The traffic of the future aggregation network will dynamically change not only in volume but also destination to support the application of virtualization technology to network edge equipment to achieve cost-effectiveness. Therefore, future aggregation network will have to accommodate this traffic cost-effectively, despite dynamic changes in both volume and destination. To correspond to this trend, in this paper, we propose an optical layer 2 switch network based on bufferless optical time division multiplexing (TDM) and dynamic bandwidth allocation to achieve a future aggregation network cost-effectively. We show here that our proposed network architecture effectively reduced the number of wavelengths and optical interfaces by application of bufferless optical TDM technology and dynamic bandwidth allocation to the aggregation network.

This letter proposes a new scheduling method to improve scheduling efficiency of EPON. The proposed method uses a credit pool for each optical network unit (ONU) and for each service class. For high scheduling efficiency, the credit pool of an ONU can be negative amount to utilize the unused ONU credits. Also the proposed method dynamically excludes the lowest service class from scheduling to decrease a transmission cycle length. Using simulations, we show that the proposed method is better than the existing methods in mean delay.

The Ethernet passive optical network (EPON), which is one of the PON technologies for realizing FTTx (Fiber-To-The-Curb/Home/Office), is a low-cost and high-speed solution to the bottleneck problem that occurs between a backbone network and end users. The EPON is compatible with existing customer devices that are equipped with an Ethernet card. To effectively control frame transmission from optical network units (ONUs) to an optical line termination (OLT), the EPON can use a multi-point control protocol (MPCP) with control functions in addition to the media access control (MAC) protocol function. In this paper, we propose a two-phase cycle dynamic bandwidth allocation (TCDBA) algorithm to increase the channel utilization on the uplink by allowing frame transmissions during computation periods, and combine the TCDBA algorithm with the queue management schemes performed within each ONU, in order to effectively support differentiated services. Additionally, we perform simulations to validate the effectiveness of the proposed algorithm. The results show that the proposed TCDBA algorithm improves the maximum throughput, average transmission delay, and average volume of frames discarded, compared with the existing algorithms. Furthermore, the proposed TCDBA algorithm is able to support differentiated quality of services (QoS).

Although wavelength division multiplexing-passive optical network (WDM-PON) is known as a high-speed transfer, it creates high channel costs per subscriber and low bandwidth utilization due to the fact that a wavelength is dedicated to each subscriber. Thus, it is imperative to reduce channel costs per subscriber and improve the bandwidth utilization. To achieve these, we first adopt a existing WDM-PON, which uses the bidirectional transmission with a single source for cost-efficiency by employing a gain-saturated reflective semiconductor optical amplifier (RSOA). Secondly, based on the existing WDM-PON, we propose an enhanced hybrid WDM/TDM-PON, which can extend the number of subscribers supported in each wavelength with splitters in the physical layer and a shared-time division duplex (TDD) frame format in the media access control (MAC) layer. Moreover, it can adaptively control the bandwidth through a dynamic bandwidth allocation (DBA) scheme according to the volume of traffic. Compared to the non TDD-based hybrid WDM/TDM-PON, it can reduce channel costs per subscriber from the extended number of subscribers supported in each wavelength. Furthermore, due to the DBA, it can improve the total queueing delay and throughput, and thus increase the bandwidth utilization.

A fast class-of-service oriented packet scheduling (FCOPS) has a service fairness problem since a credit pool for a service class is initialized at the beginning of a transmission cycle whose starting moment is fixed at a specific ONU. To remedy the service unfairness of FCOPS, we suggest an enhanced class-of-service oriented packet scheduling (ECOPS) that uses a new initialization cycle whose starting moment is fairly distributed to each ONU. Also, ECOPS generates a colorless grant to utilize the resource wastage, when traffic is light and the total sum of grants of an ONU is less than a minimum size. Using simulation, we validate ECOPS as superior to FCOPS in the mean delay and the service fairness.

We suggest a dual thresholds method for the dynamic bandwidth allocation in EPON. In the suggested method, a buffer in ONU has two thresholds and ONU generates a normal request and a greedy request based on the two thresholds. Also, OLT estimates the overall traffic load and grants the greedy request when estimated traffic is light. We study upstream channel resource wastage and show the suggested method decreases the upstream channel resource wastage. Using simulation, we validate the dual thresholds method is superior to the existing methods in the mean delay.

