91 research outputs found
Efficient Fast-Convolution-Based Waveform Processing for 5G Physical Layer
This paper investigates the application of fast-convolution (FC) filtering
schemes for flexible and effective waveform generation and processing in the
fifth generation (5G) systems. FC-based filtering is presented as a generic
multimode waveform processing engine while, following the progress of 5G new
radio standardization in the Third-Generation Partnership Project, the main
focus is on efficient generation and processing of subband-filtered cyclic
prefix orthogonal frequency-division multiplexing (CP-OFDM) signals. First, a
matrix model for analyzing FC filter processing responses is presented and used
for designing optimized multiplexing of filtered groups of CP-OFDM physical
resource blocks (PRBs) in a spectrally well-localized manner, i.e., with narrow
guardbands. Subband filtering is able to suppress interference leakage between
adjacent subbands, thus supporting independent waveform parametrization and
different numerologies for different groups of PRBs, as well as asynchronous
multiuser operation in uplink. These are central ingredients in the 5G waveform
developments, particularly at sub-6-GHz bands. The FC filter optimization
criterion is passband error vector magnitude minimization subject to a given
subband band-limitation constraint. Optimized designs with different guardband
widths, PRB group sizes, and essential design parameters are compared in terms
of interference levels and implementation complexity. Finally, extensive coded
5G radio link simulation results are presented to compare the proposed approach
with other subband-filtered CP-OFDM schemes and time-domain windowing methods,
considering cases with different numerologies or asynchronous transmissions in
adjacent subbands. Also the feasibility of using independent transmitter and
receiver processing for CP-OFDM spectrum control is demonstrated
Generalized Fast-Convolution-based Filtered-OFDM: Techniques and Application to 5G New Radio
This paper proposes a generalized model and methods for fast-convolution
(FC)-based waveform generation and processing with specific applications to
fifth generation new radio (5G-NR). Following the progress of 5G-NR
standardization in 3rd generation partnership project (3GPP), the main focus is
on subband-filtered cyclic prefix (CP) orthogonal frequency-division
multiplexing (OFDM) processing with specific emphasis on spectrally well
localized transmitter processing. Subband filtering is able to suppress the
interference leakage between adjacent subbands, thus supporting different
numerologies for so-called bandwidth parts as well as asynchronous multiple
access. The proposed generalized FC scheme effectively combines overlapped
block processing with time- and frequency-domain windowing to provide highly
selective subband filtering with very low intrinsic interference level. Jointly
optimized multi-window designs with different allocation sizes and design
parameters are compared in terms of interference levels and implementation
complexity. The proposed methods are shown to clearly outperform the existing
state-of-the-art windowing and filtering-based methods.Comment: To appear in IEEE Transactions on Signal Processin
Interference analysis and power allocation in the presence of mixed numerologies
The flexibility in supporting heterogeneous services with vastly different technical requirements is one of the distinguishing characteristics of the fifth generation (5G) communication systems and beyond. One viable solution is to divide the system bandwidth into several bandwidth parts (BWPs), each having a distinct numerology optimized for a particular service. However, multiplexing of mixed numerologies over a unified physical infrastructure comes at the cost of induced interference. In this paper, we develop an analytical system model for inter-numerology interference (InterNI) analysis in orthogonal frequency-division multiplexing (OFDM) systems with and without filter processing in the presence of mixed numerologies. With the analytical model, the level of InterNI is quantified by the developed analytical metric, which is expressed as a function of several system parameters. This leads to an analysis and evaluation of these parameters for meeting a given distortion target. Moreover, a case study on power allocation utilizing the derived analysis is presented, where an optimization problem of maximizing the sum rate is formulated, and a solution is also provided. It is also demonstrated that a filtered-OFDM system better accommodates the coexistence of mixed numerologies. The proposed model provides an accurate analytical guidance for the multi-service design in 5G and beyond systems
System-level assessment of a C-RAN based on generalized space–frequency index modulation for 5G new radio and beyond
Index modulation (IM) has been attracting considerable research efforts in recent years as it is considered a promising technology that can enhance spectral and energy efficiency and help cope with the rising demand of mobile traffic in future wireless networks. In this paper, we propose a cloud radio access network (C-RAN) suitable for fifth-generation (5G) and beyond systems, where the base stations (BSs) and access points (APs) transmit multidimensional IM symbols, which we refer to as precoding-aided transmitter-side generalized space–frequency IM (PT-GSFIM). The adopted PT-GSFIM approach is an alternative multiuser multiple-input multiple-output (MU-MIMO) scheme that avoids multiuser interference (MUI) while exploiting the inherent diversity in frequency-selective channels. To validate the potential gains of the proposed PT-GSFIM-based C-RAN, a thorough system-level assessment is presented for three different three-dimensional scenarios taken from standardized 5G New Radio (5G NR), using two different numerologies and frequency ranges. Throughput performance results indicate that the 28 GHz band in spite of its higher bandwidth and higher achieved throughput presents lower spectral efficiency (SE). The 3.5 GHz band having lower bandwidth and lower achieved throughput attains higher SE. Overall, the results indicate that a C-RAN based on the proposed PT-GSFIM scheme clearly outperforms both generalized spatial modulation (GSM) and conventional MU-MIMO, exploiting its additional inherent frequency diversity.info:eu-repo/semantics/publishedVersio
Frequency-Domain Signal Processing for Spectrally-Enhanced CP-OFDM Waveforms in 5G New Radio
Orthogonal frequency-division multiplexing (OFDM) has been selected as the
basis for the fifth-generation new radio (5G-NR) waveform developments.
