnitude-based TAS (EVM-TAS) are proposed, which exhibit an attractive system performance at low complexity. Moreover, the proposed ED-TAS algorithms are amalgamated with the low-complexity yet efficient power allocation (PA) technique, termed as TAS-PA, for the sake of further improving the system's performance. Our simulation results show that the proposed TAS-PA algorithms achieve signal-to-noise ratio (SNR) gains of up to 9 dB over the conventional TAS algorithms and up to 6 dB over the TAS-PA algorithm designed for spatial multiplexing systems

Transmit antenna selection algorithms for quadrature spatial modulation.

Master of Science in Electronic Engineering. University of KwaZulu-Natal, Durban 2016.The use of multiple-input multiple-output (MIMO) systems has become increasingly popular due to the demand for high data rate transmissions. One such attractive MIMO system is spatial modulation (SM). SM is an ideal candidate for high data rate transmission as it is able to achieve a high spectral efficiency, whilst maintaining a relatively low receiver complexity. SM completely avoids inter-channel interference and the need for inter-antenna synchronisation. Furthermore, SM requires the existence of only one radio frequency chain. However, the need to increase the spectral efficiency achieved by SM is a topic which continues to garner interest. Quadrature spatial modulation (QSM) was introduced as an innovative SM-based MIMO system. QSM maintains the aforementioned advantages of SM, whilst further increasing the spectral efficiency of SM. However, similar to SM, the need to improve the reliability (error performance) of QSM still exists. One such strategy is the application of a closed-loop technique, such as transmit antenna selection (TAS). In this dissertation, Euclidean distance-based antenna selection for QSM (EDAS-QSM) is proposed. A substantial improvement in the average error performance is demonstrated. However, this is at the expense of a relatively high computational complexity. To address this, we formulate an algorithm in the form of reduced-complexity Euclidean distance-based antenna selection for QSM (RCEDAS-QSM) that is used for the computation of EDAS-QSM. RCEDAS-QSM yields a significant reduction in the computational complexity, whilst preserving the error performance. To further address computational complexity, four sub-optimal, low-complexity, TAS schemes for QSM are investigated, viz. capacity optimised antenna selection for QSM (COASQSM), TAS for QSM based on amplitude and antenna correlation (TAS-A-C-QSM), lowcomplexity TAS for QSM based on amplitude and antenna correlation using the splitting technique (LCTAS-A-C-QSM) and TAS based on amplitude, antenna correlation and Euclidean distance for QSM (A-C-ED-QSM). Amongst the sub-optimal algorithms, A-C-ED-QSM provides superior error performance. While the computational complexity of A-C-ED-QSM is higher than the other sub-optimal, lowcomplexity schemes, there is a significant reduction in the computational complexity compared to the optimal RCEDAS-QSM. However, this is at the expense of error performance. Hence, clearly a trade-off exists between error performance and computational complexity, and is investigated in detail in this dissertation

A Unified Precoding Scheme for Generalized Spatial Modulation

© 1972-2012 IEEE. Generalized spatial modulation (GSM) activates Nt (1 ≤ nt < Nt) available transmit antennas, and information is conveyed through nt modulated symbols as well as the index of the nt activated antennas. GSM strikes an attractive tradeoff between spectrum efficiency and energy efficiency. Linear precoding that exploits channel state information at the transmitter enhances the system error performance. For GSM with nt=1 (the traditional SM), the existing precoding methods suffer from high computational complexity. On the other hand, GSM precoding for nt ≥ 2 is not thoroughly investigated in the open literature. In this paper, we develop a unified precoding design for GSM systems, which universally works for all nt values. Based on the maximum minimum Euclidean distance criterion, we find that the precoding design can be formulated as a large-scale nonconvex quadratically constrained quadratic program problem. Then, we transform this challenging problem into a sequence of unconstrained subproblems by leveraging augmented Lagrangian and dual ascent techniques. These subproblems can be solved in an iterative manner efficiently. Numerical results show that the proposed method can substantially improve the system error performance relative to the GSM without precoding and features extremely fast convergence rate with a very low computational complexity

Index modulation for next-generation wireless networks.

