COGNITIVE RADIO. Priyesh V.P.

Transcription

1 COGNITIVE RADIO Priyesh V.P.

2 Introduction We get kicked off the Net as computers competing for bandwidth interfere with one another. We require a rich set of digital services but present communications have limited communication capabilities (e.g. C2000 system based on TETRA). Other public telecommunication networks like GPRS are unreliable. Different networks could work in different frequency bands. International networks could exploit different protocols. High performance ad hoc networks for instant internet access.

3 STPF s Observation Some spectrum is intensively used Other spectrum has highly variable use in when viewed in terms of time and geography

4 COGNITIVE RADIO Allow secondary users to access to the spectrum holes that are unutilized by the primary user. A cognitive radio senses the spectral environment over a wide frequency band and exploits this information to opportunistically provide wireless links that can best meet the demand of the user, but also of its radio environments. The cognitive radio devices have two important functionalities: spectrum sensing and adaptation. Thus, cognitive radio allows users to utilize a frequency band more densely in time and space, thereby leading to a drastic increase of the total spectrum efficiency.

5 Promoting Access to Spectrum Licensee 2 nd -ary User 2 nd -ary User Not-to-Interfere Basis Easement User Below the Acceptable Interference Temperature

6 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

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

8 Time - Frequency - Space Each Domain has Opportunities for Spectral Reuse Transmitter forms Beam Toward Intended Recipient Receiver forms Null Toward Interference Sources R1,R4 T2 T1 Interfering Signal Placed In Null R3,T4 R3 T3 Spatial - Beam steering and Null Steering

9 Features of SDR Implementation SDR Products and Technology are a Reality Today. SDRs are being standardised widely. Ability to Implement Protocols and Policies. New Realms of Knowledge and Information Transfer are Achievable.

10 Conclusion Drawbacks can be solved. Great number of advantages. Next revolution in communication industry.

11 References 1. Cognitive Radio Architecture by Joseph Mitola. 2. FCC Seminar On Spectrum Usage by Bruce Fette. 3. Cognitive Radio Implementation Seminar by Vanwazer Engineering-Foundations/dp/B000SW4BWI Spingerlink. 8. MIT news.