The idea of utilizing multiple antennas (MIMO) has emerged as one of the significant breakthroughs in modern wireless communications. MIMO techniques can improve the spectral efficiency of wireless systems and provide significant throughput gains. As such, MIMO will be increasingly deployed in future wireless systems. On the other hand, in order to meet the increasing demand for high data rate multimedia wireless services, future wireless systems are evolving towards universal frequency reuse, where neighboring cells may utilize the same radio spectrum. As such, the performance of future wireless systems will be mainly limited by inter-cell interference (ICI). It has been shown that the throughput gains promised by conventional MIMO techniques degrade severely in multi-cell systems. This definitely attributes to the existence of the ICI. A lot of related work has been performed on the ICI mitigation or cancellation strategies, in multi-cell MIMO systems. Most of them assume that the channel and even data information is available at the collaborating base stations (BSs). Different from the previous work, we are looking into certain low-complexity codebook-based multi-cell multi-user MIMO strategies. For most of our work, we derive the statistics of the selected user's signal-to-interference-and-noise-ratio (SINR), which enable us to calculate the achieved sum-rate accurately and e ciently. With the derived sum-rate expressions, we evaluate and compare the sum-rate performance for several proposed low-complexity ICI-mitigation systems with various system parameters for single-user per-cell scheduling case. Furthermore, in order to fully exploit spatial multiplexing gain, we are considering multi-user per-cell scheduling case. Based on the assumption that all CSI including intra-cell and inter-cell channels are available at each BS, we rstly look into the centralized optimization approach. Typically, since the sum-rate maximization problem is mostly non-convex, it is generally di cult to obtain the globally optimum solution. Through certain approximation and relaxations, we successfully investigate an iterative optimization algorithm which exploits the second-order cone programming (SOCP) approach. From the simulation results, we will observe that the iterative option can provide near-optimum sum capacity, although only locally optimized. Afterwards, inspired by the successful application of Per-User Unitary Rate Control (PU2RC) scheme, we manage to extend it into dual-cell environment, with limited coordination between two cells. / Graduate

For opportunistic spectrum access and spectrum sharing in cognitive radio networks, one key problem is how to develop wireless access schemes for secondary users so that harmful interference to primary users can be avoided and quality-of-service (QoS) of secondary users can be guaranteed. In this research, dynamic wireless access protocols for secondary users are designed and optimized for both infrastructure-based and ad-hoc wireless networks. Under the infrastructure-based model, the secondary users are connected through a controller (i.e., an access point). In particular, the problem of wireless access for eHealth applications is considered. In a single service cell, an innovative wireless access scheme, called electromagnetic interference (EMI)-aware prioritized wireless access, is proposed to address the issues of EMI to the medical devices and QoS differentiation for different eHealth applications. Afterwards, the resource management problem for multiple service cells, specifically, in multiple spatial reuse time-division multiple access (STDMA) networks is addressed. The problem is formulated as a dual objective optimization problem that maximizes the spectrum utilization of secondary users and minimizes their power consumption subject to the EMI constraints for active and passive medical devices and minimum throughput guarantee for secondary users. Joint scheduling and power control algorithms based on greedy approaches are proposed to solve the problem with much less computational complexity. In an ad-hoc wireless network, the robust transmission scheduling and power control problem for collision-free spectrum sharing between secondary and primary users in STDMA wireless networks is investigated. Traditionally, the problem only considers the average link gains; therefore, QoS violation can occur due to improper power allocation with respect to instantaneous channel gain realization. To overcome this problem, a robust power control problem is formulated. A column generation based algorithm is proposed to solve the problem by considering only the potential subset of variables when solving the problem. To increase the scalability, a novel distributed two-stage algorithm based on the distributed column generation method is then proposed to obtain the near-optimal solution of the robust transmission schedules for vertical spectrum sharing in an ad-hoc wireless network.

