113 research outputs found
Architectures and Key Technical Challenges for 5G Systems Incorporating Satellites
Satellite Communication systems are a promising solution to extend and
complement terrestrial networks in unserved or under-served areas. This aspect
is reflected by recent commercial and standardisation endeavours. In
particular, 3GPP recently initiated a Study Item for New Radio-based, i.e., 5G,
Non-Terrestrial Networks aimed at deploying satellite systems either as a
stand-alone solution or as an integration to terrestrial networks in mobile
broadband and machine-type communication scenarios. However, typical satellite
channel impairments, as large path losses, delays, and Doppler shifts, pose
severe challenges to the realisation of a satellite-based NR network. In this
paper, based on the architecture options currently being discussed in the
standardisation fora, we discuss and assess the impact of the satellite channel
characteristics on the physical and Medium Access Control layers, both in terms
of transmitted waveforms and procedures for enhanced Mobile BroadBand (eMBB)
and NarrowBand-Internet of Things (NB-IoT) applications. The proposed analysis
shows that the main technical challenges are related to the PHY/MAC procedures,
in particular Random Access (RA), Timing Advance (TA), and Hybrid Automatic
Repeat reQuest (HARQ) and, depending on the considered service and
architecture, different solutions are proposed.Comment: Submitted to Transactions on Vehicular Technologies, April 201
Mixed-numerology signals transmission and interference cancellation for radio access network slicing
A clear understanding of mixed-numerology signals multiplexing and isolation in the physical layer is of importance to enable spectrum efficient radio access network (RAN) slicing, where the available access resource is divided into slices to cater to services/users with optimal individual design. In this paper, a RAN slicing framework is proposed and systematically analyzed from a physical layer perspective. According to the baseband and radio frequency (RF) configurations imparities among slices, we categorize four scenarios and elaborate on the numerology relationships of slices configurations. By considering the most generic scenario, system models are established for both uplink and downlink transmissions. Besides, a low out of band emission (OoBE) waveform is implemented in the system for the sake of signal isolation and inter-service/slice-band-interference (ISBI) mitigation. We propose two theorems as the basis of algorithms design in the established system, which generalize the original circular convolution property of discrete Fourier transform (DFT). Moreover, ISBI cancellation algorithms are proposed based on a collaboration detection scheme, where joint slices signal models are implemented. The framework proposed in the paper establishes a foundation to underpin extremely diverse user cases in 5G that implement on a common infrastructure
Cellular, Wide-Area, and Non-Terrestrial IoT: A Survey on 5G Advances and the Road Towards 6G
The next wave of wireless technologies is proliferating in connecting things
among themselves as well as to humans. In the era of the Internet of things
(IoT), billions of sensors, machines, vehicles, drones, and robots will be
connected, making the world around us smarter. The IoT will encompass devices
that must wirelessly communicate a diverse set of data gathered from the
environment for myriad new applications. The ultimate goal is to extract
insights from this data and develop solutions that improve quality of life and
generate new revenue. Providing large-scale, long-lasting, reliable, and near
real-time connectivity is the major challenge in enabling a smart connected
world. This paper provides a comprehensive survey on existing and emerging
communication solutions for serving IoT applications in the context of
cellular, wide-area, as well as non-terrestrial networks. Specifically,
wireless technology enhancements for providing IoT access in fifth-generation
(5G) and beyond cellular networks, and communication networks over the
unlicensed spectrum are presented. Aligned with the main key performance
indicators of 5G and beyond 5G networks, we investigate solutions and standards
that enable energy efficiency, reliability, low latency, and scalability
(connection density) of current and future IoT networks. The solutions include
grant-free access and channel coding for short-packet communications,
non-orthogonal multiple access, and on-device intelligence. Further, a vision
of new paradigm shifts in communication networks in the 2030s is provided, and
the integration of the associated new technologies like artificial
intelligence, non-terrestrial networks, and new spectra is elaborated. Finally,
future research directions toward beyond 5G IoT networks are pointed out.Comment: Submitted for review to IEEE CS&
Narrowband Internet of Things (NB-IoT) and LTE Systems Co-existence Analysis
