ime-frequency resource block. However, other use cases of MIMO systems, when the same data stream is sent from the different antennas, are generally called diversity schemes. That is, we can differentiate the fol- lowing two primary use cases of MIMO systems: Spatial multiplexing can be employed in cases when the channel rank Vch > 1 (and likewise the transmission rank Vtr > 1) and the SINR is high enough. Because the transmission power has to be shared between the streams sent from the different antennas, the SINR per stream will be lower compared to a single antenna transmission. Therefore, the spatial multiplexing trans- mission mode is beneficial only if the original SINR was high enough SO that the loss in terms of channel capacity due to the lower SINR per stream is compensated by the multiplication of the transmission streams. In other words, this means that the original SINR has to be on the flat part of the Shannon curve, where a 1/2, 1/3, decrease of the SINR does not result in a 1/2, 1/3, decrease of the channel capacity. It is also often said that the spatial multiplexing is most suitable to increase the peak rate in the inner part of the cell, where the channel conditions are favorable. In contrast to spatial multiplexing, diversity schemes are typically used for bad SINR scenarios in order to improve the SINR by exploiting diversity gains among the spatial channels of the multiantenna system. In the case of the diversity schemes, the transmission rank is Vtr=1 (i.e., only one piece of data is transmitted in a given time-frequency resource block, meaning © 2009 by Taylor & Francis Group, LLC Long Term Evolution: 3GPP LTE Radio and Cellular Technology that the one and the same data stream is transmitted from each transmit antenna port). There are many different variants of diversity schemes; the most relevant examples from an LTE system point of view include: transmit diversity beam forming space-time block codes (STBCs) (not used in LTE) space-frequency block codes (SFBCs) cyclic delay diversity (CDD