For opportunistic spectrum access and spectrum sharing in cognitive radio networks, one key problem is how to develop wireless access schemes for secondary users so that harmful interference to primary users can be avoided and quality-of-service (QoS) of secondary users can be guaranteed. In this research, dynamic wireless access protocols for secondary users are designed and optimized for both infrastructure-based and ad-hoc wireless networks. Under the infrastructure-based model, the secondary users are connected through a controller (i.e., an access point). In particular, the problem of wireless access for eHealth applications is considered. In a single service cell, an innovative wireless access scheme, called electromagnetic interference (EMI)-aware prioritized wireless access, is proposed to address the issues of EMI to the medical devices and QoS differentiation for different eHealth applications. Afterwards, the resource management problem for multiple service cells, specifically, in multiple spatial reuse time-division multiple access (STDMA) networks is addressed. The problem is formulated as a dual objective optimization problem that maximizes the spectrum utilization of secondary users and minimizes their power consumption subject to the EMI constraints for active and passive medical devices and minimum throughput guarantee for secondary users. Joint scheduling and power control algorithms based on greedy approaches are proposed to solve the problem with much less computational complexity. In an ad-hoc wireless network, the robust transmission scheduling and power control problem for collision-free spectrum sharing between secondary and primary users in STDMA wireless networks is investigated. Traditionally, the problem only considers the average link gains; therefore, QoS violation can occur due to improper power allocation with respect to instantaneous channel gain realization. To overcome this problem, a robust power control problem is formulated. A column generation based algorithm is proposed to solve the problem by considering only the potential subset of variables when solving the problem. To increase the scalability, a novel distributed two-stage algorithm based on the distributed column generation method is then proposed to obtain the near-optimal solution of the robust transmission schedules for vertical spectrum sharing in an ad-hoc wireless network.

Attention-Deficit / Hyperactivity Disorder (ADHD) is characterized by higher than normal levels of inattention, hyperactivity and impulsivity. Behavioural inhibition is proposed to be a primary deficit in children with ADHD, and is included as a component of a number of models accounting for the core behavioural symptoms of ADHD. Children with ADHD often show deficits in their performance on behavioural inhibition tasks relative to typically developing children of the same age, although inconsistent findings have been observed. Stimulant medication is associated with reduction in the core symptoms of ADHD in the majority of children. The primary goal of this thesis was to examine the effects of stimulant medication on behavioural inhibition in children with ADHD. Furthermore, this thesis sought to determine whether children with ADHD who have, and have not taken stimulant medication differ from normally developing children in terms of behavioural inhibition. In order to achieve these aims, it was necessary to firstly determine which tasks provide the best measures of behavioural inhibition. While many tasks have been used to measure inhibitory control amongst children with ADHD, it was unclear from previous research which tasks measure the same constructs. Study 1 investigated relationships in task performance among seven measures of inhibitory control, including the Stop-Signal task, Go / No-go task, Sustained Attention to Response Task (SART; analogous the not-X Continuous Performance Task), Eriksen Flanker task, Stroop, Opposite Worlds task and Task-Switching task. Significant developmental changes in a variety of cognitive abilities occur across childhood and adolescence. To limit the possibility that developmental changes in task performance would be observed, the age range for children included in the study was restricted to seven to 10 years. Nevertheless, to interpret correlations among inhibition measures from the tasks, it was necessary to determine whether children showed comparable developmental trends in their performance across tasks. Study 1A investigated developmental changes in the performances of the seven tasks purported to measure inhibitory control in normally developing children aged seven to 10 years. The results of this study suggested that the tasks chosen were appropriate for use among this age group, and that there is little change in behavioural inhibition across the seven to 10 years age range. In Study 1B, inhibition measures from each of the tasks were included in an exploratory factor analysis to determine those tasks measuring the same constructs. The results of Study 1B suggested that the Stop-Signal, Go / No-go and SART tasks provided the best measures of the behavioural inhibition construct. Performance on the Eriksen Flanker task was also related to the performance on these tasks, but in a direction contrary to that predicted. The Stroop and Opposite Worlds tasks measured the same construct, which appeared to be interference control. Performance on the Task-Switching task was not related to the performance on any other task, suggesting that this task did not measure behavioural inhibition or interference control. Study 2 investigated the performance of children with ADHD on the three tasks shown to be the best measures of behavioural inhibition in Study 1B (i.e., the Stop-Signal task, Go / No-go task and Sustained Attention to Response task). Children with ADHD were aged from seven to 11 years, and were tested both when they had, and had not taken their regularly prescribed stimulant medication. The performance of children with ADHD on these tasks was compared to that of normally developing children matched in age. The results of Study 2 suggested that stimulant medication leads to significant improvement in behavioral inhibition amongst children with ADHD, such that children with ADHD do not differ from matched controls. However, this effect was not observed across all three tasks. Reasons for this, along with study limitations, and directions for future research are discussed.