In this paper, we establish a comprehensive uplink system model for in-band and guard-band Narrowband Internet of Things (NB-IoT) with arbitrary sample duration in the NB-IoT device. The mathematical expressions of received LTE and NB-IoT signals are derived. Moreover, the close-form interference power on the LTE signal from the adjacent NB-IoT signal is given analytically. The result shows that the sample duration of NB-IoT device has significant impact on its desired signal and on the interference to the LTE user equipment (UE). Numerical results show that the analytical expressions match the simulated ones perfectly, which verifies the effectiveness of proposed system model and derivations. The work in this paper provides a valid guidance for NB-IoT system deployment and co-existence analysis
Mixed-numerology for radio access network slicing
Network slicing is a sustainable solution to support the various service types in future networks. In general, network slicing is composed of core network slicing and radio access network (RAN) slicing. The former can be realized by allocating dedicated virtualized core network functionalities to specific slices. Similarly, RAN slicing includes the virtualization and allocation of the limited RAN resources. From the physical layer perspective, supporting RAN slicing implies the need of unique radio-frequency (RF) and baseband (BB) configurations, i.e., numerology, for each slice to fulfil its quality of service requirements. To support such a heterogeneous mixed-numerology (MN) system, the transceiver architecture and widely used signal processing algorithms in the traditional single-service system need to be significantly changed. A clear understanding of mixed-numerology signals multiplexing and isolation is of importance to enable spectrum and computation efficient RAN slicing. Meanwhile, an effective channel estimation is the guarantee of performing almost all receiver signal processing. Fundamental channel estimation investigations also constitute a crucial piece of MN study.
This thesis aims to systematically investigate the OFDM-based MN wireless communication systems in terms of system modeling, channel equalization/ estimation, and power allocation. First, a comprehensive mixed-numerology framework with two numerologies is proposed and characterized by physical layer parameters. According to the BB and RF configurations imparities among numerologies, four scenarios are categorized and elaborated on the configuration relationships of different numerologies. System models considering the most generic scenario are established for both uplink and downlink transmissions. Two theorems are proposed as the basis of MN algorithms design, which generalize the original circular convolution property of the discrete Fourier transform. The proposed theorems verifies the feasibility of the one-tap channel equalization in MN systems. However, they also indicate that both BB and RF configuration differences result in inter-numerology-interference (INI). Besides, severe signal distortion may occur when the transmitter and receiver numerologies are different. Therefore, a pre-coding algorithm is designed by utilizing the theorems to compensate the system degradation resulting from the signal distortion. INI cancellation algorithms are proposed based on collaboration detection scheme and joint numerologies signal models for downlink and uplink, respectively. Numerical results shows that the proposed algorithms are able to significantly improve the system performance.
Another objective of this thesis is to verify the effectiveness of the existing channel estimation algorithms and to develop new ones in the presence of MN. To achieve these goals, three channel estimation methods, i.e., least-square linear interpolation, least-square ‘sinc’ interpolation, and minimum mean square error ‘sinc’ interpolation are implemented and theoretically analyzed in both single-user and multi-user scenarios. The analysis reveals that the pilot signal to noise ratio, pilot distance, and position of pilot signals jointly affect the channel estimation. In particular, a signal distortion factor caused by the RF configuration difference is spotted to seriously affect the channel estimation performance, whose values are mainly decided by the degree of configuration mismatch. On the other hand, INI also degrades the channel estimation in the MN system. The existence of interference-free subcarriers is demonstrated based on the derived closed-form expression of the INI. Pilot design principles in terms of pilot signal placement are developed according to the analyses. Numerical results shows that minimum mean square error based channel estimation has the best performance and robustness to the configuration mismatch. In addition, the proposed pilot design principles could produce comparable channel estimation results with the legacy OFDM systems where no INI and signal distortion exist.
