Joint Optimization of Generalized Multicarrier Waveforms and Power Allocation for Two-Way Relay Systems

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Modern communication systems have evolved from pure voice call systems to networks supporting an increasing number of services with different Quality of Service (QoS) requirements. This development comes at the expense of a growing demand for high data rates having severe impacts on the architecture of mobile communication systems. Relaying is seen as a key technology to improve future wireless communication systems in terms of coverage extension and system throughput. However, as the deployment of relay nodes also introduces impairments due to the half-duplex constraint, sophisticated cooperative communication approaches are essential. In order to support the message exchange between two nodes, the concept of two-way relaying raised enormous interest recently as it facilitates the simultaneous transmission of both directions in the same frequency band. Based on this initial transmission, the relay broadcasts a joint message to both nodes in a second phase using the principle of network coding. The main gains are due to the application of physical layer network coding and the corresponding detection schemes in the first phase. Another key technology for future wireless communication systems is multicarrier transmission with non-orthogonal waveforms known as Generalized Frequency Division Multiplexing (GFDM) or equivalently Filterbank Based MultiCarrier (FBMC). These waveforms are well localized in time and frequency domain and allow for flexible usage of the resources in both dimensions. The design of the waveforms improves robustness against transceiver mismatches and, as adequate synchronization of several distributed nodes is a challenging task, the adaption of these innovative non-orthogonal waveforms for two-way relaying systems is a very promising approach.The main goal of this project is the development of a joint impulse shaping and resource allocation strategy for a two-way relay system including physical layer network coding and GFDM. Aiming for an overall high spectral efficiency while facilitating robustness against imperfections in the transceiver design, innovative waveforms and advanced coding & modulation concepts including PLNC are strongly required. The design of innovative waveforms allows for an efficient usage of the time-frequency grid and takes synchronization aspects such as time-and-frequency offsets into account. Moreover, the envisaged flexible but non-orthogonal waveform design allows controlling the trade-off between inter-carrier/-symbol interference and assignment of carriers to provide the required data rate. To cope for channel variations or changing rate requirements a flexible adaptation of waveforms (dynamic spectrum shaping), e.g., by using codebook-based approaches has to be investigated. The flexible adaptation of transmit parameters can especially be exploited in the multiple access phase of the two-way relaying protocol leading to highly scalable detectors at the relay.