William Krenik and Anuj Batra Texas Instruments Incorporated

12500 TI Blvd., MS 8723Dallas, Texas 75243, USA

214-480-6448w-krenik@ti.com

Cognitive Radio Techniques for Wide Area Networks

Outline

1. Motivation2. Basic Concepts3. Unlicensed Wide Area Networks4. Regulation and Deployment5. Q&A

Spectrum Allocation

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

The Need for Spectrum

Service Avail. Data

Rate

Eff.

Bps/Hz

Technology Spec.

Need

Voice Today ~10kbps ~0.1-0.2 TDMA 1X

UMTS Today 384kbps ~0.2-0.3 W-CDMA, QPSK ~2-4X

HSDPA 2006 ~10Mbps ~1 Scheduling, HARQ, QAM

~10X

3.9G ~2009 ~100Mbps ~3-4 OFDM, MIMO, Scheduling (small

cells, WLAN)

~20X

4G ~2015 ~1Gbps ?? Directional antennas?

???

Air Interface Technology:Advanced/adaptive modulation and codingSophisticated schedulingMIMO / directional antennas

Network Design:Use more smaller cellsUse WLAN whenever possibleSmaller cells and WLAN use high freq. bands

Open New Spectrum:Digital TV Bill in Congress nowOpen all available bands ($$$)Share idle spectrum

1. Most spectrum is idle most of the time2. Lowers costs for service providers3. Lowers costs for consumers4. 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 3-10.

"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

How LANs share spectrum

AccessPoint

1. “Listen” before transmitting

2. When a collision occurs:1. pick a random time to wait2. 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 efficient2. Thousands of possible interferers3. 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 signal3. Complain on a shared control channel4. Complain on a shared control channel before

the secondary users interfere with them

Interference Temperature

UWAN Operation

1. UE1 requests service from BTS1 over RCC2. BTS1 checks ARM for available spectrum, checks etiquette rules, updates ARM3. BTS1 directs UE1 to channel, BW, and waveform4. UE3 & UE4 arrange session over RCC5. 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!