I-Shyan Hwang

A Hybrid Scalable Peer-to-Peer IP-Based Multimedia Services Architecture in Ethernet Passive Optical Networks

Peer-to-peer (P2P) applications such as P2P video streaming and internet video calling have gained tremendous popularity and are expected to be vastly increasing in the next few years. However, low-cost large-scale video services have remained an intangible goal. The ethernet passive optical network (EPON) is being regarded as one of the promising for next-generation optical access solutions in the access networks attempt to tackle this problem but facing a major challenge to offer scalable large-scale video services. Therefore, in this paper, we propose an architecture which combines the advantages of EPON and P2P architecture to provide scalable Internet Protocol delivery multimedia services and improve quality-of-services. In the proposed architecture, we design new optical network unit (ONU) mechanisms, which support traffic redirection communication among ONUs in combination with caching. Thus, it can reduce the resource consumption and add extra downstream bandwidth at the optical line terminal since the intra-PON traffic is not necessary to be buffered and scheduled in the downstream direction. Finally, we propose a “Redirect” dynamic bandwidth allocation scheme, which can support intra-PON traffic redirection and intertraffic bandwidth allocation. Simulation results have shown that our proposed architecture can improve the overall QoS in terms of end-to-end delay, jitter, system throughput, fairness, and packet dropping rate.

Generic QoS-Aware Interleaved Dynamic Bandwidth Allocation in Scalable EPONs

The Ethernet passive optical network is being regarded as one of the best solutions for next-generation optical access solutions. In time-division multiplexing-passive optical network technology (TDM-PON), the dynamic bandwidth allocation (DBA) plays a crucial role in efficiently and fairly allocating the bandwidth between all users. Moreover, the quality of service (QoS) is also an essential requirement to support triple-play services. However, many proposed DBA mechanisms are still unable to solve the idle period problem and enhance the differentiated services (DiffServ), which will decrease the quality of overall system performance. Therefore, this paper proposes a generic QoS-aware interleaved dynamic bandwidth allocation (QA-IDBA). The QA-IDBA can operate adaptively bi-partitioned interleaved scheduling with QoS-based predictive limit bandwidth allocation (QP-LBA) and excess bandwidth reallocation (EBR) with the remaining bandwidth compensation scheme to eliminate the idle period, enhance QoS, and effectively reduce high-priority traffic delay and jitter. We conduct detailed simulation experiments with 16 and 32 optical network units (ONUs) to show the scalability. Simulation results show that our proposed algorithms can accommodate the growth of ONUs and achieve better overall quality of system performance even if the high-priority traffic is increasing from 20%, 40%, and 60%.

Scalable architecture for VOD service enhancement based on a cache scheme in an Ethernet passive optical network

Video on demand (VOD) is becoming one of the most important services for many network operators. VOD needs a huge bandwidth to deliver data in a real-time network. Ethernet passive optical networks (EPONs) provide a low-cost and high-speed solution for multimedia services such as VOD. In this paper, we propose a scalable architecture based on an EPON, using single copy broadcast in the downstream direction and a special caching mechanism responsible for VOD requests, to improve VOD services. Our architecture consists of an optical network unit (ONU) with an associated storage unit and optical line terminal (OLT) components. We set a “broadcast” logical link identifier in the video packets so that all of the ONUs can accept them. Therefore, when the movie is sent from the OLT to the ONUs after it is requested by the user, each ONU accepts the movie packet and saves it in its own storage. In this architecture, the OLT just needs to send each video to the ONUs once, and the attached storage is responsible for future requests. With this architecture, at least 60% of VOD traffic can be saved in the feeder fiber. Simulation results show that our architecture can improve the overall quality of service in terms of packet loss, mean packet delays, jitter, and system throughput.

