Heung-Jae Im

A novel adaptive beamforming algorithm for antenna array CDMA systems with strong interferers

Blind beamforming based on the maximum signal-to-noise ratio (MSNR) can improve the performance of an array system only when the processing gain of the given code-division multiple-access (CDMA) system is high enough such that the desired signal can become dominant after despreading (see Choi, S. and Shim, D., IEEE Trans. Veh. Technol., vol.49, p.1793-1806, 2000; Choi, S. and Yun, D., IEEE Trans. Antennas Propagat., vol.45, p.1393-1404, 1997). We consider a maximum signal-to-interference-plus-noise ratio (MSINR) beamforming. The MSINR performance criterion is chosen to deal with strong interferers effectively. It is shown that blind MSINR beamforming is possible by directly utilizing the input and output signals of correlators of the CDMA systems. In addition, we propose an adaptive beamforming algorithm at a lower computational complexity - about O(7.5N) - where N is the number of antenna elements of the array system. Simulation results are presented in various signal environments to show the performance of the proposed adaptive algorithm.

Performance analysis of smart antenna test-bed operating in a wide-band CDMA channel

In this paper, we present a performance analysis of a smart antenna system operating in a wide-band CDMA wireless-local-loop channel using a beam-forming module (BFM) that has been implemented on a digital signal processor (TMS320C6701) board. We first show the results of computer simulations obtained from the modeled received (RX) signals through a test-bed system consisting solely of baseband signal processing parts, i.e., modeled RX data-generating PC, BFM for computing the optimal weight vector and interfacing module. A test-bed system of the entire base station is then implemented to evaluate the adaptive beam-forming function with the actual wireless signals. This test-bed system includes several subscribers, as well as the array antenna, RF modules, and other receiving parts required at the cell site.

Implementation of a smart antenna test-bed

In this paper, we present a hardware implementation of a smart antenna test-bed for real-time simulation of our adaptive beamforming algorithm. The test-bed consists of a PC (RX-data generation), interface module, and beamformer (weight computation) implemented on a stand-alone PCB with TMS320C6701. The performance improvements are shown in terms of BER and achievable capacity in a wide-band CDMA (code division multiple access) WLL.

Implementation of smart antenna base station for IS-2000 1X

This paper presents performance analysis of a smart antenna base station (SABS) that has been implemented for IS-2000 1X system. The SABS introduced in this paper includes all the subsystems required in a commercial base station such as array antenna elements, RF unit, channel card, beamforming unit, GPS unit, etc. The channel card contains subsystems for generating the transmitting data, retrieving the received data, and controlling the transmitting and receiving parts. The data retrieval module, which performs the despreading function, has been realized on an FPGA board in accordance with the array structure and adaptive beamforming procedure of the proposed SABS. In order to provide a proper downlink beamforming as well as uplink beamforming, we present a novel procedure for practically usable accurate calibration. The performance analysis of the proposed SABS presented in this paper is based on experimental results provided by the commercial mobile terminals in PCS (personal communication service) frequency band.

Implementation of smart antenna base station with a novel searcher and tracker for CDMA 2000 1X

This paper presents a performance analysis of smart antenna BTS (base-station transceiver subsystem) for the frame error rate (FER) and detection probability in PN-code acquisition, which provides a tremendous increase in communication capacity.

Performance analysis of a smart antenna system utilizing a test-bed implemented on a DSP board

In this paper, we present a performance analysis of the smart antenna system operating in a wide-band CDMA (Code division multiple access) WLL (Wireless local loop) channel through a test-bed that has been implemented on a DSP (TMS320C6701) board. The test-bed consists of a PC (for generating the RX data), beam-former (i.e., a stand-alone PCB for weight computation), and an interfacing module. The performance improvements compared to a normal base station system consisting of a single antenna are shown in terms the BER (bit error rate) in the wide-band CDMA WLL channel.

Performance improvement of smart antenna system in terms of searching and tracking capability due to phase diversity technique in IS2000 1X signal environment

This paper presents a performance analysis of a smart antenna system (SAS) with a special emphasis on the searching and tracking capability. For both searching and tracking procedure, the SAS consisting of 6 antenna elements in this paper generates the test-variable from the sum of received signal power obtained at each of the 6 antenna channels. From various computer simulations, the proposed SAS exhibits a considerable improvement in terms of detection/false alarm probability, synchronisation-loss probability as well as the final bit error rate (BER), frame error rate (FER), and the communication capacity.

Implementation of a smart antenna test-bed for wide-band CDMA WLL channel

We present a performance analysis of a smart antenna system operating in a wideband CDMA (code division multiple access) WLL (wireless local loop) channel. The analysis is done using a test-bed consisting of a data-generating PC, interfacing module, and weight-generating module. The performance improvements provided by the proposed smart antenna system are shown in terms of the BER (bit error rate) and achievable capacity (allowable number of subscribers with a given BER) in a wide-band CDMA WLL channel.