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The lack of technical equipment is one of the hurdles in facing challenges in engineering education and basic research for universities in developing countries. In this paper we present a low-cost laboratory mostly based on commercial off-the-shelf wifi routers. A basic workbench is made out of three second hand wireless routers. Our local market provided plenty of used D-Link DIR-300. Total cost...
There has been a high concern regarding the energy saving on mobile devices recently, for mobile devices have been performing increasingly complex tasks over time. The computation offloading is one of the most popular techniques used by developers as an effective way of saving energy on mobile devices, which consists on executing complex tasks in external servers with different purposes including...
Methods based on order statistics are often used in finance, quality control, data and signal processing, especially when signals of interest are immersed in impulsive noise. These allow to include rank information by increasing the dimension of the problem. In large dimension problems, we are usually required to know only the second order statistics. In this article we use a rank-one quadratic measurement...
In this paper we propose an SDN-based control plane for the University of Costa Rica. Our campus network faces heavy congestion problems and fails at providing adequate quality of service (QoS). Therefore, we describe a solution that leverages priority-traffic routing to ensure that important services (such as live video streaming) are not as heavily affected by congestion. To this end, we first survey...
In this paper, we consider the deployment of multiple antennas as a way to exploit spatial diversity in the uplink of multiple access systems that adopt low-density spreading (LDS) with orthogonal frequency-division multiplexing (OFDM). An overloaded LDS-OFDM system is assumed, i.e., the number of users served is assumed greater than the number of resources. A basic model is developed and from it...
A WBANs (Wireless Body Area Networks) number dimensioning technique for cluster-type network structure is proposed in this paper. The WBANs, in this structure, are placed, together with the sink nodes, at the ends of the network. An access scheme is provided so that the sink nodes, which temporarily store the data packets of the WBANs, transmit these packets to the collector nodes. The collector nodes...
This paper demonstrates an innovative variable fractional rate Digital Down Converter(DDC) architecture for satellite communication where the carrier frequency and output sample rate can be changed dynamically at run time. The proposed algorithm is highly modular and generic so that the DDC can decimate by any fractional ratio i.e. the ADC sampling rate may be any integer or non-integer multiple of...
It is well-know that carrier frequency offset in the subcarriers of orthogonal frequency division multiplexing (OFDM) leads to intercarrier interference (ICI); therefore, system degradation occurs. Nevertheless, this issue may effectively be mitigated via the pulse shaping filter method. In this manuscript, we present the improved double jump linear combination (IDJLC) function. With the goal of minimizing...
The design of blind rendezvous strategies for dynamic spectrum access in multi-users, multi-hop networks is a challenging task. In this paper, a two radios synchronization strategy that minimizes the time to rendezvous in multi-users networks is analyze. In fact, it has been recently demonstrated that this synchronization strategy provides optimum results in terms of maximum time to rendezvous (MTTR)...
Some of the future wireless networks are related to the provision of higher data rates and lower energy consumption. In contrast to the clear increasing spectrum demand, bandwidth is a limited resource. Cooperative diversity allows to increase the spectral efficiency and the reliability of the communication. However, in scenarios with high node density and high mobile data traffic volume the collaboration...
In this paper, we address the issue of profiling users over the Internet using meta-data logs derived from network flow data (hence preserving a high degree of privacy). In this broader context, we specifically aim to empirically demonstrate that Internet volume and time of usage of humans do exhibit repeatable behavior over time. In our experimental study, Internet usage statistics of octets and...
A greenhouse monitoring system using hierarchical wireless sensor network (WSN) is presented in this paper. The main parameters required to monitor and control a greenhouse are air humidity and temperature, ground moisture and environment lightness. For the data gathering of these parameters, a hierarchical WSN is presented in this work. In this configuration, the sensors, aggregated with all gathering...
In this paper a practical application of an electrooptical communication system based on external modulation is reported. The sixteen ATSC TV-channels located at 2.4 GHz, were transmitted over a 30 km of standard optical fiber. The transmitted TV-signal uses Single-Side Band Full Carrier (SSBFC) modulation, allowing in this way an adequate management of the transmitted power and the bandwidth. The...
The introduction of Space division multiplexing (SDM) in optical networks brings new challenges for protection of networks since a lightpath can span multiple cores. In this paper, we investigate the problem of dynamic protection against two simultaneous failures in spacial division multiplexing elastic optical networks. For that, we propose a new path-protection sharing spectrum and straddling p-cycle...
The VST-TDMA access protocol has shown to have many advantages over existing protocols in centralized (star) wireless network architectures. As most data-link layer protocols, it does not have a recovery feature as data integrity is supervised by the connection-oriented transport protocols. Nevertheless, VST-TDMA possesses the flexibility to easily incorporate a retransmission feature that allows...
Low voltage, in-home power-line communications (PLC) networks allow direct communication between smart meters (SM) and in-home devices (IHD). In order to minimize security issues, in many deployment scenarios transmission takes place only towards the IHD to display consumption data, with no backwards channel. As a result, channel estimation is difficult and it is necessary to use robust transmission...
Wireless applications require the use of Power Amplifiers for signal transmission. Those are generally nonlinear devices, and there is a trade-off between efficiency and the signal distortion level, which degrades performance. Besides that, transmission waveforms suffer from spectral regrowth when non-linearities are present. Moreover, some power amplifiers also carry memory effects, which further...
The shifting towards New Radio waveforms for future cellular networks will require a smooth transition from the existing 4G physical layer (PHY), which is based on the LongTerm Evolution-Advance (LTE-A) system. This will allow the service provider to develop less cost multi-standard devices that rely on the same master clock compatibility and with the same time-frequency grid representation of the...
This article presents the analysis of the influence of environmental variables on the received signal power from a point to point wireless link (f = 5.52 GHz) in a tropical urban environment, in the cities of Guayaquil and Duran, of Ecuador. The study included data of five variables such as relative humidity (HR), atmospheric temperature (T), solar radiation (RS), rainfall (Pr) and signal power (P)...
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