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CURRENT RESEARCH PROJECTS:

 

OLD RESEARCH PROJECTS:

 

MISCELLANEOUS PROJECTS:

 

 


Project Title: Multiply-Detected Macrodiversity (MDM)

 In the Multiply-Detected Macrodiversity (MDM) scheme, there is no selection, but all the received signals are detected in parallel at a number of base-stations and an algorithm is employed to maximize the probability of correct decision. Our results show that a considerable improvement can be obtained with this scheme, especially when the mobile is located close to the boundary between the cells. As boundary between the cells is exactly the region where the mobile-station is expected to suffer the most degradation in the received signal, the MDM scheme has a considerable potential to be applied in practical cellular systems to improve their performance. Moreover, to implement the scheme, no substantial changes are required in the existing cellular infrastructures. In this project, we investigate the performance of the MDM scheme and compare them with the performance of the traditional macrodiversity schemes based selection. Furthermore, we are studying how the MDM scheme can be practically integrated into today's existing systems. We would like to extend this study to additional systems, such as GSM, for example.

Publications:

 

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Project Title: Ad-Hoc Networks (Reconfigurable Wireless Networks)

Abstract: Reconfigurable Wireless Networks (RWN) are ad-hoc networks whose topology is continuously changing, self-adapting to the connectivity and propagation conditions and to the traffic and user mobility patterns. The main application of the RWN is in situations where a network needs to be rapidly deployed without prior planning and that needs to provide reliable and uninterruptible communication in harsh propagation conditions. Furthermore, the network needs to support high degree of survivability; failure of a single or co-located entities should have, ideally, no effect on the performance of the rest of the network. Possible examples of the use of the RWN are for tactical military communication, for disaster recovery operation, and for ad-hoc commercial installations, such as exhibitions. We have proposed and are currently investigating the performance of a set of protocols for operation of the RWN. These include multi-hop routing protocols in the constantly and continuously changing network configuration and network operational conditions.

Publications:

  • Z.J. Haas and M.R. Pearlman, "The Performance of Query Control Schemes for the Zone Routing Protocol," ACM DialM 1999, Seattle, WA, August 20, 1999

         A. Tsirigos and Z.J. Haas, ``Analysis of Multipath Routing - Part II: Mitigation of the effects of frequently changing network topologies,'' IEEE Transactions on Wireless Communications, vol.3, no.2, March 2004, pp. 500-511 [.pdf]

 

Applications:

Software:

         ZRP Implementation in NS2: README file   Documentation   NS2 Code (tar file)

         ZRP Implementation in Glomosim: Glomosim Code (tar file) by Kaixin Xu (UCLA/CSD)

 

Acknowledgements:

Research under this topic was sponsored in part by the following grants and contracts:

   AFOSR,  MURI contract number F49620-02-1-0233

   NSF, grant number ANI-0329905

   NSF, grant number ANI-0081357

   NSF, grant number ANI-9980521

   ONR, MURI ontract number N00014-00-1-0564

   Air Force Research Labs, contract number F30602-00-C-0032

   Motorola Corporation, research grant

   Nortel Corporation, research grant

Thank you!

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Project Title: Application of Communications and Networking to Biosystems

Abstract: In wireless ad hoc networks, capacity can be traded for delay. This tradeoff has been the subject of a number of studies, mainly concentrating on the two extremes: either minimizing the delay or maximizing the capacity. However, in between these extremes, there are schemes that allow instantiations of various degrees of this tradeoff. Infostations which offer geographically intermittent coverage at high speeds, are one such an example. Indeed, through the use of the Infostation networking paradigm, the capacity of a mobile network can be increased at the expense of delay. We propose to further extend the Infostation concept by integrating it with the ad hoc networking technology. We refer to this networking model as the Shared Wireless Infostation Model (SWIM). SWIM allows additional improvement in the capacity-delay tradeoff through a moderate increase in the storage requirements. To demonstrate how SWIM can be applied to solve a practical problem, we use the example of a biological information acquisition system - radio-tagged whales - as nodes in an ad hoc network. We derive an analytical formula for the distribution of end-to-end delays and calculate the storage requirements. We further extend SWIM by allowing multi-tiered operation; which in our biological information acquisition system could be realized through seabirds acting as mobile data collection nodes.

