Cognitive Radio: Next Generation Communication System By V.ALAGU ABINAYA 11MCO02

Evolution of Communication Systems

Software Defined Radio Software 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 SDR Software 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 field 3. Software Defined Radios- All functions, modes and applications can be configured and reconfigured by software SDR 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 RADIO Two-way radio Automatically changes its transmission or reception parameters communicates 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 state FCC –Federal Communication Commission “A software defined radio with a cognitive engine brain".

Cognitive Radio Means “Smart” and “Alert It 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 Radio Radio 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? -Spectrum sensing -Spectrum management -Spectrum mobility -Spectrum sharing awareness 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? External Intelligence Sources Orient Establish Priority Plan Normal Generate Alternatives (Program Generation) Evaluate Alternatives Register to Current Time Decide Alternate Resources Initiate Process(es) (Isochronism Is Key) Act Learn Save Global States Set Display Send a Message Observe Receive a Message Read Buttons Outside World New The Cognition Cycle Prior Pre-process Parse Immediate Urgent Infer on Context Hierarchy Mitola, “Cognitive Radio for Flexible Mobile Multimedia Communications”, IEEE Mobile Multimedia Conference, 1999, pp3-10

Spectrum Sensing Dynamic 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 Contd…

Spectrum Sensing Contd… 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 detection Cooperative detection- information from multiple Cognitive radio users are incorporated for primary user detection. Interference based detection

Spectrum Management Spectrum 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 Sharing Spectrum Sharing – provides the fair spectrum scheduling method One 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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