This dissertation focuses on downlink multi-antenna transmission with packet scheduling in a wireless packet data network. The topic is viewed as a critical system design problem for future high-speed packet networks requiring extremely high spectral efficiency. Our aim is to illustrate the interaction between transmission schemes at the physical layer and scheduling algorithms at the medium access control (MAC) layer from a sum-capacity perspective. Various roles of multiple antennas are studied under channel-aware scheduling, including diversity, beamforming and spatial multiplexing. At a system performance level, our work shows that downlink throughput can be optimized by joint precoding across multiple transmit antennas and exploiting small-scale fading of distributed multiple input and multiple output (MIMO) channels. There are three major results in this dissertation. First, it is shown that over a MIMO Gaussian broadcast channel, and under channel-aware scheduling, open-loop transmit antenna diversity actually reduces the achievable sum rate. This reveals a negative interaction between open-loop antenna diversity and the closed-loop multiuser diversity through scheduling. Second, a suboptimal dirty paper coding (DPC) approach benefits greatly from multiuser diversity by an efficient packet scheduling algorithm. Performance analysis of a suboptimal greedy scheduling algorithm indicates that, compared with the receiver-centric V-BLAST method, it can achieve a much larger scheduling gain over a distributed MIMO channel. Further, pre-interference cancellation allows for transmissions free of error propagation. A practical solution, termed Tomlinson-Harashima precoding (THP), is studied under this suboptimal scheduling algorithm. Similar to V-BLAST, a reordering is applied to minimize the average error rate, which introduces only a negligible sum-rate loss in the scenarios investigated. Third, for an orthogonal frequency division multiplexing (OFDM) system using MIMO precoding, it is shown that a DPC-based approach is readily applicable and can be easily generalized to reduce the peak-to-average power ratio (PAR) up to 5 dB without affecting the receiver design. Simulations show that in an interference-limited multi-cell scenario, greater performance improvement can be achieved by interference avoidance through adaptive packet scheduling, rather than by interference diversity or averaging alone. These findings suggest that, coordinated with channel-aware scheduling, adaptive multiplexing in both spatial and frequency domains provides an attractive downlink solution from a total capacity point of view. / Ph. D.

The proliferation of connected embedded devices has driven wireless communications into commercial, military, industrial, and personal systems. It is unreasonable to expect privacy and security to be inherent in these networks given the spatial density of these devices, limited spectral resources, and the broadcast nature of wireless communications systems. Communications for these systems must have sufficient information capacity and secrecy capacity while typically maintaining small size, light weight, and minimized power consumption. With increasing crowding of the electromagnetic spectrum, interference must be leveraged as an available resource. This work develops a new beamforming method for direction-dependent modulation that provides wireless communications devices with enhanced physical layer security and the ability to simultaneously communicate and harvest energy by exploiting co-channel interference. We propose a method that optimizes a set of time-varying array steering vectors to enable direction-dependent modulation, thus exploiting a new degree of freedom in the space-time-frequency paradigm. We formulate steering vector selection as a convex optimization problem for rapid computation given arbitrarily positioned array antenna elements. We show that this method allows us to spectrally separate co-channel interference from an information-bearing signal in the analog domain, enabling the energy from the interference to be diverted for harvesting during the digitization and decoding of the information-bearing signal. We also show that this method provides wireless communications devices with not only enhanced information capacity, but also enhanced secrecy capacity in a broadcast channel. By using the proposed method, we can increase the overall channel capacity in a broadcast system beyond the current state-of-the-art for wireless broadcast channels, which is based on static coding techniques. Further, we also increase the overall secrecy capacity of the system by enabling secrecy for each user in the system. In practical terms, this results in higher-rate, confidential messages delivered to multiple devices in a broadcast channel for a given power constraint. Finally, we corroborate these claims with simulation and experimental results for the proposed method. / PHD / The proliferation of connected devices has driven wireless communications into commercial, military, industrial, and personal systems. It is unreasonable to expect privacy and security to be inherent in these networks given the spatial density of these devices, limited available resources, and the broadcast nature of wireless communications systems. Communications for these systems need not only sufficient information capacity, but also the assurance that the available information capacity remains confidential while typically maintaining small size, light weight, and minimized power consumption. With increasing crowding of the electromagnetic spectrum due to the numerous connected devices, interference between them must be leveraged as an available resource. This work develops a new method for electrically steering an array of antennas to overlay or encode information onto a signal in a way that is direction-dependent and provides wireless communications devices with enhanced security and the ability to simultaneously communicate and harvest energy from interfering devices. We propose a method that optimizes a set of time-varying array steering vectors to enable direction-dependent modulation, thus exploiting a new degree of freedom in the traditional space-time-frequency paradigm. We formulate the selection of steering vectors as a convex optimization problem for rapid computation given arbitrarily positioned array antenna elements in three dimensions. We show that this method allows us to separate interference from an information-bearing signal in the analog domain, enabling the energy from the interference to be diverted for harvesting during the digitization and decoding of the information-bearing signal. We also show that this method provides broadcast wireless communications devices with not only increased information capacity, but also assured secrecy. By using the proposed time-varying method, we can increase the overall channel capacity in a broadcast system beyond the current state-of-the-art, which is based on static encoding techniques. Further, we also increase the overall secrecy capacity of the system by ensuring that each user in the system receives separate and confidential signals. In practical terms, this results in higher-rate, confidential messages delivered to multiple devices in a broadcast channel for a given power constraint. Finally, we corroborate these claims with simulation and experimental results for the proposed method.

