153 research outputs found
Performance Evaluation of Low Complexity Massive MIMO Techniques for SC-FDE Schemes
Massive-MIMO technology has emerged as a means to achieve 5G's ambitious goals;
mainly to obtain higher capacities and excellent performances without requiring the use of more
spectrum. In this thesis, focused on the uplink direction, we make a study of performance of low
complexity equalization techniques as well as we also approach the impact of the non-linear elements
located on the receivers of a system of this type. For that purpose, we consider a multi-user
uplink scenario through the Single Carrier with Frequency Domain Equalization (SC-FDE)
scheme. This seems to be the most appropriate due to the low energy consumption that it implies,
as well as being less favorable to the detrimental effects of high envelope fluctuations, that is, by
have a low Peak to Average Power Ratio (PAPR) comparing to other similar modulations, such
as the Orthogonal Frequency Division Multiplexing (OFDM). Due to the greater number of antennas
and consequent implementation complexity, the equalization processes for Massive-
MIMO schemes are aspects that should be simplified, that is, they should avoid the inversion of
matrices, contrary to common 4G, with the Zero Forcing (ZF) and Minimum Mean Square Error
(MMSE) techniques. To this end, we use low-complexity techniques, such as the Equal Gain
Combining (EGC) and the Maximum Ratio Combining (MRC). Since these algorithms are not
sufficiently capable of removing the entire Inter-Symbol Interference (ISI) and Inter-User Interference
(IUI), we combine them with iterative techniques, namely with the Iterative Block with
Decision Feedback Equalizer (IB-DFE) to completely remove the residual ISI and IUI. We also
take into account the hardware used in the receivers, since the effects of non-linear distortion can
impact negatively the performance of the system. It is expected a strong performance degradation
associated to the high quantization noise levels when implementing low-resolution Analog to
Digital Converters (ADCs). However, despite these elements with these configurations become
harmful to the performance of the majority of the systems, they are considered a desirable solution
for Massive-MIMO scenarios, because they make their implementation cheaper and more energy
efficient. In this way, we made a study of the impact in the performance by the low-resolution
ADCs. In this thesis we suggest that it is possible to bypass these negative effects by implementing
a number of receiving antennas far superior to the number of transmitting antennas
Performance analysis of massive MIMO receivers
We face now an exponential increase in wireless devices and to allow good user experience, it is imperative that the next generation of mobile (5G) communications
ensures reliable connections, high data transfer rates and low latency.
One way to increase the data transfer rate is to use massive Multiple-Input,
Multiple-Output (MIMO) systems, that is, systems with multiple antennas to emit
and multiple antennas to receive thus allowing spatial diversity. In these systems,
to increase the battery life of the devices it is preferable to use the Single-Carrier
with Frequency-Domain Equalization modulation in the uplink as this modulation
reduces the complexity in the emitter, transferring it to the receiver, in this case
the Base Staion, where it is quite acceptable.
This dissertation studies the performance of massive MIMO receiver systems,
comparing it to the performance achieved with the Matched Filter Bound (MFB).
The Iterative Block Decision-Feedback Equalizer (IB-DFE) receiver presents a
very similar performance to the MFB, however, the algorithm requires matrix
inversions, which in the systems under study, where the size of the matrix is
high, implies an increase of the associated operations increases. Thus it is very
important that low complexity receivers, such as the Maximal-Ratio Combining
(MRC) or Equal Gain Combining are used.
In this dissertation, a simple receiver is proposed combining the IB-DFE receiver with the MRC receiver, thus creating a low complexity receiver with excellent performanceAtualmente, sente-se um aumento exponencial nos dispositivos wireless. De modo
a permitir uma boa experiência por parte dos utilizadores é fundamental que a
próxima geração de comunicações móveis (5G) assegure fiabilidade nas ligações,
uma elevada taxa de transferência de dados e baixa latência.
Uma maneira de elevar a taxa de transferência de dados é utilizar sistemas
massive Multiple-Input, Multiple-Output (MIMO), ou seja, sistemas com múltiplas antenas a emitir e múltiplas antenas a receber permitindo assim diversidade
espacial. Nestes sistemas, para aumentar a bateria dos dispositivos é preferÃvel
usar no uplink a modulação Single-Carrier with Frequency-Domain Equalization
pois esta modulação reduz a complexidade no emissor transferindo-a para o recetor, neste caso na Base Station, onde isso é bastante aceitável.
