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[Author] Hiromasa HABUCHI(30hit)

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  • Nonorthogonal CSK/CDMA with Received-Power Adaptive Access Control Scheme

    Nobuyoshi KOMURO  Hiromasa HABUCHI  Toshinori TSUBOI  

     
    PAPER-Communication Theory

      Vol:
    E91-A No:10
      Page(s):
    2779-2786

    The measurements for Multiple Access Interference (MAI) problems and the improvement of the data rate are key issues on the advanced wireless networks. In this paper, the nonorthogonal Code Shift Keying Code Division Multiple Access (CSK/CDMA) with received-power adaptive access control scheme is proposed. In our system, a user who is ready to send measures the received power from other users, and then the user decides whether to transmit or refrain from transmission according to the received power and a pre-decided threshold. Not only overcoming the MAI problems, but our system also improve the throughput performance. The throughput performance of the proposed system is evaluated by theoretical analysis. Consequently, the nonorthogonal CSK/CDMA system improves by applying received-power adaptive access control. It was also found that the throughput performance of the nonorthogonal CSK/CDMA system is better than that of the orthogonal CSK/CDMA system at any Eb/N0. We conclude that the nonorthogonal CSK/CDMA system with received-power adaptive access control scheme is expected to be effective in advanced wireless networks.

  • A Comparison of Wireless Optical CDMA Systems Using Chip-Level Detection

    Yusuke KOZAWA  Hiromasa HABUCHI  

     
    PAPER-Spread Spectrum Technologies and Applications

      Vol:
    E93-A No:11
      Page(s):
    2291-2298

    In this paper, the optimum combination of optical pseudo-noise (PN) code and modulation scheme to achieve high total data transmission rate is presented. Moreover, the bit error rate (BER) performance of a wireless OCDMA system using chip-level detection is evaluated through theoretical analysis in the multi-user case. It is shown that, in a wireless OCDMA system with chip-level detection, the total data transmission rate of a multi-pulse pulse position modulation (MPPM) systems with optical pseudo-noise code generated by an M-sequence is better than that of an MPPM system with optical orthogonal code and that of an MPPM system with an extended prime code sequence. Moreover, the total data transmission rate of an MPPM/SIK system using modified pseudo orthogonal M-sequence sets can achieve more than 1.0 [bit/chip].

  • Theoretical Analysis of New PN Code on Optical Wireless Code-Shift-Keying

    Yusuke TAKAMARU  Sachin RAI  Hiromasa HABUCHI  

     
    PAPER-Sequences

      Vol:
    E97-A No:12
      Page(s):
    2572-2578

    A code shift keying (CSK) using pseudo-noise (PN) codes for optical wireless communications with intensity/modulation and direct detection (IM/DD) is considered. Since CSK has several PN codes, the data transmission rate and the bit error rate (BER) performance can be improved by increasing the number of PN codes. However, the conventional optical PN codes are not suitable for optical CSK with IM/DD because the ratio of the number of PN codes and the code length of PN code, M/L is smaller than 1/√L. In this paper, an optical CSK with a new PN code, which combines the generalized modified prime sequence code (GMPSC) and Hadamard code is analyzed. The new PN code can achieve M/L=1. Moreover, the BER performance and the data transmission rate of the CSK system with the new PN code are evaluated through theoretical analysis by taking the scintillation, background-noise, avalanche photodiode (APD) noise, thermal noise, and signal dependent noise into account. It is found that the CSK system with the new PN code outperforms the conventional optical CSK system.

  • Optical Wireless LDGM-BPPM with Unequal Transmission Power Allocation Scheme

    Kyohei SUMIKAWA  Hiromasa HABUCHI  

     
    PAPER-Communication Theory and Signals

      Vol:
    E97-A No:12
      Page(s):
    2579-2585

    In this paper, the low density generator matrix (LDGM) coded scheme with unequal transmission power allocation (UTPA) in optical wireless channel is evaluated by computer simulation. In particular, the bit error rate performance of the LDGM-coded binary pulse position modulation (LDGM-BPPM) with the UTPA scheme is investigated in the presence of avalanche photo diode (APD) noise, scintillation and background noise. Consequently, the BER performance of the LDGM-BPPM with UTPA is better than that of the conventional LDGM-BPPM. It is found that there is the optimum power ratio (R). The optimum R varies with scintillation and background noise. For example, when the average received laser power is -47[dBm], the variance of scintillation is 0.1, and background noise is -45[dBm], the optimum R is 3.1. Thus, the LDGM-BPPM with the UTPA scheme is superior to the conventional LDGM-BPPM system.

