Two-Way Optical Frequency Comparisons Over 100km Telecommunication Network Fibers

By using two-way frequency transfer, we demonstrate ultra-high resolution comparison of optical frequencies over a telecommunication fiber link of 100 km operating simultaneously digital data transfer. We first propose and experiment a bi-directional scheme using a single fiber. We show that the relative stability at 1 s integration time is 7 10^18 and scales down to 5 10^21. The same level of performance is reached when an optical link is implemented with an active compensation of the fiber noise. We also implement a real-time two-way frequency comparison over a uni-directional telecommunication network using a pair of parallel fibers. The relative frequency stability is 10^15 at 1 s integration time and reaches 2 10^17 at 40 000 s. The fractional uncertainty of the frequency comparisons was evaluated for the best case to 2 10^20. These results open the way to accurate and high resolution frequency comparison of optical clocks over intercontinental fiber networks

Packet Transmission at 100 Gb/s Ethernet

Platforma NetCOPE slouží pro rychlý vývoj hardwarově akcelerovaných síťových aplikací na COMBO kartách. Nezbytnou součástí této platformy je i výstupní síťový modul, který návrháři pomáhá s implementací linkové vrstvy síťového modelu ISO/OSI, především pod- vrstvy MAC. Tato bakalářská práce se zabývá návrhem, implementací a verifikací tohoto modulu pracujícího na rychlosti 100 Gb/s. Dále byla vytvořena aplikace nad platformou NetCOPE pro odesílání krátkých vzorků síťového provozu uložených ve statické paměti QDR. Odesílání je řízeno podle přesných časových značek. Celý systém byl nasazen na kartě COMBO a ověřen pomocí síťového analyzátoru.The NetCOPE platform is used for rapid developement of hardware accelerated network applications on the family of COMBO cards. An essential part of this platform is output network module which helps designers to implement Data Link Layer of the OSI reference model, especially the MAC sublayer. This bachelor’s thesis focuses on design, implemen- tation and verification of such a module operating at speed 100 Gb/s. Furthemore, an appli- cation on the NetCOPE platform was created. It is designed for transmitting short samples of network traffic stored in QDR static memory. Transmission is controlled by precise ti- mestamps. The whole system was deployed on a COMBO card and verified by a network traffic analyzer.

Assessing the Performance of a 60-GHz Dense Small-Cell Network Deployment from Ray-Based Simulations

Future dense small-cell networks are one key 5G candidates to offer outdoor high access data rates, especially in millimeter wave (mmWave) frequency bands. At those frequencies, the free space propagation loss and shadowing (from buildings, vegetation or any kind of obstacles) are far stronger than in the traditional radio cellular spectrum. Therefore, the cell range is expected to be limited to 50 - 100 meters, and directive high gain antennas are required at least for the base stations. This paper investigates the kind of topology that is required to serve a suburban area with a small-cell network operating at 60 GHz and equipped with beam-steering antennas. A real environment is considered to introduce practical deployment and propagation constraints. The analysis relies on Monte-Carlo system simulations with non-full buffer, and ray-based predictions. The ray-tracing techniques are today identified as a relevant solution to capture the main channel properties impacting the beam-steering performance (angular dispersion, inter-link correlation); and the one involved in the present study was specifically enhanced to deal with detailed vegetation modeling. In addition to the user outage, the paper evaluates the evolution of the inter-cell interference along with the user density, and investigates the network behavior in case of local strong obstructions.Comment: IEEE 21st International Workshop on Computer Aided Modelling and Design of Communication Links and Networks (CAMAD), October 201

Millimeter Wave Ad Hoc Networks: Noise-limited or Interference-limited?

In millimeter wave (mmWave) communication systems, narrow beam operations overcome severe channel attenuations, reduce multiuser interference, and thus introduce the new concept of noise-limited mmWave wireless networks. The regime of the network, whether noise-limited or interference-limited, heavily reflects on the medium access control (MAC) layer throughput and on proper resource allocation and interference management strategies. Yet, alternating presence of these regimes and, more importantly, their dependence on the mmWave design parameters are ignored in the current approaches to mmWave MAC layer design, with the potential disastrous consequences on the throughput/delay performance. In this paper, tractable closed-form expressions for collision probability and MAC layer throughput of mmWave networks, operating under slotted ALOHA and TDMA, are derived. The new analysis reveals that mmWave networks may exhibit a non-negligible transitional behavior from a noise-limited regime to an interference-limited regime, depending on the density of the transmitters, density and size of obstacles, transmission probability, beamwidth, and transmit power. It is concluded that a new framework of adaptive hybrid resource allocation procedure, containing a proactive contention-based phase followed by a reactive contention-free one with dynamic phase durations, is necessary to cope with such transitional behavior.Comment: accepted in IEEE GLOBECOM'1

Springbrook: Challenges in developing a long-term, rainforest wireless sensor network

We describe the design, development and learnings from the first phase of a rainforest ecological sensor network at Springbrook - part of a World Heritage precinct in South East Queensland. This first phase is part of a major initiative to develop the capability to provide reliable, long-term monitoring of rainforest ecosystems. We focus in particular on our analysis around energy and communication challenges which need to be solved to allow for reliable, long-term deployments in these types of environments