Named Data Networking (NDN) is a widely adopted future Internet architecture well-suited to large scale content retrieval.The congestion control is one of the research topics actively studied, and the rate-based congestion control method is considered to be fitted to NDN.From the viewpoint of implementation, however, the rate-based method has an issue that it requires the fine-grained clock management, which is hard to implement in off-the-shelf computers.Among the rate-based congestion control methods, an approach in which intermediate nodes report a maximum rate explicitly for a flow is considered to work well.In this paper, we pick up the Multipath-aware ICN Rate-based Congestion Control as an example of explicit rate reporting scheme, and examine how coarse-grained clock gives impacts to its performance.This paper provides the performance evaluation when consumers and NDN routers use the system clock with long time interval.This paper also proposes a method for smoothening Interest sending under a coarse-grained clock and evaluates the performance of proposed method.

CCN (Content-Centric Network) has attracted attention as new network architecture suitable for content distribution. For Quality of Service (QoS) control of CCNs in previous studies, the priority has been controlled in a relative manner using caching strategies or packet scheduling in routers. However, QoS controls based on relative priority are insufficient because video content distribution requires bandwidth for the bit rate of the video content. We propose a bandwidth reservation method for the CCN architecture to prepare the required bandwidth considering the bit rate of the video content. In the proposed method, the CCN routers adaptively reserve bandwidth using the data size requested by Interest packets. The bandwidth is then prepared for users without knowing the number of users, even when they simultaneously request different parts of the same content. The proposed method is implemented in CCNx, and its effectiveness is shown experimentally.

The Tor network is an open network that helps its users to defend against adversaries who performed traffic analysis and threatens the personal privacy and confidential security. Tor protects its users by preventing the sites they visit from revealing their physical location. As the number of Tor user increases, the performance of Tor degrades badly due to Tor's scheduler is not fairly distributing the traffic in Tor. In this paper, we highlight the problems in Tor performance due to scheduling design of Tor, which degrades the web and bulk traffic performances that multiplexes on a single TCP connection. To solve these problems, this paper emphasis on applying a simple method of active circuit switching on Tor application level, in order to distribute the bulk and web traffics on different TCP connections when congestion is detected in the Tor network. We evaluate our modified switching algorithm with the other default schedulers in Tor, such as vanilla Tor and priority EWMA scheduler in a shadow wide deployment network emulator. The experimental results show that our switching technique considerably offers stable improvement of traffic performance for all the web and bulk traffics.

In this paper, we adapted the pseudo multicast scheme with content piecing to streaming content distribution. In future research, we examine the application of network coding to scheduling.

The Tor network has its user grown by thousands every year. The increasing number of users around the world makes Tor become one of the widely used privacy networks today. However, as the number of Tor user increases, the performance of Tor degrades badly due to traffic is not fairly distributed. As a result, the Tor network does not provide a better quality of communication for all its users. To improve these problems, we proposed a simple method of dynamic circuit switching on the Tor application level to distribute the bulk and light traffic on Tor. We calculated the fairness indexes of transferred bulk and light traffic to observe any improvement and, compared our method with the default entry onion router algorithm. Our experimental results show the proposed method improves the distribution of traffic and achieves fairness of throughputs for all Tor users.

It is particularly challenging to design an efficient routing protocol for vehicular ad hoc networks due to the vehicle movement, limited wireless resources, and lossy feature of the wireless channel. We propose a protocol which uses common backbone vehicles for different traffic flows, as well as employs interflow network coding to encode packets at the backbone vehicles. A reliably connected backbone is selected by taking into account vehicle movement dynamics and link quality between vehicles. By using interflow network coding at the backbone vehicles, the protocol is able to reduce the number of generated packets by 25% in most cases compared with the conventional routing approach. As a result, the proposed protocol can provide a high packet delivery ratio, low overhead, and low delay. We show the effectiveness of the protocol using theoretical analysis and computer simulations.

