Masashi Tadokoro

Bandwidth scheduling techniques in TDM-PON supporting inter-ONU communication with network coding for smart grid applications

In next-generation passive optical networks (PONs), the traffic exchanged among optical network units (ONUs) belonging to the same PON, i.e. inter-ONU traffic, will increase because of emerging applications and services such as the smart grid. Applying network coding (NC) techniques to the inter-ONU traffic will improve throughput, security and reliability. However, the implementation of NC causes additional queuing delay at the optical line terminal (OLT), and degrades the fairness among coded and uncoded inter-ONU flows in terms of latency. This paper proposes a novel bandwidth scheduling technique, i.e. a grouped random scheduling (GRS) algorithm, to reduce the additional queuing delay at the OLT. In addition, a priority index (PI) is defined to further reduce the latency of coded inter-ONU flows, and an adaptive priority scheduling (APS) algorithm is proposed to improve latency fairness among coded and uncoded inter-ONU flows. The proposed techniques are validated by numerical analyses and simulations.

Performance evaluation of energy-efficient PONs for large-scale sensor-actuator networks

This paper proposes a next-generation optical access architecture supporting machine-to-machine (M2M) communication in large-scale sensor-actuator networks. Especially, in this paper, we focus on a smart grid system, which is an application of the large-scale sensor-actuator networks. As a communication infrastructure in the smart grid, optical communication has many advantages over other communication technologies such as wireless communication and power line communication. However, the current optical access systems, e.g. Ethernet passive optical network (EPON) systems, cannot satisfy all requirements for the smart grid communication. In this research, some applicable optical access technologies are discussed from the viewpoint of capacity, reliability, security, energy efficiency and so on. In addition, the existing power-saving mechanism for EPON systems is evaluated using M2M traffic. The proposed architecture can be applied to a communication system in future smart communities including the smart grid, intelligent transport systems and other Internet services.

Energy-efficient peer-to-peer communication with network coding over WDM/TDM-PON

Peer-to-peer (P2P) applications are of growing importance in designing access/home networks. This paper proposes an energy-efficient P2P communication architecture over a wavelength division multiplexing/time division multiplexing passive optical network (WDM/TDM-PON). The proposed architecture includes adaptive link rate (ALR) and network coding (NC) techniques. Simulation results show that the proposed architecture can reduce the power consumption of a communication device effectively in the presence of bidirectional P2P traffic.

Service-oriented communication platform for scalable smart community applications

This paper proposes a service-oriented communication platform enabling the provision of scalable smart community services. The proposed platform is managed using Extensible Markup Language (XML) that has advantages in terms of flexibility, cost-effective implementation and affinity with databases. In practice, the platform is embedded into distributed communication nodes, e.g. routers, switches and home gateways, and both existing IP services and smart community services are provided over public networks. In this research, as an application, a building energy management system (BEMS) using the platform is demonstrated. The feasibility of the network architecture with the platform is discussed based on experimental results of data acquisition and control in the BEMS demonstration.

Virtualization of EPON OLT functions and collision suppression techniques for Multi-Point MAC control

We proposed a novel virtualized PON OLT architecture to realize flexible and cost-efficient PON systems, and evaluate the techniques proposed to suppress collision between upstream signals caused by the software-derived processing time jitter on MPMC.

Highly-efficient ONU power-saving technique with HGW-determined sleep pattern toward next-generation optical access systems

We propose a novel power-saving technique by interworking with the home network via the home-gateway. Numerical simulations show it is highly effective even if the UNI throughput is 100 Mbit/s; it has moderate buffer size requirement. It is also shown that the optical and electrical components and command processing for the state transitions must offer quick response times for higher power efficiency.

Disturbance-observer-based active queue management with time delay using software-defined networking controller

This paper presents an active queue management (AQM) architecture using a software-defined networking (SDN) controller. The SDN controller can achieve the AQM of a router from a remote location. It leads to realizing cooperative AQM of multiple routers and flexible AQM taking traffic conditions of the total network system into account. However, the AQM control system includes additional time-delay elements between the SDN controller and routers, and they have not been discussed. In this research, we discuss the effects of the time-delay elements on the AQM performance. Simulations are performed to compare the queue length variations in a bottleneck router, when we adopt a disturbance-observer (DOB)-based proportional-derivative (PD) controller or a proportional-integral-derivative (PID) controller as an AQM controller. The simulation results show that the DOB-based PD controller tracks the target queue length more accurately than the PID controller even if the additional time-delay elements exist.

Precise inter-ONU time synchronization using jitter buffer in passive optical networks

Various applications and services have been provided over broadband optical access networks such as passive optical networks (PONs). The data communication among optical network units (ONUs) in the same PON, i.e. inter-ONU communication, is expected to be one of the most attractive communication architectures in the future, since it can provide low-latency peer-to-peer (P2P) communication services. However, the current PON systems cannot provide the services which require precise time synchronization among ONUs, e.g. smart grid services. This paper proposes an inter-ONU time synchronization technique using jitter buffer in the optical line terminal (OLT) to make inter-arrival time of control messages for time synchronization a constant value. The practical effectiveness of the jitter compensation technique is verified by a numerical simulation. The simulation results show that the proposed technique provides small packet delay variation (PDV) of the control messages, and improves the synchronization accuracy.

Effect of forward error correction on spectral sliced WDM/TDMA-PON system

A simple and scalable wavelength division multiplexing/time division multiple access passive optical network (WDM/TDMA-PON) system is demonstrated that uses spectral slicing and forward error correction (FEC) with a Reed-Solomon (255, 239) encoder in burst mode upstream transmissions. Receiver sensitivities are improved to -33.5, -34.9 and -35.5dBm at a sliced bandwidth of 100, 200 and 400GHz with FEC. Moreover, the dispersion penalties after a 20km transmission are only about 0.6 and 0.4dB at a bit error rate (BER) of 10-10 at 200 and 400GHz, respectively.