L a b R e s e a r c h


International Conference Papers
34. Educational Criteria for Evaluating Simple Class Diagrams made by Novices for Conceptual Modeling
M. Kayama, S. Ogata, D.K. Asano, M. Hashimoto, Proc. of 13th International Conference on Cognition and Exploratory Learning in the Digital Age (CELDA 2016) Mannheim, Germany, pp.319-323, October 28-30, 2016.
  Conceptual modeling is one of the most important learning topics for higher education and secondary education. The goal of conceptual modeling in this research is to draw a class diagram using given notation to satisfy the given requirements. In this case, the subjects are asked to choose concepts to satisfy the given requirements and to correctly extract the relations between objects and services. In this paper, we aim to propose criteria for evaluating conceptual modeling errors made by university freshmen. To achieve this research goal, we quantitatively analyzed class diagrams made by novice learners. Based on the results of three types of experiments, we propose 12 criteria, which are divided into 4 types, for evaluating class diagrams made by novices.


33. Realization of a safe and secure society using ICT in Shiojiri-city, Nagano Prefecture, Japan
H. Suzuki, Y. Fuwa, D.K. Asano, M. Komatsu, Y. Takeshita, M. Futagawa, E. Motoyama, S. Seryu, H. Kaneko, Proc. 2nd International Conference on Information & Communication Technologies for Disaster Management (ICTDM 2015), Rennes, France, 7 pages, November-December, 2015.
  For some time, we have been working toward the "Realization of a Safe and Secure Society using ICT in Shiojiri-City, Nagano Prefecture." This is a project comprised of two phases: information gathering, and dissemination of information. For information gathering, we are developing systems to confirm the whereabouts of children and the elderly, who are vulnerable in disasters, and systems to gather information on the situation in mountainous regions, rivers etc. For dissemination of information, we are developing systems using broadcast technology for disseminating information to residents, such as disaster information and evacuation warnings derived from the gathered information. This presentation will describe the project goals, the background of the project thus far, and an overview of the developed system. The current situation and plans for the future will also be discussed.


32. Occupied Bandwidth Comparison of BBOST-CPM with Two Transmit Antennas
K. Morioka, N. Kanada, S. Futatsumori, A. Kohmura, N. Yonemoto, Y. Sumiya, D. Asano, Proc. International Symposium on Antennas and Propagation (ISAP2015), Hobart, Australia, 4 pages, November, 2015.
  Continuous phase modulation (CPM) has constant envelope and good spectral properties, so it is suitable for satellite communication systems which require high power amplifiers. On the other hand, recent broadband mobile communication systems use space time block codes (STBC) to achieve channel gain by using multiple antennas. Burst based orthogonal space timecontinuous phase modulation (BBOST-CPM) is a combination of orthogonal STBC and CPM which takes advantages of both merits. In this paper, we compare the occupied bandwidth of BBOST-CPM with two transmit antennas. We consider the relationship between modulation parameters and occupied bandwidth in detail. The results are useful for designing BBOST-CPM for future satellite communication systems.


31. A Program Complexity Metric based on Variable Usage for Algorithmic Thinking Education of Novice Learners
M. Fuwa, M. Kayama, H. Kunimune, M. Hashimoto, D.K. Asano, Proc. of the 12th International Conference on Cognition and Exploratory Learning in the Digital Age (CELDA 2015), Maynooth, Ireland, pp.262-266, October, 2015.
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  We have explored educational methods for algorithmic thinking for novices and implemented a block programming editor and a simple learning management system. In this paper, we propose a program/algorithm complexity metric specified for novice learners. This metric is based on the variable usage in arithmetic and relational formulas in learner's algorithms. To evaluate the applicability of this metric for novice education, we discuss the differences between three previous program complexity metrics and our proposed metric.


30. Development of a High School Computer Science Learning Tool for Bit Synchronization in Network Protocols
W. Minoura, M. Kayama, Y. Fuwa, M. Hashimoto, D.K. Asano, Proc. of the 2015 International Conference on Interactive Collaborative Learning (ICL 2015), Florence, Italy, 8 pages, September, 2015.
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  The purpose of this study is to develop problem-solving based learning tools to nurture sound knowledge and abilities about "Information Studies (or Informatics)". Based on the survey on Japanese high school students' comprehension of communication networks, our first tool focuses on teaching the basic principles of network protocols. This tool gives students hands-on experience to help them understand. In this paper, we describe the conceptual design and preliminary evaluation of this tool.


