A message protocol called message queuing telemetry transport (MQTT) is being used in large-scale energy-efficient communications. However, even when using MQTT, if the network quality and capacity are insufficient, especially when there are many subscribers, nodes may fail to receive messages. Therefore, we propose a new communication control mechanism, eXchanging attributes of transmission uniformity (Xatu). The goal of Xatu is to establish a reliable new method that can compensate for message loss even in long-time and large-scale environments. Xatu sets up a state called bridge, and a conventional MQTT subscriber switches to a bridge. Xatu allows messages to be sent to all subscribers without missing messages.

The widespread adoption of USB Type-C technology has been remarkable in recent years. Electronic devices such as smartphones, tablets, and computers now utilize Universal Serial Bus (USB) Type-C connectors in compliance with the USB Power Delivery (USB-PD) specification for power transmission and reception. Although USB Type-C devices are equipped with a function of auto-notification of their IDs, the function is not always guaranteed to work; we cannot rely on the ID notification. Relying exclusively on this data for comprehensive device identification presents a significant obstacle. Based on the ground, this study introduces an approach to identify USB-C-connected devices by analyzing the power waveform in USB PD negotiations, a distinctive feature of USB Type-C. The goal is to identify these devices regardless of their charging rates or circuit designs. Furthermore, our proposed method was validated using a virtual grid hub (VG-Hub) with seven USB-PD-compliant Type-C ports oriented toward renewable energy. The proposed method using VG-Hub showed excellent performance, achieving 99.25% accuracy, repeatability, and F1 score over the previous method. This demonstrated the effectiveness of the USB Type-C connected device classification method independent of device state.

In recent years, vehicle-to-vehicle (V2V) communications are used not only for safe driving assistance such as collision avoidance but also for advanced autonomous driving using dynamic maps and remote control. Ultra-reliable low-latency communications (URLLC) are necessary for safety-related functions, e.g. driver assistance and autonomous driving. Due to high mobility, V2V communication must be performed in a variety of communication environments. However, millimeter wave (mmWave) communications, an enabler of URLLC, are greatly affected by the environment, e.g. the terrain, density of vehicles, etc.. This paper proposes an environment-dependent throughput estimation method for mmWave V2X communications. Roadside units (RSUs) collect information on the throughputs of their nearby vehicles and calculate their distribution model with the Bayesian approach. The proposed method provides a regression scheme to estimate distribution models of the throughput of the area without RSUs. The simulation evaluation validates that the beta distribution fits well for the throughput of mmWave vehicular communication and that the regression scheme can estimate throughput models of the area without RSUs.

We developed a prototype of a virtual grid hub (VG-Hub), which is a device for controlling direct current (DC) power flow by utilizing the characteristics of USB-PD. In a network of interconnected VG-hubs, deciding the entire power distribution path every time a load changes results in disruption of the power flow during operation as well as high-cost of recomputing over the entire network. Therefore, we propose Minimum-Hop Power-Path Routing (MHPPR), which determines a new power flow only at the hub where the load fluctuates. In the MHPPR, the route that minimizes the total number of hops from the power supply source to the load is determined to achieve the goal of the nearest power supply. In this study, we show that the power flow is more efficiently determined compared to the case of recalculation of the entire network when the load changes.

Power delivery (PD) to computing and sensing devices in an indoor environment is as important as data communication between them. We are developing a USB-PD-based DC power supply system called VGHub. As the power loss at each input and output port of VGHub depends on the incoming or outgoing power at the port, the power distribution among all the ports needs to be optimized to maximize the power efficiency of VGHub. In this poster paper, we describe the formulation of a power distribution control in VGHub.

Device-to-Device (D2D) communication is expected to be a promising solution in next generation cellular technologies to efficiently provide connectivity over a wide area with low-cost. This paper proposes a gamified participatory D2D (GP-D2D) communication for encouraging mobile users to appropriately activate access point (AP) functions with their mobile devices. It is implied that gamification is an effective approach for encouraging autonomous D2D communication if the game-settings such as gain mechanisms are appropriately defined.

