Index Modulation Techniques for 5G Wireless Networks (1604.08315v1)

Abstract: The increasing demand for higher data rates, better quality of service, fully mobile and connected wireless networks lead the researchers to seek new solutions beyond 4G wireless systems. It is anticipated that 5G wireless networks, which are expected to be introduced around 2020, will achieve ten times higher spectral and energy efficiency than current 4G wireless networks and will support data rates up to 10 Gbps for low mobility users. The ambitious goals set for 5G wireless networks require dramatic changes in the design of different layers for next generation communications systems. Massive multiple-input multiple-output (MIMO) systems, filter bank multi-carrier (FBMC) modulation, relaying technologies, and millimeter-wave communications have been considered as some of the strong candidates for the physical layer design of 5G networks. In this article, we shed light on the potential and implementation of index modulation (IM) techniques for MIMO and multi-carrier communications systems which are expected to be two of the key technologies for 5G systems. Specifically, we focus on two promising applications of IM: spatial modulation (SM) and orthogonal frequency division multiplexing with IM (OFDM-IM), and we discuss the recent advances and future research directions in IM technologies towards spectral and energy-efficient 5G wireless networks.

• The paper’s main finding is that index modulation techniques can significantly improve spectral and energy efficiency in 5G wireless networks.
• It explores spatial modulation and OFDM-IM methods, demonstrating how system indices are used to convey additional information with reduced complexity.
• The study highlights potential enhancements in 5G design, paving the way for future research integrating IM with massive MIMO and cooperative communications.

Index Modulation Techniques for 5G Wireless Networks

The paper, authored by Ertugrul Basar, provides a comprehensive examination of index modulation (IM) techniques for 5G wireless networks, focusing on their potential to enhance spectral and energy efficiency. The need for these advancements arises from the ambitious goals of 5G networks, which aim to achieve significantly higher efficiency compared to existing 4G systems and support data rates up to 10 Gbps.

Index Modulation Overview

Index modulation (IM) is explored primarily in two applications: spatial modulation (SM) and orthogonal frequency division multiplexing with index modulation (OFDM-IM). Both approaches utilize the indices of system building blocks to convey additional information, thus improving spectral efficiency without dramatically increasing system complexity.

Spatial Modulation Techniques

Spatial modulation (SM) employs the indices of transmit antennas of a MIMO system for information transmission, alongside traditional $M$-ary signal constellations. This method efficiently uses spatial resources and reduces complexity, allowing a single RF chain to transmit data, thereby minimizing inter-antenna synchronization issues and inter-channel interference.

Recent advances also focus on generalized and enhanced variants of SM, such as generalized SM (GSM) and enhanced SM (ESM), which improve spectral efficiency and adapt to various system architectures, including massive MIMO and cooperative systems. These methods demonstrate an advantageous complexity-performance trade-off, positioning them as promising candidates for future wireless communication systems.

OFDM with Index Modulation

OFDM-IM adds an innovative layer to conventional OFDM by employing subcarrier indices as information carriers. This dual utilization of subcarriers enhances spectral efficiency and can outperform traditional OFDM under certain conditions, particularly in systems requiring adaptable configurations given spectral efficiency constraints.

Recent research into OFDM-IM includes generalized and MIMO-based approaches, exploring how these can further benefit from index modulation. The focus is on balancing error performance and system complexity, with IM's flexibility making it a strong contender for various 5G applications, including M2M communications.

Implications and Future Directions

The implications of these IM techniques are significant for next-generation wireless networks. They enable a high degree of flexibility in system design, allowing configurations that meet specific spectral and energy efficiency requirements. As research progresses, integrating IM with massive MU-MIMO systems and cooperative communication scenarios remains a critical avenue for exploration. Additionally, practical implementation studies will be crucial to ensure these theoretical benefits translate into real-world performance improvements.

Future research should aim to develop novel IM schemes that further optimize efficiency and explore their potential in diverse application environments typical of 5G networks. This paper provides a foundational understanding for ongoing research and development towards achieving the ambitious goals set for future communication systems.