2012 Annual Report of Advanced Networked Environment Division, Cybermedia Center, Osaka University, Japan

This web page is the 2012 annual report of Advanced Networked Environment Division, Cybermedia Center, Osaka University (Ubiquitous Network Laboratory, Graduate School of Information Science and Technology, Osaka University / Nakano Laboratory).

Japanese version of this web page is here.

Table of contents

  1. Members
    1. Laboratory staffs
    2. Joint researcher
    3. Students
  2. Achievements
    1. Research on wireless mesh networks
      1. Time slot assignment algorithm considering traffic demand and link transmission quality
      2. Effect of radio interference estimation methods for time slot assignment on performance of IEEE 802.11j relay networks
      3. Time slot assignment algorithm considering wireless link transmission quality
    2. Research on pedestrian counting
      1. Counting pedestrians passing through virtual gate in video sequences
      2. Multiple regression analysis of explanatory variables for pedestrian counting in video sequences
      3. Counting pedestrians with compound-eye binary sensors
    3. Research on overlay network architectures
      1. Reduction of inter-ISP transit cost caused by overlay routing
      2. Distributed and conflict-aware measurement based on local information exchange in overlay networks
      3. Virtual network assignment considering performance and fault tolerance in a multi-tenant data center
      4. The interation between overlay routing and inter-domain routing structure
    4. Research on architecture of transport layer for next-generation high-speed network
      1. Analysis of power consumption in TCP data transmission over a wireless LAN environment
      2. Influence of power saving technique in IEEE 802.11 multi-hop networks on network performance
      3. Improvement of end-to-end bandwidth measurement method for power-saving routers
      4. Measuring available bandwidth of multiple parts on end-to-end network path
      5. Performance evaluation of distributed computing environment considering power consumption
      6. Information network design inspired by degeneracy and redundancy in biological networks
      7. HEMS over cloud system utilizing realtime web technologies
  3. Publications
    1. Journal papers
    2. International conference papers
    3. Theses
      1. Ph.D. Theses
      2. Masters' Theses
      3. Bachelors' Theses

1. Members

1.1. Laboratory staffs

Hirotaka Nakano
Hirotaka Nakano
Professor
Go Hasegawa
Go Hasegawa
Associate Professor
Yoshiaki Taniguchi
Yoshiaki Taniguchi
Assistant Professor
Mari Onishi
Mari Onishi
Secretary

1.2. Joint researcher

Masayuki Murata
Masayuki Murata
Osaka University
Graduate School of IST
Professor

1.3. Students

Masafumi Hashimoto
Masafumi Hashimoto
Doctoral Course 3rd
Kazuhito Matsuda
Kazuhito Matsuda
Doctoral Course 3rd
Xun Shao
Xun Shao
Doctoral Course 3rd
Daisuke Kobayashi
Daisuke Kobayashi
Doctoral Course 1st
Tomoya Kitayama
Tomoya Kitayama
Master Course 2nd
Wataru Tourisaka
Wataru Tourisaka
Master Course 2nd
Ryosuke Mine
Ryosuke Mine
Master Course 2nd
Yusuke Iijima
Yusuke Iijima
Master Course 1st
Shoichi Takagi
Shoichi Takagi
Master Course 1st
Yuki Tsubouchi
Yuki Tsubouchi
Master Course 1st
Kohei Higo
Kohei Higo
Master Course 1st
Shuto Fujii
Shuto Fujii
Master Course 1st
Miki Mizushima
Miki Mizushima
Master Course 1st
Takuro Okazaki
Takuro Okazaki
Bachelor Course 4th
Kai Koyama
Kai Koyama
Bachelor Course 4th
Takuya Tanoue
Takuya Tanoue
Bachelor Course 4th
Kazuyuki Hashimoto
Kazuyuki Hashimoto
Bachelor Course 4th

2. Achievements

2.1. Research on wireless mesh networks

2.1.1. Time slot assignment algorithm considering traffic demand and link transmission quality

Time slot assignment algorithm considering traffic demand and link transmission quality

Wireless multi-hop relay networks based on IEEE 802.16j provide broadband wireless access environment by using multi-hop wireless communications. IEEE 802.16j adopts Time Division Multiple Access (TDMA), where time slots are assigned to wireless links between relay nodes as transmission opportunities. Time slot assignment has large influence on link transmission quality because it is affected by interference signals from nodes using the same time slot. Furthermore, when adaptive modulation and coding is employed for data transmission on wireless links, the transmission bitrate is highly dependent on the link transmission quality. Therefore, algorithms that assign time slots to links are important for enhancing relay network performance.

In the relay network, time slots should be assigned to links according to their traffic loads, which is determined by the traffic demand from user terminals connected to relay nodes. Therefore, we need to assign time slots to links considering the balance between traffic load and transmission quality of each link because links with insufficient or excess transmission bit amount against traffic loads cause the waste of wireless resources and the degradation of network performance. However, to the best of my knowledge, there are no existing research on time slot assignment that considers both traffic demand and detailed link transmission quality.

In this research, we propose a balancing algorithm of time slot assignment for IEEE 802.16j relay networks, considering traffic demand and link transmission quality. The proposed method increases the number of time slots at links that have not enough transmission bit amount and decreases the number of time slots at links with excess transmission bit amount against their traffic loads. Repeating this operation maintains the balance between transmission bit amount and traffic load on links in the network. Performance evaluation results exhibit that the proposed method improves data transfer throughput by up to around 500%. It also shows that proposed method can obtain around 94% data transfer throughput of optimal time slot assignment.