We have developed a robot that voice-casting during the rehabilitation considering the emotion of the people. Firstly, we have discussed how to motivate rehabilitation by grasping the feelings of the patient and speaking from the results as it is called "supportive voice is important". As a method of grasping the patient's feelings, emotional analysis using biometric information was decided. Biological information is activity information of the body unconsciously issued by a person. Several methods for identifying emotion using such information has been proposed. In the research, we conducted emotional estimation using a pulse sensor to acquire the feelings of the person in motion, and designed and implemented a voice-casting robot that makes voice calls. As a result, it was possible to confirm the effectiveness of a voice-casting robot that performs supportive actions while using emotions.

We explore the possibility of detecting person's mood with the usage pattern of mobile applications. Towards this ultimate goal, we first examine the relationship between LF/HF values in heart rate and the CDR (Call Detail Record) logs. Our evaluation result shows that different LF/HF values correspond to different types of mobile applications.

Presents the introductory welcome message from the conference proceedings. May include the conference officers' congratulations to all involved with the conference event and publication of the proceedings record.

This poster paper describes our trial of Quality of Service (QoS) control using packet classification based on the time sequence of the beginning of flows. In contrast to the classification of flows using the total sequence, utilization of only the first few packets for classification is difficult. We explore this approach with several different time windows both at the learning phase and at the identification phase.

Meetings are considered to be indispensable for decision making of groups, and thus efficiency is required for meetings. However, it is difficult to discuss the efficiency of meeting in a quantitative way. Based on this background, we define metrics to quantify the meeting activity and we implement a system to evaluate the metrics called KAIHUI. A smartphone is used as a KAIHUI client to record meeting audio. Then a KAIHUI server analyzes and calculates activeness according to the proposed metrics. In this demonstration, we show the basic operations of KAIHUI using a smartphone.

Recent empirical studies have shown clear evidence that wireless links are not independent and that the packet receptions on adjacent wireless links are correlated. This finding contradicts the widely held link-independence assumption in the calculation of the core metric, i.e., the expected number of transmissions to the candidate forwarder set, in opportunistic routing (OR). The inappropriate assumption may cause serious estimation errors in the forwarder set selection, which further leads to underutilized diversity benefits or extra scheduling costs. We thus advocate that OR should be made aware of link correlation. In this paper, we propose a novel link-correlation-aware OR scheme, which significantly improves the performance by exploiting the diverse low correlated forwarding links. We evaluate the design in a real-world setting with 24 MICAz nodes. Testbed evaluation and extensive simulation show that higher link correlation leads to fewer diversity benefits and that, with our link-correlation-aware design, the number of transmissions is reduced by 38%.

In this paper, we propose a novel vibration-based communication system for Bluetooth-equipped smartphones. Smartphones are commonly utilized through the display; however, sometimes users would like to exchange pieces of information with nearby peers, without shifting their focus from current task. Additionally, this enables communication in cases without visual or sound contact. For this purpose, we developed a novel application called Hand-to-Hand on Bluetooth Communication (H2BCom). We use the common gestures of tapping and touching the smartphone display for sending a Morse coded message over a Bluetooth channel. On the receiving side, the Morse coded message is presented as vibration of the smartphone. We show the design, implementation and evaluation of H2BCom on Android phones. In our user study, we found that using the Morse code was difficult for beginners, but the users'skill improved after taking a tutorial of the Morse code.

In this research, we designed and implemented Real-World File System (RWFS), which can manage files as if we can put them onto or pick them up from the places of the real world. RWFS regards the places of the real world as directories of the file system by associating a directory with a place. We create directories called Real-World Directory (RWD) which forms a hierarchical structure to reflect the natural property of places. In addition to the conventional access rights of read, write, and execute as implemented in other file systems, RWFS accommodates utilizing location information of the target user in access rights; RWFS can decide whether or not the user can access to a particular file or directory based on the user's location. Therefore, accessible files for a user change depending on the user's location. This mechanism enables creating information that can be read or written by users who physically stay at a particular place. We evaluated this system by measuring turnaround time to operate the file system together with simulation.

We study an instant messaging system between two smartphones, without the need of visually following the screen of the smartphones. In the sending side, a Morse-code-type touchscreen input is used to encode the message and a vibration in the receiver side to perceive the message.