29. An Implementation of CPFSK-OFDM Systems by using Software Defined Radio
K. Morioka, N. Kanada, S. Futatsumori, A. Kohmura, N. Yonemoto, Y. Sumiya, D. Asano, Proc. of the 15th IEEE Wireless and Microwave Technology Conference (WAMICON 2014), Tampa, Florida, 3 pages, June, 2014.
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  In this paper, CPFSK-OFDM systems which use CPFSK (Continuous Phase Frequency Shift Keying) as the first modulation scheme of OFDM (Orthogonal Frequency Division Multiplexing) are considered. We implemented CPFSK-OFDM systems by using software defined radio and evaluated them in an AWGN (Additive White Gaussian Noise) channel. We found that the performance is better when the modulation index of CPFSK is 0.75. In the future, we will evaluate our system in a real environment.


28. Experiments of VoIP using WiMAX System and Fading Simulator with Two-Path Models for Aeronautical Scenarios
K. Morioka, N. Kanada, S. Futatsumori, A. Kohmura, N. Yonemoto, Y. Sumiya, D. Asano, Proc. of the 2014 Integrated Communications Navigation and Surveillance Conference (ICNS2014), Washington D.C., 8 pages, April, 2014.
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  In this paper, we study the performance of VoIP over WiMAX systems. We assume a two-path model for airport surface communications and experiment by using a multipath fading simulator. We evaluate the R-factor when the mobile speed and delay time are changed. We use an R-factor of 80 which is defined in ED-136 as a threshold where VoIP can be used for air traffic control (ATC). When the delay time is 0 -20ns i.e., the horizontal distance is over 40m and if the mobile speed is under 50 km/h, the R-factor is over 80. On the other hand, in takeoff and landing scenarios when the mobile speed is over 300 km/h, it is difficult to keep the quality of VoIP and some improvements in the receiver are needed.


27. EVM and BER Evaluation of C band New Airport Surface Communication Systems
K. Morioka, N. Kanada, S. Futatsumori, J. Honda, A. Kohmura, N. Yonemoto, Y. Sumiya, D. Asano, Proc. of the 2014 International Workshop on Antenna Technology (iWAT2014), Sydney, Australia, pp. 255-258, March, 2014.
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  AeroMACS (Aeronautical Mobile Airport Communication System) is proposed for future airport surface communication system in the C band. In this paper, we report the results of an experiment at Sendai airport in Japan to evaluate the AeroMACS. Our base station covers the approximately 3km x 1km rectangular airport surface with a transmitter power of 1W. A BER (Bit Error Rate) of less than 10-6 is required at the physical layer in order to realize reliable data communication systems. However, measurement of the BER is difficult especially in field experiments because another data link is required to inform the receiver of the correct transmitted symbols. Therefore, we calculate the relationship between EVM (Error Vector Magnitude) and BER by computer simulation, then translate the EVM which is measured in the experiment into BER. The results show that 64QAM-3/4 can be used with a BER of less than 10-6 in 64.3% of the LOS (Line Of Sights) area and 64QAM cannot be used in almost all NLOS (Non Line Of Sights) areas at Sendai airport.


26. Performance Evaluation of AeroMACS using existing WiMAX System in Japanese High-Speed Trains
K. Morioka, N. Kanada, S. Futatsumori, A. Kohmura, N. Yonemoto, Y. Sumiya, D. Asano, Proc. of the 5th Thailand-Japan MicroWave (TJMW2013), Bangkok, Thailand, (2 pages), December, 2013.
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  AeroMACS (Aeronautical Mobile Communication System) is being developed in order to provide new broadband wireless communications on the airport surface. In this paper, results of experiments using existing WiMAX (Worldwide Interoperability for Microwave Access) systems and Japanese high-speed trains (Shinkansen) are reported. We consider the capability of the AeroMACS system in high-speed scenarios, e.g. take-offs and landings. The relationship among frequency offset, moving speed and throughput are analyzed. We found that transmission of movies during take-off and landing is possible if CINR on the runway is higher than about 24dB and the base station is set at an appropriate position to reduce the influence of the Doppler shift.