[Related paper]

  1. Tomoya Kitayama, Go Hasegawa, Yoshiaki Taniguchi and Hirotaka Nakano, ``Time slot-adding algorithm for improving bottleneck link throughput in IEEE 802.16j relay networks,'' in Proceedings of the 27th International Conference on Information Networking (ICOIN 2013), pp.606-611, Jan. 2013. [paper]
  2. Tomoya Kitayama, ``Time slot assignment algorithm in IEEE 802.16j relay networks considering traffic demand and link transmission quality,'' Master's Thesis, Graduate School of Information Science and Technology, Osaka University, Feb. 2013.

2.1.2. Effect of radio interference estimation methods for time slot assignment on performance of IEEE 802.11j relay networks

Effect of radio interference estimation methods for time slot assignment on performance of IEEE 802.11j relay networks

On time slot assignment in IEEE 802.16j multi-hop relay networks, the interference relationships among links are estimated for spatial reuse of channel resource. Most of existing works treat interference relationships based on distance or hop count between nodes. However, these methods determine interference relationships among links in binary fashion, so they cannot take into account gradual changes in wireless link quality due to radio wave propagation and interference characteristics in practical situations. In addition, IEEE 802.16j multi-hop relay networks adopt Adaptive Modulation and Coding (AMC) for stable and efficient communication. Therefore, the network performance is heavily affected by which models to be used in estimating radio wave propagation and how to infer interference relationships in time slot assignment. However, to the best of my knowledge, there is no existing works on time slot assignment algorithms for IEEE 802.16j relay networks considering above-mentioned complicated factors.

In this research, we evaluate the performance of time slot assignment algorithms based on various interference estimation methods by considering differences in radio propagation model and the effect of AMC. For radio propagation models we assume the line-of-sight and nonline-of-sight environments with various path loss exponent. we consider three algorithms for time slot assignment with and without consideration of the signal to interference plus noise ratio (SINR). Furthermore, we introduces a time slot assignment algorithm which takes into account changes in transmission bit amount due to AMC. Through performance evaluations, we clarify the sensitivity of the control parameters in interference estimation method on the performance of the relay networks. Moreover, we demonstrate that by carefully tuning the control parameter, the interference estimation method based on the network topology information can achieve almost the equivalent performance as the method requiring SINR calculation.

[Related paper]

  1. Ryosuke Mine, ``Effect of radio interference estimation methods for time slot assignment on performance of IEEE 802.11j relay networks,'' Master's Thesis, Graduate School of Information Science and Technology, Osaka University, Feb. 2013.
  2. Ryosuke Mine, Go Hasegawa, Yoshiaki Taniguchi, Hirotaka Nakano, ``Effect of radio interference models on the performance of time slot assignment algorithms in IEEE 802.16j relay networks,'' in Proceedings of the 8th IEEE International Workshop on the Performance Analysis and Enhancement of Wireless Networks (IEEE PAEWN 2013) (IEEE AINA 2013 Workshop), pp.107-113, Mar. 2013. [paper]

2.1.3. Time slot assignment algorithm considering wireless link transmission quality

Time slot assignment algorithm considering wireless link transmission quality

In IEEE 802.16j relay networks, wireless communication is carried out based on Time Division Multiple Access. By using the adaptive modulation and coding, each link in the network can obtain the data rate according to the Signal to Interference Noise Ratio (SINR). When a few links utilize a certain time slot, the data rate becomes large because of less radio interference. But, it means that the degree of spatial reuse of the network resources is low, increasing the frame size. Therefore, it is necessary to assign time slots so that the traffic demand of each link is satisfied, as well as achieving small frame length. In this research, we propose new time slot assignment methods for IEEE 802.16j relay networks. One method is to assign time slots to each link in the predetermined order of links, and the another is to determine the group of links to utilize each time slot. As a result of the evaluation by simulation experiments, we show that the latter method is more effective to reduce the frame length.

2.2. Research on pedestrian counting

2.2.1. Counting pedestrians passing through virtual gate in video sequences

Counting pedestrians passing through virtual gate in video sequences

Pedestrian counting is needed in many situations such as safety control in airports or stations, traffic control in streets and surveillance at event sites. Pedestrian counting is usually conducted manually or automatically using sensors and video sequences captured by cameras. Manual counting requires labor costs and can not be used in crowded scenes due to human error. Pedestrian counting using video sequences has advantage of flexibility of camera placement compared with other sensors, because video sequences can be retrieved remotely. Pedestrian counting systems using video sequences are divided into two kinds of systems. One is used for counting pedestrians for each frame, and the other is used for counting pedestrians passing at specific points or lines. In both pedestrian counting systems, improvement of the counting accuracy under crowded situations is open issue.

In our research group, we have proposed a method for counting pedestrians for each frame. In the method, optical flows which are vectors of moving objects, are first obtained from video sequences. Next, optical flows are clustered according to lengths, angles, and source locations of optical flows. Then, the number of pedestrians are estimated based on the number of clusters. The effectiveness of the method was shown through experimental evaluation using several video sequences. In this research, we propose a method for counting pedestrians passing at a specific line. We call the line virtual gate. The proposed method is based on optical flow clustering like our previous study. Here, there are variations of process to obtain optical flows from video sequences, e.g., coordinate systems used, starting points of optical flows, and the number of frames to obtain optical flows. In this research, we evaluate all variations of process to obtain optical flows, and find the best way to achieve the highest counting accuracy. Through experimental evaluations using a video sequence captured from Cybermedia Center, Osaka University, it was shown that the proposed method achieves higher accuracy when starting points of optical flows are set on the virtual gate.

