349 research outputs found
Design guidelines for spatial modulation
A new class of low-complexity, yet energyefficient Multiple-Input Multiple-Output (MIMO) transmission techniques, namely the family of Spatial Modulation (SM) aided MIMOs (SM-MIMO) has emerged. These systems are capable of exploiting the spatial dimensions (i.e. the antenna indices) as an additional dimension invoked for transmitting information, apart from the traditional Amplitude and Phase Modulation (APM). SM is capable of efficiently operating in diverse MIMO configurations in the context of future communication systems. It constitutes a promising transmission candidate for large-scale MIMO design and for the indoor optical wireless communication whilst relying on a single-Radio Frequency (RF) chain. Moreover, SM may also be viewed as an entirely new hybrid modulation scheme, which is still in its infancy. This paper aims for providing a general survey of the SM design framework as well as of its intrinsic limits. In particular, we focus our attention on the associated transceiver design, on spatial constellation optimization, on link adaptation techniques, on distributed/ cooperative protocol design issues, and on their meritorious variants
Subcarrier index-power modulated optical OFDM with dual superposition multiplexing for IMDD PON systems
International audienc
Enhanced Huffman Coded OFDM with Index Modulation
In this paper, we propose an enhanced Huffman coded orthogonal
frequency-division multiplexing with index modulation (EHC-OFDM-IM) scheme. The
proposed scheme is capable of utilizing all legitimate subcarrier activation
patterns (SAPs) and adapting the bijective mapping relation between SAPs and
leaves on a given Huffman tree according to channel state information (CSI). As
a result, a dynamic codebook update mechanism is obtained, which can provide
more reliable transmissions. We take the average block error rate (BLER) as the
performance evaluation metric and approximate it in closed form when the
transmit power allocated to each subcarrier is independent of channel states.
Also, we propose two CSI-based power allocation schemes with different
requirements for computational complexity to further improve the error
performance. Subsequently, we carry out numerical simulations to corroborate
the error performance analysis and the proposed dynamic power allocation
schemes. By studying the numerical results, we find that the depth of the
Huffman tree has a significant impact on the error performance when the
SAP-to-leaf mapping relation is optimized based on CSI. Meanwhile, through
numerical results, we also discuss the trade-off between error performance and
data transmission rate and investigate the impacts of imperfect CSI on the
error performance of EHC-OFDM-IM
Multidimensional Index Modulation for 5G and Beyond Wireless Networks
This study examines the flexible utilization of existing IM techniques in a
comprehensive manner to satisfy the challenging and diverse requirements of 5G
and beyond services. After spatial modulation (SM), which transmits information
bits through antenna indices, application of IM to orthogonal frequency
division multiplexing (OFDM) subcarriers has opened the door for the extension
of IM into different dimensions, such as radio frequency (RF) mirrors, time
slots, codes, and dispersion matrices. Recent studies have introduced the
concept of multidimensional IM by various combinations of one-dimensional IM
techniques to provide higher spectral efficiency (SE) and better bit error rate
(BER) performance at the expense of higher transmitter (Tx) and receiver (Rx)
complexity. Despite the ongoing research on the design of new IM techniques and
their implementation challenges, proper use of the available IM techniques to
address different requirements of 5G and beyond networks is an open research
area in the literature. For this reason, we first provide the dimensional-based
categorization of available IM domains and review the existing IM types
regarding this categorization. Then, we develop a framework that investigates
the efficient utilization of these techniques and establishes a link between
the IM schemes and 5G services, namely enhanced mobile broadband (eMBB),
massive machine-type communications (mMTC), and ultra-reliable low-latency
communication (URLLC). Additionally, this work defines key performance
indicators (KPIs) to quantify the advantages and disadvantages of IM techniques
in time, frequency, space, and code dimensions. Finally, future recommendations
are given regarding the design of flexible IM-based communication systems for
5G and beyond wireless networks.Comment: This work has been submitted to Proceedings of the IEEE for possible
publicatio
Modulation options for OFDM-based waveforms: classification, comparison, and future directions
This paper provides a comparative study on the performance of different modulation options
for orthogonal frequency division multiplexing (OFDM) in terms of their spectral efficiency, reliability,
peak-to-average power ratio, power efficiency, out-of-band emission, and computational complexity. The
modulation candidates are classified into two main categories based on the signal plane dimension they
exploit. These categories are: 1) 2-D signal plane category including conventional OFDM with classical
fixed or adaptive QAM modulation and OFDM with differential modulation, where information is conveyed
in changes between two successive symbols in the same subcarrier or between two consecutive subcarriers in
the same OFDM symbol and 2) 3-D signal plane category encompassing: a) index-based OFDM modulation
schemes which include: i) spatial modulation OFDM, where information is sent by the indices of antennas
along with conventional modulated symbols and ii) OFDM with index modulation, where the subcarriers’
indices are used to send additional information; b) number-based OFDM modulation schemes which
include OFDM with subcarrier number modulation, in which number of subcarriers is exploited to convey
additional information; and c) shape-based OFDM modulation schemes which include OFDM with pulse
superposition modulation, where the shape of pulses is introduced as a third new dimension to convey
additional information. Based on the provided comparative study, the relationship and interaction between
these different modulation options and the requirements of future 5G networks are discussed and explained.
