1 Department of Photonics Engineering, Technical University of Denmark2 Networks Technology and Service Platforms, Department of Photonics Engineering, Technical University of Denmark3 Networks, Department of Photonics Engineering, Technical University of Denmark4 Department of Telecommunication, Technical University of Denmark
Although wireless networks have achieved great success in the lastest two decades, the current wireless networks have difficulties to fulll users' ever-increasing expectations and needs. It is mainly due to available spectrum resource scarcity, limited battery capacity of wireless device, unreliable wireless radio link, etc. To tackle these issues, a new telecommunication paradigm has been proposed, referred to as cooperative wireless networking . The basic idea of cooperative wireless networking is that wireless devices work together to achieve their individual goals or one common goal following a common strategy. Wireless devices share their resources (i.e. radio link, antenna, battery, processing unit, etc.) during cooperation using the short-range technology as the underlying communication platform. The amount of data exchanged over the short-range link diers from application to application. In some situations the short-range communication is not used at all in case all mobile devices have a predefined mutual understanding of their cooperativeness. The main reason of cooperation is threefold: first, the limit capability of wireless devices can be virtually enhanced by cooperation; secondly, the increasing density of the wireless devices makes cooperation possible; last, the cost of information exchange (i.e. transmission power, transmission time, spectrum, etc.) is very low if information exchange over short-range link is needed. Cooperation changes the way of information delivery and the concept of wireless device resource. It is promising to solve the crucial issues that cannot be easily tackled in conventional network architectures. Different cooperative strategies or schemes according to cooperation concept are proposed in the thesis to solve crucial issues in different wireless networks. An energy saving cooperative strategy for DVB-H in ii Abstract networks is designed as a primary attempt to illustrate the potential of cooperation application for multicast services. Furthermore, a cooperative retrans-mission scheme is proposed for reliable multicast service in wireless network. These two cooperative schemes are used for downlink traffic. In addition to that, cooperation is also applied to uplink access. One4all cooperative uplink access strategy is proposed for WLAN to reduce the collision probability to save energy. Cooperation concept is also applied in spectrum sensing for a cognitive radio MAC protocol. Finally, a novel modulation, hierarchical modulation, is used to facilitate the uplink transmission in cooperative networks. Simulation and analytical analysis has been conducted. Great potentials of cooperation are shown in improving the energy effciency, spectrum effciency, quality of service, and so on.