2.2.2. Multiple regression analysis of explanatory variables for pedestrian counting in video sequences

Multiple regression analysis of explanatory variables for pedestrian counting in video sequences

In recent years, video processing-based methods for counting pedestrians in a crowded scene have been proposed. In these methods, the relationships between various features in video sequences and the number of pedestrians are obtained using training data. Then, the number of pedestrians is estimated from the video features and the pre-learning relationships. However, for each method, different video features are used and its performance is evaluated under different environments. Therefore, it is difficult to compare the effectiveness of video feature for estimating the number of pedestrians. In this research, we investigate the relationships between various video features and the number of pedestrians using multiple regression analysis under same evaluation environments. We use the size of moving objects, the perimeter of moving objects, the number of optical flows, and the number of clusters of optical flows as video features. Through analysis using actual video sequences, we show that combining the number of optical flows and perimiter of moving objects is effective for estimating the number of pedestrians under crowded situations.

[Related paper]

  1. Takuya Tanoue, ``Multiple regression analysis of explanatory variables for pedestrian counting in video sequences,'' Bachelor's Thesis, School of Engineering Science, Osaka University, Feb. 2013. (in Japanese)

2.2.3. Counting pedestrians with compound-eye binary sensors

Counting pedestrians with compound-eye binary sensors

In many situations such as survey of the number of visitors to commercial facilities and event sites, there are demands for pedestrian counting. Manual pedestrian counting has some problems such as high-cost and decrease of counting accuracy under crowded situation. Therefore, automated pedestrian counting technologies have attracted much attention. Binary sensors are among the simplest sensors and can detect only the presence or absence of pedestrians within sensing range. Although binary sensors can neither detect the number of pedestrians nor identify pedestrians individually, they have advantages in terms of cost, simplicity, and energy-efficiency. By constructing a wireless sensor network from binary sensors equipped with wireless communication devices, it is possible to construct a pedestrian counting system. However, in the pedestrian counting system with binary sensors, it is a problem that estimation accuracy decreases under crowded situation such as many pedestrians are incoming and outgoing.

In this research, we propose a method for estimating the number of pedestrians under the situation that pedestrians move bidirectionally such as a corridor. In the proposed method, a compound-eye sensor is constructed on a ceiling by closely placing two binary sensors whose sensing regions are partly overlapping. The output data from compound-eye sensor is gathered to a monitoring server through wireless networks, and the monitoring server estimates the number of pedestrians by using the information. In this research, to estimate the number of pedestrians from sensor data, we propose a method based on the Monte Carlo method. Concretely, the proposed method conducts a number of Monte Carlo simulations while the system detects pedestrians. When the system detects no pedestrians, a simulation scenario that has the smallest difference between output histories of compound-eye sensor is selected, and the number of pedestrians under the simulation scenario is used as the estimation result. In this research, we evaluated the fundamental characteristics of the proposed method by changing compound-eye sensor parameters, arrival rate of pedestrians and the number of simulations in the proposed method. In addition, it was shown that the estimation accuracy is improved up to 90% compared with a existing method that estimates the number of pedestrians from difference between output timing of two binary sensors.

[Related paper]

  1. Shuto Fujii, Yoshiaki Taniguchi, Go Hasegawa and Hirotaka Nakano, ``Monte Carlo-based bi-directional pedestrian counting with compound-eye sensor,'' in Proceedings of the 2012 IEEE International Conference on Computer Systems and Industrial Informatics (ICCSII 2012), 6 pages, Dec. 2012. [paper]

2.3. Research on overlay network architectures

2.3.1. Reduction of inter-ISP transit cost caused by overlay routing

Reduction of inter-ISP transit cost caused by overlay routing

The current Internet consists of a numerous number of Internet Service Providers (ISPs), each of which operates own network to maximize its own benefit. Each ISP configures the IP-level routes for the network traffic based on monetary cost of inter-ISP links. In recent years, on the other hand, new types of traffic routing mechanisms are getting much attention, which largely impact on the ISPs' cost structure. Application-level traffic routing is one of such mechanisms. Because the application-level traffic routing is conducted by end-to-end approach without any care of the monetary costs of inter-ISP links, it can be harmful to the ISPs' cost structure. Content-centric networking (CCN), which routes packets based on content name, also largely affects to the ISPs' cost structure. On the contrary to application-level traffic routing, CCN brings positive effect on inter-ISP transit cost due to its in-network caching mechanism, because that it can reduce the traversing traffic on transit links by replying the cached contents when there is a cache hit. However, CCN is not developed considering ISPs cost structure directly, and in-network caching of CCN does not help reducing the transit cost of ISPs with peering relationships.

This research begins by developing a method to reduce transit cost of application-level traffic routing conducted by individual end user. To determine the relationships among ASes, which are required for ISP cost-aware routing, we first construct a method to estimate the transit cost of application-level paths from end-to-end network performance values.

In the next part of this research, we aim to realize an application-level traffic routing conducted by individual operators in multiple ISPs in a distributed fashion. In the proposed method, we assume that the operators of application-level traffic routing cooperate with each other on their route selection, so that we can avoid performance degradation caused by route overlaps due to their selfish decisions. We then propose an application-level traffic routing method based on distributed simulated annealing to obtain near-optimal solutions to the problem.

The third part of this research, we focus on the in-network caching mechanism in CCN and propose a new mechanism to reduce the transit cost by cache sharing mechanism, that is, cooperative cache sharing among CCN routers in multiple ISPs. It aims to improve cache hit ratio, which leads the further reduction in the inter-ISP transit cost. In the proposed method, the CCN routers share the memory space for content caching.

