For an efficient utilization of the upstream bandwidth in passive optical network, a dynamic bandwidth assignment mechanism is necessary as it helps the service providers in provisioning of bandwidth to users according to the service level agreements. The scheduling mechanism of existing schemes, immediate allocation with colorless grant and efficient bandwidth utilization (EBU), does not assign the surplus bandwidth to a specific traffic class and only divides it equally among the optical network units (ONUs). This results in overreporting of ONU bandwidth demand to the optical line terminal and causes wastage of bandwidth and increase in delays at high traffic loads. Moreover, the EBU also assigns the unused bandwidth of lightly loaded ONU queues to the overloaded queues through an Update operation. This Update operation has a flaw that it borrows the extra bandwidth to a queue in the current service interval, if the queue report is higher than its service level agreement and refunds in next service interval. This borrow-refund operation causes reduced bandwidth allocation to the lower priority classes and increases their delay and frame loss. This study improves both these weaknesses. The simulation results show that the proposed scheme uses bandwidth efficiently and reduces mean upstream delay of type-2 (T2) traffic class by 38% and type-3 (T3) up to 150% compared to immediate allocation with colorless grant at a cost of up to 10% higher delay for T2. However, T4 performance improves by 400% compared to EBU with slight increase in delay for T2 traffic class. Overall, it shows a balanced performance for all the traffic classes and minimizes the bandwidth waste per cycle as well as the frame loss rate.

Comprehensive bandwidth utilization and polling mechanism for XGPON

Abstract In time division, multiple access (TDMA)-based passive optical network (PONs), a dynamic bandwidth assignment (DBA) is necessary for efficient utilization of the available bandwidth of the upstream link. An efficient DBA scheme can improve the upstream performance of a traffic class of an ONU in two ways. First, it can increase the bandwidth assignment to it by efficiently utilizing the available bandwidth. Secondly, it can reduce the channel and frame idle time by increasing the polling frequency and by assigning extra surplus bandwidth not used by the other ONUs. Many DBA schemes have been reported for both ITU PONs (GPON and XGPON) and IEEE PONs (EPON and 10 G EPON). In this study, we explain the impact of DBA scheme on the upstream performance of PON and then do a thorough survey of both PON standards, categorize the DBA schemes and review them critically. Based on the literature review we also give our opinion on the most suitable DBA scheme for both type PONs on the basis of upstream delays, frame loss and bandwidth utilization efficiency.

A Survey of Dynamic Bandwidth Assignment Schemes for TDM-Based Passive Optical Network

An energy efficient cyclic sleep control framework for ITU PONs

Long Range Dependence is the most important character of the self-semilar traffic in data networks. With wavelet, Long Range Dependence can be converted into Short Range Dependence and then the network traffic can be predicted. By this method, this paper studies the GPON on its key technique in the MAC layer: Dynamic Bandwidth Allocation. Then, an improved dynamic bandwidth allocation algorithm is proposed.

Improved dynamic bandwidth allocation algorithm for GPON

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A Survey of Energy Conservation Schemes for Present and Next Generation Passive Optical Networks

Dynamic bandwidth assignment (DBA) schemes for long reach PONs face a suffer from higher upstream channel idle time due to long round trip time (RTT) In ITU PONs, the DBA schemes; Immediate allocation with colorless grant (IACG), Efficient bandwidth utilization (EBU) and GPON redundancy eraser algorithm (GREAL) minimize idle time by sending bandwidth grants to the optical network units (ONUs) every downstream frame (DF) EBU further improves IACG by utilizing unused bandwidth (UBW) of other traffic classes Sending the grant results every DF requires optical line terminal (OLT) to remember all previous grants sent to ONU during RTT and subtract them from the received queue reports Since, both IACG and EBU assign the excess bandwidth equally to ONUs Therefore, the OLT is actually not aware of the complete grant to each traffic class and thus do not subtract these completely from receiving reports This leads to wastage of bandwidth and higher US delays due to over granting GREAL resolves this problem by not utilizing the excess bandwidth which also leads to increased US delays The proposed scheme in this study eliminates this shortcoming by allocating excess bandwidth to each traffic class completely at the OLT Moreover, the UBW assignment mechanism of EBU is also improved Simulation results show a 50-85 % reduction in delays of type-2 (T2) and type-3 (T3) traffic classes versus GREAL and IACG and up to 40 % reduction in delays for type-4 (T4) versus EBU

Shahid-Ur Rehman

Papers

Comprehensive Polling and Scheduling Mechanism for Long Reach Gigabit Passive Optical Network

Investigation of pure-cubic optical solitons in nonlinear optics

Efficient optical duobinary transmission for high-speed next generation passive optical networks