Visible light communication – An architectural perspective on the applications and data rate improvement strategies

With the increasing number of edge devices in large-scale edge systems, more and more data are collected to be processed. In such big data scenarios, there is a resurgence of interest in main-memory analytic databases because of the large RAM capacity of modern servers and the increasing demand for real-time analytic platforms. In such databases, join is at the heart of almost every query plan. Join also stays as a time-consuming operation when the denormalization overhead is too large to be applicable. However, the current implementations of these operations have not fully leveraged the new features (eg, SIMD, multi-core) provided by the modern hardware. The goal of this article is to design efficient algorithms for joins by judiciously exploiting every bit of RAM and all the available parallelisms in each processing unit. For join operations, hash joins have been studied, improved, and reexamined over decades.In this article, we propose to utilize a secondary index to improve hash joins without the physical partitioning. Specifically, in the build phase, the hash values are scattered evenly into the logical partitions of the hash table; in the probe phase, the secondary index is used as the hints to re-order the probing sequence, such that the locality of the hash probing is increased. We benchmark the performance of the proposed techniques in our column-store research prototype. Extensive experiments on the synthetic data and the real data show that our methods offer significant performance improvement over their counterparts.

Section: Accelerating Hash Joins With Imprintsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Utilizing the column imprints to accelerate no‐partitioning hash joins in large‐scale edge systems

Liu

2020

“…Short‐term flicker severity is another important performance metric for quality illumination design. It has been pointed out by Saadi et al that flickering is one of the challenging issues in the VLC system and can cause grave detrimental physiological disorders in humans . The IEC also mentioned the threshold of irritability due to change of luminance of the artificial light source .…”

Section: System Performancementioning

confidence: 99%

Daylight integrated indoor VLC architecture: An energy‐efficient solution

Chatterjee

Sabui

2019

In an indoor space, visible light communication (VLC) can form a promising enhancement of future illumination infrastructures with communication functionalities. This illumination infrastructure consumes 20% of the total energy consumption in the world. In this perspective, daylight integration with indoor VLC system is a promising area of research to conserve a considerable amount of energy. This paper deals with the design and practical realization of an energy‐efficient indoor VLC system through daylight integration. Dimming control mechanism using continuous current reduction topology is adopted to design the transmitter section of the VLC system. Thrust has been given to accomplish the required communication performance in terms of the bit error rate and illumination performance in terms of average horizontal illuminance and short‐term flicker severity. Both the communication and illumination performances have been evaluated under five different daylight conditions. At maximum ambient daylight condition, 37.29% of total energy has been saved, while the bit error rate lies in the order of 10−10. Simultaneously, satisfactory illumination performance in accordance with international guidelines has been achieved.

“…Mobile phone and laptop users can also enjoy broadband services using VLC which has recently matured. This technology can provide a significant range of benefits to the railway industry not only within the trains but inside stations as well; since every source of light on a train or inside a station could be used as a wireless hot‐spot 12,13 . However, some light sources have advantages that made the VLC technology began to be used in various indoors and outdoors applications.…”

Section: Introductionmentioning

confidence: 99%

Communication systems of high‐speed railway: A survey

Gheth

Rabie

Adebisi

et al. 2021

Modern railway services are required to deliver good quality services to the passenger throughout the whole journey. These include improved performances, safety, and reduce delays. There is also the requirement for in‐train customer experience such as infotainment and access to reliable communication systems. The railway industry has employed different types and generations of communication systems in recent times. Signaling systems were used at the early stage of the railway services. Today, communication systems such as the second‐generation communication system, also known as the global system for mobile communications (GSM), the Third‐generation (3G) and the Fourth‐generation (4G) are utilized in the railway industry. In this paper, we present a brief history of railway communication systems, their features and applications. In addition, we discuss the technical challenges and potential solutions of in‐train communication systems and how data can be distributed on‐board and between the train coaches using state of the art and hybrid communication technologies.