[Invited Paper] Superposed Multicarrier Transmission

Abstract

A superposed multicarrier transmission scheme is known to improve frequency utilization efficiency where several systems share spectrum without any spectrum spreading techniques. In the superposed multicarrier transmission scheme forward error correction (FEC) coding is in general applied so that the effects of interference caused by superposition of spectrum is mitigated by error correction capability. Thus, the superposed multicarrier transmission scheme is effective under cognitive environments where several wireless systems share the same frequency band. The superposed multicarrier transmission scheme is also expected in broadcasting where wireless communications are also used and can be interfered by other wireless systems. In the superposed multicarrier transmission scheme, to reduce the effects of interference by exploiting the capability of FEC, initial log likelihood ratio (LLR) should be set appropriately. Setting LLR correctly requires several information including interference power on each subcarrier, which are not known in general. We have developed several techniques to estimate the information including interference required for the superposed multicarrier transmission scheme. This paper introduces the superposed multicarrier transmission scheme. This paper also introduces some of our techniques proposed for the superposed multicarrier transmission scheme.