NeTS/NEDG/Medium: Next-Generation Long-Reach Broadband Access Networks
1.1 Award Information
Award No. CNS-0832176; Amount: $586,356 (including a REU supplement and an international cooperation supplement); Duration: September 1, 2008, to February 28, 2013.
1.2 Principal Investigators
1. Biswanath Mukherjee: The PI for the project is Distinguished Professor Biswanath Mukherjee, whose expertise is on network architecture in general, and optical networking in particular. He is responsible for the overall execution of this project, including serving as the lead supervisor of the PhD students trained in this project.
2. Charles U. Martel: The Co-PI for the project is Professor Charles U. Martel, whose expertise is on algorithms in general with an emphasis on network algorithms. He has been working closely with the PI and co-advising the graduate students to ensure that the design and analysis of the algorithms developed are sound and efficient.
1.3 Graduate Students Supported (in part) by the Award
1. Dr. Huan Song worked primarily on the dynamic bandwidth allocation algorithms and protection of Long-Reach Broadband Access Network (LR-BAN). Dr. Song finished his PhD in 2009, and he is working as an engineer at Brocade, Inc. on the topic of broadband access networks for fiber-to-the-X (FTTX) applications.
2. Dr. Lei Shi worked primarily on the scheduling and energy issue of Long-Reach PON. He also worked on how to accommodate the physical-layer issues (i.e., optical signal impairments) in the network architecture of Long-Reach PON. He finished his PhD in 2012, and is now working at Cisco Systems, Inc. on datacenter technology.
3. Dr. Pulak Chowdhury worked primarily on extending the PON coverage by also considering integrated wireless-optical broadband access network (WOBAN) and energy-efficiency issues. He finished his PhD in March 2011; he works for a startup company, Ennetix, Inc., incubated at the UC Davis campus; and he continues to assist the PhD students working on this project with their research.
4. Dr. Marilet de Andrade Jardin (visiting from Universita Politecnica Catalunya) worked primarily on upgrading an existing PON seamlessly in the most cost-effective and disruption-free manner. She finished her PhD in November 2010, and is working as a postdoctoral researcher at Politecnico di Milano, Italy, on optical access networks.
5. Dr. Avishek Nag worked on how to accommodate the physical-layer issues (i.e., optical signal impairments) in the network architecture of Long-Reach PON. As part of an international research supplement of this NSF award, Dr. Nag spent several months at the Indian Institute of Technology, Kharagpur, India, conducting research with our international collaborator, Professor Debasish Datta. He finished his PhD in 2012, and he continues to work as a postdoc on physical-layer issues in Long-Reach PON and other topics.
6. Mr. Saigopal Thota, PhD Candidate, is working primarily on the WOBAN architecture, and deployment of wireless-wireline last-mile access network in remote areas.
7. Mr. Partha Bhaumik, PhD Candidate, has worked primarily on developing an WOBAN prototype in our lab and the performance of applications such as streaming IPTV on optical access networks such as 10G-EPON.
Several Undergraduate students were also supported through a REU supplement. They assisted the PhD students on network control protocols and GUI interface development.
1.4 Other Collaborators
Professor Debasish Datta: Head, G. S. Sanyal School of Telecommunications, Indian Institute of Technology, Kharagpur, India. Professor Datta is an expert on optical communication systems, namely optical technology and system modeling, which is very complimentary to our work on optical network architectures. This cooperation is very important since holistic network design should take into account sound network architectures that are based on accurate physical-layer models. Professor Datta has been collaborating with the PI on research problems for the past 15+ years, but this NSF project is the first to formalize our international research cooperation.
Dr. Glen Kramer: Alumnus from our lab and Chief Scientist of Teknovus, a startup company based in Petaluma CA, acquired by Broadcom; Glen plays a very important role in the global FTTH business, as chairperson of the IEEE standards effort for 10G EPON. Glen has helped our understanding with the directions being taken by the FTTH / PON industry, and he has helped us with the formulation of the seamless and cost-effective PON upgrade problem.
Dr. Lena Wosinska: KTH Sweden. Lena has helped us on the PON upgrade problem also by providing us information on the cost models and typical component costs.
