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Introduction
Robson D. Vieira is at Ektrum, a technology company focused on delivering high-quality concepts.
Additional affiliations
April 2016 - November 2017
Ektrum
Position
- Executive
August 2014 - December 2015
January 2006 - December 2010
Publications
Publications (83)
In this paper, we present the results of short-range path loss measurement in the microwave and millimeter wave bands, at frequencies between 27 and 40 GHz, obtained in a campaign inside a university campus in Rio de Janeiro, Brazil. Existing empirical path loss prediction models, including the alpha-beta-gamma (ABG) model and the close-in free spa...
In this paper, we present the results of short-range path loss measurements in the microwave and millimetre wave bands, at frequencies between 27 and 40 GHz, obtained in a campaign inside a university campus in Rio de Janeiro, Brazil. Existing empirical path loss prediction models, including the alpha-beta-gamma (ABG) model and the close-in free sp...
In this paper, we present the results of short-range path loss measurement in the microwave and millimetre wave bands, at frequencies between 27 and 40 GHz, obtained in a campaign inside a university campus in Rio de Janeiro, Brazil. Existing empirical path loss prediction models, including the alpha-beta-gamma (ABG) model and the close-in free spa...
High-Altitude Platform Systems (HAPS) are being studied as a viable, easy to deploy and to maintain technology to provide isolated areas with connectivity. They can be integrated to existing cellular networks and have a wide coverage area, presenting a lower cost than satellite systems. The deployment of HAPS, however, demands that country administ...
In this paper, we investigate the suitability of the propagation models ITU-R 526, Okumura Hata, COST Hata models and Standard Propagation Model (SPM) to predict the path loss in open-pit mines. The models are evaluated by comparing the predicted data with measurements obtained in two operational iron-ore mining complexes in Brazil. Additionally, a...
This paper presents a cm-Wave measurement-based analysis of the path loss and a comparison with the SUI propagation model and the M.2135 and P.1411 ITU-R recommendations. These models were previously applied to mm-Wave measurements in the USA and Japan and it is probably the first analysis when considering cm-Wave measurements in Brazil. The measur...
The introduction of a high number of small cells in cellular networks and the complementary adoption of WLAN technologies in unlicensed spectrum are interesting options to attend the increasing demand for Internet traffic in wireless broadband access networks. One alternative for integrating both solutions is the aggregation of ISM unlicensed spect...
5G will play a pivotal role in the digitization of the industrial sector and is expected to make the best use of every bit of spectrum available. In this light, this paper presents the results of an extensive measurement campaign in two iron-ore open-pit mining complexes, at the 700 MHz and 2.6 GHz bands, considering macro and small cell deployment...
Unlicensed spectrum is increasingly being used by mobile operators to meet the mobile traffic demand, and Wi-Fi is foreseen as one of the technologies for implementing mobile traffic offloading. However, Wi-Fi efficiency does not scale well as node density increases, and IEEE 802.11ax Task Group (TGax) was created in 2014 for developing Wi-Fi techn...
In this paper we present the results of an extensive measurement campaign performed at two large iron ore mining centers in Brazil at the 2.6 GHz band. Although several studies
focusing on radio propagation in underground mines have been published, measurement data and careful analyses for open-pit mines are still scarce. Our results aim at filling...
Methods, apparatuses, and computer programs for assigning measurement groups in a wireless network are disclosed. The measurement group may be announced by measurement group information comprised in a broadcast message transmitted in the wireless network. Reporting may be triggered by transmission of a request-to-report message transmitted in the w...
This document discloses a solution for reducing interference between wireless networks. According to an aspect, a method comprises: acquiring, by an access node of a first wireless network from at least one node of the first wireless network, information on at least one interfering node of a second wireless network; generating, by the access node,...
Existing cellular technologies are rapidly coming to their performance limits. This is due not only to the growth in data traffic and in the number of connected terminals, but also because we are on the verge of new era, where everyone and everything will be connected, with more demanding and varied requirements that cannot be satisfied by current ne...
