Cognitive Radio Based 5G Wireless Networks

1. Cognitive Radio Based 5G Wireless Networks 1

2. 2 I. Introduction Different spectrum bands for different services

3. Exponential Growth in Number of Wireless Applications Over 5G Networks

4. More and more people subscribe to one or many of the wireless services Rapid growth of wireless devices Increasing demand for additional bandwidth Increasing Demand For Spectrum Use

5. Global Cell Phone Users > 2 Billion New Cell Phone Sales > 1 Billion (2006) #1 Cell Phone Country –China > 400M European Union > 450M U.S. > 200M Recorded usage in 221 Countries SMS Messages -235M (36/user/month) Cell Phone Statistics (2006)

6. 6 Background and Motivations Crowded radio spectrum

7. 7 Background and Motivations Low spectrum utilization

8. Examples of the Spectrum Opportunities Most of the spectrum is unused Evidence of overcrowding 54 MHz to 88 MHz (TV broadcasting), 24 hour period starting during Sep. 01 to Sep. 09 2009

9. Examples of the Spectrum Opportunities Most of the spectrum is unused Evidence of overcrowding 2390 MHz to 2500 MHz (mobile satellite), 24 hour period starting during Sep. 01 to Sep. 09 2009

10. Example of the Spectrum Opportunities Spectrum hole analysis for 54 – 88 MHz frequency band.

11. Example of the Spectrum Opportunities Spectrum hole analysis for 2390 – 2500 MHz frequency band.

12. Spectrum Occupancy Measurements in Seven Different Places Most of the spectrum in most of the places at most of the time is completed unused!

13. Current Spectrum Allocation Policies Today, frequency bands are statically assigned to specific wireless operators/services. Frequency allocation policies lead to a low utilization of the licensed frequency spectrum. For example, in most of the time only 6% of the frequency spectrum is active. Current spectrum policy needs to be reconsidered ! Solutions?

14. 14 II. Cognitive Radio (CR) Large amount of white space in time and frequency • Unused portions of licensed spectrum is called spectrum holes or White Spaces. • Dynamic spectrum sensing helps with identifying and assessing quality of unused channels

15. 15 Cognitive Radio: Basic Idea Cognitive Radio (CR) technique has been proposed by the Federal Communication Committee (FCC) as a solution to such spectrum scarcity problem. • Cognitive radios enhance the control process by adding: • Intelligent control of radio; • Ability to sense the environment; • Processes for learning about environmental parameters; • Awareness of its environment: signals & channels; • Awareness of capabilities of the radio; • Ability to negotiate waveforms with other radios.

16. 16 Definitions Why So Many Definitions? FCC: “A radio that can change its transmitter parameters based on interaction with the environment in which it operates.” ITU (Wp8A): “A radio or system that senses and is aware of its operational environment and can dynamically and autonomously adjust its radio operating parameters accordingly.” IEEE USA “A radio frequency transmitter/receiver that is designed to intelligently detect whether a particular segment of the radio spectrum is currently in use, and to jump into (and out of, as necessary) the temporarily-unused spectrum very rapidly, without interfering with the transmissions of other authorized users.”

17. Our cognitive radio definition • Cognitive radio is an intelligent wireless communication system that is aware of its surrounding environment and uses methodology of understand-by-building to learn from environment and adapt  its internal states to statistical variations by making corresponding changes in its operating parameters. • Intelligence is defined as “The capacity to acquire and apply knowledge, especially toward a purposeful goal.”

18. Cognitive Radio Applications

19. Overlays (e.g. Cognitive Radio –Frequency Agile / Smart Radios / Software Defined Radio) Creation of Unlicensed Bands (esp. ISM / UNII –0.9, 2.4, 5 GHz) Underlays (e.g. Ultrawideband –UWB –min. 500 MHz bandwidth) Three Solutions

20. Cognitive Radio Wireless Networks • Two types of cognitive users • Primary users (PUs) or licensed users • Secondary users (SUs) or unlicensed users • Two types of cognitive radio networks • Synchronous • Asynchronous • Three types of spectrum sharing modes • Overlay • Underlay • Interweave

21. PUs & SUs • Primary User: A user who has higher priority or legacy rights on the usage of a specific part of the spectrum. • Secondary User: A user who has a lower priority and therefore exploits the spectrum in such a way that it does not cause interference to primary users. • Spectrum Sensing: The task of obtaining awareness about the spectrum usage and existence of primary users in a geographical area.

22. PUs & SUs • SUs can sense occupancy of licensed channels and use licensed channels when they are not occupied by PUs based on spectrum sensing results. • PUs and SUs form primary wireless network and secondary wireless network (cognitive radio network), respectively.

23. Time axis is divided into slots SUs are synchronized with PUs Same knowledge on the time-slot boundary PUs spectrum activity is consistent during a given time slot 1) Synchronous Cognitive Radio Networks An example of Synchronous CRN with interweave spectrum sharing mode

24. SUs are NOT synchronized with the PUs • Different licensed channels for different types of PUs can also be asynchronous 2) Asynchronous Cognitive Radio Networks

25. Overlay Cognitive radios overhear and enhance PU’s` transmissions Underlay Cognitive radios constrained to cause minimal interference to PUs Interweave Cognitive radios find and exploit spectral holes to avoid interfering with PUs Cognitive Radio Spectrum Sharing Modes Knowledge and Complexity

26. Type 1: Overlay • SUs may use a part of their energy to assist communications of PUs through cooperative communication techniques and the rest of energy to transmit their own signals. • Interference from SUs' signals can be compensated with gain for PUs' signal quality through cooperation of SUs. • It requires SUs to know PUs' packets before PUs begin their transmissions Spectrum Sharing Modes (1) SU R2 SU R1 PU S PU D

27. Type 2: Underlay • SUs transmit signals in such a low-power level that interference caused by SUs is below noise floor of the spectrum. • In the view point of PUs, transmissions by SUs are nothing but noise with low-level power. • SUs and PUs can co-exist in same spectrum • If PUs’ topology and transmission power do not change • No need to sense the channel • Do not cause packet collision for PUs for both synchronous and asynchronous cognitive networks Spectrum Sharing Modes (2)

28. Type 3: Interweave • Listen first and talk later • Exclusive utilization • SUs frequently sense channel • SUs do not need to worry about interference temperature constraint of PUs • Relax power constraints imposed onto SUs as compared with underlay spectrum sharing mode. • No interference to PUs in synchronous CRNs • Inevitable interference to PUs in asynchronous CRNs due to half-duplex nature of wireless radios Spectrum Sharing Modes (3)