Dr. Xiuzhong (Adam) Chen: Visiting PhD Student from Beijing University of Post and Telecommunications (BUPT), China. Dr. Chen visited our lab for 20 months and worked on the WOBAN architecture.
Ms. Guoying Zhang: Visiting Scientist from China Academy of Telecom Research, China. Ms. Zhang will finish her 1-year visit to our lab in October 2011; she worked on OFDM-based network architectures, including their potential application in access networks.
Dr. Sudhir Dixit: HP Labs. Dr. Dixit heads HP Labs India, and is a long-term research collaborator of the PI. He is hosting Mr. Saigopal Thota as an intern in his lab, and co-supervising his research on the WOBAN architecture.
2 Summary of Research Activities and Findings
2.1 General Background
One way to reduce the operational cost (OpEx) of a communication network is to lower its number of active sites such as points of presence (PoP) and local exchanges. Passive optical networks (PON) can meet this goal. By eliminating the power supply along the fiber path from the central office (CO) to end users, which contributes a large portion of the OpEx, and by sharing a large part of the network cost among multiple users, PON is the most promising fiber-to-the-home (FTTH) access network, and is being deployed worldwide. But further reduction of active sites can lead to larger distances to be covered by the access network, leading to even lower cost per user.
Long-Reach Broadband Access Network (LR-BAN), also known as a Long-Reach PON (LR-PON), is a more cost-effective solution for future broadband optical access networks. LR-BAN extends the coverage span of PONs from the traditional 20 km range to 100 km and beyond by exploiting optical amplifier and wavelength-division multiplexing (WDM) technologies (see Fig. 1). Compared with traditional PON, LR-BAN consolidates the multiple optical line terminals (OLTs) and central offices where they were located, thus significantly reducing the corresponding OpEx of the network (while serving the user base through their Optical Network Units (ONUs)). By providing extended geographic coverage, LR-BAN combines optical access and metro networks into an integrated system. Thus, cost savings are also achieved by replacing the metro ring network such as Synchronous Optical Network (SONET) with a shared optical fiber. In general, the LR-BAN can simplify the network, reducing the number of equipment interfaces, network elements, and even nodes. Note our proposed “ring-and-spur” architecture for the LR-BAN in Fig. 1, which “reuses” the “ring” structure of the metro network (and hence provides fault tolerance for a single fiber cut) while each traditional PON segment is a “spur” from the ring. Strictly speaking, the LR-BAN is not passive because it has a few active elements such as optical amplifiers and/or optical add-drop multiplexers where the CO was located previously, but the name LR-PON (or SuperPON) is widely used in the literature since it is derived from the PON; but we prefer to call it LR-BAN (and not LR-PON) since it is not passive.
Fig. 1. A Long-Reach Broadband Access Network (LR-BAN), also known as a “ring-and-spur” architecture.
Based on the promising aspects of LR-BAN, our research is investigating methods which can utilize this network in an effective way to serve people’s needs. With the help of this NSF award, our studies have led to important research results, as indicated below.
2.2 Research Contributions
Please check our publications for detailed research contributions.
· Performance of Access Network (EPON) in Streaming IPTV [1-2]
· Power Management in WDM-PON 
· EPoC (Ethernet PON over Coax) Architecture 
· Energy Efficient Dynamic Wavelength Allocation in LR-BAN 
· Energy Efficient LR-BAN with Sleep-Mode ONU 
· BER-Aware Wavelength Allocation Schemes for LR-BAN with AWG 
· Optical Access Networks: Exploiting Wireless Connectivity for Robustness and a Prototype 
· Strategies for Evolution of PONs 
· Energy Efficient Design of LR-BAN 
· Energy Efficiency Operation of a LR-BAN 
· Survey of Energy Efficiency Approaches in Telecom Networks 
· Energy Efficiency in WOBAN 
· Optimizing the Migration to Future-Generation PONs 
· A Comprehensive Survey on Long-Reach Optical Access Networks 
· Multi-Thread Polling: A Dynamic Bandwidth Distribution Scheme in Long-Reach PON [16-17]
· Behavior-Aware User-Assignment in Long-Reach PON 
· Hardware-Accelerated Protection in Long-Reach PON 
3 Ongoing Research Activity/Plan
Our ongoing research activity/plan includes: (1) continuing to develop efficient algorithms to operate and upgrade Long-Reach Broadband Access Networks (LR-BANs), where upgrade means adding more capacity to the network seamlessly (because of increasing number of users and their increasing bandwidth demands) without disrupting existing users, and to make the corresponding network architecture more service-centric; (2) extending the coverage of the optical access network not only into the network cloud (i.e., covering the metro network) but also the wireless access domain so that we have an extended-reach hybrid wireless-optical broadband access network (WOBAN) with coaxial and cellular (LTE, WiMax, etc.) front end, and develop the corresponding networking problems and challenges; and (3) developing energy-efficient configurations and operations of the LR-BAN as well as the WOBAN with coaxial and cellular (LTE, WiMax, etc.) front end. These are important, interesting, and challenging research problems.
