Professor Watit Benjapolakul, D. Eng.
ศ. ดร.วาทิต เบญจพลกุล
Education
- D. Eng. (Electronics), University of Tokyo, Japan
- M. Eng. (Electronics), University of Tokyo, Japan
- B. Eng. (1st Class Honor in Electrical Engineering), Chulalongkorn University, Thailand
Email: Watit.B@chula.ac.th
Research Interest
- 5G and Beyond
- Internet of Things
- Artificial Intelligence
- Machine Learning
- Data Analytics
- Big Data
- Smart Grid and Renewable Energy
- Smart Health
- Smart City
- Smart Factory
- Smart Railway
Research Cluster
1.
Le, N T; Asdornwised, W; Chaitusaney, S; Benjapolakul, W
Application of the mixed effects model for analysing photovoltaic datasets and interpreting into meaningful insights Journal Article
In: IET Generation, Transmission and Distribution, 2021, ISSN: 17518687, (cited By 0).
@article{Le2021,
title = {Application of the mixed effects model for analysing photovoltaic datasets and interpreting into meaningful insights},
author = {N T Le and W Asdornwised and S Chaitusaney and W Benjapolakul},
url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85102276868&doi=10.1049%2fgtd2.12160&partnerID=40&md5=396986630bf342b005b547783065c238},
doi = {10.1049/gtd2.12160},
issn = {17518687},
year = {2021},
date = {2021-01-01},
journal = {IET Generation, Transmission and Distribution},
publisher = {John Wiley and Sons Inc},
abstract = {Energy power studies commonly apply the analysis of variance (ANOVA) method in data analysis context to find the significant difference among many compared groups or to evaluate the impact of an influential factor. However, most of the datasets in these studies are time series data or longitudinal data, which are collected from the same object over some periods. Therefore, violating the independent assumption of ANOVA is the error commonly made. This leads to the misinterpretation of the comparison tests. In this article, this problem is solved by providing the application of mixed effects model (MEM) as a viable alternative to the ANOVA. In detail, two models based on MEM are proposed to analyse the time series data of micro-inverter PV stations located in Concord city, Massachusetts, USA. In the first scenario, the average models are implemented to compare the seasonal variation of monthly yield taking into account the effects of shading conditions and different orientations. In the second scenario, the linear regression model based on MEM is implemented to estimate and compare the decline rate in a 6-year period of PV stations. The analysis results have shown that the models based on MEM performs better than ANOVA in interpreting raw time-series dataset into meaningful insights. © 2021 The Authors. IET Generation, Transmission & Distribution published by John Wiley & Sons Ltd on behalf of The Institution of Engineering and Technology},
note = {cited By 0},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Energy power studies commonly apply the analysis of variance (ANOVA) method in data analysis context to find the significant difference among many compared groups or to evaluate the impact of an influential factor. However, most of the datasets in these studies are time series data or longitudinal data, which are collected from the same object over some periods. Therefore, violating the independent assumption of ANOVA is the error commonly made. This leads to the misinterpretation of the comparison tests. In this article, this problem is solved by providing the application of mixed effects model (MEM) as a viable alternative to the ANOVA. In detail, two models based on MEM are proposed to analyse the time series data of micro-inverter PV stations located in Concord city, Massachusetts, USA. In the first scenario, the average models are implemented to compare the seasonal variation of monthly yield taking into account the effects of shading conditions and different orientations. In the second scenario, the linear regression model based on MEM is implemented to estimate and compare the decline rate in a 6-year period of PV stations. The analysis results have shown that the models based on MEM performs better than ANOVA in interpreting raw time-series dataset into meaningful insights. © 2021 The Authors. IET Generation, Transmission & Distribution published by John Wiley & Sons Ltd on behalf of The Institution of Engineering and Technology
2.
Le, N T; Benjapolakul, W
Evaluation of contribution of PV array and inverter configurations to rooftop PV system energy yield using machine learning techniques Journal Article
In: Energies, vol. 12, no. 16, 2019, ISSN: 19961073, (cited By 6).
@article{Le2019,
title = {Evaluation of contribution of PV array and inverter configurations to rooftop PV system energy yield using machine learning techniques},
author = {N T Le and W Benjapolakul},
url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85071647803&doi=10.3390%2fen12163158&partnerID=40&md5=6c5f5c2afa277bc4e2ec418768da110d},
doi = {10.3390/en12163158},
issn = {19961073},
year = {2019},
date = {2019-01-01},
journal = {Energies},
volume = {12},
number = {16},
publisher = {MDPI AG},
abstract = {Rooftop photovoltaics (PV) systems are attracting residential customers due to their renewable energy contribution to houses and to green cities. However, customers also need a comprehensive understanding of system design configuration and the related energy return from the system in order to support their PV investment. In this study, the rooftop PV systems from many high-volume installed PV systems countries and regions were collected to evaluate the lifetime energy yield of these systems based on machine learning techniques. Then, we obtained an association between the lifetime energy yield and technical configuration details of PV such as rated solar panel power, number of panels, rated inverter power, and number of inverters. Our findings reveal that the variability of PV lifetime energy is partly explained by the difference in PV system configuration. Indeed, our machine learning model can explain approximately 31% (95% confidence interval: 29-38%) of the variant energy efficiency of the PV system, given the configuration and components of the PV system. Our study has contributed useful knowledge to support the planning and design of a rooftop PV system such as PV financial modeling and PV investment decision. © 2019 by the authors.},
note = {cited By 6},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Rooftop photovoltaics (PV) systems are attracting residential customers due to their renewable energy contribution to houses and to green cities. However, customers also need a comprehensive understanding of system design configuration and the related energy return from the system in order to support their PV investment. In this study, the rooftop PV systems from many high-volume installed PV systems countries and regions were collected to evaluate the lifetime energy yield of these systems based on machine learning techniques. Then, we obtained an association between the lifetime energy yield and technical configuration details of PV such as rated solar panel power, number of panels, rated inverter power, and number of inverters. Our findings reveal that the variability of PV lifetime energy is partly explained by the difference in PV system configuration. Indeed, our machine learning model can explain approximately 31% (95% confidence interval: 29-38%) of the variant energy efficiency of the PV system, given the configuration and components of the PV system. Our study has contributed useful knowledge to support the planning and design of a rooftop PV system such as PV financial modeling and PV investment decision. © 2019 by the authors.
3.
Le, N T; Benjapolakul, W
In: IEEE Access, vol. 7, pp. 175126-175134, 2019, ISSN: 21693536, (cited By 2).
