Fourth Generation Cellular Systems and Smart Antennas Jack H. Winters Division Manager Wireless Systems Research Department AT&T Labs - Research Middletown, NJ jhw@research.att.com November 15, 2001

Goal Wireless communications, anywhere, in any form In any form: high-speed data (Internet) voice audio (music) video Anywhere: home buildings (office) pedestrian vehicles Secure wireless virtual office

OUTLINE Current Systems Current Trends Strategy Proposal Technical Issues

High performance/price High ubiquity and mobility Current Systems Peak Data Rate $ 500,000 $ 1000 $ 100 $ 500 $ 10 $/Cell $/Sub High performance/price 100 Mbps 802.11a 5.5GHz Unlicensed 10 Mbps 802.11b 2.4GHz Unlicensed 3G Wireless ~ 2GHz 1 Mbps BlueTooth 2.4GHz 100 kbps High ubiquity and mobility 10 feet 100 feet 1 mile 10 miles Range 2 mph 10 mph 30 mph 60 mph Mobile Speed

Cellular Data CDPD (US) < 10 kbps GPRS (Asia/trials in US) = 30 kbps (limited work at AT&T Labs since AWS spinoff) EDGE (AWS scaling back plans) = 80 kbps WCDMA = 100 kbps (starting in Japan, but not for several years in US)

Key 802.11b Physical Layer Parameters: Barker Barker CCK CCK 1 ms 11 chips 727 ns 8 chips Key 802.11b Physical Layer Parameters: Data rate: 1, 2, 5.5, 11 Mbps (adaptation to our needs for 1 Mbps only) Modulation/Spreading: Direct Sequence Spread Spectrum (DSSS) DBPSK, DQPSK with 11-chip Barker code (1, 2 Mbps) (this mode stems from the original 802.11 standard) 8-chip complementary code keying (CCK) (5.5, 11 Mbps) optional: packet binary convolutional coding (PBCC), 64 state, rate 1/2 CC (BPSK 5.5 Mbps, QPSK 11 Mbps) Transmission modes: (dynamic rate shifting) Chip rate: 11 MHz Frequency band: Industrial, Scientific and Medical (ISM, unlicensed) 2.4 - 2.4835 GHz Bandwidth: 22 MHz - TDD Channel spacing: 5 MHz Number of channels: Total of 14 (but only the first 11 are used in the US) Carrier accuracy: ±25 ppm

User data rates (Mbps): 3.2 ms FFT G 4 ms 52=48+4 tones 64 point FFT Key 802.11a Physical Layer Parameters: Data rate: 6, 9*, 12, 18*, 24, 36*, 48*, 54* Mbps Modulation: BPSK, QPSK, 16QAM, 64QAM* Coding rate: 1/2, 2/3, 3/4* User data rates (Mbps): Subcarriers: 52 BPSK QPSK QAM16 QAM64 Pilot subcarriers: 4 R=1/2 6 12 24 FFT size: 64 Symbol duration: 4 ms R=2/3 48 Guard interval: 800 ns R=3/4 9 18 36 54 Subcarrier spacing: 312.5 kHz Bandwidth: 16.56 MHz - TDD Channel spacing: 20 MHz Frequency band: Unlicensed national infrastructure (U-NII) Number of channels: Total of 12 in three blocks between 5 and 6 GHz Carrier accuracy: 20 ppm Carrier accuracy @5.8GHz: 114 kHz * optional

Current Trends Enterprise and Home users are all potential public WLAN users when they are away from the office or home. Players: MobileStar, WayPort, AerZone, … Soon to cover over 400 hotels & 50 airports US, Canada, UK $2.50/quarter-hour $15 ~ $60/month (depending on minutes cap) (struggling to define pricing) Jan 2001: Starbucks+MSN plans to install WLANs in all 3,000 stores WayPort and Dell team to give customers wireless public Internet Access http://www.wayport.com/ Spontaneous appearance of neighborhood/residential access sites via consumer broadband wire-line connections

Community 802.11b LANs Bay Area 802.11b Access Point Map North America Bay Area Wireless User Group Equip2rip (Oahu, HI) Guerrilla.net (Boston) Pdx Personal Telco pdxwireless.org (Portland, Oregon) SBAY.ORG Wireless Network (San Francisco Bay Area) Seattle Wireless (Seattle) Seattle Wireless Internet Project SFLAN (San Francisco) Xlan (Seattle) Europe Consume (London, UK) Elektrosmog (Stockholm and Gothenburg) Wlan.org.uk (UK) Wireless France (France) Wireless MediaPoli (Helsinki) Australia Bay Area 802.11b Access Point Map

Possible Strategies Broadband Residential Access Provide 802.11b’s to selected cable modem customers or pole locations for universal wireless high-speed data coverage (1 mile radius) with access to other homes in neighborhood Since cable modem is at 1.5 Mbps and 802.11b is at 11 Mbps, provide fiber to these selected homes or poles (economical for selected homes) Broadband Business Access Fiber to building access points (e.g., floors) Extend to residences for virtual offices

