Digital signal processing for intra- and inter-data centre applications
Lead Research Organisation:
University College London
Department Name: Electronic and Electrical Engineering
Abstract
The effectiveness of many of today's technological advances are enabled by remote access to vast processing and storage facilities; also known as 'The Cloud'. These remotely accessed resources are hosted by data centres, which can host thousands of interconnected servers. Optical fibres are used to support high speed data connection between servers within a data centre (intra-data centre). Similarly, groups of data centres can be clustered together to enhance the size of the available resource pool. These are also connected via optical fibre communication systems (inter-data centre). Due to the challenge of buffering and routing optical signals, routing is currently achieved using optical-electrical-optical conversion, via electrical switches.
However, in the cloud architecture of the future, increasing data traffic demands and computing resources highlight that the capability of electrical network switches will not scale in line with Moore's law. Intelligent optical networks and intelligent transceivers may provide a solution for the next generation data-centre optical networks, thus replacing electrical switching. This PhD will focus on investigating whether ultra-fast optical switching in combination with coherent detection and simplified digital signal processing will be an enabling technology for the continued scaling of data centre network bandwidth. This PhD will advance the fields of both digital signal processing (under a significant computational resource constraint) and all-optical switching, potentially demonstrating the potential of an entirely new optically connected data centre .
Relevance to EPSRC thematic areas:
Information and communication technologies (subthemes: optical communications, digital signal processing, ICT networks and distributed systems, Optical devices and subsystems), Physical sciences.
However, in the cloud architecture of the future, increasing data traffic demands and computing resources highlight that the capability of electrical network switches will not scale in line with Moore's law. Intelligent optical networks and intelligent transceivers may provide a solution for the next generation data-centre optical networks, thus replacing electrical switching. This PhD will focus on investigating whether ultra-fast optical switching in combination with coherent detection and simplified digital signal processing will be an enabling technology for the continued scaling of data centre network bandwidth. This PhD will advance the fields of both digital signal processing (under a significant computational resource constraint) and all-optical switching, potentially demonstrating the potential of an entirely new optically connected data centre .
Relevance to EPSRC thematic areas:
Information and communication technologies (subthemes: optical communications, digital signal processing, ICT networks and distributed systems, Optical devices and subsystems), Physical sciences.
Organisations
- University College London (Lead Research Organisation)
- Chalmers University of Technology (Collaboration)
- Eindhoven University of Technology (Collaboration)
- Microsoft Research (Collaboration)
- Mitsubishi Electric Research Laboratories (Collaboration)
- Microsoft Research (United Kingdom) (Student Project Partner)
People |
ORCID iD |
| Polina Bayvel (Primary Supervisor) | |
| Hubert Dzieciol (Student) |
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| EP/R513143/1 | 01/10/2018 | 30/09/2023 | |||
| 2142343 | Studentship | EP/R513143/1 | 17/10/2018 | 31/10/2022 | Hubert Dzieciol |
| Description | Currently, the majority of data communications travels through an optical fibre which underpins the global network. Moreover, the effectiveness of many of today's technological advances is enabled by remote access to vast processing and storage facilities known as 'the cloud'. These remotely accessed resources are hosted by data centres, which can host thousands of interconnected servers. With the ever-increasing data requirements, understanding how to use fibre capacity to exchange information between the individual or clustered data centres in a smarter way is one of the key enablers of the digital era. By applying intelligent algorithms jointly (or separately) with the design of channel-specific signal formats, I investigate the optimal trade-offs between the computational complexity and a modern optical transceiver's performance. The main goal is to reduce the implementation cost of such solutions in cloud data centres and coherent passive optical networks. Throughout more than two years of my PhD, I have been working on various projects ranging from fast optical switching to intelligent signal modulation for coherent transmission systems in the presence of laser phase noise. I had to learn quickly and apply new knowledge in numerical simulations and, often, in the optical networks lab at UCL. Then, usually in collaboration with colleagues from other research groups/institutions (i.a. Technical University of Eindhoven & Chalmers University), these new findings have been translated into research papers listed in this application. For future work, I plan to look into the following techniques' hardware applications and investigate whether introducing neural networks into short-reach, coherent optical fibre links can significantly improve their spectral and cost efficiencies. Moreover, I plan to experimentally validate the published theoretical findings on the intelligent optical transceivers in the optical lab environment. |
