Seung Hoon Shin

Power control and QoS of a CDMA based hierarchical cell structure network

The hierarchical cell structure is needed for different requirements: large cells guarantee continuous coverage, while small cells are necessary to achieve good spectrum efficiency and high capacity. In this paper a CDMA system in macro/micro cell structure is investigated. We propose an adaptive scheme of controlling cell size according to time-varying traffic distribution in a macro/micro overlaid cell environment. This aims to bring communications quality in both macro-cell and micro-cell to a target quality level. Simulation results show that the proposed scheme effectively controls the time-varying traffic fluctuations and provides an enhanced performance.

Power control for CDMA macro-micro cellular system

The hierarchical cell structure is needed for different requirements: large cells guarantee continuous coverage, while small cells are necessary to achieve good spectrum efficiency and high capacity. In this paper, the CDMA system in macro/micro cell structure is investigated. We propose an adaptive scheme of controlling the cell size according to a time-varying traffic distribution in a macro/micro overlaid cell environment. This aims to bring the communications quality in both the macro-cell and micro-cell to a target quality level. Simulation results show that the proposed scheme effectively controls the time-varying traffic fluctuations and provides an enhanced performance.

Multiuser detection for DS/CDMA systems with adaptive antenna array

Recently, the study on adaptive antenna array systems has been investigated to combat multiple access interference for CDMA systems. An adaptive antenna array can cancel out an undesired signal using beamforming. However, if there interfering signals from undesired users with the same arrival angle as that of a desired user, an adaptive antenna array cannot suppress it. This paper proposes an adaptive antenna array including a multiuser detection unit to cancel out remaining interference at the same beamforming region (arrival angle). The performance analysis of the proposed system is developed for frequency selective Rayleigh fading channels. Simulation results show that the proposed system provides a significantly enhanced performance.

Multiuser receiver with multipath diversity for DS/CDMA systems

Several multiuser detectors have been previously proposed to combat multiple-access interference and the near-far problem for CDMA systems. Multiuser detectors, exploiting knowledge of other users to cancel multiple-access interference, have the potential to provide a significant increase in capacity of CDMA systems. In this paper, we propose a suboptimal multiuser receiver that combines multipath diversity reception, multiuser detection and decision-feedback cancellation. Also, the performance analysis of the proposed multiuser receiver is derived for frequency selective Rayleigh fading channels. Numerical results show that the proposed receiver provides a significantly enhanced performance.

An Efficient Scheme for Transmit Antenna Diversity with Limited Feedback Channel Rate

In this letter, we propose an efficient closed-loop transmit (Tx) diversity scheme that works well for high mobility as well as low mobility. The proposed scheme exploits a quantized weight vector codebook designed by separating it into gain and phase codebooks. Simulation results reveal that the proposed scheme can provide a significant advantage in both complexity and flexibility over conventional methods.

Adaptive Linear Detectors in Space-Time Block Coded Multiuser Systems

In this letter, we propose adaptive linear detectors in space-time block coded multiuser systems, by exploiting a particular property of the minimum mean square error multiuser detector. The proposed scheme can provide much faster convergence than the existing adaptive scheme [5] and so lower the system overhead requirements.

EFFECTIVE ADMISSION CONTROL FOR POWER-CONTROLLED DS-CDMA SYSTEMS

Effective call admission control (CAC) is one of the most important techniques to provide the desired quality of service (QoS) in wireless networks. This paper investigates the call admission contr...