Comprehensive performance assessment of bipartition upstream bandwidth assignment schemes in GPON

With the emerging diversified services, the gigabit-capable passive optical network (GPON) has emerged as one of the most important technologies to support the next-generation broadband access networks. Dynamic bandwidth assignment (DBA) avoids transmission collision in the upstream direction and improves the efficiency of the PON upstream bandwidth by dynamically adjusting the bandwidth among the optical network units (ONUs) in response to the ONU burst traffic requirement. Instead of using GATE and REPORT control messages in Ethernet PON DBA, the buffer REPORT/GRANT message is embedded into a GPON encapsulation mode (GEM)/GPON transmission convergence (GTC) frame, and all ONUs are essentially polled simultaneously within a GEM/GTC frame in GPON DBA. This paper proposes a bipartition DBA (BI-DBA) mechanism in GPON that divides the transmission cycle time into two groups and adjusts the bandwidth dynamically. Two cases are considered: in the first case, there is a first group for high priorities T-CONT 1 and T-CONT 2 and a second group for low priorities T-CONT 3 and T-CONT 4, called class based scheduling (CBDBA). In the second case, the first and the second group are created according to the number of ONUs, called group based scheduling (GBDBA). Moreover, the T-CONT 2 traffic has a prediction mechanism and recycles the remaining unused bandwidth for the low-priority T-CONTs. The GBDBA has better system performances in terms of the average bandwidth utilization, packet latency, and drop probability; on the other hand, the CBDBA has better packet delay performance when the proportion of T-CONT 1 traffic is higher and has better fairness performance.

A novel dynamic fault restoration mechanism using multiple rings approach in WDM mesh network

This work describes a distributed fault restoration algorithm, called the Dynamic Multiple Ring Algorithm (DMRA), for application in WDM mesh networks. This study explores the choice of restoration paths and the assignment of fault-tolerant bandwidth when a link, node, or channel failure occurs according to the change in traffic load, number of nodes, and transmission delay including propagation and switching delays. Accordingly, the primary aim of this work is to use networking segments near faults to share the restoration load throughout a mesh network. Each node searches for restoration paths in their near environment using the proposed DMRA. Nodes use distributed control to search for neighboring nodes and to establish the relationship between them to build numerous logical rings. Nodes can also locate faults in the logical rings. These rings establish the restoration paths. The traffic load over failed links or nodes can be diverted to other paths in the networking segments. The cost of the restoration paths is computed at each node based on both the current capacity and the transmission delay. The selected restoration paths are suitable transmission routes in the network neighborhood. Hence, restoration paths can be identified and wavelength assigned quickly according to network bandwidth and traffic load. Simulation results reveal that the proposed method works extremely quickly and has a high success rate. Consequently, it is very useful for applications in real WDM networks, where the status varies from minute to minute.

QoS Enhancement of Live IPTV Using an Extended Real-Time Streaming Protocol in Ethernet Passive Optical Networks

Internet protocol TV (IPTV) is one of the most important multimedia applications for next-generation networks. IPTV provides triple-play services that require high-speed access networks with the functions of multicasting and quality of service (QoS) guarantees. Among access networks, Ethernet passive optical networks (EPONs) are regarded as among the best solutions to meet higher bandwidth demands. In this paper, we propose a new architecture for multicasting live IPTV traffic in EPONs. The proposed mechanism involves assigning a unique logical link identifier to each IPTV channel. To manage multicasting, a table in the optical line terminal (OLT) and in each optical network unit (ONU) is constructed. These tables are maintained in the reconciliation sublayer to deliver the IPTV traffic. We extend the message passing of the original real-time streaming protocol (RTSP), called the extended RTSP (ERTSP), to handle the IPTV requests. A mechanism is proposed to handle the IPTV requests as intra traffic in the ONU without sending the request to the OLT. Handling the live IPTV channel as intra traffic can save bandwidth in the feeder fiber and increase the system throughput. Simulation results show that our proposed architecture can improve the system performance and QoS metrics in terms of packet delay, jitter, system throughput, and packet loss.

Multicast wavelength assignment with sparse wavelength converters to maximize the network capacity using ILP formulation in WDM mesh networks

In general, multicast routing and wavelength assignment (MC-RWA) can be subdivided in routing and wavelength assignment issues in wavelength-division multiplexing (WDM) mesh networks. Previous studies on WDM multicast have mainly focused on WDM multicast routing. The multicast wavelength assignment problem is studied in this paper. A unicast routing path can be established by a lightpath in an all-optical network. However, in the multicasting case, a multicast routing tree can be established by a single light-tree or several lightpaths, or a combination of several light-trees and lightpaths. We propose a wavelength assignment algorithm for finding an optimal combination of lightpaths and light-trees to construct a newly required multicast session. First of all, two cost functions are given to evaluate the establishing cost for each feasible wavelength, and then find a set of wavelengths that covers all destinations with the minimal cost using Integer Linear Programming (ILP) formulation. We focus on maximizing the total number of users served in a multicast session and the network capacity. The simulation results show that the proposed algorithm can improve system resource utilization and reduce the blocking probability compared with the First-Fit algorithm.

