• Journal of Broadcast Engineering
• /
• v.16 no.6
• /
• pp.1026-1035
• /
• 2011

This paper presents generalization and application for the conventional SISO decoding algorithm of Block Turbo Codes. R. M. Pyndiah suggested an iterative SISO decoding algorithm for Product Codes, two-dimensionally combined linear block codes, on AWGN channel. It wascalled Block Turbo Codes. Based on decision of Chase algorithm which is SIHO decoding method, SISO decoder for BTC computes soft decision information and transfers the information to next decoder for iterative decoding. Block Turbo Codes show Shannon limit approaching performance with a little iteration at high code rate on AWGN channel. In this paper we generalize the conventional decoding algorithm of Block Turbo Codes, under BPSK modulation and AWGN channel transmission assumption, to the LLR value based algorithm and suggest an application example such as concatenated structure of LDPC codes and Block Turbo Codes.

• Journal of Satellite, Information and Communications
• /
• v.6 no.1
• /
• pp.75-79
• /
• 2011

Wireless devices can communicate between each other without existing infrastructure in mobile Ad-hod network. Ad hoc networks can be used under difficult conditions, where it is difficult to construct infrastructures, such as shadowing areas, disaster areas, war area, and so on. In order to support to considerable and various wireless services, more spectrum resources are needed. However, efficient utilization of the frequency resource is difficult because of spectrum scarcity and the conventional frequency regulation. Ad-hoc networks employing cognitive radio (CR) system that guarantee high spectrum utilization provide effective way to increase the network capacity. In this paper, we simulate and compare the performance of conventional single and cooperative spectrum sensing with CR system using ad-hoc networks in additive white Gaussian noise (AWGN) and Rayleigh channel model. And we demonstrate performance improvement by analyzing the system performance.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.5A
• /
• pp.484-492
• /
• 2006

A multi-code biorthogonal code keying(MBCK) system consists of multiple waveform coding block, and the sum of output codewords is transmitted. Drawback of MBCK is that it requires amplifier with high linearity because its output symbol is multi-level. MBCK with constant amplitude preceding blcok(CA-MBCK) has been proposed, which guarantees sum of orthogonal codes to have constant amplitude. Redundant bits of CA-MBCK for constant amplitude coding are not only used to make constant amplitude signal but also used to improve the bit error rate(BER) performance at receiver. In this paper, we proposed a transmission scheme which combine CA-MBCK with $Q^{2}PSK$ to improve bandwidth efficiency of CA-MBCK. The BER performance of the scheme is same that of CA-MBCK in additive white gaussian noise(AWGN). And we showed that BER performance of the proposed system can be improved using redundant bits of constant amplitude preceding.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.19 no.6
• /
• pp.1004-1015
• /
• 1994

Modulation type classifier based on statistical moments has been successfully employed to classify PSK signals. Previously, the classifier developed utilizes the statistical moment of samples of the received signal phase, which may be difficult to extract from received signal. In this paper we propose a new moments-based classifier to classify PSK signals by using the moments of the demodulated signal for PSK. THe demodulated signal can be easily extracted from the conventional demodulation of PSK. The evaluation of the performance of the proposed classifier for PSK signals has been investigated in additive white Gaussian noise environment using the exact distribution of the demodulated signal. The performances of classifier in terms of probability of misclassification were evaluated. We found that the coherent system classifier gave 4dB improvement for BPSK and 3dB for QPSK over noncoherent system classifier, when the probability of misclassification is 10 and m equals to 4.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.13 no.2
• /
• pp.397-406
• /
• 2009

A Wireless Access for Vehicular Environment (WAVE) system based on Orthogonal frequency Division Multiplexing (OFDM) is made for vehicle to vehicle wireless communications. The physical layer standard of the WAVE system is very similar to that of the IEEE802.1la wireless local area network (WLAN). Therefore, the performance of the WAVE system is degraded by continual timing delay in the WAVE multipath fading channels after starting initial timing synchronization. In this paper, the tracking algorithm that synchronizes symbol timing is proposed to continually compensate additional timing delay. Computer simulation of the proposed algorithm is performed in the worst communication environments that apply to maximum timing delay. Computer simulation shows that the proposed algorithm can improve the system performance in various channel conditions.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.18 no.1
• /
• pp.1-9
• /
• 1993

