## FANDOM

186 Pages

In this thesis, we consider effective transmission methods for limited feedback multiuser multiple-input and multiple-output (MU-MIMO) systems for wireless cellular networks. As candidate MU-MIMO solutions, we consider suboptimal linear precoding and optimal dirty paper coding (DPC) to optimize the performance of cellular communication systems with the multiple antenna configuration.

For relay-assisted wireless communications, we define effective spectrum efficiency and find the optimal resource allocation based on the defined effective spectrum efficiency.

## Multiuser MIMO with PU2RC Precoding Edit

In WCDMA/HSDPA of 3GPP, several multiple-input multiple-output (MIMO) techniques have been proposed and in progress of performance evaluation for comparison. Most MIMO candidates in HSDPA have been generally designed based on a point-to-point communication, which means that a single-user throughput is of their major concern. However, multiple users and user scheduling need to be considered in wireless packet transmission, so as to maximize system throughput. In this paper we propose the effective user scheduling technique in both space and time domains accompanying three main features, which are the spatial-beamforming, uplink feedback signaling, and advanced receivers. Furthermore, user scheduling is combined together with the modified SIC reception, which allocates all transmit antennas to the best user with SIC or each transmit antenna to different users with MMSE. Simulation results show that the proposed scheme has higher user diversity gain than the other MIMO candidates in terms of achievable throughput.

t.b.d.

## Multiuser MIMO with DPC Precoding Edit

Recently, a number of techniques have been introduced to exploit multiuser diversity of a wireless multiple-input multiple-output (MIMO) broadcast channel (BC) that consists of a base station with $t$ transmit antennas and $K$ users with multiple antennas. However, prior works have ignored the rate overhead associated with feedback of MIMO BC channel state information at transmitter (CSIT), which is roughly $K$ times larger than single-user MIMO CSIT (i.e., it is $\mathcal{O}(tr)$ where $r = \sum_{k=1}^K r_k$ and $r_k$ is the number of antennas at the $k$th user). Considering the amount of feedback signaling, quantization is a necessity for effective feedback transmission as a form of partial CSIT. In this paper, we propose the greedy multi-channel selection diversity (greedy MCSD) scheme based on block MMSE QR decomposition with dirty paper coding (block MMSE-DP), where partial CSIT is almost sufficient. The sum-rate performance of our novel scheme approaches extremely close to the sum capacity of MIMO BC as the number of users increases, whereas the feedback overhead is reduced by a factor of $2t^3/L(t^2-t)$, in which $L$ is the number of active channel vectors. Simulation results validate the expectation from the analysis. In addition, the proposed scheme is shown to be appropriate for reconfigurable implementation.