• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.9
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• pp.1-8
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• 1999

In this paper, we propose and analyze a concatenated coding scheme for DS/CDMA systems in asynchronous channels. In the concatenated coding, bandwidth efficient $2^{2L-2}$-state ${\frac{L}{L+1}}$-rate 2-MTCM with biorthogonal signal constellation is used for the inner code, and $(2^{L-1},\;{\lceil}\frac{2^{L-1}}{L/2}{\rceil})$ RS code is use for the outer code. It is shown that we can get considerable performance gain over the uncoded system without sacrificing the data transmission rate. The proposed system can be used as a coding scheme for reliable and high speed integrated information services of mobile communication systems.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.10
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• pp.10-20
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• 1999

In this paper, we propose and analyze a multiuser receiver using a decorrelating filter and Viterbi decoders for trellis coded DS/CDMA systems with biorthgonal signal constellation in asynchronous channels. The biorthogonality is implemented by user signature waveforms and the decorrelating filter. The performance of the proposed system is investigated with emphasis on the asymptotic cases. It is shown that the proposed system can provide us with some coding gain and near-far resistance. We also analyze the performance of the proposed system with base-station antenna array.

• Proceedings of the Korean Society of Computer Information Conference
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• 2010.07a
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• pp.173-179
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• 2010

Currently, the communication systems are progressing two ways as the wireless and multimedia and these need big transmission capacity then before. In these circumstance, communication services existed as two different service forms which have different rates and characteristics. For example Voice/Video Services accept some errors but transmit on realtime, but Date Services don't need to transmit on realtime but have to retransmit if these have only one bit error. In Voice/Date Integrated traffics, it has big throughput that realtime voice/video data which could have some errors if integrated traffic is increased rapidly have transmission priority, then Data traffics which delay is accepted is sent after that. In this paper, I introduce the calculation method for various traffic when voice/data mixed traffics is transmitted to asynchronous unslotted ALOHA CDMA system proposed and the result is presented. And We can easily theoretical analysis for the system traffic and changing traffic using proposed solution in this paper.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.3
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• pp.360-369
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• 2001

This paper proposes the groupwise serial cross interference cancellation(GSCIC) algorithm for coherent detection and analyzes the groupwise serial block interference cancellation(GSBIC) and GSCIC algorithm for an asynchronous wideband DS-CDMA system in a single cell over multipath fading channels. In general, the GSIC algorithm can be grouped into two classes: i.e., GSBIC and GSCIC algorithm. In this paper, the proposed GSCIC algorithm is to improve the performance of the GSBIC algorithm. We compare the performance of the GSCIC and existing GSBIC algorithm in a multipath fading channel to that of the existing SIC algorithm. As a result, the performance of GSCIC algorithm is somewhat better compared with the GSBIC algorithm according to reduction factor $R_{f}$ and is similar to that of the SIC algorithm. And also, the GSBIC and GSCIC algorithms have the advantage that it can be analyzed system performance easily, changing the number of users within a user group according to system capacity.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.13 no.2
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• pp.120-126
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• 1988

In this paper the performance of the asynchronous Repeated FH/MFSK system for the CDMA(Code Division Multiple Access) was analyzed. Actually there was no difference in the probabilities of hit of frequency between Random Coding method and frequency hopping pattern vector suggested by Einarsso. Actual situation was adopted as a model in thie simulation, on the assumption thet;a:there was no Noise, Multipath propagation, b:there was only mutual interference. c:the number of users M was given. Also it was found that there is almost no deviation between the value calculated from the formula of word error probability expressed by bound and that obtained from this simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.3B
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• pp.179-187
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• 2002

This paper proposes and analyzes the iterative groupwise equal-delay interference cancellation(IGEIC) algorithm for coherent detection of an asynchronous wideband DS-CDMA system in a single cell over multipath fading channels. The IGEIC algorithm divide users in a system into several groups, and subtract out interference signal from the received signal as many as the number of users within a user group, iteratively. The IGEIC algorithm is also classified into the iterative groupwise equal-delay serial interference cancellation(IGESIC) algorithm and the iterative groupwise equal-delay parallel interference cancellation(IGEPIC) algorithm. In the case of perfect correlation for spreading codes, it shows that the performance of IGESIC and IGEPIC algorithm is the same after interference cancellation of as many as the number of users within a user group, but the performance of IGEPIC algorithm is superior to the IGESIC algorithm just before fecal cancellation within a user group. The results show that (he performance of the two proposed algorithms are also superior to the SIC algorithm by 3dB.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.2
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• pp.54-67
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• 2000

