Tomoichi Ebata

Synchronous distributed wireless network emulator for high-speed mobility: Implementation and evaluation

Wireless network emulators provide various mobile node dynamic conditions and wireless links for real implementation of protocols to be evaluated based on user-defined mobility scenarios. The target of our proposed emulator is IP-based protocols for large-scale mobile wireless networks composed of a large number of high-speed vehicles. The requirements imposed by our target are high scalability and high-speed mobility emulation while maintaining high accuracy for many hours. To satisfy this, we first introduce a distributed architecture then propose an approach called “time-based wireless link emulation.” In this approach, the mobility scenario is converted into a wireless link schedule, and each distributed processor emulates a wireless link based only on the schedule and its clock, which is precisely synchronized with the other processor clocks by using IEEE 1588 PTPv2. Intensive experiments on the performance of the latest version of our prototype emulator show that (i) high-speed mobility emulation up to 200 m/sec with 0.1 M accuracy, (ii) packet delay emulation with 100 μsec accuracy, and (iii) time-stamps based measurement of elapsed time spent by test nodes with 100 μsec accuracy have been achieved. Our proposed emulator functioned well in an experiment with a simple protocol implementation for car-to-car/infrastructure communication.

Symbiotic Autonomous Decentralized System on Cooperative Distributed Scheduling

Currently, System of Systems approach becomes more and more important in the field of social infrastructure to adapt various user needs flexibly and efficiently. Symbiotic autonomous decentralized systems is one of System of Systems. In this system, optimizations of both entire system and each system are expected to be achieved simultaneously. However, the symbiotic operation based on free will of each system doesnt go well, because each system has its own key performance indicator and tries to pursue the indicator. In order to promote symbiosis in the systems, we developed Cooperative Distributed Scheduling. As a result of verification with a simulator, we confirmed the total key performance indicator of each system improved by about 17%.

Performance evaluation of synchronous distributed wireless network emulator for high-speed mobility

The IEEE 1588 Precision Time Protocol Version 2 (PTP v2) standard was developed to establish precise synchronization protocols for distributed nodes, and thus facilitate the development of distributed time-based systems. As an example of an applied system, we developed a distributed wireless network emulator that permits precise and stable synchronized time-based wireless link scheduling. In our system, each agent node simply emulates schedule-based wireless links without exchanging control messages with any other nodes. This emulator is designed to test IP-based protocols for high scalability and high-speed mobility while maintaining high accuracy levels over extended periods of time. In our previous work, we showed the existence of a relationship between packet handling size and accuracy in a developed emulator system. In this study, we evaluate the performance of agent node loads, and their relationship to processing time accuracy, by obtaining time information from PTP v2. These factors are important when deciding future extension policy. From our experimental results, we determined that performance has two kind of influence. Specifically, processing time increases as loading increases, and some processing elements become excessively long under high load conditions. These factors have a significant influence on time-based distributed systems, such as our distributed mobile network emulator, which is designed to handle processes at microsecond speeds.