We propose a QoS supporting ad hoc network scheme which employs a hybrid approach utilizing both TDMA and 802.11 DCF and present performance evaluation results of the scheme. In the scheme, TDMA period provides contention free transmissions for QoS flows, and DCF period is used to provide contention-based access for best effort or low priority flows. We evaluate the proposed scheme for various numbers of TCP flows and different CBR data rates with QualNet simulator. Simulation results show that the protocol is able to provide an efficient solution for QoS control in ad hoc networks by combing TDMA and 802.11 DCF.

Existing multi-hop routing protocols for vehicular ad hoc networks (VANETs) do not consider the packet payload size and some important MAC layer issues for the route selection. In this paper, we first solve the performance anomaly problem by providing the same transmission time for different nodes which have different channel qualities using an adaptive frame aggregation mechanism. Next, we propose a packet size-aware routing protocol where a communication route is determined by taking into account the payload size of data packets. We consider multiple metrics for the route selection specifically vehicle mobility, frame aggregation efficiency, and link quality. The proposed protocol is evaluated using real-world experiments as well as computer simulations.

We propose a routing protocol for drive-thru Internet access in delay tolerant vehicular networks. The contribution of this paper is two-folds. First, we propose a new approach which utilizes the concept of delay tolerant network (DTN) to supplement the conventional communication approach. Second, we propose an algorithm to schedule DTN transmissions in order to maximize the system throughput. The proposed protocol is able to attain higher TCP throughput than the conventional approach by providing more efficient wireless resource utilization. We use theoretical analysis and computer simulations to evaluate the proposed protocol.

Designing an efficient multi-hop broadcast protocol is very important for the realization of collision avoidance systems and other many interesting applications in vehicular ad hoc networks (VANETs). Existing protocols are optimized for a specific scenario, and are not capable of working in various scenarios. Therefore, designing an intelligent protocol which can tune itself in relation to the change of network environment is particularly important. In this paper, we propose a broadcast protocol which is able to make forwarding decision based on a self-learning mechanism. The protocol employs a fuzzy logic-based relay node selection approach to take into account multiple metrics for the forwarding algorithm. The parameters used for the fuzzy logic are tuned online using a reinforcement learning approach. Transfer learning is used to transfer knowledge to new arriving vehicles (agents) in order to shorten the convergence time. The combination of reinforcement learning, transfer learning and fuzzy logic can provide an intelligent solution for broadcasting in VANETs. We conduct computer simulations to evaluate the proposed protocol.

In vehicular ad hoc networks (VANETs), due to the limited radio propagation range of wireless devices, many safety applications require a multihop broadcast protocol to disseminate traffic warning information. However, providing an efficient multi-hop forwarding of broadcast messages has been a challenging problem due to vehicle movement, limited wireless resources, and unstable signal strength. In this paper we propose a broadcast protocol that can provide a low message overhead and a high packet dissemination ratio. The proposed scheme uses a fuzzy logic algorithm to choose the next hop relay nodes and uses network coding to improve the packet dissemination ratio without increasing the message overhead. By using the fuzzy logic algorithm, the protocol can choose the best relay node by taking intervehicle distance, vehicle velocity, and link quality into account. Network coding is used to improve the packet reception ratio by utilizing the broadcast nature of wireless channels. We show the effectiveness of the proposed scheme by using both theoretical analysis and computer simulations.

Multihop data dissemination in vehicular ad hoc networks (VANETs) is very important for the realization of collision avoidance systems and many other interesting applications. However, designing an efficient data dissemination protocol for VANETs has been a challenging issue due to vehicle movements, limited wireless resources, and the lossy characteristics of wireless communication. In this paper, we propose a protocol that can provide a lightweight and reliable solution for data dissemination in VANETs. The protocol employs dynamically generated backbone vehicles to disseminate broadcast packets to reduce the MAC-layer contention time at each node while maintaining a high packet dissemination ratio by taking into account vehicle movement dynamics and the link quality between vehicles for the backbone selection. The protocol also uses network coding to reduce the protocol overhead and to improve the packet reception probability as compared with conventional approaches. We use theoretical analysis and computer simulations to show the advantage of the proposed protocol over other existing alternatives.

