SDN ‐ based WiFi ‐ VLC Coupled 5G System

In IEEE WoWMoM 2018 conference, I presented our work on an SDN-based WiFi-VLC Coupled System for Optimised Service Provision in 5G Networks. Visible Light Communication (VLC) is a powerful supplement, which has gained tremendous attention recently and has become a favorable technology in short-range communication scenarios for the Fifth Generation (5G) networks. VLC possesses a number of prominent features to address the highly demanding 5G system requirements for high capacity, high data rate, high spectral efficiency, high energy efficiency, low battery consumption, and low latency. However, this prominent performance is limited by the imperfect reception, since line of sight channel condition may not always exist in practice. The paper presents and experimentally validates a SDN-assisted VLC system, which is coupled with WiFi access technology in order to improve the reliability of VLC system, reassuring zero packet loss reception quality due to misalignment or path obstructions or when the user is moving between two consecutive VLC transmitters and experience “dead coverage zones”.

fig1

The experimental setup of this paper includes an SDN network domain, which is controlled by Ryu controller that is capable of executing python-based SDN apps. The CPE is a laptop equipped with a USB VLC receiver and an Arduino-based luminance detector, placed next to the VLC dongle.

The experimental topology complements the VLC technology with a 2.4GHz WiFi 802.11g access point, which was used in the experiment as a dynamically coupled access technology for the zones that the user has poor reception quality, such as the dead reception zones between two successive VLC transceivers. An SDN app was developed in order to handle the seamless switching of the access technology (i.e. WiFi or VLC) used each time in order to maintain good reception quality.

fig2As it was expected, while the user is moving away from the center of the LED light, the lx value (and respectively the SNR value) is decreasing, which means that the reception quality drops and the http-streaming video service from normal playback is starting to appear occasional pauses. Gradually the lx value reaches to zero as the users is located in a dead reception zone between two successive lamps, where the video service provision is paused/interrupted (packet loss reaches 100%/blue line). The video service playback re-initiates when the user reaches the coverage area of the next VLC transmitter, since all the lamps are broadcasting the same content, and therefore the distance from the next light source is decreasing and therefore the lm value and the SNR value are gradually increasing.

The experiment was repeated placing the CPE at the same distances, but with the SDN controller enabled and the proposed SDN-app active and properly configured. The user requested the HTTP streaming video service and once the service started, she/he started to move from distance equal to zero with step of 30cm, towards the next VLC lamp. When she/he covered a distance of two meters (i.e. at the dead coverage zone between the two lamps), then the packet loss started to increase (as is it observed in the figure above in oragne). Then the SDN-app detected the loss of the ctrl_messages via the VLC channel and once the window of 2 seconds had been completed, the SDN-app instructed via the SDN Controller appropriate Openflow commands to be applied on the OVS switch for diverting the downloading flow to WiFi. The switching process performed seamlessly to the end-user, which resulted in maintaining the video service delivery intact, without any service interruption or quality degradation.

Read the full paper. Available here.

Advertisements

Ultra HD Premium: The commercial logo of HDR TV

High dynamic range imaging (HDR) is a technique used in imaging and photography to reproduce a greater dynamic range of luminosity than is possible with standard digital imaging or photographic techniques. The aim is to present the human eye with a similar range of luminance to that which, through the visual system, is familiar in everyday life. The human eye, through adaptation of the iris and other methods, adjusts constantly to the broad dynamic changes ubiquitous in our environment. The brain continuously interprets this information so that a viewer can see in a wide range of light conditions.

For imaging, HDR, as its name implies, is a method that aims to add more “dynamic range” to photographs, where dynamic range is the ratio of light to dark in a photograph. In principle, when HDR is enabled during that image capture, the camera instead of taking one photo, three photos are taken at different light exposures. Then, either with an automatic software (as is done at Mobile Phone cameras) or with a sophisticated image editing software, the pictures with the different exposures are overlayed  and the best parts of each photo are highlighted.

Toward the HDR TVs, the UHD Alliance (UHDA) [1] of TV manufacturers, broadcasters and film producers have decided to create a new brand logo beyond UHD, the Ultra HD Premium that defines the technical specifications that a TV must meet in order to deliver a HDR/premium 4K experience.

sony_4k_hdr_uhd_logo-600x300

The UHDA’s new ULTRA HD PREMIUM specifications cover multiple display technologies and reference established industry standards and recommended practices from the Consumer Technology Association, the Society of Motion Picture and Television Engineers, the International Telecommunications Union and others. Moving further forward, UHDA Launches “ULTRA HD PREMIUM” Logo and Certification Licensing for Ultra HD Blu-ray Disc Players.

Summarizing the minimum requirements [2]:

Minimum resolution of 3,840 x 2,160 – which remains the same as the 4K/Ultra HD TVs.

10-bit color depth – In contrast to the 8-bit color space that Blu-Ray players use today, the UHD Premium TVs must be able to receive and process a 10-bit colour signal, often called ‘deep color’, supporting over a billion colors.

Minimum of 90% of P3 colors – To certify a TV as an Ultra HD Premium TV, the TV must be able to display 90% of the colors defined by the P3 color space [3] (More info here).

Signal Input– BT.2020 color representation [4]

High Dynamic Range – SMPTE ST2084 EOTF [5]

Minimum dynamic range – To qualify with UHD Premium, a TV should meet a minimum standard for the maximum and the minimum brightness it can achieve.

There are two different requirements in order to accommodate the pros and cons of different TV technologies.
  1. Aiming at LED TVs: More than 1,000 nits peak brightness and less than 0.05nits black level
  2. Aiming at OLED TVs: More than 540 nits brightness and less than 0.0005 nits black level

Please note that TVs could be certified Ultra HD Premium retroactively, but few TVs released in 2015 can meet the standard.

References