SM-MIMO Systems Research Articles

UHDTV 방송을 위한 공간 변조 다중 안테나 시스템 수신 성능 분석

In this paper, the reception performance of spatial modulation multiple-output multiple-input (MIMO) is analyzed for high speed terrestrial broadcasting. The MIMO scheme is required to reduce the inter symbol interference (ISI) and spatial correlation. The spatial modulation scheme solves the problem of ISI, but the spatial correlation degrades the reception performance of SM scheme. The space-time block coded spatial modulation (STBC-SM) is combined the SM system with space-time block code (STBC) for reducing the effects of the spatial correlation. However, the STBC-SM scheme degrades the spectral efficiency by transmitting same data in the two symbol period. The double space-time transmit diversity with spatial modulation (DSTTD-SM) scheme transmits the data with full antenna combination. To adapt these SM MIMO systems into the terrestrial broadcasting system, the reception performance is analyzed using computer simulation in SUI channel environments.

Limited Feedback Precoder Design for Spatial Modulation in MIMO Systems

We investigate the limited feedback precoding for spatial modulation in multiple-input multiple-output systems via using the codebook. To enhance bit error rate, we propose a codebook design which iteratively trains the codebook by two criteria. The first criterion is to partition the training set by assigning the best codeword to each training symbol; the second criterion is to optimize the codewords according to the assigned training symbols. Simulation results show that the proposed codebook design can effectively improve the SM-MIMO systems with small overhead.

Low-Complexity ML Detection for Spatial Modulation MIMO With APSK Constellation

Spatial modulation (SM) is a promising multiple-input–multiple-output (MIMO) transmission technology, which exploits the indexes of the transmit antennas for encoding information into the spatial dimension and, thus, for increasing the transmission rate. Optimal demodulation is realized by using a maximum-likelihood (ML) detector, which jointly estimates the information bits encoded into the transmit antenna indexes and into the transmitted symbol. If a large number of transmit antennas and/or a large modulation size are used; however, the computational complexity of ML demodulation may not be affordable for some applications. Against this background, we propose two novel near-ML but low-complexity detection schemes for SM-MIMO systems, which use $\boldsymbol{M}$ -ary amplitude and phase-shift keying (APSK) digital modulation. The proposed algorithms exploit specific features of the $\boldsymbol{M}$ -ary APSK constellation diagram, in order to avoid searching among all constellation points. It is shown, in particular, that the complexity of the proposed detection schemes is independent of the constellation size and that it only depends on the number of rings that constitute the APSK constellation. Simulation results are also provided, which confirm that the proposed detection schemes provide bit error probability performance close to that of ML demodulation but with lower demodulation complexity.

Generalized Precoder Design Formulation and Iterative Algorithm for Spatial Modulation in MIMO Systems With CSIT

In this paper, we propose two generalized precoder designs to enhance the bit error rates for the general category of spatial modulation (SM) in multiple-input multiple-output (MIMO) systems with channel state information at the transmitter (CSIT). We investigate typical SM-MIMO systems and propose two optimization formulations for designing precoders. Our design rationale for the first formulation is to maximize the minimum Euclidean distance among codewords; for the second formulation, it is to minimize the total signal power for the lower-bounded Euclidean distances among codewords. Since both formulations are non-convex and their optimal solutions are generally intractable, we propose an algorithm that acquires effective solutions by iteratively solving the alternative convex problem linearized and approximated from the original non-convex problem. Discussions on complexity analysis, performance comparisons, design challenges, and robustness in imperfect CSIT are then provided. By generalizing the design formulations, the proposed precoder designs can be extended to generalized SM, which completes the investigation for virtually all SM-type systems. Simulation results show that the proposed designs improve the performance of SM-/GSM-MIMO systems and outperform existing precoding methods with a potentially higher complexity cost.

상관성을 가진 도심무선채널환경에서 공간 변조 기법들의 성능분석

Recently, spatial modulation (SM) schemes are considered to improve the reception performance in spatially correlated channel environments. SM schemes utilize a switching method between multiple transmitters to reduce the correlation among multiple transmitters to reduce the correlation of each received signals and can support transmission additional bits using antenna combinations without extra bandwidth. Therefore, SM schemes can overcome correlation interference of conventional MIMO in urban wireless channels. However, the performance comparisons between SM schemes are not yet performed in correlated urban wireless channels. In this paper, some representative SM schemes are compared and a suitable SM-MIMO system in correlated urban wireless channels is proposed.

On the Error Probability of Spatial Modulation over Keyhole MIMO Channels

The keyhole effect causes a dramatic performance degradation to Multiple-Input Multiple-Output (MIMO) systems. The main contribution of this letter is the analytical performance evaluation of Spatial Modulation MIMO (SM-MIMO) systems over the keyhole channel. The closed-form Pairwise Error Probability (PEP) is derived with accuracy verified by simulations. Based on the PEP, the achievable diversity gain is extracted and shown to be no more than 1 under any configuration. In addition, a tight Average Bit Error Probability (ABEP) upper bound is given. Numerical results demonstrate that compared to independent fading scenarios, the keyhole channel causes a significant performance degradation to the SM-MIMO system. It is shown that SM-MIMO schemes outperforms Space-Time Block Code (STBC) and V-BLAST schemes over the keyhole channel. Therefore, among multiple antenna transmission schemes, SM-MIMO schemes are better choices for systems that may experience the keyhole effect. However, owing to the inherent unfitness of the keyhole channel for multiple antenna transmission, SM-MIMO schemes are still inferior to SISO/SIMO schemes.

Reliability Analysis of Combing Opportunistic Scheduling and Transmit Antenna Selection with Zero-Forcing Receivers in SM-MIMO Systems

In this paper, we propose a novel scheme combing opportunistic schedule (OS) and transmit antenna selection (Tx-AnSS) with ZF receivers under imperfect channel estimation in SM-MIMO systems, where the user set and the transmit antenna subset are adaptively selected according to channel state information (CSI), which is feedback from the receive side. First, we derive the average effective SNR and both analytical forms and approximation expressions for outage probability and BER expression, showing that combining multiuser diversity (MUD) and Tx-AnSS in SM-MIMO systems provides much larger diversity and better performance than the scheme without MUD or Tx-AnSS. Further, the diversity gains for both outage probability and BER expression are also quantified through asymptotic analysis.

Optimization of Switched MIMO Systems Over Rayleigh Fading Channels

This paper proposes a new switched MIMO system where the MIMO includes both diversity-based MIMO and spatial multiplexing MIMO (SM-MIMO). The proposed scheme is a closed-loop system where the feedback bits are sent back to the transmitter to indicate the channel quality. The switching operation is employed among groups of a certain number of transmit antennas. For diversity-based MIMO systems, the switching operation aims to improve the link performance, while the goal of the switching for the SM-MIMO systems is to increase the data rate. The authors analyze and optimize the proposed systems and show that there is considerable benefit in terms of performance and practical use