This paper proposed an optimized strategy of the incentive mechanism for participatory sensing network on the basis of Sense Util which is our previous research work. For optimizing, the strategy considered the possibility of that some users actually cannot participate the current sensing task, so in order to avoid unnecessary energy and bandwidth consumption on server end, users were classified into different subsets according to their position, and server distributed the sensing tasks directionally. To evaluate the performance of the strategy, we conducted simulation study, and the results showed that the optimization work is energy efficient.

We demonstrate interoperable mobile agents for language- and platform-independent wireless sensor network programming, with low-power resource-constrained embedded devices as static nodes and Android-based smartphones as mobile nodes, over disparate networks: 6LoWPAN and Wi-Fi. Representational state transfer architectural principles are applied in agent composition, control and migration and exposing the system resources to the Web: the devices, agents, sensor data, tasks and data processing results. The adaptable agent composition includes the task code in any programming language, the agent migrates according to a resource list and the state, i.e. the intermediate task result, represents the agent as a system resource. Mobile agents are then utilized in two tasks: first to collect light sensor data cooperatively in location, saving the mobile node battery whenever possible, and secondly the magnetometer sensor data with the scanned Wi-Fi access points' signal strength is used to detect groups of mobile nodes moving in the same direction in real-time.

Pervasive smartphones that embed a variety of sensors enable us to sense and learn about the physical environment around us, even the society we live in. However, the sheer volume of data collected through participatory sensing can deeply hamper the performance of various applications (e.g., data processing time and transmitting cost). In this paper, we proposed a method to reduce the volume of sensor data while preserving the information content of the original data. Our proposed method REPresentative Sense (REPSense) borrows the idea from electoral system. Hence, after data reduction, output data (target) can represent the original data (source) as parliament members are elected to delegate their constituencies. This method can compress multi-dimensional data with arbitrary distribution. We evaluated our method using real-world datasets collected by 12 users over a period of 4 months. The results show that our method outperforms state-of-the-art by comparing baseline methods in terms of data divergence and data processing performance.

By exploiting reception diversity of wireless network links, researchers have shown that opportunistic routing can improve network performance significantly over traditional routing schemes. However, recently empirical studies indicate that we are too optimistic, i.e. diversity gain can be overestimated if we continue to assume that packet receptions of wireless links are independent events. For the first time, this paper formally analyzes the opportunistic routing gain under the presence of link correlation considering the loss of DATA and ACK packets. Based on the model, we introduce a new link-correlation-aware opportunistic routing scheme, which improves the performance by exploiting the diverse uncorrelated forwarding links. Our design is evaluated using simulation where we show (i) link correlation leads to less diversity gain, (ii) and with our link-correlation-aware design; improvement can be gained. We also provide a unique model to generate strings of randomly correlated receptions.

In this paper, we present an integrated framework, named NaviComf, which constructs pedestrian navigation systems for comfort in varying environments by using multi-modal sensing technologies. With NaviComf we aim to systematically provide solutions to three key problems: (1) how to build the environmental data warehouse (EDW) which works as an infrastructure providing comprehensive and predictive environmental information, (2) how to integrate heterogeneous environmental information from multi-modal sensors into an aggregate value which facilitates further processing, and (3) how to determine the optimal path plans in environments which are varying continuously. In NaviComf the multidimensional data model and data prediction method are applied to build the EDW. Then a novel multi-factor cost (MFC) model is proposed as the fundamental concept to integrate the multi-modal sensor data. Based on the former two solutions, the optimal path planning (PP) problem is solved in a time-dependent network by applying a dynamic programming method. In the evaluations of NaviComf, sensor data for temperature, humidity, and pedestrian traffic flow have been gathered in real environments and a prototype system has been implemented with the data. Evaluations are conducted by using the prototype system and the results show that NaviComf can efficiently navigate pedestrians through more comfortable paths as compared to the traditional navigation method.

Waiting in a long queue is a cause of stress which affects people's life, work, and so on. The purpose of this paper is to avoid queues of restaurant during lunch time. To achieve the purpose, we develop a Qviz system which is able to visualize queues of remote restaurants. Users can ask for queue information of any restaurants by using a Qviz client which is implemented on smartphones. By applying a Markov process on historical movement, Qviz server predicts futuristic movement of users and selects potential reporters for the requested restaurant. We have implemented the Qviz system to validate the feasibility as well as usefulness of the system.

