Top 100 Electronics,China Electric Tools

Having previously foiled the dark plot of the “Empire”, let us look at what the Jedi knights at Ericsson are up to these days. They deserve the title of Jedi as for last 20+ years they have been busy keeping the order in our mobile galaxy by fighting at forefront against the evil plots of the “Empire” and other separatists.

Their recent innovation, the indoor small cell system, named “Dot”, has seen mixed reaction from friends and foes. Even though the architecture can be called the classical closed system from the radio heads, it looks way better than the “Hyper Dense HetNet” proposed by the Imperial army generals, I mean visionaries.

The Dot architecture can be considered an evolution of DAS and provides a much more scalable and cost effective system to overcome the indoor coverage and capacity issue dogging the mobile industry for over a decade. The separation of baseband and radio resources is an elegant solution to provide coverage at the right spots while economizing on the baseband and in turn the spectrum the most treasured asset in the mobile galaxy. One of the biggest advantage of this architecture is that the macro and the small layers are managed by a common baseband pool simplifying the interference management.

Dot system is a two tier architecture, the first leg is a CPRI connection (open but lot of proprietary stuff) between baseband and indoor radio control unit. The second leg is their recent innovation, RFoLAN. Here the digitized RF is sent over Cat 5/6/7 cables commonly deployed to provide Ethernet connectivity in buildings. Interference management in such a system is not a big issue as all of the remote radio heads operate through the common radio resource management at the centralized baseband unit.

The analogy to explain the difference between Dot and Hyper Dense HetNet approach would be to consider a typical mall, where the former approach would require a handful of Dots to enhance the coverage/capacity indoor, the latter would require that each of the shops have to deploy their own little femtos and open the access to everyone. The former approach seems much more plausible and manageable. The bonus is that very similar architecture would work for indoor and outdoor environment. The outdoor cousin of the Dot system is what is known as Centralized-RAN or Cloud-RAN and has seen a lot of interest from operators with fiber rich access networks. After all there is some benefit to eating fiber rich diet

So overall Jedi knights have made a good return (on investment of course). Next we will see how this architecture unfolds in the routing/switching (plumbing) realm. Stay tuned for the next dose of this epic saga …

Footnote: the views in this series of blog are my own personal opinions, no corporate kool-aid involved

View the original article here

 
Researchers used the technology to create a small picoprojector, seen here, which could be embedded in a smartphone, tablet or other device. (Image courtesy of ImagineOptix Corp.)

Researchers from North Carolina State University and ImagineOptix Corporation have developed new technology to convert unpolarized light into polarized light, which makes projectors that use liquid crystal (LC) technology almost twice as energy efficient. The new technology has resulted in smaller, lower cost and more efficient projectors, meaning longer battery life and significantly lower levels of heat.

All LC projectors - used from classrooms to conference rooms - utilize polarized light. But efficient light sources - such as light-emitting diodes, or LEDs - produce unpolarized light. As a result, the light generated by LEDs has to be converted into polarized light before it can be used.

The most common method of polarizing light involves passing the unpolarized light through a polarizing filter. But this process wastes more than 50 percent of the originally generated light, with the bulk of the "lost" light being turned into heat - which is a major reason that projectors get hot and have noisy cooling fans.

But the new technology developed at NC State allows approximately 90 percent of the unpolarized light to be polarized and, therefore, used by the projector.

The ImagineOptix-sponsored research team was also able to use the technology to create a small "picoprojector," which could be embedded in a smartphone, tablet or other device.

"This technology, which we call a polarization grating-polarization conversion system (PGPCS), will significantly improve the energy efficiency of LC projectors," says Dr. Michael Escuti, co-author of a paper describing the research and an associate professor of electrical and computer engineering at NC State. "The commercial implications are broad reaching. Projectors that rely on batteries will be able to run for almost twice as long. And LC projectors of all kinds can be made twice as bright but use the same amount of power that they do now. However, we can't promise that this will make classes and meetings twice as exciting."

Because only approximately 10 percent of the unpolarized light is converted into heat - as opposed to the more than 50 percent light loss that stems from using conventional polarization filters - the new technology will also reduce the need for loud cooling fans and enable more compact designs.

The technology is a small single-unit assembly composed of four immobile parts. A beam of unpolarized light first passes through an array of lenses, which focus the light into a grid of spots. The light then passes through a polarization grating, which consists of a thin layer of liquid crystal material on a glass plate. The polarization grating separates the spots of light into pairs, which have opposite polarizations. The light then passes through a louvered wave plate, which is a collection of clear, patterned plates that gives the beams of light the same polarization. Finally, a second array of lenses focuses the spots of light back into a single, uniform beam of light.

The paper, "Efficient and monolithic polarization conversion system based on a polarization grating," was published July 10 in Applied Optics. The paper was co-authored by Drs. Jihwan Kim and Ravi Komanduri, postdoctoral researchers at NC State; Kristopher Lawler, a research associate at NC State; Jason Kekas, of ImagineOptix Corp.; and Escuti. The research was funded by ImagineOptix, a start-up company co-founded by Escuti and Kekas.

Note to Editors: The study abstract follows.

"Efficient and monolithic polarization conversion system based on a polarization grating"

Authors: Jihwan Kim, Ravi K. Komanduri, Kristopher F. Lawler, Michael J. Escuti, North Carolina State University; D. Jason Kekas, ImagineOptix Corporation

Published: July 10, 2012, Applied Optics

Abstract: We introduce a new polarization conversion system (PCS) based on a liquid-crystal polarization grating (PG) and louvered wave plate. A simple arrangement of these elements laminated between two microlens arrays results in a compact and monolithic element, with the ability to nearly completely convert unpolarized input into linearly polarized output across most of the visible bandwidth. In our first prototypes, this PG-PCS approach manifests nearly 90% conversion efficiency of unpolarized to polarized for +/-11 degree input light divergence, leading to an energy efficient picoprojector that presents high efficacy (12 lm/W) with good color uniformity.

View the original article here