Recently, Ethernet Passive Optical Network (EPON)with sleep mode has been actively investigated to improve energy conservation in the broadband access network. EPON with cyclic sleep mode transmits up/downstream traffic at the same time and put into the sleep mode at idle time in Optical Network Unit (ONU). However, QoS requirement can be violated by the cyclic sleep mode. In this paper, we propose novel bandwidth allocation algorithm to maximize energy efficiency while satisfying QoS requirement. The main idea is to consider up/downstream traffic in order to determine suitable scheduling transmission period on Optical Line Terminal (OLT). To do this, it allocates bandwidth according to request from ONU, usually. However, when downstream traffic in OLT buffer exceeds predefined threshold, the proposed algorithm compares threshold to bandwidth request from ONU for reducing OLT traffic queuing delay. So, our proposed algorithm can satisfy both energy saving and QoS requirement. In order to evaluate the proposed algorithm, we perform simulation in terms of total and average sleep time of ONU, queuing delay of downstream traffic in OLT buffer.

The Low Power Idle (LPI) has been proposed by IEEE 802.3az Task Force to reduce energy consumption of network devices. Recently, many researches about the LPI have been progressing to maximize the sleep time and improve the performance of energy saving. However, most researches have not considered the effect of transition which causes additional energy consumption. The transition is a serious factor, which affect the performance of energy saving and QoS. Therefore, in this paper, we propose novel algorithms, called Wake Transition Decision(WTD) algorithms to reduce unnecessary transition in an OBS edge router with LPI. The Fixed Time based WTD algorithm(FT-WTD) reduces transition by waiting certain time before sleep transition. The Burst Length based WTD algorithm(BL-WTD) controls the unnecessary transition by keeping the active state of Tx module in an OBS edge router when burst length exceeds certain threshold.Simulation results show that not only approximately 30% of energy consumption can be decreased compared with exist LPI approach but also packet delay is kept within acceptable level by proposed algorithm.

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