Laura Pierucci

Next-generation mobile satellite networks

Due to the increasing demands of multimedia services supporting high bit rates and mobility, ATM, TCP/IP, and satellite technology are going to be associated to form the internetwork infrastructure of future global systems. In this scenario, distinctions between terrestrial and satellite communications systems, as well as between fixed networks and 3G mobile networks, will cease to exist in a global coverage wireless system. The European Action COST252 actively participated in developing the satellite component of UMTS.

A continuously adaptive MLSE receiver for mobile communications: algorithm and performance

The paper presents a Euclidean distance maximum likelihood sequence estimation (MLSE) receiver, based on the Viterbi algorithm (VA), suitable for fading and noisy communications channels, as that specified by the Group Special Mobiles (GSM). In a mobile cellular system, the fast varying channel characteristics, due to the fading and Doppler effects, require adaptive methods to update the channel coefficients to the MLSE receiver. The proposed technique continuously estimates the channel characteristics directly within the metric calculation of the VA. At each step of the VA, the sequence associated to the path with the best metric value (minimum-survivor method) among the survivor paths is used to update the channel estimate (employing conventional adaptive algorithms) throughout the entire informative sequence. However, the detection of the transmitted data sequence is performed by the VA only at the end of each burst. The proposed technique allows simpler receiver implementation and the simulation results show a good performance of this adaptive MLSE receiver in typical GSM environments.

An interactive multimedia satellite telemedicine service

We present a telemedicine application, called the Medical Environment for Diagnostic Images (MEDI), that provides remote medical care services while taking advantage of the broadcast and multicast capabilities and the wide-band capacity of satellite systems. We developed the application in an open environment (Java) using a client-server architecture based on TCP/IP. We evaluated the performance of the application on satellite connections.

The quality of experience perspective toward 5G technology

Quality of experience (QoE) is the subjective acceptability of the quality of a telecommunication service perceived by the user. This paper expands the vision to new QoE acceptability for the future 5G networks and analyzes the impact of the main challenges of 5G on QoE. An efficient QoE estimation method tailored for 5G systems is also proposed based on the neural network (NN) approach. Due to their ability to fully learn the causal relationship between network parameters of quality of services (QoS) and the resulting QoE, NN can be suitable to gain QoE self-optimization for 5G. Again, new increasingly smart user devices will be delegated to handle the most burdensome tasks of ensuring user satisfaction.

Design of a digital MLSE receiver for mobile radio communications

A digital receiver suitable for use in the future GSM pan-European cellular system is described. The receiver uses a maximum-likelihood sequence estimation (MLSE) implemented by means of the Viterbi algorithm to compensate for the heavy selective distortions caused by multipath propagation. The performance of the receiver is evaluated through a channel simulator suitable for mobile communications. The results obtained show the good behavior characteristics for the receiver in different modes of operation. Easy implementation of the device using VLSI technology is expected.<<ETX>>

UWB localization on indoor MIMO channels

The paper focuses on the joint use of a UWB system along with antenna arrays for localization purposes of mobile terminals in an indoor MIMO environment. The proposed localization method estimates the direction of arrival (DoA) by evaluating the delays of the received UWB signals impinging on the antenna array. Correlation processing in the time domain of the UWB impulse wavefronts yields precise temporal resolution which provide a fine estimation of DOAs if it is combined with an uniform linear antenna array and as a DS-TH (direct sequence-time hopping) UWB signals is used, an unique independent code identifies each users, therefore the desired user direction can be evaluated. In the simulated system each transmitter emits the same signal through indoor channels and each UWB signal replica is affected by AWGN noise, so slightly different signals are obtained from each channel, which is the perfect situation for using a MIMO implementation. Therefore, a 2/spl times/2 and a 2/spl times/3 UWB-MIIMO systems are analyzed to evaluate the angle error rate for different E/sub b//N/sub 0/ values.