  • Embedded Frame Synchronization Method for Pulse Position Modulation System

    Fumie ONO  Hiromasa HABUCHI  

     
    LETTER

      Vol:
    E89-A No:6
      Page(s):
    1757-1760

    The objective of this paper is to propose the Pulse Position Modulation (PPM) system which embeds the synchronizing signal in the information frame. In the proposed system, the frame for transmitting information is also the frame for acquiring frame timing. The data transmission rate of the proposed system is independent of the length of the synchronization signal because the proposed system does not require the synchronization frame. The data transmission rate and the synchronization performance for the proposed system are better than those of the conventional system.

  • Bi-Orthogonal Modulation Systems Using Two Different Inner Sequences

    Kouji OHUCHI  Hiromasa HABUCHI  

     
    PAPER

      Vol:
    E84-A No:12
      Page(s):
    2976-2982

    In this paper, we describe a frame synchronization method for bi-orthogonal modulation systems. In bi-orthogonal modulation systems, several bi-orthogonal sequences are used for data transmission. Frame synchronization in bi-orthogonal modulation systems is difficult because transmitted sequences can change every frame. In the proposed method, each bi-orthogonal sequence consists of two different inner sequences. Each bi-orthogonal sequence has the same arrangement of two different inner sequences. A receiver can track the frame timing by observing the arrangement of inner sequences. In this paper, we analyze the bit error rate performance that takes into account the tracking performance of a system we developed based on our method. The spectral efficiency of the proposed system in code division multiple access (CDMA) systems is also investigated. As a result, we found that the proposed system is effective in synchronous CDMA systems.

  • Bit Error Rate of Bi-orthogonal Systems Considering Synchronization Performance

    Hiromasa HABUCHI  Shun HOSAKA  

     
    PAPER

      Vol:
    E79-A No:12
      Page(s):
    1982-1987

    In this paper, the bit error rate (BER) considering tracking performance is evaluated, by theoretical analysis and computer simulation, for a bi-orthogonal system using a synchronizing pseudo-noise (PN) sequence and co-channel interference cancellers. A system that improves on Tachikawa's system is proposed. It is found that the optimum ratio of the information signal energy to the synchronizing signal energy varies with Eb/No, and the canceller is better for small L than for large L (L = length of the sequence). Moreover, it is found that the BER considering synchronization performance improvse as the equivalent noise bandwidth Bn decreases.

  • FOREWORD

    Ryuji KOHNO  Kazuo TSUBOUCHI  Peter JUNG  Masakazu SENGOKU  Tetsushi IKEGAMI  Hisao TACHIKA  Yukitsuna FURUYA  Yoshiharu TOZAWA  Takaaki HASEGAWA  Shigenobu SASAKI  Hiromasa HABUCHI  

     
    FOREWORD

      Vol:
    E79-A No:12
      Page(s):
    1927-1929
  • An Analysis of Frame Synchronization Systems with Racing Counters and Majority Rule for M-ary/SS Communication Systems

    Kouji OHUCHI  Hiromasa HABUCHI  

     
    PAPER

      Vol:
    E80-A No:12
      Page(s):
    2406-2412

    In this paper, a simple frame synchronization system for M-ary Spread Spectrum (M-ary/SS) communication system is analyzed. In particular, synchronization performance, bit error rate performance, and Spread Spectrum Multiple Access (SSMA) performance are analyzed. The frame synchronization system uses the racing counters. The transmitted signal contains framing chips that are added to spreading sequences. In the receiver, the framing chips are detected from several frames. The authors have proposed the simple frame synchronization system that detects framing chips from consecutive 2 frames. In this system, as the number of framing chips increases, synchronization performance improves and bit error rate performance degrades. In this paper a frame synchronization system that improves bit error rate performance is treated and analyzed. As the rusult, when the number of reference frames is 3, the bit error rate is much improved than the conventional system.