The two problems associated with the MN system, i.e., signal distortion and INI, could negatively affect the power distribution of the received MN signals, and the system performance in terms of spectrum efficiency may be seriously degraded. Consequently, it becomes outstandingly important to introduce an efficient subcarrier-level power allocation scheme in such kinds of systems to counter the performance degradation caused by the configuration mismatch. As such, this thesis makes the attempt to extend the two-numerology model to contain ‘M’ different numerologies. Based on the model, closed-form expressions of desired signal, interference, and noise are derived. The derivation shows that interference generated from different numeroloies are linearly superimposed in the frequency domain. The distribution of signal-to-interference-plus-noiseratio (SINR) is analyzed theoretically. An iterative convex approximation power allocation algorithm is proposed by applying the derived SINR. Results show that the power allocation algorithm contributes to remarkable spectrum efficiency improvement compare to the other schemes, and an extra subband filtering process could bring about even higher performance.
The work presented in this thesis provides guidance for multi-numerology system design in terms of parameter selection, and the frame structure and algorithms design. Moreover, it presents a solution as to how the radio access network slicing can be underpinned in the physical layer in a spectrum efficient way
Multitone NB-IoT optimization based on filtered OFDM waveform
Narrowband Internet of Things (NB-IoT) is standardized by 3GPP as a novel radio-access scheme for next-generation IoT technology. In-band operation mode, as one of its deployment methods, shares the spectrum of LTE. To avoid interference leakage on adjacent resource blocks (RBs), the spectrum sharing system needs a spectrally well-localized waveform. In this thesis, we investigate filtered-OFDM waveform for NB-IoT in-band system. This is achieved by designing and exploiting optimized filter for each sub-band. Specifically, the optimum filter needs a suitable length, a relatively narrowed transition band, and adequate stopband attenuation, which efficiently reduces the required guard-band, minimizing the related overhead in resource usage.
In the experiments, we simplify the system model by shifting the NB-IoT RB to the center of the LTE spectrum. Firstly, we test potential filter types with various transition bands, selecting suitable filter configurations with acceptable performance when the system operates under carrier frequency offset (CFO) of half subcarrier spacing. Then, we define two different power level test cases, which are based on the minimum SNR for 1% uncoded bit-error rate (BER), for examining NB-IoT and LTE error tolerance in asynchronous cases, when NB-IoT system fails to synchronize to the time-frequency alignment of LTE. Finally, the system performance in a multipath channel is evaluated. With filtered-OFDM, the out-of-band emission is suppressed effectively and the tolerance to time and frequency offset is significantly improved, which makes the proposed scheme suitable for supporting asynchronous NB-IoT operation
Spectrally and Energy Efficient Wireless Communications: Signal and System Design, Mathematical Modelling and Optimisation
This thesis explores engineering studies and designs aiming to meeting the requirements of enhancing capacity and energy efficiency for next generation communication networks. Challenges of spectrum scarcity and energy constraints are addressed and new technologies are proposed, analytically investigated and examined.