In vehicular ad hoc networks (VANETs), multi-hop broadcast communications are required for many applications including driver assistance systems. However, providing a low end-to-end latency has been very challenging. In this paper, we propose a joint MAC network layer multi-hop broadcast protocol. For the network layer, the proposed protocol reduces the number of sender nodes by using common forwarder nodes for different traffic flows. At the MAC layer, the proposed protocol uses a Q-Learning algorithm to adjust the contention window size. By interacting with the environment, the protocol can find the best contention window size to transmit data packets and therefore can provide a high packet dissemination ratio and low end-to-end delay for various scenarios. The simulation results demonstrate the advantage of the proposed protocol over other existing alternatives.

We propose a QoS supporting ad hoc network protocol which employs a hybrid approach utilizing both TDMA and 802.11 DCF. TDMA period provides contention free transmissions for QoS flows, and DCF period is used to provide contention-based access for best effort or low priority flows. TDMA time slots are assigned on admission basis in a distributed manner by utilizing network routing information and considering current assignment situation. In DCF period, frames are transmitted not to disturb the TDMA period. By combing TDMA and 802.11 DCF, the proposed ad hoc network is able to provide an efficient solution for QoS control in ad hoc networks. We use QualNet simulator to evaluate the proposed scheme.

Packet delivery ratio and end-to-end delay are the two most important metrics for vehicular ad hoc network applications. In this paper, we propose a MAC layer protocol which can provide a high packet delivery ratio, low end-to-end delay, and high fairness for various scenarios. The proposed protocol uses a Q-Learning algorithm to adjust the contention window size in order to provide an efficient channel access scheme for various network situations. The simulation results demonstrate the advantage of the proposed protocol over other alternatives.

In vehicular ad hoc networks (VANETs), multi-hop broadcast protocols are required for many applications including driver assistance systems. However, providing a low end-to-end latency has been very challenging. In this paper, we propose a protocol which can provide a fast channel access for broadcast traffic flows in VANETs. The protocol introduces new control messages to reserve time slots for the forwarder nodes and eliminate the hidden terminal problem. By providing a contention-free multi-hop forwarding scheme based on reliably generated forwarding backbone, the protocol can provide low end-to-end delay and high packet dissemination ratio. The theoretical analysis and simulation results demonstrate the advantage of the proposed protocol over other existing alternatives.

Multi-hop data dissemination in vehicular ad hoc networks (VANETs) is very important for the realization of collision avoidance systems and other many interesting applications. However, designing an efficient data dissemination protocol in VANETs has been a challenging issue due to vehicle movements, limited wireless resources and lossy characteristics of wireless communication. In this paper, we propose a protocol which employs intra-flow and inter-flow network coding to reduce the protocol overhead as compared to traditional protocols. The protocol also can improve the packet reception probability at the receiver nodes by using the network coding. Therefore, the protocol can provide a lightweight and reliable solution for data dissemination in VANETs. We use theoretical analysis and computer simulations to show the advantage of the proposed protocol over other existing alternatives.

Many routing protocols in vehicular ad hoc networks (VANETs) utilize location information to find a route to the destination. However, tracking the location information of other nodes is very challenging in highly dynamic VANETs. We propose a location service which can provide location information with low overhead and low delay. The location service periodically disseminates the location of each vehicle to 3-hop distance for every second with very low overhead. By eliminating location errors by taking account of the velocity of a vehicle, the proposed protocol can provide accurate position information. The location service also provides a lightweight location query mechanism for longer distance destination nodes. We show the effectiveness of the protocol by using theoretical analysis and computer simulations.