Thesis (M.S.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / OBJECTIVES: "Americans in Exile," a two-part documentary series for radio is an endeavor to shed some light on a subject which has been shrouded in confusion and, in many cases, simplistic thinking: draft dodgers and deserters in Canada. [TRUNCATED] / 2999-01-01

Previous research into sporting events and broadcast commentary have been consistent in showing that there are clear differences in prevalence of commentary topics when a commentator is describing a male athlete and a female athlete. Among these differences are sexualized and ambivalent language towards female athletes, gender marking, and language that suggests male athlete superiority to that of female athletes. Although sporting events such as the Summer and Winter Olympics and NCAA Men's and Women's Basketball Championship games have repeatedly been sites for exploration, the world's largest single-event sporting competition, the World Cup, remains relatively untouched. Keeping this in mind, using a systematic content analysis, this thesis analyzed the broadcast commentary provided by play-by-play and color commentators in FIFA World Cup and FIFA Women's World Cup final matches to discern whether or not the sex of the athlete competing resulted in a difference in the descriptive evaluations employed by commentators. Findings of this study revealed that there were few differences in the prevalence of descriptive evaluations based on the gender of the athletes competing. Implications of the results and recommendations for future research into broadcast commentary and World Cup final matches are addressed. / Master of Arts / Previous research into the role of broadcast commentary in sporting events has shown that not only are there differences in what sports commentators say about male and female athletes, but also in how often specific types of commentary occur. Through the examination of pinnacle athletic competitions, findings have revealed a higher frequency of sexualized and contradictory language towards female athletes, an increase in gender marking, and language that suggests the superiority of male athletes to that of female athletes, among other things. Despite the wide range of athletic competitions that have garnered research attention, one event that has remained relatively ignored is the FIFA World Cup. Because of this, by examining the broadcast commentary provided during FIFA World Cup and FIFA Women’s World Cup final matches, this study looked to discover if the sex of the athlete competing impacted how often certain evaluation types occurred during game action. Findings showed that there were few differences in the prevalence of these evaluations based on the sex of the athlete competing. In addition to discussing the findings of this study, recommendations for future research are also addressed.