[Related paper]

  1. Kazuhito Matsuda, ``Reducing ISPs' cost by application-level path selection and in-network caching,'' Ph.D. Thesis, Graduate School of Information Science and Technology, Osaka University, Jan. 2013.
  2. Kazuhito Matsuda, Go Hasegawa, Satoshi Kamei and Masayuki Murata, ``A method to reduce inter-ISP transit cost caused by overlay routing based on end-to-end network measurement,'' IEICE Transactions on Information and Systems, vol.E96-D, no.2, pp.289-302, Feb. 2013. [paper]
  3. Kazuhito Matsuda, Go Hasegawa, and Masayuki Murata, ``An application-level routing method with transit cost reduction based on a distributed heuristic algorithm,'' submitted for publication.
  4. Kazuhito Matsuda, Go Hasegawa, and Masayuki Murata, ``Multi-ISP cooperative cache sharing for saving inter-ISP ransit cost in content centric networking,'' submitted for publication.
  5. Kazuhito Matsuda, Go Hasegawa, and Masayuki Murata, ``Cooperative cache sharing among ISPs for additional reduction in inter-ISP transit cost in content-centric networking,'' submitted for publication.

2.3.2. Distributed and conflict-aware measurement based on local information exchange in overlay networks

Distributed and conflict-aware measurement based on local information exchange in overlay networks

Measuring network resource information, including available bandwidth, propagation delay, and packet loss ratio, is an important task for efficient operation of overlay network services. Although measurement accuracy can be enhanced by frequent measurements, performing measurements with high frequency can cause measurement conflict problem that increases the network load and degrades measurement accuracy. In this research, we propose a low-cost, distributed and conflict-aware measurement method that reduces measurement conflicts while maintaining high measurement accuracy. The main idea is that the overlay node exchanges the route information and the measurement results with its neighboring overlay nodes while decreasing the measurement frequency. This means our method trades the overhead of conducting measurements for the overhead of information exchange to enhance measurement accuracy. Simulation results show that the relative error in the measurement results of our method can be decreased by half compared with the existing method when the total measurement overheads of both methods are equal. We also confirm that exchanging measurement results contributes more to the enhancement of measurement accuracy than performing measurements.

[Related paper]

  1. Dinh Tien Hoang, Go Hasegawa and Masayuki Murata, ``A distributed and conflict-aware measurement method based on local information exchange in overlay networks,'' in Proceedings of the 2012 Australasian Telecommunication Networks and Applications Conference (ATNAC 2012), 6 pages, Nov. 2012. [paper]
  2. Dinh Tien Hoang, Go Hasegawa and Masayuki Murata, ``A low-cost, distributed and conflict-aware measurement method for overlay network services utilizing local information exchange,'' IEICE Transactions on Communications, vol.E96-B, no.2, pp.459-469, Feb. 2013. [paper]

2.3.3. Virtual network assignment considering performance and fault tolerance in a multi-tenant data center

Virtual network assignment considering performance and fault tolerance in a multi-tenant data center

In a multi-tenant data center, a proper assignment of tenants' virtual overlay networks on the physical underlay network is indispensable for sharing total bandwidth of the physical network effectively and tolerating network failures. In this research, for increasing performance and availability of the virtual networks, we first formulate the problem that deals with the effective bandwidth of a virtual network, which is defined by the difference between available bandwidth allocated to the virtual network and loss of the bandwidth when the failure of a element occurs in the physical network. Then, we provide procedures to recover from the failure, and propose a model for the virtual network's recovery time from the failure in the physical network. In the proposed model, the recovery time depends on the degree of concentration of the virtual network elements on the physical network elements. Finally, using computer simulations, we confirm that when we assign the virtual networks so as to maximize the sum of their effective bandwidth, the virtual networks can fully utilize the physical bandwidth, while the total downtime is reduced to one-third as compared to the assignment for maximizing the sum of available bandwidth of the virtual networks.

2.3.4. The interation between overlay routing and inter-domain routing structure

The interation between overlay routing and inter-domain routing structure

Today's Internet is composed of thousands of interconnected networks operated by independent Internet Service Providers (ISPs). The task of establishing routes between ISPs concerning the business relationships is called inter-domain routing. The current inter-domain routing protocol is the Border Gateway Protocol (BGP). In recent years, more and more studies find that BGP routes are sub-optimal in end-to-end performance metrics. As a candidate to overcome the functionality limitations of BGP, overlay routing has been receiving increasing attention. The basic idea of overlay networks is to form a virtual network on top of the native networks so that overlay nodes can be customized to incorporate complex functionality without modifying the IP network. Overlay routing has been proved to be effective in many applications. However, as overlay routing works in the application layer, it is difficult for ISPs to conduct traffic engineering effectively. In this research, we conduct a comprehensive study on the implications of overlay traffic to interconnected ISPs' contracting and inter-domain engineering issues, and intend to give some guidelines for ISPs to better coexist with user-directed overlay traffic. By further considering the principles of BGP routing and overlay routing, we then discuss a question that rather than mitigate the effect of overlay traffic, how ISPs could take the advantages of overlay technologies to improve the inter-domain routing.

We begin this research by exploring the implications of overlay routing to ISPs' contracting issues. In this study, we suppose a typical network scenario in which two ISPs have a peering relationship, and both of them access to the Internet through transit providers. By combining the overlay traffic patterns and ISPs economic model, we discuss ISPs peering strategies including whether to set up peering connection, what kind of peering agreement to be established, and how to decide the optimal peering link capacity.

The implications of overlay traffic are not only to ISPs' contracting issues, but also inter-domain traffic engineering. Therefore, in the second part of the research, we propose a typical multihoming network in which the tussle between overlay routing and traffic engineering is most likely to happen. We model the interaction of ISP。ヌs traffic engineering and overlay routing as a noncooperative routing game, and show that it is dangerous for ISP to neglect the overlay's routing decision, because persistent routing oscillation may occur. We therefore propose a routing strategy for the ISP with which ISP can avoid routing oscillation definitely, while keeping the cost relatively low.

