Hiroei Imai

OLSRv2 implementation and performance evaluation with link layer feedback

OLSRv2 is being standardized in the IETF MANET (Mobile Ad hoc Network) working group. OLSRv2 uses the common packet format, that is also being standardized in the MANET WG. It is necessary to validate the OLSRv2 protocol specification by implementing OLSRv2. In addition, OLSRv2 has a great capability to reduce message size compared to OLSR. This is due to address compression. The change of control message size directly affects the total network performance, but how much it affects the various parameters are dependent on the network scale, number of nodes, and address compression implementation. In this context, we have implemented the OLSRv2 protocol, which can run as a real-time protocol or in the QualNet simulator. In addition, we added link disconnection feedback function from MAC layer to OLSRv2 modifying wireless LAN device driver. In this paper our OLSRv2 implementation detail is introduced, and OLSRv2 performance is compared with OLSR by using both a 50 node testbed built in Niigata university and also in the Qualnet simulator. In addition, IP address compression effect is analyzed in the simulator, and the performance of OLSRv2 with link layer disconnection feedback is evaluated in the testbed.

A synchronization mechanism in networked virtual environment

We describe the design of a group synchronization mechanism for a local area network virtual environment and introduce a step synchronization mechanism. We use a football game to evaluate this mechanism. In this football game, users can share a virtual space where they can move around, dribble and shoot. To achieve synchronization among users, a client of the game exchanges data through a server within a certain period time. A problem of such a system is that all users should share the space in the same time for justice competition. But because of the different capacity of computers and the time cost of the communication between clients, it is difficult for all clients to update the virtual space simultaneously. In our systems, we introduce a waiting time synchronization mechanism. To evaluate our proposed architecture and mechanisms, we make a series of experiments in our local area network and then build and analyse the model of our system.

An evaluation method for network systems based on delay jitter analysis

This paper proposes a method for evaluating network systems based on delay-jitter analysis using generalized stochastic Petri nets (GSPN). Systems are modeled by GSPN and tagged client approach. The mean delay time and its variance for systems are calculated by using equations derived from a Markov chain of the GSPN model. Systems can be evaluated statistically by the obtained values.

Web-GIS-based emergency rescue to track triage information — System configuration and experimental results

In emergency situations, first responders must possess the means to communicate vital information, such as the number of patients requiring immediate medical attention, -and their precise locations, as quickly and efficiently as possible, to fire and rescue-, and police departments, as well as city officials. For these situations, we developed a mobile terminal incorporating a GPS, as well as an RFID reader. The objectives of our current research are to develop; 1) - a mobile terminal for use in disaster areas; 2) - a robust “Web-GIS” platform to disseminate patient information to medical teams, during a disaster.

An evaluation method for delay time and its jitter of WLAN using a GSPN model

This paper proposes a method for evaluating mean delay time and its standard deviation (jitter) of wireless local area networks (WLAN) using Generalized Stochastic Petri Nets (GSPN). The WLAN is modeled using GSPN and the mean delay time and its jitter are calculated using equations derived from the Markov chain associated with the GSPN model. The method is applied to evaluate delay time and its jitter for 802.11e WLAN. The results reveal that the values calculated based on the equations agree well with the values obtained from simulations.

A method for analyzing a queuing network by the tagged‐task model

This paper considers faults in distributed real-time systems modeled by queuing networks; in particular, a fast method of analysis of transient variation of system performance is proposed. This method involves analyzing queuing networks by means of the tagged-task model. Such an analysis requires repetitive determination of the limit-state probability at varied initial values; however, the computation time can be reduced by using the absorption probability (the probability of arriving at the absorption state). In addition, a fast algorithm is proposed to calculate absorption probability, in which the state set is split into cosets according to arrivability, and the cosets are replaced by representatives as soon as the state probability becomes low. Finally, the effectiveness and accuracy of the proposed method are verified by actual examples.