  • Proposal of a Simple Synchronization Method for CSK/SS

    Azumi ITO  Hiromasa HABUCHI  Fumie ONO  

     
    PAPER

      Vol:
    E88-A No:6
      Page(s):
    1455-1461

    In this paper, a new tracking method for Code Shift Keying Spread Spectrum (CSK/SS) is proposed. In the CSK/SS systems, since the transmitted sequences vary at every frame, synchronization is difficult. In the proposed method, a pair consists of the Manchester-coded PN sequence and the non-Manchester-coded PN sequence as the synchronizing sequence. The cross-correlation characteristic of the pair is used instead of the S-curve of delay lock loop (DLL). The receiver can track the signal timing by using the characteristic. The proposed method is applied to the external synchronization system whose structure is simple. The following performance in channel with the Additive White Gaussian Noise (AWGN) is analyzed and evaluated; (1) the tracking error (jitter) performance and (2) the bit error rate (BER) performance that takes the jitter into account. As a result, the jitter of the proposed system is better than those of the conventional DLL systems as Eb/N0 increases. The jitter of the proposed system has less degradation than those of the conventional systems, even if the number of users increases. Moreover, BER of the proposed system is similar to that of the 1Δ-DLL system and superior to that of the 2Δ-DLL system.

  • Design of UWB Pulses in Terms of B-Splines

    Mitsuhiro MATSUO  Masaru KAMADA  Hiromasa HABUCHI  

     
    PAPER-Pulse Shape

      Vol:
    E88-A No:9
      Page(s):
    2287-2298

    The present paper discusses a new construction of UWB pulses within the framework of soft-spectrum adaptation. The employed basis functions are B-splines having the following properties: (i) The B-splines are time-limited piecewise polynomials. (ii) The first-order B-splines are rectangular pulses and they converge band-limited functions at the limit that their order tends to infinity. (iii) There are an analog circuit and a fast digital filter for the generation of B-splines. Simple application of Gram-Schmidt orthonormalization process to the shifted B-splines results in a few basic pulses, which are well time-limited and have a broad band width, but do not comply with the FCC spectral mask. A constrained approximation technique is proposed for adaptively designing pulses so that they approximate target frequency characteristics. At the cost of using eleven shifted B-splines, an example set of four pulses comforting the FCC spectral mask is obtained.

  • A Study on the M–ary/SS Communication System Using a Frame Synchronization Method of PCM Communication Systems

    Kouji OHUCHI  Hiromasa HABUCHI  Takaaki HASEGAWA  

     
    LETTER

      Vol:
    E77-A No:11
      Page(s):
    1942-1945

    Synchronization has been one of the problems in M–ary spread spectrum communication systems. In this letter, we propose the frame synchronization method using the Hadamard matrix and a frame synchronization method of PCM communication systems. Moreover, we analyze the probabilities of keeping synchronous state and frame renewal rates, and we evaluate the relationship between these probabilities and the number of stages of counters.

  • A Tracking System Using a Differential Detector for M-ary Bi-orthogonal Spread Spectrum Communication Systems

    Junya KAWATA  Kouji OHUCHI  Hiromasa HABUCHI  

     
    PAPER

      Vol:
    E94-A No:12
      Page(s):
    2737-2745

    As an application of the direct sequence spread spectrum (SS) communication system, there is an M-ary bi-orthogonal SS communication system. In its system, several spreading sequences (bi-orthogonal sequences) are used in a code shift keying basis. Hence, design of the spreading code synchronization system has been an issue in the M-ary bi-orthogonal SS systems. In this paper, the authors focus on a code tracking system using a differential detector and a Delay Lock Loop (DLL). They investigate a tracking performance of their code tracking system by theoretical analysis. In addition, a multi-stage interference canceler is applied to the M-ary bi-orthogonal SS system. As the result, it is shown that the tracking performance of the theoretical analysis is almost the same as that of computer simulations in a multi-user environment. It is also shown that the multi-stage interference canceler is effective in improvement of the BER performance.

  • A Theoretical Analysis of the Synchronous SS-CSC/CDMA System

    Kouji OHUCHI  Hiromasa HABUCHI  Toshio TAKEBAYASHI  

     
    PAPER

      Vol:
    E81-A No:11
      Page(s):
    2291-2297

    In this paper, the bit error rate (BER) performance of the Spread Spectrum communication with Constrained Spreading Code system is studied under the synchronous CDMA system. Particularly, BER considering the tracking error is derived by theoretical analysis. The synchronizing spreading sequence is employed to track the signals in the receiver. As the result, the BER performance is degraded by increasing the number of users. However, the BER performance can be improved by canceling the co-channel interference and by suppressing the cross-correlation value between the information spreading sequence and the synchronizing spreading sequence.

