Building an Energy-efficient Uplink and Downlink Delay Aware TDM-PON System

With the increasing concern over the energy expenditure due to rapid ICT expansion and growth of Internet traffic volume, there is a growing trend towards developing energy-efficient ICT solutions. Passive Optical Network (PON), which is regarded as a key enabler to facilitate high speed broadband connection to individual subscribers, is considered as one of the energy-efficient access network technologies. However, an immense amount of research effort can be noticed in academia and industries to make PON more energy-efficient. In this paper, we aim at improving energy saving performance of Time Division Multiplexing (TDM)-PON, which is the most widely deployed PON technology throughout the world. A commonly used approach to make TDM-PON energy-efficient is to use sleep mode in Optical Network Units (ONUs), which are the customer premises equipment of a TDM-PON system. However, there is a strong trade-off relationship between traffic delay performance of an ONU and its energy saving (the longer the sleep interval length of an ONU, the lower its energy consumption, but the higher the traffi c delay, and vice versa). In this paper, we propose an Energy-efficient Uplink and Downlink Delay Aware (EUDDA) scheme for TDM-PON system. Prime object of EUDDA is to meet both downlink and uplink traffic delay requirement while maximizing energy saving performance of ONUs as much as possible. In EUDDA, traffic delay requirement is given more priority over energy saving. Even so, it still can improve energy saving of ONUs noticeably. We evaluate performance of EUDDA in front of two existing solutions in terms of traffic delay, jitter, and ONU energy consumption. The performance results show that EUDDA significantly outperforms the other existing solutions

Implementing pull manufacturing in make-to-order environments

The demand for increasing product variety and customization has forced many companies to adopt a make-to-order (MTO) strategy. Traditional push-type MTO companies suffer from unstable demands, struggling to deliver on time, making them consider the utilization of pull systems to control production. In the present paper, an overview of pull systems in MTO environments is presented. Moreover, a discrete event simulation (DES) model of an MTO company in the printing and packaging industrial sector was developed and validated, in order to identify areas for improvement. DES was also used in order to evaluate the feasibility of implementing three types of pull systems: kanban, CONstant-Work-In-Process (CONWIP) and Paired Overlapping Loops of Cards with Authorizations (POLCA). The main performance indicators measured were the average WIP and the average throughput time of parts. The key findings of this project for the case study were: a) kanban is inapplicable for the current routing of parts; b) a CONWIP strategy improves the shop floor performance, but only when extra capacity is added to the extrusion workstation; c) production based on POLCA leads to the blockage of the system due to the existence of multi-routes and undirected routing