- The paper introduces spatial modulation as an innovative method that encodes data using antenna indices, reducing RF chain complexity in MIMO systems.
- It details key variants such as GSM, QSM, and DSM and explores their integration with techniques like compressed sensing and NOMA to boost performance.
- The paper highlights practical applications in mmWave and Visible Light Communications while addressing challenges like antenna switching constraints and phase noise.
A Survey on Spatial Modulation in Emerging Wireless Systems: Research Progresses and Applications
Spatial Modulation (SM) presents itself as an innovative modulation technique in digital communication, emphasizing the trade-off between spectral and energy efficiency while maintaining a simplified design. Unlike conventional approaches that rely on multiple RF chains for MIMO systems, SM harnesses the ON/OFF states of transmit antennas to encode additional information, potentially reducing system complexity and cost.
The paper provides an extensive review of the advancements and state-of-the-art methodologies associated with SM. Initially, SM's foundational concepts are discussed, highlighting its unique mechanism of employing antenna indices to convey information, which alone can enhance the spectral efficiency without necessitating extra RF chains. This fundamental approach underwent significant theoretical and experimental developments leading to several variants such as Generalized Spatial Modulation (GSM), Quadrature Spatial Modulation (QSM), and Differential Spatial Modulation (DSM). Each variant introduces modifications aimed at improving system adaptability, performance in different channel conditions, and reducing detection complexity.
The survey further explores the integration of SM with other cutting-edge techniques like compressed sensing (CS), non-orthogonal multiple access (NOMA), and massive MIMO. CS emerges as a solution to detect SM symbols in large-scale systems efficiently, capitalizing on their inherent sparsity. Meanwhile, the amalgamation of SM with NOMA is particularly significant in addressing inter-user interference and enhancing spectral efficiency in dense network environments.
Practical applications of SM stretch across various emerging communication paradigms, including millimeter-wave (mmWave) communications, where SM helps mitigate hardware cost by reducing the number of necessary RF chains in transceivers. Similarly, Visible Light Communication (VLC) systems benefit from SM by leveraging fast-switching LEDs for data modulation without compromising illumination.
An intriguing direction is the transposition of SM concepts into other domains, such as frequency and time, creating new modulation schemas like OFDM-IM and time-domain IM. These extensions reveal the flexibility of the SM framework to optimize resource utilization across multiple dimensions.
From a practical standpoint, SM's applicability is occasionally hindered by limitations imposed by hardware constraints, such as antenna switching times and phase noise. Addressing these challenges in real-world deployments requires innovative solutions, as highlighted through practical experiments and prototype development showcased in the paper.
Overall, the surveyed content underlines SM's pivotal role in future communication systems, addressing key challenges such as crowded spectra and energy scarcity while ensuring scalability for massive IoT deployments. Future research should aim to refine SM's integration in dynamic and dense environments, explore its synergy with emerging technologies like AI-driven smart antennas, and further reduce operational complexity for seamless real-world adoption.