There is provided a method, including receiving, by a receive node, a transmission request message for data transmission from a transmit node of a first basic service set, wherein the transmission request message includes an indication of a modulation and coding scheme to-be-used in the data transmission; detecting signal strength of the transmissi...
Multiple-input, multiple-output (MIMO) communications have attracted considerable attention in the last years. In particular, multiuser MIMO (MU MIMO) systems are able to offer higher link capacity of MIMO systems as long as channel state information (CSI) is available at the transmitter, so that the spatial properties of the channel can be exploit...
This paper presents a machine learning approach based on the concept of reinforcement learning andMarkov Decision Processes for link adaptation in orthogonal frequency-division multiplexing systemsthrough adaptive modulation and coding. Although machine learning techniques have attracted attentionfor link adaptation, the schemes proposed so far are...
The expansion of wireless broadband access network deployments is resulting in increased scarcity of available radio spectrum. It is very likely that in the near future, cellular technologies and wireless local area networks will need to coexist in the same unlicensed bands. However, the two most prominent technologies, LTE and Wi-Fi, were designed...
The default medium access mechanism for Wi-Fi, Distributed Coordination Function (DCF), is a simple contention based protocol aimed at providing a fair distribution of resources among Wi-Fi nodes. However, DCF suffers from significant performance degradation in the presence of dense deployments. Hence, improving the performance of the Wi-Fi MAC lay...
The increasing commercial success of Wi-Fi and the wireless communication industry forecast of exponential traffic growth for the next years indicate Wi-Fi dense deployments as scenarios more and more common in the future. Wi-Fi was not designed to operate in such scenarios. Because of its contention based channel access and backoff procedure, Wi-F...
In this paper, devices to devices communications underlaying cellular network techniques are proposed as an alternative to maximize spectral efficiency. This gain is obtained by the reuse of spectrum when different links are simultaneously established using the same resources. The cost of this technique is additional interference in cellular networ...
The use of TV white spaces as an alternative to overcome spectrum scarcity is a huge opportunity for new telecommunication systems and services. While being attractive for its desirable propagation characteristics, this part of the spectrum imposes a major difficulty from design and regulatory perspectives: how to optimize the use of spectrum and t...
Spectrum sharing is a powerful alternative to deal with the exponential increase on the wireless communication capacity demand. In this context, the coexistence of two of the most prominent wireless technologies today, Long Term Evolution (LTE) and Wi-Fi, is an important research topic. In the most common Wi-Fi network operation, the Distributed Co...
Wireless communications industry foresees an exponential increase of the traffic demand for the next years. Spectrum scarcity for the operation of cellular networks makes the use of unlicensed spectrum an attractive alternative for traffic offload. From the technical perspective, LTE pico/femtocells arise as the preferable traffic offload solution....
The recent development of regulatory policies that permit the use of TV bands spectrum on a secondary basis has motivated discussion about coexistence of primary (e.g. TV broadcasts) and secondary users (e.g. WiFi users in TV spectrum). However, much less attention has been given to coexistence of different secondary wireless technologies in the TV...
The deployment of modern mobile systems has faced severe challenges due to the current spectrum scarcity. The situation has been further worsened by the development of different wireless technologies and standards that can be used in the same frequency band. Furthermore, the usage of smaller cells (e.g. pico, femto and wireless LAN), coexistence am...
The recent development of regulatory policies that permit the use of TV bands spectrum on a secondary basis has motivated discussion about coexistence of primary (e.g. TV broadcasts) and secondary users (e.g. WiFi users in TV spectrum). However, much less attention has been given to coexistence of different secondary wireless technologies in the TV...
The explosive growth of mobile communications, and the overly crowded and expensive spectrum have pushed both system engineers and operators to make their systems as spectrally efficient as possible in order to accommodate the increasing traffic demand. This article is a tutorial introduction to the orthogonal subchannel (OSC) technique. OSC was ad...