25. Performance Analysis of a Serial UEP System Based on Time-Division Multiplexing Codes
S. Yamazaki, D. Asano, Proc. of the 2013 International Workshop on Smart Info-Media Systems in Asia (SISA 2013), Nagoya, Japan, pp. 139-144, Sept.-Oct. 2013.
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  Previously, we proposed a serial unequal error protection (UEP) code system or use with information sources that contain a mixture of both important and less important data. Moreover we showed the effectiveness of the proposed system with symmetrical signal constellations (2RING type). In this paper, we show theoretical analysis of the asymmetrical signal constellations, which are called TRAP (trapezoid) type in AWGN channels and evaluate the validity using computer simulations. In addition, we show the performance in fading channels. Therefore, we showed the effectiveness of the TRAP type in the propose UEP system.


24. Theoretical Performance for the Transmit Power in Multi-hop Wireless Networks
S. Yamazaki, H. Iwase, D.K. Asano, Proc. of the 10th IEEE Asia Pacific Wireless Communications Symposium (APWCS 2013), Seoul, Korea, pp. 434-437, August 2013.
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  In the future, a very large amount of transmitted power is required to realize transmission rates such as 1Gbps. As a solution to this problem, multi-hop communications have received much attention. In this paper, we theoretically derive a closed form expression for the transmitted power in linear multihop networks. Moreover, we showed the validity of the proposed method by comparing the theoretical performance with computer simulations. For the parameters we used in our evaluation, we could show that 1.14W less transmitted power is required to transmit the same amount of data when there are 5 relay nodes compared to direct communication. In the future, we wish to analyze the power of the whole multi-hop network including the power consumption of the terminal.


23. Research on the Construction of an Ad-Hoc Network System for Flexibly Dealing with Disasters
H. Suzuki, D.K. Asano, M. Komatsu, Y. Takeshita, K. Sawada, M. Futagawa, H. Nose, Y. Fuwa, Proc. of the 28th International Technical Conference on Circuits/Systems, Computers and Communications (ITC-CSCC 2013), Yeosu, Korea, pp. 24-27, June 30 - July 3, 2013.
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  In order to mitigate disasters, it is important to collect and use various kinds of information when a disaster strikes. Therefore, it is extremely important create sensor technology for acquiring information and to establish a communication infrastructure for conveying the acquired information. Here, we describe the communication infrastructure. When a large-scale disaster occurs, the entire communication infrastructure may collapse. Also, when a disaster occurs in the mountainous area, there often isn't even a communication infrastructure present in that area in the first place. Therefore, we designed a communication infrastructure using an adhoc network. The ad-hoc network we have in mind does not involve placing transponders in advance, as is conventional, but instead aims to construct a communication infrastructure by quickly establishing transponders in times of emergency. In this essay, we touch on the problems and solutions in ad-hoc networks for creating such a communication infrastructure.


22. Construction of a Sensor Network to Forecast Landslide Disasters - Sensor Terminal Development and On-Site Experiments
H. Suzuki, D. Kuroyanagi, D.K. Asano, M. Komatsu, Y. Takeshita, K. Sawada, M. Futagawa, H. Nose, Y. Fuwa, Proc. of the 11th International Conference on Wired/Wireless Internet Communications (WWIC 2013), St. Petersburg, Russia, LNCS 7889, pp. 180-191, June 2013.
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  We believe it is extremely important to quickly communicate information - on matters such as the extent of the damage and the safety of affected persons - when a large-scale earthquake or other disaster occurs. However, if electric power is lost, communication will be impossible with existing information networks. For this reason, we have built an Ad-Hoc network in Shiojiri City enabling communication even if electric power is lost due to a large-scale disaster. Using this Ad-Hoc network, we are building a sensor network to forecast landslide disasters. Among the various sensors installed to the sensor terminals, this paper reports in particular on observation results with EC sensors.