Attention-Deficit / Hyperactivity Disorder (ADHD) is characterized by higher than normal levels of inattention, hyperactivity and impulsivity. Behavioural inhibition is proposed to be a primary deficit in children with ADHD, and is included as a component of a number of models accounting for the core behavioural symptoms of ADHD. Children with ADHD often show deficits in their performance on behavioural inhibition tasks relative to typically developing children of the same age, although inconsistent findings have been observed. Stimulant medication is associated with reduction in the core symptoms of ADHD in the majority of children. The primary goal of this thesis was to examine the effects of stimulant medication on behavioural inhibition in children with ADHD. Furthermore, this thesis sought to determine whether children with ADHD who have, and have not taken stimulant medication differ from normally developing children in terms of behavioural inhibition. In order to achieve these aims, it was necessary to firstly determine which tasks provide the best measures of behavioural inhibition. While many tasks have been used to measure inhibitory control amongst children with ADHD, it was unclear from previous research which tasks measure the same constructs. Study 1 investigated relationships in task performance among seven measures of inhibitory control, including the Stop-Signal task, Go / No-go task, Sustained Attention to Response Task (SART; analogous the not-X Continuous Performance Task), Eriksen Flanker task, Stroop, Opposite Worlds task and Task-Switching task. Significant developmental changes in a variety of cognitive abilities occur across childhood and adolescence. To limit the possibility that developmental changes in task performance would be observed, the age range for children included in the study was restricted to seven to 10 years. Nevertheless, to interpret correlations among inhibition measures from the tasks, it was necessary to determine whether children showed comparable developmental trends in their performance across tasks. Study 1A investigated developmental changes in the performances of the seven tasks purported to measure inhibitory control in normally developing children aged seven to 10 years. The results of this study suggested that the tasks chosen were appropriate for use among this age group, and that there is little change in behavioural inhibition across the seven to 10 years age range. In Study 1B, inhibition measures from each of the tasks were included in an exploratory factor analysis to determine those tasks measuring the same constructs. The results of Study 1B suggested that the Stop-Signal, Go / No-go and SART tasks provided the best measures of the behavioural inhibition construct. Performance on the Eriksen Flanker task was also related to the performance on these tasks, but in a direction contrary to that predicted. The Stroop and Opposite Worlds tasks measured the same construct, which appeared to be interference control. Performance on the Task-Switching task was not related to the performance on any other task, suggesting that this task did not measure behavioural inhibition or interference control. Study 2 investigated the performance of children with ADHD on the three tasks shown to be the best measures of behavioural inhibition in Study 1B (i.e., the Stop-Signal task, Go / No-go task and Sustained Attention to Response task). Children with ADHD were aged from seven to 11 years, and were tested both when they had, and had not taken their regularly prescribed stimulant medication. The performance of children with ADHD on these tasks was compared to that of normally developing children matched in age. The results of Study 2 suggested that stimulant medication leads to significant improvement in behavioral inhibition amongst children with ADHD, such that children with ADHD do not differ from matched controls. However, this effect was not observed across all three tasks. Reasons for this, along with study limitations, and directions for future research are discussed.