5. Project Activities and Findings
Research and Education Objectives:
The research and education activities of this project include the creation of new knowledge and understanding on the design, deployment, and operation of the novel Long-Reach Broadband Access Network (LR-BAN) architecture and resource-allocation algorithms, as well as seamless network evolution to accommodate traffic growth. The objective is to develop the next generation of broadband access networks which are cost-effective, energy-efficient, and easy to upgrade. We have extended the scope to also study the performance of services (such as streaming IPTV) over the broadband optical access network, energy-efficient operation of the WDM-PON, etc.
Our major findings are that the current and emerging access networks such as Passive Optical Networks (PONs) which provide Fiber-to-the-X (FTTX) service and the regional metro networks which are optical rings can be operated in an integrated manner to achieve the Long-Reach Broadband Access Network (LR-BAN) architecture. This leads to the 'ring-and-spur' architecture which exploits the existing metro ring infrastructure to provide fault tolerance from a fiber cut, while each traditional PON represents a 'spur'. Effective operation of LR-BAN can be achieved through (1) energy-efficient network design and operation, (2) extending the access network to the integrated wireless-wireline access network which is also energy efficient, and (3) cost-effective, seamless, and minimal-disruption network upgrades to accommodate network traffic growth, as several of our publications have shown. Cost-effective network architectures to address the above problems have been developed and studied. Additional findings include the following: (4) the optical access network such as 10G-EPON can support a large number of concurrent IPTV channels with minimal buffer size at moderate rates of video compression; (5) significant energy saving is achieved by adapting active wavelengths to varying traffic in WDM-PON, and only minor reconfiguration and limited ONU wavelength tunability are needed; etc.
Our project should have a significant impact in demonstrating the viability of the LR-BAN as a cost-effective solution for broadband access. At his November 4, 2009, Plenary Speech at the Asia Communications and Photonics Conference (ACP 2009) (http://www.acp-ce.org/), the CTO of China Telecom, Leping Wei, who is well-known to the PI, stated the importance of LR-BAN for cost-effective broadband access, especially for emerging high-capacity applications such as video-on-demand, IPTV, storage and grid applications. Many other leaders in the networking industry are making similar statements.
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Contributions Within Discipline:
New knowledge is being created by this project on the design and operation of the novel Long-Reach Broadband Access Network (LR-BAN) architecture, resource-allocation algorithms, and their energy-efficient design and operation; integrated wireline-wireless access network architecture; performance of services such as streaming IPTV over optical access networks; as well as seamless network evolution to accommodate traffic growth. We have shown that Passive Optical Network (PON) which provides Fiber-to-the-X (FTTX) service and the regional metro optical ring network can be integrated to achieve the Long-Reach Broadband Access Network. We have developed an experimental prototype of a wireless-optical broadband access network (WOBAN) on which we are performing tests and experiments to demonstrate the various properties of our proposed architectures, algorithms, and methods.
Contributions to Other Disciplines:
Our research group enjoys support from industry such as Teknovus/Broadcom, NTT, Nokia, Fujitsu, ETRI Korea, NEC, Siemens, HP, and Huawei. Also, as broader influence of his NSF-supported research, the PI serves or has recently served as a Member of the Board of Directors or on the Technical Advisory Board of several companies: IPLocks, Teknovus, Intelligent Fiber Optic Systems (IFOS), and LookAhead Decisions Inc. (LDI). ETRI, a leading telecom research organization in Korea is collaborating with us on the related problem of integrated wireless-wireline integrated access network. HP Labs is supporting the research of one of our PhD students on the WOBAN architecture and also co-supervising this student’s research.