  • Performance Comparison of M-Ary/SSMA Systems and DS/SSMA Systems in the Presence of Frequency Selective Fading and Partial-Band Interference

    Tsuyoshi ARAI  Hiromasa HABUCHI  

     
    PAPER

      Vol:
    E81-A No:11
      Page(s):
    2319-2326

    M-ary/SS systems are compared with DS/SS systems applied the multicarrier systems and the RAKE receiver in the presence of AWGN, frequency selective Rayleigh fading and partial-band interference. In particular, the BER performance and SSMA capability are evaluated. Consequently, the M-ary/SSMA system using the multicarrier techniques is subject to the M-ary/SSMA system with the RAKE receiver in the presence of partial-band interference. The BER performance of the M-ary/SSMA system is better than that of the DS/SSMA system when the number of users is smaller than 20. And the spectral efficiency of the multicarrier M-ary/SSMA system is best in the four systems when JSR=20 [dB] and BER=10-3.

  • A Self-Synchronization Method for the SS-CSC System

    Hiromasa HABUCHI  Toshio TAKEBAYASHI  Takaaki HASEGAWA  

     
    PAPER

      Vol:
    E80-A No:12
      Page(s):
    2398-2405

    In this paper, a simple frame synchronization method for the SS-CSC syytem is proposed, and the synchronization performance is analyzed. There have been growing interests in the M-ary/SS communication system and the bi-orthogonal modulation system because these systems can achieve the high frequency utilization efficiency. However, the frame synchronization is difficult. We proposed the SS-CSC system, and evaluated the bit error rate (BER) performance of the SS-CSC system under the completed synchronization. The BER performance of the SS-CSC system is much the same as that of the bi-orthogonal modulation system. In this paper, a frame synchronization method using the differential detector and racing counters is proposed. In particular, the lose lock time, the recovery time and the BER performance considering the synchronizing performance are analyzed. In consequence, the BER performance considering the synchronization performance can approach the lower bound of the SS-CSC system by tuning the number of the stages in racing counters.

  • Free Space Optical Turbo Coded Communication System with Hybrid PPM-OOK Signaling

    Ran SUN  Hiromasa HABUCHI  Yusuke KOZAWA  

     
    PAPER

      Vol:
    E103-A No:1
      Page(s):
    287-294

    For high transmission efficiency, good modulation schemes are expected. This paper focuses on the enhancement of the modulation scheme of free space optical turbo coded system. A free space optical turbo coded system using a new signaling scheme called hybrid PPM-OOK signaling (HPOS) is proposed and investigated. The theoretical formula of the bit error rate of the uncoded HPOS system is derived. The effective information rate performances (i.e. channel capacity) of the proposed HPOS turbo coded system are evaluated through computer simulation in free space optical channel, with weak, moderate, strong scintillation. The performance of the proposed HPOS turbo coded system is compared with those of the conventional OOK (On-Off Keying) turbo coded system and BPPM (Binary Pulse Position Modulation) turbo coded system. As results, the proposed HPOS turbo coded system shows the same tolerance capability to background noise and atmospheric turbulence as the conventional BPPM turbo coded system, and it has 1.5 times larger capacity.

  • Optical Wireless N-CSK with Modified Pseudo Orthogonal M-Sequence Sets

    Yusuke KOZAWA  Hiromasa HABUCHI  

     
    PAPER-Spread Spectrum Technologies and Applications

      Vol:
    E94-A No:11
      Page(s):
    2188-2193

    In this paper, N-CSK (N parallel Codes Shift Keying) using modified pseudo orthogonal M-sequence sets (MPOMSs) to realize the parallel combinatory spread spectrum (PC/SS) communication system for the optical communications is proposed. Moreover, the upper bound of data transmission rate and the bit error rate (BER) performance of this N-CSK system using the chip-level detection are evaluated through theoretical analysis by taking into account the scintillation, background-noise, avalanche photo-diode (APD) noise, thermal noise, and signal dependence noise. It is shown that the upper bound of data transmission rate of the proposed system is better than those of OOK/CDM and SIK/CDM. Moreover, the upper bound of data transmission rate of the proposed system can achieve about 1.5 [bit/chip] when the code length of MPOMS is 64 [chip].

  • Influence of Phase Difference between the Groups on BER Performance in the 2M-Plex System

    Hiromasa HABUCHI  Takaaki HASEGAWA  

     
    LETTER

      Vol:
    E76-B No:7
      Page(s):
    748-750

    Recently, there has been increasing interest in Code Division Multiplex (CDM) systems. We reported the CDM system using the -chip shift multiplex operation. So far the performance of this system evaluated under the optimum . In this letter, we evaluate an influence of the phase difference between the groups on BER performance in 2M-plex system.

  • FOREWORD

    Hiromasa HABUCHI  

     
    FOREWORD

      Vol:
    E99-A No:1
      Page(s):
    158-158
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