Anna Umbert

Evaluation of Spectrum Occupancy in Spain for Cognitive Radio Applications

Cognitive radio (CR) has been identified as a promising solution to the so-called spectrum scarcity problem. The basic idea of this paradigm is to allow unlicensed users to access in an opportunistic and non-interfering manner some licensed bands that are temporarily unoccupied by licensed users. CR is expected to significantly increase current spectrum usage. However, before this paradigm can turn into reality, a full understanding of the dynamic usage of spectrum is required. Current spectrum utilization has already been evaluated in some measurement campaigns. However, most of them were performed in USA and therefore evaluated the American spectrum regulation and utilization. Few studies have been carried out in other places. In this context, this paper presents spectrum occupancy measurements conducted in the frequency range from 75 MHz to 3 GHz in an outdoor environment in urban Barcelona, Spain. The measurements are analyzed and compared to the official spectrum regulations. The obtained results demonstrate the existence of a significant amount of spectrum available for the deployment of future CR networks.

Spectral occupation measurements and blind standard recognition sensor for cognitive radio networks

Cognitive radio has been claimed to be a hopeful solution to the existing conflicts between spectrum demand growth and spectrum underutilization. The basic underlying idea of cognitive radio is to allow unlicensed users to access in an opportunistic and non-interfering manner some licensed bands temporarily unoccupied by licensed users. The cognitive radio concept relies on two basic premises: the current spectrum underutilization, which has been demonstrated in some spectrum measurements campaigns, and the ability of unlicensed users to effectively detect and identify the presence of different licensed technologies in order not to cause harmful interference. In this context, this paper reports the joint work on these two areas that is currently being carried out in the framework of the FP7 Network of Excellence in Wireless COMmunications (NEWCOM++). Concretely, this paper presents spectrum occupancy measurements conducted in the frequency range from 75 MHz to 7075 MHz that demonstrate the low degree to which spectrum is currently used in an urban outdoor environment and also describes the blind standard recognition sensor concept, a sensor embedded in a cognitive radio equipment to enable the identification of many commercial wireless standards without the need to connect to any network. The joint research in both areas is a key step in promoting and validating the idea of dynamic spectrum usage.

Cross-layer scheduling strategy for UMTS downlink enhancement

This article describes the benefits of including cross-layer information in the scheduling mechanism of a UMTS downlink channel. In particular, the information obtained from the fast power control algorithm is used to properly schedule transmissions. A prioritization function that exploits the short-term channel variations is proposed. This strategy is shown to be a feasible approach to improve system performance in terms of capacity and delay. This enhancement is obtained as a benefit of intrinsic multi-user diversity. The proposal is applicable within the current UMTS radio resource management framework.

Quality of experience evaluation under QoS-aware mobility mechanisms

Next generation wireless networks will encompass a wide range of heterogeneous technologies in the radio access part. In such networks, the all-IP paradigm has been identified as a promising solution that will contribute benefits by providing IP-based transport through the radio and core network parts. However, this concept requires a precise management of the userpsilas mobility, especially in order to preserve userpsilas quality of service (QoS) throughout the sessionpsilas lifetime. The aim of this paper is to evaluate the quality of experience (QoE) that users perceive when the different QoS-aware mobility management strategies adopted in the AROMA project are applied. A real-time testbed that provides end-to-edge QoS in all-IP heterogeneous wireless access networks has been employed to obtain QoE results that hardly could be obtained by means of simulations.

TVWS indoor measurements for HetNets

In this paper the results of intensive measurement campaigns performed inside the buildings in two locations (Poznań, Poland and Barcelona, Spain) are presented and analyzed to investigate their potential in the generation of digital indoor radio environment maps. The existence of such detailed and stable maps will allow for further definition of the allowed transmit power of small cell transceivers operating within indoor heterogeneous networks and making use of TeleVision White Spaces (TVWS). The analysis concentrates on the stability and repeatability of the measured values both over time and location, as key elements enabling the creation of aforementioned digital maps.