In vehicular ad hoc networks (VANETs), designing an efficient routing protocol is particularly challenging due to the vehicle movement and lossy wireless channel. A packet can be lost at a forwarder node even when a proper node is selected as the forwarder. In this paper, we propose a loss-tolerant scheme for unicast routing protocols in VANETs. The proposed scheme uses multiple forwarder nodes to improve the packet reception ratio at the forwarders. The scheme uses network coding to reduce the number of required transmissions, resulting in a significant improvement of end-to-end packet delivery ratio without increasing the message overhead. We show the effectiveness of the proposed scheme by using both theoretical analysis and computer simulations.

Point-to-point data delivery in Vehicular Ad hoc NETworks (VANETs) has been a challenging issue due to the vehicle movement, limited wireless resources and lossy feature of wireless channel. In VANETs, due to the frequent topology changes, traditional ad hoc routing protocols incur a high overhead for the route maintenance. In this paper, we propose a new approach to route data messages in VANETs. The proposed protocol uses dynamically generated backbone vehicles to forward data messages. The protocol generates the backbone by using only hello messages. The protocol selects the backbone vehicles by considering vehicle movement dynamics and link quality between vehicles. As a result, the selected backbone vehicles generate a reliably connected network. By using packet forwarding with the backbone nodes, the proposed protocol can reduce the message overhead and MAC layer contention time at each node while maintaining a high packet delivery ratio. We show the effectiveness of the proposed protocol with both theoretical analysis and computer simulations.

Efficient data dissemination in Vehicular Ad hoc NETworks (VANETs) has been a challenging issue due to vehicle movements, limited wireless resources and lossy characteristics of wireless communication. In this paper, we use dynamically generated backbone vehicles to disseminate information. The proposed protocol selects the backbone vehicles by considering vehicle movement dynamics and link quality between vehicles. The proposed approach can significantly reduce the MAC layer contention time at each node while maintaining a high packet dissemination ratio. We show the effectiveness of the proposed protocol by using theoretical analysis and computer simulations.

In vehicular ad hoc networks (VANETs), a multi-hop broadcast protocol is required to disseminate traffic warning information. Reducing broadcast message overhead while maintaining a high dissemination ratio is a very challenging task. In this paper, we study how to improve the performance of sender-oriented broadcast protocols using network coding. We propose a scheme which uses network coding to improve the packet dissemination ratio without increasing the message overhead. In the proposed scheme, the source node specifies two relay nodes. With cooperation between two relay nodes, the proposed scheme significantly increases the packet reception ratio by utilizing the broadcast nature of wireless channel. We show the effectiveness of the proposed scheme by using both theoretical analysis and computer simulations.

Wireless sensor networks (WSNs) can be used for a variety of applications. For many applications, a high reliability and low delay are required. Due to lossy feature of wireless channel, providing a reliable communication is very challenging. The most frequently used approach for providing the reliability is to use the acknowledgement based retransmission mechanism which increases the end-to-end delay especially when the number of hops from a sensor to the sink node is large. In this paper, we propose a redundancy-based approach to provide a high reliability while maintaining a low end-to-end delay. The proposed mechanism uses a redundant transmission when a link is unreliable or the end-to-end delay requirement is strict. We implement the proposed mechanism on a wireless sensor network which consists of IRIS motes, and evaluate the performance of the proposed mechanism.

Vehicular ad hoc networks (VANETs) can be used for the purpose of driving assistance, environment monitoring and entertainment. However, due to the vehicle movement, limited wireless resources and lossy feature of wireless channel, providing a reliable multi-hop communication in VANETs is particularly challenging. In this paper, we propose a VANET routing protocol which learns the optimal route by employing a fuzzy constraint Q-Learning algorithm. The protocol uses a fuzzy logic to evaluate a wireless link is whether good or not by considering multiple metrics of signal strength, available bandwidth and relative vehicle movement. Based on the evaluation of each wireless link, the proposed protocol learns the best route using the route request messages and hello messages. Upon reception of a route request message, each node maintains an evaluation value for each possible next hop node. In this way, the protocol can choose the best route, which is difficult to acquire in a typical reactive routing protocol. We show the effectiveness of the proposed protocol by using computer simulations.

