Seong-Ho Hur

Sum Rate Analysis of a Reduced Feedback OFDMA Downlink System Employing Joint Scheduling and Diversity

We consider joint scheduling and diversity to enhance the benefits of multiuser diversity in an orthogonal frequency-division multiple access (OFDMA) downlink system. The OFDMA spectrum is assumed to consist of NRB resource blocks and the reduced feedback scheme consists of each user feeding back channel quality information (CQI) for only the best-NFB resource blocks. Assuming largest normalized CQI scheduling and a general value for NFB, we develop a unified framework to analyze the sum rate of the system for both the quantized and nonquantized CQI feed- back schemes. Based on this framework, we provide closed-form expressions for the sum rate for three different multiantenna transmitter schemes; transmit antenna selection (TAS), orthogonal space time block codes (OSTBC) and cyclic delay diversity (CDD). Furthermore, we approximate the sum rate expression and determine the feedback ratio (NFB/NRB) required to achieve a sum rate comparable to the sum rate obtained by a full feedback scheme.

Sum rate enhancement by maximizing SGINR in an opportunistic interference alignment scheme

In this paper, we consider an opportunistic interference alignment scheme exploiting multiuser diversity in the interference-limited uplink cellular networks. The spatial degrees of freedom afforded by multiple receive antennas are partitioned into the signal dimension and interference dimension. We propose a method to enhance the sum rate by maximizing the signal to generated interference and noise ratio (SGINR) in each user. When multiple antennas are available in each user, we also propose a transmit beamforming scheme at each user in the direction to further maximize SGINR. We show that the proposed methods greatly improve the sum rate compared to the conventional opportunistic scheme.

Performance of a Reduced Feedback OFDMA System Employing Joint Scheduling and Diversity

We consider joint scheduling and diversity to enhance the benefits of multiuser diversity in a multiuser OFDMA scheduling system. The OFDMA spectrum is assumed to consist of

Determination of cyclic delay for CDD utilizing RMS delay spread in OFDMA multiuser scheduling systems

N_{RB}

Cell search apparatus and method in a mobile communication system

resource blocks and the reduced feedback scheme consists of each user feeding back only the best-

Cell search method in discontinuous reception mode in a mobile communication system

N_{FB}

Cell search method in UMTS

signal to noise ratios. Assuming maximum SNR scheduling, we develop a framework to analyze the performance of both adaptive and non-adaptive rate schemes for a general value of

Apparatus and method for generating reference timing in a CDMA mobile communication system

N_{FB}

Apparatus and method for estimating initial frequency offset in an asynchronous mobile communication system

. Based on this framework, we provide closed-form expressions for the sum rate and the bit error probability when transmit antenna selection is employed at the transmitter and maximal ratio combining is utilized at the receivers.

COMMUNICATION SYSTEM WITH CELL SELECTION MECHANISM AND METHOD OF OPERATION THEREOF

The multiuser diversity gain increases with the degree and dynamic range of channel fluctuations. For a multi-antenna orthogonal frequency division multiplexing (OFDM) system operating in a channel with limited fluctuations, cyclic delay diversity (CDD) was proposed to increase frequency selectivity. This is achieved by introducing a cyclic delay between the different transmit antennas thereby increasing the effective number of paths in the resulting channel. In this paper, for a multiuser system, we propose a scheme to determine peruser optimal cyclic delay value based on the knowledge of the root-mean-square (RMS) delay spread of the channel. We show that the proposed technique achieves better performance than a conventional fixed cyclic delay scheme and that the throughput is very close to the optimal sum rate possible with CDD.