The popularity of wireless communication has increased substantially over the last decade, due to mobility support, flexibility and ease of deployment. Among next generation of mobile communication technologies, Ad Hoc networking plays an important role, since it can stand alone as private network, become a part of public network, either for general use or as part of disaster management scenarios. The performance of multihop Ad Hoc networks is heavily affected by interference, mobility, limited shared bandwidth, battery life, error rate of wireless media, and the presence of hidden and exposed terminals. The scheduler and the Medium Access Control (MAC) play a vital role in providing Quality of Service (QoS) and policing delay, end-to-end throughput, jitter, and fairness for user application services. This project aims to optimise the usage of the available limited resources in terms of battery life and bandwidth, in order to reduce packet delivery time and interference, enhance fairness, as well as increase the end-to-end throughput, and increase the overall network performance. The end-to-end throughput of an Ad Hoc network decays rapidly as the hop count between the source and destination pair increases and additional flows injected along the path of an existing flow affects the flows arriving from further away; in order to address this problem, the thesis proposes a Hop Based Dynamic Fair Scheduler that prioritises flows subject to the hop count of frames, leading to a 10% increase in fairness when compared to a IEEE 802.11b with single queue. Another mechanism to improve network performance in high congestion scenarios is network-aware queuing that reduces loss and improve the end-to-end throughput of the communicating nodes, using a medium access control method, named Dynamic Queue Utilisation Based Medium Access Control (DQUB-MAC). This MAC provides higher access probability to the nodes with congested queue, so that data generated at a high rate can be forwarded more effectively. Finally, the DQUB-MAC is modified to take account of hop count and a new MAC called Queue Utilisation with Hop Based Enhanced Arbitrary Inter Frame Spacing (QU-EAIFS) is also designed in this thesis. Validation tests in a long chain topology demonstrate that DQUB-MAC and QU-EAIFS increase the performance of the network during saturation by 35% and 40% respectively compared to IEEE 802.11b. High transmission power leads to greater interference and represents a significant challenge for Ad Hoc networks, particularly in the context of shared bandwidth and limited battery life. The thesis proposes two power control mechanisms that also employ a random backoff value directly proportional to the number of the active contending neighbours. The first mechanism, named Location Based Transmission using a Neighbour Aware with Optimised EIFS for Ad Hoc Networks (LBT-NA with Optimised EIFS MAC), controls the transmission power by exchanging location information between the communicating nodes in order to provide better fairness through a dynamic EIFS based on the overheard packet length. In a random topology, with randomly placed source and destination nodes, the performance gain of the proposed MAC over IEEE 802.11b ranges from approximately 3% to above 90% and the fairness index improved significantly. Further, the transmission power is directly proportional to the distance of communication. So, the performance is high and the durability of the nodes increases compared to a fixed transmission power MAC such as IEEE 802.11b when communicating distance is shorter. However, the mechanism requires positional information, therefore, given that location is typically unavailable, a more feasible power control cross layered system called Dynamic Neighbour Aware – Power controlled MAC (Dynamic NA -PMAC)is designed to adjust the transmission power by estimating the communicating distance based on the estimated overheard signal strength. In summary, the thesis proposes a number of mechanisms that improve the fairness amongst the competing flows, increase the end-to-end throughput, decrease the delay, reduce the transmission power in Ad Hoc environments and substantially increase the overall performance of the network.

