PhD Amornrat Jirattigalachote

Where are you from and where did you study before coming to school of ICT?

– I am from Phitsanulok, one of the oldest cities in lower northern region of Thailand. I graduated my Bachelor’s degree in Telecommunication Engineering from King Mongkut’s Institute of Technology Ladkrabang in Bangkok. After a few years of working in Thailand, I came to Stockholm for my Master study and in the beginning of 2008 I received my Master degree with specialization in Photonics from KTH.

What is your topic and why did you choose it?

– My topic is “Provisioning Strategies for Transparent Optical Networks Considering Transmission Quality, Security and Energy Efficiency”. This topic was initially selected by my supervisor. However, after studying the problems, I have found that these problems are very interesting and challenging, and I think that my background in telecommunication engineering and photonics fit well with this topic.

Describe your topic in short

– Internet traffic volume is forecasted to increase by around 30% each year. This continuous growth of traffic demands creates new challenges for communication networks. Among different transport network technologies, transparent optical networks based on wavelength division multiplexing (WDM) technology are considered to be the most promising option to support this rapidly growing traffic demands. With the ability of such networks to transparently carry the optical signal from source to destination through all-optical channel or lightpath, the electronic processing of the tremendous amount of data can be avoided and the optical-to-electrical-to-optical (O/E/O) conversions at intermediate nodes can be eliminated. The absence of O/E/O conversions brings the benefit in terms of transparency to bit rate, signal format, and protocol. Moreover, transparent WDM networks consume relatively low power compared to its electronic-based IP network counterpart. However, transparent networks have also some drawbacks. By transparently transmitting the optical signal from source to destination, the optical signal quality might be degraded due to the effect of physical-layer impairments accumulated along the lightpath. Furthermore, without signal regeneration, transparent networks are also highly vulnerable to malicious physical-layer attacks. On the other hand, transparent WDM networks have the potential to consume even less power by targeting the inefficiencies of the current provisioning strategies used.

The work in my thesis addresses the three important aspects just mentioned. In particular, my thesis focuses on the provisioning strategies specially devised to target the lightpath transmission quality, the network security, and the reduction of the network energy consumption.

Tell us something about your results

– In the context of transmission quality, in my thesis we propose an Impairment Constraint Based Routing algorithm supporting differentiation of services. Although a number of Impairment Constraint Based Routing (ICBR) algorithms have been proposed in the literature, none of them considers the fact that next generation networks and future Internet are expected to support a wide variety of services with disparate requirements for transmission quality. To address this issue, our approach takes into account the effect of physical-layer impairments during connection provisioning phase where various signal quality thresholds are considered for accepting/blocking connection requests, depending on the signal quality requirements of the connection requests. Results show that our approach is not only able to achieve a significant improvement of network performance in terms of connection blocking but also shows high adaptability to heterogeneous fiber scenarios.

Regarding the network security in terms of vulnerability to physical-layer attacks, we propose to use power equalizers based on wavelength-selective attenuators at the network nodes to efficiently limit the propagation of high-power jamming attacks. Due to the increased cost of network node installed with power equalizers, we also develop a set of heuristic algorithms, including Greedy Randomized Adaptive Search Procedure (GRASP) approach, for power equalization placement problem. The objective of our algorithms is to minimize the number of power equalizers needed to reduce the attack vulnerability to the desired level. Results show that our GRASP approach allows for 50% reduction of the sites with the power equalizers while offering the same level of attack propagation limitation as it is possible to achieve with all nodes having this additional equipment installed.

About energy efficiency, we focus on the power consumption of survivable WDM network with dynamically provisioned 1:1 dedicated path protected connections. We find that the network power consumption can be significantly reduced by setting all unused protection resources into a low-power, stand-by state (or sleep mode) during normal network operations. Thus, to optimize the power savings, we propose and evaluate a series of energy-efficient strategies specifically tailored around the sleep mode functionality. Our results reveal the existence of a trade-off between power saving and connection blocking. However, they also show that with the right provisioning strategy it is possible to save a considerable amount of power with a negligible impact on the connection blocking.

What will the future bring for your research topic?

– I think all aspects considered in my thesis will become more and more important, as I mentioned previously that with the brisk growth of Internet traffic volume optical networks are considered as the most promising solution.

What are your future plans?

– I would like to continue doing research in academia for some time.

You can find Amornrats thesis here .