Cooperative transmission involves the simultaneous transmission by a group of devices, alldevices sending the same data. The devices may use sidelink (SL) to share data prior to thejoint transmission. Cooperative transmission helps improve network coverage since it can usethe combined transmission power of all devices in a group, whereas single-hop transmissionby one device is limited to its own maximum uplink power. Cooperative transmission aim is toimprove the network coverage of devices involved. The cooperative transmission solutioncomprisestwo steps. The first step is when a device (source device) in the group wants to senddata in the UL and then transmits data via SL to the devices in a created group. In the secondstep, all users simultaneously transmit the data in the UL to the base station the group isassigned to.This master thesis studies both the performance in the uplink (UL), comparing cooperativewith direct transmission, and how to reduce the power consumption of the devices involvedin the cooperative transmission.A power consumption model was developed to analyze the energy consumption, both viaanalytical and simulations methods. The analytical results show that cooperative transmissioncan reduce energy consumption by 7% compared to direct transmission. An algorithm wasproposed for cooperative transmission, which helps reduce energy consumption by 31%.Furthermore, the performance of cooperative transmissions was also studied using a systemsimulator. The results shows that the UL total bit rate increases with cooperative transmissionand is proportional to the number of users in the group. The total bit rate increased by 57%for a group with five users and for a group of 10 the increase was 107% (with a carrierfrequency of 3GHz). Different scenarios were simulated, and the increase in total bit ratevaries from 50-150%. Cooperative transmission involves the simultaneous transmission by a group of devices, alldevices sending the same data. The devices may use sidelink (SL) to share data prior to thejoint transmission. Cooperative transmission helps improve network coverage since it can usethe combined transmission power of all devices in a group, whereas single-hop transmissionby one device is limited to its own maximum uplink power. Cooperative transmission aim is toimprove the network coverage of devices involved. The cooperative transmission solutioncomprisestwo steps. The first step is when a device (source device) in the group wants to senddata in the UL and then transmits data via SL to the devices in a created group. In the secondstep, all users simultaneously transmit the data in the UL to the base station the group isassigned to.This master thesis studies both the performance in the uplink (UL), comparing cooperativewith direct transmission, and how to reduce the power consumption of the devices involvedin the cooperative transmission.A power consumption model was developed to analyze the energy consumption, both viaanalytical and simulations methods. The analytical results show that cooperative transmissioncan reduce energy consumption by 7% compared to direct transmission. An algorithm wasproposed for cooperative transmission, which helps reduce energy consumption by 31%.Furthermore, the performance of cooperative transmissions was also studied using a systemsimulator. The results shows that the UL total bit rate increases with cooperative transmissionand is proportional to the number of users in the group. The total bit rate increased by 57%for a group with five users and for a group of 10 the increase was 107% (with a carrierfrequency of 3GHz). Different scenarios were simulated, and the increase in total bit ratevaries from 50-150%.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

The rapid growth in demand for cellular mobile communications and emerging fixed wireless access has created the need to increase system capacity through more efficient utilization of the frequency spectrum, and the need for better grade of service. In cellular systems, capacity improvement can be achieved by reducing co-channel interference. Several techniques have been proposed in literature for mitigating co-channel interference, such as adaptive antennas and power control. Also, by allocating transmitter power and communication channels efficiently (resource allocation), overall co-channel interference can be maintained below a desired maximum tolerable level, while maximizing the carried traffic of the system. This dissertation presents investigation results on the performance of base station adaptive antennas, power control and channel allocation, as techniques for capacity improvement. Several approaches are analyzed. Firstly, we study the combined use of adaptive antennas and fractional loading factor, in order to estimate the potential capacity improvement achieved by adaptive antennas. Next, an extensive simulation analysis of a cellular network is carried out aiming to investigate the complex interrelationship between power control, channel allocation and adaptive antennas. In the first part of this simulation analysis, the combined use of adaptive antennas, power control and reduced cluster size is analyzed in a cellular system using fixed channel allocation. In the second part, we analyze the benefits of combining adaptive antennas, dynamic channel allocation and power control. Two representative channel allocation algorithms are considered and analyzed regarding how efficiently they transform reduced co-channel interference into higher carried traffic. Finally, the spatial filtering capability of adaptive antennas is used to allow several users to share the same channel within the same cell. Several allocation algorithms combined with power control are analyzed. / Ph. D.

Wireless ad-hoc networks are easily deployed, untethered to infrastructure, and have virtually an unlimited number of applications. However, this flexibility comes at the cost of finite and often unreplenishable power supplies. Once a node has consumed all of its power, it can no longer receive, transmit, gather information, or otherwise participate in the network. Therefore, reducing the amount of energy necessary for node communication has been an area of intense research. Previous work has investigated the use of directional antennas as a method to reduce inter-node power requirements. However, most proposed methods ignore inter-session interference, propose heuristic solution methods, and ignore the use of directional antennas for signal reception. We develop a flexible mixed-integer linear program (MILP) designed to optimize max-min multicast path lifetime for directional antenna equipped networks in the presence of interference. The MILP is utilized to perform a comparison directional antenna use for signal transmission and reception. Results indicate that directional reception is slightly superior to transmission for the defined max-min lifetime metric, and vastly superior when considering cumulative power use. We further analyze the performance of interference-ignorant link-based heuristics designed for both directional transmission and directional reception as they perform in our more realistic model. Our results show that interference-ignorant methods cannot find feasible solutions unless all nodes are equipped with high gain, high efficiency directional antennas. Even in these cases, directional reception outperforms directional transmission. Because of the superiority of directional reception, we focus our attention on this method. A heterogeneity study is performed, and two heuristic methods for approximating the MILP optima are developed. We find that even under heterogeneous conditions, directional reception can increase network lifetime. Finally, a genetic algorithm (GA) and semi-distributed heuristic method are developed as alternatives to the MILP. Results show that the GA often can find solutions with lifetimes 85% as long as the optimal. Our semi-distributed heuristic, designed to be even more computationally simple than the GA, and to serve as a basis for a distributed protocol, is almost as effective as the GA as approximating optimal solutions. We conclude that directional reception is the superior method of antenna use for extending max-min multicast tree lifetime, that it works well in heterogeneous conditions, and lends itself well to heuristic design. / Ph. D.

