Earticle

무선통신 시스템에서는 운용하는 송신기나 수신기의 이동에 의해서 도플러 주파수 천이가 발생하며, 도플러 주파수 천이나 송수신기 사이에 존재하는 주파수 오프셋을 제거해야 원하는 성능을 얻을 수 있다. FTS(Flight Termination System)는 공공의 안전과발사체의 비정상적인 임무 수행을 막기 위해서 사용되는데 발사체의 경 우에는 지구 탈출을 위해서 초기 속도가 아주 빠르고 그에따라서 도플러 주파수 천이도 아주 크다. 최근 차세대 FTS의 도입을 위한 연구가 활발히 진행 중이며, 새로운 FTS를 도입하기 위해서는 도입하는 시스 템에 대한 도플러주파수의 영향을 검토해야 한다. 본 논문에서는 발사체의 도플러 주파수 천이가 FTS 수신기 의 성능에 미치는 영향을 분석하였으며,디지털 방식의 FTS와 톤 방식의 FTS에 미치는 영향으로 나누어 분석 하였다. 디지털 방식의 FTS인 EFTS(Enhanced FTS)에서는비동기 DPSK(Differential PSK)와 비동기 CPFSK (Continuous Phase FSK)에 미치는 영향을 중점적으로 검토하였고, 200Hz의 도플러 주파수 천이가 채널코딩 을 적용한 비동기 DPSK와 비동기 CPFSK에 미치는 영향을 시뮬레이션 하였다. 시뮬레이션 결과 BER이10⁻⁵ 근 처에서 RS코딩은 약 0.5dB의 Eb/No가 악화되었고, 컨볼루션코딩과 BCH코딩은 성능변화가 거의 없거나 Eb/No가 0.1dB 정도악화되었다. 톤 방식의 FTS에서는 수신기가 직교검파기를 사용하는 경우에 대해서 분석 하였으며, 직교검파인 경우에는 도플러 주파수 천이의 영향을 거의 받지 않는다.

A doppler shift is generated by moving a transmitter or receiver operated in communication systems. The doppler frequencyshift between a transmitter and a receiver or the frequency offset present in transceivers must be removed to get the wantedsystem performance. FTS is used for preventing an accident from operating abnormally and for guaranteeing publicprotection. A launching vehicle's initial velocity is very fast in order to escape the earth and the amount of doppler shiftis large. Recently many studies to adopt the next generation FTS are ongoing. To introduce new FTS, the effects of doppler shifton the performance of the new FTS must be studied. In this paper the doppler effect caused by launching vehicle's velocityaffecting the performance of FTS receiver is investigated into two cases, one is for EFTS as a digital FTS and the otheris for FTS using a tone signal. Noncoherent DPSK and noncoherent CPFSK are considered as the modulation methods ofEFTS. In the cases of the doppler frequency shift of 200Hz present in EFTS using noncoherent DPSK and noncoherentCPFSK are simulated. Simulation results show that Eb/No of 0.5dB deteriorates in the region of near BER of about 10⁻⁵in RS coding. And there is no performance variation in Eb/No or Eb/No is worsened about 0.1dB in the same BER regionfor the case of using convolutional and BCH coding. Quadrature detector used in FTS using tone signals is not influencedby the doppler frequency shift.