Publications:

 

 

Acknowledgements: Research under this topic was sponsored in part by: the following grants and contracts:

         NSF,  grant number ANI-0329905

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Project Title: Topology Control

Abstract:

Publications:

         J. Cho and Z.J. Haas, ``Impact of Concurrent Transmissions on Downstream Throughput in Multi-hop Cellular Networks,'' IEEE ICC 2004, Paris, France, June 20-24, 2004

         J. Cho and Z.J. Haas, ``On the Throughput Enhancement of the Downstream Channel in Cellular Radio Networks through Multi-hop Relaying,'' IEEE Journal on Selected Areas in Communications, issue on ``Quality-of-Service Delivery in Variable Topology Networks,'' vol. 22, no. 7, September 2004, pp. 1206-1219


Project Title: 802-related Studies

Abstract:

Publications:

         H-Y. Wei, S. Ganguly, R. Izmailov, and Z.J. Haas, "Interference-Aware IEEE 802.16 WiMax Mesh Networks," 61st IEEE Vehicular Technology Conference (VTC 2005 Spring), Stockholm, Sweden, May 29-June 1, 2005

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Project Title: Mobility Management and Resource Allocation in Wireless Networks

Abstract: In this project, we deal with two central issues in Multimedia Mobile Computing, namely Mobility Management and Connection Admission. More specifically, we ask the questions of how to efficiently locate users within massively accessed internet.

Our approach is based on the idea of ``User Mobility Profile'' (UMP). As a user roams within an internet, the system continuously collects information on the users' mobility and connection patterns. This information is used to anticipate the future location of the active users, thus, reduces the search space and, consequently, the cost of locating the user.

For Additional Information see: http://wnl.ece.cornell.edu/nsf.html

Publications:

  •  Z.J. Haas, J.Y. Halpern, L. Li, and S.B. Wicker, ``A Decision-Theoretic Approach to Resource Allocation in  Wireless Multimedia Networks,'' Fourth International Workshop on Discrete Algorithms and Methods for Mobile Computing, DIALM 2000, Boston, MA, August 11, 2000
  •  R. Prakash, Z.J. Haas, and M.Singhal, ``Load-Balanced Location Management for Cellular Mobile Systems Using Quorum and Dynamic Hashing,'' Wireless Networks 7, 497-512, 2001


Acknowledgements: Research under this topic was sponsored in part by:

  • NSF grant number NCR9704404
  • Nortel Corporation research grant

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Project Title: Multipath Routing

Abstract:

Publications:

         A. Tsirigos and Z.J. Haas, ``Analysis of Multipath Routing - Part I: The Effect on the Packet Delivery Ratio,'' IEEE Transactions on Wireless Communications, vol.3, no.1, January 2004, pp. 138-146 [.ps]

         A. Tsirigos and Z.J. Haas, ``Analysis of Multipath Routing - Part II: Mitigation of the effects of frequently changing network topologies,'' IEEE Transactions on Wireless Communications, vol.3, no.2, March 2004, pp. 500-511 [.pdf]

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Project Title: Heterogeneous Networks

Abstract:

Publications:

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Project Title: MAC layer for Wireless Networks

Abstract: On one hand, the Asynchronous Transfer Mode (ATM) protocol is ubiquitously accepted as a vehicle for multimedia traffic. On the other hand, most of the mobile communication is implemented using a wireless infrastructure. Thus, operation of the ATM protocol across wireless links is of particular interest. One important aspect that needs to be considered is a way to maximize the utilization of the available bandwidth through the design of a Medium Access Control (MAC) scheme. MAC protocols, in general, and MAC protocols for wireless systems, in particular, have been extensively studied in the past. However, most of the previously investigated MAC protocols are designed for single-medium communications and turn out to be inadequate for transmission of intergrated, multiple-media traffic. Even though some claim that their existing MAC schemes support multimedia traffic, these schemes, in fact, were not designed with multimedia traffic characteristics in mind and, thus, only partially serve the goals of multimedia communications. Design of a new MAC scheme that will efficiently support an arbitrary mix of different and differing traffic types is the subject of this study. In particular, our proposed scheme takes advantage of the bursty nature of the multimedia traffic, as to guarantee the required Quality of Service.