Dynamic spectrum access (DSA) is a powerful approach to mitigate the spectrum scarcity problem caused by rapid increase in wireless communication demands. Based on architecture design, DSA systems can be categorized as centralized and distributed. To successfully enable DSA, both centralized and distributed systems have to deal with spectrum management issues including spectrum sensing, spectrum decision, spectrum sharing and spectrum mobility. Our work starts by investigating the challenges of efficient spectrum monitoring in centralized spectrum sensing. Since central controllers usually require the presence information of incumbent users/primary users (IUs) for decision making, which is obtained during spectrum sensing, privacy issues of IUs become big concerns in some DSA systems where IUs have strong operation security needs. To aid in this, we design novel location privacy protection schemes for IUs. Considering the general drawbacks of centralized systems including high computational overhead for central controllers, single point failure and IU privacy issues, in many scenarios, a distributed DSA system is required. In this dissertation, we also cope with the spectrum sharing issues in distributed spectrum management, specifically the secondary user (SU) power control problem, by developing distributed and secure transmit power control algorithms for SUs. In centralized spectrum management, the common approach for spectrum monitoring is to build infrastructures (e.g. spectrum observatories), which cost much money and manpower yet have relatively low coverage. To aid in this, we propose a crowdsourcing based spectrum monitoring system to capture the accurate spectrum utilization at a large geographical area, which leverages the power of masses of portable mobile devices. The central controller can accurately predict future spectrum utilization and intelligently schedule the spectrum monitoring tasks among mobile SUs accordingly, so that the energy of mobile devices can be saved and more spectrum activities can be monitored. We also demonstrate our system's ability to capture not only the existing spectrum access patterns but also the unknown patterns where no historical spectrum information exists. The experiment shows that our spectrum monitoring system can obtain a high spectrum monitoring coverage with low energy consumption. Environmental Sensing Capability (ESC) systems are utilized in DSA in 3.5 GHz to sense the IU activities for protecting them from SUs' interference. However, IU location information is often highly sensitive in this band and hence it is preferable to hide its true location under the detection of ESCs. As a remedy, we design novel schemes to preserve both static and moving IU's location information by adjusting IU's radiation pattern and transmit power. We first formulate IU privacy protection problems for static IU. Due to the intractable nature of this problem, we propose a heuristic approach based on sampling. We also formulate the privacy protection problem for moving IUs, in which two cases are analyzed: (1) protect IU's moving traces; (2) protect its real-time current location information. Our analysis provides insightful advice for IU to preserve its location privacy against ESCs. Simulation results show that our approach provides great protection for IU's location privacy. Centralized DSA spectrum management systems has to bear several fundamental issues, such as the heavy computational overhead for central controllers, single point failure and privacy concerns of IU caused by large amounts of information exchange between users and controllers and often untrusted operators of the central controllers. In this dissertation, we propose an alternative distributed and privacy-preserving spectrum sharing design for DSA, which relies on distributed SU power control and security mechanisms to overcome the limitations of centralized DSA spectrum management. / Doctor of Philosophy / Due to the rapid growth in wireless communication demands, the frequency spectrum is becoming increasingly crowded. Traditional spectrum allocation policy gives the unshared access of fixed bands to the licensed users, and there is little unlicensed spectrum left now to allocate to newly emerged communication demands. However, studies on spectrum occupancy show that many licensed users who own the license of certain bands are only active for a small percentage of time, which results in plenty of underutilized spectrum. Hence, a new spectrum sharing paradigm, called dynamic spectrum access (DSA), is proposed to mitigate this problem. DSA enables the spectrum sharing between different classes of users, generally, the unlicensed users in the DSA system can access the licensed spectrum opportunistically without interfering with the licensed users. Based on architecture design, DSA systems can be categorized as centralized and distributed. In centralized systems, a central controller will make decisions on spectrum usage for all unlicensed users. Whereas in distributed systems, unlicensed users can make decisions for themselves independently. To successfully enable DSA, both centralized and distributed DSA systems need to deal with spectrum management issues, such as resource allocation problems and user privacy issues, etc. The resource allocation problems include, for example, the problems to discover and allocate idle bands and the problems to control users' transmit power for successful coexistence. Privacy issues may also arise during the spectrum management process since certain information exchange is inevitable for global decision making. However, due to the Federal Communications Commission's (FCC) regulation, licensed users' privacy such as their location information must be protected in any case. As a result, dynamic and efficient spectrum management techniques are necessary for DSA users. In this dissertation, we investigate the above-mentioned spectrum management issues in both types of DSA systems, specifically, the spectrum sensing challenges with licensed user location privacy issues in centralized DSA, and the spectrum sharing problems in distributed DSA systems. In doing so, we propose novel schemes for solving each related spectrum management problem and demonstrate their efficacy through the results from extensive evaluations and simulations. We believe that this dissertation provides insightful advice for DSA users to solve different spectrum management issues for enabling DSA implementation, and hence helps in a wider adoption of dynamic spectrum sharing.