최근에 Standard 톤 방식의 FTS(Flight Termination System)는 보안 및 다수의 발사체가 동시에 운영될 때 문제가 있음이 보고되 어, 차세대 FTS의 도입이 검토되고 있다. 본 논문에서는 차세대 FTS로 도입이 검토되고 있는 EFTS(Enhanced FTS)의 변조 방식 및 채널 코드에 따른 BER 성능을 비교하였다. EFTS의 변조 방식으로는 비동기 BFSK, 동기 BPSK, 비동기 DPSK, 동기 CPFSK 그리고 비동기 CPFSK의 성능을 비교 검토하였으며, 채널 코드로는 컨볼류션널, RS 그리고 BCH의 성능을 비교하였다. EFTS의 변조 방식의 성능 시뮬레이션 결과 동기 방식이 비동기 방식에 비해 우수한 성능을 가짐을 확인하였다. 그러나 동기 방식은 발사체 의 환경에서 동기의 획득 및 유지문제 그리고 동기를 위해서 추가적으로 사용되는 부품들의 신뢰성을 고려하면 도입이 어렵다. 비동 기 방식에서는 DPSK, 비동기 CPFSK 그리고 비동기 BFSK 순서로 BER 성능이 좋은 것으로 시뮬레이션되었다. 그러나 DPSK 변조 의 경우 PEP(Peak Enveop Power)가 약 2.6dB(rolloff 0.5인 경우)로 CPFSK의 PEP 1.8dB 보다 크기 때문에 송신기의 구성측면에서 불리하다. 채널 코드에 따른 성능 시뮬레이션 결과를 보면 컨볼루션널 코드가 다소 좋은 성능을 보이지만, 원하는 BER을 갖는 Eb/No 부근에서는 RS의 BER 성능 개선 정도가 더 우수함을 확인하였다.

A report of security problems and simultaneous operation limits of Standard tone currently used for FTS introduces the development of a next generation FTS. In this paper, BER performance by modulations and channel coding methods for EFTS are compared. Simulation results show that coherent modulations have better BER performance than noncoherent modulations. However the environments of a lunching vehicle may cause serious problems in achieving and maintaining synchronization and the increasing complexity of coherent systems also increases reliability problems. Therefore noncoherent systems are suitable for FTS even though BER performace of noncoherent systems is lower than coherent systems. Noncoherent DPSK has better BER performance than noncoherent CPFSK. However the PEP of noncoherent DPSK is 0.8dB higher than noncoherent CPFSK. Therefore a transmitter of noncoherent DPSK has more output power than noncoherent CPFSK. Convoltional code has better BER performance than RS code. However RS code has a tendency of steeply decreasing BER near the wanted Eb/No.

The paper proposes reliable channel for medical uses via Physical Layer. The purpose is to serve medical data transmission from WBAN through the UMTS. This study is focusing on applying coding theory to carry high reliability and robustness, in order to satisfy various QoS requirements of medical data. The aim is to build Medical Network Channel that transmits WBAN medical data through the UMTS. The design of extra channel coding is considered as concatenated techniques. The method applies adaptive outer code with inner UMTS code. The accomplishment of QoS is investigated with numerical results proven under AWGN and Rayleigh fading.

In this paper we propose high rate turbo code (HRTC) that exploits the potential correlation present between the data of the neighboring sensor nodes in a wireless sensor network. The problem of implosion and overlap, faced by the sensor nodes, gives rise to data redundancy in the sensor network. This paper combines source -channel coding wi th data aggregation using HRTC to reduce the redundant information produced amongst the nodes and to make the network more resourceful and reliable. This paper also includes the design of the proposed HRTC that uses deterministic interleaver to ensure good permutations.

본 논문에서는 송신부에서 다중 안테나를 사용할 때, 안테나 선택 과정에서 논리적 정보를 담아 전송하는 시스템이다. 송신부는 보내고자 하는 데이터 스트림 일부분을 안테나 선택 테이블에 적용하여 일부분을 제외한 데이터 스트림을 송 신한다. 수신부는 송신된 데이터 스트림과, 선택된 안테나 테이블에 의해 실제적으로는 송신되지 않은 데이터 스트림을 복구하여 송신부가 보내고자 했던 전체 데이터 스트림을 도출하는 시스템이다. 채널 용량을 최대화하기 위하여 SVD (Singular value decomposition)을 적용 후 송신할 안테나를 선택하였다. 선택하는 송신 안테나 수에 따라 달라지는 채널 용량을 실험하였으며, 안테나 선택에 의한 논리적 전송에 따라 증가하는 시스템 처리량을 확인하였다.

A new decoding algorithm that modifies error searching soft decision method is presented. The proposed algorithm improves the decoding error performance caused by repeated searching. It is shown that the simplicity inherent in the hard decision decoding is still maintained. This paper proposes an error correcting binary channel code which promotes symbol transition. This scheme exploits the error correcting capability of the preparatory code. It is demonstrated that the proposed code combine good symbol transition property with their own error correcting capability.