@article{Le2019a,
title = {Comparative Electrical Energy Yield Performance of Micro-Inverter PV Systems Using a Machine Learning Approach Based on a Mixed-Effect Model of Real Datasets},
author = {N T Le and W Benjapolakul},
url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85076999407&doi=10.1109%2fACCESS.2019.2957381&partnerID=40&md5=5f1fdc8237b194fd4bb7051b7a31d68e},
doi = {10.1109/ACCESS.2019.2957381},
issn = {21693536},
year = {2019},
date = {2019-01-01},
journal = {IEEE Access},
volume = {7},
pages = {175126-175134},
publisher = {Institute of Electrical and Electronics Engineers Inc.},
abstract = {Long-term energy evaluation of PV systems that use micro-inverter configuration (micro-inverter PV systems) is currently unclear due to the lacking of sufficient longitudinal measurement data and appropriate analysis method. The poor knowledge about impact and aging of micro-inverter PV system affects the comprehension and accuracy of PV design and simulation tools. In this paper, we propose a machine learning approach based on the mixed-effect model to compare and evaluate the electrical energy yield of micro-inverter PV systems. The analyzed results using a 5-year period data of PV stations located at Concord, Massachusetts, USA showed that there is no significant difference in yearly electrical energy yield of micro-inverter PV systems under shading and non-shading condition. This finding has confirmed the advantage of micro-inverter PV system over the other PV types. In addition, our work is the first study that identified the average degradation rate of micro-inverter PV of 3% per year (95% confidence intervals: 2%-4.3%). Our findings in this study have extended substantially the comprehensive understanding of micro-inverter PV system. © 2013 IEEE.},
note = {cited By 2},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Long-term energy evaluation of PV systems that use micro-inverter configuration (micro-inverter PV systems) is currently unclear due to the lacking of sufficient longitudinal measurement data and appropriate analysis method. The poor knowledge about impact and aging of micro-inverter PV system affects the comprehension and accuracy of PV design and simulation tools. In this paper, we propose a machine learning approach based on the mixed-effect model to compare and evaluate the electrical energy yield of micro-inverter PV systems. The analyzed results using a 5-year period data of PV stations located at Concord, Massachusetts, USA showed that there is no significant difference in yearly electrical energy yield of micro-inverter PV systems under shading and non-shading condition. This finding has confirmed the advantage of micro-inverter PV system over the other PV types. In addition, our work is the first study that identified the average degradation rate of micro-inverter PV of 3% per year (95% confidence intervals: 2%-4.3%). Our findings in this study have extended substantially the comprehensive understanding of micro-inverter PV system. © 2013 IEEE.
4.
Le, N T; Benjapolakul, W
A Data Imputation Model in Phasor Measurement Units Based on Bagged Averaging of Multiple Linear Regression Journal Article
In: IEEE Access, vol. 6, pp. 39324-39333, 2018, ISSN: 21693536, (cited By 5).
@article{Le2018,
title = {A Data Imputation Model in Phasor Measurement Units Based on Bagged Averaging of Multiple Linear Regression},
author = {N T Le and W Benjapolakul},
url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85050234834&doi=10.1109%2fACCESS.2018.2856768&partnerID=40&md5=b5bc1ae6323b9d8d2f643488a5a315a3},
doi = {10.1109/ACCESS.2018.2856768},
issn = {21693536},
year = {2018},
date = {2018-01-01},
journal = {IEEE Access},
volume = {6},
pages = {39324-39333},
publisher = {Institute of Electrical and Electronics Engineers Inc.},
abstract = {Synchrophasor data from the phasor measurement unit (PMU) indicate the health of the electrical system. However, the PMU performance relies entirely on a supported communication network. The existing communication approaches do not guarantee the error-free channel for the PMU network. Meanwhile, the mean or median approaches are commonly used to impute the missing value. These methods, however, fail to recover some valuable frequency events. In this paper, we first proved the multiple linear regression features in many synchronized frequency data streams in the short-time window. Then, we proposed the Bagged Averaging of Multiple Linear Regression model, which handles and fulfills the missing values in synchronized frequency data measurement fast and efficiently. This technique was based on the ensemble learning by bootstrapping and averaging many multiple linear regressions to predict the missing values. Various experiments on the synchronized frequency measurement data from the Texas synchrophasor network have demonstrated the effectiveness of our proposed approach in recovering the missing frequency events. Our proposed approach guarantees the performance of real-time wide area monitoring system applications, such as frequency analysis or stability monitoring and trending. © 2013 IEEE.},
note = {cited By 5},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Synchrophasor data from the phasor measurement unit (PMU) indicate the health of the electrical system. However, the PMU performance relies entirely on a supported communication network. The existing communication approaches do not guarantee the error-free channel for the PMU network. Meanwhile, the mean or median approaches are commonly used to impute the missing value. These methods, however, fail to recover some valuable frequency events. In this paper, we first proved the multiple linear regression features in many synchronized frequency data streams in the short-time window. Then, we proposed the Bagged Averaging of Multiple Linear Regression model, which handles and fulfills the missing values in synchronized frequency data measurement fast and efficiently. This technique was based on the ensemble learning by bootstrapping and averaging many multiple linear regressions to predict the missing values. Various experiments on the synchronized frequency measurement data from the Texas synchrophasor network have demonstrated the effectiveness of our proposed approach in recovering the missing frequency events. Our proposed approach guarantees the performance of real-time wide area monitoring system applications, such as frequency analysis or stability monitoring and trending. © 2013 IEEE.
5.
Le, N T; Benjapolakul, W
Improving reliability of synchrophasor data gathering method using network coding technique Journal Article
In: Engineering Journal, vol. 22, no. 1, pp. 131-142, 2018, ISSN: 01258281, (cited By 0).
@article{Le2018a,
title = {Improving reliability of synchrophasor data gathering method using network coding technique},
author = {N T Le and W Benjapolakul},
url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85042660677&doi=10.4186%2fej.2018.22.1.131&partnerID=40&md5=4cc3ff3732bd5419c955744c21e2e671},
doi = {10.4186/ej.2018.22.1.131},
issn = {01258281},
year = {2018},
date = {2018-01-01},
journal = {Engineering Journal},
volume = {22},
number = {1},
pages = {131-142},
publisher = {Chulalongkorn University},
abstract = {We consider synchrophasor data gathering method over the network of Phasor Measurement Units (PMUs) for Wide Area Measurement System (WAMS) applications. Although this network plays an important role to monitor, protect and control distribution electric grid, the research efforts in efficient data collection method are lacking in the literature. In this paper, we represent a novel data gathering approach using Network Coding technique and develop a mathematic model to predict the PMUs network reliability using our proposed model. It allows the PMU nodes in network to perform linear combination of many packets in order to improve the packet delivering ratio at the collector. We demonstrate our proposed method using a distribution grid test case and evaluate the performance by using Monter Carlo simulation. The numerical results have verified the effectiveness of our proposed method. © 2018, Chulalongkorn University. All rights reserved.},
note = {cited By 0},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We consider synchrophasor data gathering method over the network of Phasor Measurement Units (PMUs) for Wide Area Measurement System (WAMS) applications. Although this network plays an important role to monitor, protect and control distribution electric grid, the research efforts in efficient data collection method are lacking in the literature. In this paper, we represent a novel data gathering approach using Network Coding technique and develop a mathematic model to predict the PMUs network reliability using our proposed model. It allows the PMU nodes in network to perform linear combination of many packets in order to improve the packet delivering ratio at the collector. We demonstrate our proposed method using a distribution grid test case and evaluate the performance by using Monter Carlo simulation. The numerical results have verified the effectiveness of our proposed method. © 2018, Chulalongkorn University. All rights reserved.
