• ETRI Journal
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• v.36 no.2
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• pp.206-213
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• 2014

This paper presents a novel 90 GHz band 16-quadrature amplitude modulation (16-QAM) orthogonal frequency-division multiplexing (OFDM) communication system. The system can deliver 6 Gbps through six channels with a bandwidth of 3 GHz. Each channel occupies 500 MHz and delivers 1 Gbps using 16-QAM OFDM. To implement the system, a low-noise amplifier and an RF up/down conversion fourth-harmonically pumped mixer are implemented using a $0.1-{\mu}m$ gallium arsenide pseudomorphic high-electron-mobility transistor process. A polarization-division duplex architecture is used for full-duplex communication. In a digital modem, OFDM with 256-point fast Fourier transform and (255, 239) Reed-Solomon forward error correction codecs are used. The modem can compensate for a carrier-frequency offset of up to 50 ppm and a symbol rate offset of up to 1 ppm. Experiment results show that the system can achieve a bit error rate of $10^{-5}$ at a signal-to-noise ratio of about 19.8 dB.

• Journal of the Semiconductor & Display Technology
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• v.9 no.2
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• pp.7-10
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• 2010

In this paper, we design a modem SoC (System on Chip) for low power consumption and high speed wireless communications. Among various schemes of high speed communications, an MB-OFDM (Multi Band-Orthogonal Frequency Division Multiplexing) UWB (Ultra-Wide-Band) chip is designed. The MB-OFDM uses wide-band frequency to provide high speed data rate. Additionally, the system imposes no interference to other services. The 90nm CMOS (Complementary Metal-Oxide Semiconductor) technology is used for the SoC design. Especially, power management mode is implemented to reduce the power consumption.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.12A
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• pp.1174-1182
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• 2005

This paper, we propose a new channel Estimation method for MB-OFDM(Multi-Band OFDM) system that is suggested as one of standards in IEEE 802.15 TG3a for high data rate(110Mbps${\~}$480Mbps) WPAN system. The proposed method uses correlation characteristic of the PS(Packet Synchronization) sequence for timing synchronization. It can reduce the influence of noise compared with the conventional algorithm which based on LS(Least square) algorithm is redundancy without using the CE(Channel Estimation) Sequence for channel Estimation. We simulate both conventional method and proposed method for performance analysis in S-V channel environment which proposed by IEEE 802.15.3a. Simulation results show the proposed algorithm outperforms conventional algorithm about 1${\~}$1.5dB of Eb/NO.

• ETRI Journal
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• v.39 no.4
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• pp.535-545
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• 2017

This paper presents a novel K-band (18 GHz) 16-quadrature amplitude modulation (16-QAM) orthogonal frequency-division multiplexing (OFDM)-based $2{\times}2$ line-of-sight multi-input multi-output communication system. The system can deliver 356 Mbps on a 56 MHz channel. Alignment mismatches, such as amplitude and/or phase mismatches, between the transmitter and receiver antennas were examined through hardware experiments. Hardware experimental results revealed that amplitude mismatch is related to antenna size, antenna beam width, and link distance. The proposed system employs an alignment mismatch compensation method. The open-loop architecture of the proposed compensation method is simple and enables facile construction of communication systems. In a digital modem, 16-QAM OFDM with a 512-point fast Fourier transform and (255, 239) Reed-Solomon forward error correction codecs is used. Experimental results show that a bit error rate of $10^{-5}$ is achieved at a signal-to-noise ratio of approximately 18.0 dB.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.12
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• pp.2140-2145
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• 2008

We design and synthesize a 128-point FFT processor for multi-band OFDM, which can be applied to a UWB transceiver. The structure of a 128-point FFT processor is based on a Radix-2 FFT algorithm and a R2SDF pipeline architecture. The algorithm is efficiently modeled in VHDL and the result is simulated using Modelsim. Finally, they are synthesized on Xilinx Vertex-II FPGA, and an operational frequency of 18.7MHz has been obtained. It is expected that the proposed 128-point FFT processor can be applied to an entire FFT block as one of parallel processed FFTs. In order to obtain the enhanced maximum frequency of operation, we design the FFT module consisting of four 128-point FFT processors for parallel process. As a result, we achieve the performance requirement of computing the FFT module in multi-band OFDM symbol timing in 90nm ASIC process.

• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.67-70
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• 2004

This paper describes and analyzes the performance of MB-OFDM (Multi-Band OFDM) technology that is suggested as one of standards in IEEE 802.15 TG3a for uwb application. Also the performance of newly proposed SFBC MB-OFDM scheme is compared with that of conventional MB-OFDM system in this paper. Simulation results show that SFBC MB-OFDM system outperforms conventional MB-OFDM system about 1.5dB Eb/No at target BER of $10^{-4}$.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.10a
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• pp.959-962
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• 2009

Recently, a multi-core system is studied for single terminal's operations on various service networks for mobile systems. Therefore, it is expected that mobile systems capable of supporting WCDMA, GSM, and WiBro would be developed. Mobile systems for supporting various service networks is able to be implemented on a single chipset via SoC(System on Chip) technology, thus a noble modem design proper for SoC technology is necessary. As those systems shall be operated at different frequency band with only a single terminal, a problem that a nonlinear characteristic according to the system and its frequency band is occurred. In this paper a noble modem design for multi-core systems is proposed and the nonlinear characteristics for those systems is analysed. The proposed modem design is based on OFDM(Orthogonal Frequency Division Multiplexing) and MC-CDMA scheme. And nonlinear characteristic analysis is done by PSD measurement.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.2A
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• pp.121-129
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• 2008

This paper presents the spatial multiplexing MIMO system to increase data rate to double in MB-OFDM UWB system, which is ECMA standards, and compares BER performance of various receiver structures. The complexity and BER performance of various types of spatial multiplexing receivers are compared and analyzed using diagonal and horizontal encoding techniques for $2{\times}2$\;and\;2{\times}3$ antennas systems. Computer simulations exhibit that $2{\times}2$ MML and $2{\times}3$ ZF method show better BER performance than that of SISO system with simple complexity.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.6
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• pp.1-5
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• 2011

We present the Multi-band orthogonal frequency division multiplexing ultra-wideband (MB-OFDM UWB) technology for increasing the transmission reach of wireless speaker systems. The proposed scheme adopts the Reed-Solomon coding for preventing the random error perfectly and shows the SNR gain in low bit error rate (BER) especially. So, we can increase the maximum reach of MB-OFDM UWB technology since the receiver sensitivity is improved. The simulation environment includes most effects of realistic channel environments such as Additive White Gaussian Noise (AWGN), CM1 channel model, Sampling frequency offset (SFO), Carrier frequency offset (CFO) to improve the simulation accuracy. The simulation results show that the proposed scheme can give a maximum 2 dB SNR gain and increase the transmission reach up to 12.6m.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6A
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• pp.547-554
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• 2010

Recently, the multi-band orthogonal frequency division multiplexing(MB-OFDM) system, one of UWB system, can satisfy the requirement and can be applied to various wireless communication services because ultra-wideband(UWB) is a wireless communication technique that supports high data rate with low power. In this paper, the method applying Alamouti's space time block code(STBC) and cyclic delay diversity(CDD) is proposed. The proposed method can be easily applied with arbitrary number of relays and only needs two time slots of quasi stationary assumption. And it is applied to the MB-OFDM system. Second, an optimal relaying scheme based on decode-and-forward(DF) method is proposed which is provides good error performance compared to conventional schemes.