A virtual MIMO dual-hop architecture based on hybrid spatial modulation

International audienceIn this paper, we propose a novel Virtual Multiple-Input-Multiple-Output (VMIMO) architecture based on the concept of Spatial Modulation (SM). Using a dual-hop and Decode-and-Forward protocol, we form a distributed system, called Dual-Hop Hybrid SM (DH-HSM). DH-HSM conveys information from a Source Node (SN) to a Destination Node (DN) via multiple Relay Nodes (RNs). The spatial position of the RNs is exploited for transferring information in addition to, or even without, a conventional symbol. In order to increase the performance of our architecture, while keeping the complexity of the RNs and DN low, we employ linear precoding using Channel State Information (CSI) at the SN. In this way, we form a Receive-Spatial Modulation (R-SM) pattern from the SN to the RNs, which is able to employ a centralized coordinated or a distributed uncoordinated detection algorithm at the RNs. In addition, we focus on the SN and propose two regularized linear precoding methods that employ realistic Imperfect Channel State Information at the Transmitter. The power of each precoder is analyzed theoretically. Using the Bit Error Rate (BER) metric, we evaluate our architecture against the following benchmark systems: 1) single relay; 2) best relay selection; 3) distributed Space Time Block Coding (STBC) VMIMO scheme; and 4) the direct communication link. We show that DH-HSM is able to achieve significant Signal-to-Noise Ratio (SNR) gains, which can be as high as 10.5 dB for a very large scale system setup. In order to verify our simulation results, we provide an analytical framework for the evaluation of the Average Bit Error Probability (ABEP)

Improving the Performance of Space Shift Keying (SSK) Modulation via Opportunistic Power Allocation

International audienceIn this Letter, we show that the performance of Space Shift Keying (SSK) modulation can be improved via opportunistic power allocation methods. For analytical tractability, we focus on a 2×1 Multiple-Input–Multiple–Output (MIMO) system setup over correlated Rayleigh fading channels. A closed–form solution of the optimal power allocation problem is derived, and it is shown that the transmit–power of each transmit–antenna should be chosen as a function of the power imbalance ratio and correlation coefficient of the transmit–receive wireless links. Numerical results are shown to substantiate the analytical derivation and the claimed performance improvement

Bit Error Probability of Space Modulation over Nakagami-m Fading: Asymptotic Analysis

International audienceRecently, the Average Bit Error Probability (ABEP) of Space Shift Keying (SSK) and Spatial Modulation (SM) over Nakagami-m fading has been computed as a single integral involving the Meijer-G function. Even though the frameworks are very accurate, the use of special functions hides some fundamental properties of the aforementioned new modulation schemes, e.g., coding and diversity gains. In this Letter, we exploit a notable limit involving the Meijer-G function near the singular point −1, and provide a simple, closed-form, and asymptotically tight upper-bound of the ABEP. The result is applicable to SM and SSK modulation, to correlated Nakagami-m fading, and to general Multiple-Input Multiple-Output (MIMO) wireless systems. As a case study, numerical examples showing the accuracy for SSK modulation are given, and it is proved that, unlike conventional modulations, the diversity gain is independent of the fading severity m

Space Shift Keying (SSK) Modulation With Partial Channel State Information: Optimal Detector and Performance Analysis Over Fading Channels

International audienceSpace Shift Keying (SSK) modulation is a new and recently proposed transmission technology for Multiple–Input–Multiple–Output (MIMO) wireless systems, which has been shown to be a promising low–complexity alternative to several state–of–the–art MIMO schemes. So far, only optimal or heuristic transceivers with Full Channel State Information (F–CSI) at the receiver have been investigated, and their performance analyzed over fading channels. In this paper, we develop and study the performance of the optimal Maximum–Likelihood (ML) detector with unknown phase reference at the receiver (i.e., Partial–CSI, P–CSI, knowledge). A very accurate analytical framework for the analysis and optimization of this novel detector over generically correlated and non–identically distributed Nakagami–m fading channels is proposed, and its performance compared to the optimal receiver design with F–CSI. Numerical results will point out that: i) the performance of SSK modulation is significantly affected by the characteristics of fading channels, e.g., channel correlation, fading severity, and, particularly, power imbalance among the transmit–receive wireless links, and ii) unlike ordinary modulation schemes, there is a substantial performance loss when the receiver cannot exploit the phase information for optimal receiver design. This latter result highlights the importance of accurate and reliable channel estimation mechanisms for the efficient operation of SSK modulation over fading channels. Analytical frameworks and theoretical findings will also be substantiated via Monte Carlo simulations

