Aggregate information efficiency and packet delay in wireless ad hoc networks

Orientador: Paulo CardieriDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de ComputaçãoResumo: As características inerentes às redes ad hoc sem fio como, por exemplo, a ausência de uma infraestrutura pré-determinada e a possibilidade de enlaces de múltiplos saltos, exigem medidas de desempenho que capturem as inter-relações entre as camadas física, de acesso ao meio e de enlace. Com base na métrica eficiência de informação agregada e no atraso de pacote, as relações de compromisso entre diversas variáveis da rede são analisadas neste trabalho. É mostrado também que a possibilidade de retransmissão para pacotes recebidos em erro pode melhorar o desempenho da rede. Considerando sistemas em que uma parcela dos enlaces ativos estão em situação de outage, observa-se que os melhores resultados ocorrem para probabilidade de ocorrência de outage na rede entre 50% e 80%. Para enlaces de múltiplos saltos, os resultados mostram que é preferível ter transmissões formadas por um número maior de saltos, com receptores que exijam uma maior potência mínima para a recepção de um pacote.Abstract: The inherent characteristics of ad hoc networks such as the lack of infrastructure and the possibility of multi-hop links require performance measures that capture the relationships between physical layer, medium access control and link layer. Based on aggregate information efficiency metric and packet delay, trade-offs involving several networks variables are analyzed. It is shown that the possibility of packet retransmission improves the network performance. In networks where part of the active links is in outage, the best results are found for outage probabilities between 50% and 80%. Concerning multi-hop links, the results show that it is preferable having transmissions with a greater number of hops formed by receptor terminals that require higher threshold powers for a packet reception.MestradoTelecomunicações e TelemáticaMestre em Engenharia Elétric

Análise da vazão espacial em redes de interferência

Orientador: Paulo CardieriTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: O Resumo poderá ser visualizado no texto completo da tese digitalAbstract: The complete Abstract is available with the full electronic documentDoutoradoTelecomunicações e TelemáticaDoutor em Engenharia Elétric

Analysis of the spatial throughput in interference networks

Abstract In this thesis we study the spatial throughput of interference-limited wireless networks from different perspectives, considering that the spatial distribution of nodes follows a 2-dimensional homogeneous Poisson point process and transmitters employ Gaussian point-to-point codes. To carry out this analysis, we model the interrelations between network elements using concepts from stochastic geometry, communication theory and information theory. We derive closed-form equations to compute/approximate the performance metric that is chosen to evaluate the system for each given specific scenario. Our first contribution is an investigation about whether it is preferable to have a large number of short single-hop links or a small number of long hops in multi-hop wireless networks, using a newly proposed metric denominated aggregate multi-hop information efficiency. For single-hop systems, we revisit the transmission capacity framework to study medium access protocols that use asynchronous transmissions and allow for packet retransmissions, showing when a carrier sensing capability is more suitable than synchronous transmissions, and vice-versa. We also cast the effective link throughput and the network spatial throughput optimization problems to find the combination of medium access probability, coding rate and maximum number of retransmissions that maximize each metric under packet loss and queue stability constraints, evincing when they do (and do not) have the same solution. Furthermore we analyze the expected maximum achievable sum rates over a given area – or spatial capacity – based on the capacity regions of Gaussian point-to-point codes for two decoding rules, namely (i) treating interference as noise (IAN) and (ii) jointly detecting the strongest interfering signals treating the others as noise (OPT), proving the advantages of the second. We additionally demonstrate that, when the same decoding rule and network density are considered, the spatial-capacity-achieving scheme always outperforms the spatial throughput obtained with the best predetermined fixed rate strategy. With those results in hand, we discuss general guidelines on the construction of ad hoc adaptive algorithms that would improve the information flow throughout the interference network, respecting the nodes’ internal and external constraints.Tiivistelmä Tässä työssä tutkitaan häiriörajoitteisten langattomien verkkojen tila-alueen suorituskykyä, olettaen verkkosolmujen sijoittuvan 2-ulotteisen Poissonin pisteprosessin mukaisesti, sekä olettaen lähettimien hyödyntävän Gaussisia pisteestä-pisteeseen -koodeja. Suorituskykyanalyysi pohjautuu stokastiseen geometriaan, tietoliikenneteoriaan sekä informaatioteoriaan. Suljetun muodon suorituskyky-yhtälöitä hyödyntäen arvioidaan suorityskykymetriikoita eri skenaarioissa. Työn aluksi esitetään uusi monihyppyverkkojen informaatiotehokkuuteen perustuva metriikka. Sen avulla voidaan tutkia onko tehokkaampaa käyttää useita lyhyen hypyn linkkejä vai pienempää määrää pidempien hyppyjen linkkejä. Yhden hypyn verkoissa tutkitaan mediaanpääsyprotokollia asynkronisissa verkoissa pakettien uudelleenlähetykseen perustuen ja verrataan tätä synkroniseen lähetykseen ilman vapaan kanavan tunnistusmekanismia. Työssä tutkitaan myös linkin efektiivisen suorituskyvyn ja verkon tila-alueen suorituskyvyn optimointia, jotta sopiva yhdistelmä mediaan pääsyn todennäköisyydelle, koodausnopeudelle ja uudelleenlähetysten maksimilukumäärälle löytyisi ja samalla maksimoisi jokaisen käytetyn metriikan ehdollistettuna paketin menetyksille ja jonon stabiilisuudelle. Lisäksi arvioidaan maksimaalista odotettavaa nettosiirtonopeutta tietyllä alueella, eli tila-alueen kapasiteettia, Gaussimaisen pisteestä-pisteeseen koodien kapasiteettialueisiin perustuen kahta eri dekoodaussääntöä hyödyntäen: (i) olettaen häiriön olevan kohinaa tai (ii) ilmaisemalla voimakkaimmat häiriösignaalit ja olettaen muiden olevan kohinaa. Jälkimmäinen osoittautui tehokkaammaksi menetelmäksi. Työssä osoitetaan myös, että samalla dekoodaussäännöllä ja verkon tiheydellä tila-alueen kapasiteetin saavuttava menetelmä on aina tehokkaampi kuin tavanomainen tila-alueen suorituskykyyn perustuva kiinteän siirtonopeuden menetelmä. Saavutettujen tulosten valossa työssä esitetään yleisiä suunnittelumenetelmiä mukautuville ad hoc -algoritmeille, joiden avulla voidaan parantaa tiedonsiirtoa häiriörajoitteisissa verkoissa, ehdollistettuna verkon solmujen sisäisille ja ulkoisille rajoitteille

