• Alexander Lackpour, M. Kavehrad and Scott Thompson, “Architecture and Predicted Performance of an IEEE 802.11b-like WMAN Transceiver at 5.8GHz,” Proceedings of the Third IEEE Workshop on Wireless Local Area Networks, Boston-Mass., September 2001. PRESENTATION

o    Opportunistic Communications – Adaptive-Rate Techniques, Dynamic Network Resource Management.

o    Multi-Input-Multi-Output (MIMO) Systems; (see, e.g.,  Broadband Wireless Local Area Networks )

o    Cellular Network Systems; Dynamic TDD:

o    Quality-of-Service (QoS) Metrics.

o    RF Propagation Modeling and Channel Characterizations.

_______________________________________

Broadband Transmission over Power Lines

 

A Solution to Global Digital Divide:

The medium-voltage (MV) power grid, typically carrying Megawatts of power at 11,000 V, reaches within a few hundred meters of most inhabited places on earth. The same grid is an excellent communications medium, offering bandwidths well beyond 100MHz and potentially more, with Shannon capacity values well into the Gigabit range. The high bandwidth and the ubiquitous nature of the MV grid make it a communication engineer’s gold mine, whose potential has hardly been exploited.

 

The power distribution grid resembles an omnipresent, widely branched hierarchical structure. The structure of the medium (MV) and low-voltage (LV) distribution grid (including outdoor supply cables) is appropriate for Internet access, offering both last mile and last meter solutions. Power-line communication (PLC) can be implemented along with wireless technology. This feature is most attractive and critical for use in rural areas, where services from telephone companies or cable companies do not reach, and where radio coverage is poor or very expensive through one-way satellite access, PLC may turn out to be an attractive solution.

 

Many service providers are interested in introducing the next generation broadband access to residential homes and small home offices (SOHOs) via power-line distribution network architecture, termed Broadband over Power-Line (BoPL) transmission network, in the not too distant future. A typical scenario for such an access network is shown in Figure-1. In search of a proper end-to-end feasibility test of the anticipated physical-layer design, we are conducting investigations on a system level model. The work presents conceptual designs, analyses, computer simulations and some experiments on a BoPL transmission configuration to assess the potential interference problems.

 

Fig.-1 Power-Line Broadband Access Network Architecture

Despite the enormous potential, there is some skepticism about the technology and its commercial viability. This is due to several technical problems and regulatory issues that as yet remain to be resolved.  Some of these issues are listed below:

 

·         Power line channel is harsh due to discontinuities (impedance mismatch), ground effects, interference and noise, thus difficult to model.

·         Regulatory issues naturally arise due to unshielded nature of overhead power lines, which are both the source and target of electromagnetic interference.

·         Since communication over power networks is basically wire-borne, suitable measures have to be developed to prevent inadmissibly high signal radiations, i.e., interference to and from other services needs to be remedied.

 

In a relatively complex grid of nodes and lines, discontinuities caused by Impedance Mismatch between a node (e.g. a transformer) and a wire line connected to the node, create reflections. These reflections give rise to a frequency selective multi-path. There is also possibility of resonance effect, due to standing wave formation, on transfer (magnitude and phase versus frequency) responses of an end-to-end line between points A and B on the overhead MV power line grid, as shown in example below [1].

                        

The impairments of Power-line Systems are similar to those of Mobile Radio Systems. Both operate over a metropolitan area, can suffer with multi-path fading and are affected by unpredictable man-made or natural noises. The power-line grid differs considerable in topology, structure, and physical properties compared to other wire-line systems such as twisted-pair, coaxial, fiber-optic cables.

We need to remember that overhead MV power-lines are exposed. The use of electric power network to carry RF waves is not unconstrained, because by occupying a frequency band of about 500 KHz to nearly 100 MHz, a frequency overlap is created with some existing practices such as; the entire HF band services, long, medium, and short-wave radios and amateur radio bands, as air-borne power lines also act as antennas, transmitting and receiving interference to and from the surrounding environments.

