Achieving Maximum Capacity From Spatially Constrained Dense MIMO Systems
نویسندگان
چکیده
In this paper, we derive a spatial precoding (power loading) scheme which eliminates the effects of non-ideal antenna placement on the capacity performance of spatially constrained dense MIMO systems. The precoder is derived based on fixed and known parameters of MIMO channels, namely the antenna spacing and antenna placement which are known at the transmitter. With this design, the precoder is fixed for fixed antenna placement and the transmitter does not require any feedback of channel state information (partial or full) from the receiver. We study the capacity performance of this fixed scheme vs traditional equal power loading scheme when applied on spatially constrained 1-D and 2-D antenna arrays. We numerically show that, unlike the equal power loading scheme, new scheme is capable of achieving the theoretical maximum capacity available for a fixed region of space. In addition, we derive a second precoding scheme is derived by exploiting the non-isotropic scattering distribution parameters at the transmitter. With this scheme, the receiver needs to estimate these parameters and feed them back to the transmitter periodically. Using this scheme, we show that accurate feedback of scattering distribution information always helps to improve the capacity of 2-D antenna arrays for all angular spread values while 1-D antenna arrays do not provide capacity improvements under some scattering scenarios.
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