In the first two parts of the research, we studied the implications of overlay traffic to ISPs' contracting and inter-domain traffic engineering issues, and gave some guidelines for ISPs to better coexist with overlay traffic. In the third part of the research, we consider a question that rather than mitigate the effect of user-directed overlay traffic, whether can ISPs improve both business and inter-domain routing structure by taking the advantage of overlay technology? As an answer, we propose an inter-domain overlay structure operated by ISPs based on ISP alliance. The ISP alliance in this research is formed by adjacent ISPs, and each ISP operates one or more overlay nodes. In the ISP alliance, we introduce novel routing and charging structure, with which both inter-domain traffic and ISPs。ヌ economic interest can be optimized.

As above, in this research, we study the interaction of ISP。ヌs inter-domain traffic engineering and overlay routing, and give guidelines for ISPs to mitigate the implication of overlay traffic. Based on these studies, we propose an inter-domain overlay network based on ISP alliance, which can take the advantages of overlay technologies, while overcome the shortcomings.

[Related paper]

  1. Xun Shao, Go Hasegawa, Yoshiaki Taniguchi and Hirotaka Nakano, ``A game-theoretic analysis of interaction between overlay routing and multihoming,'' in Proceedings of the 14th Asia-Pacific Network Operations and Management Symposium (APNOMS 2012), 7 pages, Sep. 2012. [paper]
  2. Xun Shao, ``Studies on the interation between overlay routing and inter-domain routing structure,'' Ph.D. Thesis, Graduate School of Information Science and Technology, Osaka University, Jan. 2013.
  3. Xun Shao, Go Hasegawa, Yoshiaki Taniguchi and Hirotaka Nakano, ``A routing strategy for multihomed ISP to mitigate the impact of overlay traffic,'' IEICE Transactions on Information and Systems, vol.E96-D, no.2, pp.193-201, Feb. 2013. [paper]
  4. Xun Shao, Go Hasegawa, Yoshiaki Taniguchi and Hirotaka Nakano, ``Economically efficient interdomain overlay network based on ISP alliance,'' in Proceedings of the 9th International Conference on Networking and Services (ICNS 2013), pp.153-159, Mar. 2013. [paper]
  5. Xun Shao, Go Hasegawa, Yoshiaki Taniguchi and Hirotaka Nakano, ``The implications of overlay routing for ISPs' peering strategies,'' IEICE Transactions on Information and Systems, vol.E96-D, no.5, May 2013. (to appear)
  6. Xun Shao, Go Hasegawa, Yoshiaki Taniguchi and Hirotaka Nakano, ``An overlay network based on ISP alliance for economically efficient interdomain traffic routing,'' submitted for publication.

2.4. Research on architecture of transport layer for next-generation high-speed network

2.4.1. Analysis of power consumption in TCP data transmission over a wireless LAN environment

Analysis of power consumption in TCP data transmission over a wireless LAN environment

With recent developments in network technologies, wireless LANs (WLANs) have been installed widely and many mobile devices have been able to access the Internet everywhere everytime through WLANs. As a result, fairness among users and energy efficiency grow in importance in WLANs. In this research, in order to resolve these issues on transport-layer protocols and WLANs, we study on transport-layer solutions to achieve fairness and energy efficiency in WLAN environments. This research begins by proposing, designing, and implementing a transport-layer solution to alleviate unfairness among TCP flows in WLANs. To alleviate such unfairness, we present a transport-layer solution that TCP congestion control mechanisms are activated against congestion at an AP. Through computer simulations and experiments in real WLAN environments, the proposed method successfully achieves both fairness among upstream TCP flows and fairness between upstream and downstream flows regardless of vendor implementations of APs and wireless network interface (WNIs). The second part of this research deals with energy efficiency of wireless clients in WLANs. Energy consumption models are constructed for TCP data transfer over a WLAN in order to assess impacts of the TCP behavior on energy efficiency. Because of importance of the TCP behavior, the proposed models consist of the combination of two layer models: a MAClevel model and a TCP-level model. In order to improve the sleep efficiency, TCP-level burst transmission behavior is proposed, which reduces the number of state transitions between active and sleep modes by transmitting multiple data packets in groups. By comparing the energy consumption between WNIs with CAM and with ideal sleep mode, numerical examples reveal the upper bound of energy savings under these sleep strategies. In particular, TCP-level burst transmission successfully reduces energy consumption with increasing moderate delay. To realize the energy saving by the above work, we need to alleviate uncoordinated behavior by multiple applications running on a single client, which produces the difficulty in control of sleep timing. For that purpose, as the last part of this research, SCTP tunneling is proposed and designed. SCTP tunneling has two features: flow aggregation and burst transmission. It aggregates multiple TCP flows into a single SCTP association between a wireless client and an AP to control packet transmission and reception timings. Furthermore, to enhance the sleep efficiency, SCTP tunneling reduces the number of state transitions by handling multiple packets in a bursty fashion. We extend the above energy consumption model and construct a mathematical model of the energy consumed by SCTP tunneling to assess its energy efficiency. Numerical examples based on the model show that the proposed method can reduce energy consumption by up to 69%. Implementation issues of SCTP tunneling are also discussed. As stated above, we propose, design, and implement transport-layer solutions to achieve per-flow fairness among TCP flows and energy efficiency for multiple TCP flows in a WLAN. Through examining the issues on both fairness and energy efficiency, this research shows that these solutions are feasible approaches and can be applied to real

[Related paper]

  1. Masafumi Hashimoto, Go Hasegawa and Masayuki Murata, ``Exploiting SCTP multistreaming to reduce energy consumption of multiple TCP flows over a WLAN,'' in Proceedings of the 2nd International Conference on Green Communications and Networking (GreeNets 2012), 8 pages Oct. 2012.
  2. Masafumi Hashimoto, ``Transport-layer solutions for achieving fairness and energy efficiency in wireless LANs,'' Ph.D. Thesis, Graduate School of Information Science and Technology, Osaka University, Jan. 2013.
  3. Masafumi Hashimoto, Go Hasegawa and Masayuki Murata, ``SCTP tunneling: Flow aggregation and burst transmission to save energy for multiple TCP flows over a WLAN,'' submitted for publication.
  4. Masafumi Hashimoto, Go Hasegawa and Masayuki Murata, ``An analysis of energy consumption for TCP data transfer with burst transmission over a wireless LAN,'' submitted for publication.