On April 27, 2004 NTIA released a Phase-I study that examined the potential interference to federal government radio systems that could result from the deployment of BoPL, and identified appropriate techniques that if applied, could potentially mitigate the interference. Some examples of these techniques are:

·        Power control

·         Avoidance of locally used frequencies

·         Differential-mode signal injection

·         Filters and signal terminations to alleviate impedance mismatch discontinuities

    In June 2004, the White House called for the establishment of technical standards to make possible new broadband technologies such as the use of high-speed communications directly over power lines.

Meanwhile, in order for this technology to be viable, some problems have to be solved, such as finding a suitable model for the power line channel that incorporates signal degradation through the line and by interference and noise sources, determining appropriate frequency allocation schemes and acceptable transmission power levels to minimize interference into existing services, and finally; selecting suitable transmission schemes and countermeasures to effectively minimize the external interference effects on the proposed system. It is important to remember that in USA, all the above have to keep the systems adherent to the Federal Communications Commission (FCC) regulations with regards to maximum allowable generated interference on neighborhood systems.

·         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, “High-Frequency Characteristics of Overhead Multi-conductor Power Lines for Broadband Communications,” IEEE Journal on Selected Areas in Communications, Vol. 24, No. 7, July 2006.

·         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.

·         Paul S. Henry, “Interference Characteristics of Broadband Power Line Communication Systems Using Aerial Medium Voltage Wires,” IEEE Communications Magazine, pp. 92-98, April 2005.

·         P. Amirshahi and M. Kavehrad, “System Design Considerations for High data Rate Communications Over Multi-wire Overhead Power-lines,” The VI IEEE International Workshop on Signal Processing Advances in Wireless Communications, New York, June 2005.

·         P. Amirshahi, S.M. Navidpour and M. Kavehrad, “'Fountain Codes for Impulsive Noise Correction in Low-Voltage Indoor Power-line Broadband Communications,” IEEE Consumer Communications & Networking Conference, Las Vegas, Nevada, January 2006.

·         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.

·         Amy K. Glasmeier, Chris Benner, and Chandrani Ohdedar, “BEYOND THE DIGITAL DIVIDE: Broadband Internet Use and Rural Development in Pennsylvania,” Final Report to the Center for Rural Pennsylvania, June 2007.

                            See also:

 

·         Scientific American: Broadband to the people

·         NetworkWorld: A two-pin plug and you have broadband

·         The Energy Daily: Repeaters are Key

·         Palo Alto Daily News July 15, 2004: ATT Labs Demo in Menlo Park, CA.

·         Electronic Clipping: Alliance opts for interoperable powerline broadband specs

  

TV Interview:

            WPSX-TV Pennsylvania... Inside Out, an interview with lead producer David Price:

           Click on the line below to see and hear the interview:

High-voltage electrical power lines could be used for communications

 

 

ACKNOWLEDGEMENTS

 

This research is supported by the AT&T Shannon Labs through a grant and by the CICTR of The Pennsylvania State University.

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Hybrid Wireless Access Systems

The allocated bandwidth for RF FWA is adequate for both point-to-point high capacity trunk lines and point-to-multipoint shared bandwidth last miles connections. Furthermore, if broadband Wireless Optical links or Hybrid Optical & RF Combined Wireless Links are used, there is a huge and as yet unregulated optical spectrum available which is secure and easily reusable, due to availability of focused optical beams. Atmospheric-optical-wireless links are excellent means for extending the fiber reach into rural areas.

Radio Frequency (RF) communications are generally reliable and well understood but cannot support emerging data rate needs unless they use a large portion of the precious radio spectrum. Free Space Optical (FSO) communications [1] offer enormous data rates but operate much more at the mercy of the environment. The perennial limitations of FSO communications are manifested in the channel attributes of scintillation (optical turbulence) and path obscurations. Both phenomena reduce the availability of the optical channel to support reliable communications. Since RF paths are relatively immune to the same phenomenology, combining the attributes of a high data rate but burst link (FSO) with the attributes of a low data rate (by comparison) but reliable link (RF) could yield attributes better than either one alone: high availability with high data rates.