Publications:

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Project Title: Asymmetric Protocols

Abstract: In this project, we advocate the use and propose the design of an asymmetric transport-layer protocol for mobile systems. Due to the ever increasing device integration density, physical dimensions of portable systems and devices continue to diminish rapidly. However, the computing power of the portable equipment does not increase at the same rate. Thus, to maintain a constant level of performance of mobile applications, there is the need to reduce the processing load of computing algorithms and communication protocols for mobile devices. One approach to offload processing of communication protocol from a mobile device without sacrificing the performance and features is through the use of asymmetric design. In an asymmetrically designed protocol, peer functions are implemented through algorithms and procedures that are of substantially different complexity, with the lower complexity procedures used on the mobile device. We propose to devise and implement an example of such a communication protocol that provides the TCP functionality, yet places a significantly lower load on the mobile machine.

Publications:

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Project Title: Novel Channel-Assignment Algorithms

Abstract: This project addresses the issue of improvement in the wireless resource utilization; i.e., how to maximally pack the users' transmissions into a preallocated amount of wireless bandwidth. In particular, it concentrates on the question of how to maximally increase the geographical reuse of channels in a cellular FDM/TDM system, such as GSM, for example.

A centralized algorithm is proposed, the Centralized-Maximally Packed Channel Assignment (C-MPCA), in which the measured information from mobiles and from base-stations is periodically conveyed to a central point in the network, where an optimal channel allocation is globally computed. The computation of the channel allocation relies on call-related parameters, such as the requested quality of service (e.g., probability of blocking and probability of dropping). In other words, the channel allocation algorithm is capable of controlling the relative quality of service (e.g., priority) of all the calls in the system in a global manner. In particular, it can assure that high-priority calls are neBecause of the centralized execution, instability of the assignments is avoided and significantly better performance (i.e., larger reuse) can be achieved, compared with distributed algorithms. A preliminary study of the proposed scheme indicates that the number of required channels to satisfy some user population with some quality of service can be reduced by half, if the maximum packing scheme is implemented. Further investigation suggests that the improvement can be even more profound for future microcellular wireless networks.

Publications:

  • Zygmunt J. Haas, Jack H. Winters, and David S. Johnson, "Simulation Results of teh Capacity of Cellular Systems,"IEEE Transactions on Vehicular Technology, vol.46, no.4, November 1997

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Publications:

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Project Title: Reliability and Security of Wireless Systems

Abstract: This work studies the database failure recovery procedure for cellular phone networks as part of the Electronic Industries Association/Telecommunications Industry Association Interim Standard 41 (EIA/TIA IS-41). Before the location information of the database is recovered, phone calls may be lost. The restoration process can be sped up by having the mobile phones to periodically confirm their existence by radio contact with the cellular network. We show that, under some cost assumptions, periodic update interval should be chosen to be approximately equal to the call interarrival time, with more frequent updates for more unreliable system. We also show that the cost of an optimized system is relatively small and stable, if the system is even moderately reliable. Finally, if the system is at least moderately reliable, the effects of call origination rate and the rate at which Location Areas are crossed, are rather small, assuming that the periodic update interval was chosen as stated above. Thus in such cases, optimization of the size of the Location Area can be made independent of the optimization of the periodic update process.

Publications:


Miscellaneous Publications:

  • Mark J. Karol, Zygmunt J. Haas, Clark B. Woodworth, and Richard D. Gitlin, "Time-Frequency-Code Slicing: Efficiently Allocating the Communications Spectrum to Multirate Users," IEEE Transactions on Vehicular Technology, vol.46, no.4, November 1997
  • Zygmunt J. Haas, "Location-Independent Access in Mobile Systems," Kluver Academic Publishers, Wireless Personal Communications 4: 163-184, 1997
  • Zygmunt J. Haas and Sanjoy Paul, "Limited-lifetime Shared-access in Mobile Systems," Wireless Networks 1 (1995) 139-146
  • Gregory Pollini and Zygmunt J. Haas, "E-BAMA vs. RAMA," IEEE Network, pp.18-25, March/April 1994

 


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Last updated by Zygmunt J. Haas on April 19, 2005

This page is maintained by Zygmunt J. Haas, haas(at)ece(dot)cornell(dot)edu

Copyright by Zygmunt J. Haas, 2005