As redes de sensores sem fio (wsns) têm ganhado cada vez mais espaço no monitoramento e controle de processos na indústria. Dentro destas redes, os dispositivos são alimentados por baterias, e a comunicação é feita por radiofrequência. Por conta disto, os rádios dos dispositivos são responsáveis por consumir boa parte da energia armazenada nas suas baterias, e a comunicação dos dispositivos está sujeita à interferência provinda de outras redes e do maquinário industrial. Para sanar estes problemas podem ser empregadas técnicas de controle de potência de transmissão (cpt). Existem diversas técnicas de cpt na literatura, visando os mais diversos objetivos, desde economia de energia e redução de interferência, até controle da topologia da rede. Este trabalho apresenta uma proposta de emprego de (cpt) em uma rede de sensores sem fio através da utilização de controladores proporcionais-integrais (pi). Juntamente com a técnica proposta, são apresentados um procedimento para projeto dos controladores e alguns algoritmos desenvolvidos para o caso ideal e para os casos com saturação dos níveis de potência disponíveis. Este trabalho se diferencia dos trabalhos encontrados na literatura por apresentar uma técnica de controle linear e que depende apenas de informações já disponíveis em cada dispositivo cuja potência será ajustada. Deste modo, esta técnica pode ser empregada em conjunto com protocolos industriais mais restritivos quanto às informações que podem ser trocadas nas mensagens. Além disso, esta técnica reduz ainda mais o consumo e a interferência por evitar transmissões desnecessárias. A proposta apresentada foi validada através de simulações e de um experimento com dispositivos WirelessHART reais, apresentando bons resultados e provando que é possível controlar a potência sem a necessidade das informações extras. / Wireless sensor networks (wsns) are being increasingly adopted in monitor and control tasks in the industry. The devices within these networks are battery-powered, and they communicate through radio frequency. Therefore the radios of the devices account for the most of the consumption of the energy stored in the batteries, and the devices’ communication is subject to interference from other networks and industrial machinery. Transmission power control (tpc) techniques can be employed to cope with these problems. There are several tpc techniques in the literature, aiming at a wide range of objectives, from energy saving and interference reduction, to network topology control. This work presents the proposal of a (tpc) technique in a wireless sensor network that works by employing proportional-integral (pi) controllers. Besides the technique itself, a procedure is presented to design the controllers along some algorithms developed to the ideal case, and the case when there is saturation in the available power levels. This work, unlike the other works found in the literature, presents a linear technique that depends only on information that is already available in each device whose power needs to be adjusted. Therefore, the proposed technique can be employed together with more restrictive industrial protocols that limit the information that can be exchanged in the messages. Besides, it further reduces the power consumption and the interference by avoiding unnecessary transmissions. The proposal was validated through simulations and an experiment using real WirelessHART devices, presenting good results and proving that it is possible to adjust the transmission power without necessarily using the extra information.

As redes de sensores sem fio (wsns) têm ganhado cada vez mais espaço no monitoramento e controle de processos na indústria. Dentro destas redes, os dispositivos são alimentados por baterias, e a comunicação é feita por radiofrequência. Por conta disto, os rádios dos dispositivos são responsáveis por consumir boa parte da energia armazenada nas suas baterias, e a comunicação dos dispositivos está sujeita à interferência provinda de outras redes e do maquinário industrial. Para sanar estes problemas podem ser empregadas técnicas de controle de potência de transmissão (cpt). Existem diversas técnicas de cpt na literatura, visando os mais diversos objetivos, desde economia de energia e redução de interferência, até controle da topologia da rede. Este trabalho apresenta uma proposta de emprego de (cpt) em uma rede de sensores sem fio através da utilização de controladores proporcionais-integrais (pi). Juntamente com a técnica proposta, são apresentados um procedimento para projeto dos controladores e alguns algoritmos desenvolvidos para o caso ideal e para os casos com saturação dos níveis de potência disponíveis. Este trabalho se diferencia dos trabalhos encontrados na literatura por apresentar uma técnica de controle linear e que depende apenas de informações já disponíveis em cada dispositivo cuja potência será ajustada. Deste modo, esta técnica pode ser empregada em conjunto com protocolos industriais mais restritivos quanto às informações que podem ser trocadas nas mensagens. Além disso, esta técnica reduz ainda mais o consumo e a interferência por evitar transmissões desnecessárias. A proposta apresentada foi validada através de simulações e de um experimento com dispositivos WirelessHART reais, apresentando bons resultados e provando que é possível controlar a potência sem a necessidade das informações extras. / Wireless sensor networks (wsns) are being increasingly adopted in monitor and control tasks in the industry. The devices within these networks are battery-powered, and they communicate through radio frequency. Therefore the radios of the devices account for the most of the consumption of the energy stored in the batteries, and the devices’ communication is subject to interference from other networks and industrial machinery. Transmission power control (tpc) techniques can be employed to cope with these problems. There are several tpc techniques in the literature, aiming at a wide range of objectives, from energy saving and interference reduction, to network topology control. This work presents the proposal of a (tpc) technique in a wireless sensor network that works by employing proportional-integral (pi) controllers. Besides the technique itself, a procedure is presented to design the controllers along some algorithms developed to the ideal case, and the case when there is saturation in the available power levels. This work, unlike the other works found in the literature, presents a linear technique that depends only on information that is already available in each device whose power needs to be adjusted. Therefore, the proposed technique can be employed together with more restrictive industrial protocols that limit the information that can be exchanged in the messages. Besides, it further reduces the power consumption and the interference by avoiding unnecessary transmissions. The proposal was validated through simulations and an experiment using real WirelessHART devices, presenting good results and proving that it is possible to adjust the transmission power without necessarily using the extra information.