In this paper, a new digital mobile channel has been modeled. And concatenated code systems have been proposed to transmit information reliably in the newly modeled mobile fading channels. The BCH code has been used as the outer code and the convolutional code as the inner code. We have modeled the channels which have multipath fading phenomena and additive white Gaussian noise. As a result, the characteristics of the channels are identical to that of the mobile fading channel. To find the best code system, we have tested (7, 4), (63, 45), (63, 57) and (31.26) BCH codes as an outer code. Results show that the concatenated code with (7, 4) outer code gives the best performance. And if we use the soft decision, we can improve about 2 -6 dB in the SNR

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.43 no.8 s.350
• /
• pp.59-68
• /
• 2006

The study on the uniform error property of codes has been restricted to additive white Gaussian noise (AWGN) channel, which is generally referred to as geometrical uniformity. In this paper, we extend the uniform error property to space-time codes in multiple-input multiple-output (MIMO) channel by directly treating the probability density functions fully describing the transmission channel and the receiver. Moreover, we provide the code construction procedure for the geometrically uniform space-time trellis codes in fast MIMO channels, which consider the distance spectrum. Due to the uniform error property, the complexity of code search is extensively reduced. Such reduction makes it possible to obtain the optimal space-time trellis codes with high order states. Simulation results show that new codes offer a better performance in fast MIMO channels than other known codes.

• 전자공학회논문지 IE
• /
• v.43 no.2
• /
• pp.80-86
• /
• 2006

The wireless communication based on LDPC and adaptive spatial-subcarrier coded modulation using MQAM for orthogonal frequency division multiplexing (OFDM) wireless transmission by using instantaneous channel state information and employing multiple antennas at both the transmitter and the receiver. Adaptive coded modulation is a promising idea for bandwidth-efficient transmission on time-varying, narrowband wireless channels. On power limited Additive White Gaussian Noise (AWGN) channels, low density parity check (LDPC) codes are a class of error control codes which have demonstrated impressive error correcting qualities, under some conditions performing even better than turbo codes. The paper demonstrates OFDM with LDPC and adaptive modulation applied to Multiple-Input Multiple-Output (MIMO) system. An optimization algorithm to obtain a bit and power allocation for each subcarrier assuming instantaneous channel knowledge is used. The experimental results are shown the potential of our proposed system.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.11 no.6
• /
• pp.295-302
• /
• 2011

In this paper we consider technological requirements to broadcast digital television signals using single frequency networks(SFN) in the Advanced Television Systems Committee(ATSC) transmission systems and propose Interference Cancellation Digital On Channel Regenerative Repeater(IC-DOCR) thar overcomes the limitation of EDOCR(Equalization Digital On Channel Repeater) proposed by ETRI. The proposed IC-DOCR maintains the benefits of EDOCR that have good output signal quality removing multi-path, additive white Gaussian noise(AWGN). In additional, since the Interference Cancellation algorithm using the 8-VSB symbol demodulation of received signal removes the Interference of feedback signal, IC-DOCR improve the weakness of EDOCR that have low isolation between receive and transmit antenna so that can overcome the limitation of output signal power. we did analysis and verification of the proposed system performance using computational simulation.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.12 no.1
• /
• pp.178-203
• /
• 2018

In this paper, authors have been evaluated the Frame Error Rate (FER) performance of IEEE 802.11 a/g/p standard 5 GHz frequency band WLAN over Rayleigh and Rician distributed fading channels in presence of Additive White Gaussian Noise (AWGN). Orthogonal Frequency Division Multiplexing (OFDM) based transceiver is implemented by using real-time signal processing frameworks (IEEE 802.11 Blocks) in GNU Radio Companion (GRC) and Ettus USRP N200 is used to process the symbol over the wireless radio channel. The FER is calculated for each sub-carrier conventional modulation schemes used by OFDM such as BPSK, QPSK, 16, 64-QAM with different punctuated coding rates. More precise SNR is computed by modifying the SNR calculation process of YANS and NIST error rate model to estimate more accurate FER. Here, real-time signal constellations, OFDM signal spectrums etc. are also observed to find the effect of multipath propagation of signals through flat and frequency selective fading channels. To reduce the error rate due to the multipath fading effect and Doppler shifting, channel estimation (CE) and equalization techniques such as Least Square (LS) and training based adaptive Least Mean Square (LMS) algorithm are applied in the receiver. The simulation work is practically verified at GRC by turning into a pair of Software Define Radio (SDR) as a simultaneous transceiver.