Location Based Services can generate variety of new commercial applications and create new streams of revenue. However, there is currently no simple indoor positioning method for low-end devices which have no Wi-Fi or GPS capability. This paper presents a novel and simple audio-based localization system to provide location-aware content for low-end...
This paper presents a machine learning approach for link adaptation in orthogonal frequency-division multiplexing systems through adaptive modulation and coding. Although machine learning techniques have attracted attention for link adaptation, most of the the schemes proposed so far are based on off-line training algorithms, which make them not we...
The use of the white spaces of the UHF broadcasting band (470-790 MHz) by unlicensed users is a huge opportunity for new telecommunication systems and services. A fundamental issue on this new scenario of spectrum usage is the power emission limit of secondary users, since it is mandatory that they do not cause harmful interference to licensed ones...
In order to have the White Spaces of the UHF broadcast band (470–790 MHz) in use by unlicensed users, new implementation challenges and special efforts still need to be done. Regulators can significantly impact the feasibility of implementation through requirements on sensing thresholds or by defining emission limits of unlicensed users. This paper...
Machine type communications have emerged with new types of applications and revenue sources both for network operators and cellular/network equipment companies. This new kind of service may increase significantly the number of devices accessing the network in the next few years, and could have some impacts over the current services, namely normal v...
Multiuser MIMO (MU MIMO) communications have attracted considerable attention in the last years since these systems are able to offer the higher link capacity of MIMO systems as long as channel state information (CSI) is available at the transmitter, so that the spatial properties of the channel can be exploited by precoding. However, the time vary...
We describe the design, implementation, and eval-uation of Molé, a mobile organic localization engine. Unlike previous work on crowd-sourced WiFi positioning, Molé uses a hierarchical name space. By not relying on a map and by being more strict than uninterpreted names for places, Molé aims for a more flexible and scalable point in the design space...
Increased attention has been drawn to machine type communication (MTC) lately, which represents important extension for user functionality in today's technologies, as well as an important potential for marketing expansion. GERAN studies over MTC has mainly focused on applications requiring low throughput and wide coverage such as smart meter, which...
Multiple-input, multiple-output (MIMO) communications have attracted considerable attention in the last years. In particular, multiuser MIMO (MU MIMO) systems are able to offer higher link capacity of MIMO systems as long as channel state information (CSI) is available at the transmitter, so that the spatial properties of the channel can be exploit...
IntroductionOverview of GSM Voice EvolutionAMR and SAIC PerformanceOSC and VAMOS PerformanceConclusion
References
Speech quality is an important measurement for performance evaluation in a wireless mobile communication system since voice is still the most used service on it. The speech quality evaluation in GSM system employing narrowband and wideband AMR codecs with Orthogonal Sub Channel (OSC) technique is addressed in this paper. OSC is a feature proposed i...
Re-farming of 900 MHz band into HSPA has been started and is likely to happen later with LTE. Typically operators have less than 10 MHz block of 900 MHz spectrum and therefore co-existence of two systems in that band is causing challenges. One of the major issues is the high GSM voice traffic that will remain in the GSM network. How to cope the sam...
A new cooperative diversity scheme with two relay stations and linear coherent detection at the destination node is proposed in this paper. We consider that a perfect CSI is available at the destination node, as well to the relay stations, allowing each relay station to perform optimal beamforming. In order to evaluate the effect of a quantized fee...
This paper presents the results of propagation measurements taken at 3.5 GHz in Rio de Janeiro city. An urban environment was chosen to collect data. The results presented in this paper deal with path loss measurement for coverage prediction and the study of received signal variability essential for determining system parameters. The results are co...
In this paper some preliminary results of power allocation strategy in downlink cooperative MIMO applied to multi-carrier cellular systems are addressed and evaluated. The system model considers multi-antenna base stations communicating with single-antenna terminals simultaneously and the outage probability is evaluated for a given target rate tupl...
