• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.10 no.3
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• pp.79-84
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• 2011

In this paper, we analyzed performance of vehicle detection for ITS (Intelligent Transport System) applications. We simulated the vehicle detection at Hi-Pass System is based on DSRC (Dedicated Short Range Communication). DSRC is a wireless network using ITS, including GPS (Global Positioning System) satellites in conjunction with the national transportation system. The system performance is evaluated in terms of bit error probability. In the simulation, the vehicle speed is set at 60 km/h and carrier frequency is 5.8 GHz. Wireless channel is modeled as the Rician fading channel. In the transmitter, the ASK (amplitude shift keying) modulation scheme is applied. From simulation results, we confirmed that performance of applied Alamouti scheme is better than other systems.

• Journal of electromagnetic engineering and science
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• v.10 no.2
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• pp.56-60
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• 2010

This paper proposes a new cooperative protocol in which Alamouti's scheme is applied to exploit the advantages of both coded cooperation and Alamouti's scheme. It not only has better than direct transmission but also coded cooperation at appropriate cooperation levels. Simulation results show that the proposed protocol can save approximately 6~7 dB of transmit power to achieve the target BER(Bit Error Rate) compared with coded cooperation. Furthermore, the performance of the proposed protocol does not significantly depend on the qualities of inter-user channels.

• ETRI Journal
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• v.26 no.5
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• pp.443-451
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• 2004

Since the publication of Alamouti's famous space-time block code, various quasi-orthogonal space-time block codes (QSTBC) for multi-input multi-output (MIMO) fading channels for more than two transmit antennas have been proposed. It has been shown that these codes cannot achieve full diversity at full rate. In this paper, we present a simple feedback scheme for rich scattering (flat Rayleigh fading) MIMO channels that improves the coding gain and diversity of a QSTBC for 2$^n$ (n=3, 4, ${\cdots}$) transmit antennas. The relevant channel state information is sent back from the receiver to the transmitter quantized to one or two bits per code block. In this way, signal transmission with an improved coding gain and diversity near to the maximum diversity order is achieved. Such high diversity can be exploited with either a maximum-likelihood receiver or low-complexity zero-forcing receiver.

• Journal of Broadcast Engineering
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• v.19 no.2
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• pp.184-194
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• 2014

The CBS methodology has been utilized in order to make a rapid broadcast of emergency alert based on cellular systems. We present a synchronous cooperative communication method for the CBS. Especially, we suggest a synchronization scheme and a data recovery approach for high-rate cooperative communications. For the high-rate transfer of emergency alert, the cyclic prefix is added to the preamble for the synchronization. For the data recovery, the Alamouti technique is utilized on frequency domain, which is similar to SC-FDE. The simulation results confirm that our proposed scheme is very suitable for the CBS.

• Journal of Navigation and Port Research
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• v.37 no.3
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• pp.269-273
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• 2013

Underwater acoustic channels are generally recognized as one of the most difficult communication media because of the multipath propagation, dispersion, and so on. MIMO (Multiple-input multiple-output) techniques have been actively pursued in underwater acoustic communications recently to increase the data rate over the bandwidth-limited channels. The transmit diversity techniques can be applied in this case, and one of them is Alamouti's scheme. In this paper the performances of the transmit diversity technique are evaluated via experiment. Two transmitters and two receivers were used in experiment, and the experiment was performed in indoor water tank. The error rate 5~8% was confirmed in experimental results, and these are the improved values than the error rate 14.8% for SISO(Single-input single-output) channel under same data rate condition.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.60 no.4
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• pp.200-205
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• 2011

In multipath fading channel, diversity is essential to mitigate the impairments. In this paper, we have proposed the angle diversity scheme called ATTD(Angle Time Transmit Diversity) instead of Alamouti's STTD(Space Time Transmit Diversity) and have analyzed the performance of the proposed scheme when signal powers caused by the transmission to different angles are different. Based on it, we have measured the wireless vector-channel in the urban area, which has lots of high-story buildings, using the data collected from the 8 by 4 smart array antenna system that we made. According to the measured data, the received signals from different angles have different signal powers. Our performance analysis results show that the proposed scheme has better performance than the space diversity scheme when the received path signal power is at least -7dB compare to the strongest path signal power.

• Journal of Communications and Networks
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• v.13 no.5
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• pp.421-427
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• 2011

Problems encountered in IEEE 802.11 medium access control (MAC) design are interferences from neighboring or hidden nodes and collision from simultaneous transmissions within the same contention floors. This paper presents the selective decoding schemes in MAC protocol for multiple input multiple output ad-hoc networks. It is able to mitigate interferences by using a developed minimum mean-squared error technique. This interference mitigation combined with the maximum likelihood decoding schemes for the Alamouti coding enables the receiver to decode and differentiate the desired data streams from co-channel data streams. As a result, it allows a pair of simultaneous transmissions to the same or different nodes which yields the network utilization increase. Moreover, the presented three decoding schemes and time line operations are optimally selected corresponding to the transmission demand of neighboring nodes to avoid collision. The selection is determined by the number of request to send (RTS) packets and the type of clear to send packets. Both theoretical channel capacity and simulation results show that the proposed selective decoding scheme MAC protocol outperforms the mitigation interference using multiple antennas and the parallel RTS processing protocols for the cases of (1) single data stream and (2) two independent data streams which are simultaneously transmitted by two independent transmitters.

• Journal of Communications and Networks
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• v.5 no.2
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• pp.167-173
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• 2003

We treat the problem of channel estimation and interference cancellation in multiuser ultra-wide-band (UWB) communication systems over multipath fading channels. The UWB system under consideration employs a random time-hopping impulse radio format. We develop a channel estimation method based on linear weighted algorithm. An iterative channel estimation and interference cancellation scheme is proposed to successively improve the receiver performance. We also consider systems employing multiple transmit and/or receive antennas. For systems with multiple receive antennas, we develop a diversity receiver for the wellseparated antennas. For systems with multiple transmit antennas, we propose to make use of Alamouti’s space-time transmission scheme, and develop the corresponding channel estimation and interference cancellation receiver techniques. Simulation results are provided to demonstrate the performance of various UWB receiver techniques developed in this paper.

• 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.

• Journal of Communications and Networks
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• v.7 no.2
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• pp.157-170
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• 2005

The combination of multiple antennas and multi-carrier code division multiple-access (MC-CDMA) is a strong candidate for the downlink of the next generation mobile communications. The study of such systems in scenarios that model real-life trans-missions is an additional step towards an optimized achievement. We consider a realistic MIMO channel with two or four transmit antennas and up to two receive antennas, and channel state information (CSI) mismatches. Depending on the mobile terminal (MT) class, its number of antennas or complexity allowed, different data-rates are proposed with turbo-coding and asymptotic spectral efficiencies from 1 to 4.5 bit/s/Hz, using three algorithms developed within the European IST-MATRICE project. These algorithms can be classified according to the degree of CSI at base-station (BS): i) Transmit space-frequency prefiltering based on constrained zero-forcing algorithm with complete CSI at BS; ii) transmit beamforming based on spatial correlation matrix estimation from partial CSI at BS; iii) orthogonal space-time block coding based on Alamouti scheme without CSI at BS. All presented schemes require a reasonable complexity at MT, and are compatible with a single-antenna receiver. A choice between these algorithms is proposed in order to significantly improve the performance of MC-CDMA and to cover the different environments considered for the next generation cellular systems. For beyond-3G, we propose prefiltering for indoor and pedestrian microcell environments, beamforming for suburban macrocells including high-speed train, and space-time coding for urban conditions with moderate to high speeds.