In this paper, delay-limited transmission of Quasi-stationary sources over block fading channels is considered. Considering distortion outage probability as the performance measure, two source and channel coding schemes with power adaptive transmission are presented. The delay limited transmission of a quasi-stationary source over a block fading channel is from the perspective of source and channel coding design and it utilizes performance scaling laws. Because In a Quasi -stationary sources time utilization takes a major role. For that the first one is optimized for fixed rate transmission, and hence enjoys simplicity of implementation. The second one is a high performance scheme, which also benefits from optimized rate adaptation with respect to source and channel states. In high SNR regime, the performance scaling laws in terms of outage distortion exponent and asymptotic outage distortion gain are derived, where two schemes with fixed transmission power and adaptive or optimized fixed rates are considered as benchmarks for comparisons. Various analytical and numerical results are provided which demonstrate a superior performance for source and channel optimized rate and power adaptive scheme.

A selection method of possible code words in channel coding systems is presented. The proposed method is for channel coding of digital communication systems. Measuring the error correction capability with reunion junction, the proposed method has superior performance and low implementation complexity.

This paper introduces a new paradigm of physical layer security through channel coding for wireless networks. The well known spread spectrum based physical layer security in wireless network is applicable when code division multiple access (CDMA) is used as wireless air link interface. In our proposal, we incorporate the proposed security protocol within channel coding as channel coding is an essential part of all kind of wireless communications. Channel coding has a built-in security in the sense of encoding and decoding algorithm. Decoding of a particular codeword is possible only when the encoding procedure is exactly known. This point is the key of our proposed security protocol. The common parameter that required for both encoder and decoder is generally a generator matrix. We proposed a random selection of generators according to a security key to ensure the secrecy of the networks against unauthorized access. Therefore, the conventional channel coding technique is used as a security controller of the network along with its error correcting purpose.

An improvement of soft decision decoding algorithm using linear block codes is presented. The proposed algorithm is for hard-detected signals of digital communication systems. Based on the error correction, the proposed scheme converts the received hard-decision into soft reliability for the input of the decoder. Simulation results are shown and superior performance is obtained by using the proposed scheme.

A coding and decoding scheme controlling run length is presented. The proposed scheme limits the run length of data 0 in digital communication systems. We present a transformation approach to reduce the implementation complexity. The new adaptive scheme is implemented by combining the tree structure model and the candidate space model.

본 논문은 센서 네트워크에서 데이터의 신뢰도를 높이고, 전력 효율적인 프로토콜을 제안한다. 그러기 위하여 최대비 결합(MRC)과 순환 부호를 적용한 협력통신 프로토콜을 제안한다. 하나의 소스노드와 하나의 중계노드는 각각의 시간 슬롯에 목적지로 동일한 데이터를 전송하고, 목적지 노드는 각각의 신호를 수신함으로써 다이버시티 효과를 획득할 수 있다. 제안한 프로토콜은 순환부호를 사용함으로써 3-비트의 오류정정능력을 가지며, 많이 사용되는 콘볼루션 코드에 비하여 복호 시 낮은 복잡도를 가진다. 본 논문의 모의실험 결과를 통하여 BER이 일 때, 단일 홉 전송의 경우에 비하여 6dB의 전력을 절약 할 수 있다는 것을 증명하였다.

In this paper, our goal is to find a power-effective protocol that improves the accuracy of transmission in sensor networks. Therefore we propose a cooperative communication protocol based on MRC(Maximal Ratio Combining) and cyclic code. In our proposal, one sensor node assists two others to communicate with a clusterhead that can get diversity effect and MRC can improve diversity effect also. The proposed protocol with cyclic code can correct error up to 3-bit and reduce decoding complexity compared with convolutional code. Simulation results reveal proposed protocol can save the network energy up to 6dB over single-hop protocol at BER(Bit Error Rate) of 10-2.

