A traffic-class burst-polling based delta DBA scheme for QoS in distributed EPONs
Introduction
Passive optical network (PON) technology is considered as the effective solution for the realization of access network [1] because it is highly configurable, scalable and can accommodate required bandwidth with less interference. Ethernet PON (EPON), an extended platform essentially preserves the merits of Ethernet networks while reducing the complexities and improving the quality of services (QoS) to an expectation level [2], [3]. Fig. 1 shows the typical EPON system. Practically, EPONs consist of one optical line terminal (OLT) situated at the central office (CO) and multiple optical network units (ONUs) located at customer premises equipment (CPE). In the downstream direction (from OLT to the ONUs), the OLT broadcasts to all ONUs. The frames are sent to their destination ONUs by using media access control (MAC) layer. In the upstream direction (from ONUs to the OLT), because it is a multipoint-to-point (M2P) network, the fiber channel is shared by all ONUs. Therefore, scheduling is needed to prevent data collision from different ONUs. A detrimental solution is to assign a time slot to each ONU. While assigning a fixed time slot regardless of its demand is simple, this scheme cannot adapt to bursty heterogeneous traffic and may waste bandwidth considerably. Consequently, a dynamic bandwidth allocation (DBA) scheme is required to support better QoS.
Recent developments on DBA in EPONs in achieving QoS to a desired level are in progress [2], [3], [4], [5], [6], [7], [8], [9], [10]. In this paper we propose a traffic-class burst-polling based delta dynamic bandwidth allocation (TCBP-DDBA) scheme that works on Multi-Point Control Protocol (MPCP) [19], and the algorithm can provide better QoS. In this scheme, an ONU is allowed to report all of its instantaneous traffic loads for each traffic class separately, and thus the OLT knows all ONUs bandwidth requirements prior to allocation. The OLT proportionally allocate surplus bandwidth according to the ratio of demand of a class to the total traffic, which is based on sophisticated algorithm such as DDBA. OLT distributes the bandwidth for different ONUs depending on the request size by utilizing the surplus bandwidth, and then send the calculated gate message to ONUs guaranteeing a prior service to expedited forwarding (EF) packets at one cycle time. Thus, this scheme is referred to as TCBP.
The rest of the paper is organized as follows. Section 2 introduces the previous works on DBAs in EPONs. Section 3 describes the system architecture covering the basic concept of MPCP protocol and an ingress/egress queueing mechanism in the ONU. In Section 4 we propose the TCBP-DDBA algorithm considering differentiated Class of Service (CoS) field of the packets in question. In order to verify and validate the proposed scheme, a number of simulation oriented experiments were carried out by considering various performance parameters such as packet delay, queue size, packet delay variation (PDV) and channel utilization (throughput). These are reported in Section 5. Finally, some concluding remarks are given in Section 6.
Section snippets
Previous works
Kramer et al. [2], [3] proposed an Interleaved Polling with Adaptive Cycle Time (IPACT) scheme, in which a maximum transmission window size is required to confine a maximum frame size. Although the scheme shows good performance it inherits disadvantages: one is, it is not suitable for delay and jitter sensitive services because of the variable polling cycle time and the other is in every cycle time, when to decide the grant size of time-slot allocated to each ONU, the OLT does not know the
Control architecture in EPON
This section will introduce overview of the MPCP operation and queue structure at ONU. In EPON, all data are encapsulated in the Ethernet frames, which are broadcasted in the downstream direction. In the upstream direction, however, the ONUs have to share channel. Access to the shared channel is arbitrated by MAC protocol.
Dynamic bandwidth allocation
In this section, we have proposed intra-ONU priority scheduling mechanism and TCBP-DDBA algorithm. Basically, DBA is as follows: each ONU sends its own information of the three prioritized queues for BE, AF, and EF traffics using the same REPORT message. OLT calculates the grants for the three prioritized service classes per ONU using the reported information and differences of previous information, and transmits the grants for an ONU in a GATE message at the fixed cycle time. Then, each ONU
Performance evaluation
In this section, the model description and simulation results are presented. The considered performance metrics are packet delay, queue size, PDV and channel utilization. The packet delay and the queue size are defined to be the time and the buffer size of an ONU between the departure from a traffic source and the arrival to the OLT. The packet delay variation is defined to be the standard deviation of packet delay. The channel utilization is defined to be a measure of the total amount of data
Conclusions
The EPON system offers effective solution to the broadcast and high-speed access network services. For guaranteed QoS to heterogeneous sources there is a need to develop efficient DBA algorithm. In this paper we have presented a TCBP-DDBA scheme for the EPON based system. This scheme can effectively allow all ONUs to fairly share the uplink bandwidth according to their bandwidth demands. That is, TCBP-DDBA ensures that all service classes proportionally share the bandwidth on the ratio of the
Acknowledgment
The project is supported by ITRC-CHOAN, MIC, South Korea.