QoS-aware energy-efficient mechanism for sleeping mode ONUs in enhanced EPON

Ethernet passive optical network (EPON) is a broadband access time-division multiplexing passive optical network technology which can be referred to as green network, as it has less power consumption compared with other networks. The optical network unit (ONU) is the best candidate to implement energy-saving adjustments in EPON. Turning off the ONU transmitter (Tx)/receiver (Rx) for substantial time is a common method to achieve the energy saving. However, setting overlong sleep duration decreases the QoS, while short sleep duration increases the ONU power consumption. The challenging issue is how to balance the trade-off between achieving energy saving and guaranteeing QoS. In this paper, we introduce an enhanced EPON architecture and a QoS-aware energy-saving mechanism to reduce ONU energy consumption and guarantee an overall QoS metric based on the ITU-T standards requirements. To achieve the energy saving in the upstream/downstream direction, two sleep durations are defined for the ONU’s Tx/Rx to generate four ONU modes including active, transmission, doze, and sleep. Simulation results show that the proposed scheme improves the energy efficiency 44xa0% in average to fulfill the QoS metrics in terms of packet loss, delay and jitter, and the buffer requirement.

Distribution drop fiber in-service fault management in enhanced EPON system

Ethernet passive optical network (EPON) is considered one of the best candidates for next-generation optical access solutions. Practical and cost-effective survivability and maintenance mechanisms are therefore becoming the key issues for continued development of viable EPON solutions. In addition, 80% of faults occur within the first/last mile. Therefore, in this paper, we propose in-service integrated fault management mechanisms at the distribution drop fibers (DDFs) in EPON. The proposed mechanisms can automatically detect and identify any signal anomalies and DDF faults in the physical layer, thus decreasing the operating expense (OpEx) to be incurred in sending off technicians in the field. The mechanisms are two-fold: pre-fault and post-fault. In the pre-fault mechanism, we use optical receiver type/length/value (TLV) code as a sensor for triggering the embedded miniaturized optical-time-domain reflectometry (OTDR), placed at optical network units (ONUs). This mechanism observes and measures the abnormal condition and reports it to the optical line terminal (OLT), via restoration plan fiber link. In post-fault mechanism, we divide the ONUs into several restoration groups (RGs) to guarantee upstream transmission of the affected ONUs. Lastly, the fault dynamic bandwidth allocation for fault management, referred as FDBA, is presented. Simulation results show that the proposed mechanisms can withstand DDF faults without any significant impact on the overall quality of service (QoS) performance, in terms of mean packet delay, queue length, system throughput, and packet loss.

Genetic expression programming: a new approach for QoS traffic prediction in EPONs

The Ethernet passive optical network is being regarded as the most promising for next-generation optical access solutions in the access networks. In time division multiplexing, passive optical network technology (TDM-PON) and the dynamic bandwidth allocation (DBA) play a crucial key role to achieve efficient bandwidth allocation and fairness among subscribers. Therefore, the traffic prediction in DBA during the waiting time must be put into the account. In this paper, we propose a new prediction approach with an evolutionary algorithm genetic expression programming (GEP) prediction incorporated with Limited IPACT referred as GLI-DBA to tackle the queue variation during waiting times as well as to reduce the high-priority packet delay. Simulation results show that the GEP prediction in DBA can reduce the expedited forwarding (EF) packet delay, shorten the EF queue length, enhance the quality of services and maintain the fairness among the optical network units (ONUs). We conducted and evaluated the detail simulation in two different scenarios with distinctive traffic proportion. Simulation results show that the GLI-DBA has EF packet delay improvement up to 30xa0% over dynamic bandwidth allocation for multiple of services (DBAM). It also shows that our proposed prediction scheme performs better than the DBAM when the number of ONUs increases.