6.
Le, N T; Benjapolakul, W
QoS metrics modeling and analysis for neighborhood area network in smart grid applications Journal Article
In: IEEJ Transactions on Electrical and Electronic Engineering, vol. 12, pp. S79-S88, 2017, ISSN: 19314973, (cited By 1).
@article{Le2017,
title = {QoS metrics modeling and analysis for neighborhood area network in smart grid applications},
author = {N T Le and W Benjapolakul},
url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85020252818&doi=10.1002%2ftee.22442&partnerID=40&md5=9f1389bf9d2fc5556786ce994d0e24ba},
doi = {10.1002/tee.22442},
issn = {19314973},
year = {2017},
date = {2017-01-01},
journal = {IEEJ Transactions on Electrical and Electronic Engineering},
volume = {12},
pages = {S79-S88},
publisher = {John Wiley and Sons Inc.},
abstract = {Recently, planning and designing of smart-grid (SG) neighborhood area network (NAN) communication architecture has drawn wide attention of researchers. In order to establish an SG NAN scheme satisfying the requirement, a quality of service (QoS) metric is a critical demand. However, there are few studies on the implementation of an efficient QoS metric model. In this paper, we propose an innovative QoS metric model for SG NAN design. By exploring the natural characteristics of SG messages in many applications, we choose the reliability and latency of a message as the most important criteria and implement the QoS curve for evaluating the performance of any candidate communication scheme. In addition, we present the evaluation model for QoS metrics of multiple SG services in NAN. Compared to other existing QoS methods, our model is easy to use and helps to reduce the time and cost in the planning and designing of a NAN for SG. Simulation and analysis results indicate good agreement with our proposed QoS model. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.},
note = {cited By 1},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Recently, planning and designing of smart-grid (SG) neighborhood area network (NAN) communication architecture has drawn wide attention of researchers. In order to establish an SG NAN scheme satisfying the requirement, a quality of service (QoS) metric is a critical demand. However, there are few studies on the implementation of an efficient QoS metric model. In this paper, we propose an innovative QoS metric model for SG NAN design. By exploring the natural characteristics of SG messages in many applications, we choose the reliability and latency of a message as the most important criteria and implement the QoS curve for evaluating the performance of any candidate communication scheme. In addition, we present the evaluation model for QoS metrics of multiple SG services in NAN. Compared to other existing QoS methods, our model is easy to use and helps to reduce the time and cost in the planning and designing of a NAN for SG. Simulation and analysis results indicate good agreement with our proposed QoS model. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
7.
Tan-a-Ram, S; Benjapolakul, W
Achievable rate region for the two-user Gaussian X channel with limited receiver cooperation: General case Journal Article
In: IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, vol. E100A, no. 3, pp. 822-831, 2017, ISSN: 09168508, (cited By 1).
@article{TanaRam2017,
title = {Achievable rate region for the two-user Gaussian X channel with limited receiver cooperation: General case},
author = {S Tan-a-Ram and W Benjapolakul},
url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85016206557&doi=10.1587%2ftransfun.E100.A.822&partnerID=40&md5=4ca9821ce0b5a4c8ffb98679a58e5dd5},
doi = {10.1587/transfun.E100.A.822},
issn = {09168508},
year = {2017},
date = {2017-01-01},
journal = {IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences},
volume = {E100A},
number = {3},
pages = {822-831},
publisher = {Maruzen Co., Ltd.},
abstract = {In this paper, we propose to use a strategy for the two-user Gaussian X channel with limited receiver cooperation in the general case consisting of two parts: 1) the transmission scheme where the superposition coding is used and 2) the cooperative protocol where the two-round strategy based on quantize-map-and-forward (QMF) is employed. We image that a Gaussian X channel can be considered as a superposition of two Gaussian interference channels based on grouping of the sent messages from each transmitter to the corresponding receivers. Finally, we give an achievable rate region for the general case of this channel. © 2017 The Institute of Electronics, Information and Communication Engineers.},
note = {cited By 1},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
In this paper, we propose to use a strategy for the two-user Gaussian X channel with limited receiver cooperation in the general case consisting of two parts: 1) the transmission scheme where the superposition coding is used and 2) the cooperative protocol where the two-round strategy based on quantize-map-and-forward (QMF) is employed. We image that a Gaussian X channel can be considered as a superposition of two Gaussian interference channels based on grouping of the sent messages from each transmitter to the corresponding receivers. Finally, we give an achievable rate region for the general case of this channel. © 2017 The Institute of Electronics, Information and Communication Engineers.
8.
Trung, H D; Benjapolakul, W; Araki, K
Capacity analysis of MIMO rayleigh channel with spatial fading correlation Journal Article
In: IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, vol. E91-A, no. 10, pp. 2818-2826, 2008, ISSN: 09168508, (cited By 2).
@article{Trung2008,
title = {Capacity analysis of MIMO rayleigh channel with spatial fading correlation},
author = {H D Trung and W Benjapolakul and K Araki},
url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-77953432687&doi=10.1093%2fietfec%2fe91-a.10.2818&partnerID=40&md5=949813f4317506ff36b4d055ec9bf424},
doi = {10.1093/ietfec/e91-a.10.2818},
issn = {09168508},
year = {2008},
date = {2008-01-01},
journal = {IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences},
volume = {E91-A},
number = {10},
pages = {2818-2826},
publisher = {Institute of Electronics, Information and Communication, Engineers, IEICE},
abstract = {MIMO (Multiple Input Multiple Output) communications systems equipped with array antennas at both the transmitter and receiver sides are a promising scheme to realize higher rate and/or reliable data transmission. In this paper, capacity analysis of MIMO Rayleigh channel with spatial correlation at the receiver of multipath taken into account is presented. In general, a model configuration of local scattering around a mobile station in MIMO environment is carried out by simulation to examine spatial correlation coefficients. Based on statistical properties of the eigenvalues of correlated complex random Wishart matrices, the exact closed-form expressions of distribution of the eigenvalues are investigated. Then, the general closed-form evaluation of integral form is proposed based on Meijer's G-function. The results demonstrate that the ergodic capacities are improved by increasing the number of the antennas and the SNR's. Compared with i.i.d. (independent identically distributed) Rayleigh channel, the incremental improvement of correlated Rayleigh channel is reduced by spatial fading correlation. The analytical results validated by Monte-Carlo simulations show a good agreement. Copyright © 2008 The Institute of Electronics, Information and Communication Engineers.},
note = {cited By 2},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
MIMO (Multiple Input Multiple Output) communications systems equipped with array antennas at both the transmitter and receiver sides are a promising scheme to realize higher rate and/or reliable data transmission. In this paper, capacity analysis of MIMO Rayleigh channel with spatial correlation at the receiver of multipath taken into account is presented. In general, a model configuration of local scattering around a mobile station in MIMO environment is carried out by simulation to examine spatial correlation coefficients. Based on statistical properties of the eigenvalues of correlated complex random Wishart matrices, the exact closed-form expressions of distribution of the eigenvalues are investigated. Then, the general closed-form evaluation of integral form is proposed based on Meijer's G-function. The results demonstrate that the ergodic capacities are improved by increasing the number of the antennas and the SNR's. Compared with i.i.d. (independent identically distributed) Rayleigh channel, the incremental improvement of correlated Rayleigh channel is reduced by spatial fading correlation. The analytical results validated by Monte-Carlo simulations show a good agreement. Copyright © 2008 The Institute of Electronics, Information and Communication Engineers.
