Partha Bhaumik

Software-defined optical networks (SDONs): a survey

This paper gives an overview of software-defined optical networks (SDONs). It explains the general concepts on software-defined networks (SDNs), their relationship with network function virtualization, and also about OpenFlow, which is a pioneer protocol for SDNs. It then explains the benefits and challenges of extending SDNs to multilayer optical networks, including flexible grid and elastic optical networks, and how it compares to generalized multi-protocol label switching for implementing a unified control plane. An overview on the industry and research efforts on SDON standardization and implementation is given next, to bring the reader up to speed with the current state of the art in this field. Finally, the paper outlines the benefits achieved by SDONs for network operators, and also some of the important and relevant research problems that need to be addressed.

Exploiting wireless connectivity for robustness in WOBAN

This article studies how next-generation optical access networks can exploit the properties of wireless connectivity to provide improved quality of service to users, and reports on a corresponding experimental prototype as well. Optical access networks using the passive optical network architecture are being increasingly deployed worldwide for fiber-to-the-home/business applications. While a PON can support higher data rates, it suffers from its tree architecture since it is vulnerable to a fiber cut on its tree¿s trunk, which will disrupt service to its users. However, by exploiting the properties of wireless connectivity, such as a wireless mesh in the front-end, the network can be made more robust. In case of a network element failure, an alternate path through the wireless-wireline integrated network may be selected, if it exists. Such a network can provide reliable high-capacity connectivity to untethered wireless devices which may be mobile as well. For such wireless-optical broadband access networks, we study a Risk-Aware Routing (RAR) algorithm to make it fault-tolerant and self-healing in case of failures. We also report on results from an experimental prototype developed in our laboratory.

A novel direction-based diurnal mobility model for handoff estimation in cellular networks

In real-life scenario where users mostly know their destinations a priori, their movement is not purely random (as assumed in random walk model); rather it is somewhat direction-based and depends on the present location and the final destination. For instance, an office goer often returns home in the evening (i.e., mobility is diurnal). While no existing research has studied direction-based diurnal mobility model which could be of immense importance to cellular operators, we formulate a Markov model for such movement and give a theoretical upper bound of cell boundary crossings (i.e., expected number of handoffs) by the user. We have theoretically calculated the number of handoffs based on our proposed mobility model and verified the result in a simulated environment. We find that a majority of inter-RNC/MSC handoffs [4] comes from only a few cells which should be made dual-homed by the operators for their cost reduction.

IPTV over EPON

In an increasingly content-centric world where users consume large amounts of multimedia content, video delivery platforms over packet networks, such as Internet Protocol Television (IPTV), are gaining rapid popularity. At the same time, to serve the ever-increasing bandwidth demand from users, access networks, traditionally the bottleneck for high-bandwidth applications, are also undergoing rapid evolution. Forecasting how streaming IPTV over a network will perform is challenging as the data rate of a video stream varies with scene, time, framerate, and encoding. Nevertheless, it is important to evaluate the performance of an access network for IPTV traffic to ensure good Quality of Service (QoS) for users. Using video traces for such evaluation requires multiple video traces to represent different scenarios and generally involves slow I/O-based operations, such as file reading. To overcome these limitations, in this paper, we explore several aspects of modeling IPTV streaming, and present a synthetic video trace generator that closely resembles the empirical IPTV traces. Our analysis confirms that our synthetic video trace follows the statistical properties of empirical videos, and its resultant data rate is representative of the IPTV video streaming. Next we study the performance of Ethernet Passive Optical Network (EPON) in streaming IPTV by using the generated synthetic trace. Parameters of interest are the number of parallel video streams supported, the effects of the degree of video compression, average and maximum packet delays, and packet delay variances (jitter). It is shown that 10G-EPON can support a large number of parallel IPTV channels at moderate rates of video compression.

On downstream transmissions in EPON Protocol over Coax (EPoC): An analysis of Coax framing approaches and other relevant considerations

We present different mechanisms for downstream transmissions in the coax segment of Ethernet Passive Optical Network (EPON) Protocol over Coax (EPoC). EPoC is the transparent extension of EPON over a cable operator’s Hybrid Fiber-Coax network. For managing and controlling such a hybrid network, a network operator prefers to have a unified scheduling, management, and quality of service environment that includes both the optical and coax portions of the network. In EPoC, this is achieved by extending the EPON Medium Access Control to run over the coax physical layer, to have a centralized end-to-end network control from the cable head-end to the end users premises. In this paper, we focus on the downstream transmissions in EPoC. We study three different framing approaches for downstream coax frames based on how sub-carriers in an orthogonal frequency division multiplexed symbol are modulated. We discuss the merits and demerits of each approach and then compare them based on their control overheads and the maximum average data transmission rates each of them can achieve. We analyze how different parameters such as modulation profile, symbol duration, number of sub-carriers and length of resource blocks affect the data rates and the performance of downstream transmissions. We present simulation results to examine the implications of these factors on packet-level performance, such as delay. The results indicate that dynamic and hybrid framing approaches tend to perform better than static approaches, when traffic and usage pattern are identical to those in real-world scenarios. Finally, we outline the important engineering and research problems in this area which can be topics of future research.

Performance of 10G-EPON in streaming IPTV

Performance of 10G-EPON in streaming IPTV is studied using a synthetic trace generator. Parameters of interest are number of concurrent channels, degree of video compression, average and maximum packet delays, packet delay variance, and buffer sizes in ONUs. It is shown that 10G-EPON can support a large number of concurrent IPTV channels with minimal buffer size at moderate rates of video compression.

On downstream coax framing in EPON protocol over coax (EPoC)

In this short paper, we propose three different framing approaches for downstream transmissions in the coax segment of EPON Protocol over Coax (EPoC), based on how subcarriers in an orthogonal frequency division multiplexed (OFDM) symbol are modulated. We analyze the merits and demerits of each approach, and then compare them based on their control overheads and the maximum average data transmission rates each of them can achieve.

Towards green NG-PON2 systems

We study real-time energy saving in NG-PON2 systems, i.e., TWDM-PON, and analyze impacts on quality of service and reconfiguration overhead. Our proposed methods are compatible with existing EPON/GPON protocols.