The thesis commences by reviewing studies on spectrally and energy-efficient techniques, with a special focus on non-orthogonal multicarrier modulation, particularly spectrally efficient frequency division multiplexing (SEFDM). Rigorous theoretical and mathematical modelling studies of SEFDM are presented. Moreover, to address the potential application of SEFDM under the 5th generation new radio (5G NR) heterogeneous numerologies, simulation-based studies of SEFDM coexisting with orthogonal frequency division multiplexing (OFDM) are conducted. New signal formats and corresponding transceiver structure are designed, using a Hilbert transform filter pair for shaping pulses. Detailed modelling and numerical investigations show that the proposed signal doubles spectral efficiency without performance degradation, with studies of two signal formats; uncoded narrow-band internet of things (NB-IoT) signals and unframed turbo coded multi-carrier signals. The thesis also considers using constellation shaping techniques and SEFDM for capacity enhancement in 5G system. Probabilistic shaping for SEFDM is proposed and modelled to show both transmission energy reduction and bandwidth saving with advantageous flexibility for data rate adaptation. Expanding on constellation shaping to improve performance further, a comparative study of multidimensional modulation techniques is carried out. A four-dimensional signal, with better noise immunity is investigated, for which metaheuristic optimisation algorithms are studied, developed, and conducted to optimise bit-to-symbol mapping. Finally, a specially designed machine learning technique for signal and system design in physical layer communications is proposed, utilising the application of autoencoder-based end-to-end learning. Multidimensional signal modulation with multidimensional constellation shaping is proposed and optimised by using machine learning techniques, demonstrating significant improvement in spectral and energy efficiencies
Modelaçcão comportamental da camada física NB-IoT - Uplink
Mestrado em Engenharia Eletrónica e TelecomunicaçõesA Internet das Coisas (IoT) consiste numa rede sem fios de sensores/atuadores
ligados entre si e que têm a capacidade de recolher dados. Devido
ao crescimento rápido do mercado IoT, as redes de longa distância e baixa
potência (LPWAN) tornaram-se populares. O NarrowBand-IoT (NB-IoT),
desenvolvido pela 3rd Generation Partnership Project (3GPP), é um desses
protocolos.
O principal objectivo desta dissertação é a implementação de uma simulação
comportamental em MATLAB do NB-IoT no uplink, que será disponibilizada
abertamente. Esta será focada, primariamente, na camada física e nas
suas respetivas funcionalidades, nomeadamente turbo coding, modulação
SC-FDMA, modelos de simulação de canal, desmodulação SC-FDMA, estimação de canal, equalizador e turbo decoding. A estimação de canal é
feita usando símbolos piloto previamente conhecidos. Os modelos de canal
utilizados são baseados nas especificações oficiais da 3GPP.
A taxa de bits errados (BER) é calculada e usada de forma a avaliar a performance
do turbo encoder e do equalizador zero forcing (ZF). Serve também
como comparação quando a implementação usa esquemas de modulação
diferentes (Binary Phase-Shift Keying (BPSK) e Quadrature Phase-Shift
Keying (QPSK)). Além disso, os sinais gerados em MATLAB são transmitidos
usando como front-end de radio-frequência (RF) uma Universal
Software Radio Peripheral (USRP). Posteriormente, são recebidos, desmodulados
e descodificados. Finalmente, é obtida a constelação do sinal, a BER
é calculada e os resultados são analisados.The Internet of Things (IoT) refers to a wireless network of interconnected
sensors/actuators with data-collecting technologies. Low Power Wide Area
Networks (LPWAN) have become popular due to the rapid growth of the
IoT market. Narrowband-IoT (NB-IoT), developed by 3rd Generation Partnership
Project (3GPP), is one of these protocols.
The main objective of this thesis is the implementation of an open-source uplink
behavioral simulator based on MATLAB. Its focus is primarily on Layer 1
(physical layer) relevant functionalities, namely turbo coding, Single-Carrier
Frequency-Division Multiple Access (SC-FDMA) modulation, channel modeling,
SC-FDMA demodulation, channel estimation, equalization and turbo
decoding. Channel estimation is performed using known pilot symbols. The
used channel models are based on the 3GPP o cial release specs.
The Bit Error Rate (BER) is calculated in order to evaluate the turbo encoder
and the Zero Forcing (ZF) equalizer performance, and to compare
Binary Phase-Shift Keying (BPSK) and Quadrature Phase-Shift Keying
(QPSK) implementations. Furthermore, the MATLAB generated signal is
transmitted using a radio-frequency (RF) front-end consisting of an Universal
Software Radio Peripheral (USRP). Afterwards, the signal is received,
demodulated and decoded. A constellation is obtained, the BER is calculated
and the results are analyzed
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