The concatenated codes or the convolutional codes which are often adopted in the communication systems are originally designed to overcome the random independent noise. As such, the performance is severely degraded over the bursty impulsive noise channels. In this paper we compare the bit error rate (BER) performance of the various different channel coding schemes with interleaver over the bursty impulsive noise channels. In particular, we focus on the existence of the bit level and/or the byte level interleavers and show from the extensive simulations that the performance can be different depending on the existence of the interleaver. From our simulations we can see that the concatenated codes with the byte interleaver between the inner and outer codes and the bit interleaver after the inner code gives the best performance among them. For the schemes which include the bit level interleaver, we also observe the interleaving gain versus the interleaver span so that it can be a good guideline to design the communication systems with the concatenated codes.

Many kinds of multi-purpose wireless communication chips exist. However, their transmission power, throughput and error correction schemes are fixed. It is hard to apply them to various wireless applications with various quality-of-service. However, bit error occurs frequently in that transmission speed, which results in corrupted digital image when we use the chip module for image transmission. Unfortunately, this chip module does not have any error correction functionality. Hence, transmission speed should be reduced for reliable wireless data transmission. In this paper, a channel coding scheme is adopted outside of the chip module. Especially, the convolutional code is adopted as an error correction code. When the channel coding is adopted, frame error probability is analyzed considering practical chip setup parameters. By using the channel coding added outside of the chip module, reliable image transmission becomes available. Using multiple chip modules and channel coding together, throughput enhancement with trusted wireless transmission can be implemented.

In this paper the model having D8PSK modulation applied by channel coding of Convolution Turbo Code (CTC) was designed and analyzed to improve the performances of wireless communication system for data link between ground equipment and aircraft. The suggested modem was differential 8PSK modulation system and channel coding of Convolution Turbo Code (CTC) system, and TDMA system was used for transmission. The hardware was embodied for the test and done by using 2 FPGA’s and DSP. The function of FPGA has the one of modulation and demodulation of signal, acquisition and maintaining of TDMA synchronization and generating timing signal. As the test results, it was recognized that the transmission rate can be maintained though the code rate is increased based on 28.8 Kbps and the performance of SNR gets 15dB when BER performance criteria is 10-6. And, it was recognized that the performance of BLER satisfies 10-4 based on BER 10-6. And, it was also recognized that the performance of SNB was improved by 4dB comparing with the case which channel coding was not used from the test results.

In this paper, we proposed a progressive time varying source channel coding system for transmitting image over wireless channels. Transmission of compressed image data over noisy channel is an important problem and has been investigated in a variety of scenarios. the core results obtained by a systematic method of instantaneous rate allocation between the progressive source coder and progressive channel coder .It is developed by closed form of expression for end-to-end distortion , rate allocation respectively in static channels. It is extended the static result to an algorithm for fading channels. It is introduced set DCT (blocks) approach is adapted to perform sub band decomposition followed by SPIHT (Set partitioning in Hierarchical tree)

In this paper, we analyze the performance of transmitter and receiver of W-CDMA system using the channel coding and space time code in downlink over ITU-R realistic channel model. We can improve the data rate and the reliability of communications by a channel code, and we can get a diversity gain by using the space time code over fading channels. We also apply the RAKE receiver to improve a performance in multi-path fading channel environment.

In this paper, we analyze the performance of transmitter and receiver of W-CDMA system using the channel coding and space time code in downlink over ITU-R realistic channel model. We can improve the reliability of communications and increase the data rate by channel coding, and we can get a diversity gain by using the space time code over fading channels. We also apply the RAKE receiver to improve tile performance in multi-Path fading channel environment.

Wireless communication chipsets have fixed transmission rate and communication distance. Although there are many kinds of chipsets with throughput and distance purpose, they cannot support various types of wireless applications. This paper provides theoretic research results in order to support various wireless applications requiring different throughput, delayed quality-of-service (QoS), and different communication distances by using a wireless communication chipset with fixed rate and transmission power. As a performance metric, the probability for a data frame that successfully receives at a desired receiver is adopted. Based on this probability, the average number of transmission in order to make a successful frame transmission is derived. Equations are utilized to analyze the performance of a single-hop with channel coding and a dual-hop without error correction matter transmission system. Our results revealed that single-hop transmission assisted by channel coding could extend its communication distance. However, communication range extending effect of the single-hop system was limited. Accordingly, dual-hop transmission is needed to overcome the communication distance limit of a chipset.