Sungsoo Ahn

Design of CIC roll-off compensation filter in a W-CDMA digital IF receiver

In a digital intermediate frequency (IF) receiver, decimation is performed to reduce the computational complexity and cascaded integrated comb (CIC) filter is used together with the decimation as an anti-aliasing filter. However, the CIC filter generates the roll-off phenomenon in the pass-band, which causes the receiving performance to be considerably degraded due to the distorted pass-band flatness of the receiving filter. In this paper, we propose a design method of the CIC roll-off compensation filter to reduce the performance degradation due to the roll-off characteristics of the CIC filter for a W-CDMA digital IF receiver. The performance of the proposed CIC roll-off compensation filter is confirmed through computer simulation in such a way that bit error rate (BER) is minimized by compensating the roll-off characteristics. In addition, the proposed method can be used in the design of a digital-to-analog (DAC) compensation filter and interpolator in the transmitter.

Performance Analysis of Smart Antenna System Using a Phase Update Method in W-CDMA Signal Environment

This paper proposes a novel blind adaptive algorithm for computing the weight vector of an antenna array system. The new technique utilizes a phase update algorithm to obtain the weight vector maximizing the SINR (Signal to Interference plus Noise Ratio) of the received signal. It is observed that the proposed algorithm generates a suboptimal weight vector with a linear computational load(O(6N+8)). From the various simulations, it is confirmed that, when the signal environment becomes adverse, the proposed algorithm outperforms the conventional one in terms of the communication capacity by about 3 times. Applying the proposed algorithm to W-CDMA mobile communication system, we have found that both communication capacity and communication quality are significantly improved

Design and implementation of GPU-based turbo decoder with a minimal latency

Decoding latency of the turbo decoder has been a serious problem in real-time processing of communication systems. This paper presents a novel procedure of reducing the latency of the turbo decoder which has been implemented with GPU (Graphic Processing Unit). The main contribution of this paper is to present an efficient procedure of reducing the latency of GPU-based turbo decoder through an efficient parallel processing of maximum a posteriori (MAP). Through experimental tests, we have verified that the proposed turbo decoder reduces the latency from 34,767μs to 273μs per iteration.

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.

A study on hierarchical policy model for managing heterogeneous security systems

As the number of security system to be managed grows, the task of managing these security systems depend on numerous system and vendor specific issue. To prevent the managers from drowning in complicated detail, the managerpsilas policy of conceptual level needs to be translated to low-level policy which systems understand. Polices which are derived from the goal of management define the desired behavior of various heterogeneous systems and networks, and specify means to enforce this behavior. In this paper, we present a hierarchical policy model consist of five levels which are conceptual policy level, goal-oriented policy level, target policy level, process policy level and low-level policy and is introduced to show how a policy system can be realized.

A novel gateway placement method adopting CEM for Wireless Sensor Network

This paper presents an optimum placement of Gateways operating in Wireless Sensor Networks (WSNs). The full search method of Gird deployment requires tremendous amount of computation. A novel algorithm for resolving the complexity problem is proposed. The new algorithm utilizes the Cross Entropy Method (CEM) for the maximum network performance with a lot less operations compared to the full search method. Applying the proposed method to various practical situations such as health care system, Electronic Shelf Labeling (ESL), etc, we have verified the superb throughput performance of the proposed algorithm using OPNET simulator. Compared to the full search, which is ideal method, the proposed method provides nearly 98% throughput in various experimental tests.

Performance analysis of MIMO system utilizing the detection algorithm

This paper presents a performance analysis for MIMO system using detection algorithm based on zero-forcing and maximum likelihood. Proposed algorithm provides optimal gain on a real-time basis arbitrarily according to angle spread produced at every snapshot. From the result of performance analysis through various simulations in WiBro, it is confirmed that proposed method is far superior compare to without detection algorithm.

Performance analysis using the two kinds of receiving gain of smart antenna in IS20001X system

In order to achieve the diversity gain with antenna arrays for moderate angle spread, we propose a beamforming algorithm that utilizes multiple eigenvectors, and apply this beamforming technique to IS2000 1X systems equipped with antenna arrays under a time-varying multipath fading channel environment. In the proposed beamforming method, the channel vector has been estimated using two basis vectors. Since the proposed beamforming algorithm utilizes two-dimensional signal subspace, it provides better performance than the conventional beamforming algorithm, which uses one beamforming signal space.

Performance analysis of a antenna array system using a new beamforming algorithm in the CDMA2000 1x wireless communication

In order to achieve the maximum gain along the desired signal, this paper propose beamforming algorithm that utilize Generalized on-off algorithm. The new algorithm that provides a maximum SINR(Signal to Interference plus Noise Ratio) based on the conventional on-off algorithm for obtaining optimal weight vector. Also, in this paper, we present a novel demodulation method enhancing the performance of smart antenna by using the pilot channel of CDMA2000 1X channel to obtain the exact weight vector. From various computer simulation, we could conform that the proposed algorithm has superior performance in terms of SER(Symbol Error Rate) than conventional algorithm with multipath fading.

Performance analysis of a smart antenna system using a novel beamforming algorithm in the CDMA2000 1X channel

In order to achieve the maximum gain along the desired signal, This work propose a beamforming algorithm that utilizes the generalized on-off algorithm. Also, we present a novel demodulation method enhancing the performance of the smart antenna by using the pilot channel of the CDMA2000 1X channel to obtain the exact weight vector.