Dizertační práce se zabývá zpracováním signálu fyzických řídicích kanálů systému LTE a vyšetřováním bitové chybovosti při přenosu řídicí informace z vysílače do přijímače v závislosti na podmínkách příjmu. Práce je rozdělena do dvou hlavních částí. První část práce je zaměřena na simulaci přenosu řídicí informace LTE v základním pásmu. Jsou zde prezentovány vytvořené simulátory řídicích kanálů ve směru uplink i downlink. Simulace jsou provedeny pro všechny druhy nastavení systému a základní modely přenosového prostředí. Jsou zde popsány výsledky vlivu použití MIMO technologií na kvalitu příjmu řídicí informace především v únikových kanálech. Druhá část práce je zaměřena na možnost nasazení systému LTE ve sdíleném pásmu ISM (2.4 GHz). Jsou zde představeny základní koncepce použití, na jejichž základě je vytvořen scénář simulací. Kapitola dále popisuje tvorbu simulátoru koexistence LTE a systému Wi-Fi v přeneseném pásmu ISM 2.4GHz. Jsou zde uvedeny výsledky simulací koexistence LTE a rušivého systému Wi-Fi provedených dle vytvořeného scénáře. Výsledky simulací koexistence LTE a Wi-Fi jsou ověřeny měřením v laboratorních podmínkách. Toto porovnání je důležité z hlediska optimalizace simulátoru koexistence. Dle výsledků obou typů simulací a měření jsou stanovena provozní doporučení, která mají přispět k bezpečnému a spolehlivému vysílání a příjmu řídicích informací LTE i při nepříznivých podmínkách příjmu.

Alcohol use disorder (AUD) is a mental disorder that negatively affects personal health and burdens the global health system. Alcohol-attributed harms can also extend beyond the drinkers to other people in the society through increased road traffic accidents and more interpersonal violent behaviors. The effects of this disorder make it crucial to investigate predisposing mechanisms in order to identify at-risk individuals and further develop novel interventions. Although aberrant learning and dysfunctions in decision-making have been observed in individuals with AUD, it is not yet clear whether they predispose the development of risky drinking behaviors or result from repetitive alcohol use. To disentangle this, we studied the drinking behaviors of a community sample comprising participants who were 18–24, which is when the prevalence of alcohol use typically peaks. This thesis investigates whether two types of learning mechanisms—the balance between goal-directed and habitual control and the susceptibility to interference between Pavlovian cues and instrumental behaviors—are associated with the development of risky alcohol drinking behaviors. For Study 1, we assessed how goal-directed and habitual controls at 18 predispose alcohol use development over the course of 3 years. Goal-directed and habitual control, which are informed by model-based (MB) and model-free (MF) learning, were assessed with a two-step sequential decision-making task during functional magnetic resonance imaging. Three-year drinking trajectories were constructed based on the Alcohol Use Disorders Identification Test (AUDIT-C; assessed every 6 months) and a gram/drinking occasion measure (binge drinking score; assessed yearly). Latent growth curve models were applied to examine how the MB and MF controls were associated with the drinking trajectories. We found that MB control was negatively associated with the development of the binge drinking score trajectory. In contrast, MF reward prediction signals in the ventromedial prefrontal cortex and the ventral striatum (VS) were associated with a higher starting point and a steeper increase/less decrease in AUDIT-C, respectively. For Study 2, we investigated the cross-sectional association between the susceptibility to interference between Pavlovian cues and instrumental behaviors and risky (binge) drinking behaviors at age 18. During a Pavlovian-to-instrumental transfer (PIT) task, the participants were instructed to “collect good shells” and “leave bad shells” while the appetitive (monetary gain) or aversive (monetary loss) Pavlovian cues were presented in the background. The behavioral interference PIT effect was characterized by an increased error rate (ER) during incongruent trials (“collecting good shells” in the presence of an aversive Pavlovian cue or “leaving bad shells” during the presentation of an appetitive Pavlovian cue) in comparison to congruent ones. Overall, the individuals demonstrated a substantial behavioral PIT effect. Neural PIT correlates were found in the VS, dorsomedial, and lateral prefrontal cortices (dmPFC and