Tudor Palade

Wireless LAN medium access techniques QoS perspective

Different people and communities perceive and interpret Quality of Services (QoS) in different ways. We consider that QoS problem has two major perspectives: (1) network perspective and (2) application/user perspective. Networks receive from the applications implicitly or explicitly their QoS parameters and need to respond to these requests by supplying QoS services. The papers analyze QoS parameters from the network perspective looking on medium access control layer (DCF and EDCF medium access techniques). The essential aim of the paper is to illustrate and demonstrate 802.11e effects on traffic priority. We use ns-2.26 simulator in our simulation scenarios.

Low-cost SDR-based ground receiving station for LEO satellite operations

This paper outlines the feasibility of using Software-Defined Radio (SDR) technology for space applications by developing and setup of a low-cost VHF/UHF ground receiving station in order to support existing and future university missions. The proposed solution is based on the integration of commercial off-the-shelf components available on the market. The paper will present some of the hardware and software related issues regarding the implementation of an educational ground station for operation with Low-Earth Orbit satellites.

In-situ measurements regarding LF radio wave propagation using DCF77 time signal transmitter

This paper illustrates experimental results regarding the ionospheric LF radio wave propagation using the DCF77 time signal transmitter. The sample data collected revealed the correlation between the diurnal variations of the received signal level and the time-domain scattering of the demodulated PPS (Pulse-Per-Second) signal.

Study of co-channel cross-layer interference for the downlink communication in femtocell networks

The paper is concerned with the study of the co-channel cross-layer interference which appears in evolved mobile networks, in which femtocell access points (FAPs) have been deployed. We will investigate the levels of interference for the downlink communication channel, in two cases: macrocell base station (MacroBS) interference at the femtocell user (FUE), and FAP interference at the macrocell user (MUE). The simulations are carried out in a combined indoor-outdoor environment. The performances of the network are evaluated according to the signal to interference plus noise ratio, measured on the downlink communication channel. The results of the study reveal the impact of the deployment of femtocells in existing mobile networks.

Multi antenna STBC transmission technique evaluation under IEEE 802.11n conditions

In this paper, the STBC (Space-Time Block Codes) transmission technique is used in order to evaluate the link availability and transmission quality of multi antenna systems that operate under various channel conditions. The propagation channel follows the IEEE 802.11n specifications. The influence of the diversity order and the spatial correlation is investigated in terms of error performance and throughput. The efficient use of the space and the power resources leads to significant improvement in the link reliability, if channel state is available at the transmission. The throughput enhancement of a 2×2 MIMO system relatively to the basic SISO (Single Input Single Output) mode is evaluated considering a fix antennas separation and different channel models.

An Innovative QoS Paradigm Based on Cognitive In-network Management of Resources for a Future Unified Network Architecture: I-NAME QoS Model

The goal of this paper is to present an innovative QoS solution of managing resources by knowing the service requests and the network context in a unified network architecture. Considering the nowadays technical solutions and the holistic vision of the future network of information, this solution is proposing a cognitive QoS model of self-managing resources by using the network virtualization concept in conjunction with the in-network management concept. Thus, the main goal of the paper is to solve resource management problem inside a unified network architecture remodeled by the actual trends in the field – virtualization and in-network management – by validating while evaluating the I-NAME QoS proposed model.

Radio coverage and performance analysis for local area networks

The paper is concerned with the study of coverage and co-channel interference for local area networks operating at three different frequencies - 2.4 GHz, 5 GHz and 60 GHz. The studies will be conducted in an indoor environment. The effects of the surrounding environment on the radio wave propagation are studied in detail for each of the three technologies. Advantages and disadvantages of each of the networks are presented, taken from the analysis of the obtained results. Finally, the best solution for our environment is proposed.

Spatial multiplexing and diversity in a MIMO based WLAN system

Spatial processing techniques are considered as means to enhance the performance of WLANs systems. Different multi-antenna methods exploit different properties of the radio channel, so in this paper, we identify, based on the channel state, the physical layer parameters that can be controlled in the attempt to satisfy the user/application requirements, with an efficient use of the available radio resources. Performance criteria considered for the evaluation are the packet error rate and the throughput. Channel state information at the transmitter provides link speed enhancement especially for high transmit diversity system and low values of the signal to noise ratio.

Adaptive Kalman Filter for target tracking in the UWB networks

The aim of this paper is to emphasize the benefits of using the information provided by the UWB network for the Adaptive Kalman Filtering (AKF). The standard 802.15.4 specifies in the section PHY UWB the field of parameters Ranging FoM, parameters that show the trust level of the receiver in determining the reception moment of leading edge of the ranging pulse. Using the specified parameters, Confidence Interval and Confidence Level, and based on statistical theory the current standard deviation is determined for every anchor of the network. The standard deviations of the anchors are combined in order to get the observation covariance for the Kalman filtering. In the steady state the innovation should be within the Confidence Region ellipsoid and if the innovation does not fall in that region the filter diverges or it is biased and it should be online tuned. The difference between the innovation and the Confidence Interval will constitute the information for adjustment of the state covariance in the Kalman Filter.

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.