251 research outputs found
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
Waveform Design for 5G and Beyond
5G is envisioned to improve major key performance indicators (KPIs), such as
peak data rate, spectral efficiency, power consumption, complexity, connection
density, latency, and mobility. This chapter aims to provide a complete picture
of the ongoing 5G waveform discussions and overviews the major candidates. It
provides a brief description of the waveform and reveals the 5G use cases and
waveform design requirements. The chapter presents the main features of cyclic
prefix-orthogonal frequency-division multiplexing (CP-OFDM) that is deployed in
4G LTE systems. CP-OFDM is the baseline of the 5G waveform discussions since
the performance of a new waveform is usually compared with it. The chapter
examines the essential characteristics of the major waveform candidates along
with the related advantages and disadvantages. It summarizes and compares the
key features of different waveforms.Comment: 22 pages, 21 figures, 2 tables; accepted version (The URL for the
final version:
https://onlinelibrary.wiley.com/doi/abs/10.1002/9781119333142.ch2
Coherent Optical DFT-Spread OFDM
We consider application of the discrete Fourier transform-spread orthogonal
frequency-division multiplexing (DFT-spread OFDM) technique to high-speed fiber
optic communications. The DFT-spread OFDM is a form of single-carrier technique
that possesses almost all advantages of the multicarrier OFDM technique (such
as high spectral efficiency, flexible bandwidth allocation, low sampling rate
and low-complexity equalization). In particular, we consider the optical
DFT-spread OFDM system with polarization division multiplexing (PDM) that
employs a tone-by-tone linear minimum mean square error (MMSE) equalizer. We
show that such a system offers a much lower peak-to-average power ratio (PAPR)
performance as well as better bit error rate (BER) performance compared with
the optical OFDM system that employs amplitude clipping.Comment: This idea was originally submitted at Nov. 28th, 2009. After many
times of rejection and resubmission, it was finally accepted by the journal
of Advances in Optical Technologie
On the system performance of DFT-S-OFDM and CP-OFDM for 5G Uplink in mmWave band
Both conventional Cyclic Prefix Orthogonal Frequency Division Multiplexing (CP-OFDM) and Discrete Fourier Transform Spread OFDM (DFT-S-OFDM) have been adopted for their use in the Physical Uplink Shared Channel (PUSCH) in the 5G New Radio (NR) standard. While CP-OFDM can better exploit the frequency characteristics of the channel, DFTS-OFDM has the advantage of a lower peak-to-average power ratio (PAPR). Due to the interactions between PAPR and power amplifier (PA) non-linearity, users adopting DFT-S-OFDM waveform may benefit from a potentially higher PA efficiency and extend their coverage by increasing their transmit power. In this paper we study the uplink performance of both waveforms and their interaction with non-linear PA and uplink power control in the millimeter-wave (mmWave) band to determine their optimal operational range
Time-frequency warped waveforms for well-contained massive machine type communications
This paper proposes a novel time-frequency warped waveform for short symbols, massive machine-type communication (mMTC), and internet of things (IoT) applications. The waveform is composed of asymmetric raised cosine (RC) pulses to increase the signal containment in time and frequency domains. The waveform has low power tails in the time domain, hence better performance in the presence of delay spread and time offsets. The time-axis warping unitary transform is applied to control the waveform occupancy in time-frequency space and to compensate for the usage of high roll-off factor pulses at the symbol edges. The paper explains a step-by-step analysis for determining the roll-off factors profile and the warping functions. Gains are presented over the conventional Zero-tail Discrete Fourier Transform-spread-Orthogonal Frequency Division Multiplexing (ZT-DFT-s-OFDM), and Cyclic prefix (CP) DFT-s-OFDM schemes in the simulations section.United States Department of Energy (DOE) ; Office of Advanced Scientific Computing Research ; National Science Foundation (NSF
Sparse orthogonal circulant transform multiplexing for coherent optical fiber communication
This paper introduces a new multicarrier system, named sparse orthogonal circulant transform multiplexing (S-OCTM), for optical fiber communication. This technique uses an inverse sparse orthogonal circulant transform (S-OCT) matrix, which is simple and contains only two nonzero elements in each column, to multiplex information of different subcarriers. We compared the proposed scheme with conventional orthogonal frequency division multiplexing (OFDM), orthogonal chirp division multiplexing (OCDM), and discrete-Fourier-transform spreading OFDM (DFT-S-OFDM) in a coherent optical communication system. It is shown that S-OCTM, while exhibiting the complexity among the least, avoids the performance disadvantages of all investigated conventional schemes. It is theoretically proved that the S-OCT matrix equalizes the bandwidth limitation effect that degrades the performance of conventional OFDM. It also shows a greatly reduced peak-to-average power ratio and higher tolerance to fiber nonlinearity than OFDM and OCDM. On the other hand, compared to DFT-S-OFDM, S-OCTM shows a better dispersion tolerance under insufficient length of cyclic prefix and is more tolerable to strong optical filtering. The performance advantages and low complexity enable the proposed scheme to be a promising multicarrier solution for optical communications
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