lPFC, respectively). High-risk drinkers, in comparison to low-risk drinkers, exhibited a stronger behavioral PIT effect, decreased lPFC responses, and increased trend-level VS responses. Moreover, the effective connectivity from the VS to the lPFC during the incongruent trials was weaker for the high-risk drinkers, which indicates that the altered interplay between bottom-up and top-down neural responses may contribute to the poor interference control performance of this group. During Study 3, we further examined whether the susceptibility to Pavlovian cues during conflict trials was associated with the development of drinking behaviors over 6 years from ages 18 to 24. The drinking behaviors were again constructed based on the AUDIT-C and the binge drinking score. The PIT task was assessed at ages 18 and 21. Following Study 2, the increased ER in the incongruent condition compared with the congruent condition (along with the neural responses in the VS, lPFC, and dmPFC during the incongruent trials) were included in the latent growth curve models as predictors. A stronger VS response during a conflict at age 18 was associated with a higher starting point in both drinking trajectories but was negatively associated with the development of the binge drinking score trajectory. At age 21, high ER and enhanced neural responses in the dmPFC were associated with a risky AUDIT-C trajectory that started to emerge and develop until age 24. Through exploratory cluster analyses of the drinking trajectories, we identified two subgroups: the drinking behavior in the 'late riser' group escalated after age 21, whereas the drinking of 'early peakers' culminated at this age and then declined. The late risers displayed enhanced dmPFC responses and higher ER during conflict at age 21. Interestingly, this group also exhibited an increased ER from ages 18 to 21. Taken altogether, the unbalanced goal-directed to habitual control, informed by less MB and more MF control, appears to be a strong predisposing candidate mechanism that underlies the development of risky drinking behaviors during young adulthood. At age 18, the susceptibility to interference between Pavlovian cues and instrumental behaviors was associated with risky drinking behavior. The development of risky drinking behaviors over the 6 years was associated with the behavioral interference PIT effect at age 21 and its change from ages 18 to 21. Researchers could further explore the dynamics in PIT to predict risky drinking behaviors in the future.

No description available.

Le contrôle de l’interférence permet de sélectionner les actions pertinentes pour la réalisation d'un but dans un environnement saturé. La question de savoir si ce processus nécessite des ressources attentionnelles reste posée. Ce travail de thèse a été organisé en deux parties, la première basée sur une approche comportementale s'intéresse au contrôle de l'interférence en situation de restriction attentionnelle et la deuxième sur une approche neuropsychologique étudie ce même contrôle chez des individus présentant un TDAH. L'ensemble du travail expérimental regroupe 3 études et est centré essentiellement sur la réalisation d'une tâche de Simon. La première contribution expérimentale, composée de 4 expériences comportementales réalisées en double-tâche, a apporté des arguments en faveur de l'idée que les mécanismes responsables de l'inhibition sont sous la dépendance de ressources attentionnelles spécifiques. La contribution 2, concernant une étude realisée chez des adultes avec un TDA/H a révélé plusieurs aspects du contrôle de l'interférence. Premièrement, on peut observer un effet d’interférence aggravé sans un déficit d’impulsivité ou d’inhibition, deuxièmement, celui-ci pourrait être secondaire d'un ralentissement général dû à un défaut de vigilance, et troisièmement, ce déficit de vigilance n’affecterait pas la capacité d'inhibition. Finalement, la contribution expérimentale 3 ont non seulement permis de suggérer que les adultes avec un TDA/H ne présentaient pas de trouble de l’attention sélective, au moins dans le domaine temporel, mais ils ont permis de proposer que ces patients ont un déficit de la vigilance, confirmant ainsi l'hypothèse de la contribution 2. / Controlling interference allows the selection of appropriate from irrelevant actions in order to achieve a goal. However, the question as to whether this process requires attentional resources remains. To clarify this issue, this thesis has been organized into two parts. The first part is based on