A virtual input-output framework for transceiver analysis and design for multipath fading channels

An understanding of the interaction between the channel and the signal space is key to reliable communication. Multipath fading channels exhibit inherent diversity that can be exploited via appropriate signaling and reception. We develop a virtual multiple-input multiple-output framework for characterizing single-transmitter single-receiver multipath fading channels, where the virtual multiple inputs and outputs are created by the dimensions of the signaling scheme. The essence of the framework is a representation of the system with respect to appropriately chosen basis waveforms for the signal space that expose the inherent structure of the channel. The structure makes it possible to derive closed-form expressions for ergodic and outage capacity for a variety of transceivers and to design novel transceivers. In many cases, the analysis clearly reveals the key factors that affect system performance. We provide new capacity expressions for a variety of transceivers. In particular, by analyzing particular transceivers, we provide new expressions that bound the outage capacity performance of the multipath channel. A novelty of this work lies in being able to apply codes developed for orthogonal frequency-division multiplexing systems and multiple antenna systems to existing code-division multiple-access-based systems.