It is known that the performance of a DS-CDMA system mainly depends on Multiple Access Interference(MAI). The effect of MAI in a reverse link is larger than that of a forward link because of the absence of orthogonality among mobile stations. In this paper we investigate the effect of synchronous transmission in the reverse link, which is compared to the performance of asynchronous transmission in the reverse link. In addition, we consider the effect of interference from Mobile Stations(MSs) in a hand-over region. That is, if we assume that a MS is moving from a serving base station(sowing BS) to a target base station(target BS), the signal of the MS is not orthogonal with the signals of all other MSs within the target BS because the MS is only synchronized with the serving BS. Finally we suggest an interference cancellation scheme to reduce the interference from MSs in the region of hand-over, which can be one of solutions for the capacity degradation due to interference from the MSs in the hand-over region in reverse link synchronous transmission.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.1
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• pp.1-10
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• 2001

In this paper, a multistage parallel interference canceller (MPIC) and a partial multistage parallel interference canceller (PMPIC) are employed as a technique for improving the performance of the asynchronous DS-CDMA systems. The degree of the effect of the timing errors and phase errors on the interference cancellation capability of two types of cancellers is theoretically analyzed and the computer simulation is performed to confirm the analytical results. From the results, the large performance improvement is obtained by employing MPIC and PMPIC with perfect synchronization over the conventional matched filter, and the performance improvement obtained by MPIC and PMPIC is very close to each other as the number of the stage of MPIC and PMPIC increases. When the timing errors and phase errors are considered (in the case of imperfect synchronization), the performance improvement reduces as the performance degradation at the first stage (no cancellation) has a bad effect on the decision statistics at each stage. However MPIC and PMPIC have the strong interference cancellation capability in spite of imperfect synchronization as the number of the stage increases. An interference canceller, which has the strong interference cancellation capability as well as lower complexity for the implementation, is needed for practical systems with timing errors and phase errors because the perfect synchronization is impossible. Therefore, the excellent tradeoff between complexity and performance offered by PMPIC makes it an attractive approach for practical systems.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.2
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• pp.221-227
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• 2002

In this paper, in order to know the effect of the interference, we have analyzed the BER (Bit Error Rate) performance of the MUD(Multi-User Detector) employing HIC(Hybrid Interference Cancellation) scheme for the asynchronous WCDMA system based on 3GPP(3rd Generation Partnership Project) Spec. through the In this paper, in order to know the effect of the interference, we have analyzed the BER (Bit Error Rate) performance of the MUD(Multi-User Detector) employing HIC(Hybrid Interference Cancellation) scheme for the asynchronous WCDMA system based on 3GPP(3rd Generation Partnership Project) Spec. through the computer simulation. we have assumed Rayleigh fading channel. And we have compared its BER performance with SIC's(Successive Interference Cancellation) and with PIC's(Parallel Interference Cancellation), which are the representative schemes in the subtractive interference cancellation. From the results, it is shown that PlC or HIC is effective for high data-rate users and SIC of HIC for low data-rate users to eliminate the interference. Regardless of the data rate, it is reasonable to use the HIC structure for WCDMA system to satisfy all of users' services. The reason is that the SIC scheme in front of HIC can guarantee the performance of low power users to cancel the serious interference caused by the high power users, while PIC in the rear of it can guarantee the performance of high power users to cancel the interference caused by the low power users.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.8
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• pp.2052-2063
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• 1998

Various full-scale radio location systems have been developed since ground-based radio navigation systems appeared during World War II, and more recently global positioning systems (GPS) have been widely used as a representative location system. In addition, radio location systems based on cellular systems are intensively being studied as cellular services become more and more popular. However, these studies have been focused mainly on macrocellular systems of which based stations are mutually synchronized. There has been no study about systems of which based stations are asynchronous. In this paper, we proposed two radio location algorithms in microcellular CDMA systems of which base stations are asychronous. The one is to estimate the position of a personal station at the center of rectangular shaped area which approximates the realistic common area. The other, as a method based on road map, is to first find candidate positions, the centers of roads pseudo-range-distant from the base station which the personal station belongs to and then is to estimate the position by monitoring the pilot signal strengths of neighboring base stations. We compare these two algorithms with three wide-spread algorithms through computer simulations and investigate interference effect on measuring pseudo ranges. The proposed algorithms require no recursive calculations and yield smaller position error than the existing algorithms because of less affection of non-line-of-signt propagation in microcellular environments.