In this paper, we propose a PON-based access network based on conventional TDM-PON architecture for the smooth, economical and effective transition to the future optical access network. We also propose a dynamic MAC protocol for wavelength channel and bandwidth allocation in the TDM-PON subscriber networks, which can provide enhanced network scalability and flexibility, and greater adaptability to the increasing number of subscribers in TDM-PON. In the proposed dynamic MAC protocol, several key functions are manifested, such as multiple wavelength channel utilization and dynamic allocation of multiple time-slots to a user depending on SLA between OLT and ONUs to meet QoS requirements. A dedicated control channel is used for delivering the request and status information between OLT and ONUs. We evaluate the performances of the proposed MAC protocol thru a statistical queuing analysis and numerical simulations. In addition, through simulations using various traffic models we verify the superior performance of the proposed approach by comparing it with conventional TDM-PONs.

We suggest a new minimum credit method for the dynamic bandwidth allocation in EPON. In the suggested method, to eliminate the unused transmission time-slot, each ONU requests no more than a predetermined maximum. We analyze the upstream channel resource wastage when traffic is light. Based on the analysis, we derive a minimum credit that eliminate the upstream channel resource wastage. The OLT estimates a traffic load and grants a minimum credit when the request is smaller than the minimum credit and traffic is light. Using simulation, we show the minimum credit discipline is superior than the existing methods in the mean delay and the frame loss rate.

As an alternative solution to provide the quality of services (QoS) for broadband access over Ethernet Passive Optical Network (EPON), we present the usage of MAC control message for plural class queues and a traffic-class burst-polling based delta dynamic bandwidth allocation (DBA), referred to as TCBP-DDBA, scheme. For better QoS support, the TCBP-DDBA minimizes packet delays and delay variations for expedited forwarding packet and maximizes throughput for assured forwarding and best effort packets. The network resources are efficiently utilized and adaptively allocated to the three traffic classes for the given unbalanced traffic conditions by guaranteeing the requested QoS. Simulation results using OPNET show that the TCBP-DDBA scheme performs well in comparison to the conventional unit-based allocation scheme over the measurement parameters such as: packet delay, packet delay variation, and channel utilization.

A broadband access network is required for supporting the increased Internet data traffic. One of the most cost-effective solutions is the Ethernet Passive Optical Networks (E-PONs) with the efficient bandwidth assignment function by which the upstream bandwidth can be shared among access users. To satisfy the services with heterogeneous QoS characteristics, it is very important to provide QoS guaranteed network access while utilize the bandwidth efficiently. In this paper, a dual DEB-GPS scheduler in E-PON is presented to provide delay-constraint and lossless QoS guarantee to QoS service and maximize the bandwidth to best-effort service. Simulation results show our scheme outperforms the conventional bandwidth allocation scheme in E-PON system.

A simple nation-wide core network architecture based on the optimized combination of WDM and OTDM technologies in a two-tier structure network is proposed. The dynamic timeslot allocation in a fixed length frame structure associated with the wavelength routing scheme creates a virtual path with variable bandwidth for edge-to-edge transport of any type of packet protocol without O-E-O conversion. The simulation results show that dynamic timeslot assignment with bandwidth reservation is the best alternative for the network bandwidth utilization efficiency. The influence of the delay caused by the physical size of the network during the request-acknowledgement process is also discussed.

This paper presents an efficient scheme for access bandwidth control for VBR (Variable Bit Rate) traffic between radio mobile terminals and their base stations in a WATM (Wireless ATM) network. After introducing the wireless ATM system model, we describe a new algorithm that enables dynamic slot allocation under TDMA/TDD (Time Division Multiple Access/Time Division Duplex) Media Access Control, making use of UPC (Usage Parameter Control) parameters and traffic characteristics. We show more efficient bandwidth utilization with our proposed algorithm, compared to other conventional algorithms. Moreover, we reveal that our algorithm improves cell transmission delays.

The explosive increase of traffic in computer communications is a clear sign that we have entered the multimedia information age. To cope with this ever increasing need, economical optical access networks that support burst traffic such as in the Internet are expected to be developed. The ATM-PON is considered to be a promising candidate for such a network, and vigorous efforts in this direction are being promoted worldwide. This paper focuses on accommodating burst traffic in the ATM-PON. In order to do this, a mechanism to transport bandwidth requests from the ONU to the OLT and an algorithm to support dynamic bandwidth allocations based on ONU requests are needed. We have performed a comparative study on bandwidth request methods and bandwidth allocation algorithms, including bandwidth request dependence on time interval and correlation and/or impact between system design parameters. The results of computer simulations are useful in determining how to accommodate burst traffic efficiently in the ATM-PON.