Modulation-Mode Assignment for SVD-Assisted Downlink Multiuser MIMO Systems

Andreas Ahrens and Mosa A. Abu-Rgheff


Multiple-Input Multiple-Output System, Singular-Value Decomposition, Bit Allocation, Wireless Transmission


Multiuser multiple-input multiple-output (MIMO) downlink (DL) transmission schemes experience both multiuser interference as well as inter-antenna interference. Instead of treating all the users jointly as in zero-forcing (ZF) multiuser transmission techniques,the investigated singular value decomposition (SVD) assisted DL multiuser MIMO system takes the individual user's channel characteristics into account. This translates to a choice of modulation constellation and transmitter power and, in our proposed system, to a choice of number of activated user-specific MIMO layers. The performed joint optimization of the number of activated MIMO layers and the number of bits per symbol along with the appropriate allocation of the transmit power shows that not necessarily all user-specific MIMO layers has to be activated in both frequency selective and frequency non-selective MIMO channels in order to minimize the overall BER under the constraint of a given fixed data throughput.

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