• Title/Summary/Keyword: Impulse Bit

Search Result 100, Processing Time 0.023 seconds

Performance Analysis of M-ary Multiple Access UWB System Using Modified Hermite Polynomial Pulses (Modified Hermite Polynomial 펄스들을 사용하는 M진 다중접속 UWB 시스템의 성능 분석)

  • Hwang, Jun-Hyeok;Kim, Suk-Chan;Park, Dong-Chan;Kim, Byoung-Chul
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.33 no.9A
    • /
    • pp.909-916
    • /
    • 2008
  • In this paper, we propose and analyze M-ary pulse order time hopping multiple access ultra wideband (PO-THMA UWB) system using modified Hermite polynomial (MHP). The MHP pulses have a mutually orthogonal property between different ordered pulses and that property makes simultaneous transmission at the same time slot regardless of collision in the THMA-UWB system. Therefore, we derive the cross-correlation furlction of MHP pulses and analyze the BER of the proposed system and show that the BER performance and the transmission capacity are improved dramatically when compared with those of conventional THMA-UWB system.

Performance Analysis of Turbo Equalizer in the Multipath Channel (다중 채널 환경에서 터보 등화기 성능 분석)

  • Jung, Ji Won
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
    • /
    • v.5 no.3
    • /
    • pp.169-173
    • /
    • 2012
  • This paper investigates the performance of Turbo equalization in wireless multipath channels. Turbo equalization mainly consists of a SISO(soft-in soft-out) equalizer and a SISO decoder. Iterative channel estimators can improve the accuracy of channel estimates by soft information fed back from the SISO decoder. Comparing iterative channel estimators with LMS(least mean square) and RLS(recursive least squares) algorithms, which are the most common algorithms to estimate and track a time-varying channel impulse response, the iterative channel estimator with RLS converges more faster than the one with LMS. However, the difference of BER(bit error rate) performances gradually decreases as the number of iterations for Turbo equalization increases.

Healing Effect of 'Creative Writing' on Individual and on Our Age - Focused on the 'Man of Darkness (Vampire)' Symbol - ('창조적 글쓰기'가 개인 및 시대에 미치는 치유적 작용 - '어둠의 남자(Vampire)' 상징을 중심으로 - )

  • Kye-Hee Kim;Ki-Won Kim;Eun-Seun Han
    • Sim-seong Yeon-gu
    • /
    • v.28 no.1
    • /
    • pp.1-49
    • /
    • 2013
  • This article started with 'encounter'. Both authors met around the middle of February and discussed the subject for the inhospital conference presentation scheduled at the break of June. Having conversation like "Movies similar to fairytales heard from childhood are standing out conspicuously among commercial films which are attracting audiences and receiving fervent response these days. This phenomenon is marvelous and mysterious." together, and sharing this and that, the conversation turned naturally to 'Bram Stoker's Dracula', 'Series of Twilight', and 'Warm Bodies', both authors found out the fact that we saw these movies in common with propound impression. Feeling our hearts beating high, bit of fear and hesitation followed simultaneously at the moment when both of us encountered the idea to choose subject of conference presentation related to this and expressed one in words. While preparing for the conference, presenting to others, and having discussion with the audience, our hearts have been filled with Presentation was finished after active discussion beyond fixed hour and it also brought audience (among those present) to show strong emotional response both positively and negatively. At first, we just had a thought to put aside the content of presentation, but we felt lack of something else, lingering in our minds. We finally decided to accomplish our work into an article leading to submission, based on the advice and recommendation from one of the audience. This article is a small 'creative writing' born by sharing both authors' passion and enthusiasm. In the first part of this article, we have introduced the dream of 31-year-old woman's which led to the 'creative writing' and spotlighted her personal life, before and after the dream. In the second part, we have examined the consequence (way of realization) and meaning of creative impulse shown from or experienced from personal unconsciousness (dream, fantasy) together. Creative impulse shown from the individual appeared to bring creative transformation of individual personality through the process of 'introversion'. Otherwise it also appeared to be delivered as a masterpiece through 'creative writing' or from the process of 'extroversion'. Sometimes both consequences happened at once. We tried to examine and interpret the dream of 31-year-old woman's, which was introduced in the first part of this article, that is to say, the dream of 'Stephenie Meyer's, the author of the 'love between vampire boy and ordinary human girl' themed novel 'Twilight Series', in a psychoanalytic perspective. In the third part, highlighting individual dreams and three different movies 'Bram Stoker's Dracula', 'Twilight Series', and 'Warm Bodies', we found the transformation of symbol 'Man of Darkness, vampire' seen in each individual dreams and in some specific popular arts, such as novels and movies, receiving fervent response from people. We also found love between this symbol and humane woman, bearing fruit together with very impressive change shown in the attitude of 'Man of Darkness' (vampire)'s conscious ego and mutual relationship pattern. We contemplated this phenomenon, the reason why these events happen, and what kind of association presents among these events, individual, and this era and discussed the effects on individuals and this era, at present. 'Creative impulse', originated in the deep structure of human mind is realized as a 'transformation of individual personality' or masterpiece through artistic creation. If it has a chance to make a match with this era, shared by a lot of contemporary people, it also appears to bring positive effect as healing and salvation to each individual or to each era. From this article, we mainly highlighted positive and healing aspects of individual 'creative impulse'. We hope to deal with the negative consequences and their reason coming from 'creative impulse', if the occasion arises, in the future with a new article.