Tornado warnings are life-threatening situations, and since the public uses television as the main source for tornado warning information, it is important to know how different visuals and messages are influencing the opinions and intentions of people. This research found that participants were more apt to say they would shelter if they were shown a tornado video than a radar video displaying storm-relative velocity or correlation coefficient, while seeing the tornado brought out a heightened level of anxiety and fear. Participants were most influenced by a call-to-action statement spoken by the meteorologist. Participants expressed negative feelings after being asked to both shelter and send in tornado footage at the same time. The standard call-to-action video and one with the addition of viewer-submitted tornado footage were statistically equivalent. Participants more correctly identified the location of a tornado on the radar product explained to them than one that was not.

An important problem for economists and policy-makers concerning the cable industry is whether the cable industry faces widespread direct competition. Only one roughly comparable, nation-wide competitor exists, Direct Broadcast Satellite ("DBS"), and there are some indications that DBS does not constrain cable prices. The model presented in this paper indicates that DBS and cable compete imperfectly in terms of monthly prices, if at all, but compete more directly in terms of the premium-level services they offer. Other factors may indicate whether a community is open to advanced services like DBS, such as whether the cable operators offers high-speed Internet access. / Master of Arts

This study of radio news stations adds to the field of Twitter research into broadcasters' use of this social media microblogging platform; previous research has predominantly focused on television. This case study, based on a survey with numerous open-ended questions completed in face-to-face interviews, begins to fill in data on how Twitter is being used in major market radio station newsrooms. Limited in scope, this exploratory study used answers from seven members of two radio newsrooms in trying to find out if there were stated goals for tweets; if separate, unique content was being tweeted or was content tied to the stations' on-air product; how tweets seek to increase station listenership and/or increase station website traffic; what were the most frequently tweeted topics; what hyperlinks were included in tweets for internal or external web content; and were tweets personal and/or opinionated, or kept more professional with just factual material. From a strategic management theory standpoint, there is neither a stated plan nor goals sought with these newsrooms' use of Twitter. Unique tweet content includes sending out photos which add visuals to the pictureless world of radio news and live-tweeting of ongoing news events, while complementary content is promotional to push audience members to on-air or website products. There are no analytics in place to try to determine whether the stations' listenership or web traffic increases based on tweets. Promotional teases of upcoming on-air guest interviews or news content and/or web content are the most frequently tweeted topics. Hashtags rather than hyperlinks are more often included in the stations' tweets. News personnel stay away from expressing opinions, or being too personal in tweets, but remain more objective and professional by sticking to facts which is in step with the traditional role of journalists.

The lack of interoperability between Pay‐TV service providers and a horizontally integrated business transaction model have compromised the competition in the Pay‐TV market. In addition, the lack of interactivity with customers has resulted in high churn rate and improper security measures have contributed into considerable business loss. These issues are the main cause of high operational costs and subscription fees in the Pay‐TV systems. This paper presents a novel end‐to‐end system architecture for Pay‐TV systems cooperating mobile and broadcasting technologies. It provides a cost‐effective, scalable, dynamic and secure access control mechanism supporting converged services and new business opportunities in Pay‐TV systems. It enhances interactivity, security and potentially reduces customer attrition and operational cost. In this platform, service providers can effectively interact with their customers, personalise their services and adopt appropriate security measures. It breaks up the rigid relationship between a viewer and set‐top box as imposed by traditional conditional access systems, thus, a viewer can fully enjoy his entitlements via an arbitrary set‐top box. Having thoroughly considered state‐of‐the‐art technologies currently being used across the world, the thesis highlights novel use cases and presents the full design and implementation aspects of the system. The design section is enriched by providing possible security structures supported thereby. A business collaboration structure is proposed, followed by a reference model for implementing the system. Finally, the security architectures are analysed to propose the best architecture on the basis of security, complexity and set‐top box production cost criteria.