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / Ericsson Brasil / O aumento da demanda por serviÃos ricos em multimÃdia e a escassez do espectro eletromagnÃtico tÃm motivado a pesquisa de tecnologias capazes de aumentar a capacidade de sistemas sem fio sem requerer espectro adicional. Nesse contexto, comunicaÃÃes Dispositivo-a-Dispositivo (D2D, do inglÃs Device-to-Device) representam uma tecnologia promissora. Ao permitir comunicaÃÃo direta e de baixa potÃncia entre os dispositivos, comunicaÃÃes D2D levam a um maior e mais inteligente reuso dos recursos de rÃdio, permitindo um descongestionamento da rede de transporte de dados. Como resultado, a capacidade total do sistema e especialmente a eficiÃncia espectral sÃo aumentadas; e a proximidade entre os dispositivos permitem transferÃncias de dados com baixo atraso e altas taxas de dados, sem requerer potÃncia extra da bateria dos dispositivos. Entretanto, com o objetivo de tornar real os potenciais ganhos de comunicaÃÃes D2D como uma rede secundÃria da celular (primÃria), algumas questÃes chave precisam ser controladas. Assumindo que os dispositivos se comunicando estÃo cientes um do outro, a condiÃÃo do enlace (canal) deve ser avaliada. Caso seja benÃfica, tÃcnicas de GestÃo de recursos de rÃdio (RRM, do inglÃs Radio Resource Management) sÃo empregadas para que a interferÃncia co-canal causada nos dispositivos celulares seja mitigada. Tais tÃcnicas podem ser resumidas como: agrupamento, seleÃÃo de modo e controle de potÃncia. Nessa dissertaÃÃo, eu foco a minha atenÃÃo para RRM em comunicaÃÃes D2D subjacentes a redes LTE, e para as principais tÃcnicas de RRM para mitigar a interferÃncia co-canal. Objetivando a reduÃÃo da interferÃncia intra-celular e na melhoria da eficiÃncia espectral, eu formulo um problema conjunto de agrupamento e controle de potÃncia. Entretanto, devido à sua complexidade eu proponho mÃtodos sub-Ãtimos para agrupar usuÃrios celulares e D2D com o objetivo de minimizar a interferÃncia intra-celular, levando em conta a ortogonalidade espacial entre os usuÃrios que compartilham o recurso. AlÃm disso, eu analiso mÃtodos para decidir se um candidato D2D deveria se comunicar diretamente ou de modo convencional atravÃs da estaÃÃo rÃdio-base (eNB, do inglÃs Evolved Node B). Os resultados mostram que comunicaÃÃes D2D conseguem melhorar a eficiÃncia espectral do sistema e que a maioria dos ganhos pode ser alcanÃada agrupando de forma adequada os usuÃrios para compartilhar recursos baseando-se em projeÃÃes sucessivas e ortogonais, assim como combinando diferentes mÃtricas de compatibilidade espacial. AlÃm disso, nessa dissertaÃÃo eu argumento que tecnologias D2D podem ser usadas para aumentar ainda mais a eficiÃncia espectral e energÃtica se os parÃmetros chave dos algoritmos de RRM forem adequadamente estendidos para comunicaÃÃes D2D em mÃltiplos saltos. Especificamente, eu proponho um novo algoritmo distribuÃdo de controle de potÃncia baseado em maximizaÃÃo da utilidade que à capaz de equilibrar eficiÃncia espectral e energÃtica, enquanto leva em consideraÃÃo a seleÃÃo de modo e restriÃÃes na alocaÃÃo de recursos inerentes à integraÃÃo do ambiente celular-D2D. Os resultados numÃricos mostram que comunicaÃÃes D2D em mÃltiplos saltos combinadas com o algoritmo de controle de potÃncia proposto sÃo Ãteis nÃo apenas para colher os potenciais ganhos identificados na literatura, mas tambÃm para estender a cobertura de redes celulares. / The increasing demand for fast multimedia services and the scarcity of electromagnetic spectrum has motivated the research of technologies able to increase the capacity of wireless systems without requiring additional spectrum. In this context, Device-to-Device (D2D) communication represents a promising technology. By enabling direct and low-power communication among devices, D2D communication leads to an increased and intelligent spatial reuse of radio resources allowing to offload the data transport network. As a result, the overall system capacity and specially the spectral efficiency is increased; and the proximity between devices allows data transfer with low delays and high rates without requiring extra power from devicesâ batteries. However, in order to realize the potential gains of D2D communications as a secondary network of the cellular (primary) one, some key issues must be tackled. Assuming that the communicating devices are aware of each other, the actual link (channel) conditions must be evaluated. If beneficial, Radio Resource Management (RRM) techniques