Multitier Wireless Networks

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Multitier Wireless Networks And Other Research
Areas
Shalinee Kishore Assistant Professor Dept. of
Electrical Computer Engineering www.eecs.lehigh.
edu/skishore Research Assistants Zhenlei
Shen, Yan Li, Norashikin Yahya
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Background
Multitier Wireless Networks contain radios whose
coverage areas vary in their order of magnitude.
Cellular Systems
Battlefield Communications
Fixed Wireless Networks
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Background (Contd)

• Higher tier radios have larger coverage area
  and extend the
• reach of the network.
• Lower tier radios used to enhance local
  performance (e.g.,
• support higher number of users or deliver
  higher data rates).
• Result multitier networks can simultaneously
  support
• ubiquity and capacity, two
  fundamental (and often
• contradictory) goals of wireless
  communication networks.

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Motivation for Research

• In the past, multitier systems have been studied
  primarily in the
• cellular context and assuming little or no
  spectral reuse across
• tiers.
• Types of services required from wireless
  networks are becoming
• increasingly varied ? critical and timely to
  develop a unified
• framework for multitier systems.
• Framework must include varying degrees of
  spectral reuse and
• address not only cellular but more ad hoc
  network configurations.

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Research Goal

• Goal perform a novel and expansive study of
  spectrally efficient
• multitier architectures.
• Presently, we are studying centralized systems,
  where user
• terminals communicate strictly to multitier
  access points.
• We will also consider non-centralized
  architectures where control
• is distributed among network nodes (ad hoc
  connections possible).

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Key Challenge Cross-Tier Interference

• High degree of spectral reuse implies cross-tier
  interference.
• Cross-tier interference due to transmissions
  made by higher
• tier radios may complicate reliable
  communications at lower
• tier radios.

Signal
Cross-Tier Interference

• Research studies signal processing methods,
  radio resource
• allocation schemes, and access control
  techniques which jointly
• suppress this interference to deliver desired
  ubiquity and capacity.

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Some Specific Areas of Research

• User Capacity and Coverage Area in Multitier
  Cellular CDMA Networks
• Multitier Networks for Data Hotspots
• Multitier (Hierarchical) Ad Hoc Networks

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Reachback in Sensor Networks A Multitier Ad Hoc
Example
Higher-Tier Access Point
Antenna
Sensor
Cluster
Forwarding Node
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Some References
1 S. Kishore, et al., Capacity in a CDMA
Macrocell with a Hotspot Microcell Exact and
Approximate Analyses , IEEE Trans. on Wireless
Comm., March 2003. 2 S. Kishore, et al.,
Uplink User Capacity of a Multi-Cell CDMA System
with Hotspot Microcells , Proc. of Vehicular
Technology Conference S-02, May 2002. 3 S.
Kishore, et al., User Capacity in a CDMA
Macrocell with a Hotspot Microcell Effects of
Transmit Power Constraints and Channel Dispersion
, Proc. of IEEE Globecom, December 2003. 4
S. Kishore, et al., Downlink User Capacity in a
CDMA Macrocell with a Hotspot Microcell , Proc.
of IEEE Globecom, December 2003.
5 S. Kishore, et. al., Uplink Throughput in a
Single-Macrocell/Single-Microcell CDMA System,
with Application to Data Access Points , Proc.
of Vehicular Technology Conference F-03, October
2003.
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Collaboration with Susquehanna County, PA

• Multitier networks can be particularly
  beneficial in serving
• varied communication needs of remote,
  under-served regions.
• To demonstrate this, we will assist Susquehanna
  County, a
• rural and technology-poor community in
  Northern PA to
• meet its communication requirements.
• Specifically, its topographic and demographic
  data will be
• used as a testbed to implement our conclusions
  and devise a
• cohesive multitier system for the region.

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Collaboration with Susquehanna County, PA (Contd)

• The design will take into consideration
• extremely hilly propagation characteristics of
  the area
• locations of population centers (businesses,
  schools, libraries,,
• major roads, medical facilities, government
  buildings, etc.),
• communication requirements at these locations.
• Result will be a plan the county could use to
  attract service
• providers to the area.
• Collaboration is part of Lehigh University
  Communication
• Internship and Development (LUCID) Program.

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More on LUCID

• LUCID will also support internships for high
  school students
• and teachers from Susquehanna County to spend a
  summer at
• Lehigh learning basic principles of
  communication systems,
• Internetworking, wireless communications, etc.
• Skills learned may be used by participants to
  improve
• communication infrastructure in Susquehanna
  County (for
• example, installing wireless local area
  networks at local
• schools, businesses, etc.).

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Other Research Activities

• Quantifying diversity in wireless communication
  systems
• Using diversity models to improve channel
  estimation,
• adaptive radio resource allocation, etc.

General Research Interests

• Wireless Networking Theory
• Cross-Layer Design
• Interference Modeling