Contributions to Human Resource Development:
This NSF project has supported (in part) the research of seven PhD students (five completed, including one visiting from Europe for a year) and three UG students. One PhD student, Dr. Huan Song, has graduated from UC Davis, and he is contributing to the workforce at Brocade, Inc., working on optical access network solutions, the topic of his PhD research. Another PhD student, Dr. Pulak Chowdhury, has also graduated from UC Davis, where he is working as a postdoc on energy conservation in networks. The Visiting PhD student, Dr. Marilet de Andrade defended her PhD Dissertation at her home institution (Universita Politecnica Catalunya), and she is now working as a psotdoc in Italy on FTTX network architectures. Dr. Lei Shi finished his PhD recently on energy-efficient access networks and is now working at Cisco Systems, Inc. on datacenter networks. Dr. Avishek Nag, who also finished his PhD recently and is continuing as a postdoc at UC Davis, spent several months at the Indian Institute of Technology, Kharagpur, India, conducting research with our international collaborator, Professor Debasish Datta. PhD student Saigopal Thota is working closely with HP Labs. Another PhD student Partha Bhaumik is working on optical-coax access network integration. The role of this NSF project in human resource development has been excellent.
Contributions to Resources for Research and Education:
A very good survey article on Long-Reach PON has appeared in IEEE Communications Surveys and Tutorials. Another review article on energy efficiency in telecom networks, including access networks, appeared in IEEE Communications Surveys and Tutorials (Fourth Quarter 2010). Both of these surveys are very well cited. Several of our other papers on this topic are tutorial oriented and published in IEEE Communications Magazine. The PI (Mukherjee) serves as the Series Editor of Springer’s “Optical Networks Book Series” which publishes a variety of books on optical networking, including Broadband Optical Access, under his supervision and guidance. PI Mukherjee also Co-Guest-Edited the September 2012 IEEE Communications Magazine Special Issue on “SERVICE INTEROPERABILITY IN ETHERNET PASSIVE OPTICAL NETWORKS (SIEPON)”, a very important topic for guiding the optical networking industry. PI Mukherjee also Co-Guest-Edited the May 2012 Centennial Issue (vol. 100) of the Proceedings of the IEEE on “The Evolution of Optical Networking”. We have developed an experimental prototype of a wireless-optical broadband access network (WOBAN) on which we are performing tests and experiments to demonstrate the various properties of our proposed architectures, algorithms, and methods.
Contributions Beyond Science and Engineering:
Alumni from our lab – who have been primarily trained by NSF support over the past two decades – have been gainfully employed in various companies and universities. Nearly a dozen of them have been women. Three of the PI’s PhD alums – Dr. Shun Yao, Dr. Laxman Sahasrabuddhe, and Dr. Abu Ahmed Sayeem Reaz – chose to pursue law. The first two have finished law school and are practicing lawyers. Three other alums – Dr. Dhritiman Banerjee, Dr. Canhui (Sam) Ou, and Dr. (Ms.) Xiaoling Qiu – are working in the finance sector where they are utilizing their technology/telecom background. Another alum, Dr. Glen Kramer, was Chief Scientist of Teknovus, a startup company based in Petaluma CA, which was recently acquired by Broadcom, and he plays a very important role in the global FTTH business, being the chairperson of the IEEE standards effort for 10G EPON. Ms. Guoying Zhang, Visiting Scientist in our lab for 12 months, returned to her job at the China Academy of Telecom Research, and she is continuing to play a very significant role in influencing worldwide telecom standards through the ITU and the IEEE. Dr. Xiuzhong (Adam) Chen, Visiting PhD Student in our lab for 20 months, is also working at the China Academy of Telecom Research, and influencing worldwide telecom standards. Dr. Joonho Choi, another alumnus from our lab, is the Director for International Liaison for the Korea Communications Commission (KCC), equivalent to the FCC in South Korea. Thus, NSF’s support of our research program over the past two decades is having strong impact in disciplines beyond science and engineering.
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Biswanath Mukherjee (http://networks.cs.ucdavis.edu/~mukherje/)
Office: 3037 Kemper Hall
E-mail: mukherje AT cs dot ucdavis dot edu
January 12, 2013