System Evaluation of MU-MIMO and Multi-cluster Allocation in LTE-Advanced Uplink

Multi-user multiple-input and multiple-output (MU-MIMO) is a key technology for enhancing the spectrum efficiency in cellular mobile communication systems. In the Long Term Evolution (LTE) -Advanced, orthogonal cover code (OCC) has been introduced for the uplink demodulation reference signal (DMRS), which provides orthogonality of the DMRS between different user equipment (UEs). This enables different bandwidth allocations for paired UEs of MU-MIMO, which enables flexible frequency selective scheduling and UE pairing. On the other hand, to further enhance the spectrum efficiency in LTE-Advanced, non-contiguous frequency resource allocation based on clustered discrete Fourier transform-spread orthogonal frequency division multiplexing (clustered DFT-S-OFDM), i.e., multi-cluster transmission, is supported. This paper presents frequency and spatial resource allocation for MU-MIMO with multi-cluster transmission, and evaluates the system performance of MU-MIMO in conjunction with multi-cluster transmissions via system level simulations considering the bandwidth allocation restriction for the paired MU-MIMO UE. It is shown that the combination of multi-cluster transmission and MU-MIMO with different bandwidth allocations significantly improve the performance.