Yusuk Yun

Phase Diversity for an Antenna-Array System With a Short Interelement Separation

This paper presents a simple procedure of obtaining a diversity gain in an antenna-array system with a short interelement separation, typically less than the carrier wavelength. The new technique provides a diversity gain through a noncoherent combination of received signals at each antenna element. The diversity gain arises because, as the number of signal components of the received signal at each antenna element becomes large enough and as the arrival angle of each signal component is distinct from one another, which is a general signal circumstance in most practical code division multiple access (CDMA) signal environments, the amplitudes of the received signals become nearly independent due to the phase difference among the received signals. The diversity gain was referred to as ldquophase diversityrdquo in this paper. The proposed technique is first theoretically analyzed to estimate the performance in terms of pseudorandom-noise-code acquisition, which is verified through extensive computer simulations. Then, through the experimental results that are obtained from a CDMA array-antenna base station system, it has been shown that the performance of noncoherent detection is proportionally improved to the number of antenna elements.

Prototype implementation of adaptive beamforming-MIMO OFDMA system based on IEEE 802.16e WMAN standard and its experimental results

This paper details the downlink performance analysis of a MIMO (Multi-Input Multi-Output) system that combines adaptive beamforming (ABF) and spatial multiplexing (SM) procedures. The combination of MIMO signal processing with ABF is applied to WiBro (Wireless Broadband), the South Korean orthogonal frequency division multiple access (OFDMA) system that follows the IEEE 802.16e standard. Performance analysis is based on the results of experiments and simulations obtained from a prototype system implementation and fixed-point simulator. Both the prototype experiments and simulations demonstrate that the ABF-MIMO OFDMA system improves the required signal to noise ratio (SNR) over the conventional MIMO OFDMA system by 3 dB (QPSK)/2.5 dB (16-QAM) for the frame error rate of 1% in the WiBro signal environments. From the implementation of the prototype system and its experimental results, we verify the feasibility of the ABF-MIMO technology for realizing a practical WiBro base station. Copyright

Smart antenna base station open architecture for SDR networks

Software-defined radio system architecture must be openly structured to various system standards. It should also provide capability for distributed processing, object-oriented design, and software controllability. This implies that the software to be used in the SDR system should be independent of a given hardware platform. In order to achieve these goals, the proposed SDR system utilizes modularization to maximize hardware reuse and design flexibility, which provides the system reconfigurability. The objective of this article is to provide an open architecture of a smart antenna base station (SABS) operating in the SDR with architecture that is object-oriented and software-controlled. For this purpose, the software and hardware of a SABS is first modularized and partitioned into modules, respectively. Then the interface among the modules is specified to determine the smart antenna application programming interface proper for the SDR network. The suitability of the proposed open architecture of SABS is verified through a design example of SABS implemented in accordance with the proposed architecture. The performance of the proposed system is shown in practical signal environments of CDMA2000 1X with commercial handsets operating at various data rates ranging from 9.6 to 153.6 kb/s in terms of frame error rate and signal-to-Interference-plus-noise ratio, which is dramatically improved through the nicely shaped beam pattern.

Novel automatic calibration technique for smart antenna systems

The problem of calibration has arisen because the phase characteristics of signal paths associated with each antenna in a smart antenna system (SAS) are different (in both receiving (RX) and transmitting (TX) modes). In this paper, we propose a simple and accurate calibration technique for eliminating the phase characteristic difference of the signal path associated with each antenna element in both RX and TX modes. Also, through the experimental data obtained from SAS, which has been implemented with the CDMA2000 1X standard, we confirm that the proposed technique has eliminated the characteristic difference.

Effect of HARQ Gain for a Smart Antenna System and a Diversity Antenna System in a TD-SCDMA System

Abstract This paper presents a performance analysis of a beam forming smart antenna array system and a diversity antenna array system operating in a time division synchronous code division multiple access (TD-SCDMA) signal environment which adopts Hybrid Automatic Request (HARQ). Performance analysis was based on a receiver structure proposed in this paper which combined the HARQ with a smart antenna system or a diversity antenna system. When there was no HARQ, the diversity system outperformed the smart antenna system by about 4.2 dB for a given Frame Error Rate (FER) if the number of antenna elements was set to six for both the receiving systems. However, the performance difference was reduced to 2 dB when HARQ was appended in the receiver, as HARQ gain can be exploited more efficiently in a smart antenna system. Comparing the 6-antenna beamforming system with the 2-antenna diversity system (which is more realistic than a 6-antenna diversity receiver in practice), we found that the former outperforms the latter by 3 dB due to the contribution of HARQ gain. Performance analysis is shown in terms of FER and the required system complexities in a TD-SCDMA mobile communication system.

Cognitive Radio in Multiple-Antenna Systems

This chapter presents an overview of the techniques used in a multiple-antenna 1 system and discusses the key issues in introducing cognitive radio (CR) technology. This discussion is followed by an explanation of the applications of the new system, which combines CR and multiple-antenna (MA) techniques. This chapter discusses the issues that combine the MA system with CR technology to increase the utilization of spectrum by sharing the spectrum among different systems as well as to improve the transmission efficiency by selecting the optimum transmission schemes under certain operational environments. It introduces the new functionalities, namely, radio environment observation and cognitive engine, in the MA system by adding cognitive capability. In such a system, besides signal detection and identification, the DOA and antenna correlation information should be obtained with the help of multiple antennas. By combining the environmental information, CE is able to select an optimum operation mode for the radio, depending on the related position between the primary units (PUs) and secondary units (SUs).

Performance analysis of PN-code acquisition in a DS/CDMA smart antenna system

This paper presents a performance analysis of PN-code acquisition in a smart antenna system operating in Rayleigh fading channels with various degrees of angular spread in the arrival direction of the received signal. It was determined that the performance enhancement provided by the smart antenna system is upper- and lower-bounded by the degrees of statistical independence between channel responses associated with each of the antenna elements. The performance of PN-code acquisition in a smart antenna system is then determined in accordance with the degree of angular spread in the range determined by the upper and lower bounds. The theoretical analysis for deriving the bounds shown in this paper is verified through extensive computer simulations with various angular spreads encountered in the Rayleigh fading channel.