3,031 research outputs found
Sparse Reconstruction-based Detection of Spatial Dimension Holes in Cognitive Radio Networks
In this paper, we investigate a spectrum sensing algorithm for detecting
spatial dimension holes in Multiple Inputs Multiple Outputs (MIMO)
transmissions for OFDM systems using Compressive Sensing (CS) tools. This
extends the energy detector to allow for detecting transmission opportunities
even if the band is already energy filled. We show that the task described
above is not performed efficiently by regular MIMO decoders (such as MMSE
decoder) due to possible sparsity in the transmit signal. Since CS
reconstruction tools take into account the sparsity order of the signal, they
are more efficient in detecting the activity of the users. Building on
successful activity detection by the CS detector, we show that the use of a
CS-aided MMSE decoders yields better performance rather than using either
CS-based or MMSE decoders separately. Simulations are conducted to verify the
gains from using CS detector for Primary user activity detection and the
performance gain in using CS-aided MMSE decoders for decoding the PU
information for future relaying.Comment: accepted for PIMRC 201
Power saving and optimal hybrid precoding in millimeter wave massive MIMO systems for 5G
The proliferation of wireless services emerging from use cases offifth-generation(5G) technology is posing many challenges on cellular communicationinfrastructure. They demand to connect a massive number of devices withenhanced data rates. The massive multiple-input multiple-output (MIMO)technology at millimeter-wave (mmWave) in combination with hybrid precodingemerges as a concrete tool to address the requirements of 5G networkdevelopments. But Massive MIMO systems consume significant power fornetwork operations. Hence the prior role is to improve the energy efficiency byreducing the power consumption. This paper presents the power optimizationmodels for massive MIMO systems considering perfect channel state information(CSI) and imperfect CSI. Further, this work proposes an optimal hybrid precodingsolution named extended simultaneous orthogonal matchingpursuit (ESOMP).Simulation results reveal that a constant sum-rate can be achieved in massiveMIMO systems while significantly reducing the power consumption. Theproposed extended SOMPhybrid precoder performsclose to the conventionaldigital beamforming method. Further, modulation schemes compatible withmassive MIMO systems are outlined and their bit error rate (BER) performance isinvestigate
Dispensing with channel estimation: differentially modulated cooperative wireless communications
As a benefit of bypassing the potentially excessive complexity and yet inaccurate channel estimation, differentially encoded modulation in conjunction with low-complexity noncoherent detection constitutes a viable candidate for user-cooperative systems, where estimating all the links by the relays is unrealistic. In order to stimulate further research on differentially modulated cooperative systems, a number of fundamental challenges encountered in their practical implementations are addressed, including the time-variant-channel-induced performance erosion, flexible cooperative protocol designs, resource allocation as well as its high-spectral-efficiency transceiver design. Our investigations demonstrate the quantitative benefits of cooperative wireless networks both from a pure capacity perspective as well as from a practical system design perspective
A generalized space-frequency index modulation scheme for downlink MIMO transmissions with improved diversity
Multidimensional Index Modulations (IM) are a novel alternative to conventional modulations which can bring considerable benefits for future wireless networks. Within this scope, in this paper we present a new scheme, named as Precoding-aided Transmitter side Generalized Space-Frequency Index Modulation (PT-GSFIM), where part of the information bits select the active antennas and subcarriers which then carry amplitude and phase modulated symbols. The proposed scheme is designed for multiuser multiple-input multiple-output (MU-MIMO) scenarios and incorporates a precoder which removes multiuser interference (MUI) at the receivers. Furthermore, the proposed PT-GSFIM also integrates signal space diversity (SSD) techniques for tackling the typical poor performance of uncoded orthogonal frequency division multiplexing (OFDM) based schemes. By combining complex rotation matrices (CRM) and subcarrier-level interleaving, PT-GSFIM can exploit the inherent diversity in frequency selective channels and improve the performance without additional power or bandwidth. To support reliable detection of the multidimensional PT-GSFIM we also propose three different detection algorithms which can provide different tradeoffs between performance and complexity. Simulation results shows that proposed PT-GSFIM scheme, can provide significant gains over conventional MU-MIMO and GSM schemes.info:eu-repo/semantics/publishedVersio
Orthogonal Time Frequency Space for Integrated Sensing and Communication: A Survey
Sixth-generation (6G) wireless communication systems, as stated in the
European 6G flagship project Hexa-X, are anticipated to feature the integration
of intelligence, communication, sensing, positioning, and computation. An
important aspect of this integration is integrated sensing and communication
(ISAC), in which the same waveform is used for both systems both sensing and
communication, to address the challenge of spectrum scarcity. Recently, the
orthogonal time frequency space (OTFS) waveform has been proposed to address
OFDM's limitations due to the high Doppler spread in some future wireless
communication systems. In this paper, we review existing OTFS waveforms for
ISAC systems and provide some insights into future research. Firstly, we
introduce the basic principles and a system model of OTFS and provide a
foundational understanding of this innovative technology's core concepts and
architecture. Subsequently, we present an overview of OTFS-based ISAC system
frameworks. We provide a comprehensive review of recent research developments
and the current state of the art in the field of OTFS-assisted ISAC systems to
gain a thorough understanding of the current landscape and advancements.
Furthermore, we perform a thorough comparison between OTFS-enabled ISAC
operations and traditional OFDM, highlighting the distinctive advantages of
OTFS, especially in high Doppler spread scenarios. Subsequently, we address the
primary challenges facing OTFS-based ISAC systems, identifying potential
limitations and drawbacks. Then, finally, we suggest future research
directions, aiming to inspire further innovation in the 6G wireless
communication landscape
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