Energy-saving Dynamic Bandwidth Allocation Algorithms In Long Reach Passive Optical Networks

Long Reach Passive Optical Network(LR-PON)extends the coverage of Ethernet Passive Optical Network(EPON)to 100 kilometers,which can serve more users with higher bandwidth and lower cost.LR-PON is a multipoint-to-point network in its upward direction,where Optical Network Units(ONUs)take turns to use the only channel during the polling cycle.As each ONU has limited time for its upward transmission,it stays in idle state for most of the time during each cycle.During the idle time,which is further increased by the long round trip time of LR-PON,keeping the transceivers of ONUs to be active will increase the energy consumption.Therefore,low power modes should be taken into consideration when designing Dynamic Bandwidth Allocation(DBA)algorithms for the purpose to reduce energy consumption.In recent years,energy-saving DBA has gradually becomes one of the hot issues in LR-PON researches.First,the background,network structure and recent progress of LR-PON are presented in this paper.And then,some classic energy-saving algorithms of EPON and LR-PON are investigated.In addition,since the existing energy efficient dynamic bandwidth allocation algorithm in LR-PON cannot make full use of the idle time of ONUs,an Improved Energy-efficient Dynamic Bandwidth Allocation(IEDBA)algorithm is proposed.In IEDBA,ONUs are turned into sleep mode immediately after the end of the upward and downward data transmission without waiting for the coming of gate frame,which can further reduce the energy consumption and lower the average downward data delay.Moreover,this paper analyzes the classic Multi-Thread Polling(MTP)algorithm and its improved algorithms.Although most of the improved algorithms are proposed to optimize the delay performance of MTP,there are few papers involve the energy saving of MTP.Therefore,an Energy-Aware Multi-Thread Polling(EAMTP)algorithm is proposed in this paper.In EAMTP,the transmitters or receivers of ONUs in idle state can be turned off between two transmission slots to turn ONUs into low energy-cost mode(i.e.sleep mode or doze mode).The transceivers are turned back into active mode before the next transmission slot without disturbing the regular transmission.Finally,the IEDBA and EAMTP algorithms are modeled and simulated by OPNET.Simulation results show that compared with some other algorithms,IEDBA and EAMTP have advantages on both delay and energy consumption performances.