• Journal of Advanced Navigation Technology
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• v.16 no.3
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• pp.426-432
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• 2012

In this paper, we investigate the signal to noise ratio (SNR) estimation performance of Cross quadrature amplitude modulation (QAM), which is being used for asymmetric digital subscriber line (ADSL), very high bit rate digital subscriber line (VDSL), and digital video broadcasting - cable (DVB-C), and has been found to be useful in adaptive modulation and blind equalization. At first, the symbol error rate (SER) performance of Cross QAM is analyzed in Rayleigh fading channel. Then we suggest error vector magnitude (EVM) based SNR estimation utilizing the selected constellation points having different types of decision region from one another, and verify that SNR estimation performance of each points have different performance pattern through simulation. From the simulation results, it has been found that when suggested selected constellation points are used for SNR estimation in Cross QAM, estimation performance is enhanced in additive white Gaussian noise (AWGN) channel or Ricean fading channel.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.6
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• pp.568-580
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• 1997

In this paper we evaluate the performances of two types of 16-QAM system such as square QAM and star QAM. First we analyze the performances of QAM systems under AWGN(adaptive white Gaussian noise) and afterward analyze the performances under fading environments. The performances of QAM systems in case of using the PSAM(Pilot Symbol Assisted Modulation) are finally evaluated under fading environments. In conclusion, the Square QAM's performance is better than star QAM in AWGN. But the performances of the both QAM systems are very poor under the fading environments. QAM performance using the PSAM system is verified to be improved in that case, and the star QAM's performance is better than square QAM.

• Journal of Digital Contents Society
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• v.6 no.2
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• pp.101-106
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• 2005

In this paper, performance evaluation of mobile access layer for multiple-input multiple-output (MIMO) MultiCarrier(MC)/CDMA 16 QAM system is considered to mitigate multiple access interference and enhance system channel capacity in Rayleigh wireless fading channel. Traditionally, multi-path is viewed as an undesirable feature of wireless communications. Therefore, diversity and adaptive array schemes are proposed to mitigate its effects. Recently, to increase the spectrum efficiency and the link reliability, MIMO schemes is devised to exploit multi-path in a scattering wireless channel. In particular, the channel capacity of MIMO-MC/CDMA 16 QAM system is evaluated according to Eb/No, Mc, p. From the results, in order to improve the channel capacity, the signals at various elements must be uncorrelated. And if the paths are correlated due to inappropriate spacing or mutual coupling effects, the channel capacity of MIMO-MC/CDMA 16 QAM system becomes substantially smaller.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1986.04a
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• pp.34-37
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• 1986

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.6 s.97
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• pp.586-593
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• 2005

It is very important to reduce the PAPR(Peak to Average Power Ratio) in the OFDM(Orthogonal Frequency Division Multiplexing) communication system. We propose an ACE(Active Constellation Extension) method that does not require the side information unlike the conventional PTS and SLM method. This ACE method is to clip the OFDM signal for the PAPR reduction. Then, the basic constellation actively moves into the higher level of M-QAM for the constellation extension due to the clipping. The already existing M-QAM system can be available so that it can be easily realized. So, we can get the target PAPR by the extension of the constellation level. In this paper, we can find the PAPR reduction of 4 dB by the 16-QAM extension, and can achieve the target PAPR by the 64-QAM ACE(Active Constellation Extension).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.3A
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• pp.362-374
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• 2000

In this paper, trellis coded 16 QAM Multi-Carrior CDMA system is proposed, Using the equivalent signal-to-noise plus interference Power ratio (SNIR) of Multi-Carrier CDMA system in the reverse link, capacity and BER performance of trellis coded 16 QAM Multi-Carrier CDMA system are analyzed taking into account the number of multi-carrier, the number of multiple access user, the number of SC/MRC diversity branch, and Rician fading parameter in multiuser interference and Rician fading channel. And the capacity and the BER performance of trellis coded 16 QAM Multi-Carrier CDMA system using selection combining (SC) and maximal ratio cabining (MRC) diversity are numerically compared. Obtained results show that the capacity of proposed system depends on the number of multi-carrier. ti is found that the trellis coded 16 QAM Multi-Carrier CDMA system with SC/MRC antenna diversity scheme is efficient to combat multipath fading and to increase the maximum number of users in high speed data communication. With the results of analysis. MRC diversity technique provides the performance fro high speed data communications. Finally, we present a numerical approach to derive the capacity and the BER performance and to find the maximum number of multiple access user for Multi-Carrier system in multiuser interference and Rician fading channel.

• Journal of Advanced Navigation Technology
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• v.8 no.1
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• pp.1-9
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• 2004

In this paper, we have studied the reliable scheme for transmission of digital watermarking-inserted image data through wireless channel. Multimedia data and watermarking data are degraded because of the high BER (Bit Error Rate) and the effect of fading in wireless channel. We adapt the error correction scheme for mitigating the degradation in watermarking data. We have evaluated the error performance of watermarking data modulated by OFDM/16QAM and sent through Rician fading channel. The simulation results show that when error correcting scheme is used the watermarking data can be detected without severe error even though watermarking-inserted image data is suffered from severe damage.

• Journal of Digital Contents Society
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• v.5 no.2
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• pp.121-127
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• 2004

In this paper, we have analyzed the error performance of OFDM (Orthogonal Frequency Division Multiplexing 16 QAM (Quadrature Amplitude Modulation) Signal in a multipath fading environment modeled as frequency selective Rician fading. We have used a three-path model as frequency selective Rician fading used Rician parameter K. A BCH channel coding is used in order to improve the performance. From the result of this analysis, we have known the improvement of the error performance improvement and the error correcting capability by the BCH channel coding. From the results, the error performance, about $10^{-6},$ required in wireless multimedia communications can not be achieved by using only the BCH channel coding technique so that it should be adopted a new technique together.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.2
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• pp.197-206
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• 1997

The purpose of this paper is to propose an improvement method of BER for coded 16QAM over Rayleigh fading channel. To overcome the BER degradation due to the fading under mobile communication, we apply trellis coded modulation technique which is efficient to get a coding gain without the expansion of bandwidth. Especially, to minimize the burst error which are the main factor of the BER degradation for mobile communication systems, we apply interleaving/deinterleaving method to the studying system. Also we apply asymmetric signal mapping methods to this TCM scheme. From the computer simulation, BER performance of asymmetric case has achieved about 1 dB improvement of about $10^{-4}$, compared to the traditional symmetric case.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.154-158
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• 2003

In this paper, Error rate performance of BCH coded DS-CDMA 16 QAM signal is analyzed using selective combining Diversity reception techniques in the environments of Rician fading. First in the performance of DS-CDMA 16 QAM signal in Rician fading channel, Second using SC diversity recepting techniques, and third using both diversity and BCH coding error rate performance is evaluated. from the results of Numerical analyzed it is found that a synergistic performance improvement is shown due to both diversity reception and coding techniques overcoming mobile wireless data communication channel environments.