Non-orthogonal Transmultiplexers for FBMC with Controlled ISI

摘要

Multicarrier modulation techniques, such as OFDM, are enabled by the use of transmultiplexers. In general, multicarrier modulation does not require perfect reconstruction of the transmitted carriers at the receiver, since near perfect reconstruction may provide similar performance with lower complexity or higher spectral efficiency. Near perfect reconstruction transmultiplexers which have low out of band ripples are seen extensively in literature. However, they exhibit a significant amount of inter-symbol interference (ISI), and closeness to orthogonality is imposed by an optimization criteria that determines the same. We propose a transmultiplexer that structurally has controlled ISI. The interference is strictly restricted to a predefined set of points that do not depend on the optimization performance, thereby reducing receiver complexity. A novel first order near-perfect reconstruction (NPR) block is proposed. This block is cascaded N times to generate an N-th order polyphase matrix which satisfies the NPR property, and this is then used to create controlled ISI transmultiplexers. We validate the fact that the out-of-band energy is limited even in the presence of ISI, using simulations.