1,711 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
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
Near-Instantaneously Adaptive HSDPA-Style OFDM Versus MC-CDMA Transceivers for WIFI, WIMAX, and Next-Generation Cellular Systems
Burts-by-burst (BbB) adaptive high-speed downlink packet access (HSDPA) style multicarrier systems are reviewed, identifying their most critical design aspects. These systems exhibit numerous attractive features, rendering them eminently eligible for employment in next-generation wireless systems. It is argued that BbB-adaptive or symbol-by-symbol adaptive orthogonal frequency division multiplex (OFDM) modems counteract the near instantaneous channel quality variations and hence attain an increased throughput or robustness in comparison to their fixed-mode counterparts. Although they act quite differently, various diversity techniques, such as Rake receivers and space-time block coding (STBC) are also capable of mitigating the channel quality variations in their effort to reduce the bit error ratio (BER), provided that the individual antenna elements experience independent fading. By contrast, in the presence of correlated fading imposed by shadowing or time-variant multiuser interference, the benefits of space-time coding erode and it is unrealistic to expect that a fixed-mode space-time coded system remains capable of maintaining a near-constant BER
OFDMA/SC-FDMA aided space-time shift keying for dispersive multi-user scenarios
Motivated by the recent concept of Space-Time Shift Keying (STSK) developed for achieving a flexible diversity versus multiplexing gain trade-off, we propose a novel Orthogonal Frequency Division Multiple Access (OFDMA)/Single Carrier Frequency Division Multiple Access (SC-FDMA) aided multi-user STSK scheme for frequency-selective channels. The proposed OFDMA/SC-FDMA STSK scheme is capable of providing an improved performance in dispersive channels, while supporting multiple users in a multiple antenna aided wireless system. Furthermore, the scheme has the inherent potential of benefitting from the low-complexity single-stream Maximum-likelihood (ML) detector. Both an uncoded and a sophisticated near-capacity coded OFDMA/SC-FDMA STSK scheme were studied and their performances were compared in multiuser wideband Multiple-Input Multiple-Output (MIMO) scenarios. Explicitly, OFDMA/SC-FDMA aided STSK exhibits an excellent performance even in the presence of channel impairments due to the frequency-selectivity of wideband channels and proves to be a beneficial choice for high capacity multi-user MIMO systems
Layered Steered Space–Time-Spreading-Aided Generalized MC DS-CDMA
Abstract—We present a novel trifunctional multiple-input– multiple-output (MIMO) scheme that intrinsically amalgamates space–time spreading (STS) to achieve a diversity gain and a Vertical Bell Labs layered space–time (V-BLAST) scheme to attain a multiplexing gain in the context of generalized multicarrier direct-sequence code-division multiple access (MC DS-CDMA), as well as beamforming. Furthermore, the proposed system employs both time- and frequency-domain spreading to increase the number of users, which is also combined with a user-grouping technique to reduce the effects of multiuser interference
Performance Analysis of a 5G Transceiver Implementation for Remote Areas Scenarios
The fifth generation of mobile communication networks will support a large
set of new services and applications. One important use case is the remote area
coverage for broadband Internet access. This use case ha significant social and
economic impact, since a considerable percentage of the global population
living in low populated area does not have Internet access and the
communication infrastructure in rural areas can be used to improve agribusiness
productivity. The aim of this paper is to analyze the performance of a 5G for
Remote Areas transceiver, implemented on field programmable gate array based
hardware for real-time processing. This transceiver employs the latest digital
communication techniques, such as generalized frequency division multiplexing
waveform combined with 2 by 2 multiple-input multiple-output diversity scheme
and polar channel coding. The performance of the prototype is evaluated
regarding its out-of-band emissions and bit error rate under AWGN channel.Comment: Presented in 2018 European Conference on Networks and Communications
(EuCNC),18-21 June, 2018, Ljubljana, Sloveni
Flexible Multi-Group Single-Carrier Modulation: Optimal Subcarrier Grouping and Rate Maximization
Orthogonal frequency division multiplexing (OFDM) and single-carrier
frequency domain equalization (SC-FDE) are two commonly adopted modulation
schemes for frequency-selective channels. Compared to SC-FDE, OFDM generally
achieves higher data rate, but at the cost of higher transmit signal
peak-to-average power ratio (PAPR) that leads to lower power amplifier
efficiency. This paper proposes a new modulation scheme, called flexible
multi-group single-carrier (FMG-SC), which encapsulates both OFDM and SC-FDE as
special cases, thus achieving more flexible rate-PAPR trade-offs between them.
Specifically, a set of frequency subcarriers are flexibly divided into
orthogonal groups based on their channel gains, and SC-FDE is applied over each
of the groups to send different data streams in parallel. We aim to maximize
the achievable sum-rate of all groups by optimizing the subcarrier-group
mapping. We propose two low-complexity subcarrier grouping methods and show via
simulation that they perform very close to the optimal grouping by exhaustive
search. Simulation results also show the effectiveness of the proposed FMG-SC
modulation scheme with optimized subcarrier grouping in improving the rate-PAPR
trade-off over conventional OFDM and SC-FDE.Comment: Submitted for possible conference publicatio
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