Tolga Ayhan

Energy-efficient next-generation optical access networks

Energy efficiency has become an increasingly important aspect of network design, due to both the increasing operational costs related to energy consumption and the increasing awareness of global warming and climate change. This article addresses the energy consumption of different next-generation optical access solutions beyond 10G TDM PONs. It is assumed that next-generation optical access should be able to provide sustainable data rates up to 1 Gb/s per subscriber with a passive fan-out of at least 1:64. Promising system candidates that meet these criteria are compared and analyzed in terms of energy consumption. Candidate PON solutions are also compared to architectures based on point-to-point fiber. A systematic approach is developed for the energy consumption comparison. The analysis is based on estimates of power consumption for key components in next-generation systems. Among the considered candidates, we find that WDM-PON based on RSOA, stacked 10G TDM-PON, and point-to-point fiber offer the lowest power per line potential.

A low-energy rate-adaptive bit-interleaved passive optical network

Energy consumption of customer premises equipment (CPE) has become a serious issue in the new generations of time-division multiplexing passive optical networks, which operate at 10 Gb/s or higher. It is becoming a major factor in global network energy consumption, and it poses problems during emergencies when CPE is battery-operated. In this paper, a low-energy passive optical network (PON) that uses a novel bit-interleaving downstream protocol is proposed. The details about the network architecture, protocol, and the key enabling implementation aspects, including dynamic traffic interleaving, rate-adaptive descrambling of decimated traffic, and the design and implementation of a downsampling clock and data recovery circuit, are described. The proposed concept is shown to reduce the energy consumption for protocol processing by a factor of 30. A detailed analysis of the energy consumption in the CPE shows that the interleaving protocol reduces the total energy consumption of the CPE significantly in comparison to the standard 10 Gb/s PON CPE. Experimental results obtained from measurements on the implemented CPE prototype confirm that the CPE consumes significantly less energy than the standard 10 Gb/s PON CPE.

Energy efficient optical-wireless residential access/in-house networks

Both ecological and economical forces drive the recent energy efficiency efforts for communication networks. The growth of the number of users and the ever-increasing bit rates raise concerns about the societys ability to reduce its energy consumption significantly in the near future. Access networks play a key role in this arena due to the sheer number of users and terminals and low sharing of the infrastructure as compared with other network segments. However, there is no universal framework so far for breaking down and analyzing the energy consumption map within access network. This paper introduces a comprehensive approach to the problem of energy consumption in the fiber-to-the-home (FTTH) access networks integrated with the in-house fiber/copper/wireless networks. The Customer Premises Equipment for Low-Power and Low-Cost Architectures (CUPELLA) project in our research group at Stanford investigates energy efficient access technologies using a structured methodology based on fundamental equipment building blocks both at the micro level and on the macro level when they are integrated into larger systems. Our study looks into both static and dynamic scenarios to exploit temporal and spatial features of the whole access network usage with the goal of substantially reducing the access energy consumption. Our preliminary results indicate that substantial energy saving is in fact possible. For example, with selective sleep mode and switching-mode customer premises equipment (CPE), more than 30% of energy could be saved as compared to broadcast-and-select architecture that does not apply sleep modes.

How to design an energy efficient fiber-wireless network

We analyze the energy consumption of current in-building networks and show that new network designs employing fiber-wireless technologies could lead to significant energy savings in future high-speed networks.

Green in-building networks: The future convergence of green, optical and wireless technologies

The global network energy consumption is increasing at an alarming rate due to proliferation of the Internet and its increasing bandwidth-intensive applications. In this paper, we propose an energy efficient Access/In-Building architecture that features energy efficient customer premises equipment (CPE) design in conjunction with an energy efficient access network protocol, and in-building optical/wireless integration using Radio-over-Fiber. We analyze the energy consumption of the proposed architecture and show that the use of these technologies could lead to up to 50% energy savings compared to the architectures that employ legacy technologies.

CBI: a scalable energy-efficient protocol for metro/access networks

This paper presents a scalable energy-efficient MAC/PHY protocol for building a metro/access network. The proposed cascaded bit-interleaving (CBI) protocol extends the previously reported bit-interleaving concept to a multi-level paradigm. Moreover, a 40Gb/s 3-level electrical duobinary based physical layer scheme has been proposed for cost and energy saving, especially for end terminals. We compared two implementation approaches in terms of optical budget and transmission penalties. The initial estimate from the proof-ofconcept full-custom ASIC design shows that an ultra-low power metro/access network can be realized.

Green optical/wireless access/in-building networks

This paper analyzes energy and power consumption of integrated optical/wireless in-building networks, with the goal of identifying energy hogs and finding ways to reduce the overall energy consumption of such networks. That goal can be achieved by optimizing network, node and circuit design along with an energy-efficient function allocation between the optical and wireless domains. This paper presents our methodology, results, and conclusions as well as selected measurement results from real networks and real network nodes.

Energy-efficient cascaded bit-interleaved converged optical access/in-building network protocol

This paper proposes the cascaded bitinterleaved optical network protocol, an energy-efficient solution aiming at low power consumption in converged optical access/in-building networks while providing high data rates to end users, and a novel network architecture for optical access/in-building networks. In the proposed network architecture, optical-electrical-optical (OEO) regeneration is employed at the interface between access and in-building networks. The downstream frames are generated in the central office using a two-stage bitinterleaving scheme. In the downstream direction, the network nodes only process the data destined for them at a lower clock rate than that of the aggregate passive optical network (PON). In the upstream direction, no word alignment or decoding is performed in the intermediate nodes. Simulation and experimental results show that significant reduction in the power consumption of access/in-building networks can be achieved when the proposed cascaded bit-interleaved protocol is employed in conjunction with the proposed network architecture.

Green Hybrid Optical/Wireless Access/In-House Networks

This paper focuses on energy efficient hybrid access networks. Solutions to underutilization of network are investigated. Power optimization of distributed antenna systems and cell-breathing technology for hybrid access networks are explored.