| Exploitation Route | The manuscript "Geometric Shaping of 2-Dimensional Constellations in the Presence of Laser Phase Noise" is put in the context of the 400ZR standard, which is a roadmap to implement the next generation inter-data centre, short-reach optical links. The proposed modulation strategy is accessible through a publicly available dataset and can be implemented in such a link by the industry. In 2021, I published an extension to the aforementioned paper entitled "The Partially-Coherent AWGN Channel: Transceiver Strategies for Low-Complexity Fibre Links". It also comes with a publicly available dataset. |
| Sectors | Digital/Communication/Information Technologies (including Software) |
| Description | The findings on fast optical switching were used to inform R&D work in the area and provided input to the collaborators/founders in Microsoft Research labs. To date, the proposed gradient descent switching is a state of art result in the field. Moreover, the investigation on the intelligent signal design provided a potential extension of the 400ZR inter-data centre standard. The commercially available coherent optical links of 400Gbit/s and their next generations can implement the modulation strategy proposed in the paper to improve their spectral efficiency or reduce the power requirements. Alternatively, the investigated signal design strategy could possibly decrease the links' cost by using cheaper, more noisy, integrated tunable lasers at the same power budget. Furthermore, the intelligent signal design paper and the work on ultra-dense passive optical networks presented at the Summer Topicals conference led to forming a new collaboration with hardware implementation experts from Chalmers University in Sweden. The joint work aims to investigate the optimal hardware application of the proposed solutions that can satisfy the industrial complexity requirements and make the idea economically feasible. |
| Title | Geometric Shaping of 2-Dimensional Constellations in the Presence of Laser Phase Noise |
| Description | 2D geometrically shaped constellations that are simultaneously robust to both residual phase noise and AWGN (GS-RPN) for 8, 16, 32 and 64-ary formats. The presented formats are optimised at the generalised mutual information (GMI) threshold of 0.96m bits/symbol, where m is the number of bits per symbol. Additionally, we added AWGN-only constellations (GS-AWGN) to serve as a reference. Note: This is a supplementary material for journal submission. |
| Type Of Material | Database/Collection of data |
| Year Produced | 2020 |
| Provided To Others? | Yes |
| Impact | This is supplementary material to my manuscript on "Geometric Shaping of 2-D Constellations in the Presence of Laser Phase Noise". The constellations shared in the dataset can be taken by anyone in the field and implemented to their own short-reach coherent system of a similar specification to those proposed in the aforementioned paper. |
| URL | https://ieee-dataport.org/open-access/geometric-shaping-2-dimensional-constellations-presence-laser-... |
| Title | Geometrically Shaped Constellations (2D) for a Low Complexity Partially-Coherent AWGN Demapper |
| Description | 2D geometrically shaped constellations that are simultaneously robust to both residual phase noise (RPN) and AWGN (named as LCM-RPN, where LC is the low-complexity receiver metric from [1]) for 8 to 64-ary PCAWGN reception using a mismatched PCAWGN model. We added AWGN-only shaped constellations (LCM-AWGN) to serve as a reference; the term M is the modulation cardinality.Note: This is a supplementary dataset for journal submission. The uploaded constellations are optimised for a low-complexity PCAWGN demapper from [1], although they may also work well with the exact channel model and other PCAWGN approximations. Each of the constellations comes with linewidth symbol time product, SNR (i.e. signal to noise ratio) and RPN variance. [1] M. Sales-Llopis and S. J. Savory, "Approximating the Partially Coherent Additive White Gaussian Noise Channel in Polar Coordinates," in IEEE Photonics Technology Letters, vol. 31, no. 11, pp. 833-836, 1 June 1, 2019, DOI: 10.1109/LPT.2019.2909803. |
| Type Of Material | Database/Collection of data |
| Year Produced | 2021 |
| Provided To Others? | Yes |
| Impact | Researchers can download a package of geometrically shaped constellations for a wide range of channel configurations to conduct experimental and/or theoretical work with a partially coherent AWGN channel. |
| URL | https://ieee-dataport.org/open-access/geometrically-shaped-constellations-2d-low-complexity-partiall... |
| Description | Chalmers University |
| Organisation | Chalmers University of Technology |
| Country | Sweden |
| Sector | Academic/University |
| PI Contribution | Together with Prof Per Larsson-Edefors and Mr Erik Börjeson (a PhD candidate at Chalmers University), we work on the low-complexity hardware implementation of the ideas proposed in our published (and submitted) papers. |
| Collaborator Contribution | 1. Technical expertise on how to translate numerically simulated algorithms into efficient hardware implementations. 2. Prototyping of the bespoke hardware implementations. |
| Impact | In progress |
| Start Year | 2020 |
| Description | Eindhoven University of Technilogy |