To seek and collect useful sensor data in a participatory sensing environment, participants should be able to coordinate their activities in a timely manner. However, existing systems deal separately with the "preparation time" to define the goal and method of sensing, and the "sensing time" in the field. Therefore, participants cannot easily modify the sensing method, including the collaboration setting, once they are out in the field. In this demonstration, we will present a system called Kitokito, which allows participants to easily create small sensing tasks, and iteratively modify the collaboration and sensing method during the "sensing time."

In this paper we describe a prototype system of identifying environment condition utilizing signals emitted by people. Many people move around in many places such as urban and mountain areas. If each person emits information about identifying the state of the place where he/she and all the information is collected to one site, we can know the state of an area. Based on the idea, we have extended WINFO, a previously developed system, to accommodate reading people's walking conditions obtained by pressure signals at the people's feet. We show an architecture of the prototype system and a result of acquiring walking patterns in an urban area.

Recent mobile devices are integrated with various kinds of sensors, thereby allowing people to capture what stationary sensing devices cannot easily acquire. We term the systems that exploit the ubiquity of the users of such devices Human Probes. To realize a Human-Probe environment, our research group has examined the usefulness of pressure sensors embedded in shoes [2]. In this demonstration, we present our recent work that extends our previous research on embedded pressure sensors by considering complimentary uses of accelerometers so as to measure walkability in our everyday spaces. Pressure sensors and accelerometers are similarly useful for capturing the motion of pedestrians; however, the close examination of the signals from both sensors reveals the strengths and the weaknesses of each, and suggests the possibility of their complimentary use to support Human Probes.

Sensor networks using mobile robots have recently been proposed to provide more flexible and efficient sensing. However, mobile robots in a practical world have many accidents with actuator or communication devices especially in their traveling to the destination. Moreover, in the practical world, there are many obstacles and bad conditioned area for both wireless and movement of mobile robots. In this paper, we introduce a practical scheme for delivering data with concerning a practical world issues.

Sensor networks using mobile robots have been proposed to provide more flexible and efficient sensing. One of the key challenges under this paradigm is a management of transferring a huge amount of data. In this paper, we propose a model and protocol for session control exploiting controlled mobility in multi-robot sensor networks (MRSNs) to transfer the huge amount of data efficiently. Since a communication in MRSNs is mainly provided by a physical movement of the mobile node, the performance of the session heavily depends on this movement. However, if a node initiating the session can utilize sufficient amount of nodes, the performance of the session significantly depends on the wireless communication. In this paper, we propose a suitable method of session control which is determined the balance between movement and wireless communications based on local information such as the location, number, maximum-velocity and buffer-size of surrounding nodes. WISER/s also takes a system policy of either delay minimization or energy efficiency into consideration. In this paper, we describe a method of how to initiate, terminate and manage the session including dynamic selection of optimal nodes' formation. We evaluate the performance of WISER/s using mobile robots which are equipped with MICA2 mote and comparing with non-optimized method. The experimental results demonstrate that WISER/s achieves better performance than non-optimized method.

Camera networks have been paid much attention in sensor networks since those network are useful to visualize a phenomenon sensed by other sensors for temperature, humidity, and light. When a user selects a point of an area deployed cameras in an application, a geographic routing is best used as a routing of the camera network. In conventional geographic routing, the destination of a message should be the location of a node. However, this is not suitable for sensors that cover a wide or directed sensing area such as cameras. To cope with this problem, we propose a modified geographic routing scheme called SenriGan. SenriGan accommodates specifying a sensed point as a destination instead of using a location of a node. In this demonstration, we show a prototype system of SenriGan.

Querying in heterogeneous sensor networks is a challenging research issue due to a variety of real-world queries depending on users' preferences. Examples of queries are weather, nearby restaurants, navigation, etc. Users may ask for a breezy path starting from distinct points to distinct train stations. Sensing data collected from wide areas (city or country level) are needed to provide the real-world search as a service for users. Therefore, another challenge is a collaboration of heterogenous sensor networks because deploying sensors in wide areas is impractical. SensorMap [1] collects sensing data from independent sensor networks by allowing data owners to publish their data on the web. Sensing data from all owners are sent to a centric storage in SensorMap. However, distributed data storage is likely to be an efficient solution comparing to a centric storage in which bottleneck always occurs.