9.
Trung, H D; Benjapolakul, W; Duc, P M
Performance evaluation and comparison of different ad hoc routing protocols Journal Article
In: Computer Communications, vol. 30, no. 11-12, pp. 2478-2496, 2007, ISSN: 01403664, (cited By 47).
@article{Trung2007a,
title = {Performance evaluation and comparison of different ad hoc routing protocols},
author = {H D Trung and W Benjapolakul and P M Duc},
url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-34548029342&doi=10.1016%2fj.comcom.2007.04.007&partnerID=40&md5=a61f98e782f1da85b7f862dd612c8615},
doi = {10.1016/j.comcom.2007.04.007},
issn = {01403664},
year = {2007},
date = {2007-01-01},
journal = {Computer Communications},
volume = {30},
number = {11-12},
pages = {2478-2496},
abstract = {A Mobile Ad Hoc Network (MANET) is a dynamic wireless network that can be formed without the need for any pre-existing infrastructure in which each node can act as a router. One of the main challenges MANET is the design of robust routing algorithms that adapt to the frequent and randomly changing network topology. In recent years, a variety of routing protocols have been proposed and several of these have been already extensively simulated or implemented as well. In this paper, we compare the performance of different protocols for ad hoc networks - Ad Hoc On-Demand Distance Vector Routing (AODV), Location-Aided Routing (LAR), Ad Hoc On-Demand Multipath Distant Vector (AOMDV) routing and Location-Aided Multipath Routing (LAMR). Therefore, we propose a location multipath routing-based method by extension of LAR. A simulation model with MAC and physical layer models is used to study interlayer interactions and their performance implications. The performance differentials are analyzed using varying network load and mobility. Simulations demonstrate the performance benefits of our proposal LAMR over LAR and AODV in most movement scenarios. AOMDV uses higher bandwidth than LAMR due to more frequent flooding of control packets. This paper directly discusses the performance evaluation and comparison of four routing protocols. Moreover, we also discuss the solutions for security in a MANET briefly, and address discussion and directions for future research. © 2007 Elsevier B.V. All rights reserved.},
note = {cited By 47},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
A Mobile Ad Hoc Network (MANET) is a dynamic wireless network that can be formed without the need for any pre-existing infrastructure in which each node can act as a router. One of the main challenges MANET is the design of robust routing algorithms that adapt to the frequent and randomly changing network topology. In recent years, a variety of routing protocols have been proposed and several of these have been already extensively simulated or implemented as well. In this paper, we compare the performance of different protocols for ad hoc networks - Ad Hoc On-Demand Distance Vector Routing (AODV), Location-Aided Routing (LAR), Ad Hoc On-Demand Multipath Distant Vector (AOMDV) routing and Location-Aided Multipath Routing (LAMR). Therefore, we propose a location multipath routing-based method by extension of LAR. A simulation model with MAC and physical layer models is used to study interlayer interactions and their performance implications. The performance differentials are analyzed using varying network load and mobility. Simulations demonstrate the performance benefits of our proposal LAMR over LAR and AODV in most movement scenarios. AOMDV uses higher bandwidth than LAMR due to more frequent flooding of control packets. This paper directly discusses the performance evaluation and comparison of four routing protocols. Moreover, we also discuss the solutions for security in a MANET briefly, and address discussion and directions for future research. © 2007 Elsevier B.V. All rights reserved.
10.
Virapanicharoen, J; Benjapolakul, W; Araki, K
A Game theoretic framework for fair-efficient threshold parameters selection in call admission control for CDMA mobile multimedia systems Journal Article
In: IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, vol. E90-A, no. 7, pp. 1280-1291, 2007, ISSN: 09168508, (cited By 0).
@article{Virapanicharoen2007,
title = {A Game theoretic framework for fair-efficient threshold parameters selection in call admission control for CDMA mobile multimedia systems},
author = {J Virapanicharoen and W Benjapolakul and K Araki},
url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-68249143361&doi=10.1093%2fietfec%2fe90-a.7.1280&partnerID=40&md5=eee86b8532df32f86a95fa4662a567bc},
doi = {10.1093/ietfec/e90-a.7.1280},
issn = {09168508},
year = {2007},
date = {2007-01-01},
journal = {IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences},
volume = {E90-A},
number = {7},
pages = {1280-1291},
publisher = {Institute of Electronics, Information and Communication, Engineers, IEICE},
abstract = {While efficient use of network resources is an important control objective of call admission control (CAC), the issue of fairness among services should also be taken into account. Game theory provides a suitable framework for formulating such fair and efficient CAC problem. Thus, in this paper, a game theoretic framework for selecting fair-efficient threshold parameters of CAC for the asymmetrical traffic case in CDMA mobile multimedia systems is proposed. For the cooperative game, the arbitration schemes for the interpersonal comparisons of utility and the bargaining problem, including the Nash, Raiffa, and modified Thomson solutions, are investigated. Furthermore, since CAC should be simple and flexible to provide a fast response to diverse QoS call requests during a connection setup, this paper also applies the concept of load factor to the previous Jeon and Jeong's CAC scheme and proposes an approximation approach to reduce the computational complexity (proposed throughput-based CAC scheme). From the numerical results, the proposed throughput-based CAC scheme shows a comparable performance to the previous Jeon and Jeong's CAC scheme while achieving lower computational complexity. All the solutions attain the fairness by satisfying their different fairness senses and efficiency by the Pareto optimality. © 2007 The Institute of Electronics, Information and Communication Engineers.},
note = {cited By 0},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
While efficient use of network resources is an important control objective of call admission control (CAC), the issue of fairness among services should also be taken into account. Game theory provides a suitable framework for formulating such fair and efficient CAC problem. Thus, in this paper, a game theoretic framework for selecting fair-efficient threshold parameters of CAC for the asymmetrical traffic case in CDMA mobile multimedia systems is proposed. For the cooperative game, the arbitration schemes for the interpersonal comparisons of utility and the bargaining problem, including the Nash, Raiffa, and modified Thomson solutions, are investigated. Furthermore, since CAC should be simple and flexible to provide a fast response to diverse QoS call requests during a connection setup, this paper also applies the concept of load factor to the previous Jeon and Jeong's CAC scheme and proposes an approximation approach to reduce the computational complexity (proposed throughput-based CAC scheme). From the numerical results, the proposed throughput-based CAC scheme shows a comparable performance to the previous Jeon and Jeong's CAC scheme while achieving lower computational complexity. All the solutions attain the fairness by satisfying their different fairness senses and efficiency by the Pareto optimality. © 2007 The Institute of Electronics, Information and Communication Engineers.