This is one of our active areas of research.

{1] Lasers that transmit data at over 1 gigabyte per second may be coming to your neighborhood, The FEATURE Journal, November 22, 2001.

ACKNOWLEDGEMENTS

This project is a collaborative research between the AT&T Shannon Labs and the CICTR of The Pennsylvania State University.

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10GBASE-T Transmission over Standard Category-5 or 6 Copper Cable

With the increasing popularity of multimedia services supplied over a fixed network, services such as: web browsing, video conferencing and video-on-demand, it is only a matter of time before users will demand higher bandwidth LAN access. Advances in signal processing and fast CMOS processing power have also made it possible for users to afford high-resolution visual services. IEEE is interested in specifying the next generation 10 Gbps twisted pair Ethernet network (10GBASE-T) in the not too distant future. The research focus here is on conceptual designs and demonstration of a 10GBASE-T copper transmission system for distribution of a digital signal over ~100 meters of a standard CAT-5 or 6 copper cable. It is believed to be possible to achieve this, using standard copper cable if we adopt vectored transmission on 4 pairs in presence of cross-talk and noise. The 10 Gigabit per second speed is about 1/2 the theoretical capacity on these cables at 100 meters. This physical layer design can be adopted in future 10 Gbps Ethernet LANs where fast connection to server farms on campus settings is a potential application of such access networks.

Our presentation to the IEEE 802.3 Standards Committee, the 10GBASE-T Study Group can be downloaded from the 10GBASE-T Study Group Meeting site at: http://www.ieee802.org/3/10GBT/public/nov03/index.html

Ø  Nexans White Paper: Nexans efforts on 10Gbe over UTP

Ø  Nexans White Paper: Dynamic Performance: Assessing Cabling Claims for 10GBASE-T, Nexans, May 2004.

 

Ø  Penn-State Research News: Copper wire shown to be competitive with fiber optic cable for LANS

Ø  Eurek-Alert: Copper wire ……………..

Ø  HimTimes: Copper Wire……………

Ø  Continuity Central: Copper wire broadband LANS shown to have advantages over fibre optic cable

Ø  Today's focus: Cat-6 may go farther…………..

Ø  Wire and Cable International Overview (page-3): Copper seen as competition for FO cable

Ø  Monitor: Copper wire competitive………….

Ø  The WAI Connection: Can copper wire match……….

Ø  Speed guide:  Copper wire………………

Ø  UOL Inovacao: Cobre pode substituir fibra óptica na transmissão de dados

Ø  CTFQ – O Potal Oficial da……………

Ø  Business Week: Developments to watch

 

ACKNOWLEDGEMENTS

This research is supported by the Pittsburgh Digital Greenhouse through a grant from the commonwealth of PA, Department of Community and Economic Development, International Copper Association (ICA), Nexans, CISCO and CICTR of the Pennsylvania State University.

Fixed Wireless Access Systems; Multimedia-Teleconferencing

Robust and Error-Resilient Multimedia Video-Teleconferencing over UNII-Band

Fixed Wireless Channels

I.                   Starting with H.263+ and H.323 standards for packet-video compression encoding / decoding, appropriate measures are being added to make the compression algorithms more error- resilient on Fixed Wireless Fading Channels.

II.                In applications involving image, video and other mixed media transmissions, the channel as seen by the higher layers is not the same old natural continuous-time physical channel. It is a modified channel due to the error correction mechanisms used on the physical layer. Thus, the uncorrected errors affect the design of video encoding algorithms. 

A UNII-Band 5.8 GHz, frequency hopping digital radio, using an adaptive signal constellation, on a metropolitan-area nearly Line-of-Sight (LOS) radio link provides a wireless test-bed for Quality-of-Service (QoS) measurements. We are performing on-going status monitoring of a nearly point-to-point radio link on the University Park campus of The Penn-State University. This status monitoring includes monitoring link throughput, outage, dropped packets, - - - etc, on the established radio link. This is required over variations of weather, seasons, etc. We are developing and implementing a means of measuring and logging link performance at TBD time intervals on this UNII-band radio link. A major goal here is to identify the validity conditions for fading assumptions on this link.