would be employed so that the co-channel interference caused in cellular devices would be mitigated. Such techniques may be summarized as: grouping, mode selection, and power control. In this thesis, I focus my attention on the RRM for D2D communications underlaying a Long Term Evolution (LTE)-like network, and the main RRM techniques to mitigate the co-channel interference. Aiming at the reduction of the intra-cell interference and at the improvement of spectral efficiency, I formulate a joint grouping and power allocation problem. However, due to its complexity I propose suboptimal methods to group cellular and D2D User Equipments (UEs) with the goal of minimizing intra-cell interference, taking into account spatial orthogonality between the UEs that share the same resources. In addition, I analyze methods to decide if D2D-capable UEs should communicate directly to one another or in the conventional way via the Evolved Node B (eNB). The results show that D2D communications can improve the spectral efficiency of the system and that most of this improvement can be achieved by suitably grouping the UEs for sharing resources based on successive orthogonal projections and matching different spatial compatibility metrics. Moreover, in this thesis I argue that D2D technology can be used to further increase the spectral and energy efficiency if the key D2D RRM algorithms are suitably extended to support network assisted multi-hop D2D communications. Specifically I propose a novel, distributed utility maximizing power control (PC) scheme that is able to balance spectral and energy efficiency while taking into account mode selection and resource allocation constraints that are important in the integrated cellular-D2D environment. The analysis and numerical results indicate that multi-hop D2D communications combined with the proposed PC scheme can be useful not only for harvesting the potential gains previously identified in the literature, but also for extending the coverage of cellular networks.

[pt] Este trabalho investiga o comportamento de três métodos de alocação de canais para Sistemas Móveis Celulares quando associados a três algoritmos de controle de potência distribuídos. Os objetivos desta associação são uma maior capacidade comparada à obtida com a aplicação isolada de alocação de canais, e uma melhor distribuição da Razão Sina- Interferência, através do uso otimizado da potência de transmissão. Resultados de simulações mostram que estes dois objetivos podem ser atingidos, mas com alguns custos. / [en] This work investigates the behavior if three channel allocation schemes for Mobile Cellular Systems, when associated to three different automatic uplink power control schemes. The two objectives sought with this association are improved capacity over the isoladed use of the allocation schemes, and a better distribuition of the Signal to Interference Ratio (SRI) due to an optimized use of transmission power. Simulation results show that indeed this can be achieved, but not without some costs.

No description available.

Fuel cost represents a significant operating expense for owners and fleet managers of hydraulic off-highway vehicles. Further, the upcoming Tier IV compliance for off-highway applications will create further expense for after-treatment and cooling. Solutions that help address these factors motivate fleet operators to consider and pursue more fuelefficient hydraulic energy recovery systems. Electrical hybridization schemes are typically complex, expensive, and often do not satisfy customer payback expectations. This paper presents a hydraulic energy recovery architecture to realize energy recovery and utilization through a hydraulic hydro-mechanical transformer. The proposed system can significantly reduce hydraulic metering losses and recover energy from multiple services. The transformer enables recovered energy to be stored in a high-pressure accumulator, maximizing energy density. It can also provide system power management, potentially allowing for engine downsizing. A hydraulic test stand is used in the development of the transformer system. The test stand is easily adaptable to simulate transformer operations on an excavator by enabling selected mode valves. The transformer’s basic operations include shaft speed control, pressure transformation control, and output flow control. This paper presents the test results of the transformer’s basic operations on the test stand, which will enable a transformer’s full function on an excavator.