a behavioral approach and focuses on the control of interference in situations of attentional restriction. The second part focuses on a neuropsychological approach examining the same control in individuals AD/HD.The thesis encompasses three studies based on the conflict paradigm. Additionally, methodological tools and analysis and distribution of electromyographic activity were used to separate the two components of interference i.e. the automatic triggering of inappropriate response and its inhibition.The first experimental contribution, consisting of four dual-task behavioral experiments, supported the idea that the mechanisms of inhibition are dependent on specific attentional resources. The second contribution highlights several interesting aspects of interference control in ADHD: a decline in interference control without a deficit in impulsivity or inhibition; that the interference effect could be a secondary manifestation of a general slowdown due to a lack of vigilance; and that the deficit of vigilance does not affect the ability to inhibit (unlike selective attention, as evidenced in the first part of the study). The third contribution demonstrates that adults with ADHD show no disorder of selective attention at least in the time domain but also that these individuals manifested a deficiency in alertness, thus confirming the hypothesis of the preceding contributions.

Les petits appareils électroniques peu coûteux et à communication sans fil sont devenus largement disponibles. Bien que chaque entité ait des capacités limitées (par exemple, communication basique ou mémoire de taille constante), un déploiement à grande échelle de telles entités communiquantes constitue un réseau performant, en plus d’être peu coûteux. De tels systèmes distribués présentent toutefois des défis importants en ce qui concerne la conception d'algorithmes simples, efficaces et évolutifs. Dans cette thèse, nous nous intéressons à l’étude de ces systèmes, composés d’appareils dotés de capacités de communication très limitées, à base de simples impulsions d’énergie. Ces systèmes distribués peuvent être modélisés à l'aide du modèle de bips, dans lequel les nœuds communiquent en émettant un bip, un simple signal indifférencié, ou en écoutant leurs voisins (selon un graphe de communication non orienté). Les communications simultanées (c'est-à-dire les collisions) entraînent des interférences non destructives : un nœud, dont deux voisins ou plus émettent simultanément un bip, détecte seulement un bip. Ce mécanisme de communication simple, général et économe en énergie rend les résultats obtenus dans le modèle de bips applicables à de nombreuses situations différentes, avec cependant un challenge. En raison de la faible expressivité des bips et des collisions, la conception des algorithmes est difficile. Tout au long de ce travail, nous surmontons ces deux difficultés afin de fournir des primitives de communication efficaces. La thèse s’intéresse particulièrement aux solutions déterministes, rapides (en temps) et indépendantes des paramètres du graphe de communication (c’est-à-dire uniformes). La première partie de la thèse considère un cadre dans lequel les nœuds se réveillent en même temps (c’est-à-dire que le réseau a été configuré a priori). Pour obtenir des solutions efficaces pour des problèmes fondamentaux de communication distribuée, nous nous concentrons d’abord sur la résolution efficace de problèmes de brisure locale de symétrie : ensemble indépendant maximal et coloration de sommets utilisant au plus Δ + 1 couleurs (où Δ est le degré maximal du graphe de communication). Nous élaborons des solutions à ces problèmes ainsi qu'à leurs variantes à distance deux. Cela nous permet de simuler une communication par messages. Enfin, nous obtenons le premier algorithme de coloration utilisant moins de Δ + 1 couleurs dans le modèle de bips. Ensuite, nous étudions des problèmes définis à l’échelle du réseau, tels que l’élection d'un leader et la diffusion multiple de messages. L'élection d'un leader est un élément essentiel dans la conception d'algorithmes distribués. Nous donnons les deux premiers algorithmes d’élection de leader optimaux en temps pour le modèle de bips. L'un est déterministe, mais nécessite des identifiants uniques. Le second n’a pas besoin d’identifiants (utile pour des raisons de sécurité et de confidentialité), mais est randomisé. S'appuyant sur une élection de leader optimale en temps, plusieurs algorithmes pour la diffusion multiple, efficaces en temps et en