Local Wireless Communications

Broadband Wireless Local Area Networks

The market for mobile services looks set to continue growing at near exponential levels over the next five to ten years. With the increasing popularity of mutimedia services supplied over the fixed network, services such as: web browsing, video conferencing and video on demand, it is for sure only a matter of time before users will demand higher bandwidth mobile access. Advances in displays, battery technology and processing power have also made it possible for users to afford and carry around laptops and palmtops. The prospects for the delivery of mutimedia services to these users is, however, crucially dependent on the development of low cost physical layer delivery mechanisms.

To address the bit rate limitation problem of current cellular phone systems, we are examining the concept of adaptive rate delivery of future mobile multimedia services. In this model, services are provided by a combination of delivery technologies giving: low bit rates (<100 Kbits/s) with universal coverage; medium bit rates over campus-like areas (< 55 Mbits/s) and very high bit rates (>100 Mbits/s) services in much localized areas. Example physical layer technologies are: GSM, UWB and optical wireless for the high-bandwidth islands (hot spots), e.g., classroom, hotel lobby, shopping mall, airports, train stations, etc.

Future Wireless World Vision

Broadband Data Communications using Energy-Efficient White LEDs on Aircraft Power-lines

Broadband power-line communication has advanced through last decade and it is going to be a mature access technique in near future. Meanwhile, optical wireless communication through energy-efficient lighting LEDs has been investigated, recently. In this project, it is shown that marriage of these two techniques may create an efficient delivery mechanism for delivering the promise of broadband access onboard an aircraft, while providing efficient and low-cost lighting. The potential capabilities of these two techniques are examined.

M. Kavehrad, Z. Hajjarian and A. Enteshari,”Broadband Data Communications using Energy-Efficient White LEDs on Aircraft Power-lines,” Proceedings of IEEE ICNS, Bethesda, MD., May 2008. PRESENTATION

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Triple Play Using Power Lines and White Light Emitting Diodes for Home Networking

The increasing interest in modern multimedia applications, such as broadband Internet, HDTV, etc, requires new last mile access and wireless techniques for connecting private premises to communications backbone network. A promising technique, broadband over power lines (BPL) (see: http://cictr.ee.psu.edu/research/bans/index.html ) uses electric power-lines as a high-speed digital data channel to connect a group of private users to a very high data rate fiber backbone.

Channel characteristics of medium voltage overhead power-line grids, a common type of grid in the United States, were investigated in details by us in: “Transmission Channel Model and Capacity” and “Medium Voltage Overhead Power-Line Broadband Communications”. It is shown that although the overhead power-line grid is a very low-loss medium, it may suffer from very deep fading caused by multipath due to reflections. Mismatch at the branches of the power-line network reflects signals back and creates several signal paths from a transmitter to a receiver. In the same papers, Shannon capacity limits of overhead MV–lines channels have been investigated. It is shown that the overhead power-line grid network has a high-capacity limit compared to other similar wire-line structures such as cable and twisted pairs. See:

BROADBAND ROOM SERVICE BY LIGHT

Encoded light transmissions can provide the wireless devices in a room with multimedia Web

services such as videoconferencing, movies on demand and more

Mohsen Kavehrad, Scientific American Journal, July 2007.

· P. Amirshahi and M. Kavehrad, “Transmission Channel Model and Capacity of Overhead Multi-conductor Medium-Voltage Power-lines for Broadband Communications,” IEEE Consumer Communications & Networking Conference, Las Vegas, Nevada, January 2005. (.PDF)

· P. Amirshahi and M. Kavehrad, “Medium Voltage Overhead Power-line Broadband Communications; Transmission Capacity and Electromagnetic Interference,” Proceedings of ISPLC 2005, Vancouver, Canada, April 2005.

Homes are connected to electric grid by low-voltage lines (LV). Low Voltage lines are distributed to each power plug in every room in a house. More than 99 percent of homes in the United States have access to electricity, whereas connectivity level is far less for cable and phone lines. Thus, a combination of MV and LV power lines can be an appropriate candidate for providing broadband access to every home in the country. The characteristics of LV power lines are very well known, and there are a variety of research activities in this area to exploit different features of LV grids.