An Adaptive Cross-Layer Strategy for QoS-Guaranteed Links in 4G Networks

This paper focuses on the problem of ensuring quality of service (QoS) to 4G network users. An adaptive cross-layer (ACL) strategy, that jointly optimizes the parameters of physical (PHY) and medium access control (MAC) layers using queueing theory, is proposed and applied to mobile user communications in an OFDM-based wireless network. PHY and MAC layers are referring to IEEE 802.16 standard, supporting, respectively, different modulations and the automatic repeat request (ARQ) protocol. PHY and MAC layer parameters are here optimally combined by ACL strategy to meet the QoS requirements. The main contribution of the paper is the evaluation of the impact of mobility on ACL strategy performance, by using an accurate channel model that accounts for shadowing effects. The simulation results show that the ACL strategy outperforms non-adaptive or single-layer strategies, in terms of bandwidth savings. Also, ACL strategy is able to guarantee the requested QoS in the different mobility scenarios with different degrees of performance.

Handset and network quality performance benchmarking for QoE improvement

Quality of Experience (QoE) is the subjective measurement of the quality of a telecommunication service perceived by the user. Overall acceptability may be influenced by user expectations and context, and QoE includes complete end-to-end system effects. Radio access network quality measurements are usually enough to evaluate the user experience of voice services. In addition, the customer satisfaction of the packet data services also depends on the type of the user equipment (UE) and on the multimedia content characteristics. To evaluate the QoE, the paper analyzes the behavior of different types of user equipments related to voice and packet data traffic statistics on the radio access network by Telecom Italia. The analysis of some suitable Key Performance Indicators is shown. The performance of different user equipment types are monitored by joining the dropped call events with the radio link conditions, in terms of signal quality, signal strength, distance of mobile equipment from the serving cell. The relation of packet loss rate, latency and network quality are also evaluated with respect to the different user equipment categories analyzed (e.g. handset, smartphone, USB Modem, tablet) for data services based on the transmission control protocol (TCP). The results show that mobile terminals behave very differently from each other, affecting both the amount of voice dropped calls and packet data retransmission in different radio link conditions and consequently the user quality of experience.

Real time detection and tracking of Gauzes by RFID UWB technique

The paper presents the implementation of the GUID (Gauzes UWB Identifier) system to control the path of gauzes and other medical instruments during surgical operations. The system allows tracking of these devices during the entire surgery, with particular reference to real-time localization of gauzes within the patients body. A precise localization of gauzes, available to the surgeon, permits an easy removal of these devices, which are sometimes difficult to identify by visual perception. The final objectives are the improvement of the patient safety, of surgeon working procedures, and the reduction of stress conditions of the surgical staff. The GUID prototype is based on RFID Ultra Wide Band(UWB) technology and the experimental phases were carried out in laboratory using the tags both in air and in biological tissue. The results show the performance of a correct identification of the tags and the accuracy of the calculated position with respect to the real position of the tags.

Buffer-Aided Diamond Relay Network With Block Fading and Inter-Relay Interference

A simple diamond half-duplex relay network composed of a source, two decode-and-forward half-duplex relays, and a destination is considered, where a direct link between the source and the destination does not exist. For this network, we study the case of buffer-aided relays, where the relays are equipped with buffers. Each relay can receive data from the source, store it in the buffer, and forward it to the destination, when the channel conditions are advantageous. Thereby, buffering enables adaptive scheduling of the transmissions and receptions over time, which allows the network to exploit the diversity offered by the fading channels. For the considered half-duplex network, four transmission modes are defined based on whether the relay nodes receive or transmit. In this paper, we derive the locally optimal scheduling of the transmission modes over time and investigate the achievable average rate, when the relays are affected by inter-relay interference. Since the proposed buffer-aided transmission policies introduce unbounded delay, we provide a sub-optimal buffer-aided transmission policy with limited delay. Moreover, for inter-relay interference cancellation, we consider two coding schemes with different complexities. In the first scheme, we employ dirty paper coding, which entails a high complexity, whereas in the second scheme, we adopt a low-complexity technique based on successive interference cancellation at the receiving relay nodes and optimal power allocation at the transmitting nodes. Our numerical results show that the proposed protocols, with and without delay constraints, outperform existing protocols for the considered network from the literature.