21. A Serial Unequal Error Protection Codes System using AEPF-DFE for Fading Channels
S. Yamazaki and D. K. Asano, Proc. of the International Conference on Electrical Engineering 2012 (ICEE 2012), Kanazawa, Japan, pp. 336-341, July 8-12, 2012.
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  In our previous research, we proposed a serial unequal error protection (UEP) code system for use with information sources that contain a mixture of both important and less important data. Previously, theoretical analyses were presented, and the effectiveness and the validity of the system for additive white Gaussian noise (AWGN) channels was confirmed using theoretical analyses and computer simulations. On the other hand, we proposed an adaptive error prediction filter with a decision feedback equalizer (AEPF-DFE) to achieve faster convergence and lower computational cost during the tracking period. In this paper, we propose our UEP system using AEPF-DFE for fast and selective fading channels. We confirm the improvement in BER performance and the effectiveness of adaptive equalization for the proposed system in fading channels. Also, we confirm the predominance of the proposed system by comparing the previous scheme, that is, the case using a simple DFE.


20. A Serial Unequal Error Protection Codes System using MMSE-FDE for Fading Channels
S. Yamazaki and D. K. Asano, Proc. of the 8th IEEE Asia Pacific Wireless Communication Symposium (APWCS 2011), Singapore, (5 pages), Aug. 22-23, 2011.
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  In our previous research, to achieve unequal error protection (UEP), we proposed a scheme which encodes the data by randomly switching between several codes which use different signal constellations and showed the effectiveness in AWGN channels. In this paper, we propose our UEP system using MMSE-FDE (frequencydomain equalization based on the minimum mean square error criterion) for fast and selective fading by using the fact that importance levels are changed every few symbols, i.e., every block, in the proposed system. We confirmed the improvement in BER performance and the effectiveness of adaptive equalization for the proposed system in fading channels. As a result, we showed that a UEP system is realizable in mobile telecommunications environments.


19. A Tabletop-Based Real-World-Oriented Interface
H. Takeda, H. Miyao, M. Maruyama and D. Asano, Proc. of the 14th International Conference on Human-Computer Interaction (HCII 2011), Orlando, Florida, USA, pp. 133-139, July 9-14, 2011.
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  In this paper, we propose a Tangible User Interface which enables users to use applications on a PC desktop in the same way as a paper and pen on a desk in the real world. Also, the proposed system is cheaper to implement and can be easily setup anywhere. By using the proposed system, we found that it was easier to use than normal application user interfaces.


18. Single-carrier Transmission Frequency-domain Equalization Based on a Wiener Filter
S. Yamazaki and D. K. Asano, Proc. of the 2010 International Symposium on Communications and Information Technologies (ISCIT 2010), Tokyo, Japan, pp. 683-688, Oct. 26-29, 2010.
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  Recently, frequency-domain equalization for single-carrier transmission (SC-FDE) has been given much attention. For example, the up-link in the 3.9 generation mobile phone long term evolution (LTE) system, an SC-FDMA method using SC-FDE and multiple access will be adopted. However in previous research, there are many papers describing the features and advantages of SC-FDE based on a comparison of SC-FDE and othogonal frequency-division multiplexing (OFDM) systems. In this paper, we discuss single-carrier transmission equalization in the time-domain (SC-TDE) and SC-FDE in a unified way centered on the Wiener filter based on the minimum mean square error (MMSE) criterion. As a result, we could get useful information and pointers, especially for when we want to replace existing SC-TDE technology with SC-FDE technology.


17. Performance Evaluation of an OFDMA/TDD System using EVM and BER for Mobile WiMAX - Field Experiments and Computer Simulations -
S. Yamazaki and D. K. Asano, Proc. of the 2010 International Symposium on Communications and Information Technologies (ISCIT 2010), Tokyo, Japan, pp. 677-682, Oct. 26-29, 2010.
  In this paper, we focused on the physical layer of mobile-WiMAX and showed the performance of a WiMAX base station in the field using the EVM and BER performance measures. We obtained the theoretical performance, the performance using computer simulations and the performance from field experiments and evaluated the overall performance for WiMAX/OFDM systems. As a result, we could show the effectiveness for the system using computer simulations and field experiments and get a clue to evaluate the performance of a WiMAX base station.