The Design of Optimal Filters in Vector-Quantized Subband Codecs (벡터양자화된 부대역 코덱에서 최적필터의 구현)

  • 지인호
    • The Journal of the Acoustical Society of Korea
    • /
    • v.19 no.1
    • /
    • pp.97-102
    • /
    • 2000
  • Subband coding is to divide the signal frequency band into a set of uncorrelated frequency bands by filtering and then to encode each of these subbands using a bit allocation rationale matched to the signal energy in that subband. The actual coding of the subband signal can be done using waveform encoding techniques such as PCM, DPCM and vector quantizer(VQ) in order to obtain higher data compression. Most researchers have focused on the error in the quantizer, but not on the overall reconstruction error and its dependence on the filter bank. This paper provides a thorough analysis of subband codecs and further development of optimum filter bank design using vector quantizer. We compute the mean squared reconstruction error(MSE) which depends on N the number of entries in each code book, k the length of each code word, and on the filter bank coefficients. We form this MSE measure in terms of the equivalent quantization model and find the optimum FIR filter coefficients for each channel in the M-band structure for a given bit rate, given filter length, and given input signal correlation model. Specific design examples are worked out for 4-tap filter in 2-band paraunitary filter bank structure. These optimum paraunitary filter coefficients are obtained by using Monte Carlo simulation. We expect that the results of this work could be contributed to study on the optimum design of subband codecs using vector quantizer.

  • PDF

Decoding Method of Repetition Pulses Using Time-Hopping Sequence for UWB-IR in Multi User Environments (다중 사용자 환경에서 무선광대역 시스템의 시간도약 순열을 이용한 반복 부호의 복호화 기법)

  • Min, Seungwook
    • Journal of the Korea Academia-Industrial cooperation Society
    • /
    • v.14 no.10
    • /
    • pp.5162-5168
    • /
    • 2013
  • Hopping sequences of Time Hopped Ultra Wideband Impulse Radio (TH-UWB-IR) system are to mitigate multipath fading and to provide the multiple access chances for multi users. For the reliable communications, the same pulses are repeatedly transmitted for a bit duration based on hopping sequences. The proposed decoding scheme utilizes the intervals of inter-codes in a frame where the short interval between two pulses leads to the large interference by the multipath fading. For a single user case, the proposed method obtains 0.5dB gain over the conventional method at BER=$10^{-3}$. Decoding performance of repeated pulses can be increased using the property of the hopping sequences of multi users.

Selective-Weighted Energy Detector(S-WED) and Synchronization algorithm for IR-UWB systems (IR-UWB 시스템을 위한 선택적 가중치 결합 에너지 검출기(S-WED)와 동기 알고리즘)

  • Ji, Sinae;Kim, Jaeseok
    • Journal of the Institute of Electronics and Information Engineers
    • /
    • v.50 no.7
    • /
    • pp.3-9
    • /
    • 2013
  • This paper proposes a selective-weighted energy detection (S-WED) and a synchronization algorithm appropriate for it in IR-UWB system. Energy detectors that are practical in terms of implementation are employed widely for noncoherent reception in IR-UWB systems. However, they show low performance due to using the energy samples captured at symbol rate. For this reason, weighted energy detectors are developed to improve the performance of EDs. Hence, for WED, not only synchronization but also the weight coefficients are needed to be obtained prior to data detection. Meanwhile, the optimal weighting coefficients of WEDs are known to be energy values. Therefore, synchronization and the weighting coefficients can be obtained simultaneously. This paper proposes an S-WED and a simple synchronization algorithm for it in which sub-intervals having energies under a certain level are excluded in energy accumulation resulting in a simpler WED with a bit performance increase in low SNR region. The proposed algorithm is verified through simulations using the preamble symbol and channel models defined in the IEEE 802.15.4a.

