• Journal of Institute of Control, Robotics and Systems
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• v.9 no.12
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• pp.1065-1070
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• 2003

We present a power control with variable state feedback gain (VFPC) to improve outage convergence rate of distributed constrained power control. The variable state feedback gain includes the information of the desired SIR changes and must be a decreasing sequence for the convergence. The proof of the convergence is given. The proposed algorithm can improve the outage convergence rate and SIR (Signal to Interference Ratio) response at transient as well as at steady state. The simulation results are given to demonstrate the feasibility of the proposed scheme.

• Journal of Communications and Networks
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• v.9 no.1
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• pp.28-33
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• 2007

Estimated channel information, especially multipath length and multipath channel of the desired user, is necessary for most previously reported linear blind multiuser detectors in code division multiple access (CDMA) systems. This paper presents a new blind intersymbol decorrelating detector in asynchronous CDMA systems, which uses the cross correlation matrix of the consecutive symbols. The proposed detector is attractive for its simplicity because no channel estimation is required except the synchronization of the desired user. Compared with other reported multiuser detectors, simulation results show that the proposed detector provides a good performance when the active users have significant intersymbol interference and the multipath length is short.

• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.1952-1955
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• 2002

Multiple access interference (MAI) and multi path interference(MPI) degrades the system performance in the DS-CDMA(direct-sequence code-division multiple- access)systems .0 this paper, a generalized construction method fer 2$\^$n/(n=1,2,3) phase preferred pairs(PP) with zero-correlation duration (ZCD) of (0.5N+1) chips is proposed. 2$\^$n/(n=1,2,3) phase ZCD code sets with ZCD and enlarged family sizes are generated by carrying out a chip-shift operation of the preferred pairs . The properties of the proposed codes are effective for the cancellation of MAI and MPI in DS-CDMA Systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.3B
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• pp.251-258
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• 2002

In this paper, an adaptive convolutional coding method in multicarrier direct sequence code division multiple access (DS/CDMA) systems is considered. In order to accommodate a number of coding rates easily and make the encoder and decoder structure simple, we use the rate compatible punctured convolutional (RCPC) code. To achieve maximum data throughput, an adaptive rate system based on the channel state information (the SINR estimate) is proposed. We show that the proposed adaptive rate convolution coded multicarrier DS/CDMA systems can enhance spectral efficiency and provide frequency diversity.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.12
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• pp.1286-1299
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• 1991

In this paper we present a multiple capture model for common spreading code CDMA packet radio systems with star topology. Basic equations for the collision free, header detection. and multiple capture probabilities are derived at the central receiver. Link performances. including the average number of packet captures, allowable number of simultaneous transmission, and system throughput are theoretically evaluated for a hybrid system. combining envelope header detection and differential data detection, Using the Block Oriented Systems Simulator(BOSS), simulations were carried out for the central receivers with envelope or differential geader detection, It is shown that for a threshold approx-imation to the probability of data packet success, the mulyiple capture model significantly improves system throughput.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.9
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• pp.1748-1758
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• 1994

Recently, the demand of mobile communication is rapidly increasing. Also, not only the voice service but also the nonvoice services such as data, FAX, and image service are required. Therefore, in this paper, the voice/data intergraed service methods that will be utilized as a basic core technology of the PCS systems are proposed and their performances are analyzed and compared by computer simulation. According to the simulation results, it could be seen that the performance of voice/data integrated PR-CDMA method is better than that of voice/data integrated broadband CDMA method using a dedicated terminal or a voice/data integrated terminal. The reason is that the voice/data integrated PR-CDMA method can overcome the weak points of CDMA protocol, such as a limitation of the fixed CDMA logical channel number and a falling-off in channel utilization, by using PRMA protocol as a multiple access method that the terminals to which a CDMA logical channel is assigned compete.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.3
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• pp.75-82
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• 2010

Korea has made a plan to allocate CH 14~CH 51 (470 MHz~698 MHz) for DTV. This paper assumes that DTV operates on CH 51 (692 MHz~698 MHz) and CDMA system operates on CH 52 (698 MHz~704 MHz) in spare band. Minimum Coupling Loss (MCL) method to get protection distance and Spectrum Engineering Advanced Monte Carlo Analysis Tool (SEAMCAT) to get guard band through 5 % interference probability are used. The protection distance is required to be 665.67 km at close frequency offset of 698.625 MHz between DTV transmitter and CDMA Base Station (BS) receiver. The required guard band between DTV transmitter and CDMA Mobile Station (MS) receiver is 5 MHz for the worst case of rural environment. There is no serious impact between CDMA MS transmitter and DTV receiver. The required guard band between CDMA BS transmitter and DTV receiver is 6.25 MHz for the worst case of urban environment. The analysis results may offer a reference and be helpful for considering interference between DTV and other communication systems.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.6
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• pp.1060-1067
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• 2004

In a CDMA system, the rapacity is variable and mainly depends on multiple access interference. The multiple access interference has a deep relationship with transmitted or received power. The capacity of CDMA2000 1x system is considered to be limited by the forward link capacity. In this paper, we show that the transmitted power can represent the total cell load and we propose a load control scheme for CDMA2000 1x system. CDMA2000 1x system has fast power control scheme and we can measure forward link cell load by using total transmitted power. In the proposed algorithm, by monitoring the total transmit power, we can simply adjust data rate to channel conditions and efficiently use radio resources. The proposed algorithm is practical algorithm to implement in the power controlled CDMA systems and enhances the system throughput and quality of service(QoS)

• Journal of Internet Computing and Services
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• v.7 no.3
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• pp.41-51
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• 2006

In the case of CDMA-based packet data systems such as 1xEV-DO which are designed to support high rate services, BSs transmit data packets with a maximum power based on time multiplexing mode such that only one user can be serviced at a time. In this paper, we propose a joint power allocation and scheduling algorithm for 1xEV-DO-like systems in which we adopt a code division multiplexing (CDM) transmission method in the downlink common channel in order to utilize channel orthogonality such that we can serve more than one user at a time slot especially when there exist remaining resources after serving the firstly selected user by the scheduler. Simulation results demonstrate that the proposed scheme can improve the performances of conventional schemes such as the maximum rate and the proportional fair algorithms.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.10B
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• pp.1995-2003
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• 1999

Since the cross-correlation function which is due to communication channel distortion or interference is not orthogonal, near far problem and multi-user interference are generated in the DS-CDMA system. Those problems degrade performance of the system so that the efficient algorithm to suppress the interference in the DS-CDMA system is required. In this paper, a blind adaptive interference suppressor using constant modulus algorithm is proposed. Simulation results present that the gain of SIR for the blind adaptive receiver is about 7[dB] at steady state over Gaussian channel in forward channel. The gain of noise to interference ration is about 4[dB] over Rayleigh fading channel, is about 11[dB] over multipath channels. Thus the proposed receiver has higher performance than a conventional receiver in the DS-CDMA system.