2.4.2. Influence of power saving technique in IEEE 802.11 multi-hop networks on network performance

Influence of power saving technique in IEEE 802.11 multi-hop networks on network performance

Internet access via wireless networks has become popular due to the rapid development of various wireless devices such as smartphones and tablet PCs. Since these devices consume a lot of electric power in data transmission over wireless networks, we need to reduce the power consumption in data transmission by such devices. The IEEE 802.11 WLAN standard defines multiple data rates, each of which has various characteristics such as power consumption, data rate, modulation method, and transmission distance. It is important to choose the optimal data rate to reduce the power consumption, as well as improving data transmission performance. Furthermore, when considering data transmission over multi-hop networks, we need to take more factors into consideration since the data rate and transmission power affects the hop count between a sender and a receiver, and resulting power consumption. Therefore, in this research, we investigate the effect of data rate selection on power consumption in data transmission over IEEE 802.11-based wireless multi-hop networks. We present that it is possible to decrease power consumption by intentionally choosing lower data rate when the nodes suffer the frequent interference.

[Related paper]

  1. Wataru Toorisaka, ``Power consumption analysis of data transmission over IEEE 802.11 multi-hop networks,'' Master's Thesis, Graduate School of Information Science and Technology, Osaka University, Feb. 2013.

2.4.3. Improvement of end-to-end bandwidth measurement method for power-saving routers

Improvement of end-to-end bandwidth measurement method for power-saving routers

The increase in energy consumption associated with network traffic explosion is becoming a major problem. To realize energy-efficient networking, a number of researchers have focused on technologies that dynamically adjust the processing performance and the link speed of routers and switches according to the network traffic load. However, when such power-saving routers and switches are present in the network, the existing network protocols and control methods may not work well since they do not assume the existence of such routers and switches. We focuses on the measurement method of an end-to-end available bandwidth, which is an important performance metric for various network controls.

In this research, we introduce a parameter tuning method for Pathload, which is a popular tool for measuring the end-to-end available bandwidth, to maintain the measurement accuracy in the network with power-saving routers, while not affecting the behavior of power-saving routers. For that purpose, we first investigate the interactions between the bandwidth measurement behavior of Pathload and the energy efficiency of power-saving routers by conducting extensive simulation experiments. In the simulation experiments, we examine the effects of the power-saving router on the measurement accuracy and the effects of the Pathload measurement on the behavior of the power-saving router. Based on simulation results, we exhibit that both the measurement accuracy of Pathload and the energy efficiency of power-saving routers degrade, particularly when the power saving functions are triggered in short cycles.

As the second contribution of this research, we propose a parameter tuning method for Pathload that maintain measurement accuracy without affecting the behavior of power-saving routers. We accomplish this by giving simple mathematical analysis of the traffic load of Pathload on the power-saving router. We confirm the accuracy of our analysis by comparing the analysis results with corresponding simulation results. We also show that Pathload can measure an available bandwidth without affecting the behavior of power-saving routers by tuning the number of probing packets on the basis of the analysis results.

[Related paper]

  1. Daisuke Kobayashi, Go Hasegawa and Masayuki Murata, ``Evaluation and improvement of end-to-end bandwidth measurement method for power-saving routers,'' in Proceedings of the 2012 International Communications Quality and Reliability Workshop (IEEE CQR 2012), 6 pages, May 2012. (Best Paper Award) [paper] [slide]

2.4.4. Measuring available bandwidth of multiple parts on end-to-end network path

Measuring available bandwidth of multiple parts on end-to-end network path

The available bandwidth on an end-to-end network path is an important metric for detecting network congestion, adapting transmission rate, configuring paths and topologies on overlay networks, and so on. The existing available bandwidth measurement techniques aimed only at knowing available bandwidth of bottleneck part on the path and most of them do not specify where the bottleneck is. Also, they cannot measure available bandwidth of multiple parts on the path separately. If we can know available bandwidth of each part of the path, we, for example, can rapidly configure the path on the overlay network to satisfy performance requirements of application services. Also, in wireless-cum-wired network environment, we can improve data rate selection on the wireless network dependent on the network resource amount of the wired network. However, to the best of our knowledge, there is no existing works on simultaneous measurement of multiple parts of a network path in an end-to-end fashion.

In this research, we propose a simultaneous measurement method of available bandwidth of multiple parts on an end-to-end network path. The proposed method adapts an end-to-end measurement principle, and estimates available bandwidth based on changes in packet sending and arrival intervals under the situation where intermediate routers can record arriving and departing times on incoming packets as a timestamps. Specifically, considering the effect of cross traffic on traversing networks, the endhost sends probe packets at various rates and estimates the available bandwidth using their incoming and outgoing rates based on statistical processing using fluid traffic model. We present extensive simulation results of the proposed method and confirm that it can accurately measure available bandwidth of each part on the path even when the available bandwidth of the sender-side network is smaller than that of the receiver-side network. We also evaluate the proposed method with numerous network scenarios varying physical and available bandwidth settings, hop count of the path, and confirm the robustness of the proposed method.