Indoor wireless connectivity is always appealing to consumers because of its ease of use. One of the conventional wireless access systems is Wi-Fi. But these systems and similar other wireless schemes suffer from many shortages, including interference, not being able to provide quality of service (QoS), adequate coverage and most importantly, security.

A better alternative for high-speed wireless home networking, delivering voice/video/data (Triple Play) is to use optical wireless, indoors. Use of conventional lasers for optical indoor communications has not been feasible as yet because of the high cost of laser sources. Instead of lasers, LEDs can be used as communications transmitters connected to electric grid, receiving high-bit-rate signals via BPL.

Recently, WHITE LEDs emerged in the market and are considered as future “lamps.” Apparently, in the near future, the low cost, efficient and miniature WHITE LEDs will replace the incandescent and fluorescent lamps. Researchers pledge that by 2012, these devices will reach seven watts and 1000 luminescence. This is brighter than a 60-watt bulb, yet draws a current provided by four D-size batteries. A Japanese research team suggested using the same WHITE LEDs not only for lighting the homes but also as light sources for wireless in-house communications. Using this new and developing technology along with MV-LV–power-lines communications can create a revolution in the area of consumer networking because of its efficiency and affordability. Therefore, in future, you turn on the lights for indoor low-cost lighting and you receive broadband via the same through modulated WHITE LED light.

(a) (b)

(c)

Figure 1: (a) Frequency; (b) Impulse Response (c) capacity of an

MV overhead Power-Line Network


	(a) (b)

(c)

Figure 2: (a) Frequency; (b) Impulse Response (c) Capacity of an LV–Power-Line Network

Figure 3: Visible Light Communications Using White LED

Figure 4: Illustration of Signal Propagation.

The Room Surface is Composed of Three Elements: a, b, and c.

Research News

q Penn-State Research News: Optical Wireless And Broadband Over Power Lines: High Speed, Secure Wi-Fi Alternative

Tuesday, Jan. 10, 2006, at 5 p.m. EST

University Park, Pa. --- Penn State engineers have shown that a white-LED system for lighting and high data-rate indoor wireless communications, coupled with broadband over either medium- or low-voltage power line grids (BPL), can offer transmission capacities that exceed DSL or cable and are more secure than RF.

q Eurek-Alert: Optical Wireless……..

q Technology News Daily: Optical Wireless………..

q Science Daily: Optical Wireless And Broadband Over Power………

q CNN_Magazine _Com: Wi-Fi alternative

q Innovations-report: Optical wireless………….

q Physic-Org: Optical wireless and broadband over power lines………….

· M. Kavehrad, P. Amirshahi, “Hybrid MV-LV Power Lines and White Light Emitting Diodes for Triple-Play Broadband Access Communications,” IEC comprehensive report on; Achieving the Triple Play: Technologies and Business Models for Success, ISBN: 978-1-931695-37-4, January 2006. (.PDF)

· P. Amirshahi and M. Kavehrad, “Broadband Access over Medium and Low Voltage Powerlines and use of White Light Emitting Diodes for Indoor Communications,” IEEE Consumer Communications & Networking Conference, Las Vegas, Nevada, January 2006. (.PDF)

· Y. Alqudah and M. Kavehrad, “MIMO characterization of indoor wireless optical link using a diffuse-transmission configuration,” IEEE Transactions on Communications, Vol. 59, No. 9, September 2003, 1554–60.

· Dominic C O’Brien and Marcos Katz, “Short-Range Optical Wireless Communications,” Wireless World Research Forum. (.PDF)

In this research, we investigate the capabilities of each of these techniques for providing broadband communications.

Acknowledgments

This research is supported by the CICTR of The Pennsylvania State University.

Indoors Broadband Wireless Optical Local Area Networks

“Huge Bandwidth & Huge Bandwidth Reuse”

It is commonly agreed that the next generation of wireless communication systems, usually referred to as 4G systems, will not be based on a single access technique but it will encompass a number of different complementary access technologies. The ultimate goal is to provide ubiquitous connectivity, integrating seamlessly operations in most common scenarios, ranging from fixed and low-mobility indoor environments in one extreme to high-mobility cellular systems in the other extreme. Surprisingly, perhaps the largest installed base of short-range wireless communications links are optical, rather than RF, however. Indeed, ‘point and shoot’ links corresponding to the Infra-Red Data Association (IRDA) standard are installed in 100 million devices a year, mainly digital cameras and telephones. It is argued that optical wireless communications (OW) has a part to play in the wider 4G vision.

