• Journal of IKEEE
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• v.16 no.2
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• pp.138-144
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• 2012

In this paper, a semi-analytical approach is proposed for DSF(Decode and Selective Forward)-Relay MC-CDMA(MultiCarrier-Code Division Multiple Access) systems over multipath Rayleigh fading channels. Considering BER(bit error rate) performance and complexity, the MMSE-C(Minimum Mean squared Error-per subCarrier) is used as the combining method for MC-CDMA systems. At first, the analytical method based on error-events at relay nodes for DSF-Relay schemes is utilized in order to derive the averaged BER. Then, the averaged BER is expressed as the form considering possible all error-events. Also, proposed semi-analytical expressions have been verified by comparing with simulation results. Finally, it is verified that the derived analytical expressions can be a frame work to cover different multipath Rayleigh fading channel conditions and to measure the upper performance for DSF-Relay MC-CDMA systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.2A
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• pp.1-11
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• 2005

S-CDMA is the advanced physical layer modulation techniques of DOCSIS 2.0 specification. S-DMT is another challenging modulation technique for cable modem upstream channel due to the intrinsic robustness for fading and impulse noise. The BER performance of S-DMT and S-CDMA over the mixed channel model of AWGN and impulse noise were evaluated in comparison with TDMA. The mathematical BER derivation and the comparison of those three types of technique were performed based on the ${\varepsilon}-mixture$ non-Gaussian impulse noise model. The results of simulation show good compliance with those of analytic BER derivation. By the results of comparisons, it was verified that the performance of S-CDMA and S-DMT is almost the same, but the performance of S-DMT is far superior to that of TDMA at typical BER range of the practical data communications.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.1A
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• pp.1-8
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• 2007

In this paper, we have derived the Noise-Equation to determine the level of cross-modulation noise that is required for designing multi-band CDMA handset from IS-98 standard. From this Noise-Equation, also we were able to determine each component's specification and forecast the performance(or margin) of designing handset. In conclusion, we have designed and implemented the multi-band CDMA handset of Qualcomm's Zero-IF structure and verified validity of the Noise-Equation. In result, we have got the result of ${\pm}0.5dB$ error between Noise-Equation and actual measurement. Therefore, this paper will give a guideline for design of the Multi-Band CDMA handset.

• The KIPS Transactions:PartC
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• v.13C no.7 s.110
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• pp.873-880
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• 2006

Since various networks are deployed and the most of users request higher mobility, there are many researches about the interworking between widely deployed 3G network and rapidly boarded WLAN. On the other side, WiBro is focused on as a next generation network, because many people expect that WiBro gives satisfaction about the enough mobility and mass data transmission. So the study of the integration between WiBro and cdma2000 will show better effects than the present study of the integration between WLAN and cdma2000. The L2 handoff proposed in this paper takes advantages over the existing L3 handoff scheme because it does not require the L3 procedure for the mobility unlike the L3 handoff. Through extensive computer simulations, the efficiency of the proposed scheme has been validated.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.2
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• pp.265-275
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• 2004

In this paper, an OFDM-CDMA broadband system is considered for a possible candidate of fixed wireless broadband access network applications. With an emphasis on a preamble design for multi-channel separation, we address a channel estimation based on the time-domain windowing and its imperfectness in OFDM-based multiple-antenna transmission systems. By properly designing each preamble for multiple antennas to be orthogonal in the time domain, the channel estimation can be applied to the ETSI HlPERLAN/2 and IEEE-802.11a standards in the case of more than two transmit antennas. Also, an effect of diversity techniques on the performance of OFDM-CDMA based broadband wireless access networks is investigated and the maximum achievable diversity gain for a two-path Rayleigh fading environment is evaluated Simulation results show that the OFDM-CDMA system applying a space-time-frequency diversity with a full-rate full diversity code can give the diversity of D = 4 and D = 8 for both multi-user cases of maximum user and half user capacities, respectively.

• Journal of KIISE:Computing Practices and Letters
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• v.8 no.5
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• pp.590-597
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• 2002

Currently, with the increasing demand for combining cellular phone and PDA, various kinds of PDA-phones are being developed. A typical PDA-phone consists of a CDMA processor and a PDA processor. Generally, a UART serial communication port is used for inter-processor communication. However, the CDMA standard will need more data bandwidth over 2Mbps with the emergence of IMT-2000. The bandwidth requirement is beyond the capability of UART. In this paper, several inter-processor communication mechanisms are analyzed and especially Dual Port Memory and USB were chosen as the candidates for the new communication mechanism. A prototype PDA-phone board has been implemented for experiment. The experimental result shows that Dual Port Memory is better than USB in cost performance.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.9
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• pp.1734-1741
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• 2007

In this paper, the Hybrid SC/MRC-2/4 method in which bit synchronization and phase synchronization were not required was applied to the orthogonal MC DS-CDMA system in which each normalized subcarrier interval and processing gain had the same value, respectively, and the direct sequence spread code of each subcarrier was orthogonal. In the broadband wireless system in which multi-carrier transmission was used, a Doppler frequency shift occurred, which was caused by the difference between the highest subcarrier frequency md the lowest subcarrier frequency. In order to complement phase error caused by the shift, the orthogonal MC DS-CDMA system was analyzed so that the receiving signal could be perfectly synchronized by adjusting the PLL gain suitable for the entire system. As a result of simulations, as the PLL gain was increased, the change in the intervals was close to the case of perfect synchronization however, it became less when the PLL gain reached more than a certain value. Therefore, by selecting a proper PLL gain suitable for the system the orthogonal MC DS-CDMA can be designed in which the Hybrid SC/MRC method is applied.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.6
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• pp.179-185
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• 2010

In ubiquitous society, there have been increasing demands on safety and security issues with infrastructures and services based on wireless technology. In this paper, we first introduce our own developed technology Binary CDMA to meet those demands. Then we present a wireless A/V surveillance system based on the Binary CDMA technology. The implemented wireless A/V surveillance system is composed of wireless terminals, wireless multiple channel processors, and an A/V management server, and the system gives a hint that the Binary CDMA technology can be adopted in practical ubiquitous systems to handle safety and security issues.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.2
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• pp.117-125
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• 2003

In this paper, we propose a new code acquisition architecture having the features of low complexity and high speed for the MC-CDMA system. The newly designed searching finger has function of the searcher as well as the finger. The searching finger tests the PN code Phase as the searcher during the initial acquisition, and as the finger after the initial acquisition. The proposed system has reduced the average acquisition time of the PN codes to $T_{acq}$/19 in the 20MHz MC-CDMA system with 75% reduction of H/W complexity.y.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.39 no.8
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• pp.1-6
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• 2002

In this paper, we considered the CDMA/TDD system suitable for high-speed packet data transmission such as Internet and multimedia services, and a sequential decoding scheme which enables fast decoding and retransmission requirement. In addition, we Proposed an improved FANO algorithm, which adopts the competition path in order to reduce the number of revisit nodes. The conventional FANO algorithm suffered from the drawback of much more revisit nodes. Furthermore, we analyzed the performance of the CDMA/TDD system with the sequential decoding scheme we proposed over multipath channel.