Advancements in video coding, compact media display, and communication devices, particularly in emerging broadband wireless access networks, have created many foreseeable and exciting applications of video broadcast/multicast over the wireless meidum. For efficient and robust wireless video broadcast/multicast under fading, this thesis presents and examines a novel cross-layer framework that exploits the interplay between applying protections on a successively refinable video source and transmitting through a layered broadcast/multicast channel. The framework is realistically achieved and evaluated by using multiple description coding (MDC) on a scalable video source and using superposition coding (SPC) for layered broadcast/multicast transmissions. An analytical model using the total received/recovered video bitstreams from each coded wireless broadcast/multicast signal is developed, which serves as a metric of video quality for the system analysis and optimization. An efficient methodology has demonstrated that optimal power allocations and modulation selections can be practically determined to improve the broadcast/multicast video quality. From the information-theoretical perspective, a general closed-form formula is derived for the end-to-end distortion analysis of the proposed framework, which is applicable to any (n, k) protection code applied on a successive refinable source with a Gaussian distribution over layered Gaussian broadcast channels. The results reveal the scenarios for the proposed framework to lead to a lower distortion than a legacy system without any protection. By analyzing the characteristics of the closed-form formula, an efficient O(n log n) algorithm is developed to determine optimal k values in the (n, k) protection codes that minimize the distortion under the framework. Finally, a cross-layer design of logical SPC modulation is introduced to achieve layered broadcast/multicast for scalable video. It serves as an alternative for practically implementing the proposed framework of coded wireless video broadcast/multicast, if the hardware-based SPC component is not available in a wireless system. In summary, the thesis presents comprehensive analyses, simulations, and experiments to understand, investigate, and justify the effectiveness of the proposed cross-layer framework of coded wireless video broadcast/multicast. More importantly, this thesis contributes to the advancement in the related fields of communication engineering and information theory by introducing a new design dimension in terms of protection. This is unique when compared to previously-reported layered approaches that are often manipulating conventional parameters alone such as power and modulation scheme. The impact of this dimension was unapparent in the past, but is now proven as an effective means to enable high-quality, efficient, and robust wireless video broadcast/multicast for promising media applications.

Advancements in video coding, compact media display, and communication devices, particularly in emerging broadband wireless access networks, have created many foreseeable and exciting applications of video broadcast/multicast over the wireless meidum. For efficient and robust wireless video broadcast/multicast under fading, this thesis presents and examines a novel cross-layer framework that exploits the interplay between applying protections on a successively refinable video source and transmitting through a layered broadcast/multicast channel. The framework is realistically achieved and evaluated by using multiple description coding (MDC) on a scalable video source and using superposition coding (SPC) for layered broadcast/multicast transmissions. An analytical model using the total received/recovered video bitstreams from each coded wireless broadcast/multicast signal is developed, which serves as a metric of video quality for the system analysis and optimization. An efficient methodology has demonstrated that optimal power allocations and modulation selections can be practically determined to improve the broadcast/multicast video quality. From the information-theoretical perspective, a general closed-form formula is derived for the end-to-end distortion analysis of the proposed framework, which is applicable to any (n, k) protection code applied on a successive refinable source with a Gaussian distribution over layered Gaussian broadcast channels. The results reveal the scenarios for the proposed framework to lead to a lower distortion than a legacy system without any protection. By analyzing the characteristics of the closed-form formula, an efficient O(n log n) algorithm is developed to determine optimal k values in the (n, k) protection codes that minimize the distortion under the framework. Finally, a cross-layer design of logical SPC modulation is introduced to achieve layered broadcast/multicast for scalable video. It serves as an alternative for practically implementing the proposed framework of coded wireless video broadcast/multicast, if the hardware-based SPC component is not available in a wireless system. In summary, the thesis presents comprehensive analyses, simulations, and experiments to understand, investigate, and justify the effectiveness of the proposed cross-layer framework of coded wireless video broadcast/multicast. More importantly, this thesis contributes to the advancement in the related fields of communication engineering and information theory by introducing a new design dimension in terms of protection. This is unique when compared to previously-reported layered approaches that are often manipulating conventional parameters alone such as power and modulation scheme. The impact of this dimension was unapparent in the past, but is now proven as an effective means to enable high-quality, efficient, and robust wireless video broadcast/multicast for promising media applications.