Doctoral Degree, University of KwaZulu- Natal, Durban.The desirability of high throughput and superior system performance for multimedia services requires schemes that can achieve high spectral efficiency. However, this imposes high system/hardware complexity due to the large number of antennas required at the transmitter. This led to the development of several innovative multiple-input multiple-output (MIMO) techniques in the research community, such as generalized spatial modulation (GSM). GSM is a spatial modulation (SM) based scheme, which employs transmit antenna combinations coupled with identical symbols to convey additional information. This made the use of multiple transmit antennas possible in index modulation, improving the setback/limitation of hardware complexity experienced in the conventional MIMO and SM schemes. Furthermore, in the literature, an improved spectral efficient quadrature spatial modulation (QSM) based scheme termed generalized quadrature spatial modulation (GQSM) is proposed. In GQSM, the antennas at the transmitter are divided into groups and a unique symbol is employed across multi-active transmit antenna groups. Hence, GQSM requires less transmit antennas to achieve a high data rate when compared to its counterparts. However, GQSM requires multiple radio frequency (RF) chains, considering unique symbols are employed in each transmit antenna group. This motivates us to investigate single-symbol GQSM (SS-GQSM), which employs identical symbols across each group requiring a single RF chain. Recently, the application of RF mirrors termed media-based modulation (MBM) was introduced to the research community as a technique to enhance the spectral efficiency at a reduced hardware complexity. This motivates us to investigate MBM with single-symbol GSM to enhance its error performance and to mitigate the drawback of the requirement of multiple RF chains. In addition, link adaptation has been stated in literature as a technique, which can enhance the performance of a single-input multiple-output (SIMO)/MIMO scheme. MBM achieves a high data rate coupled with enhanced system performance. However, to the author's best knowledge, link adaptation has not been investigated with MBM. This motivates us to propose an adaptive algorithm that employs different candidate transmission modes to enhance the reliability of the SIMO system. The proposed scheme is called adaptive SIMOMBM (ASIMOMBM). Lately, two-way cooperative relaying has been proven as a spectral efficient relaying system. This technique employs two or more source nodes, which transmit information to the relay node simultaneously. Considering the advantages of GQSM stated earlier, this motivates us to investigate two-way decode-and-forward relaying for the GQSM scheme to improve the error performance of the conventional GQSM system

Link adaptation for quadrature spatial modulation.

Master of Science in Electrical Engineering. University of KwaZulu-Natal, Durban 2016.Abstract available in PDF file

Index modulation for next generation radio communications.

Masters Degree. University of KwaZulu- Natal, Durban.Man’s insatiable desire for swift and more efficient internet service, a wide range of connectivity and increased data rate of transmission necessitated the need for further research to improve the efficiency of the existing systems. The development and evolution of the next-generation communication systems can be ascribed to the multiple-input multiple-output (MIMO) techniques implemented. The fundamental founding block of the MIMO systems is the spatial modulation (SM) which interestingly was able to attain high spectral efficiency as the receiver maintained significantly lower complexity. However, even with the feat achieved by the SM scheme, there was still a need improve on the performance of the SM scheme which meant an increase in the spectral efficiency was required, this prompted further research and a new scheme was introduced. The quadrature SM (QSM) scheme was introduced to better the performance of the conventional SM. QSM retains all the good benefits the SM scheme offers, while still enhancing the spectral efficiency and improving overall throughput. However, the demand for increased reliability, i.e., improving the QSM scheme’s error performance led to a new scheme being introduced. Space-time QSM (ST-QSM) improves the QSM scheme’s error performance by achieving second-order diversity gain for QSM. This scheme combines both the spatial dimension and diversity to the QSM scheme, bringing about a new and improved scheme. In this dissertation, a scheme was introduced to fix the high computational complexity (CC) that affects MIMO systems transmitting at high data rates. Signal orthogonal projection (OP) was employed to decrease the CC of the space-time block coded spatial modulation (STBC-SM). The proposed scheme is called STBC-SM-OP and its results were investigated by comparing it with the STBC-SM with maximum likelihood detection (STBC-SM-ML). The proposed STBC-SM-OP scheme’s error performance matched that of STBC-SM-ML tightly down to low BER whilst maintaining a low CC

Soft-output detection for transit antenna index modulation-based schemes.

Master of Sciences in Electronic Engineering. University of KwaZulu-Natal, Durban 2016.Abstract available in PDF file