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Multiuser detection using blockwise successive interference cancellation in DS/CDMA systems
Kim, Daejoong,Kang, Changeon 연세대학교 전자정보통신연구소 1998 전자 정보 통신 논문집 Vol.3 No.1
The performance of a new multiuser detector in combination with a blockwise successive interference cancellation (BSIC) scheme for DS/CDMA systems is propose. The BSIC detector consists of the multistage blocks, which include the power-ranked users to be cancelled. The BSIC scheme is simulated using coherent QPSK modulation under AWGN and Rayleigh fading environments. From the practical implementation point of view, a promising candidate among the multiuser detectors is the SIC detector due to the lower complexity compared to other multiuser detectors. The SIC scheme, however, has two main problems. The first problem is that each user, once selected, makes no further contribution and refinement for subsequent operations. The second problem is that the hardware complexity of the SIC scheme grows linearly as the number of users increase. We compare the performance and the hardware complexity of the SIC scheme and the BSIC scheme. The experimental results show that as the size of block at the BSIC scheme increases, the performance of the BSIC scheme is improved, outperforming the SIC scheme. The BSIC scheme has low hardware complexity.
A Soft Handoff with Dynamic Thresholds for CDMA Cellular Systems
Hwang, Seonho,Kang, Changeon 연세대학교 전자정보통신연구소 1998 전자 정보 통신 논문집 Vol.3 No.1
Traffic nonuniformity degrades the performance of CDMA cellular systems. This paper presents a new algorithm called the Soft Handoff with Dynamic Thresholds (SHDT) which reduces the performance degradation due to traffic nonuniformity in CDMA cellular systems. Unlike the conventional fixed handoff thresholds, the proposed algorithm allows the handoff thresholds (T_DROP) to vary dynamically according to the traffic density of each cell. this algorithm has been implemented by means of computer simulation and the results show that SHDT improves the overall CDMA system performance in terms of outage probability. The SHDT algorithm can easily be applied to CDMA cellular systems without any modification.
A Direction Based Soft Handoff Call Control Scheme in CDMA Cellular Systems
Jeon, Hyounggoo,Kang, Changeon 연세대학교 전자정보통신연구소 1998 전자 정보 통신 논문집 Vol.3 No.1
In this paper, a new direction-based handoff call control scheme (DBHCCS) for CDMA cellular systems is proposed. In the proposed scheme, a neighbor base station ignores unnecessary soft handoff calls requested by mobile stations which are not approaching the neighbor base station, while protecting real soft handoff calls by employing a queue. We proposed a new method of determining the priorities of queued handoff calls. In this method, a mobile station predicts the time its handoff call is forcedly terminated, by using the changing rate of the received pilot strength from the serving BS and using the current time broadcast by the sync channel of the serving BS as a reference time. The service priority of queued handoff calls is determined based on the predicted forced termination time reported by mobile stations. In this paper, the performance of the DBHCCS is compared with that of the first-in/first-out (FIFO) scheme [1] and measurement-based prioritization scheme (MBPS) [2]. The simulation results show that the probability of new call blocking for the DBHCCS is lower than that of the FIFO scheme or MBPS queuing discipline. it is also showed that the probability of forced termination for the DBHCCS is less than or equal to that of the conventional CDMA cellular system with MBPS queuing discipline.
Limitations in the Code Acquisition Performance for Adaptive Filter Versus Correlator
Takki Yu,Changeon Kang,Daesik Hong IEEE Signal Processing Society 2006 IEEE signal processing letters Vol.13 No.11
<P>In this letter, we compare the code acquisition performance of the adaptive filter to that of the correlator in direct sequence spread spectrum (DS/SS) systems. The test variables used in the code acquisition are statistically analyzed for both schemes, and then, the obtained results are used in comparing the detection and false-alarm probabilities. Analysis and simulation results show that the correlator outperforms the adaptive filter under most acquisition environments</P>