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- Interference study between wireless microphone systems and TV white space devicesPublication . Dionísio, Rogério Pais; Marques, Paulo; Rodriguez, JonathanThis work focus on a coexistence study between wireless microphone systems and secondary users of the TV White Spaces, using a Monte-Carlo methodology. Exclusion areas around wireless microphone receivers, for co-channel and adjacent channel interference, are computed, considering indoor and outdoor scenarios. Using this methodology, impact and tendencies of several parameters over the probability of interference are analyzed, like spectral channel spacing, separation distance and propagation scenario. As an example, for outdoor scenarios, the spectral spacing between primary system and secondary users, ranging from 0 MHz (co-channel operation) to 16 MHz (2 DVB-T channels) results in a protection distance of 13.9 km and 2.2 km, respectively.
- Implementation of a communication protocol between a geo-location database and TV white space devicesPublication . Dionísio, Rogério Pais; Ribeiro, Jorge Miguel Afonso; Paulo, MarquesTelevision White Spaces (TVWS) are a spectral opportunity, for secondary users of the spectrum to deliver broadband access to rural areas. Most of the approaches now under test worldwide use a geo-location database to inform secondary users of the available channels, and avoid interference with primary users of the spectrum. The secondary network should follow a approach capable to communicate with a geo-location spectrum database, to store and retrieve information on spectrum occupancy, location of DVB-T broadcast towers and wireless microphones, maximum EIRP of secondary White Space devices (WSDs), sensing activity and other technical parameters. One group from the Internet Engineering Task Force (IETF) is presently working on the definition of a protocol to access white spaces databases – PAWS. The IETF draft protocol was chosen and considered flexible enough to be adapted for the CREW-TV project model and requirements, since it is more comprehensive and less specific on details than other proposals.
- ETSI opportunistic spectrum sharing technology for (TV) white spacesPublication . Mueck, Markus Dominik; Sato, Naotaka; Sun, Chen; Freda, Martino; Ojanen, Pekka; Zhou, Dong; Xiao, Junfeng; Dionísio, Rogério Pais; Marques, PauloThis chapter provides an overview on European Telecommunications Standards Institute (ETSI) activities related to opportunistic spectrum sharing technology with a specific focus on (TV) white spaces. Key use cases are outlined and a novel approach for a coordinated and an uncoordinated approach for accessing the spectrum resource is given. A spectrum coordinator is indeed introduced in order to handle resource management. Furthermore, database system design and inter-database communication solutions are discussed as they are introduced by ETSI. Finally, various sensing mechanisms are detailed, which allow to monitor the radio environment and to feed decision-making components correspondingly.
- Evaluation of blind sensing techniques in multiple wireless microphones environmentsPublication . Dionísio, Rogério Pais; Marques, Paulo; Ribeiro, José CarlosThis work focuses on the evaluation of blind sensing techniques for the detection of multiple wireless microphones in the UHF band, by means of simulation. The metrics used for the comparisons include probability of detection, probability of false alarm and minimum SNR detected for a given observation time. As an example, simulation results showed that blind detection algorithms can sense multiple wireless microphone signals with SNR = -19 dB, in a Rayleigh channel environment, considering 100 ms sensing time, 90 % probability of detection and 10 % probability of false alarm. In these conditions, blind detection techniques suffer maximum SNR degradation of 3.5 dB, as compared with single wireless microphone scenarios.
- Plataforma de agendamento de espectro para equipamentos profissionaisPublication . Esteves, Hugo; Duarte, Pedro José; Marques, Paulo; Dionísio, Rogério PaisCom o switch off da televisão analógica libertou-se uma importante e útil parte do espectro que possui características que o tornam bastante importante e útil para utilização por outros sistemas radiofrequência. Mas é também nesta banda de espectro que funcionam inúmeros dispositivos sem fios, de forma anárquica, e sem qualquer tipo de regulamentação. Desta forma tornou-se necessário regular estes aparelhos. Neste artigo propõe-se uma plataforma que possibilita a regulamentação e correcta utilização destes dispositivos que operam anarquicamente nestas frequências.
- Affordable LTE network benchmarking based on transport fleetsPublication . Dionísio, Rogério Pais; Marques, Paulo; Marques, Hugo; Alves, Tiago Ferreira; Pereira, Luis Miguel Cardoso; Silva, Fernando; Ribeiro, Jorge Miguel AfonsoTo gain competitive advantage in today’s mobile market, cellular network testing, monitoring and improving customer experience is crucial. Today independent benchmarking companies are hired by mobile operators to run drive tests in a certain geographical areas. The high cost for running these tests results in a low frequency of execution, typically this benchmarking is executed no more than two or three times per year, which is not sufficient to follow the dynamics of an LTE network in a dense urban area. The majority of the drive testing costs come from the car, driver, and the in-car technician. Another approach is to take advantage of existing transportation companies to carry on network benchmarking services to Mobile Network Operators. Unattended measurement nodes can be deployed in existing transportation fleets without the need for dedicated field personnel, reducing the cost of testing up to 70%. This demo uses nodes placed in buses, available in several cities in Europe, to create and validate an automatic LTE network benchmark. The tool allows an easy comparative analyses of mobile network quality of Service and quality of experience parameters based on the operators raw data.
