Switched Multi-Radio Transmission Diversity for Non-Collocated Radio Accesses

We evaluate the spectral efficiency gains observed through multi-radio transmission diversity (MRTD), whereby packets of data are jointly scheduled for downlink transmission over multiple independent radio accesses. We specifically address downlink switched MRTD employed across macro- and pico-cellular radio accesses with non-collocated base stations in a hierarchical cell structure. It is shown that while significant gains can be achieved via MRTD among collocated macro-cell (or pico-cell) base stations, tight cooperation across non-collocated macro-and pico-cell base stations is only beneficial for a small subset of possible geometries. The impact of CQI reporting delays is also investigated