Masato Tsuru

Demonstration of Vehicle to Vehicle Communications over TV White Space

Future vehicular communications systems are expected to utilize the vacant channels (white spaces) of the spectrum, otherwise allocated for specific designated use. One such candidate of white space comes from the TV broadcast band. In this demonstration, we will first present animated results of a TV spectrum measurement campaign along the entire portion of Interstate I-90 located in the US state of Massachusetts. Next, we will demonstrate a cyber-physical proof-of-concept lab implementation of our previously developed control and data channel assignment schemes for vehicle-to-vehicle communications over (TV) white space. Finally we will show a video of actual vehicle to vehicle communications field tests conducted in Japan using TV white space.

Data transfer exploiting multiple heterogeneous challenged networks – implementation and application

A concept of integrating multi-path data transfer (IMPDT) is introduced to efficiently transfer a large-sized data if multiple heterogeneous networks are available but none of them has sufficient performance for the requested task. IMPDT integrates heterogeneous networks not simply for bandwidth aggregation but also for providing sustainable control information exchange on a stable but low data rate network path, being handled separately from data transmission on different network paths in different ways. In the present paper, the design of a prototype implementation of IMPDT is discussed especially focusing on retransmission, which is evaluated by field experiments using different types of wireless communication systems. Then the design of a prototype implementation of web access system is discussed as an interactive application over multiple challenged networks by integrating the HTTP protocol and the IMPDT scheme, which implies a potentially wide applicability of our proposed scheme.

Effects of routing granularity on communication performance in OpenFlow networks

The explosive growth of its usage means that the Internet has to become more flexible in order to handle a huge traffic volume efficiently and a variety of users requirement adaptively. OpenFlow architecture is a promising technology for flexible switching and routing to achieve this. In OpenFlow networks, OpenFlow switches can change their action on the basis of header information of an incoming packet. This allows to control traffic flows on the basis of various routing granularities such as destination IP address, TCP connection, etc. While a fine-grained control can increase routing optimality, its control overhead may decrease the communication performance. In this paper, therefore, the impact of routing granularity on communication performance is investigated through simulation evaluations. The results suggest dynamic changes in the routing granularity be considered for efficient traffic control.

Store-Carry-Forward Based Networking Infrastructure: Vision and Potential

In response to the increasing demand for asynchronous mass data exchange even by mobile users, the DTN-related technologies are considered promising for an efficient use of limited network resources and low-cost deployment at the expense of communication delays. The authors previously proposed a Virtual Segment concept aiming at a practical network infrastructure combining Internet-connected broadband wireless network devices, which have high data transmission rates but limited coverage areas, with a store-carry-forward networking by vehicles that is capable of bridging the gaps in broadband service areas in an asynchronous fashion. In this paper, as an extended framework to combine and integrate the wired/wireless communication networks with the transportation networks, Global Information Logistics Infrastructure (GILI) is briefly discussed. A case study of the GILI in a field experiment using school buses is reported with examining its potential. For this experiment, we develop a remote maintenance tool, as an example of store-carry-forward based asynchronous applications, which is shown to be useful in our framework.

Heuristic Maxmin Fairness for the Wireless Channel Allocation Problem

In this contribution, we will reveal some problems related to the transition of the maxmin fairness concept from the continuous to the discrete domain. By means of the wireless channel allocation problem, a heuristic approach to fairness allocation will be presented, based on searching for allocations with high similarity of the corresponding throughputs and high total throughput at the same time. Thus, the proposed approach overcomes stated problems with discrete fairness by capturing the characterisitics of fairness as comparison criterion among solutions. A meta-heuristic algorithm is proposed to handle this problem, and results are presented for problem scales, where a complete analysis is still possible. The approach is demonstrated to sufficiently follow up the maxmin fairness states with regard to performance, while definitely excluding any artifacts arising from the transition of maxmin fair allocations to the discrete domain.

