Transmission Schemes for Multicarrier Broadcast and Unicast Hybrid Systems

Wireless infrastructures can be conveniently categorized into two types: those that provide point-to-point dasiaunicastpsila connectivity (e.g., cellular) and others that are dasiabroadcastpsila in nature (such as TV and radio) and are inherently point-to-multipoint. This paper introduces a transmission scheme for multicarrier hybrid system that supports both broadcasting and unicasting on a single-frequency platform. In particular, we present a dirty-paper coding (DPC) based overlay architecture to enable interference-free reception of unicast signals. The fundamental limits of hybrid communications are investigated, along with power allocation algorithms that approach the hybrid capacity. Our results show that OFDMA for unicast offers the best hybrid performance and considerable gains over orthogonal multiplexing (e.g., TDM/FDM) can be achieved through interference-free overlay. In addition, we describe approaches to further improve the spectral efficiency and the broadcast coverage through multicell collaboration.