Selected Papers

• J. Yun, W. Jeong, M. Kavehrad, “Throughput Analysis of Selective Repeat ARQ Combined with Adaptive Modulation for Fading Channels,” Proceedings of the MILCOM’02, Anaheim, CA, October 2002.
• K. Muhonen and M. Kavehrad, “Amplifier Linearization with Memory for Broadband Wireless Applications,” Proceedings of the Thirty-Fifth Asilomar Conference on Signals, Systems and Computers, Pacific Grove, CA., November 2001.
• W.-C. Jeong and M. Kavehrad, “Dynamic-TDD and optimum Slot-Allocation in Fixed Cellular Systems,” Proceedings of the IEEE Vehicular Technology Conference, Atlantic City, October 2001.
• Ravindran, H. Liu, I. Agoren, A. Lackpour, D. Miller, M. Kavehrad, J. Doherty, “Mobile Multimedia Services for Third Generation Communications Systems,” Proceedings of the IEEE Vehicular Technology Conference, Atlantic City, October 2001.
• J. Li, M. Kavehrad, “Multi-Carrier Orthogonal-CDMA for Broadband Fixed Wireless Applications,” Proceedings of the IEEE Vehicular Technology Conference, Atlantic City, October 2001.
• Alexander Lackpour, M. Kavehrad and Scott Thompson, “Architecture and Predicted Performance of an IEEE 802.11b-like WMAN Transceiver at 5.8GHz,” Proceedings of the Third IEEE Workshop on Wireless Local Area Networks, Boston-Mass., September 2001. PRESENTATION .
• M. Kavehrad, "Next Generation Wireless Communications Systems," Plenary Speaker, MWSCAS'2000, Lansing, Michigan, August 2000.
• J. Li, S. Farahvash, M. Kavehrad, R. Valenzuela "Dynamic TDD and Fixed Cellular Networks," IEEE Communications Letters, Vol. 4, No. 7, July 2000. 
• S. Farahvash, M. Kavehrad, J. Li, S. D. Thompson," Using Collision Avoidance Frequency Hopping Technique in a Fixed Wireless Network with Star Topology," Proceedings of the IEEE WCNC'2000, Chicago, September 2000.
• K.J. Muhonen, M. Kavehrad, R. Krishnamoorty, "Look-Up Table Techniques for Adaptive Digital Pre-distortion, a Development and Comparison, "IEEE Trans. on Vehicular Tech., Vol. 49, No. 5, September 2000.
• S. Farahvash, M. Kavehrad, "A Statistical Channel Model for Wave Propagation in Millimeter-Waves Range; LMDS Application," Proceedings of PIMRC'99, Osaka, Japan, September 1999.
• K. Akhavan, S. Farahvash, M. Kavehrad, N. Mehravari " QoS Provisioning for Wireless ATM by Variable-Rate Coding," Proceedings of WCNC'99, New Orleans, USA, September 1999.
• J. Li, K. Muhonen, M. Kavehrad, "Digital Pre-distortion Linearizer for Multi-Carrier Spread Spectrum," Proceedings of RAWCON'99, Denver, Colorado, August 1999.
• J. Li, M. Kavehrad, "A Multiple Access Scheme for LMDS, based on OFDM, O-CDMA and Sectored Antennas," Proceedings of ICC'99, Vancouver, CANADA, June 1999: PRESENTATION
• Kathleen Muhonen, M. Kavehrad, "Amplifier linearization for the Local Multipoint Distribution Services Application," Proceedings of PIMRC'98, Boston, September 1998: PRESENTATION.
• John J. Metzner, Reliable Data Communications, Academic Press, 1998.
• H. Ohtsuka, O. Kagami, S. Komaki, K. Kohiyama, M. Kavehrad, "256-QAM Sub-carrier Transmission Using Coding and Optical Intensity Modulation in Distribution Networks," IEEE/LEOS Photonics Technology Letters, April 1991.
• M. Kavehrad, E. Savov, "Fiber-Optic Transmission of Microwave 64-QAM Signals," IEEE Journal on Selected Areas in Communications, Vol. 8, No. 7, Sept. 1990, pp. 1320-1326 and ICC Proceedings, Atlanta, April 1990.
• I.M. Habbab, M. Kavehrad and C-E. Sundberg, " ALOHA with Capture Over Slow and Fast Fading Radio Channels with Coding and Diversity," IEEE Journal on Selected Areas in Communications, Vol. 7, No. 1, pp. 79-88, January 1989.
• M. Kavehrad, “A Countermeasure to Improve Outage Performance of Interference-Limited Microwave Radio Links,” Canadian Journal of Electrical & Computer Engineering, Vol. 16, No. 1, January 1991.
•  M. Kavehrad, "A Hybrid Radio Model and its Performance in RF Interference Environments," Technical Memorandum, AT&T Bell Laboratories, April 1988.
• M. Kavehrad, "Design and Performance Considerations for the Hybrid Atmospheric Optical/Digital Microwave Network Systems," Technical Memorandum, AT&T Bell Laboratories, December 1987.
• M. Kavehrad, G.E. Bodeep, "Design and Experimental Results for a Direct-Sequence Spread-Spectrum Radio using Differential Phase Shift Keying Modulation for Indoor, Wireless Communications," IEEE Journal on Selected Areas in Communications, pp. 815-823, June 1987.
• M. Kavehrad, P.J. McLane and C-E. Sundberg, "On the Performance of Combined QAM and Convolutional Codes for Cross-Coupled Multidimensional Channels," IEEE Trans. on Communications, pp. 1190-1201, December 1986.
• M. Kavehrad, J. Salz,"Cross-Polarization Cancellation and Equalization in Digital Transmission Over Dually-Polarized Multipath Fading Channels," AT&T Technical Journal, Vol. 64, No. 10, December 1985.
• M. Kavehrad, P.J. McLane, "Performance of Low-Complexity Channel-Coding and Diversity for Spread-Spectrum in Indoor, Wireless Communication," AT&T Technical Journal, Vol. 64, No. 8, pp. 1927-1966, October 1985.