11.
Chiratana, K; Benjapolakul, W
Improvement of paging extensions in mobile Internet protocol based on post registration Journal Article
In: IEICE Transactions on Information and Systems, vol. E89-D, no. 12, pp. 2848-2855, 2006, ISSN: 09168532, (cited By 0).
@article{Chiratana2006,
title = {Improvement of paging extensions in mobile Internet protocol based on post registration},
author = {K Chiratana and W Benjapolakul},
url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-33845569869&doi=10.1093%2fietisy%2fe89-d.12.2848&partnerID=40&md5=9d6fcde4a1652d234ab844ea5d4065c6},
doi = {10.1093/ietisy/e89-d.12.2848},
issn = {09168532},
year = {2006},
date = {2006-01-01},
journal = {IEICE Transactions on Information and Systems},
volume = {E89-D},
number = {12},
pages = {2848-2855},
publisher = {Institute of Electronics, Information and Communication, Engineers, IEICE},
abstract = {Paging extensions for Mobile Internet Protocol (P-MIP) decreases only the number of registration, but it does not much improve the method of registration, which still gives rise to a lot of lost packets and long handoff latency, and may also waste the data buffering and time during registration. In the active state, P-MIP behaves in the same way as Mobile Internet Protocol (MIP), thus, in this state, the packet loss rate of P-MIP is the same as that of MIP. However, the packet loss rate of P-MIP is lower than that of MIP, when changing from idle state to active state, because P-MIP buffers packets at the registered FA. We propose an improvement method for the registration delay, while the mobile node is entering the active state to decrease the mobile node waiting time for data packets. The proposed method can reduce the requirement of data buffering and also improve the method of registration to decrease lost packets and handoff latency when the mobile node moves across the cell in the same paging area during active state. Copyright © 2006 The Institute of Electronics, Information and Communication Engineers.},
note = {cited By 0},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Paging extensions for Mobile Internet Protocol (P-MIP) decreases only the number of registration, but it does not much improve the method of registration, which still gives rise to a lot of lost packets and long handoff latency, and may also waste the data buffering and time during registration. In the active state, P-MIP behaves in the same way as Mobile Internet Protocol (MIP), thus, in this state, the packet loss rate of P-MIP is the same as that of MIP. However, the packet loss rate of P-MIP is lower than that of MIP, when changing from idle state to active state, because P-MIP buffers packets at the registered FA. We propose an improvement method for the registration delay, while the mobile node is entering the active state to decrease the mobile node waiting time for data packets. The proposed method can reduce the requirement of data buffering and also improve the method of registration to decrease lost packets and handoff latency when the mobile node moves across the cell in the same paging area during active state. Copyright © 2006 The Institute of Electronics, Information and Communication Engineers.
12.
Virapanicharoen, J; Benjapolakul, W
In: IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, vol. E88-A, no. 7, pp. 1869-1880, 2005, ISSN: 09168508, (cited By 4).
@article{Virapanicharoen2005b,
title = {Fair-efficient guard bandwidth coefficients selection in call admission control for mobile multimedia communications using framework of game theory},
author = {J Virapanicharoen and W Benjapolakul},
url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-26044480426&doi=10.1093%2fietfec%2fe88-a.7.1869&partnerID=40&md5=c17c953e08f4e92037440da2118d757e},
doi = {10.1093/ietfec/e88-a.7.1869},
issn = {09168508},
year = {2005},
date = {2005-01-01},
journal = {IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences},
volume = {E88-A},
number = {7},
pages = {1869-1880},
publisher = {Institute of Electronics, Information and Communication, Engineers, IEICE},
abstract = {Call admission control (CAC) plays a significant role in providing the efficient use of the limited bandwidth and the desired quality-of-service (QoS) in mobile multimedia communications. As efficiency is an important performance issue for CAC in the mobile networks with multimedia services, the concept of fairness among services should also be considered. Game theory provides an appropriate framework for formulating such fair and efficient CAC problem. Thus, in this paper, a framework based on game theory (both of noncooperative and cooperative games) is proposed to select fair-efficient guard bandwidth coefficients of the CAC scheme for the asymmetrical traffic case in mobile multimedia communications. The proposed game theoretic framework provides fairness and efficiency in the aspects of bandwidth utilization and QoS for multiple classes of traffic, and also guarantees the proper priority mechanism. Call classes are viewed as the players of a game. Utility function of the player is defined to be of two types, the bandwidth utilization and the weighted sum of new call accepting probability and handoff succeeding probability. The numerical results show that, for both types of the utility function, there is a unique equilibrium point of the noncooperative game for any given offered load. For the cooperative game, the arbitration schemes for the interpersonal comparisons of utility and the bargaining problem are investigated. The results also indicate that, for both types of the utility function, the Nash solution with the origin (0,0) as the starting point of the bargaining problem can achieve higher total utility than the previous CAC scheme while at the same time providing fairness by satisfying a set of fairness axioms. Since the Nash solution is determined from the domain of the Pareto boundary, the way to generate the Pareto boundary is also provided. Therefore, the Nash solution can be obtained easily. Copyright © 2005 The Institute of Electronics, Information and Communication Engineers.},
note = {cited By 4},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Call admission control (CAC) plays a significant role in providing the efficient use of the limited bandwidth and the desired quality-of-service (QoS) in mobile multimedia communications. As efficiency is an important performance issue for CAC in the mobile networks with multimedia services, the concept of fairness among services should also be considered. Game theory provides an appropriate framework for formulating such fair and efficient CAC problem. Thus, in this paper, a framework based on game theory (both of noncooperative and cooperative games) is proposed to select fair-efficient guard bandwidth coefficients of the CAC scheme for the asymmetrical traffic case in mobile multimedia communications. The proposed game theoretic framework provides fairness and efficiency in the aspects of bandwidth utilization and QoS for multiple classes of traffic, and also guarantees the proper priority mechanism. Call classes are viewed as the players of a game. Utility function of the player is defined to be of two types, the bandwidth utilization and the weighted sum of new call accepting probability and handoff succeeding probability. The numerical results show that, for both types of the utility function, there is a unique equilibrium point of the noncooperative game for any given offered load. For the cooperative game, the arbitration schemes for the interpersonal comparisons of utility and the bargaining problem are investigated. The results also indicate that, for both types of the utility function, the Nash solution with the origin (0,0) as the starting point of the bargaining problem can achieve higher total utility than the previous CAC scheme while at the same time providing fairness by satisfying a set of fairness axioms. Since the Nash solution is determined from the domain of the Pareto boundary, the way to generate the Pareto boundary is also provided. Therefore, the Nash solution can be obtained easily. Copyright © 2005 The Institute of Electronics, Information and Communication Engineers.