calcul, sont présentés. La deuxième partie de la thèse considère un cadre plus difficile mais plus général, dans lequel les nœuds se réveillent de façon asynchrone. Nous nous concentrons sur le problème de désynchronisation à distance deux, qui permet un contrôle de l'accès au support, primordial dans les réseaux sans fil. Nous montrons qu'il est possible pour les nœuds de communiquer de manière cohérente au-delà de leur voisinage immédiat. A cette fin, une primitive permettant aux nœuds de simuler une communication est présentée. Cette primitive est un élément central dans la conception de l'algorithme de désynchronisation à distance deux. Enfin, nous exploitons cette solution afin d'implémenter des primitives de haut niveau pour l’envoi et la réception de messages. / Small inexpensive inter-communicating electronic devices have become widely available. Although the individual device has severely limited capabilities (e.g., basic communication, constant-size memory or limited mobility), multitudes of such weak devices communicating together are able to form a low-cost, easily deployable, yet highly performant network. Such distributed systems present significant challenges however when it comes to the design of efficient, scalable and simple algorithms. In this thesis, we are interested in studying such systems composed of devices with severely limited communication capabilities - using only simple bursts of energy. These distributed systems may be modeled using the beeping model, in which nodes communicate by beeping or listening to their neighbors (according to some undirected communication graph). Simultaneous communications (i.e., collisions) result in non-destructive interference: a node with two or more neighbors beeping simultaneously detects a beep. Its simple, general and energy efficient communication mechanism makes the beeping model widely applicable. However, that simplicity comes at a cost. Due to the poor expressiveness of beeps and the interference caused by simultaneous communications, algorithm design is challenging. Throughout this work, we overcome both difficulties in order to provide efficient communication primitives. A particular focus of the thesis is on deterministic and time-efficient solutions independent of the communication graph's parameters (i.e., uniform). The first part of the thesis considers a setting in which nodes wake up at the same time (i.e., the network has been set up a priori). To obtain efficient solutions to fundamental distributed communication problems, we first focus on efficiently solving problems for local symmetry-breaking: (Δ+1)-vertex coloring and maximal independent set (where Δ is the maximum degree of the communication graph). The solutions we devise are particularly efficient when the communication graph is sparse. They are then used to solve the 2-hop variants of these problems and to simulate message-passing. Finally, combining this simulation with existing results, which assume message-passing, gives the first vertex coloring algorithm using less than Δ+1 colors in the beeping model. Then, we study problems defined on a global scale, such as leader election and multi-broadcast (i.e., information dissemination). Leader election is a crucial building block in the design of distributed algorithms. We give the first two time-optimal leader election algorithms for the beeping model. One is deterministic, but requires unique identifiers. The second one does not need identifiers (useful for security and privacy reasons), but is randomized. Building upon the time-optimal leader election solution, computationally efficient and time-optimal algorithms for multi-broadcast are presented. Although a previous time-optimal solution was available, it required computationally expensive methods. The second part of the thesis considers a more difficult but more general setting, in which nodes wake up at some arbitrary time rounds. We focus on the desynchronization problem, and more precisely on its 2-hop variant, which can be used as medium access control method. We show that it is possible for nodes to communicate in a coherent manner beyond their 1-hop neighborhood. More concretely, a primitive allowing nodes to simulate communication on the square of the communication graph is presented. This primitive is a centerpiece in the design of the 2-hop desynchronization algorithm. Finally, by leveraging this solution, we show that higher-level primitives for sending and receiving messages can be obtained in this difficult setting.