• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.48 no.6
• /
• pp.14-21
• /
• 2011

In this paper, we propose an efficient symbol mapping method based on LLR (log-likelihood ratio) statistic for HARQ employing CoRe (constellation rearrangement) with 64QAM. The signal constellations for 64QAM with limited number of retransmissions are selected by the proposed mapping rule. Then we determine the transmission order of selected constellations. The proposed scheme reduces the performance deviation between transmit symbols so as to improve the system performance. Through simulation results, the proposed and existing CoRe mapping methods are compared with respect to error rate and throughput in MIMO-OFDM system over fading channel and we confirm the applicability of the proposed scheme in practical wireless communications environment.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.12 no.6
• /
• pp.865-870
• /
• 2001

In this paper, we analyse the effect of phase noise from PLL frequency synthesizer on 64 QAM when detecting corrupted signals. To predict the phase noise of an oscillator very accurately, we assume that the oscillator is linearly time-varying when the input impulsive current to the oscillator is small. The performance of the detector which detects the corrupted signal by oscillator phase noise is compared with that when the detector is only affected by AWGN and then analyse how much the phase noise degrades the system performance for 64 QAM.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.19 no.5
• /
• pp.928-938
• /
• 1994

We designed and implemented (3.3) tap Decision Feedback Equalizer using Zero Forcing algorithm for 64 QAM RF MODEM (155Mbps) in SDH STM-1, Before we designed DFE, simulate 11 tap linear equalizer and (3.3) tap DFE. Then we get results that performance of DFE is better than linear equalizer by 5dB in fading. Practically, implemented DFE have good performance equalizing signal in 20dB fading depth.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.9 no.2
• /
• pp.247-252
• /
• 2005

This paper proposed M-ary QAM OFDM system for efficiently transmission in multipath fading environment. And, this system have analyzed reception performance by occurred synchronization error to frequency offset in presence of multipath fading. As a result, it confirmed justification by simulation and BER theory of 64QAM OFDM of SP frame structure for the digital broadcasting.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.28 no.6C
• /
• pp.561-569
• /
• 2003

In this paper, for my linear orthogonal space-time block including the orthogonal space-time codes introduced by Alamouti［1］, Tarokh［14］, and Xia［11］, the exact expression for the pairwise error probability in the slow Rayleigh fading channel is derived in terms of the message symbol distance between two message vectors rather than the codeword symbol distance between two transmitted codeword matrices. Using the one-dimensional component symbol error probability, the exact closed form expressions for the symbol error probability of linear orthogonal space-time codes are derived for QPSK, 16-QAM, 64-QAM, and 256-QAM.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.19 no.11
• /
• pp.2081-2093
• /
• 1994

In this study, we design and implement 64 QAM demodulator which has 155 Mbps, first level of CCITT G707 SDH(Synchronous Digital Hierachy) for STM 1 signal transmission. Carrier recovery which effects the demodulator performance uses decision feedback carrier using 8 bits A/D converter. Also, PSF(Pulse Shaping Filter) is 7 order elliptic filter. Carrier recovery circuit is designed and implemented digital type which use high 3 bits of 8 bits conversion data as data and the order low bits as error data and hybrid type which use VCO and analog integrator. Therefore we obtain stable performance recovery.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.19 no.4
• /
• pp.624-632
• /
• 1994

In this paper, we implement modulator of 155Mbps 64QAM RF MODEM, CCITT G. 707 SDH(Synchronous Digital Hierachy) 1 level, for DMR(DIgital Microwave Radio) STM-1 transmission, PSF(Pulse Shaping Filter) plays an important role to analyze modulator. We use 7 orders elliptic filter instead of Chebychev filter(roll-off facter a=0.5)in this paper. we obtain that roll-off factor, a is 0.33, group delay is less than 10nsec using this filter. Also we get -20dBm output level after passing the PSF, and 0dBm output level after passing the IF amplifier.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.16 no.6 s.97
• /
• pp.586-593
• /
• 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 the Korea institute of electronic communication sciences
• /
• v.17 no.4
• /
• pp.587-594
• /
• 2022

This paper analyzed radio link throughput performance by applying radio link simulation and test equipment because there is limit in train filed test in 420 km/h high speed environment. According to the radio performance analysis, the throughput performance is slightly degraded in QPSK and 16QAM modulation schemes. But throughput performance is highly degraded in 64QAM modulation scheme.

• Journal of Advanced Navigation Technology
• /
• v.16 no.1
• /
• pp.158-162
• /
• 2012

In this paper, we propose a wireless modem, which used OFDM/64QAM method and the ISM band with 2.4GHz radio frequency. In this paper proposed the case of a modem, the main program to process the baseband processor, processing speed, operating voltage, and reliability should be ensured. So we have designed with Ralink's RT2870, witch was used for Wi-Fi solution. The RT2870 provides full support for wireless LAN standard, and supports various modulation formats, 2.4GHz and 5GHz bands, both of which support chip. In this paper, we also output the modulated signal transmitted wirelessly to the 2.4GHz band RF RT2850 chip processing was applied and using 40MHz band 2.422 ~ 2.462GHz wireless bands were designed to occupy. By applying bi-directional transmission between wireless transmitter and receiver, it can be effectively connected with any kinds of wireless LAN with 2.4GHz ISM band. Therefore it could economically be used as peripheral equipments for POS system or personal wireless device based on Android platform.