13.
Khemapatapan, C; Benjapolakul, W; Araki, K
QPSK impulse signal transmission for ultra wide band communication systems in multipath channel environments Journal Article
In: IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, vol. E88-A, no. 11, pp. 3100-3108, 2005, ISSN: 09168508, (cited By 2).
@article{Khemapatapan2005a,
title = {QPSK impulse signal transmission for ultra wide band communication systems in multipath channel environments},
author = {C Khemapatapan and W Benjapolakul and K Araki},
url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-29144453847&doi=10.1093%2fietfec%2fe88-a.11.3100&partnerID=40&md5=5f7232cdfb28d246ebbfc77a1d296bdb},
doi = {10.1093/ietfec/e88-a.11.3100},
issn = {09168508},
year = {2005},
date = {2005-01-01},
journal = {IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences},
volume = {E88-A},
number = {11},
pages = {3100-3108},
publisher = {Institute of Electronics, Information and Communication, Engineers, IEICE},
abstract = {In this paper, three new ultra wideband (UWB) communication systems with quadrature-phase shift keying (QPSK) impulse modulation are proposed. First, direct-sequence (DS) multiple-access scheme is applied. The second proposed system is based on time-hopping (TH) multiple-access scheme. The last proposed system applies TH multiple-access scheme with QPSK impulse modulation and pulse position modulation (PPM). The conventional UWB communications as TH scheme with PPM modulation and DS scheme with binary-phase shift keying (BPSK) are used to compare. The simulation results show that all proposed UWB communication systems can provide obviously better performances compared with the conventional TH-PPM and DS-BPSK UWB communication systems. The comparisons in aspects of transmission bit rate and the number of users are also investigated. Copyright © 2005 The Institute of Electronics, Information and Communication Engineers.},
note = {cited By 2},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
In this paper, three new ultra wideband (UWB) communication systems with quadrature-phase shift keying (QPSK) impulse modulation are proposed. First, direct-sequence (DS) multiple-access scheme is applied. The second proposed system is based on time-hopping (TH) multiple-access scheme. The last proposed system applies TH multiple-access scheme with QPSK impulse modulation and pulse position modulation (PPM). The conventional UWB communications as TH scheme with PPM modulation and DS scheme with binary-phase shift keying (BPSK) are used to compare. The simulation results show that all proposed UWB communication systems can provide obviously better performances compared with the conventional TH-PPM and DS-BPSK UWB communication systems. The comparisons in aspects of transmission bit rate and the number of users are also investigated. Copyright © 2005 The Institute of Electronics, Information and Communication Engineers.
14.
Homnan, B; Benjapolakul, W
Application of fuzzy inference to CDMA soft handoff in mobile communication systems Journal Article
In: Fuzzy Sets and Systems, vol. 144, no. 2, pp. 345-363, 2004, ISSN: 01650114, (cited By 4).
@article{Homnan2004a,
title = {Application of fuzzy inference to CDMA soft handoff in mobile communication systems},
author = {B Homnan and W Benjapolakul},
url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-2142771316&doi=10.1016%2fS0165-0114%2803%2900206-9&partnerID=40&md5=72adbe1fa07ef53366eb1c6212221164},
doi = {10.1016/S0165-0114(03)00206-9},
issn = {01650114},
year = {2004},
date = {2004-01-01},
journal = {Fuzzy Sets and Systems},
volume = {144},
number = {2},
pages = {345-363},
abstract = {The adaptation of soft handoff thresholds in direct sequence code division multiple access mobile communication systems using fuzzy inference is described. The soft handoff thresholds obtained from the proposed method are considered to depend on two inputs: the number of remaining traffic channels and the number of base stations connected to each mobile station. By evaluation of performance indicators, the fuzzy inference tends to give higher performance than the conventional soft handoff especially in trunk-resource efficiency, call blocking, and carried traffic. Among fuzzy inference schemes considered, fuzzy inference with defuzzification using weighted average formula and fuzzification using bell membership function of the number of connected base stations and triangular membership function of the number of remaining traffic channels is the most compromised scheme when call blocking is not concerned. When call blocking is the serious indicator, fuzzy inference with defuzzification using weighted average formula and fuzzification using triangular membership function of both inputs should be selected. Regarding computational complexity, fuzzy inference with defuzzification using weighted average formula is the simplest. © 2003 Elsevier B.V. All rights reserved.},
note = {cited By 4},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The adaptation of soft handoff thresholds in direct sequence code division multiple access mobile communication systems using fuzzy inference is described. The soft handoff thresholds obtained from the proposed method are considered to depend on two inputs: the number of remaining traffic channels and the number of base stations connected to each mobile station. By evaluation of performance indicators, the fuzzy inference tends to give higher performance than the conventional soft handoff especially in trunk-resource efficiency, call blocking, and carried traffic. Among fuzzy inference schemes considered, fuzzy inference with defuzzification using weighted average formula and fuzzification using bell membership function of the number of connected base stations and triangular membership function of the number of remaining traffic channels is the most compromised scheme when call blocking is not concerned. When call blocking is the serious indicator, fuzzy inference with defuzzification using weighted average formula and fuzzification using triangular membership function of both inputs should be selected. Regarding computational complexity, fuzzy inference with defuzzification using weighted average formula is the simplest. © 2003 Elsevier B.V. All rights reserved.
15.
Homnan, B; Benjapolakul, W
QoS-controlling soft handoff based on simple step control and a fuzzy inference system with the gradient descent method Journal Article
In: IEEE Transactions on Vehicular Technology, vol. 53, no. 3, pp. 820-834, 2004, ISSN: 00189545, (cited By 7).