With high date rates using Enhanced Uplink (EUL), a conventional signal to interference ratio (SIR) based power control algorithm may lead to a power rush due to self interference or incompatible SIR target [2]. Time division (TD) scheduling in Wideband Code Division Multiplex Access (WCDMA) is considered to be a key feature in achieving high user data rates. Unfortunately, power oscillation/peak is observed in time division multiplexing (TDM) at the transition between active and inactive transmission time intervals [1]. Therefore there is a need to revisit power control algorithms for different time division scheduling scenarios. The objective of power control in the context of this study is to minimize the required rise over thermal noise (RoT) for a given data rate, subject to the constraint that the physical layer control channel quality is sufficient (assuming that the dedicated physical control channel (DPCCH) SIR should not go below 3dB with a probability of at most 5%). Another goal is to minimize the local oscillation in power (power peaks) that may occur, for example due to transitions between active and inactive transmission time intervals. The considered hybrid power control schemes are: (1) non-parametric Generalized rake receiver SIR (GSIR) Inner Loop Power Control (ILPC) during active transmission time intervals + Received Signal Code Power (RSCP) ILPC during inactive transmission time intervals and (2) RSCP ILPC during active transmission time intervals + GSIR ILPC during inactive transmission time intervals. Both schemes are compared with pure GSIR and pure RSCP ILPC. Link level simulations with multiple users connected to a single cell show that: The power peak problem is obviously observed in GSIR + GSIR transmit power control (TPC), but in general it performs well in all time division scenarios studied. GSIR outperforms other TPC methods in terms of RoT, especially in the TU channel model. This is because it is good in combating instantaneously changed fading and accurately estimates SIR. Among all TPC methods presented, GSIR + GSIR TPC is best in maintaining the quality of the DPCCH channel. No power rush is observed when using GSIR + GSIR TPC. RSCP + RSCP eliminates the power peak problem and outperforms other TPC methods presented under the 3GPP Pedestrial A (pedA) 3km/h channel in terms of RoT. However, in general it is worse in maintaining the control channel’s quality than GSIR + GSIR TPC. GSIR + RSCP ILPC eliminates the power peak problem and out-performs GSIR power control in the scenario of 2 and 4 TDM high data rate (HDR) UE and 2 TDM HDR UE coexistence with 4 Code DivisionMultiplex (CDM) LDR UE, in the pedA 3km/h channel, in terms of RoT. However, the control channel quality is not maintained as well during inactive transmission time intervals. It is not recommended to use RSCP + GSIR TPC since it performs worst among these TPC methods for most of the cases in terms of RoT, even though it is the second best in maintaining the control channel quality. The power peak is visible when using RSCP + GSIR TPC. To maintain the control channel’s quality, a minimum SIR condition is always used on top of all proposed TPC methods. However, when there are several connected TDM HDR UEs in the cell, results indicates that it is challenging to meet the quality requirement on the control channels. So it may become necessary to limit the number of connected terminals in a cell in a time division scenario. / Med den höga datahastighet som Enhanced Uplink (EUL) medger kan en konventionell algoritm för effektkontroll baserad på signal to interference ratio (SIR) leda till effekthöjning beroende på självinterferens eller felaktigt SIR mål. Time division (TD) schedulering vid Wideband Code Division Multiple Access (WCDMA) anses vara en nyckelfunktion för att uppnå höga datahastigheter. I övergången mellan aktiv och inaktiv transmissionstidsintervall vid time division multiplexing (TDM) har effektoscillering/effektpeak observerats. Detta gör det nödvändigt att se över algoritmerna för effektkontroll vid olika scenarion av TD schedulering. Målet med effektkontrollen i denna studie är att minimera rise over thermal noise (RoT) för en given datahastighet givet begränsningen att kvaliteten på physical layer control channel är tillräcklig (beaktande att dedicated physical control channel (DPCCH) SIR inte understiger 3dB med en sannolikhet på som mest 5%). Ett annat mål är att minimera den lokala effektoscillationen (effektpeakar) som kan inträffa till exempel vid övergång mellan aktiv och inaktiv transmissionstidsintervall. De undersökta hybrida metoderna för effektkontroll är: (1) icke-parametrisk Generalized rake receiver SIR (GSIR) Inner Loop Power Control (ILPC) vid aktiv transmissionstidsintervall + Received Signal Code Power (RSCP) ILPC vid inaktiv transmissionstidsintervall och (2) RSCP ILPC under aktiv transmissionstidsintervall + GSIR ILPC under inaktiv transmissiontidsintervall. Båda metoderna jämförs med ren GSIR och ren RSCP ILPC. Länk nivå simulering med flera användare anslutna till en enda cell visar att: Problemet med effektpeakar observeras tydligt vid GSIR + GSIR transmit power control (TPC) men generellt sett presterar den bra i alla studerade TD scenarion. GSIR