In this paper we propose a design of application programming interfaces (APIs) for configuration of multi-robot sensor networks (MRSNs). Such networks have unique aspects: intentional mobility and delay tolerance. These aspects limit the applicability of conventional approaches proposed for mobile ad-hoc networks (MANETs). APIs for configuration of MRSNs must take these aspects into account. In addition, an application program should be transparent from changing of physical devices such as wireless devices. In this paper we describe the design and prototype implementation of APIs for configuration of MRSNs.

Life rhythm analysis for elderly people has recently been paid mach attention in many countries with long life expectancy. Wireless sensors attached to a human body are considered useful in automating the life rhythm analysis. We propose a system of such a monitoring and analysis system. This system has two advantages: unconscious monitoring and continuous analysis. We receive data from a mule with wireless sensors. The mule consists of pressure sensors connected with Mica2 Motes and sensed data is analyzed to extract a user's life rhythm.

Extracting human's health condition using wireless sensors impose a challenge in the balance between data storage and CPU power. Taking available resources on nodes into consideration, we apply Step-wise Context Extraction (SCE) to AoK mule system [4]. SCE compresses data obtained at the mule into a context as the data is forwarded. In this demonstration, we show how the raw data is converted into the context in the AoK system.

No abstract available.

In this paper we propose a new scheme of managing resources on public devices used by private devices. Due to the advancement of wireless LAN technologies, wireless hot spots are becoming popular in the cities. In such hot spots, we can expect that public devices such as large displays and printers be available in the future as well. Assuming that these public devices are used by anonymous group of users, there are several threats of group-secret information being exposed or unintentionally left on public devices. To overcome the problems, secure management of personalization association (SAPEA) is introduced. SAPEA has two fundamental mechanisms: accessible-zone based and soft-state management of public devices. In particular, files which are the fundamental resources in SAPEA can be extinguished even when they are being used to avoid exposure to illegitimate users. In this paper we describe the design and implementation of SAPEA on Linux PCs with Bluetooth.

This paper presents a novel effective scheme of configuring wireless personal area networks (WPANs), called master-driven connection control (MaCC). WPANs are based on a new wireless technology, which enables portable and mobile computing devices, and consumer electronic appliances to communicate with each other. Assuming that WPANs operate in a master-slave style, we exploit the information about master-slave relationships for identifying a network topology in an ad hoc fashion. Specifically, MaCC supports routing, providing the minimum-hop paths that cannot be obtained by flooding algorithms. In addition, it constructs the optimal topology on demand along the minimum-hop paths dynamically, because the performance of routing is dependent on network topologies. These functions need only a few control messages to achieve, and so can avoid excessive message propagation by flooding causing frame collisions in the WPANs. MaCC has several prominent features: self-direction of every node, adaptive formation of networks, and minimization of hop counts for routing control. In this paper, we describe the details of MaCC and analyze its overhead about initialization, routing discovery, and reconfiguration. The results show control messages propagated in a MaCC network at route discovery are reduced to less than one half of those in a network utilizing pure flooding.

This paper describes the design, implementation, and evaluation of a proximity-based dynamic path shortening scheme, called DPS. In DPS, active route paths adapt dynamically to node mobility based on the "local" link quality estimation at each own node, without exchanging periodic control packets such as Hello packets. Each node monitors its own local link quality only when receiving packets and estimates whether to enter the "proximity "of the neighbor node to shorten active paths in a distributed manner. Simulation results of DPS in several scenarios of various node mobility and traffic flows reveal that adding DPS to DSR and AODV (conventional prominent on-demand ad hoc routing protocols) significantly reduces the end-to-end packet latency up to 50-percent and also the number of routing packets up to 70-percent over DSR, particularly in heavy traffic cases. We also demonstrate the more simulation results obtained by using our two novel mobility models which generate realistic node mobility: random orientation mobility and random escape mobility models. Finally, simple performance experiments using DPS implementation on FreeBSD OS demonstrate that DPS shortens active routes in the order of milliseconds (about 5 ms).

