83169909 Cognitive Radio1

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Transcript of 83169909 Cognitive Radio1

  • Cognitive Radio: NextGeneration Communication System


  • Evolution of Communication Systems

  • Software Defined RadioSoftware Defined Radio as a basic platform on which to build a Cognitive Radio

    Cognitive Radio can provide the spectral awareness technology to support FCC initiatives in Spectral Use

  • Definition of SDRSoftware defined radios -evolutionary process from purely hardware-based equipment to fully software-based equipment. 1. Hardware driven radios- Transmit frequencies, modulation type and other radio frequency (RF) parameters are determined by hardware and cannot be changed without hardware changes. 2. Digital radios -A digital radio performs part of the signal processing or transmission digitally, but is not programmable in the field3. Software Defined Radios- All functions, modes and applications can be configured and reconfigured by softwareSDR Forum--waveform properties, cryptography and applications, is re-programmable, and may be upgraded in the field with new capabilities-Importance of Standards (APIs)

    *Notice of Proposed Rule Making (NPRM) 8/12/00

  • Cognitive Radio

  • Spectrum Allocation

  • COGNITIVE RADIOTwo-way radio

    Automatically changes its transmission or reception parameterscommunicates efficiently, avoiding interference with licensed or licensed exempt users.

    Monitoring of several factors in the external and internal radio environment-radio frequency spectrum, user behaviour and network stateFCC Federal Communication CommissionA software defined radio with a cognitive engine brain".

  • Cognitive Radio Means Smart and AlertIt knows where it is

    It knows what services are available, for example, it can identify then use empty spectrum to communicate more efficiently It knows what services interest the user, and knows how to find them

    It knows the current degree of needs and future likelihood of needs of its user

    Learns and recognizes usage patterns from the user

    Applies Model Based Reasoning about user needs, local content, environmental context

  • Need for Cognitive RadioRadio spectrum is a scarce resource and is regulated

    Spectrum usage is one of the key issues in communication system challenges

    The spectrum efficiency can be improved with idea of dynamic spectrum allocation.

    Cognitive radio network - on effective spectrum utilization-allocates to primary user or licensed user-user is not utilizing ,secondary user can claim without interfering to primary user

  • What is needed for a CR ?

  • Cognitive Radio Evolution

  • How Cognitive radio works?Cognitive radio -Spectrum sensing

    -Spectrum management

    -Spectrum mobility

    -Spectrum sharingawareness of changes in its environment response to these changes adapts - operating characteristics - improve its performance or to minimize a loss in performance

  • How Does a Cognitive Radio Get So Smart?Mitola, Cognitive Radio for Flexible Mobile Multimedia Communications, IEEE Mobile Multimedia Conference, 1999, pp3-10

  • Spectrum SensingDynamic spectrum allocation

    Cognitive radio networks

    scans the entire spectral band for the presence/absence of primary users

    Performed either locally - secondary user - collectively by a group


  • Spectrum Sensing Transmitter detection- capability to determine if a signal from a primary transmitter is locally present in a certain spectrum. There are several approaches-Matched filter detection-Energy detection-Cyclostationary feature detectionCooperative detection- information from multiple Cognitive radio users are incorporated for primary user detection.Interference based detectionContd

  • Spectrum ManagementSpectrum Management - capturing the best available spectrum to meet user communication requirements

    Decide on the best spectrum band -Quality of service

    These management functions can be classified spectrum analysis spectrum decision

    Practical implementation of functions - very complex and multifaceted issue in itself.

  • Spectrum Mobility

    Spectrum Mobility- when a user exchanges its frequency of operation

    - use the spectrum in a dynamic manner with the best available frequency band- maintaining seamless communication requirements with better spectrum.

  • Spectrum SharingSpectrum Sharing provides the fair spectrum scheduling methodOne of the major challenges is spectrum sharing.It can be regarded to be similar to generic media access control MAC problems in existing systems

  • The future of CR

    The unlicensed band in range of wireless devices and services FCC - consider opening further bands for unlicensed use. Exploits the inefficiently utilized licensed bands without causing interference to incumbent users Unlicensed radios to operate in the TV broadcast bands and also TV services.

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