Introduction CR Intelligent Wireless Technology. a radio that is aware of its surroundings and adapts intelligentlyIntelligence Searching the spectrum. Cognitive radio requirements co-exists with legacy wireless systems uses their spectrum resources does not interfere with them
Introduction Embedded intelligence to determine optimal transmission and vary communication parameters (bandwidth, center frequency, QoS) based on primary users’ behavior Defining new concepts: Spectrum sharing. Adaptive parameters.
Why CR? Recent measurements by the FCC in the US show 70% of the allocated spectrum is not utilized. (Spectrum scarcity)
Why CR? Bandwidth is expensive and good frequencies are taken Unlicensed bands – biggest innovations in spectrum efficiency. Spectrum utilization.
Applications Band sharing, emergency services, broadband wireless services, multi-media networking Non-time sensitive services, such as downloading could be most appropriate.
Cont. Application Cellular operator Local KAUST free mobile network. Sensing is limited of the operator’s band.
Challenges Hidden tunnel Cooperative Spectrum Sensing Controlling CRs to ensure they have the same spectrum picture. Spectrum sharing Could add lots of interference. Scarcer resources. A lot of control communications (increase throughput)
Mathematical tool that can help in reducing the number of measurements to solve a system given it is sparse. What is Compressive Sensing?
Cont. What is Compressive Sensing? N equations is needed to solve this system. M=N.
Cont. What is Compressive Sensing? S = number of nonzero elements in U. S<
Control Channels On Cognitive radio. Handles the control communication between Cognitive base station (CBS) and Cognitive Radios (CR). Ex. spectrum sensing information. Share scarce resources. Collision Happens. Collision Resolving Algorithms Should Be Applied. The channel is given to the strongest connection users: Support Higher rates. Increase throughput.
Control Channels On Cognitive radio. DataReservation Increase Throughput: Increase the frame length. Decrease Reservation Time
DataReservation Control Channels On Cognitive radio.
Apply Compressive Sensing to Optimize the number of slots. DataReservation
Compressive Sensing Protocol CBS has fixed reservation slots=m. CBS sends a beacon with a threshold level L. CRs compare their channel gain a with L. If a>L Strong Connection CR (SCR) Otherwise, Weak connection (WCR)
Cont. Compressive Sensing Protocol WCR go to sleep mode. Saves Battery. Eliminate WCRs that can cause slow rates and interference. SCR multiplies 1 by random sequence of length m +1 &-1 and reply on all slots.
Cont. Compressive Sensing Protocol CBS then knows SCRs. It reserves the channel randomly to any of SCRs. CBS receives the replies and form the system of independent equations.
Cont. Compressive Sensing Protocol CBS senses the spectrum and send the spectrum information to SCRs. SCRs sense spectrum and compare with CBS. If SCRs agree it remains silent and apply the decision. If SCRs object they reply back. CBS base a new decision on the amount of objection to its decision.
Cont. Compressive Sensing Protocol Advantages: Shared control channels are used. Limit collision by limiting the number of users. decrease reservation time and increase data time. Strong connection users only use channel.
Control Channels On Cognitive radio Traditional way N users send their ID and Channel gain G to reserve the channel.
Apply Compressive Sensing to decrease reservation Time If N is limited to s users need to send s<
The goal Increase throughput. Give channels to strong connection users. They support high rates. Limit the activity of weak connection users.