An Image Compression Algorithm Using the WDCT (Warped Discrete Cosine Transform) (WDCT(Warped Discrete Cosine Transform)를 이용한 영상 압축 알고리듬)

    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.24 no.12B
    • /
    • pp.2407-2414
    • /
    • 1999
  • This paper introduces the concept of warped discrete cosine transform (WDCT) and an image compression algorithm based on the WDCT. The proposed WDCT is a cascade connection of a conventional DCT and all-pass filters whose parameters can be adjusted to provide frequency warping. In the proposed image compression scheme, the frequency response of the all-pass filter is controlled by a set of parameters with each parameter for a specified frequency range. For each image block, the best parameter is chosen from the set and is sent to the decoder as a side information along with the result of corresponding WDCT computation. For actual implementation, the combination of the all-pass IIR filters and the DCT can be viewed as a cascade of a warping matrix and the DCT matrix, or as a filter bank which is obtained by warping the frequency response of the DCT filter bank. Hence, the WDCT can be implemented by a single matrix computation like the DCT. The WDCT based compression, outperforms the DCT based compression, for high bit rate applications and for images with high frequency components.

  • PDF

Characteristics of the Electric and Magnetic Field Waveforms Radiated by Lightning Discharges (뇌방전에 의해 방사되는 전계와 자계파형의 특성)

  • 이복희;이경옥
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
    • /
    • v.7 no.4
    • /
    • pp.300-309
    • /
    • 1996
  • The electric and magnetic fields radiated by lightning discharges are significantly changeable in amplitude and time, one of the topics concerning electromagnetic compatibility of modern electronic systems is the efficient and economic protection against transient voltages caused by not only by direct but also by nearly lightning strokes. In this paper, in order to obtain the detailed informations about lightning electromagnetic impulse waveforms, the electric and magnetic fields radiated by lightning discharges in the summer of 1995 were measured by a fast electric antenna and a loop-type magnetic field sensor, and their charac- teristics were presented and analyzed. The signals of the electric and magnetic fields were re- corded continuously by a transient digitizer having a resolution of 12 bit and a memory capacity of 5000 point and using a sampling time of 200 ns. The electric and magnetic field waveforms associated with lightning return strokes are significantly different with those of intracloud discharges. The magnetic fields radiated by intracloud lightning discharges have essentially the same waveforms as the electric field when the lightning discharhes are at distance of 50 km or more. Also the main frequency components of the electric and magnetic fields radiated by lightning discharges range from a few kHz to several hundred kHz.

  • PDF

Pulse-mode Response Characteristics of a Small LRE for the Precise 3-axes Control of Flight Attitude in SLV (우주발사체의 비행자세 3축 정밀제어를 위한 소형 액체로켓엔진의 펄스모드 응답특성)

  • Jung, Hun;Kim, Jong Hyun;Kim, Jeong Soo;Bae, Dae Seok
    • Journal of the Korean Society of Propulsion Engineers
    • /
    • v.17 no.1
    • /
    • pp.1-8
    • /
    • 2013
  • A liquid-monopropellant hydrazine thruster has several outstanding advantages such as relatively-simple structure, long/stable propellant storability, clean exhaust products, and so on. Therefore hydrazine thruster has such a wide application as orbit and attitude control system (ACS) for space vehicles. A hydrazine thruster with the medium-level thrust to be used in the ACS of space launch vehicles (SLV) has been developed, and its ground firing test result is presented in terms of thrust, impulse bit, temperature, and chamber pressure. It is verified through the performance test that the response and repeatability of thrust are very excellent, and the thrust efficiencies compared to its ideal requirement are larger than 93%.

Performance improvement of underwater acoustic communication using ray-based blind deconvolution in passive time reversal mirror (수동형 시역전 기반의 음선 기반 블라인드 디컨볼루션 기법을 이용한 수중음향통신 성능 개선)

  • Oh, Se Hyun;Byun, Gi Hoon;Kim, J.S.
    • The Journal of the Acoustical Society of Korea
    • /
    • v.35 no.5
    • /
    • pp.375-382
    • /
    • 2016
  • This paper presents the results for the performance improvement of underwater communication in a passive time reversal mirror (PTRM) using ray-based blind deconvolution (RBD). In conventional PTRM, the signal to be recovered is found from matched-filtering the received probe signal. However, the communication performance is degraded because the time-varying impulse response for each data frame is not reflected in the received probe signal. In this study, the time-variant transfer function is estimated from each received data frame using RBD, and the estimated time-variant transfer function is then used to recover the data signal using PTRM. The results from the experimental data show that the suggested method improves the communication performance when comparing with the conventional PTRM.