@article{Homnan2004b,
title = {QoS-controlling soft handoff based on simple step control and a fuzzy inference system with the gradient descent method},
author = {B Homnan and W Benjapolakul},
url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-2942628321&doi=10.1109%2fTVT.2004.825755&partnerID=40&md5=d25454a8906108dbf027c8bcaa06736d},
doi = {10.1109/TVT.2004.825755},
issn = {00189545},
year = {2004},
date = {2004-01-01},
journal = {IEEE Transactions on Vehicular Technology},
volume = {53},
number = {3},
pages = {820-834},
abstract = {Quality of service (QoS) is an important criterion considered in mobile communication systems since it directly affects system users in terms of both call blocking and call quality. This paper aims to control the QoS in code-division multiple-access mobile communication systems by proposing two new practical methods applied to the conventional soft handoff (SHO) process based on a simple step-control method and a human-oriented information method of fuzzy inference system with classical mathematics of the gradient descent method. The output parameters selected to be controlled by adapting SHO thresholds are the trunk-resource efficiency (TRE), the forward link's average energy per bit to the interference plus noise power spectral density ratio (Eb/Io), and the outage probability (Pout). TRE is concerned with call blocking while Eb/Io is an indicator of the call quality. The number of the remaining channels of serving base station (CHrm), the moving average number of pilots in active set of any mobile station (noBS), and Eb/Io is or are selected to be one, two, or three of the control plant inputs, depending on the method applied. QoS-controlling SHO (TRE- and Eb/Io-controlling SHO) can improve the system performance. However, which method that will be selected for use is according to the environment and the requirement of the system operator and/or users.},
note = {cited By 7},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Quality of service (QoS) is an important criterion considered in mobile communication systems since it directly affects system users in terms of both call blocking and call quality. This paper aims to control the QoS in code-division multiple-access mobile communication systems by proposing two new practical methods applied to the conventional soft handoff (SHO) process based on a simple step-control method and a human-oriented information method of fuzzy inference system with classical mathematics of the gradient descent method. The output parameters selected to be controlled by adapting SHO thresholds are the trunk-resource efficiency (TRE), the forward link's average energy per bit to the interference plus noise power spectral density ratio (Eb/Io), and the outage probability (Pout). TRE is concerned with call blocking while Eb/Io is an indicator of the call quality. The number of the remaining channels of serving base station (CHrm), the moving average number of pilots in active set of any mobile station (noBS), and Eb/Io is or are selected to be one, two, or three of the control plant inputs, depending on the method applied. QoS-controlling SHO (TRE- and Eb/Io-controlling SHO) can improve the system performance. However, which method that will be selected for use is according to the environment and the requirement of the system operator and/or users.
16.
Homnan, B; Benjapolakul, W; Tsukamoto, K; Komaki, S
The effects of varying soft handoff thresholds in cellular CDMA system Journal Article
In: IEICE Transactions on Communications, vol. E87-B, no. 4, pp. 807-815, 2004, ISSN: 09168516, (cited By 3).
@article{Homnan2004c,
title = {The effects of varying soft handoff thresholds in cellular CDMA system},
author = {B Homnan and W Benjapolakul and K Tsukamoto and S Komaki},
url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-2342635249&partnerID=40&md5=141fe60e0fb36253066fbb1d3584040d},
issn = {09168516},
year = {2004},
date = {2004-01-01},
journal = {IEICE Transactions on Communications},
volume = {E87-B},
number = {4},
pages = {807-815},
publisher = {Institute of Electronics, Information and Communication, Engineers, IEICE},
abstract = {In order to benefit from the advantages of soft handoff (SHO), it is important that the SHO parameters (the SHO thresholds; T _ADD and T _DROP are well assigned. T _ADD is the threshold used for triggering a pilot with high strength to be added to the Active Set (AS) list. The AS means the pilots associated with the forward traffic channels assigned to mobile station. In contrast, T _DROP is the threshold used for triggering a pilot with low strength to be dropped from the AS list. This paper analyzes the effects of varying SHO thresholds in a cellular code division multiple access (CDMA) system on the blocking probability based on traffic load and geometrical distances in hexagonal layout of base stations (BSs). In addition, the previously proposed traffic load equation [1] is applied to the proposed SHO model for balancing the numbers of new and handoff calls on the forward link capacity in case of uniform traffic load. The results show that the blocking probability is more sensitive to T _DROP than to T _ADD variations.},
note = {cited By 3},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
In order to benefit from the advantages of soft handoff (SHO), it is important that the SHO parameters (the SHO thresholds; T _ADD and T _DROP are well assigned. T _ADD is the threshold used for triggering a pilot with high strength to be added to the Active Set (AS) list. The AS means the pilots associated with the forward traffic channels assigned to mobile station. In contrast, T _DROP is the threshold used for triggering a pilot with low strength to be dropped from the AS list. This paper analyzes the effects of varying SHO thresholds in a cellular code division multiple access (CDMA) system on the blocking probability based on traffic load and geometrical distances in hexagonal layout of base stations (BSs). In addition, the previously proposed traffic load equation [1] is applied to the proposed SHO model for balancing the numbers of new and handoff calls on the forward link capacity in case of uniform traffic load. The results show that the blocking probability is more sensitive to T _DROP than to T _ADD variations.
17.
Homnan, B; Benjapolakul, W
Adaptation of CDMA Soft Handoff Thresholds Using Fuzzy Inference System Journal Article
In: Wireless Personal Communications, vol. 26, no. 4, pp. 325-345, 2003, ISSN: 09296212, (cited By 0).
@article{Homnan2003,
title = {Adaptation of CDMA Soft Handoff Thresholds Using Fuzzy Inference System},
author = {B Homnan and W Benjapolakul},
url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-0141924261&doi=10.1023%2fA%3a1025684710889&partnerID=40&md5=93e71322ac8630804e9b25e826497ede},
doi = {10.1023/A:1025684710889},
issn = {09296212},
year = {2003},
date = {2003-01-01},
journal = {Wireless Personal Communications},
volume = {26},
number = {4},
pages = {325-345},
abstract = {This paper proposes a new procedure to adjust soft handoff thresholds dynamically by using fuzzy inference system. This algorithm is compared with IS-95A and IS-95B/cdma2000 soft handoffs. The aims are to increase the thresholds at high traffic loads in order to release the traffic channel for supporting more carried traffic, and to decrease the thresholds at low traffic loads in order to give high quality of traffic channel. The inputs of the proposed algorithm are the number of remaining channels of each base station and the number of active pilots in active set of each mobile station. The output is the new soft handoff thresholds. In the fuzzy inference module, the triangular membership function, the max-min composition, and the weighted average formula defuzzification are selected. By comparison of all performance indicators among three algorithms, soft handoff using fuzzy inference tends to give higher performance than those of IS-95A and IS-95B/cdma2000 soft handoffs at high traffic loads and at lower soft handoff thresholds while the quality of traffic channel is still acceptable. Moreover, the wider soft handoff window size of the proposed algorithm gives high carried traffic and low blocking probability but lower quality of traffic channels. In addition, the adaptive soft handoff window size can give lower blocking probability while still keep acceptable quality of traffic channels.},
note = {cited By 0},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
This paper proposes a new procedure to adjust soft handoff thresholds dynamically by using fuzzy inference system. This algorithm is compared with IS-95A and IS-95B/cdma2000 soft handoffs. The aims are to increase the thresholds at high traffic loads in order to release the traffic channel for supporting more carried traffic, and to decrease the thresholds at low traffic loads in order to give high quality of traffic channel. The inputs of the proposed algorithm are the number of remaining channels of each base station and the number of active pilots in active set of each mobile station. The output is the new soft handoff thresholds. In the fuzzy inference module, the triangular membership function, the max-min composition, and the weighted average formula defuzzification are selected. By comparison of all performance indicators among three algorithms, soft handoff using fuzzy inference tends to give higher performance than those of IS-95A and IS-95B/cdma2000 soft handoffs at high traffic loads and at lower soft handoff thresholds while the quality of traffic channel is still acceptable. Moreover, the wider soft handoff window size of the proposed algorithm gives high carried traffic and low blocking probability but lower quality of traffic channels. In addition, the adaptive soft handoff window size can give lower blocking probability while still keep acceptable quality of traffic channels.