presterar bättre än andra TPC metoder beträffande RoT, speciellt i TU kanal modellen. Detta beror på att metoden är bra på att motverka momentant förändrad fading och med god precision estimerar SIR. Bland alla presenterade TPC metoder är GSIR + GSIR TPC den bästa på att behålla en god kvalitet på DPCCH kanalen. Ingen effekthöjning har observerats vid GSIR + GSIR TPC. RSCP + RSCP eliminerar problemet med effektpeakar och presterar bättre än andra TPC metoder presenterade under 3GPPs Pedestrial A (pedA) 3km/h kanal beträffande RoT. Dock är metoden generellt sett sämre på att behålla kontrollkanalens kvalitet än GSIR + GSIR TPC. GSIR + GSIR ILPC eliminerar problemet med effektpeakar och presterar bättre än GSIR power control i ett scenario med 2 och 4 TDM high data rate (HDR) UE och 2 TDM HDR UE tillsammans med 4 Code Division Multiplex (CDM) LDR UE i pedA 3km/h kanalen beträffande RoT. Dock kan inte kvaliteten på kontrollkanalen behållas i detta fall heller under inaktiv transmissionstidsintervall. Det är inte rekommenderat att använda RSCP + GSIR TPC eftersom den presterar sämst av alla TPC metoder beträffande RoT i de allra flesta fall. Till dess fördel är att den är den näst bästa på att behålla kvaliteten på kontrollkanalen. Effektpeakar har observerats när RSCP + GSIR TPC använts. För att behålla kontrollkanalens kvalitet används alltid en minimum SIR nivå ovanpå alla föreslagna TPC metoder. När det finns flera anslutna TDM HDR UEs i cellen indikerar resultaten att det är en utmaning att behålla kvalitetskraven på kontrollkanalen. På grund av detta kan det bli nödvändigt att begränsa antalet anslutna terminaler i en cell i ett TD scenario.

Future cellular networks, the so-called 5G, are expected to provide explosive data volumes and data rates. To meet such a demand, the research communities are investigating new wireless transmission technologies. One of the most promising candidates is in-band full-duplex communications. These communications are characterized by that a wireless device can simultaneously transmit and receive on the same frequency channel. In-band full-duplex communications have the potential to double the spectral efficiencywhen compared to current half duplex systems. The traditional drawback of full-duplex was the interference that leaks from the own transmitter to its own receiver, the so- called self-interference, which renders the receiving signal unsuitable for communication.However, recent advances in self-interference suppression techniques have provided high cancellation and reduced the self-interference to noise floor levels, which shows full-duplex is becoming a realistic technology component of advanced wireless systems. Although in-band full-duplex promises to double the data rate of existing wireless technologies, its deployment in cellular networks is challenging due to the large number of legacy devices working in half-duplex. A viable introduction in cellular networks is offered by three-node full-duplex deployments, in which only the base stations are full-duplex, whereas the user- or end-devices remain half-duplex. However, in addition to the inherent self-interference, now the interference between users, the user-to-user interference, may become the performance bottleneck, especially as the capability to suppress self-interference improves. Due to this new interference situation, user pairing and frequency channel assignment become of paramount importance, because both mechanisms can help to mitigate the user-to-user interference. It is essential to understand the trade-offs in the performance of full-duplex cellular networks, specially three-node full-duplex, in the design of spectral and energy efficient as well as fair mechanisms. This thesis investigates the design of spectral efficient and fair mechanisms to improve the performance of full-duplex in cellular networks. The novel analysis proposed in this thesis suggests centralized and distributed user pairing, frequency channel assignment and power allocation solutions to maximize the spectral efficiency and fairness in future full-duplex cellular networks. The investigations are based on distributed optimization theory with mixed integer-real variables and novel extensions of Fast-Lipschitz optimization. The analysis sheds lights on two fundamental problems of standard cellular networks, namely the spectral efficiency and fairness maximization, but in the new context of full-duplex communications. The results in this thesis provide important understanding in the role of user pairing, frequency assignment and power allocation, and reveal the special behaviourbetween the legacy self-interference and the new user-to-user interference. This thesis can provide input to the standardization process of full-duplex communications, and have the potential to be used in the implementation of future full-duplex in cellular networks. / <p>QC 20170403</p>