Wireless-powered communication networks with random mobility

Abstract In this paper, we consider a wireless-powered communication network (WPCN), where an energy-limited multi-antenna information source, powered by a dedicated power beacon, communicates with a mobile user (MU). The MU is equipped with a single-antenna and its mobility is characterized by the well-known random waypoint mobility model. To gain the advantages with the use of multiple antennas at the source, we adopt two popular multiple-antenna transmission schemes, namely maximal-ratio transmission (MRT) and transmit antenna selection (TAS). Differently from previous works which considered only static scenarios, this paper aims to investigate wireless power and information transfer in the scenario with a random mobile user under Nakagami-$m$ fading. It is noteworthy that a special case of our analysis, i.e., the Rayleigh fading case, has not been examined in the literature as well, which enhances the contribution value of the proposed analysis. Considering both MRT and TAS schemes, closed-form expressions for the outage probability, average delay-limit throughput, average delay-tolerant throughput, average bit error rate (BER), and throughput under average BER constraint are derived. The analysis quantifies the impact of the mobility and propagation environments, which are characterized by the path-loss exponent and multipath parameter for the PB-AP link and AP-MU link, on the performance of a WPCN. The analytical results are compared with Monte-Carlo simulations in order to validate the analysis and provide useful insights on the impact of different parameters on the system performance

Detection of appliance utilization patterns via dimensionality reduction

Abstract This paper focuses on the detection of utilization patterns in electricity residential consumption, which are closely related to the occupant characteristics (e.g. number, age, occupancy, and social class). Our goal is to identify groups of appliances that are often used together via their statistically relatedness. This relation might be obvious (as in TV and Home Theater), or not. The results can be used, for example, to guide a recommendations letter from the energy supplier to the final user, suggesting specific change of habits in order to improve the residence’s energy efficiency. We propose here a methodology for identifying patterns from a large sets of system status, which is a computationally hard task defined in ℝ n with n being the number of appliances involved. The approach consist in the following steps: (i) the Principal Component Analysis method is employed to reduce the set dimensionality to ℝ 3 with explained variance from 68% to 90% to guarantee minimum information loses, (ii) the k-means method to clustering appliances into different groups and (iii) the elbow method was used to define the best number of clusters for each house with explained variance of at least 93% and reaching more than 99% for the best k. Numerical tests using the UK-DALE dataset are presented to show the effectiveness of the proposed solution. The main contribution of this work is a method with low computational cost that requires no other information than a large set of reliable system status (binary vectors) to reveal utilization patterns in the residence