Andra Pastrav

Assessing VoLTE performances for fundamental E-UTRAN technologies

As the LTE network infrastructure is currently in development, this paper provides an objective assessment of the VoIP performances for an LTE cell deployed in a 3D modeled urban area. Fundamental E-UTRAN technologies have been tested in the LTE cell used at full capacity for the 1.4MHz and 5MHz channel bandwidths. The VoLTE performance improvements are evaluated in terms of QoS and QoE parameters. The simulation results provide useful insights for the operators regarding an efficient LTE network planning.

GPStation-6 employment for GNSS TEC monitoring in SIRIUS project

HF communications have proved to be a quick and reliable solution for encrypted data transmissions in scenarios where other infrastructure is damaged or inexistent. However, the behavior of the ionosphere has to be predicted in order to model a suitable radio link and overcome the errors introduced during ionospheric propagation. As a partner in the SIRIUS project, the Technical University of Cluj-Napoca has acquired, installed and employed the NovAtel GPStation-6, a GNSS ionospheric scintillation and TEC monitor receiver to estimate the electronic density and to be used in the validation of the ionospheric model developed within the project. This paper aims at presenting the capabilities of the GNSS receiver, its installation, the calibration process, and TEC measurements.

Performance evaluation of a fuzzy-based QoS support implementation

The task of Quality-of-Service (QoS) routing is to find a path in the network that satisfies certain constraints on metrics such as delay, jitter, bandwidth and packet loss. All routing algorithms are designed for intra-domain QoS support, and when multiple technologies are interconnected, a proper end-to-end QoS support cannot be guaranteed. This paper proposes a method for the most suitable end-to-end path selection in a unified network architecture. The solution is implemented in two phases: firstly, the network is tested in order to obtain a list of all possible routes and secondly, the best path is selected using the fuzzy logic algorithm. This solution has been implemented and validated through network simulations.

HCCA support in IEEE 802.11 networks QoS and QoE performance evaluation

The profile of the service users in telecommunication networks shows a continuous growth in the interest towards real-time applications (streaming and interactive video, web conferences, voice over IP). In order to assure the optimal parameters for this kind of transmissions, the implementation of mechanisms that provide service quality support is mandatory. One way of assuring the QoS support in IEEE 802.11 networks is to enable the HCCA mechanism. This paper provides an objective analysis of the performances of the HCCA mechanism regarding voice and video applications by means of the evaluation of specific QoS/QoE parameters: delay, jitter and MOS.

Conceptual Architecture of a Retrodirective Antenna System with Beamforming Capabilities

As antenna arrays can achieve high directivity, they improve the performance of a receiver in terms of signal detection and offer the support for the implementation of advanced techniques like direction-of-arrival estimation, source localization, beamforming and user tracking. In the context of the RDAntenna project which aims to prototype an adaptive retrodirective system, we proposed a comprehensive solution which identifies the target user and changes the radiation pattern of the access point to improve the users quality of the transmission. This paper presents the framework of the project and the conceptual solution for an adaptive retrodirective system using an array of antennas controlled by Software Defined Radios, able to perform beamforming operations.

SDWN for End-to-End QoS Path Selection in a Wireless Network Ecosystem

In recent years, a significant increase of mobile data traffic has been observed, resulting in more complex and diverse network services. Thus, it becomes more difficult to fulfill the requirements of QoS-sensitive applications. The emergence of new technologies such as Cloud Computing, Software Defined Networking and Network Function Virtualization provides an excellent ecosystem for QoS routing solutions to support real-time applications requirements in wireless networks. The scope of this paper is to propose a Software Defined Wireless Network controller implementation to determine the appropriate end-to-end QoS path in a wireless network ecosystem. The proposed solution is based on Bayesian reasoning and Fuzzy logic algorithms.

Implementation of a SDR-based redundant access network using NI USRP-RIO

Wireless transmission is, broadly speaking, considered unreliable and unstable. For real-time applications, redundancy must be counted as a solution for preventing system unavailability. In this paper a testbed comprised of three National Instruments USRP-RIO platforms (two acting as access points, and one as a client station) was set in order to test the performance of a redundant IEEE 802.11-based access network. The 802.11 Application Framework was modified on the receiving side to allow the client to change between the two access points operating in different frequency bands, considering as the trigger values the received radiofrequency input power and throughput. Experimental results and measurements confirm that this implementation improves the reliability of the access network, and bring forward the high processing capabilities of the USRP FPGA based devices. Moreover, the test measurements were validated using the Rohde & Schwarz CMW500 Wideband Radio Communication Tester, proving the compatibility of the adopted solution.

Experimental evaluation of the IEEE 802.11ac standard using NI USRP 2954R

This paper proposes an experimental evaluation of the IEEE 802.11ac standard. The evaluation testbed is comprised of two National Instruments Universal Software Radio Peripheral (NI USRP) 2954R Software Defined Radios (SDRs) controlled by the NI-PXIe-8840 Quad-Core embedded computer running the 802.11 Application Framework and Lab VIEW Communications 2.0. Two evaluation scenarios are analyzed: (1) a conducted transmission to assess the maximum potential of the USRP transmitters, and (2) an over the air transmission to evaluate the performance in real environmental conditions. A set of measurements has been performed considering different configuration parameters: transmission channel bandwidth (20MHz and 40MHz), backoff value (2 and 4), and available modulation and coding scheme. The conducted measurements indicate that higher data rates are obtained for higher modulation and coding scheme orders, larger channel bandwidth, and a lower backoff value. The over the air experiments showed the negative effects of the interferences on the transmission, especially on higher order modulations, in terms of measured data rates, plots of the received constellations and block error rate. Finally, the radio transmissions were validated using the Rohde & Schwarz CMW 500 Wideband Radio Communication Tester.

Implementation of an UWB-based module designed for wireless intra-spacecraft communications

Traditionally, intra-spacecraft data distribution is performed using wired data-handling systems. However, this approach increases the complexity and dry mass of the satellite harness. Therefore, extensive research is done to replace, complement or extend the wired communications with wireless ones. In this context, this paper presents the UWB-based solution developed within the WiSAT project funded by ESA. Considering the determined set of requirements for intra-spacecraft wireless communications, the proposed VN360 UWB module implements a custom software stack of the ISA-100.11a protocol over the IEEE 802.15.4 UWB PHY layer. The solution is tested and validated in different laboratory environmental conditions (TRL 4), including the satellite mock-up built within WiSAT. The results prove the capacity of the VN360 UWB module to establish a reliable intra-spacecraft UWB connection.

A proposed mechanism for traffic management during gateway outage periods in high throughput satellite systems

To reach a capacity of 1Tbps the next generation of high throughput satellite systems will have to use frequencies in the Ka band and above. At these frequencies, the precipitation attenuation becomes more severe and may lead to gateway outage events. Considering the weather uncorrelation between the gateway sites, a solution to the outage problem is to redirect the traffic from the gateway in outage to one or more gateways that are able to support it. This paper proposes a mechanism that is able to manage the traffic from the gateway in outage and select the best path in the terrestrial network to redirect the traffic towards an available gateway. The mechanism is tested through simulations in QualNet Developer and the results provide useful insights regarding its potential to redirect the traffic in an HTS system.