Broadband Networks

Internet_1024

Our research in this area is focused on solving broadband networked systems problems, e.g., those associated with hybrid - fiber / twisted-pair / coax / wireless networks evolution. These networks are planned to be transparent on the optical side. A major thrust has been our examination of possible synergy between wired access platforms and wireless technologies.

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Transmitting 40/100Gbps Data Rates over Category 7A Copper Cable

Cross-section of Category 7 cable

A recent collaboration between Nexans and Penn State on a project entitled “40/100 GBASE-T Transmission over Standard Category-7A Copper Cable” resulted in a Best Paper Award at DesignCon 2009.

·         A. Enteshari and M. Kavehrad, “40/100 Gbps Transmission over Copper: Myths and Realities,” Proceedings of DesignCon, Santa Clara, CA. Feb. 2009.

 

The paper was presented in the category “High-Speed and RF Design. 

 

The collaboration also resulted in another paper award in 2009.

·         Ali Enteshari, Jarir M. Fadlullah, and Mohsen Kavehrad, "High-Speed Access over Copper: Rate Optimization and Signal Construction," ETRI Journal, Vol.31, No.5, pp.489-499, Oct. 2009.

 

This paper was selected as the Paper of the Year by the ETRI Journal and received an honorarium award.


The project focused on assessment and design of transmission systems for distribution of digital signals over standard Category-7A copper cables at speeds beyond 10Gbps. The main focus was on the technical feasibility and system design for data rates of 40 and 100Gbps over copper. Based on capacity analysis and rate optimization algorithms, system parameters were obtained and the design implementation trade-offs are examined. The simulation results confirmed that with the aid of Decision-Feedback Equalizer and powerful coding techniques, e.g. TCM or low-density parity-check (LDPC) code, 40Gbps transmission is feasible over 50m of CAT-7A copper cable.

MIMO capacity and R1 rate for 50m cable


The results confirm the technical feasibility of beyond 10Gbps high-speed transmission over standard Category 7A copper wire. The assessment has revealed that CAT-7A cables are, theoretically, capable of delivering data streams at a speed of 40Gbps over 50 meters due to their shielding and design. Also, based on modeling and analysis, the maximum possible rate over 20 meters of cable is well above 100Gbps. However, with various degrees of DSP, the objective of running 100GBASE-T over CAT-7Acable can be achieved with some effort by silicon vendors, probably in the next generations of CMOS technology. We conclude that 40GBASE-T is practical over 50 meters of CAT-7A cable and this is within the realm of expectation of current objectives of IEEE 802.3 standards committee. 

·         Click here to read the paper:  40/100 Gbps Transmission Over Copper: Myths and Realities

·         Penn-State Research News:  Researchers Push Transmission Rate of Copper Cable

·         November 2007 Plenary Week IEEE 802.3 Higher Speed Study Group Meeting, Atlanta, GA. Presentation Title:Towards 100G over 100 Meters of CAT-7”.

News Media :

·         ZD-Net: 100 gigabits per second over copper?

·         Network World: Researchers pushing 100 Gig

·         United Press International: Copper cable transmission rate increased

 

 

ACKNOWLEDGEMENTS

 

This research was supported by the  International Copper Association (ICA) through Nexans Inc and by the CICTR of The Pennsylvania State University.

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Wi-MAX Access Systems

IEEE 802.16e, the standard for Mobile WiMAX, is expected to be published by the end of 2005 and the Mobile WiMAX will be launching its service in South Korea and possibly in North America in late 2006 or early 2007. Originally, the IEEE 802.16 standard was developed for fixed wireless, seeking a new tool for homes and business to link with the worldwide core networks. It was envisioned that 802.16 would offer better solution for the ‘last mile’ connections compared to fiber, cable, or DSL (digital subscriber line) links because wireless systems are less costly to deploy over wide geographic areas. IEEE 802.16d (IEEE 802.16-2004) was published on June 2004 and it assured that WiMAX market and its competitiveness for NLOS (non line-of-sight) wireless broadband access is becoming mature.