Summary form only given. M. Crochemore et al. introduced a two-pass lossless data compression scheme called data compression using antidictionaries (DCA) (see Proc. IEEE, vol.88, no.11, p.1756-68, 2000). DCA finds some words (minimal forbidden words) that never appear in the text to be compressed, and chooses a subset of minimal forbidden words as an antidictionary (AD). We develop improved DCAs in two ways. (1) We propose an improved DCA using, instead of the AD, predictable dictionaries made up of the words whose last symbols are uniquely determined by their prefixes. The good properties of the original DCA hold in this extension. (2) We present an algorithm to construct the AD (or predictable dictionary) by using a suffix array of the text. We can reduce the amount of memory necessary to construct an AD by using the suffix array. Moreover, by applying a suffix array instead of a suffix tree, we can exploit the relationship between the suffix array and the BWT (Burrows-Wheeler transform), giving us the chance of choosing between DCA and the Burrows-Wheeler compression algorithm (BWCA).

The growing popularity of IEEE 802.11 has made wireless LAN a potential candidate technology for providing high speed wireless access services. Also, by supporting Mobile IP, wireless LAN can meet demands for expanded wireless access coverage while maintaining continuous connectivity from one wireless LAN to another. In the Mobile IP procedure, mobile node movement can be detected from advertisements of foreign agents that differ from the previously received advertisement and the new "care-of" address is registered with the home agent. However, user packets are not forwarded to the new foreign agent until registration is completed and this interruption may degrade the quality of service especially in real-time applications such as audio and video or may lower the TCP throughput due to retransmission timeout. To tackle these issues, we propose a new low latency handoff method, where access points used in a wireless LAN environment and a dedicated MAC bridge are jointly used to alleviate packet loss without altering the Mobile IP specifications. In this paper, we present the design architecture of the proposed method and evaluate its performance in an actual network environment to verify the effectiveness of our approach.

Recently routing protocols for QoS aware multicast have been actively studied, but there are few studies focusing on the scalability of link state advertisement when the available bandwidth of a link is updated along with the QoS aware multicast tree construction. This paper proposes a new QoS aware multicast routing protocol that is scalable in terms of the link state advertisement exchange. Our protocol has the following features: (1) a multicast network is divided into domains, and the advertisement of information on links within a domain is limited within the domain; (2) among the border multicast routers, only the link state information of interdomain links is advertised, so that the number of link state advertisement messages is drastically reduced; (3) when a multicast tree spreads over multiple domains, the tree construction needs to be performed without information on links in other domains, and it is possible that the construction may fail. In order to cope with this problem, the crank back mechanism of tree construction is introduced. This paper describes the detailed procedures and the message formats of our protocol. It also describes the evaluation of the number of exchanged link state advertisement messages and shows that our protocol can reduce the number by the order of 1/(number of domains) compared with conventional protocols.

It is widely recognized that IP-based mobile network will be a dominant trend and that the address starvation problem and scalable mobility management for mobile nodes are important issues for mobile IP networks. In order to cope with these issues, we propose an approach to realize mobile IP network supporting private addresses for mobile nodes. Our approach introduces regional registration of mobile nodes (Hierarchical Mobile IPv4) and coordinates NAT and DNS functions with the mobile IP protocol. It enables a mobile node to be assigned a global address temporally in a visited network and to accept a call initiated by a correspondent node connected to the global IP network. This paper describes the detailed design of our approach.

Presents the wide angle foveated vision sensor (WAFVS) system with a special optical lens, designed by mimicking a human eye, and flexible parallel processing function, examined and advanced by the author. The WAFVS system is applied to navigation of an autonomous mobile robot. As a rational execution of the system, the authors have carried out experiments of obstacle avoidance. 3D information for obstacle avoidance and locational information of the mobile robot are acquired from central vision with high accuracy and peripheral vision with less pixels, respectively Cooperation between them has improved quality of navigation.