16. Performance Evaluation of a Decision Feedback Equalizer with an Adaptive Error Prediction Filter
S. Yamazaki and D. K. Asano, Proc. of the 2009 International Symposium on Intelligent Signal Processing and Communication Systems (ISPACS 2009), Kanazawa, Japan, pp. 615-618, Dec. 7-9, 2009.
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  We proposed an Adaptive Error Prediction Filter with a Decision Feedback Equalizer (AEPF-DFE) to achieve faster convergence and lower computational cost during the tracking period. An AEPF is a linear predictive filter that updates its coefficients using an adaptive algorithm. We got the basic characteristic about an AEPFDFE and the effectiveness was shown using computer simulations. Specially, using a step size of 0.05 and a forgetting factor of 0.7 for the channels considered in this evaluation, we confirmed the effectiveness and domination of the AEPF-DFE in terms of convergence, bit error rate and computational load by computer simulations.


15. A Serial Unequal Error Protection Code System using Multilevel Trellis Coded Modulation with Two Ring Signal Constellations for AWGN Channels
S. Yamazaki and D. K. Asano, Proc. of the 2009 International Symposium on Intelligent Signal Processing and Communication Systems (ISPACS 2009), Kanazawa, Japan, pp. 315-318, Dec. 7-9, 2009.
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  A serial Unequal Error Protection (UEP) code system for use with information sources that contain a mixture of both important and less important data is proposed. To achieve UEP, the proposed scheme uses a form of Trellis Coded Modulation (TCM) which encodes the data by switching between two codes that use different signal constellations. The proposed system uses two ring signal constellations (2RING). No extra information about which code was used is added. The receiver decides which code was used by examining the received signal points. In this paper, a theoretical analysis of the 2RING signal constellation is presented, and the effectiveness of the system for AWGN channels is shown using computer simulations.


14. A Serial Unequal Error Protection Code System using a Decision Feedback Equalizer for Fading Channels
S. Yamazaki and D. K. Asano, Proc. of the 12th International Symposium on Wireless Personal Multimedia Communications (WPMC 2009), Sendai, Japan, Sept. 7-10, 2009.
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  We propose a serial unequal error protection (UEP) system using a ring-type signal constellation, a trellis coded modulation and a decision feedback equalizer for use in mobile fading channel communication environments. We confirmed the fundamental operation and showed the effectiveness of the system using computer simulations.


13. A Serial Unequal Error Protection Code System using Trellis Coded Modulation and an Adaptive Equalizer for Fading Channels
S. Yamazaki and D. K. Asano, Proc. of the 14th Asia-Pacific Conference on Communications (APCC 2008), Tokyo, Japan, Oct. 14-16, 2008.
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  We propose a serial unequal error protection (UEP) scheme using trellis coded modulation and an adaptive equalizer for use in mobile fading channel communication environments. We propose two types of signal constellations, TRAP and RING, to realize unequal error protection and show their performance in fading channels using computer simulations.


12. An Implementation of a Software Radio using an FPGA
Y. Izawa, D. K. Asano and D. Takeuchi, Proc. of the 2nd Magneto-Electronics International Symposium (magel '99), Nagano, Japan, pp. 351-353, Oct. 20-22, 1999.
[ PDF ]   In this paper, an implementation of an AM radio receiver using a Field Programmable Gate Array (FPGA) is described. By using this approach, the flexibility of software and the speed of hardware can be combined, i.e., the receiver construction can be modified without new hardware. The receiver consists of a processor core and several logic blocks. Audio signal processing and adaptive control of the RF signals are performed by the processor, while the logic blocks handle high-speed signal processing tasks such as envelope detection. To program the FPGA, all of the circuits are first described using HDL, then the circuit description is downloaded to the FPGA. The experimental board that was built is described and some problems using this approach are reported.