This paper is then concluded with some recommendations and future research directions.This work was supported in part by the Scientific and Technological Research Council of Turkey (TUBITAK), under Grant 215E316
Adaptive OFDM Index Modulation for Two-Hop Relay-Assisted Networks
In this paper, we propose an adaptive orthogonal frequency-division
multiplexing (OFDM) index modulation (IM) scheme for two-hop relay networks. In
contrast to the traditional OFDM IM scheme with a deterministic and fixed
mapping scheme, in this proposed adaptive OFDM IM scheme, the mapping schemes
between a bit stream and indices of active subcarriers for the first and second
hops are adaptively selected by a certain criterion. As a result, the active
subcarriers for the same bit stream in the first and second hops can be varied
in order to combat slow frequency-selective fading. In this way, the system
reliability can be enhanced. Additionally, considering the fact that a relay
device is normally a simple node, which may not always be able to perform
mapping scheme selection due to limited processing capability, we also propose
an alternative adaptive methodology in which the mapping scheme selection is
only performed at the source and the relay will simply utilize the selected
mapping scheme without changing it. The analyses of average outage probability,
network capacity and symbol error rate (SER) are given in closed form for
decode-and-forward (DF) relaying networks and are substantiated by numerical
results generated by Monte Carlo simulations.Comment: 30 page
Orthogonal frequency division multiplexing with subcarrier power modulation for doubling the spectral efficiency of 6G and beyond networks
With the emergence of new applications (eg, extended reality [XR] and haptics), which require to be simultaneously served not just with low latency and sufficient reliability, but also with high spectral efficiency, future networks (ie, 6G and beyond) should be capable of meeting this demand by introducing new effective transmission designs. Motivated by this, a novel modulation technique termed as orthogonal frequency division multiplexing with subcarrier power modulation (OFDM-SPM) is proposed for providing highly spectral-efficient data transmission with low-latency and less-complexity for future 6G wireless communication systems. OFDM-SPM utilizes the power of subcarriers in OFDM blocks as a third dimension to convey extra information bits while reducing both complexity and latency compared to conventional schemes. In this article, the concept of OFDM-SPM is introduced and its validity as a future adopted modulation technique is investigated over a wireless multipath Rayleigh fading channel. The proposed system structure is explained, an analytical expression of the bit error rate (BER) is derived, and numerical simulations of BER and throughput performances of OFDM-SPM are carried out. OFDM-SPM is found to greatly enhance the spectral efficiency where it is capable of doubling it. In addition, OFDM-SPM introduces negligible complexity to the system, does not exhibit error propagation, reduces the transmission delay, and decreases the transmission power by half.Türkiye Bilimsel ve Teknolojik Araştirma Kurumu, 119E40
Visible Light Communication (VLC)
Visible light communication (VLC) using light-emitting diodes (LEDs) or laser diodes (LDs) has been envisioned as one of the key enabling technologies for 6G and Internet of Things (IoT) systems, owing to its appealing advantages, including abundant and unregulated spectrum resources, no electromagnetic interference (EMI) radiation and high security. However, despite its many advantages, VLC faces several technical challenges, such as the limited bandwidth and severe nonlinearity of opto-electronic devices, link blockage and user mobility. Therefore, significant efforts are needed from the global VLC community to develop VLC technology further. This Special Issue, “Visible Light Communication (VLC)”, provides an opportunity for global researchers to share their new ideas and cutting-edge techniques to address the above-mentioned challenges. The 16 papers published in this Special Issue represent the fascinating progress of VLC in various contexts, including general indoor and underwater scenarios, and the emerging application of machine learning/artificial intelligence (ML/AI) techniques in VLC
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