[Related paper]

  1. Kazumasa Koitani, Go Hasegawa and Masayuki Murata, ``Measuring available bandwidth of multiple parts on end-to-end network path,'' in Proceedings of the 2012 International Communications Quality and Reliability Workshop (IEEE CQR 2012), 6 pages, May 2012. [paper]

2.4.5. Performance evaluation of distributed computing environment considering power consumption

Performance evaluation of distributed computing environment considering power consumption

When information systems are consolidated in a large data center, a huge amount of energy is consumed for transferring massive amounts of data to the data center through a wide area network. Our approach is to reduce the network power consumption by distributing servers capable of reducing or localizing traffic across the network. In this research, we develop the models of applications, their traffic and a network system for transferring the traffic. We also introduce the models of router's and server's energy consumption, and formulate the power consumption caused by the traffic. Then, we evaluate the power consumption reduction as a result of traffic reduction by the distributed servers. Numerical evaluation results show that the whole power consumption reduces by about 20 percent when the more servers are added to the network; it increases due to the server power consumption when a lot of servers are added to the network.

[Related paper]

  1. Yukio Ogawa, Go Hasegawa and Masayuki Murata, ``Power consumption evaluation of distributed computing network considering traffic locality,'' IEICE Transactions on Communications, vol.E95-B, no.8, pp.2538-2548, Aug. 2012. [paper]

2.4.6. Information network design inspired by degeneracy and redundancy in biological networks

Information network design inspired by degeneracy and redundancy in biological networks

In this research, we propose a design method of information network systems, inspired by degeneracy and redundancy found in biological networks. It achieves high-level robustness against large-scale failures. The main idea is to realize a novel redundant configration inspired by networked buffering characteristics in gene network, providing many-to-many backup with small amount of additional resources, unlike the one-to-one or one-to-many backup in the traditional redundant systems. We evaluate the fundamental characteristics of the proposed method by computer simulations, and show that the proposed system can largely improve the recovery performance from large-scale failures compared with existing methods.

[Related paper]

  1. Takuro Okazaki, ``Robust redundant configuration method of information network systems inspired by degeneracy in biological networks,'' Bachelor's Thesis, School of Engineering Science, Osaka University, Feb. 2013. (in Japanese)

2.4.7. HEMS over cloud system utilizing realtime web technologies

HEMS over cloud system utilizing realtime web technologies

Home Energy Management System (HEMS) is paid much attraction as one of power-saving technologies for home appliances. In Japan, ECHONET and ECHONET Lite are possible candidates as HEMS protocol. Although the current HEMS is implemented as a closed system within Home Area Network (HAN), increased cost becomes a serious problem in large-scale deployment of HEMS. Therefore, in this research, we propose a method to apply ASP service for implementing HEMS at a low cost. We show the overall architecture, performance evaluation of protocol implementations for interactive Web service, and prototype implementation of the proposed system.

3. Publications

3.1. Journal papers

  1. Go Hasegawa, Shinpei Tanaka, Yoshiaki Taniguchi and Hirotaka Nakano, ``Time slot assignment algorithms to upstream links for decreasing transmission latency in IEEE 802.16j networks,'' IEICE Transactions on Communications, vol.E95-B, no.5, pp.1793-1801, May 2012. [paper]
  2. Yukio Ogawa, Go Hasegawa and Masayuki Murata, ``Power consumption evaluation of distributed computing network considering traffic locality,'' IEICE Transactions on Communications, vol.E95-B, no.8, pp.2538-2548, Aug. 2012. [paper]
  3. Masahiro Sasabe and Hirotaka Nakano, ``Perfect cell partitioning scheme for micro-cellular networks,'' Journal of Communications, vol.7, no.10, pp.749-757, Oct. 2012. [paper]
  4. Dinh Tien Hoang, Go Hasegawa and Masayuki Murata, ``A low-cost, distributed and conflict-aware measurement method for overlay network services utilizing local information exchange,'' IEICE Transactions on Communications, vol.E96-B, no.2, pp.459-469, Feb. 2013. [paper]
  5. Xun Shao, Go Hasegawa, Yoshiaki Taniguchi and Hirotaka Nakano, ``A routing strategy for multihomed ISP to mitigate the impact of overlay traffic,'' IEICE Transactions on Information and Systems, vol.E96-D, no.2, pp.193-201, Feb. 2013. [paper]
  6. Kazuhito Matsuda, Go Hasegawa, Satoshi Kamei and Masayuki Murata, ``A method to reduce inter-ISP transit cost caused by overlay routing based on end-to-end network measurement,'' IEICE Transactions on Information and Systems, vol.E96-D, no.2, pp.289-302, Feb. 2013. [paper]
  7. Shizuka Fujisawa, Go Hasegawa, Yoshiaki Taniguchi and Hirotaka Nakano, ``Pedestrian counting in video sequences based on optical flow clustering,'' International Journal of Image Processing, vol.7, no.1, Feb. 2013. [paper]
  8. Go Hasegawa, Takuro Horie and Masayuki Murata, ``Proactive recovery from multiple failures utilizing overlay networking technique,'' Telecommunication Systems, vol.52, no.2, pp.1001-1019, Feb. 2013. [paper]

