1,417 research outputs found
A joint OFDM PAPR reduction and data decoding scheme with no SI estimation
The need for side information (SI) estimation poses a major challenge when selected mapping (SLM) is implemented to reduce peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems. Recent studies on pilot-assisted SI estimation procedures suggest that it is possible to determine the SI without the need for SI transmission. However, SI estimation adds to computational complexity and implementation challenges of practical SLM-OFDM receivers. To address these technical issues, this paper presents the use of a pilot-assisted cluster-based phase modulation and demodulation procedure called embedded coded modulation (ECM). The ECM technique uses a slightly modified SLM approach to reduce PAPR and to enable data recovery with no SI transmission and no SI estimation. In the presence of some non-linear amplifier distortion, it is shown that the ECM method achieves similar data decoding performance as conventional SLM-OFDM receiver that assumed a perfectly known SI and when the SI is estimated using a frequency-domain correlation approach. However, when the number of OFDM subcarriers is small and due to the clustering in ECM, the modified SLM produces a smaller PAPR reduction gain compared with conventional SLM
Single-Carrier Modulation versus OFDM for Millimeter-Wave Wireless MIMO
This paper presents results on the achievable spectral efficiency and on the
energy efficiency for a wireless multiple-input-multiple-output (MIMO) link
operating at millimeter wave frequencies (mmWave) in a typical 5G scenario. Two
different single-carrier modem schemes are considered, i.e., a traditional
modulation scheme with linear equalization at the receiver, and a
single-carrier modulation with cyclic prefix, frequency-domain equalization and
FFT-based processing at the receiver; these two schemes are compared with a
conventional MIMO-OFDM transceiver structure. Our analysis jointly takes into
account the peculiar characteristics of MIMO channels at mmWave frequencies,
the use of hybrid (analog-digital) pre-coding and post-coding beamformers, the
finite cardinality of the modulation structure, and the non-linear behavior of
the transmitter power amplifiers. Our results show that the best performance is
achieved by single-carrier modulation with time-domain equalization, which
exhibits the smallest loss due to the non-linear distortion, and whose
performance can be further improved by using advanced equalization schemes.
Results also confirm that performance gets severely degraded when the link
length exceeds 90-100 meters and the transmit power falls below 0 dBW.Comment: accepted for publication on IEEE Transactions on Communication
Mobile Communications Beyond 52.6 GHz: Waveforms, Numerology, and Phase Noise Challenge
In this article, the first considerations for the 5G New Radio (NR) physical
layer evolution to support beyond 52.6GHz communications are provided. In
addition, the performance of both OFDM based and DFT-s-OFDM based networks are
evaluated with special emphasis on the phase noise (PN) induced distortion. It
is shown that DFT-s-OFDM is more robust against PN under 5G NR Release 15
assumptions, namely regarding the supported phase tracking reference signal
(PTRS) designs, since it enables more effective PN mitigation directly in the
time domain. To further improve the PN compensation capabilities, the PTRS
design for DFT-s-OFDM is revised, while for the OFDM waveform a novel block
PTRS structure is introduced, providing similar link performance as DFT-s-OFDM
with enhanced PTRS design. We demonstrate that the existing 5G NR Release 15
solutions can be extended to support efficient mobile communications at 60GHz
carrier frequency with the enhanced PTRS structures. In addition, DFT-s-OFDM
based downlink for user data could be considered for beyond 52.6GHz
communications to further improve system power efficiency and performance with
higher order modulation and coding schemes. Finally, network link budget and
cell size considerations are provided, showing that at certain bands with
specific transmit power regulation, the cell size can eventually be downlink
limited.Comment: This manuscript has been submitted to IEEE Wireless Communications
Magazine (WCM). 8 pages, 4 figures, and 2 table
MIMO-UFMC Transceiver Schemes for Millimeter Wave Wireless Communications
The UFMC modulation is among the most considered solutions for the
realization of beyond-OFDM air interfaces for future wireless networks. This
paper focuses on the design and analysis of an UFMC transceiver equipped with
multiple antennas and operating at millimeter wave carrier frequencies. The
paper provides the full mathematical model of a MIMO-UFMC transceiver, taking
into account the presence of hybrid analog/digital beamformers at both ends of
the communication links. Then, several detection structures are proposed, both
for the case of single-packet isolated transmission, and for the case of
multiple-packet continuous transmission. In the latter situation, the paper
also considers the case in which no guard time among adjacent packets is
inserted, trading off an increased level of interference with higher values of
spectral efficiency. At the analysis stage, the several considered detection
structures and transmission schemes are compared in terms of bit-error-rate,
root-mean-square-error, and system throughput. The numerical results show that
the proposed transceiver algorithms are effective and that the linear MMSE data
detector is capable of well managing the increased interference brought by the
removal of guard times among consecutive packets, thus yielding throughput
gains of about 10 - 13 . The effect of phase noise at the receiver is also
numerically assessed, and it is shown that the recursive implementation of the
linear MMSE exhibits some degree of robustness against this disturbance
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