In large open environments where individual users require 100 Mbps or more, optical wireless is a more sensible solution because of its limited cell size. Today's Radio Frequency (RF) LANs realistically cannot support more than one or perhaps two high capacity users per cell. With cell sizes of ~100 meters which could accommodate ten's of users, this is highly wasteful. Multiple high capacity users could only be serviced by deploying a similar number of systems, all within the same locale. This would create a situation where the multiple cells almost completely overlap, which then raises concerns with regards to interference, carrier re-use, etc. In contrast, optical wireless could deliver the necessary capacity to each user through multiple user-sized cells, and because of the intrinsically abrupt boundary of these cells, interference would be negligible and carrier re-use would not be an issue. Indeed, optical wireless is a future proofed solution since additional capacity far beyond the capabilities of radio could be delivered to users as their needs increase with time.

Related Papers:

We have been examining the potential of infrared (IR) for transmission of information packets in broadband indoor multimedia wireless communications. The current focus is on the feasibility study of broadband indoor infrared wireless systems for very high-speed transmissions, as in broadband wireless local multimedia access.

We originated and designed concepts for a Multi-Input-Multi-Output (MIMO) wireless optical architecture referred to as Multi-Spot Diffuse (MSD) configuration with Multi-element optical transmitters and multi-branch optical receivers, proposed in:

Ø G. Yun, M. Kavehrad, “Spot Diffusing and Fly-Eye Receivers for Indoor Infrared Wireless Communications," Proceedings of IEEE Wireless Communications Conference, Vancouver, June 1992.

Ø G. Yun, M. Kavehrad, " Indoor Infrared Wireless Communications Using Spot Diffusing and Fly-Eye Receivers," The Canadian Jour. on Elect & Comp. Eng., Vol. 18, No. 4, October 1993.

In these articles, the following factors were taken into account:

1. Implementation of multi-branch angle diversity using non-imaging elements requires a separate optical concentrator for each receiving element, which may be excessively bulk and costly. We proposed the fly-eye receiver, which consists of a single imaging optical concentrator (e.g., a lens) that forms an image of the received light on a collection of photo-detectors, thereby separating signals that arrive from different directions. This new design is referred to as an imaging angle-diversity receiver, or simply an imaging receiver. The imaging design has two advantages over a non-imaging angle-diversity receiver. First, all photo-detectors share a common concentrator, reducing size and cost. Second, all the photo-detectors can be laid out in a single planar array, facilitating the use of a large number of receiving elements or pixels.

2. In non-directed, non-LOS links, the conventional diffuse transmitter utilizes a single broad beam aimed at reflecting surfaces within a room, such as the ceiling. We proposed to replace this by the spot-diffusing transmitter, which employs multiple narrow beams pointed in different directions toward these reflecting surfaces. This is referred to as a multi-beam or quasi-diffuse transmitter. While the diffuse transmitter provides considerable immunity against beam blockage near the receiver, it yields a high path loss. The multi-beam (quasi-diffuse) transmitter is expected to reduce path loss compared to the diffuse transmitter, because the narrow beams experience little path loss traveling, from the transmitter to the illuminated reflective surfaces.

Effectively, this is equivalent to using Multi-Element Antennas at both transmit and receive ends (MIMO).

Also, related to implementation of this system are the following publications:

Ø M.R. Pakravan, M. Kavehrad, "Direction Diversity for Indoor Infrared Wireless Communication Receivers," Proceedings of ICC'95, Seattle, WA, June 1995.

Ø M. Kavehrad and G. Yun, United States Patents: Optical taper for increasing the effective area of a photo diode in atmospheric free space communications applications (U.S. 5,192,863), awarded March 1993.

Ø E. Simova, M. Tai, M. Kavehrad, "Indoor Wireless Infrared Link with a Holographic Multiple-Spot Diffuser," Proceedings of ICAPT, Montreal, August 1996.

Ø M.R. Pakravan, E. Simova, M. Kavehrad, "Holographic Diffusers for Indoor Infrared Communication Systems," Journal of Wireless Information Networks, Vol. 4, No. 4, pp. 259-274, October 1997.