However, effective signal processing tools are needed for enhancing the OFDM
spectrum in various advanced transmission scenarios. In earlier work, we have
shown that fast-convolution (FC) processing is a very flexible and efficient
tool for filtered-OFDM signal generation and receiver-side subband filtering,
e.g., for the mixed-numerology scenarios of the 5G-NR. FC filtering
approximates linear convolution through effective fast Fourier transform
(FFT)-based circular convolutions using partly overlapping processing blocks.
However, with the continuous overlap-and-save and overlap-and-add processing
models with fixed block-size and fixed overlap, the FC-processing blocks cannot
be aligned with all OFDM symbols of a transmission frame. Furthermore, 5G-NR
numerology does not allow to use transform lengths shorter than 128 because
this would lead to non-integer cyclic prefix (CP) lengths. In this article, we
present new FC-processing schemes which solve the mentioned limitations. These
schemes are based on dynamically adjusting the overlap periods and
extrapolating the CP samples, which make it possible to align the FC blocks
with each OFDM symbol, even in case of variable CP lengths. This reduces
complexity and latency, e.g., in mini-slot transmissions and, as an example,
allows to use 16-point transforms in case of a 12-subcarrier-wide subband
allocation, greatly reducing the implementation complexity. On the receiver
side, the proposed scheme makes it possible to effectively combine cascaded
inverse and forward FFT units in FC-filtered OFDM processing. Transform
decomposition is used to simplify these computations. Very extensive set of
numerical results is also provided, in terms of radio-link performance and
associated processing complexity.Comment: This work has been submitted to the IEEE Transactions on Wireless
Communications for possible publication. Copyright may be transferred without
notice, after which this version may no longer be accessibl
NR V2X Communications at Millimeter Waves: An End-to-End Performance Evaluation
3GPP NR V2X represents the new 3GPP standard for next-generation vehicular
systems which, among other innovations, supports vehicle-to-vehicle (V2V)
operations in the millimeter wave (mmWave) spectrum to address the
communication requirements of future intelligent automotive networks. While
mmWaves will enable massive data rates and low latency, the propagation
characteristics at very high frequencies become very challenging, thereby
calling for accurate performance evaluations as a means to properly assess the
performance of such systems. Along these lines, in this paper MilliCar, the new
ns-3 module based on the latest NR V2X specifications, is used to provide an
end-to-end performance evaluation of mmWave V2V networks. We investigate the
impact of different propagation scenarios and system parameters, including the
inter-vehicle distance, the adopted frame numerology, and the modulation and
coding scheme, and provide guidelines towards the most promising V2V deployment
configurations.Comment: 6 pages, 7 figures. Submitted to IEEE Globecom 202
5G New Radio Evolution Towards Sub-THz Communications
In this paper, the potential of extending 5G New Radio physical layer
solutions to support communications in sub-THz frequencies is studied. More
specifically, we introduce the status of third generation partnership project
studies related to operation on frequencies beyond 52.6 GHz and note also the
recent proposal on spectrum horizons provided by federal communications
commission (FCC) related to experimental licenses on 95 GHz - 3 THz frequency
band. Then, we review the power amplifier (PA) efficiency and output power
challenge together with the increased phase noise (PN) distortion effect in
terms of the supported waveforms. As a practical example on the waveform and
numerology design from the perspective of the PN robustness, link performance
results using 90 GHz carrier frequency are provided. The numerical results
demonstrate that new, higher subcarrier spacings are required to support high
throughput, which requires larger changes in the physical layer design. It is
also observed that new phase-tracking reference signal designs are required to
make the system robust against PN. The results illustrate that single-carrier
frequency division multiple access is significantly more robust against PN and
can provide clearly larger PA output power than cyclic-prefix orthogonal
frequency division multiplexing, and is therefore a highly potential waveform
for sub-THz communications.Comment: This manuscript has been accepted for publication to IEEE 6G Wireless
Summit 2020, 6 pages, 4 figure
- …