A General Framework for Performance Analysis of Space Shift Keying (SSK) Modulation for MISO Correlated Nakagami-m Fading Channels

International audienceIn this paper, we offer an accurate framework for analyzing the performance of wireless communication systems adopting the recently proposed Space Shift Keying (SSK) modulation scheme. More specifically, we study the performance of a Nt×1 MISO (Multiple–Input–Single–Output) system setup with Maximum–Likelihood (ML) detection and full Channel State Information (CSI) at the receiver. The exact Average Bit Error Probability (ABEP) over generically correlated and non–identically distributed Nakagami–m fading channels is computed in closed–form when Nt=2, while very accurate and asymptotically tight upper bounds are proposed to compute the ABEP when Nt>2. With respect to current literature, our contribution is threefold: i) the ABEP is computed in closed–form without resorting to Monte Carlo numerical simulations, which, besides being computationally intensive, only yield limited insights about the system performance and cannot be exploited for a systematic optimization of it, ii) the framework accounts for arbitrary fading conditions and is not restricted to identically distributed fading channels, thus offering a comprehensive under standing of the performance of SSK modulation over generalized fading channels, and iii) the analytical framework could be readily adapted to study the performance over generalized fading channels with arbitrary fading distributions, since the Nakagami–m distribution is a very flexible fading model, which either includes or can closely approximate several other fading models. Numerical results show that the performance of SSK modulation is significantly affected by the characteristics of fading channels, e.g., channel correlation, fading severity, and power imbalance among the Nt transmit–receive wireless links. Analytical frameworks and theoretical findings are also substantiated via Monte Carlo simulations

On the Performance of SSK Modulation over Multiple-Access Rayleigh Fading Channels”, IEEE Global Communications Conference

International audienceSpatial Modulation (SM) is a recently proposed joint coding and modulation scheme for Multiple–Input-Multiple–Output (MIMO) wireless systems, which is receiving a growing interest. SM offers a low-complexity alternative to the design of MIMO wireless systems, which avoids multiple Radio Frequency (RF) chains at the transmitter and high–complexity interference cancelation algorithms at the receiver, but still guarantees a multiplexing gain that only depends on the number of antennas at the transmitter. This makes this technology especially suitable for the downlink with low–complexity mobile units. So far, the feasibility and performance of SM have been assessed and studied only for point–to–point communication systems, i.e., the single–user scenario. However, the performance achievable by the vast majority of wireless communication networks is interference limited, due to the simultaneous transmission of various users over the same physical wireless channel. Therefore, the adoption of SM in the next generation of wireless communication systems requires a deep understanding of its performance over interference channels. Motivated by this consideration, in this paper we study the performance of SM over the reference multiple–access fading channel composed by two transmitters and one receiver. Two detectors at the receiver are studied, i.e., the single– and the multi–user detector. In particular, analysis and Monte Carlo simulations show that the single–user detector does not offer, in general, good error performance for arbitrary channel conditions, while the multi–user detector achieves error performance very close to the single–user lower–bound. These results clearly highlight that SM can be adopted for enabling data transmission over multiple–access fading channels as well

Spatial Modulation with Partial-CSI at the Receiver: Optimal Detector and Performance Evaluation

International audienceSpatial Modulation (SM) is a novel and recently proposed transmission technology for Multiple–Input–Multiple–Output (MIMO) wireless communication systems, which has been shown to be a promising alternative to several popular MIMO schemes. So far, only optimal or heuristic transceivers with Full Channel State Information (F–CSI) at the receiver have been investigated, and their performance analyzed over fading channels. However, in several circumstances, channel fading might be sufficiently rapid to preclude the availability of the perfect knowledge of CSI at the receiver, and, in particular, the estimation of a stable phase reference. Motivated by this consideration, in this paper we develop the optimal detector for SM with unknown phase reference at the receiver (i.e., Partial–CSI, P–CSI, knowledge), which inevitably leads to a sub–optimal receiver design. An analytical framework will be developed for the accurate performance analysis of this novel detector over fading channels, and its performance will be compared to the optimal receiver design with F–CSI. Numerical results will point out that, unlike ordinary modulation schemes, there is a substantial performance loss when the receiver cannot exploit the phase information for optimal detection operations. This result highlights the importance of accurate and reliable channel estimation mechanisms for the efficient operation of SM over fading channels. Analytical frameworks and theoretical findings will also be substantiated via Monte Carlo simulations