An all-IP heterogeneous wireless testbed for RAT selection and e2e QoS evaluation

In this paper, we present an all-IP heterogeneous wireless testbed for radio access technologies (RAT) selection and end-to-end (e2e) quality of service (QoS) evaluation. Presented testbed includes three different radio access networks (RANs): UTRAN, GERAN, and WLAN; and the core network (CN) based on DiffServ technology and multiprotocol label switching (MPLS). As an example two RAT selection algorithms implemented in the testbed, network-controlled cell-breathing (NCCB) and fittingness factor are described and analyzed in more details. The paper provides also simple case study that validates and compares both mentioned algorithms in a basic heterogeneous environment using the presented testbed.

A beyond 3G real-time testbed for an All-IP heterogeneous network

This paper describes a real-time testbed emulating an all-IP B3G (Beyond 3rd Generation) network that includes UTRAN, GERAN, and WLAN emulation and the corresponding common core network based on DiffServ (Differentiated Services) technology and MPLS (Multiprotocol Label Switching). In such a complex scenario, considering real user applications and end-to-end (e2e) QoS, it is convenient to develop emulation platforms, where algorithms and applications can be tested in realistic conditions, not achievable by means of non-real-time simulations. Presented testbed will be used to evaluate three main objectives: to test the e2e QoS experienced by a user in a heterogeneous mobile environment with IP connectivity, to test and validate specific algorithms and mechanisms, and to evaluate real implementations of some subsystems.

Real-time emulation of RRM strategies for UMTS bearer services

This paper describes the implementation and the achieved capabilities of a real-time UMTS demonstrator developed within the framework of the IST ARROWS (advanced radio resource management on wireless services) project. Among the main goals of the ARROWS demonstrator are the evaluation of radio resource management (RRM) strategies in a UMTS network and the analysis of the impact that these strategies have on the end-to-end behaviour of multimedia applications with quality of service (QoS) requirements. The demonstrator platform is built over a network of personal computers and copes with the real-time restrictions imposed by the emulation of UMTS transport bearers. After providing a brief description of the developed HW/SW platform, the different approaches taken to emulate the main functions included in the test-bed are described, together with some of the achieved capabilities in terms of implemented RRM algorithms, supported scenarios, lower layer emulation and included services and applications with QoS requirements.

A generic radio channel emulator to evaluate higher layer protocols in a CDMA system

Currently, we are involved in the standardisation process to specify the next mobile system generation. A wideband code division multiple access (WCDMA) system is considered in most of the region versions. It would be very useful to count on a radio channel emulator which allows one to evaluate higher layers protocols within this context. This paper presents a radio channel emulator developed for a code division multiple access (CDMA) based system. Its versatility and low complexity have been exposed, and the validation process to check the model accuracy has also been shown for this system as an example.

Implementation of Cognitive Radio Networks to evaluate spectrum management strategies in real-time

This paper illustrates a Universal Software Radio Peripheral (USRP)-based real-time testbed that is able to evaluate different spectrum management solutions that exploit the Cognitive Radio (CR) paradigm. The main objective of this testbed is to provide an accurate and realistic platform by which the performance of innovative spectrum management solutions for a wide set of scenarios and use cases in the context of Opportunistic Networks (ONs) and Cognitive Radio Networks (CRNs) can be entirely validated and assessed before their implementation in real systems. Real-time platforms are essential to carry out significant studies and to accurately assess the performance of innovative solutions before their implementation in the real world. This work provides a comprehensive description of the testbed, highlighting many interesting implementation details and illustrating its applicability for different studies that rely on the CR paradigm. Then, a particular application in a realistic Digital Home (DH) scenario is also illustrated, which allows demonstrating the effectiveness of the real-time testbed and assessing its practicality in terms of user-perceived end-to-end Quality of Experience (QoE) in a realistic environment.