 

Since IEEE 802.16e, the mobile version of IEEE 802.16-2004, will be published soon, the focus of 802.16 is expected to be changed from fixed subscribers to mobile subscribers with various form factors; PDA, phone or laptop. The 802.16e standardization group promises to support mobility up to speeds of 40~50mi/h; some vendors already are claiming their success in testing their prototype systems with mobility over 50mi/h speeds for 5Mbps or more data rate. Hence, Mobile WiMAX is expected to not only compete with other ‘last mile’ connections such as fiber, cable, and DSL, but it also threatens WiFi and the CDMA voice communications with VoIP services through Mobile WiMAX.

 

Unlike the wired networks, wireless networks are highly dependent on communications channels; radio channels are dynamic, correlated, unreliable and very expensive. This is why the performance will be highly dependent on how well the radio resource management supports QoS requirements even if QoS might be luxurious in early stages of the Mobile WiMAX market. Therefore, several cross layer issues in MAC layer and PHY layer need be resolved optimally on the radio resource management side of Mobile WiMAX systems.

 

In multi-user environments, especially in wireless fading channels, multi-user diversity in radio resource management is one of key elements in maximizing the throughput. Multi-user diversity is a form of selection diversity. Since different users experience independent time-varying fading channels in wireless networks, resources shall be allocated to the user that has the best channel quality in order to maximize the system throughput. Multi-user diversity drew attention since tracking the channel fluctuations of the users is getting more accurate and faster. Hence, the diversity gain increases when dynamic range of the fluctuation increases but, the gain is limited in environments with slow fading. In slow fading, multi-user diversity hardly satisfies all QoS parameters at the same time, especially the fairness among all different users. Ultimately, radio resource management need to implement a combined form of multi-user diversity and fairness scheduler.

The architecture requires development of critical components for the transceiver and systems. This includes providing cost-effective distribution and coverage to subscribers, utilization of low-cost monolithic IC and antenna technology, and implementing effective transceiver linearity, modulation and coding and MAC-layer techniques. Recently, availability of low-cost powerful processors and development of good channel estimation techniques have rejuvenated an interest in adaptive rate techniques both in industry and academia. This new way of thinking is termed “Opportunistic Communications” whereby dynamic rate and power allocation may be performed over the dimensions of time, frequency and space in a wireless system. In a fading (scattering) environment, channel can be reliable locally in time and space, and opportunistic schemes can choose to transmit in only those channel states. Obviously, some channel state information is required for an opportunistic communication approach to be successful. Otherwise, it becomes like shooting in the dark. This is in a way similar to building a financial investment portfolio of stocks, based on some “insider” information. Clearly, it results in more gain compared to traditional methods of building a diversified portfolio of stocks, based on long-term published trends. Same as one would expect a great loss, if the “insider” information turned out to be wrong, consequence of opportunistic communications based on wrong channel states will be a great loss in the wireless network capacity. Thus, in those wireless applications where reliable channel state may easily be obtained, it is possible to achieve enormous capacities.

Related issues are being investigated:

·         BECHTEL Telecommunications Journal:

§  Jungnam Yun, M. Kavehrad, “PHY/MAC Cross-Layer Issues in Mobile WiMax,” Bechtel Telecomm Technical Journal, Vol. 4, No. 1, January 2006.

 

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:

·         Penn-State Research News: New Allocation Technique Boosts Efficiency for Wireless Internet Access

·         The Washington Times: Stories of modern science  ...

·         ASME: Clarifying Wireless High-Speed Internet

·         Innovation Reports: Allocation technique boosts efficiency, minimizes interference for wireless internet broadband

·          

o    Quality-of-Service (QoS) Metrics.

o    RF Propagation Modeling and Channel Characterizations.

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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.

bplpic

 

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

 

 The NTIA Reports are a set of guidelines to service providers on how to conduct their interference measurements. These reports are available online:

 

    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

·         Black Issues in Higher Education: Penn State Engineers Present Expanded View of Broadband by Power Lines

·         Penn-State Research News: Power Line Data Transmission Capacity: Bigger Than DSL Or Cable

·         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

Optical Mesh

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

10GBASE-T

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

lmds2

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.                 

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.

imageKRB

LAB-CICTR


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)

cdma-1

cdma-2

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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