• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.25 no.9A
• /
• pp.1332-1339
• /
• 2000

This paper presents the architecture and design of a high speed asymmetric data transmission baseband MODEM ASIC chip for CATV networks. The implemented MODEM chip supports the physical layer of the DOCSIS(Data Over Cable Service Interface Specification) standard in MCNS(Multimedia Cable Network System) The chip consists of a QPSK/16-QAM transmitter and a 64/256-QAM receiver which contain a symbol timing recovery circuit, a carrier recovery circuit, a blind equalizer using MMA and LMS algorithms. The chip can support data rates of 64Mbps at 256 QAM and 48Mbps at 64-QAM and can provide symbol rates up to 8MBaud. This symbol rate is faster than existing QAM receivers. We have performed logic synthesis using the $0.35\mu\textrm{m}$ standard cell library. The total number of gates is about 290,000 and the implemented chip is being fabricated and will be delivered soon.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.51 no.6
• /
• pp.34-42
• /
• 2014

This paper presents a low-complexity and high-throughput symbol detector for two-spatial-stream multiple-input multiple-output systems based on the modified maximum-likelihood symbol detection algorithm. In the proposed symbol detector, the cost function is calculated incrementally employing a multi-cycle architecture so as to eliminate the complex multiplications for each symbol, and the slicing operations are performed hierarchically according to the range of constellation points by a pipelined architecture. The proposed architecture exhibits low hardware complexity while supporting complicated modulations such as 256 QAM. In addition, various modulations and antenna configurations are supported flexibly by reconfiguring the pipeline for the slicing operation. The proposed symbol detector is implemented with 38.7K logic gates in a $0.11-{\mu}m$ CMOS process and its throughput is 166 Mbps for $2{\times}$3 16-QAM and 80Mbps for $2{\times}3$ 64-QAM where the operating frequency is 478 MHz.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.25 no.1A
• /
• pp.27-33
• /
• 2000

Gardner’s algorithm is one of the useful algorithm for NDD(Non-Decision Directed) symbol synchronization in PAM communications. But the algorithm has a weak point such as pattern noises increasing in multi-level PAM. To insert a pre-filter in the algorithm is able to reduce timing jitter and pattern noise. In this paper, we analyze statistical properties of NDD algorithm to find an optimal parameter of the pre-filter for improving timing jitter and PLL locking. As a simulation result, optimum value of pre-filter parameter, $\beta$, is 0.3 and 0.5 at the roll off factor of the channel, $\alpha$, is 0.5 and 1.0, respectively. Optimum parameters of the pre-filter for clock synchronization of all-digital 256-QAM demodulator is shown in the results.

• 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.35 no.6C
• /
• pp.506-515
• /
• 2010

In this paper, we compare and analyze the spectral efficiency of representative adaptive MIMO algorithms in indoor environments. We first briefly investigate the modulation and demodulation schemes of MIMO algorithms to be compared and then implement adaptive algorithms by using BPSK and square QAM schemes up to 256QAM. We finally compare the spectral efficiency of adaptive MIMO algorithms employing (2$\times$2) or (4$\times$4) antenna array through the computer simulation in indoor environments.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.52 no.4
• /
• pp.3-8
• /
• 2015

In this paper, we propose a blind equalization algorithm based on the error signal linearly combined a constellation-matched error (CME) and a non-constellation-matched error (non-CME). The new error signal was designed to include the non-CME term for reaching initial convergence and the CME term for improving intersymbol interference (ISI) performance of output signals, and it controls the error terms through a combining factor. By controlling the error terms, it generates an appropriate error signal for equalization process and improves convergence speed and ISI cancellation performance compared to those of conventional algorithms. In the simulation for 64-QAM and 256-QAM signals under the multipath channel and additive noise conditions, the proposed method was superior to CMA and CMA+DD concurrent equalization.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.38 no.4
• /
• pp.11-17
• /
• 2001

In this paper, we propose a polarity decision carrier recovery algorithm for high order QAM(Quadrature Amplitude Modulation), which has robust and large frequency acquisition performance in the high order QAM modem. The proposed polarity decision PD(Phase Detector) output and its variance characteristic are mathematically derived and the simulation results are compared with conventional DD(Decision-Directed) method. While the conventional DD algorithm has linear range of $3.5^{\circ}{\sim}3.5^{\circ}$, the proposed polarity decision PD algorithm has linear range as large as $-36^{\circ}{\sim}36^{\circ}$ at ${\gamma}-17.9$. The conventional DD algorithm can only acquire offsets less than ${\pm}10\;KHz$ in the case of the 256 QAM while an analog front-end circuit generally can reduce the carrier-frequency offset down to only ${\pm}100\;KHz$. Thus, in this case additional AFC or phase detection circuit for carrier recovery is required. But by adopting the proposed polarity decision algorithm, we can find the system can acquire up to ${\pm}300\;KHz$at SNR = 30dB without aided circuit.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.7 no.5
• /
• pp.893-898
• /
• 2003

This paper proposes a Truncated Type-II Hybrid ARQ scheme and coding techniques using an adaptive modulation system to achieve high throughput data transmission systems for wireless multimedia communication systems. In this paper, the adaptive modulation system analyzed in Nakagami (m-distribution) fading channel environment. The adaptive modulation system controls the modulation level and symbol rate according to the Nakagami fading parameter(m). When the received Eb/No is high or the Nakagami fading parameter m is high, the propose system selects higher modulation level and higher symbol rate to increase throughput. On the other hand, this system selects lower modulation level and lower symbol rate to prevent throughput performance degradation when the received Eb/No is low. The modulation method have been adopted QPSK(Quadrature Phase Shift Keying), 16QAM(Quadrature Amplitude Modulation), 64QAM, 256QAM. Therefore, adaptive modulation systems with truncated type-II hybrid ARQ scheme is proper for wireless multimedia communication system that require high reliability and delay-limited applications.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.12 no.5
• /
• pp.810-816
• /
• 2001

This paper proposes a Truncated Type-II Hybrid ARQ scheme using an adaptive modulation system to achieve high throughput data transmission systems for mobile communication systems. In this paper, the adaptive modulation system analyzed in Nakagami (m-distribution) fading channel environment. The adaptive modulation system controls the modulation level and symbol rate according to the Nakagami fading parameter(m). When the received $E_bN_0$ is high or the Nakagami fading parameter m is high, the propose system selects higher modulation level and higher symbol rate to increase throughput. On the other hand, this system selects lower modulation level and lower symbol rate to prevent throughput performance degradation when the received $E_bN_0$ is low. The modulation method have been adopted QPSK(Quadrature Phase Shift Keying), 16 QAM(Quadrature Amplitude Modulation), 64 QAM, 256 QAM. Therefore, Adaptive Modulation Systems with Truncated Type-II Hybrid ARQ Scheme is proper for mobile and radio for mobile and radio data communication system that require high reliability and delay-limited applications.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.10A
• /
• pp.1147-1158
• /
• 2004

In this paper we design STBC-OFDM systems by applying several STBC schemes to the OFEM system and show their comparative analysis results obtained through computer simulations under Rayleigh fading environments, considering the effect of channel estimation error. We first consider the space-time coding algorithms of major STBC schemes, together with their demodulation algorithms. We then select the OFDMparameters considering mobile environments and design the STBC-OFDM systems by choosing one of digital modulation schemes such as QPSK, BPSK, 16QAM, 64QAM, and 256QAM according to the transmission rate, and describe the block diagrams of the demodulator and channel estimator. We finally compare and analyze the BER performances of the STBC-OFDM systems according to the transmission rate and the number of receive antennas.