Network-Supported TCP Rate Control for High-Speed Power Line Communications

The high-speed power line communications (PLC) technology has great potential to serve as an infrastructure for home networking because every home electric device must be connected to a power line network. However, various special environmental factors, such as power level attenuation, divergence between different voltage lines (100/200 V), and fluctuations of source impedance and noise by other equipment, often severely degrade the communication performance. In the present paper, we focus on the flow-level performance of end-to-end data transmission (i.e., TCP) over PLC line with various negative environmental factors, which has not been well investigated so far. We first develop a new module on the NS-2 network simulator, which is driven by the information on time-varying packet error rate over PLC line prepared beforehand, to simulate the High Definition (HD)-PLC’s data transmission including some dedicated mechanisms against degradation caused by the environmental factors. The simulator is validated by comparing the TCP performance obtained from experiments on a real HD-PLC network and that from simulations using the packet error rate information measured in the real environments. Next, we address a problem on co-existing multiple TCP flows over PLC line and then, as a solution, propose a new and practical network-supported TCP rate control scheme in which the sender-side PLC modem modifies the advertised window (awnd) in TCP ACK packets for controlling the TCP’s sending rate in response to the PLC line condition. The simulation results demonstrate the effectiveness of the proposed scheme.

Code Optimization for Packet Filters

Packet filters play an essential role for network traffic/security management in todays Internet. To make software-based packet filters so fast that could work even in suffering from DOS attacks, the authors are challenging to effectively combine both the higher-level optimization relating to algorithmic structure adapted to the input packet sequence and the lower-level one relating to acceleration techniques in compiler study. In this paper, we focus on the lower-level (machine code) optimization using software pipelining, and report preliminary experimental results indicating that our approach has great potential to accelerate packet filter performance. Our code optimization achieves more than ten times higher performance compared with a conventional interpreter-based packet filter for each of seven typical fragments of packet filter rules

Software pipelining for packet filters

Packet filters play an essential role in traffic management and security management on the Internet. In order to create software-based packet filters that are fast enough to work even under a DOS attack, it is vital to effectively combine both the higher-level optimization related to algorithmic structure and the lower-level optimization related to acceleration techniques in compiler study. In the present paper, we focus on the lower-level (machine code) optimization using software-pipelining, and report experimental results that indicate the potential of our approach for accelerating packet filter performance. The technical difficulty is that the packet filter is a lump of conditional branches, so that standard optimization techniques usually applied to basic blocks is not directly applicable to this problem. Using predicated execution and enhanced modulo scheduling, we solve this problem and achieve 20 times higher performance compared with a conventional interpreter-based packet filter. We also compare the proposed filters and compiler-based packet filters, and obtain a better than two-fold increase in performance.

Network-supported TCP rate control for the coexistence of multiple flows in IP over PLC

With the approval of IEEE P1901 standard for power line communications (PLC) and the recent Internet-enable home appliances like the IPTV having access to a content-on-demand service through the Internet as AcTVila in Japan, there is no doubt that PLC has taken a great step forward to emerge as the in-home-network technology. However, existing schemes developed so far have not considered the PLC network connected to an unstable Internet environment (i.e. more realistic situation). In this paper, we investigate the communication performance from the end-user perspective in such networks with large and variable round-trip time (RTT) and with the existence of cross-traffic. Then, we address the problem of unfair bandwidth allocation when multiple flows coexist and propose a TCP rate control considering the difference in terms of end-to-end delay and bandwidth to solve it. Our methodology was validated through simulations, and it effectively deals with the throughput unfairness problem under critical communication environment, where multiple flows with different RTTs share the PLC and cross-traffic exists on the path of the Internet.

Unsorting the Proportional Fairness Relation

Typical problems related to the application of proportional fairness are sparsity of the relation with increasing dimension, and the operator confusion problem. Here, we propose a new fairness relation derived from proportional fairness to handle these problems. The design principle behind this relation is relational unsorting: if there is a relation x(R)y between elements x and y from n-dimensional Euclidian space, the unsorted relation x(uR)y holds whenever there is a permutation x* of the elements of x for which x*(R)y holds. We apply this concept to proportional fairness, study the properties of the new relation, contrast with another relation based on over-sorting proportional fairness, and provide simulations to demonstrate the ease of ordered proportional fairness for meta-heuristic search.