18.
Krachodnok, P; Benjapolakul, W
Buffer management for tcp over gfr service in an atm network Journal Article
In: IEEE International Conference on Networks, ICON, pp. 302-307, 2001, ISSN: 15566463, (cited By 1).
@article{Krachodnok2001,
title = {Buffer management for tcp over gfr service in an atm network},
author = {P Krachodnok and W Benjapolakul},
url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-78651563055&doi=10.1109%2fICON.2001.962358&partnerID=40&md5=2952a2d1fb00bfafe07ed0c995cf0b16},
doi = {10.1109/ICON.2001.962358},
issn = {15566463},
year = {2001},
date = {2001-01-01},
journal = {IEEE International Conference on Networks, ICON},
pages = {302-307},
abstract = {Buffer management plays an important role in guaranteed frame rate (GFR) service in an asynchronous transfer mode (ATM) network. Buffer management algorithms are used to allocate appropriate space in a switch buffer for untagged GFR cells to fulfill the guaranteed minimum cell rate (MCR). Two main goals of buffer management algorithms are high throughput and high fairness index. However, these goals are compromised, that is the higher throughput gives the lower fairness index. This paper proposes a new buffer management algorithm called BADT (buffer allocation with dynamic threshold) algorithm, which uses dynamic threshold techniques for the fairness index improvement. The performance comparison of the previously proposed algorithms is shown. The simulation results show that the BADT algorithm gives the highest fairness index and still gives acceptably high throughput compared to the previously proposed algorithms. © 2001 IEEE.},
note = {cited By 1},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Buffer management plays an important role in guaranteed frame rate (GFR) service in an asynchronous transfer mode (ATM) network. Buffer management algorithms are used to allocate appropriate space in a switch buffer for untagged GFR cells to fulfill the guaranteed minimum cell rate (MCR). Two main goals of buffer management algorithms are high throughput and high fairness index. However, these goals are compromised, that is the higher throughput gives the lower fairness index. This paper proposes a new buffer management algorithm called BADT (buffer allocation with dynamic threshold) algorithm, which uses dynamic threshold techniques for the fairness index improvement. The performance comparison of the previously proposed algorithms is shown. The simulation results show that the BADT algorithm gives the highest fairness index and still gives acceptably high throughput compared to the previously proposed algorithms. © 2001 IEEE.
19.
Tanterdtid, S; Benjapolakul, W; Steanputtanagul, W
Optimizing a single-hop virtual path system using a genetic algorithm Journal Article
In: International Journal of Computers and Applications, vol. 22, no. 2, pp. 62-72, 2000, ISSN: 1206212X, (cited By 0).
@article{Tanterdtid2000,
title = {Optimizing a single-hop virtual path system using a genetic algorithm},
author = {S Tanterdtid and W Benjapolakul and W Steanputtanagul},
url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-0034476678&doi=10.1080%2f1206212X.2000.11441602&partnerID=40&md5=5312a0ae94fc4ca8fc79552c39638c17},
doi = {10.1080/1206212X.2000.11441602},
issn = {1206212X},
year = {2000},
date = {2000-01-01},
journal = {International Journal of Computers and Applications},
volume = {22},
number = {2},
pages = {62-72},
publisher = {IASTED, Calgary},
abstract = {The virtual paths (VPs) system has been proposed as a key technique in order to utilize the asynchronous transfer mode (ATM)-based transport network. This article addresses the problem of how to assign the VPs system-based ATM network. This problem can be classified as a combinatorial and NP-hard complete optimization problem in which we want to minimize the designed VPs system assignment objective subject to the network constraints. A genetic algorithm (GA) is introduced as a new approach to solve this problem. Using the ON-OFF source and the fluid flow concepts, the equivalent bandwidth is formulated as the effective transmission rate of each heterogeneous traffic VP which guarantees both quality of service (QoS) in the cell level and the grade of service (GoS) in the connection level. The multi-objective function which comprises the average blocking rates (ABR) and the average packet delay (APD) is regarded as our designed VPs system assignment objective. A new coding technique in which each chromosome represents one of the VP system configurations and is also created associating with the designing delay bound of each VP is proposed. The concept of past solution is modified to suit the dynamic VPs system control technique that requires fast calculation speed. Numerical results show that by using our proposed method, it gives a good solution. Faster calculation speed than offered in previous literature, can be obtained by using our new coding technique. Moreover, comparative studies between this Genetic Algorithm (GA) application and conventional exhaustive search method which has been used as a reference algorithm to evaluate the quality of solution for global optimum provides very similar results.},
note = {cited By 0},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The virtual paths (VPs) system has been proposed as a key technique in order to utilize the asynchronous transfer mode (ATM)-based transport network. This article addresses the problem of how to assign the VPs system-based ATM network. This problem can be classified as a combinatorial and NP-hard complete optimization problem in which we want to minimize the designed VPs system assignment objective subject to the network constraints. A genetic algorithm (GA) is introduced as a new approach to solve this problem. Using the ON-OFF source and the fluid flow concepts, the equivalent bandwidth is formulated as the effective transmission rate of each heterogeneous traffic VP which guarantees both quality of service (QoS) in the cell level and the grade of service (GoS) in the connection level. The multi-objective function which comprises the average blocking rates (ABR) and the average packet delay (APD) is regarded as our designed VPs system assignment objective. A new coding technique in which each chromosome represents one of the VP system configurations and is also created associating with the designing delay bound of each VP is proposed. The concept of past solution is modified to suit the dynamic VPs system control technique that requires fast calculation speed. Numerical results show that by using our proposed method, it gives a good solution. Faster calculation speed than offered in previous literature, can be obtained by using our new coding technique. Moreover, comparative studies between this Genetic Algorithm (GA) application and conventional exhaustive search method which has been used as a reference algorithm to evaluate the quality of solution for global optimum provides very similar results.