 

ACKNOWLEDGEMENTS

This research has been supported by the National Science Foundation (NSF) Grant Number CCR-9902846, The Ben Franklin Partnership Program of Pennsylvania Pittsburgh Digital Greenhouse, Lockheed Martin Philanthropy and Lucent Technologies.

 

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Optical Frequency-Encoded CDMA Switch --- Amplitude Encoding 

Of Broadband Sources (Space-Time Coding)

Selected Papers

• D. Zaccarin, M. Kavehrad, "An Optical CDMA System Based on Spectral Encoding of LED," IEEE/LEOS Photonics Tech. Lett. Journal, Vol. 5, No. 6, April 1993.
• M. Kavehrad, D. Zaccarin, "Optical Code-Division-Multiplexed Systems Based on Spectral Encoding of Non-coherent Sources," Jour. of Lightwave Tech., Vol. 13, No. 3, March 1995.
• M. Kavehrad, E. Simova, "Optical CDMA by Amplitude Spectral Encoding of Spectrally-Sliced Light-Emitting-Diodes," Proceedings of IEEE ISSSTA, Mainz-Germany, September 1996: PRESENTATION
• P.C. Neusy, M. Kavehrad, "Proposal for an All-Optical Code-Division Multiple Access for Local Area Networks," Electronics Letters Journal, Vol. 26, No. 18, 30th August 1990, pp. 1471-1473.
• D. Zaccarin, M. Kavehrad, "Optical CDMA with New Coding Strategies and New Architectures to achieve Bipolar Capacity with Unipolar Codes," OFC'94 Technical Digest, Vol. 4, San Jose, Feb. 1994.

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