| Organisation | Eindhoven University of Technology |
| Country | Netherlands |
| Sector | Academic/University |
| PI Contribution | Together with our partners at the Eindhoven University of Technology, we work on advanced modulation formats for short-reach optical communications. |
| Collaborator Contribution | Our colleagues at the Eindhoven University of Technology provide their expertise on the topic of channel coding techniques and modulation format design. |
| Impact | 1. Publication of "Geometric Shaping of 2-D Constellations in the Presence of Laser Phase Noise" manuscript in Journal Lightwave Technology 2. An extension of the above manuscript is currently in-peer review. |
| Start Year | 2020 |
| Description | MERL Consultancy |
| Organisation | Mitsubishi Electric Research Laboratories |
| Country | United States |
| Sector | Private |
| PI Contribution | From September 2021 to March 2022, I worked as a remote consultant (intern) in MERL. |
| Collaborator Contribution | My work was focused on developing novel ideas for signal propagation and nonlinearity compensation with physics-informed machine learning. |
| Impact | Due to the confidentiality agreement's terms and conditions, nothing can be reported at present. |
| Start Year | 2021 |
| Description | Microsoft Research Cambridge |
| Organisation | Microsoft Research |
| Department | Microsoft Research Cambridge |
| Country | United Kingdom |
| Sector | Private |
| PI Contribution | 1. Presenting at Optics for the Cloud Virtual PhD Event on 1-2 July 2020, Topic: "Extending Phase Noise Tolerance in UDWDM Access Networks". 2. Research Internship (May 2021 to Sep 2021) |
| Collaborator Contribution | 1. As a Microsoft-funded PhD student, I am hosted and supervised by university faculty members and co-supervised by Microsoft researchers. This brings benefits from discussion, insights, and feedback from practitioners at Microsoft and greater interaction between industry and academia. 2. Organisation of Optics for the Cloud PhD events in 2019 and 2020. 3. During the Internship, I worked on: - Developing digital signal processing techniques for next-generation cloud infrastructure. - Investigating machine learning techniques and their practical implementation. - Practical implementation of free-space and fibre-based optical systems. |
| Impact | 1. Presenting at Optics for the Cloud Virtual PhD Event on 1-2 July 2020, Topic: "Extending Phase Noise Tolerance in UDWDM Access Networks". 2. Contribution to "Geometric Shaping of 2-D Constellations in the Presence of Laser Phase Noise" on the topic of inter data-centre communication standards. 3. Research Internship from May 2021 to Sep 2021 |
| Start Year | 2018 |
| Description | Eighth Van Der Meulen Seminar: Neural Networks in Communication Systems (Workshop) |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Postgraduate students |
| Results and Impact | The 8th Van der Meulen Seminar focused on new directions in studying neural networks for communication systems. In particular, invited speakers sought to answer the questions "Which communication tasks should be first offloaded to neural networks?" and "Can we also learn from neural networks on how to build signal processing algorithms that push the limits of communication through fibres?". The event consisted of a morning workshop session and technical talks by invited speakers from the industry and academia. |
| Year(s) Of Engagement Activity | 2019 |
| URL | https://www.sps.tue.nl/ictlab/event/vandemeulen2019/ |
| Description | Huawei's Vision Forum Europe meeting |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Industry/Business |
| Results and Impact | Presentation on Modeling 'Nonlinearity in Ultra-wideband Optical Fibre Transmission Systems', attended by Huawei Technologies engineers and managers, and other workshop participants |
| Year(s) Of Engagement Activity | 2021 |
| Description | Speaker at Optics for the Cloud event at Microsoft Research |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Industry/Business |
| Results and Impact | I presented on "Extending Phase Noise Tolerance in UDWDM Access Networks" at the Optics for the Cloud Virtual PhD event organised on 1st of July 2020 by Microsoft Research. |
| Year(s) Of Engagement Activity | 2020 |
| URL | https://www.microsoft.com/en-us/research/collaboration/optics-for-the-cloud-research-alliance/ |
| Description | Summer Topicals 2020 |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Industry/Business |
| Results and Impact | I gave a talk on "Extending Phase Noise Tolerance in UDWDM Access Networks" at the virtual Summer Topicals Conference. As a result, we established a collaboration with Chalmers University on real-time hardware implementations of the presented idea. |
| Year(s) Of Engagement Activity | 2020 |
| Description | TRANSNET EAB |
| Form Of Engagement Activity | Participation in an open day or visit at my research institution |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Industry/Business |
| Results and Impact | The advisory board provides critical evaluation and direction to the project leadership, ensuring relevance to EPSRC priorities and project outcomes of the highest quality. The meeting was the second time within the programme that board members have convened. The event saw the advisors respond with an abundance of constructive and positive feedback. |
| Year(s) Of Engagement Activity | 2020 |
| URL | https://transnet.org.uk/news-and-events/435-transnet-eab-2020 |