• Journal of the Korean Institute of Telematics and Electronics C
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• v.34C no.2
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• pp.1-11
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• 1997

We developed a base station modulator ASIC for CDMA digital cellular system. In CDMA digital cellular system, the modulation is performed by convolutional encoding and QPSK with spread spectrum. The function blocks of base station modulator are CRC, convolutional encoder, interleaver pseudo-moise scrambler, power control bit puncturing, walsh cover, QPSK, gain controller, combiner and multiplexer. Each function block was designed by the logic synthesis of VHDL codes. The VHDL code was described at register transfer level and the size of code is about 8,000 lines. The circuit simulation and logic simulation were performed by COMPASS tools. The chip (ES-C2212B CMB) contains 25,205 gates and 3 Kbit SRAM, and its chip size is 5.25 mm * 5,45 mm in 0.8 mm CMOS cell-based design technology. It is packaged in 68 pin PLCC and the power dissipation at 10MHz is 300 mW at 5V. The ASIC has been fully tested and successfully working on the CDMA base station system.

• Proceedings of the IEEK Conference
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• 2002.07a
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• pp.329-332
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• 2002

In this paper a common design method fur RF receivers of different CDMA standards is introduced. The method adopted a new equation, receiver noise equation, for the analysis of each standard. The test conditions for RF receivers in four different CDMA standards, CDMA cellular, PCS, WCDMA, and cdma2000 are analyzed based on the receiver noise equation. With the result of the analysis, the specifications fer RF receivers of different CDMA standards are derived.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.43 no.1 s.307
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• pp.7-12
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• 2006

In this paper we proposed a real-time remote monitoring system for interoperability between local area and wide area for wireless data communication. In local area, we used a miniaturized low-power wireless module and in wide area used CDMA Cellular System's Packet Data Service. The measurement results can be spread via Internet access in real-time

• Proceedings of the IEEK Conference
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• 2001.06a
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• pp.213-216
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• 2001

In this paper, the performance of an OFDM/CDMA system with turbo coding is analyzed and simulated in a multipath fading channel. Bit error probability is derived fDr a Rayleigh fading channel. In an OFDM/CDMA system, an OFDM and a CDMA techniques are combined to exploit the advantages of both techniques. For decoding of turbo code, MAP decoding algorithm is employed. From the simulation results. it is demonstrated that turbo coding offers considerable coding gain with reasonable encoding/decoding complexity. Also, it is shown that the BER performance is substantially improved by increasing the interleaver length for a fixed code rate and the increasing number of iterations used in the decoding process. The results in the paper can be applied to the design of OFDM-based CDMA system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.11
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• pp.1349-1355
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• 2016

It should guarantee high reliability and ultra low latency communication. Additionally, it should support connection between massive devices. As one of estimated scenarios for 5G mobile communication, mobile devices and sensors using low data rate wireless communication will increase. For communication of these devices, single-carrier system can be considered. In order to satisfy these requirements, in this paper, we propose CDMA (Code Division Multiple Access) system using complex spreading and Multi-level BPSK(Binary Phase Shift Keying). The proposed system spread transmit symbol by using chip code consisted of real and imaginary number. As simulation results, we can confirm that although the proposed system has 3dB lower BER (Bit Error Rate) performance than conventional CDMA system, the proposed system can support 2 times more users in comparison with conventional CDMA system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.3B
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• pp.153-160
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• 2007

Placing antennas of low power base stations below surrounding buildings, as in urban microcells, makes propagation characteristics strongly dependent on the building environment. As a result, propagation in these urban microcells is non-isotropic, so that the assumption of circular cells used in planning of conventional cellular sys toms is no longer valid. Assuming circular cells leads to a more conservative system design, implying more base stations. This work investigates the effect of cell shape, due to non-isotropic propagation, on the out-of-cell interference and Erlang capacity of CDMA system. Propagation is described by measurement derived models for low antennas in a rectangular urban street grid. The analysis is done for soft handoff protocols.

• Proceedings of the IEEK Conference
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• 2000.07a
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• pp.509-512
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• 2000

In this paper, the RBF-based multiuser detector (MUD) is proposed for a multirate DS/CDMA system. The performance of RBF-based MUD is compared with that of many suboptimal multiuser detectors in terms of bit error probability. From the simulation results, it is confirmed that the RBF-based multiuser detector outperforms decorrelating detector, and achieves near-optimum performance in several situations. The results in this paper can be applied to design of MUD fur a multirate DS/CDMA system.

• Journal of Advanced Navigation Technology
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• v.6 no.4
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• pp.273-278
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• 2002

In this paper, we provide the Interference Canceller Systems(ICS) in the wireless environments in the presence of co-existing ETACS and CDMA digital cellular systems to effectively cancel the interference than the established canceller systems. We proved the enhanced cancelling performances more than 29 dB cancellation characteristics between co-existing ETACS and CDMA digital cellular systems and the stabilized system characteristics in the rapidly changing wireless circumstances.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.10
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• pp.158-163
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• 2006

In this paper, we considered the received signal of the wideband CDMA systems using turbo code in the multipath channel environments, and analyze the performance of the system. This study is to analyze the performance for the variable system bandwidth according to the number of branches of rake receiver by passing the received signal through a rake receiver with a turbo code in Rayleigh fading channel environments. For the design of receiver in wideband CDMA systems, we presented the efficient parameters for the number of iterative decoding and the number of branches of rake receiver.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.4 no.1 s.6
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• pp.73-79
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• 2005

In this paper, a circuit for detecting a fine oscillation in an integrated PCS and W-CDMA receiver is presented. The advantages for this design are small size and flexible compatibility for system operation compared with the conventional method. The fine oscillation level can be detected by dB unit through selecting the receiver mode as PCS of 1.8 GHz range or W CDMA of 1.9 GHz range by a RF switch and monitoring the corresponding frequency band. Also, the circuit is designed to be flexible for other communication systems with the consideration of the required dynamic range of 75 dB.