Cognitive Radio Techniques for Wide Area Networks

2. Cognitive Radio Techniques for Wide Area Networks William Krenik and Anuj Batra Texas Instruments Incorporated 12500 TI Blvd., MS 8723Dallas, Texas 75243, USA214-480-6448w-krenik@ti.com

3. Outline • Motivation • Basic Concepts • Unlicensed Wide Area Networks • Regulation and Deployment • Q&A

4. Spectrum Allocation Top 60 U.S. Markets have ~180-200MHz licensed for cellular WAN use

5. The Need for Spectrum

6. How to get more throughput • Air Interface Technology: • Advanced/adaptive modulation and coding • Sophisticated scheduling • MIMO / directional antennas • Network Design: • Use more smaller cells • Use WLAN whenever possible • Smaller cells and WLAN use high freq. bands • Open New Spectrum: • Digital TV Bill in Congress now • Open all available bands ($$$) • Share idle spectrum • Most spectrum is idle most of the time • Lowers costs for service providers • Lowers costs for consumers • Reduces regulatory burdens for FCC

7. Cognitive Radio "A cognitive radio is a radio that can change its transmitter parameters based on interactions with the environment in which it operates. The majority of cognitive radios will probably be SDRs (software defined radios), but neither having software nor being field programmable are requirements of a cognitive radio." FCC. ET docket no. 02-25. Order, May 2002 Adapted From Mitola, “Cognitive Radio for Flexible Mobile Multimedia Communications ”, IEEE Mobile Multimedia Conf., 1999, pp 3-10.

8. Access Point How LANs share spectrum 1. “Listen” before transmitting 2. When a collision occurs: 1. pick a random time to wait 2. then try again 3. Take queues from Access Point on when to TX The system is simple and depends on an abundance of spectrum and a small number possible interferers. Radio Link range is limited to ~100 meters A wide area network requires more sophistication: 1. Must be very efficient 2. Thousands of possible interferers 3. Avoid collisions in high mobility network

9. The Hidden Node Problem • Highly sensitive handsets could be a partial answer • First users could complain: • Ramp up their power levels • Cut into secondary users with objection signal • Complain on a shared control channel • Complain on a shared control channel before the secondary users interfere with them

10. Interference Temperature

11. UWAN Operation • UE1 requests service from BTS1 over RCC • BTS1 checks ARM for available spectrum, checks etiquette rules, updates ARM • BTS1 directs UE1 to channel, BW, and waveform • UE3 & UE4 arrange session over RCC • BTS1 monitors RCC, UE3 & UE4 session is not a problem, no objection

12. ARM Includes: GPS Location, TX Power, Directionality, Channel, Modulation, Code, etc.

13. UWAN Etiquette

14. UWAN System Complexity

15. System Complexity • OFDMA is favorable air interface • Modular and flexible • No CDMA related complexity • No complexity increase in air interface, data processing, etc • Adhoc RCC control channel – est. 2-4X complexity vs 3G • GPS or other positioning system required (Indoor positioning?) • Peer-to-peer mode increases complexity • Infrastructure network requires ARM access • Overall system complexity increase is minimal, less than the 2X overall density boost gained from a wafer process node • Flexible RF front-ends are key needed technology: • Programmable MEM filters on the front end • MEMs for automatically tuned impedance matching

16. Regulatory and Deployment Regulatory Government body can adopt industry standard Handset and network compliance mandated Operating licenses for BTS operators (tower restrictions) System upgrades possible over time Deployment Exploits existing network infrastructure Incremental use of new spectrum Appears acceptable to network operators

17. Summary Limited spectrum is a threat to ubiquitous wireless data service Advances in air interface technology cannot meet the need Most spectrum is idle most of the time Cognitive radio can provide a very flexible solution at reasonable complexity level

18. THANK YOU!