11. Coding for Limiter-Discriminator Based CPM Transceivers in a Rayleigh, Fast Fading Channel
D. K. Asano, S. Pasupathy and R. Kohno, Proc. of the 10th International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC '99), Osaka, Japan, pp. B5-3.1 - B5-3.5, Sept. 12-15, 1999.
[ PDF ]   A coding technique for limiter-discriminator based CPM transceivers is proposed for use in Rayleigh, fast fading environments. The proposed technique maintains the same bandwidth to information rate ratio as the uncoded system and therefore does not cause bandwidth expansion. The performance of the proposed coding scheme is compared to trellis coded modulation (TCM) and found to be better. It is also found that the increase in performance as the code complexity is increased is larger for the proposed scheme than for TCM.


10. Efficient Block and Convolutional Coding of GMSK
D. K. Asano, S. Pasupathy, Proc. of the 10th International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC '99), Osaka, Japan, pp. D5-5.1 - D5-5.5, Sept. 12-15, 1999.
[ PDF ]   In this paper, block and convolutional coding for Gaussian Minimum Shift Keying is investigated. The improvement in performance that can be obtained without an increase in bandwidth is found as a function of the block length for block codes and as a function of the constraint length for convolutional codes. For a fixed system transmission bandwidth, the tradeoff between the percentage of bandwidth to use for coding and the percentage to use for modulation is examined and optimized for various values of bandwidth.


9. Modulation and Processing Gain Tradeoffs in DS-CDMA Spread Spectrum Systems
D. K. Asano, T. Hayashi and R. Kohno, Proc. of the IEEE Fifth International Symposium on Spread Spectrum Techniques & Applications (ISSSTA '98), Sun City, South Africa, pp. 9-13, Sept. 2-4, 1998.
[ PDF ]   In this paper, Continuous Phase Modulation schemes are examined for use in DS-CDMA spread spectrum systems. Since the power spectra of Continuous Phase Modulation schemes are narrower than BPSK schemes, a larger processing gain can be used for the same overall bandwidth after spreading. The process ing gain, relative to BPSK, that can be used with Continuous Phase Modulation is calculated. As an example, it is shown that the performance of an MSK system is better than a BPSK system for an equivalent overall bandwidth.


8. Enhanced Conceptual Design Formulae for Frequency Channel Double Reuse Digital Systems using Sectored Cells
Y. Kinoshita and D. K. Asano, Proc. of the 1998 IEEE Vehicular Technology Conference (VTC '98), Ottawa, Canada, pp. 679-682, May 18-21, 1998.
[ PDF ]   To enhance frequency utilization efficiency, cellular mobile radio systems widely use a sector cell structure for the base stations. In this paper, the conceptual design formula previously reported are extended for frequency double reuse indoor picocellular systems. A three sector cell structure is adopted for the urban cellular base stations and omni-directional base stations are used for the indoor system, which is in the final stage of implementation. In particular, the small cluster size case is analyzed for TDMA cellular systems.


7. Performance Analysis of a New Decision-Avoided Handover Algorithm for DS-CDMA Indoor Pico-cellular Systems
Y. Kinoshita, H. Ohno and D. K. Asano, Proc. of the 1998 IEEE Vehicular Technology Conference (VTC '98), Ottawa, Canada, pp. 1044-1048, May 18-21, 1998.
[ PDF ]   Handover control of indoor pico-cellular radio systems becomes unstable due to severe multipath fading in buildings. The previously proposed decision-avoided handover algorithm can greatly improve the robustness of indoor handover control. This paper analyzes soft handover control algorithms for indoor DS-CDMA systems. The soft handover algorithm exhibits the same robustness as the decision-avoided algorithm. Also, the proposed algorithm can increase the utility of pico-cell base stations, because this approach does not use any channels of the base station receiving handoff.


6. Frequency Double Reuse for Indoor and Urban Digital Cellular Telephone Systems - Enhanced Conceptual Design Formulae for Single Handset Systems -
Y. Kinoshita and D. K. Asano, Proc. of the 1997 Multiaccess, Mobility and Teletraffic for Personal Communications Workshop (MMT '97), Melbourne, Australia, pp. 247-257, Dec. 15-17, 1997.
[ PDF ]   This year in Japan, the standardization of the digital frequency double reuse system was proposed and the standardization process is proceeding. This paper presents conceptual design formulae for a digital system. These formulae enhance the previous analog design formulae by introducing two parameters in the wave propagation model.