Esta dissertação estuda o desempenho dos recetores dos sistemas massive
MIMO, comparando o desempenho alcançado com o desempenho do Matched
Filter Bound (MFB). O recetor Iterative Block Decision-Feedback Equalizer (IBDFE) apresenta um desempenho muito semelhante ao do MFB no entanto, o
algoritmo do receptor inverte matrizes, o que nos sistemas em estudo, onde o
tamanho das matrizes é elevado, se reflecte no aumento da complexidade das operações associadas. Deste modo, é importante que sejam utilizados recetores de
baixa complexidade tal como o Maximal-Ratio Combining (MRC) ou o Equal Gain
Combining.
Esta dissertação propõe um recetor simples que combina um recetor IB-DFE
com um recetor MRC, criando desde modo um recetor de baixa complexidade e
com excelente desempenho
On the Performance of LDPC-Coded MIMO Schemes for Underwater Communications Using 5G-like Processing
UIDB/EEA/50008/2020This article studies the underwater acoustic (UWA) communications associated with multiple input–multiple output (MIMO), single carrier with frequency-domain equalization (SC-FDE), and with low-density parity-check (LDPC) codes. Low-complexity receivers such as equal gain combining (EGC), maximum ratio combining (MRC), and iterative block—decision feedback equalization (IB-DFE) are studied in the above-described scenarios. Furthermore, due to the low carrier frequencies utilized in UWA communications, the performance of the proposed MIMO scenarios is studied at different levels of channel correlation between antennas. This article shows that the combined schemes tend to achieve good performances while presenting low complexity, even in scenarios with channel correlation between antennas.publishersversionpublishe
On the Performance of LDPC-Coded MIMO Schemes for Underwater Communications Using 5G-like Processing
6F1A-06CB-E82D | Mário Pedro Guerreiro Marques da SilvaN/
Low complexity detection for SC-FDE massive MIMO systems
Nowadays we continue to observe a big and fast growth of wireless com-munication usage due to the increasing number of access points, and fields of application of this technology. Furthermore, these new usages can require higher speed and better quality of service in order to create market. As example we can have: live 4K video transmission, M2M (Machine to Machine communication), IoT (Internet of Things), Tactile Internet, between many others.
As a consequence of all these factors, the spectrum is getting overloaded with communications, increasing the interference and affecting the system's per-formance. Therefore a different path of ideas has been followed and the commu-nication process has been taken to the next level in 5G by the usage of big arrays of antennas and multi-stream communication (MIMO systems) which in a greater scale are called massive MIMO schemes. These systems can be combined with an SC-FDE (Single-Carrier Frequency Domain Equalization) scheme to im-prove the power efficiency due to the low envelope fluctuations.
This thesis focused on the equalization in massive MIMO systems, more specifically in the FDE (Frequency Domain Equalization), studying the perfor-mance of different approaches, namely ZF (Zero Forcing), EGD (Equal Gain De-tector), MRD (Maximum Ratio Detector), IB-DFE (Iterative Block Decision Feed-back Equalizer) and a proposed receiver combining MRD (or EGD) and IB-DFE.With this approach we want to minimize the ICI (Inter Carrier Interference) in order to have almost independent data streams and to produce a low complexity code, so that the receiver's performance doesn't affect the total system's perfor-mance, with a final objective of increasing the data throughput in a great scale
A Low Complexity Channel Estimation and Detection for Massive MIMO Using SC-FDE
5G Communications will support millimeter waves (mm-Wave), alongside the conventional
centimeter waves, which will enable much higher throughputs and facilitate the employment of
hundreds or thousands of antenna elements, commonly referred to as massive Multiple Input–Multiple
Output (MIMO) systems. This article proposes and studies an efficient low complexity receiver that
jointly performs channel estimation based on superimposed pilots, and data detection, optimized for
massive MIMO (m-MIMO). Superimposed pilots suppress the overheads associated with channel
estimation based on conventional pilot symbols, which tends to be more demanding in the case of
m-MIMO, leading to a reduction in spectral efficiency. On the other hand, MIMO systems tend to
be associated with an increase of complexity and increase of signal processing, with an exponential
increase with the number of transmit and receive antennas. A reduction of complexity is obtained
with the use of the two proposed algorithms. These algorithms reduce the complexity but present
the disadvantage that they generate a certain level of interference. In this article, we consider an
iterative receiver that performs the channel estimation using superimposed pilots and data detection,
while mitigating the interference associated with the proposed algorithms, leading to a performance