- Experimental assessment of WiFi coordination strategies using radio environment mapsPublication . Dionísio, Rogério Pais; Marques, Paulo; Alves, Tiago Ferreira; Ribeiro, Jorge Miguel AfonsoThe rapidly increasing popularity of WiFi has created unprecedented levels of congestion in the unlicensed frequency bands, especially in densely populated urban areas. This results mainly because of the uncoordinated operation and the unmanaged interference between WiFi access points. In this context, the main objective of this experiment is to assess the benefit of a coordinated management of radio resources in dense WiFi networks for both 2.4 GHz and 5 GHz bands, using Radio Environment Maps (REM). This experiment has used the w-iLab.t test environment and the portable test-bed provided by iMINDS for indoor scenarios. It was shown that REMs can detect the presence of interfering links on the network (co-channel or adjacent channel interference), and a suitable coordination strategy can use this information to reconfigure Access Points (AP) channel assignment and re-establish the client connection. The coordination strategy almost double the capacity of a WiFi link under strong co–channel interference, from 6.8 Mbps to 11.8 Mbps, increasing the aggregate throughput of the network from 58.7 Mbps to 71.5 Mbps. However, this gain comes with the cost of a relatively high-density network of spectrum sensors, increasing the cost of deployment. The technique of AP handoff was tested to balance the load form one AP to another, although the aggregate throughput is lower after load balancing. REMs are also capable of detecting coverage holes on the network, and a suitable Radio Resource Management strategy use this information to reconfigure the APs transmit power to reestablish the client connection and increase the throughput of the overloaded AP, at a cost of diminishing the aggregate throughput of the network. The insights coming out from this experiment helped to understand the opportunities and limitations of WiFi coordination strategies in realistic scenarios.
- Experimental assessment of RRM techniques in 5 GHz dense WiFi networks using REMsPublication . Dionísio, Rogério Pais; Marques, Paulo; Alves, Tiago Ferreira; Ribeiro, Jorge Miguel AfonsoThe increasing acceptance of WiFi has created unprecedented levels of congestion in the unlicensed frequency bands, especially in densely populated areas. This results mainly because of the unmanaged interference and uncoordinated op- eration between WiFi access points. Radio Environment Maps (REM) have been suggested as a support for coordination strategies that optimize the overall WiFi network performance. In this context, the main objective of this experiment is to assess the benefit of a coordinated management of radio resources in dense WiFi networks at 5 GHz band, using REMs for indoor scenarios. It was shown that REMs can detect the presence of interfering links on the network or coverage holes, and a suitable coordination strategy can use this information to reconfigure Access Points (AP) channel assignment and re-establish the client connection, at a cost of diminishing the aggregate throughput of the network. The technique of AP hand-off was tested to balance the load from one AP to another. Using REMs, the Radio Resource Management (RRM) strategy could reconfigure the network to optimize the client distribution among available APs. Although the aggregate throughput is lower after load balancing, the RRM could increase the throughput of the overloaded AP.
- Sistema eletrónico para a monitorização remota da qualidade do ar e ruído na indústria cerâmicaPublication . Marques, Paulo; Dionísio, Rogério PaisNo âmbito da "campanha Cerâmica", promovida pelo Instituto de Desenvolvimento e Inspeçcão das Condições de Trabalho (IDICT), foi desenvolvido o sistema SEMIC. O SEMIC é uma ferramenta eletrónica para monitorização remota de parâmetros ambientassem postos de trabalho. Depois de instalado numa unidade fabril, o SEMIC permite realizar medidas de uma forma contínua e sem intervenção humana. O SEMIC integra numa única solução a monitorização do empoeiramento, temperatura, humidade relativa e nível de ruído acústico (intensidade e frequência), de forma a facilitar o trabalho dos técnicos de higiene e segurança.
- Some initial results and observations from a series of trials within the Ofcom TV white spaces pilotPublication . Holland, Oliver; Ping, Shuyu; Sastry, Nishanth; Chawdhry, Pravir; Chareau, Jean-Marc; Bishop, James; Xing, Hong; Taskafa, Suleyman; Aijaz, Adnan; Bavaro, Michele; Viaud, Philippe; Pinato, Tiziano; Anguili, Emanuele; Akhavan, Mohammad Reza; McCann, Julie; Gao, Yue; Qin, Zhijin; Zhang, Qianyun; Knopp, Raymond; Kaltenberger, Florian; Nussbaum, Dominique; Dionísio, Rogério Pais; Ribeiro, José Carlos; Marques, Paulo; Hallio, Juhani; Jakobsson, Mikko; Auranen, Jani; Ekman, Reijo; Kokkinen, Heikki; Paavola, Jarkko; Kivinen, Arto; Solc, Tomaz; Mohorcic, Mihael; Tran, Ha-Nguyen; Ishizu, Kentaro; Matsumura, Takeshi; Ibuka, Kazuo; Harada, Hiroshi; Mizutani, KeiichiTV White Spaces (TVWS) technology allows wireless devices to opportunistically use locally-available TV channels enabled by a geolocation database. The UK regulator Ofcom has initiated a pilot of TVWS technology in the UK. This paper concerns a large-scale series of trials under that pilot. The purposes are to test aspects of white space technology, including the white space device and geolocation database interactions, the validity of the channel availability/powers calculations by the database and associated interference effects on primary services, and the performances of the white space devices, among others. An additional key purpose is to perform research investigations such as on aggregation of TVWS resources with conventional resources and also aggregation solely within TVWS, secondary coexistence issues and means to mitigate such issues, and primary coexistence issues under challenging deployment geometries, among others. This paper provides an update on the trials, giving an overview of their objectives and characteristics, some aspects that have been covered, and some early results and observations.