This paper endeavors to present a scheme to detect and estimate bottleneck bandwidth along the path in the Internet. We have participated in the RIPE NCC's TTM project to perform one-way delay (OWD) and loss measurement from a host in our laboratory to other hosts in Europe and USA. TTM is an active measurement system, which has implemented the IPPM one-way delay (RFC2679) and one-way loss metrics (RFC2680). From measured delay, loss, and traceroute's data, we can know the path properties such as bandwidth, path rerouting, congestion between each host, and so on. Based on measured delay, we propose an algorithm called Estimating Bottleneck Bandwidth using Packet-pair (EBBP), to estimate bottleneck bandwidth. Our algorithm is based on Bolot's (1993) equation, but we use OWD instead of round trip delay. Every participated host uses a GPS receiver to avoid the problem of clock difference. We make a phase plot graph from measured delay, extract useful samples, quantize extracted samples, and find the intercept of the phase plot graph by EBBP. Finally, we can estimate bottleneck bandwidth along the path.

This paper presents a new routing scheme called estimated-TCP-throughput maximization based routing (ETR) scheme for mobile ad hoc networks (MANET). Many routing protocols have been proposed to build multi-hop networks in MANET. Most of these protocols select a path based simply on hop metrics, although the shortest path is not always the best path under the influence of radio link quality. We propose that the path should be selected with the maximum end-to-end TCP throughput because most of applications use TCP. In ETR, as a new metric for routing, we introduce an estimated TCP-throughput. A source node measures loss and delay for a path with probing packets periodically. The node estimates maximum TCP throughput from the expression of first approximation with those measured values, and exchanges a path dynamically so that the performance of the using path will be the best of all paths. This paper shows the, design and implementation of ETR. We add ETR to dynamic source routing (DSR) protocol in our MANET testbed, and evaluate ETR. In the case of 50% packet loss at DSR layer. ETR improves TCP throughput by 93% than unmodified DSR. ETR can select the path whose TCP throughput is maximum from the multiple paths to a destination.

This paper proposes a middleware for home networks, called Virtual Networked Appliance (VNA) architecture, in which the service description method and the Service to Service (S2S) communication mechanism are separated in an orthogonal way. Through the separation, VNA architecture solved the following two problems of existing middleware technologies: aspect violation and middleware fragmentation. In this paper, we first clarify the two problems and their relationship. Then, we describe the proposed middleware architecture as a solution from the viewpoint of the overall configuration and the S2S communication mechanism.

We propose an efficient route discovery scheme for mobile ad hoc networks called Hop-Wise Limited broadcast (HOWL). HOWL executes an efficient route discovery by predicting current location of destination using hop counts of previously used routes. Furthermore, we introduce characterized environmental indicators (CEI), namely node density, average hop count of route, and frequency of link failure, which characterizes real world environments with the constraint that parameters such as speed or transmission range are similar for every node in the network. CEI is also applicable to simulation environments. We have implemented a preliminary phase of HOWL as an extension to dynamic source routing (DSR), which uses network-wide broadcasts as a means of sending route request messages, on ns-2 network simulator. Simulations show that HOWL is especially effective when the node density is low, average hop count of route is short, or frequency of link failure is high where up to 10 % reduction in overhead and approximately 5 % reduction in latency were demonstrated.

In this paper, we present a new mobility-support model for applications, Application Module Request Broker (AMRB). We focus on two types of mobility: host mobility and application code mobility. These two types of mobility dynamically change the binding between applications name and location in the network. AMRB conceals these changes of banding to reduce a complexity in development of applications. In AMRB, we deal with mobile application codes that communicate with each other as Application Modules (AMs). AMRB provides AM's service transparent communication for applications by using a specifier which does not need to include any network location information. Furthermore, applications can use AM's service transparently of migration by exploiting location management mechanism. In this paper, we describe the design and implementation of AMRB and some evaluations. Also, we demonstrate a sample application that AMRB is effective for developing mobile sensor type applications.

This paper presents "OR2", an adaptive path tuning scheme for mobile ad hoc networks. In OR2, the active path adapts dynamically to node mobility without any link failures based on the local link quality. Most conventional routing protocols accommodate the change of network topology only when the link fails. Unless the movement of intermediate nodes leads to any link failures, they cannot adapt to the network topology even if other routes with less hop count become available. In contrast to these protocols, OR2 reduces the hop count of an active route while data packets are sent without link disconnection. Specifically, by introducing the notion of proximity that indicates the nearness of two communicating nodes, OR2 skips the upstream node in a proximity area and continues to shorten an active route as possible. For delay sensitive TCP flows, reducing the number of hops and path delay significantly improves the performance of TCP. We have implemented OR2 as an extension to DSR on FreeBSD. The experimental results have shown that OR2 is effective in enhancing TCP throughput and reducing end-to-end delay for all relevant flows.