Yeon-Mo Yang is currently working towards his PhD degree in Mechatronics and is a member of SI (System Integration) lab at GIST, Korea. His current research interests are in the areas of passive optical networks, optical MEMS (Micro-electro Mechanical Systems), multicasting protocols in access area, wire speed layer 3 switch for QoS and Mechanical filter design. Yeon-Mo Yang received his BS degree in electrical engineering from KAIST (Korea Advanced Institute of Science and Technology, //www.kaist.ac.kr
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Yeon-Mo Yang is currently working towards his PhD degree in Mechatronics and is a member of SI (System Integration) lab at GIST, Korea. His current research interests are in the areas of passive optical networks, optical MEMS (Micro-electro Mechanical Systems), multicasting protocols in access area, wire speed layer 3 switch for QoS and Mechanical filter design. Yeon-Mo Yang received his BS degree in electrical engineering from KAIST (Korea Advanced Institute of Science and Technology, http://www.kaist.ac.kr) 1990, and MS from GIST (Gwangj Institute of Science and Technology, http://www.gist.ac.kr) in Mechatronics in 1998. Previous joining GIST, he was a project leader and senior member of engineering staff at LG industrial systems (http://www.lgis.co.kr) and LG Innotek (http://www.lginnotek.com) Company in the field of automation and computer networks in 1995 and 1999, respectively. He has more than 10 years of experience in the embedded industrial systems, primarily in the area of robotics (motion controller), optical recording devices (multiple speed CDROM drive) technology and high-speed router design.
Ji-Myong Nho received his BS, MS and PhD degrees from Korea Advanced Institute of Science and Technology in 1990, 1994 and 2000, respectively. From 2000 to 2001, he worked as a senior researcher in the Optical Communication Department of Electronics and Telecommunication Research Institute. From 2002 to 2004, he was a full-time instructor in Department of EE of Catholic University at Daegu. He is currently a patent secretary in the Korea Intellectual Property Office. His research interests are in the areas of the security and control and communication networks. He is a member of IEEE, KIEE, KICS and KIISC.
Prof. NP Mahalik, an invited Professor in the department of Mechatronics, Gwangju Institute of Science and Technology (GIST), South Korea, received his BSc Engg. (Electronics), MEngg. (Communication), and PhD (Machine Control) in the year 1989, 1993 and 1998, respectively. He has experiences in authoring and editing research books for technical education. To his credit, Dr. Mahalik has received the prestigious National Overseas Scholarship (1994) and Brain-Korea-21 Fellowship (2001) award from the Indian and Korean governments, respectively, for pursuing research especially in the field of interdisciplinary areas. His research area has been “Networked Control, System Integration, Micromechatronics.” More than 55 research articles and reports have been published.
Kiseon Kim received BEng and MEng degrees, all in electronics engineering, from the Seoul National University, Seoul, Korea, in 1978 and 1980, and his PhD degree from the University of Southern California, Los Angeles, in 1987, in Electrical Engineering-Systems. From 1988 to 1991, he was with Schlumberger in Texas as a senior development engineer where he has been involved in development of wireless telemetry systems. From 1991 to 1994, he was a computer communications specialist for Superconducting Super Collider Lab, in Texas, where he has built detection and analysis systems for large-scale instrumentations networks. He joined Gwangju Institute of Science and Technology (GIST), Korea, in 1994, where he is currently a Professor. His current interests include wideband digital communications system deisgn, analysis and implementation both at the physical layer and at the resource management layer.
Professor BH Ahn is a senior Professor in the Department of Mechatronics, GIST and Director of the System Integration Laboratory with additional administrative position as Vice-President at the institutional level. After serving in the Air Force Tactical Flight Wing as Pilot and subsequently as Chief during 1966–1981, Prof. Ahn preferred to join in the academic field since then. Prof. Ahn, received his PhD in Industrial Engineering in the year 1980 and have achieved many distinctions, awards, publications and patents to his credit. He is the auditor of the Society of Korea Industrial Engineering; member, Society of Korea Human Factors Engineering; member, Board of Directors, Society of Korea CALS/EC. His research interest includes data acquisition/fusion for intelligent transport systems; industrial application of information technology; microtelemanipulation; air traffic control, systems management and reliability analysis. More than 120 research articles and reports have been published in his name.