The mobile IP data communication is widely spreading. Accordingly, it is pointed out that the number of IP addresses in IPv4 will be short if every mobile terminal has its IP address. In order to solve this address starvation problem, we propose an approach to realize mobile IP protocol by assigning a private IP address to a mobile terminal. It installs the foreign agent and home agent with network address translator (NAT) function, and it coordinates domain name server (DNS) procedure and NAT function in order to allow a correspondent node to make a connection to a mobile terminal. This paper describes the detailed design of our approach.

Recently audio and video delivery services are widely spread in the Internet. In order to deliver these data to multiple receivers at the same time, the multicast technologies are indispensable. In such a situation, the performance analysis of multicast traffic will be important in order to design and operate the Internet. Multicast traffic is controlled by its own routing protocol and the multicast routing protocol is more complex than conventional unicast routing protocols. In this paper we propose a new multicast performance analyzer considering distance vector multicast routing protocol (DVMRP) and protocol independent multicast-sparse mode (PIM-SM) routing protocols. It captures messages of a multicast routing protocol as well as multicast IP datagrams. It also analyzes DVMRP and PIM-SM messages in order to investigate the behaviors of multicast IP datagrams and measures the statistics of multicast traffic in detail. This paper describes the detailed design of the multicast performance analyzer and the results of analyzing multicast datagrams transmitted over networks.

Satellite communication is able to provide wide bandwidth, and satellite-based Internet access is expected to be a high speed Internet access method of the next generation. However, the propagation delay of a satellite link degrades the TCP throughput. The reason for this problem is that TCP performs window based flow control and most communicating hosts use the default window size such as 8 kbytes through 24 kbytes. To deal with this problem, we propose a TCP gateway for satellite-based Internet access. The communication throughput of TCP is improved without any modifications to equipment and terminals of subscribers by introducing this system only at a satellite Earth station. In this paper, we describe the protocol architecture of the TCP gateway and its performance by comparing with conventional methods. The results of a performance evaluation show that the proposed TCP gateway can provide more than 20 times higher throughput than communication without it over a link with 6 Mbps bandwidth and 350 msec round trip time.

Most of current video retrieval systems use video transfer protocols such that servers simply transmit video packets at the same rate as clients play them. If any packets are corrupted during transmission, they will be lost and cannot be recovered by retransmission. In video retrieval systems however the video data are stored in servers and clients can prefetch them prior to playing. So, it might be possible for the video retrieval systems to make corrupted video packets retransmitted before the play-out deadline. However, the application of existing reliable protocols causes problems such that, if a packet does not arrives before the deadline due to retransmission, the packets following it will not be delivered to the upper layer even if they have already arrived. We propose a new video transfer protocol for video retrieval systems over an ATM network which provides video data prefetch, flow control for the video buffer, selective retransmission with a skipping function for video packets that are late for the play-out deadline, and a resynchronization function for the video buffer. We have implemented an experimental system using our protocol and evaluated the performance. The results of the performance evaluation shows that the proposed protocol decreases the number of unplayed video data to less than 1/70 compared with the conventional non-retransmission protocol when random bit errors with a BER of 10/sup -6/ are inserted in an ATM network.

Along with the rapid progress of optical technologies, the transmission speed of LANs and public networks has been increased significantly. As a result, it has become possible for computers distributed geographically to communicate with each other with high throughput. However, the current protocols such as TCP/IP have some problems, especially the performance through long distance and wide bandwidth networks. Therefore, new protocols with new data transfer algorithms are required. In this paper, we describe an implementation of a high speed transport protocol by a user level library which interfaces to UDP/IP. This method uses only functions commonly provided by UNIX operating systems, and therefore, allows a new protocol to be developed easily and to be ported to other UNIX workstations easily. Our library called the transport library realizes the coordination of buffer managements in the application and the library, and low overhead and prompt handling of receive and timer interrupts in order to achieve high performance. Our implementation results show 32 Mbits/sec over an ATM network whose effective transmission speed is 36 Mbits/sec, regardless of the propagation delay from 0 to 200 msec. These values of throughput are better than those of the in-kernel TCP programs.