3.2. International conference papers

  1. Go Hasegawa, Shoichi Takemori, Yoshiaki Taniguchi and Hirotaka Nakano, ``Determining coverage area using Voronoi diagram based on local information for wireless mesh networks,'' in Proceedings of the 9th International Conference on Information Technology : New Generations (ITNG 2012), pp.71-76, Apr. 2012. [paper]
  2. Daisuke Kobayashi, Go Hasegawa and Masayuki Murata, ``Evaluation and improvement of end-to-end bandwidth measurement method for power-saving routers,'' in Proceedings of the 2012 International Communications Quality and Reliability Workshop (IEEE CQR 2012), 6 pages, May 2012. (Best Paper Award) [paper] [slide]
  3. Kazumasa Koitani, Go Hasegawa and Masayuki Murata, ``Measuring available bandwidth of multiple parts on end-to-end network path,'' in Proceedings of the 2012 International Communications Quality and Reliability Workshop (IEEE CQR 2012), 6 pages, May 2012. [paper]
  4. Yukio Ogawa, Go Hasegawa and Masayuki Murata, ``Effect of traffic locality on power consumption of distributed computing network with a data center,'' in Proceedings of the 9th International Conference on Communications (COMM 2012), pp.233-236, June 2012. [paper]
  5. Yoshiaki Taniguchi, Go Hasegawa and Hirotaka Nakano, ``Self-organizing transmission scheduling mechanisms using a pulse-coupled oscillator model for wireless sensor networks,'' in Proceedings of the 2nd International Conference on Digital Information Processing and Communications (ICDIPC 2012), pp.85-90, July 2012. [paper]
  6. Xun Shao, Go Hasegawa, Yoshiaki Taniguchi and Hirotaka Nakano, ``A game-theoretic analysis of interaction between overlay routing and multihoming,'' in Proceedings of the 14th Asia-Pacific Network Operations and Management Symposium (APNOMS 2012), 7 pages, Sep. 2012. [paper]
  7. Masafumi Hashimoto, Go Hasegawa and Masayuki Murata, ``Exploiting SCTP multistreaming to reduce energy consumption of multiple TCP flows over a WLAN,'' in Proceedings of the 2nd International Conference on Green Communications and Networking (GreeNets 2012), 8 pages Oct. 2012.
  8. Dinh Tien Hoang, Go Hasegawa and Masayuki Murata, ``A distributed and conflict-aware measurement method based on local information exchange in overlay networks,'' in Proceedings of the 2012 Australasian Telecommunication Networks and Applications Conference (ATNAC 2012), 6 pages, Nov. 2012. [paper]
  9. Shuto Fujii, Yoshiaki Taniguchi, Go Hasegawa and Hirotaka Nakano, ``Monte Carlo-based bi-directional pedestrian counting with compound-eye sensor,'' in Proceedings of the 2012 IEEE International Conference on Computer Systems and Industrial Informatics (ICCSII 2012), 6 pages, Dec. 2012. [paper]
  10. Tomoya Kitayama, Go Hasegawa, Yoshiaki Taniguchi and Hirotaka Nakano, ``Time slot-adding algorithm for improving bottleneck link throughput in IEEE 802.16j relay networks,'' in Proceedings of the 27th International Conference on Information Networking (ICOIN 2013), pp.606-611, Jan. 2013. [paper]
  11. Ryosuke Mine, Go Hasegawa, Yoshiaki Taniguchi, Hirotaka Nakano, ``Effect of radio interference models on the performance of time slot assignment algorithms in IEEE 802.16j relay networks,'' in Proceedings of the 8th IEEE International Workshop on the Performance Analysis and Enhancement of Wireless Networks (IEEE PAEWN 2013) (IEEE AINA 2013 Workshop), pp.107-113, Mar. 2013. [paper]
  12. Xun Shao, Go Hasegawa, Yoshiaki Taniguchi and Hirotaka Nakano, ``Economically efficient interdomain overlay network based on ISP alliance,'' in Proceedings of the 9th International Conference on Networking and Services (ICNS 2013), pp.153-159, Mar. 2013. [paper]

3.3. Theses

3.3.1. Ph.D. Thesis

  1. Masafumi Hashimoto, ``Transport-layer solutions for achieving fairness and energy efficiency in wireless LANs,'' Ph.D. Thesis, Graduate School of Information Science and Technology, Osaka University, Jan. 2013.
  2. Kazuhito Matsuda, ``Reducing ISPs' cost by application-level path selection and in-network caching,'' Ph.D. Thesis, Graduate School of Information Science and Technology, Osaka University, Jan. 2013.
  3. Xun Shao, ``Studies on the interation between overlay routing and inter-domain routing structure,'' Ph.D. Thesis, Graduate School of Information Science and Technology, Osaka University, Jan. 2013.

3.3.2. Masters' Theses

  1. Tomoya Kitayama, ``Time slot assignment algorithm in IEEE 802.16j relay networks considering traffic demand and link transmission quality,'' Master's Thesis, Graduate School of Information Science and Technology, Osaka University, Feb. 2013.
  2. Wataru Toorisaka, ``Power consumption analysis of data transmission over IEEE 802.11 multi-hop networks,'' Master's Thesis, Graduate School of Information Science and Technology, Osaka University, Feb. 2013.
  3. Ryosuke Mine, ``Effect of radio interference estimation methods for time slot assignment on performance of IEEE 802.11j relay networks,'' Master's Thesis, Graduate School of Information Science and Technology, Osaka University, Feb. 2013.

3.3.3. Bachelors' Theses

  1. Takuro Okazaki, ``Robust redundant configuration method of information network systems inspired by degeneracy in biological networks,'' Bachelor's Thesis, School of Engineering Science, Osaka University, Feb. 2013. (in Japanese)
  2. Kai Koyama, ``Evaluation of time slot assignment for accommodating the user terminal in IEEE 802.16j relay networks,'' Bachelor's Thesis, School of Engineering Science, Osaka University, Feb. 2013. (in Japanese)
  3. Takuya Tanoue, ``Multiple regression analysis of explanatory variables for pedestrian counting in video sequences,'' Bachelor's Thesis, School of Engineering Science, Osaka University, Feb. 2013. (in Japanese)
  4. Kazuyuki Hashimoto, ``Effect of occlusions on pedestrian counting based on the number of salient points in video sequences,'' Bachelor's Thesis, School of Engineering Science, Osaka University, Feb. 2013. (in Japanese)