Transmit diversity vs. spatial multiplexing in modern MIMO systems

A contemporary perspective on the tradeoff between transmit antenna diversity and/nspatial multiplexing is provided. It is argued that, in the context of most modern wireless/nsystems and for the operating points of interest, transmission techniques that utilize/nall available spatial degrees of freedom for multiplexing outperform techniques that explicitly/nsacrifice spatial multiplexing for diversity. In the context of such systems, therefore,/nthere essentially is no decision to be made between transmit antenna diversity and spatial/nmultiplexing in MIMO communication. Reaching this conclusion, however, requires that/nthe channel and some key system features be adequately modeled and that suitable performance/nmetrics be adopted; failure to do so may bring about starkly different conclusions. As/na specific example, this contrast is illustrated using the 3GPP Long-Term Evolution system/ndesign