very close to that obtained with conventional pilots, but without the corresponding loss in the
spectral efficiency.6F1A-06CB-E82D | Mário Pedro Guerreiro Marques da SilvaN/
Analytical performance evaluation of massive MIMO techniques for SC-FDE modulations
SAICT-45-2017-02
UIDB/EEA/50008/2020In the Fifth Generation of telecommunications networks (5G), it is possible to use massive Multiple Input Multiple Output (MIMO) systems, which require efficient receivers capable of reaching good performance values. MIMO systems can also be extended to massive MIMO (mMIMO) systems, while maintaining their, sometimes exceptional, performance. However, we must be aware that this implies an increase in the receiver complexity. Therefore, the use of mMIMO in 5G and future generations of mobile receivers will only be feasible if they use very efficient algorithms, so as to maintain their excellent performance, while coping with increasing and critical user demands. Having this in mind, this paper presents and compares three types of receivers used in MIMO systems, for further use with mMIMO systems, which use Single-Carrier with Frequency-Domain Equalization (SC-FDE), Iterative Block Decision Feedback Equalization (IB-DFE) and Maximum Ratio Combining (MRC) techniques. This paper presents and compares the theoretical and simulated performance values for these receivers in terms of their Bit Error Rate (BER) and correlation factor. While one of the receivers studied in this paper achieves a BER performance nearly matching the Matched Filter Bound (MFB), the other receivers (IB-DFE and MRC) are more than 1 dB away from MFB. The results obtained in this paper can help the development of ongoing research involving hybrid analog/digital receivers for 5G and future generations of mobile communications.publishersversionpublishe
A Tutorial
Funding Information: This work is funded by FCT/MCTES through national funds and when applicable co-funded EU funds under the projects UIDB/EEA/50008/2020 and 2022.03897.PTDC. Funding Information: We acknowledge the support of FCT/MCTES, as described above in funding. We also acknowledge the support of Autonoma TechLab for providing an interesting environment to carry out this research. Publisher Copyright: © 2022 by the authors.This is a tutorial on current techniques that use a huge number of antennas in intelligent reflecting surfaces (IRS), large intelligent surfaces (LIS), and radio stripes (RS), highlighting the similarities, differences, advantages, and drawbacks. A comparison between IRS, LIS, and RS is performed in terms of the implementation and capabilities, in the form of a tutorial. We begin by introducing the IRS, LIS, and RS as promising technologies for 6 G wireless technology. Then, we will look at how the three notions are applied in wireless networks. We discuss various performance indicators and methodologies for characterizing and improving the performance of IRS, LIS, and RS-assisted wireless networks. We cover rate maximization, power consumption reduction, and cost implementation concerns in order to take advantage of the performance increase. Furthermore, we extend the discussion to some cases of emerging use. In the description of the three concepts, IRS-assisted communication was introduced as a passive system, considering the capacity/data rate, with power optimization being an advantage, while channel estimation was a challenge. LIS is an active component that goes beyond massive MIMO; a recent study found that channel estimation issues in IRS had improved. In comparison to IRS, capacity enhancement is a highlight, and user interference showed a trend of decreasing. However, power consumption due to utilizing power amplifiers has restrictions. The third technique for increasing coverage is cell-free massive MIMO with RS, with easy deployment in communication network structures. It is demonstrated to have suitable energy efficiency and power consumption. Finally, for future work, we further propose expanding the conversation to include some cases of new uses, such as complexity reduction; design and simulation with LDPC code could be a solution to decreasing complexity.publishersversionpublishe
On the Performance of LDPC-Coded MIMO Schemes for Underwater Communications Using 5G-like Processing
6F1A-06CB-E82D | Mário Pedro Guerreiro Marques da Silvainfo:eu-repo/semantics/publishedVersio
Efficient frequency-domain detection for massive MIMO systems
Reduced-complexity implementations are critical for massive MIMO (Multiple Input, Multiple Output) systems. In this paper we consider the uplink of broadband massive MIMO systems employing SC-FDE (Single-Carrier with Frequency-Domain Equalization) schemes, where multiple users transmit to a single base station with a large number of antennas. We propose low-complexity frequency-domain detection schemes that allow excellent performance, but do not require matrix inversions.info:eu-repo/semantics/acceptedVersio
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