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This work reviews a high-speed, direct modulation underwater optical communication link enabled by a combination of polarization and Orbital Angular Momentum (OAM) multiplexing techniques that results in a data rate of 12 Gbit/s. An efficient technique for combining and sorting multiple OAM modes is presented based on log-polar coordinate transformation diffractive phase only optics.
One of the challenges for tsunami detection by HF radar is to make a first detection at the longest range possible from the shore in order to maximise the warning time for civil responses. A signal-to-noise advantage is obtained by using a dynamic filter in software to lock onto the Bragg spectral lines in mid-range of the radar, and track the Bragg lines into more distant ranges by dynamically changing...
This paper addresses the problem of compensating for motion-induced Doppler frequency offset in multicarrier acoustic communication systems based on orthogonal frequency division multiplexing (OFDM). In mobile acoustic systems, Doppler effect can be sever enough that the received OFDM signal experiences non-negligible frequency offsets even after initial resampling. To target these offsets, a practical...
Deploying a large number of sensing buoys is a powerful tool for oceanographic, marine biology and climate change research. In this work we address the problem of efficient data collection by a team of Unmanned Aerial Vehicles (UAV) from low-power, small buoys with previously unknown locations in complex coastal or remote oceanic regions with aerial restrictions. To tackle this problem we propose...
There is a growing interest in the use of untethered underwater vehicles. These vehicles require robust and error-free underwater communication for transmission of mission-critical data. In contrast, the requirements for sensor payloads are often less stringent. Depending on the type of data, different Quality-of-Service (QoS) demands can be identified. To maximize the bandwidth utilization of underwater...
Underwater free-space optical communication (FOC) is widely used in underwater platforms since its wide bandwidth. Light emitting diode (LED) is the light source in FOC systems. However, LED's spectrum is not concentrated which constraints its transmission distance. Also, its package is comparatively large. In this paper, we use laser diode (LD) as a light source to increase the communication distance...
ROV operations are expensive and there is an urge to improve on their efficiency and speed. The EU project “Effective Dexterous ROV Operations in Presence of Communications Latencies (DexROV)” proposes a solution to those needs by developing a set of hardware and software tools to support the teleoperation of ROVs over a satellite link, i.e., from remote locations including off-shore sites. A core...
Multi-vehicle teams are being used more and more frequently to solve increasingly complex problems [1, 2]. In order for the team to work effectively, the vehicles must communicate to coordinate their efforts. In applications with high quality communication links, the vehicles are able to operate almost as a single entity. But in more harsh and dynamic environments, such as underwater, communication...
This paper presents a technique for extending the bandwidth of chirped active sonar signals. Bandwidth synthesis (BWS) results in improved range resolution, increased signal-to-noise ratio (SNR) and reduced fading due to delay-spread multipath. The approach demonstrated uses a low-order autoregressive (AR) process to model de-chirped segments of the received signal, which are then extrapolated using...
The increasing demand for extracting value out of ever-growing data poses an ongoing challenge to system designers, a task only made trickier by the end of Dennard scaling. As the performance density of traditional CPU-centric architectures stagnates, advancing compute capabilities necessitates novel architectural approaches. Near-memory processing (NMP) architectures are reemerging as promising candidates...
This paper investigates compression for DRAM caches. As the capacity of DRAM cache is typically large, prior techniques on cache compression, which solely focus on improving cache capacity, provide only a marginal benefit. We show that more performance benefit can be obtained if the compression of the DRAM cache is tailored to provide higher bandwidth. If a DRAM cache can provide two compressed lines...
Caches are traditionally organized as a rigid hierarchy, with multiple levels of progressively larger and slower memories. Hierarchy allows a simple, fixed design to benefit a wide range of applications, since working sets settle at the smallest (i.e., fastest and most energy-efficient) level they fit in. However, rigid hierarchies also add overheads, because each level adds latency and energy even...
Heterogeneous memory management combined with server virtualization in datacenters is expected to increase the software and OS management complexity. State-of-the-art solutions rely exclusively on the hypervisor (VMM) for expensive page hotness tracking and migrations, limiting the benefits from heterogeneity. To address this, we design HeteroOS, a novel application-transparent OS-level solution for...
Residential gateways play a key role in providing internet access to home consumers. Nowadays, users in the same home with heterogeneous applications share a common gateway. As such, the gateway becomes the bandwidth bottleneck, leading to impairments and negatively affecting users' Quality of Experience (QoE). In the case of delay sensitive applications like video streaming and online gaming, this...
Widely-used Rate Control (RC) algorithms, such as those in the H.264 encoder, have certain shortcomings for time-sensitive applications such as High Definition Video Conferencing (HDVC): they either respond too slowly to available bandwidth variations, causing degradation in the perceived quality of the video session, or do not optimize video quality for a given available bandwidth. To overcome these...
The high demand of bandwidth from multimedia applications, specially video applications which consume the great majority of the Internet bandwidth, has caused a challenge for service providers and network operators. On the one hand, the allocation of bandwidth in a fair manner for multimedia users is necessary, so that the total utility of all users is maximized for higher quality of experience. On...
This paper presents the design, trade-off of a very high bandwidth variable gain stage, and the practical limits during its implementation as a tunable gain cell in the high speed equalizer for next generation serial electrical / optical communication links. The variable gain stage presented in this work, achieves a bandwidth of above 50 GHz and a tunable gain range of 40 dB. With a very high input...
A 56Gbps PAM-4 optical receiver front-end is presented. In order to reduce the input-referred current noise of the receiver front-end, the shunt feedback resistor Rf of the TIA is enlarged. And, the equalizer is inserted to boost the high-frequency gain and extend the bandwidth. The AGC amplifier using the proposed dB-linear VGAs is further to lower the noise. This PAM-4 optical receiver front-end...
In this paper we propose an SDN-based control plane for the University of Costa Rica. Our campus network faces heavy congestion problems and fails at providing adequate quality of service (QoS). Therefore, we describe a solution that leverages priority-traffic routing to ensure that important services (such as live video streaming) are not as heavily affected by congestion. To this end, we first survey...
This paper proposes a fully integrated 5–12 GHz power mixer in tsmcTM 1P6M 0.18 μm CMOS technology. The power mixer is used to replace the conventional mixer and power amplifier (PA). The circuit consists of an up-conversion Gilbertcell mixer and a wideband and low loss 1:4 Guanella-type differential transmission-line-transformer (DTLT). The power mixer is biased at deep class A/B under a 3.5-V supply...
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