In order to take advantage of adaptive transmission techniques or multiple antennas, it is necessary to have actual channel state information (CSI) at transmitter and/or receiver. Due to system constraints and the time varying nature of the mobile radio channel, the CSI might be outdated, leading to performance degradation of the system. Channel pr...
In this paper, the energy detection spectrum sensing technique, based on the wavelet transform, is investigated. In order to evaluate the accuracy of the methodology, spectrum measurements were made in bands allocated for FM broadcast (88-108 MHz) and mobile services (824-835 MHz). Modifications in an existing technique were proposed in order to im...
Receive diversity with multiple antennas is a very well-known technique to improve receiver performance in fading environments. The concept is particularly simple in OFDM systems, where the channel effect on each subcarrier amounts to a complex multiplication of the transmitted symbol. It is also well known that, provided the antenna noise covarian...
In this paper we addressed the capacity gains achieved when the antenna selection is carried out in a frequency selectivity MIMO measured channel. The best antenna subsets were selected and analyzed for different environments and for the bandwidth of 20 MHz. The gains with frequency selection, after the antenna selection, were also evaluated. Final...
In this paper we present the results of a MIMO wideband measurement campaign carried out in hallways (indoor scenario) with a carrier frequency of 2 GHz. The wideband and narrowband channel capacity and MIMO channel characteristics were evaluated. The correlation between channel capacity and physical parameters as azimuth spread (AS) and delay spre...
In this paper presents the results of antenna selection for a MIMO wideband measurement campaign carried out in indoor scenario with a carrier frequency of 2 GHz. The amplitude and phase of the received signal were collected at 801 frequency values in the 200 MHz bandwidth. For each frequency, the best set of antennas was selected. The spatial sele...
This article proposes several types of interference cancellation for the downlink connection in the GSM mobile communications system. The solutions are in the class of dual antenna interference cancellation (DAIC) which utilize two antennas in the mobile station in order to improve the network performance in the link level. The performance of the r...
In this paper we present the results of a MIMO wideband measurement campaign carried out in an indoor scenario with a carrier frequency of 2 GHz. The wideband and narrowband channel capacity and several channel parameters were evaluated from the measured data. The correlation between channel capacity and physical parameters as angle spread, coheren...
This work investigates the effect of some EQoS - enhanced QoS - parameters through dynamic system-level simulations. These parameters are used to adjust the EQoS framework mechanisms. Dimensioning and optimization of these parameters are essential since they improve the EQoS frame functionality and consequently the performance of data network is im...
In this paper we present the results of an ultra wideband (UWB) measurement campaign carried out in an indoor environment. The UWB channel parameters were evaluated from the measured data. Specially, temporal dispersions of the multipath channel were calculated and the relationship among these parameters was studied. The sounding technique was base...
This paper presents the results of an ultra- wideband measurement campaign carried out in different indoor environment with 850 MHz of bandwidth. This measurement procedure allows us to characterize the small- scale statistics of the channel. Hence, the channel temporal dispersions analysis was done. The temporal dispersions are assessed in terms o...
This work presents the results of an estimation of the mobile radio channel space-time dispersion at 1.8 GHz, through the use of the frequency sounding technique. Some changes in the classical technique were implemented: a set of antennas known as an array was built and calibrated, and a processing algorithm of the measured signal was tested. The c...
The results of a 1.8 GHz indoor wideband channel sounding survey in some typical environments, trying to account for pedestrian subscriber mobility, are presented. The sounding technique has been based on the classical frequency domain, with an optic link instead of coaxial cables providing an extended path range, up to 350 m. Three different scena...
The results of propagation measurements of a 3.5 GHz signal realized on a typical urban environment at Rio de Janeiro city are presented. The path-loss, obtained from two different urban environments, is calculated and compared with the most popular prediction models in the literature. Variability characteristics such as the large-scale fading and...
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