This thesis deals with the design of efficient transmission schemes forwireless interference networks, when certain channel state information(CSI) is available at the terminals.In wireless interference networks multiple source-destination pairsshare the same transmission medium for the communications. The signalreception at each destination is affected by the interference from unintendedsources. This may lead to a competitive situation that each sourcetries to compensate the negative effect of interference at its desired destinationby increasing its transmission power, while it in fact increasesthe interference to the other destinations. Ignoring this dependency maycause a significant waste of available radio resource. Since the transmissiondesign for each user is interrelated to the other users’ strategies, anefficient radio resource allocation should be jointly performed consideringall the source-destination pairs. This may require a certain amount ofCSI to be exchanged, e.g. through feedback channels, among differentterminals. In this thesis, we investigate such joint transmission designand resource allocation in wireless interference networks.We first consider the smallest interference network with two sourcedestinationpairs. Each source intends to communicate with its dedicateddestination with a fixed transmission rate. All terminals have the perfectglobal CSI. The power control seeks feasible solutions that properly assigntransmission power to each source in order to guarantee the successfulcommunications of both source-destination pairs. To avoid interference,the transmissions of the two sources can be orthogonalized. They canalso be activated non-orthogonally. In this case, each destination maydirectly decode its desired signals by treating the interference signals asnoise. It may also perform decoding of its desired signals after decodingand subtracting the interference signals sent from the unintendedsources. The non-orthogonal transmission can more efficiently utilize the  available channel such that the power control problem has solutions withsmaller transmission power in comparison with the orthogonal transmission.However, due to the randomness of fading effects, feasible powercontrol solutions may not always exist. We quantify the probability thatthe power control problem has feasible solutions, under a Rayleigh fadingenvironment. A hybrid transmission strategy that combines the orthogonaland non-orthogonal transmissions is then employed to use the smallesttransmission power to guarantee the communications in the consideredtwo-user interference network.The network model is further extended to the general K-user interferencenetwork, which is far more complicated than the two-user case. Thecommunication is conducted in a time-varying fading environment. Thefeedback channel’s capacity is limited so that each terminal can obtainonly quantized global CSI. Conventional interference management techniquestend to orthogonalize the transmissions of the sources. However,we permit them to transmit non-orthogonally and apply an interferencealignment scheme to tackle inter-user interference. Ideally, the interferencealignment concept coordinates the transmissions of the sources insuch a way that at each destination the interference signals from differentunintended sources are aligned together in the same sub-space which isdistinguishable from the sub-space for its desired signals. Hence, eachdestination can cancel the interference signals before performing decoding.Nevertheless, due to the imperfect channel knowledge, the interferencecannot be completely eliminated and thus causes difficulties to theinformation recovery process. We study efficient resource allocation intwo different classes of systems. In the first class, each source desires tosend information to its destination with a fixed data rate. The powercontrol problem tends to find the smallest transmission powers to guaranteesuccessful communications between all the source-destination pairs.In another class of systems where the transmission power of each sourceis fixed, a rate adaptation problem seeks the maximum sum throughputthat the network can support. In both cases, the combination of interferencealignment and efficient resource allocation provides substantialperformance enhancement over the conventional orthogonal transmissionscheme.When the fading environment is time-invariant, interference alignmentcan still be realized if each terminal is equipped with multiple antennas.With perfect global CSI at all terminals, the interference signalscan be aligned in the spatial dimension. If each terminal has only localCSI, which refers to the knowledge of channels directly related to  the terminal itself, an iterative algorithm can be applied to calculate thenecessary transmitter-side beamformers and receiver-side filters to properlyalign and cancel interference, respectively. Again, due to the lack ofperfect global CSI, it is difficult to completely eliminate the interferenceat each destination. We study the power control problem in this caseto calculate the minimum required power that guarantees each source tosuccessfully communicate with its destination with a fixed transmissionrate. In particular, since only local CSI is available at each terminal, wepropose an iterative algorithm that solves the joint power control andinterference alignment design in a distributed fashion. Our results showthat a substantial performance gain in terms of required transmissionpower over the orthogonalizing the transmissions of different sources canbe obtained. / <p>QC 20120912</p>