António Serrador

A 802.11p prototype implementation

This paper presents an IEEE 802.11p full-stack prototype implementation to data exchange among vehicles and between vehicles and the roadway infrastructures. The prototype architecture is based on FPGAs for Intermediate Frequency (IF) and base band purposes, using 802.11a based transceivers for RF interfaces. Power amplifiers were also addressed, by using commercial and in-house solutions. This implementation aims to provide technical solutions for Intelligent Transportation Systems (ITS) field, namely for tolling and traffic management related services, in order to promote safety, mobility and driving comfort through the dynamic and real-time cooperation among vehicles and/or between vehicles and infrastructures. The performance of the proposed scheme is tested under realistic urban and suburban driving conditions. Preliminary results are promising, since they comply with most of the 802.11p standard requirements.

Policies for a Cost Function for Heterogeneous Networks Performance Evaluation

Heterogeneous cellular networks are analysed by taking several Key Performance Indicators (KPIs) into account, their proper balance being required in order to guarantee a desired Quality of Service (QoS). An approach to integrate a set of KPIs into a single one is presented, by using a Cost Function that includes these KPIs, providing a single evaluation parameter as output, and reflecting network conditions and Common Radio Resource Management (CRRM) strategies performance. The proposed model enables the implementation of different CRRM policies, by manipulating KPIs according to users or operators perspectives, allowing for a better QoS. Results show that different policies can in fact be established, with a different impact on the network, e.g., with median values ranging by a factor higher than two.

A Cost Function Model for CRRM over Heterogeneous Wireless Networks

Heterogeneous cellular networks performance is usually analysed by taking several Key Performance Indicators (KPIs) into account, their proper balance being required in order to guarantee a desired Quality of Service (QoS). An approach to simplify and integrate a set of KPIs into a single one is presented, by using the proposed Cost Function model that includes these KPIs, providing a single evaluation parameter as output, and reflecting network conditions and Common Radio Resource Management (CRRM) strategies performance. This paper proposes a Cost Function that enables the implementation of different CRRM algorithms and policies, by manipulating KPIs according to user’s or operator’s perspectives, allowing for a better QoS. Results show that different policies can in fact be established, with a different impact on the network, e.g., with median values ranging by a factor higher than two.

A model to evaluate vertical handovers on JRRM

In a heterogeneous cellular networks environment, users behaviour and network deployment configuration parameters have an impact on the overall Quality of Service. This paper proposes a new and simple model that, on the one hand, explores the users behaviour impact on the network by having mobility, multi-service usage and traffic generation profiles as inputs, and on the other, enables the network setup configuration evaluation impact on the Joint Radio Resource Management (JRRM), assessing some basic JRRM performance indicators, like Vertical Handover (VHO) probabilities, average bit rates, and number of active users, among others. VHO plays an important role in fulfilling seamless users sessions transfer when mobile terminals cross different Radio Access Technologies (RATs) boundaries. Results show that high bit rate RATs suffer and generate more influence from/on other RATs, by producing additional signalling traffic to a JRRM entity. Results also show that the VHOs probability can range from 5 up to 65 %, depending on RATs cluster radius and users mobility profile.

Energy efficiency gains using VHOs in heterogeneous networks

Partially, the future of mobile and cellular networks will be about energy consumption savings, at the network infrastructure side. In the heterogeneous cellular networks environment, these can be achieved based on bandwidth adaptation, discontinuous transmission, relays, or even Base Stations (BSs) shutdown when possible. This paper proposes an approach for power savings using Vertical Handovers (VHOs) among different Radio Access Technologies (RATs), based on Radio Resource Management. The presented solution use a utility function focused on the energy efficiency of a given BS and RAT. An active VHO trigger mechanism is also proposed to provide RF power savings by handover mobile terminals to the most efficient RAT. Based on a power model proposed by the ICT-EARTH project, it is possible to translate RF power savings into system level ones. Results show that VHOs RF power gains range up to 46%, and up to 13% at the BS system level.

Impact of MIMO Systems on CRRM in Heterogeneous Networks

The impact of MIMO systems on common radio resource management (CRRM) in heterogeneous cellular networks is analysed, by taking some key performance indicators (KPIs) into account. A recent method used to integrate MIMO effects/gains into system level simulation is presented. User mobility profiles are mapped onto MIMO terminal capabilities, and their impact is analysed. CRRM algorithms are based on a integrated set of KPIs, by using a cost function (CF) that includes these KPIs, providing a single evaluation parameter as output, and reflecting network conditions and strategies performance. Results show that different mobility profiles and mobile terminals capabilities have different impacts on the network performance, e.g., with median CRRM QoS values ranging by a factor higher than two, when MIMO systems are present.

Physical layer aware network architecture for the future internet

In this article, physical layer awareness in access, core, and metro networks is addressed, and a Physical Layer Aware Network Architecture Framework for the Future Internet is presented and discussed, as proposed within the framework of the European ICT Project 4WARD. Current limitations and shortcomings of the Internet architecture are driving research trends at a global scale toward a novel, secure, and flexible architecture. This Future Internet architecture must allow for the co-existence and cooperation of multiple networks on common platforms, through the virtualization of network resources. Possible solutions embrace a full range of technologies, from fiber backbones to wireless access networks. The virtualization of physical networking resources will enhance the possibility of handling different profiles, while providing the impression of mutual isolation. This abstraction strategy implies the use of well elaborated mechanisms in order to deal with channel impairments and requirements, in both wireless (access) and optical (core) environments.

Parameters for the Definition of Scenarios for CRRM Performance Evaluation

This paper addresses the RRM and CRRM reference scenarios state of the art. Many researchers use simulation tools for their work, using different approaches and scenarios, disabling the possibility to evaluate and compare results among them. Thus, this paper besides pointing out the different activities on reference scenarios, proposes a set of scenarios for RRM and CRRM for GERAN, UTRAN and WLAN. This paper constitutes a first approach to the identification of key parameters related with RRM/CRRM performance evaluation

A model for heterogeneous networks management and performance evaluation

In general, modern networks are analysed by taking several key performance indicators (KPIs) into account, their proper balance being required in order to guarantee a desired quality of service (QoS), particularly, cellular wireless heterogeneous networks. A model to integrate a set of KPIs into a single one is presented, by using a cost function that includes these KPIs, providing for each network node a single evaluation parameter as output, and reflecting network conditions and common radio resource management strategies performance. The proposed model enables the implementation of different network management policies, by manipulating KPIs according to userspsila or operatorspsila perspectives, allowing for a better QoS. Results show that different policies can in fact be established, with a different impact on the network, e.g., with median values ranging by a factor higher than two.