· · · Institutional Repository

Personal network and their federations (called Fednet) are considered as one of the promising future concepts regarding the personal communication. In this thesis, we first studies the state of the art of Fednet, from which we know there are two approaches for providing the services in Fednet, one is overlay and the other is proxy-based. Each of the approaches has the advantages and drawbacks. To trade off between these two approaches, we propose a new scheme, which can make the way of service provisioning in Fednet flexible and adaptable to the changing environment and the user’s preference.

The Third Generation Partnership Program's Long-Term Evolution Advanced (3GPP LTE-Advanced) group is developing a new standard for mobile broadband access that will meet the throughput and coverage requirements of a fourth generation cellular technology. The key goals for this evolution are increased data rate, improved spectrum efficiency, improved coverage and reduced latency. The ultimate results of these goals are significantly improving service provisioning and reduction of operator costs for different traffic scenarios. One of the main challenges faced by the developing standard is providing high throughput at the cell edge. Cell edge performance is becoming more important as cellular systems employ higher bandwidths with the same amount of transmit power and use higher carrier frequencies with infrastructure designed for lower carrier frequencies. One solution to improve coverage is to use the fixed relays to transmit data between the Base Stations and the Mobile Stations or User Equipments through multi hop communication. For this reason, relay technologies have been actively studied and considered in the standardization process of next-generation mobile broadband communication system. As a next-generation 3GPP standard, LTE-Advanced exclusively takes the relay technology into account. This thesis focuses the relay technologies for the LTE-Advanced systems and evaluates the performance of the relay-enhanced LTE-Advanced network. The approach for this work is to design several environments for LTE-Advanced networks involving relays. Incorporating the channel model from the Wireless World Initiative New Radio (WINNER) project, four environments were designed among which one environment considers no relay at all and the rest of the environments considered relay deployments. And the performances of all the environments are evaluated in terms of Symbol Error Rate (SER) versus the Signal to Noise Ratio (SNR), under several different scenarios defined in WINNER project. As an outcome, the simulation results from the simulator show that relay technologies can effectively improve service performance.

Homes, offices and vehicles are getting networked. This will enable context aware, autonomous operation of many support systems that could be controlled remotely. To achieve this there would be a large number of tiny devices -- sensors and actuators -- which are networked and they are termed generally as Internet of Things (IoT) devices. In future, they will be powered through harvested energy from the ambience to enable perennial lifetime and minimal manual maintenance. Some examples of energy sources are photovoltaic panels and piezoelectric crystals. Several challenges arise due to the nature of sources of energy. One of these challenges is that the devices (nodes) leave and re-enter networks due to fluctuating availability of harvested energy. This energy condition requires the adaptation of special means at every layer of the communication model. For example, as a result of fluctuating energy levels, the neighbor table maintained at each node changes quite often leading to complications in forming and maintaining routes. In fact initial neighbor discovery (ND) itself is a difficult task. Further, usage of directional antennas would affect the time taken to complete ND. Given the spatio-temporal variations in energy availability in harvesting environments, there are benefits of energy prediction. With the help of prediction, resource allocation within a single system and splitting of tasks between nodes in a network would be enhanced. In order to identify the various parameters that affect ND we first describe a generic analytical model of an energy harvesting device. Next, we study a network of these devices through exhaustive simulation study considering these various parameters. We demonstrate the benefits and challenges of using directional antennas for ND. We present a scheme that nodes could use to discover their neighbors during initial deployment and another scheme that could be used for subsequent discovery on re-entry into the network. We show that a dedicated ND protocol is necessary for energy harvesting networks and that directional ND is beneficial in these networks under some circumstances. Finally, we present light-weight energy prediction solutions that can be used to improve the performance of the ND process in particular.

The thesis aims at extending the capabilities of devices and enabling cooperation, i.e., data connection sharing, among users who may or may not necessarily be related to or know each other. To achieve this objective as well as to validate the results of our theoretical analysis, we developed a smart-phone application for data connection sharing. By means of data connection sharing, users may influence the pricing schemes of mobile network operators, increase spectrum utilization and build their own cooperative network. We define the mobile tethering game and investigate what makes the cooperation work and what are the economic requirements for building a cooperative network. The mobile tethering game may pave the way for a new business model where users not only get Internet connection service but also sell it in a mobile fashion. Using the results of the conjoint analysis integrated with the game theoretic model and the smart-phone application, the thesis will present a clear picture as to the interactions among players of the mobile tethering game and the influential preference factors. We are interested in figuring out whether people might be willing to share their connection for incentives (money or virtual currency) or whether they are just expecting to receive the same treatment (service) in a future interaction.

The limited availability of radio frequency spectrum demands for more efficient ways to utilize it in future wireless networks. Spectrum sharing radios are an interesting solution to the spectral scarcity problem, where the available resources are adaptively used across time and frequency without affecting other user's transmissions. In this context, sensing the spectrum for its occupancy is needed to increase the awareness among technologies that share the same spectrum. In a typical wireless sensor network, each node senses and transmits data constrained by a very low power budget. At the same time, they should be capable of finding a free frequency channel with minimal latency. A solution to this problem is to make radios capable of sensing multiple frequency bands, in the order of a few hundred MHz, all at once. The technical challenge lies in the design of low-complexity wideband spectrum sensing techniques that increase context awareness at the wireless node. In this thesis, we address this problem with two approaches. The first approach is based on Compressed Sampling (CS) theory, where a new perspective is taken, different to conventional methods that estimate the spectrum and perform detection on the reconstructed spectrum. Instead a direct detection is performed on the sub-Nyquist rate sampled wideband signal. In the second part of this thesis, an alternative approach to reduce the power at an architectural level is proposed, by avoiding the Nyquist rate wideband Analog-to-Digital Converter (ADC) and pushing the conventional digital processing to the analog domain.