Ø S. Jivkova, M. Kavehrad, " Multi-spot Diffusing Configuration for Wireless Infrared Access," IEEE Trans. on Communications, Vol. 48, No. 6, pp. 970-978, June 2000.

Ø S. Jivkova, M. Kavehrad, "Receiver Designs and Channel Characterization for Multispot High Bit Rate Wireless Infrared Communications," IEEE Trans. on Communications, Vol. 49, No. 12, pp. 2145-2153, December 2001.

Ø K. Akhavan, M. Kavehrad and S. Jivkova, “High‑Speed Power‑Efficient Indoor Wireless Infrared Communication Using Code Combining, PART-- I,” IEEE Trans. on Communications, Vol. 50, No. 7, pp. 1098-1109, July 2002.

Ø K. Akhavan, M. Kavehrad and S. Jivkova, “High‑Speed Power‑Efficient Indoor Wireless Infrared Communication Using Code Combining, PART-- II,” IEEE Trans. on Communications, Vol. 50, No. 9, pp. 1495-1502, September 2002.

Ø M. Kavehrad, S. Jivkova, “Indoor Broadband Optical Wireless Communications: Optical Subsystems Designs and Their Impact on the Channel Characteristics,” IEEE Wireless Communications Magazine, Vol. 10, No. 2, pp. 30-35, April 2003.

The pioneering work performed in 1980’s contributed to achieving higher capacities over severely band-limited wireless channels, in the Multi-Input-Multi-Output (MIMO) RF world.

Today, MSD-MIMO utilizing multi-beam transmitter and multi-branch angle diversity detection is one of the most promising ways of achieving very high digital transmission capacities in places as classrooms, hotel lobbies, shopping malls, train stations, etc., where the roaming flexibility for the users is imperative. The multi-beam transmitter while improving the power efficiency significantly, it maintains its robustness to transmitted beam blockage possibility. The multi-branch angle diversity detection further reduces the power requirements due to reduced ambient light reception and multipath-induced distortions. Typically, the receiver optical front-end consists of a concentrator to increase the received optical signal power, and an optical band-pass filter to reject the ambient light. Several types of optical concentrators for the multi-branch angle diversity receivers have been suggested, i.e., ball lens, compound parabolic concentrator and imaging lens. Interference filters have been used to reduce the ambient light reception.

In the recent past, we have designed a novel optical transceiver design in which we exploit unique advantages of holographic optical elements (Patent Pending). Eye-safety limits on the transmit power and the limits imposed by the background noise, e.g., sunlight or in-building lights on the receiver field-of-view (FOV) are the constraints we are considering for the implementation of a practical MSD-MIMO wireless local access IR architecture.

Articles below quote this project:

Penn-State Research News: Low Power, Highly Reliable, Wireless, Infrared LAN
New York Times Article: Beaming Data Holds Promise, With Limits, for Networking
Center Daily Times Article: Professor sees the future in infrared
The Digital Collegian: Researchers look into ways to network computers through infrared light
Electronics Times: Inside job for network system
IEEE Communications Society Industry NewsCache (INC): Scientists are working on high-speed
Science Daily Magazine: Low Power, Highly Reliable, Wireless, Infrared
iG - NY TIMES: As ondas de rádio não conseguirão competir com a luz," afirmou Mohsen Kavehrad
ICON News: Beaming data could be networking's saviour
Wireless News Factor: Does Infrared Have a Chance?
Uni-Science: Indoor Wireless LANs Minus Line-of-Sight IR can work
Penn-State Intercom: Wireless IR LAN
Photonics Spectra: IR Wireless signals High Bandwidth at Low Power
TRN News: Holograms control data beams
INFORMATICA 2.0: Redes conectadas con rayos infrarrojos
EE TIMES, UK: Inside job for low power network system with reduced error rate
Laser Focus World: Free-space optical communications
Burrus Research Associates Inc: Reliable, Broadband, Infrared Communication System
EurekAlert: Low power, highly reliable, wireless, infrared local area networks demonstrated
December 1998 IEEE Communications Magazine: Imaging Diversity Receivers for High-Speed Infrared Wireless Communication
Book: Wireless Optical Communication Systems

Channel modeling by computer simulations as well as experimental measurements and optical transceiver design for actual communications are other aspects that have a major influence on the system architecture design.

Indoor