5. Unequal Error Protection Scheme Using Several Convolutional Codes
M. Matsunaga, D.K. Asano and R. Kohno, Proc. of the 1997 IEEE International Symposium on Information Theory (ISIT '97), Ulm, Germany, p. 101, June 29 - July 4, 1997.
[ PDF ]   This paper proposes and investigates a coding and decoding scheme to achieve for unequal error protection (UEP) using several convolutional codes with different error-correcting capabilities. An upper bound of decoder-selection-errors (DSE) in decoding is derived. We search good sets of codes which can reduce DSE, and introduce a biased metric in decoding to compensate performance degradation due to DSE.


4. Unequal Error Protection Based on Multidimensional Coded Modulation Using Several Convolutional Encoders
M. Matsunaga, D.K. Asano and R. Kohno, Proc. of the 1996 IEEE Workshop on Intelligent Signal Processing and Communication Systems (ISPACS '96), Singapore, pp. 1658-1662, Nov. 25-29, 1996.
[ PDF ]   It is essential for intelligent error control schemes to use a coding method which can adapt the error-correcting capability to the changing importance of the information. This paper proposes and investigates a multidimensional coded modulation scheme to achieve unequal error protection using convolutional codes which have different error-correcting capability. An appropriate encoder is selected every frame, which consists of a constant number of data symbols, according to the importance of each frame. In decoding, however, there is a problem of decoder-selection-error, which is an error that results when the decoder that is selected is not the same as the encoder used in the transmitter. In order to reduce the decoder-selection-errors, the proposed scheme assigns a signal constellation and encoder to each frame according to its importance, because these constellations can be used to determine the correct decoder. Computer simulation is employed to evaluate the bit error rate performance of the proposed scheme. The performance is compared with a conventional error control scheme and it is found that the proposed scheme can outperform the conventional one.


3. A TCM-based Unequal Error Protection Scheme for Intelligent Communication
D.K. Asano and R. Kohno, Proc. of the 1996 International Symposium on Information Theory and its Applications (ISITA '96), Victoria, B.C., Canada, pp. 203-206, Sept. 17-20, 1996.
[ PDF ]   Unequal error protection codes that are designed using trellis coded modulation are proposed for use with intelligent communication systems, where the transmitted data consists of a random mixture of important and less important information. To achieve unequal error protection, the proposed scheme encodes the data by randomly switching between two codes which use different signal constellations. No extra information about which code was used is added. The receiver decides which code was used by examining the received signal points. Using simple trellis codes, it is shown that the error rate of the important information can be made lower than the error rate for an equivalent equal error protection scheme.


2. Combined Source and Channel Coding System Using Different Importance of Multi-Media Information
S. Fujioka, D.K. Asano and R. Kohno, Proc. of the 1996 International Symposium on Information Theory and its Applications (ISITA '96), Victoria, B.C., Canada, pp. 472-475, Sept. 17-20, 1996.
[ PDF ]   In this paper, we propose a combined source and channel coding system for multimedia information sources, which outputs different kinds of information on a frame by frame basis. We use a source encoder which has several probability tables for each medium and a channel encoder which has several convolutional codes for unequal error protection. Computer simulation shows the performance of our system.


1. Phase Smoothing Functions for Full Response CPM
D.K. Asano, H. Leib, S. Pasupathy, Proceedings of the 1989 Pacific Rim Conference on Computers, Communications and Signal Processing (PACRIM '89), Victoria, B.C., pp. 316-319, June 1-2, 1989.
[ PDF ]   Continuous Phase Modulation (CPM) is examined for low complexity receivers, i.e., those that operate on only one symbol interval. The tradeoff between the bandwidth and bit error rate (BER) performance of these simple systems is studied. The phase smoothing functions that minimize the effective bandwidth for a given BER are calculated. A linear and a polynomial approximation to these phase smoothing functions are chosen. The three families are compared using their bandwidth-BER performance tradeoffs, power spectral densities, out-of-band powers and bandwidth efficiencies. It is shown that CPM schemes with small modulation indices (h <= 0.5) offer good tradeoffs between bandwidth and BER performance.