Space Shift Keying (SSK-) MIMO over Correlated Rician Fading Channels: Performance Analysis and a New Method for Transmit-Diversity

International audienceIn this paper, we study the performance of Space Shift Keying (SSK) modulation for a generic Multiple-Input-Multiple-Output (MIMO) wireless system over correlated Rician fading channels. In particular, our contribution is twofold, i) First, we propose a very general framework for computing the Average Bit Error Probability (ABEP) of SSK-MIMO systems over a generic Rician fading channel with arbitrary correlation and channel parameters. The framework relies upon the Moschopoulos method. We show that it is exact for MIMO systems with two transmit-antenna and arbitrary receive-antenna, while an asymptotically-tight upper-bound is proposed to handle the system setup with an arbitrary number of transmit-antenna. ii) Second, moving from the consideration that conventional SSK-MIMO schemes can offer only receive-diversity gains, we propose a novel SSK-MIMO scheme that can exploit the transmit-antenna to increase the diversity order. The new method has its basic foundation on the transmission of signals with good time-correlation properties, and is called Time-Orthogonal-Signal-Design (TOSD-) assisted SSK modulation (TOSD-SSK). It is shown that the proposed method can increase twofold the diversity order for arbitrary transmit- and receive-antenna. In particular, for MIMO systems with two transmit-antenna and Nr receive-antenna full-diversity equal to 2Nr can be achieved. Analytical frameworks and theoretical findings are substantiated via Monte Carlo simulations for various system setups

Bit Error Probability of Spatial Modulation (SM-) MIMO over Generalized Fading Channels

International audienceIn this paper, we study the performance of Spatial Modulation (SM-) Multiple-Input-Multiple-Output (MIMO) wireless systems over generic fading channels. More precisely, a comprehensive analytical framework to compute the Average Bit Error Probability (ABEP) is introduced, which can be used for any MIMO setups, for arbitrary correlated fading channels, and for generic modulation schemes. It is shown that, when compared to state-of-the-art literature, our framework: i) has more general applicability over generalized fading channels; ii) is, in general, more accurate as it exploits an improved union-bound method; and, iii) more importantly, clearly highlights interesting fundamental trends about the performance of SM, which are difficult to capture with available frameworks. For example, by focusing on the canonical reference scenario with independent and identically distributed (i.i.d.) Rayleigh fading, we introduce very simple formulas which yield insightful design information on the optimal modulation scheme to be used for the signal- constellation diagram, as well as highlight the different role played by the bit mapping on the signal- and spatial-constellation diagrams. Numerical results show that, for many MIMO setups, SM with Phase Shift Keying (PSK) modulation outperforms SM with Quadrature Amplitude Modulation (QAM), which is a result never reported in the literature. Also, by exploiting asymptotic analysis, closed-form formulas of the performance gain of SM over other single-antenna transmission technologies are provided. Numerical results show that SM can outperform many single-antenna systems, and that for any transmission rate there is an optimal allocation of the information bits onto spatial- and signal-constellation diagrams. Furthermore, by focusing on the Nakagami-m fading scenario with generically correlated fading, we show that the fading severity plays a very important role in determining the diversity gain of SM. In particular, the performance gain over single-antenna systems increases for fading channels less severe than Rayleigh fading, while it gets smaller for more severe fading channels. Also, it is shown that the impact of fading correlation at the transmitter is reduced for less severe fading. Finally, analytical frameworks and claims are substantiated through extensive Monte Carlo simulations

Spatial Modulation for Multiple-Antenna Wireless Systems : A Survey

International audienceMultiple-antenna techniques constitute a key technology for modern wireless communications, which trade-off superior error performance and higher data rates for increased system complexity and cost. Among the many transmission principles that exploit multiple-antenna at either the transmitter, the receiver, or both, Spatial Modulation (SM) is a novel and recently proposed multiple- uniqueness and randomness properties of the wireless channel for communication. This is achieved by adopting a simple but effective coding mechanism that establishes a one-to-one mapping between blocks of information bits to be transmitted and the spatial positions of the transmit-antenna in the antenna-array. In this article, we summarize the latest research achievements and outline some relevant open research issues of this recently proposed transmission technique