A key challenge in packet scheduling over a wireless channel is to achieve effective throughput against bursty errors. Although there have been several proposals on packet scheduling for a wireless channel, they are only based on bi-modal channel states: good or bad. In this paper we propose a new packet scheduling scheme for wireless links based on the receiver's signal to noise ratio (SNR). The scheme is referred to as SNR-based packet scheduling (SPS). In SPS, outgoing packet flows are scheduled such that the flows with higher SNR values have larger weights in scheduling. SPS can achieve effectiveness by adopting a flexible mapping between weight and SNR. We present measured results of the relationship between throughput and SNR as well as the design and implementation of SPS. In our experiments, SPS has shown its effectiveness in enhancing total throughput for hosts with good and bad wireless connectivity over a wireless LAN.

We propose a scheme of rate control for continuous UDP flow with moderate fairness. First, per-packet relative one-way trip time (ROTT) of a UDP stream at a receiver on the Internet is investigated extensively, and it is found that spikes with successive plots, which we call spike-trains, often appear on a time-ROTT graph. Also, congestion-related losses are found to be strongly correlated only to the spike-trains and the path status is effectively identified by such spike-trains. Based on these observations, a rate control with moderate fairness using the path-status, PAth-STatus-based RAte control (PASTRA), is presented. The effectiveness of PASTRA in achieving moderate fairness for UDP streams on the Internet is demonstrated.

This paper proposes "MobileSocket" which realizes session layer communication continuity support for Java Applications towards the continuous operations for mobile applications. In the mobile computing environment where mobile hosts move around the network even during communications with the remote, maintenance of the communication continuity between the applications is significant. Not only mobility support but virtual circuit continuity support is required for communication continuity. Existing approaches have not provided the complete communication continuity for applications. "MobileSocket" is a user-level enhanced socket library written in Java, and provides library-based session layer mobility and virtual circuit continuity support for applications. Two mechanisms, dynamic socket switching (DSS) and the application layer window (ALW) were developed for MobileSocket and enable a simple implementation. The MobileSocket applications can be used in Java mobile applications and the agents, as well as for ordinary network applications. In this paper, after we clarify the communication continuity and existing approaches, we present the MobileSocket design, mechanism, and results of evaluation.

We propose the neighbor-state based queuing (NBQ) for improving the performance of flows sharing link bandwidth under various transfer protocols. Each router with NBQ informs the next upstream router of its link status. According to the received status, the NBQ dynamically sets the packet discard ratio of the non-adaptive flows. The NBQ reduces the wasted non-adaptive flows and provides available bandwidth for the adaptive flows. We have demonstrated dramatic improvements of the adaptive flow's throughput using our scheme through simulations.

We propose a new, efficient fast retransmission (EFR) scheme for wireless LANs. Wireless LANs are becoming popular and providing an efficient protocol over a wireless link is important. In our experiments with the 2.4 GHz WaveLAN, the poor TCP performance observed was attributed to frequent expiration of the retransmission timer. To avoid unnecessary expiration of the retransmission timer, we propose a scheme in which fast retransmission is performed efficiently. The proposed modification only affects a TCP sender, and our version of TCP where the change is interoperable with existing TCP implementations. The change is especially effective in wireless LAN environments, where we have demonstrated significant improvements in throughput, 10-15%, via experiments.

Continuous media communication requires timely delivery of data such as digital video and audio packets. Quality of Service (QOS) parameters specify the temporal and spatial characteristic of such continuous media data. To insure timely delivery of continuous media data, the system needs to minimize the communication delay by securing required processor and network resources. We have extended the Capacity-Based Session Reservation Protocol(CBSRP), which was proposed to realizing predictable real-time communications, to support dynamic control of QOS. We have implemented a QOS control scheme by which the network dynamically adjusts the allocations of network bandwidth on a Fiber Distributed Data Interface(FDDI) network.