William Krenik and Anuj Batra Texas Instruments Incorporated TI Blvd., MS 8723 Dallas, Texas 75243, USA Cognitive Radio Techniques for Wide Area Networks

Outline 1. Motivation 2. Basic Concepts 3. Unlicensed Wide Area Networks 4. Regulation and Deployment 5. Q&A

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

The Need for Spectrum Service Avail.Data Rate Eff. Bps/Hz TechnologySpec. Need Voice Today~10kbps~ TDMA1X UMTS Today384kbps~ W-CDMA, QPSK~2-4X HSDPA 2006~10Mbps~1Scheduling, HARQ, QAM ~10X 3.9G ~2009~100Mbps~3-4OFDM, MIMO, Scheduling (small cells, WLAN) ~20X 4G ~2015~1Gbps??Directional antennas? ???

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 1.Most spectrum is idle most of the time 2.Lowers costs for service providers 3.Lowers costs for consumers 4.Reduces regulatory burdens for FCC How to get more throughput

Cognitive Radio Adapted From Mitola, “Cognitive Radio for Flexible Mobile Multimedia Communications ”, IEEE Mobile Multimedia Conf., 1999, pp "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 Order, May 2002

How LANs share spectrum Access Point 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

The Hidden Node Problem Highly sensitive handsets could be a partial answer First users could complain: 1.Ramp up their power levels 2.Cut into secondary users with objection signal 3.Complain on a shared control channel 4.Complain on a shared control channel before the secondary users interfere with them

Interference Temperature

UWAN Operation 1.UE1 requests service from BTS1 over RCC 2.BTS1 checks ARM for available spectrum, checks etiquette rules, updates ARM 3.BTS1 directs UE1 to channel, BW, and waveform 4.UE3 & UE4 arrange session over RCC 5.BTS1 monitors RCC, UE3 & UE4 session is not a problem, no objection

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

UWAN Etiquette

UWAN System Complexity

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

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

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

THANK YOU!