WLAN Overlay for Broadband Cable Infrastructure HYBRID FIBER WIRELESS Logical fit with cable infrastructure Responds to ad-hoc and organized competition Potential for higher data rate alternative to DOCSIS Synergy with streaming digital media

Hybrid Fiber Wireless Run fiber down streets (or to selected homes/businesses) to access points (1 mile apart) for universal coverage with one infrastructure) Start with wireless data access (802.11b) Extend range and migrate to: Voice (802.11e) Audio (music) Video Mobility Higher data rates (54 Mbps - 802.11a => 216 Mbps) Virtual personal/office (remote workforce) environment

Internet Roaming Internet Wireless LAN’s Cellular Wireless Home Seamless handoffs between WLAN and WAN high-performance when possible ubiquity with reduced throughput management/brokering of consolidated WLAN and WAN access adaptive or performance-aware applications I-mobile, CC/PP, location based Cellular Wireless Internet Wireless LAN’s Home Enterprise Public

Technical Issues Voice Music streaming Video streaming Secure virtual office Universal coverage Range (delay spread) Mobility High data rates Capacity (interference) Key constraint: Stay within existing standards/standard evolution (enhance performance within standards and drive standards evolution)

Physical Layer Enhancements Peak Data Rate $ 500,000 $ 1000 $ 100 $ 500 $ 10 $/Cell $/Sub High performance/price 100 Mbps 802.11a 5.5GHz Unlicensed 10 Mbps 802.11b 2.4GHz Unlicensed 3G Wireless ~ 2GHz 1 Mbps Enhanced BlueTooth 2.4GHz 100 kbps High ubiquity and mobility Range 10 feet 100 feet 1 mile 10 miles 2 mph 10 mph 30 mph 60 mph Mobile Speed

Physical Layer Enhancements Physical Layer research Smart antennas for range/capacity enhancement (keeping within standards, using TDD) Smart antennas using MIMO for 216 Mbps 802.11a Equalizers for delay spread robustness Adaptive coding/modulation, dynamic packet assignment, power control (using cellular techniques – radio resource management - in WLANs) Modification of 802.11a (a+) for the outdoor environment

Physical Layer Enhancements Physical Layer research Experiments: 20 MHz MIMO channel measurements Smart antennas in 802.11b/a 216 Mbps MIMO 802.11a 4G streaming downlink

Smart Antennas Smart Antennas significantly improve performance: SIGNAL INTERFERENCE BEAMFORMER WEIGHTS SIGNAL OUTPUT Smart Antennas significantly improve performance: Higher antenna gain  Range extension (50 to 100% greater coverage) Interference suppression  Quality and capacity improvement (>2x) MIMO capacity increase (with smart antennas at Tx/Rx)

Smart Antennas for Cellular Key enhancement technique to increase system capacity, extend coverage, and improve user experience Uplink Adaptive Antenna INTERFERENCE SIGNAL OUTPUT BEAMFORMER WEIGHTS Downlink Switched Beam Antenna SIGNAL OUTPUT INTERFERENCE BEAMFORMER BEAM SELECT Aggressive frequency re-use  High spectrum efficiency  Increased co-channel interference Smart antennas provide substantial interference suppression for enhanced performance

Multiple-Input Multiple-Output (MIMO) Radio With M transmit and M receive antennas, can provide M independent channels, to increase data rate M-fold with no increase in transmit power (with sufficient multipath) AT&T measurements show 4x bit rates & capacity increase in full mobile & indoor/outdoor environments (4 Tx and 4 Rx antennas) 216 Mbps 802.11a 1.5 Mbps EDGE WCDMA

Test Bed Receivers with Rooftop Antennas Terminal Antennas on a Laptop MIMO Channel Testing Mobile Transmitters Test Bed Receivers with Rooftop Antennas W1 Tx Rx Perform timing recovery and symbol synchronization Record 4x4 complex channel matrix Evaluate capacity and channel correlation W2 Tx Rx W3 Tx Rx Terminal Antennas on a Laptop W4 Tx Rx Prototype Dual Antenna Handset Synchronous test sequences LO LO Rooftop Base Station Antennas 11.3 ft Mobile Transmitters

MIMO Antennas Base Station Antennas Laptop Prototype Antennas mounted on 60 foot tower on 5 story office building Dual-polarized slant 45 1900 MHz sector antennas and fixed multibeam antenna with 4 - 30 beams 4 patch antennas at 1900 MHz separated by 3 inches (/2 wavelengths) Laptop prototype made of brass with adjustable PCB lid

MIMO Field Test Results Measured capacity distribution is close to the ideal for 4 transmit and 4 receive antennas

Smart Antennas for WLANs AP Smart Antenna AP Smart Antenna Interference Smart Antennas can significantly improve the performance of WLANs TDD operation Interference suppression  Improve system capacity and throughput Supports aggressive frequency re-use for higher spectrum efficiency, robustness in the ISM band (microwave ovens, outdoor lights) Higher antenna gain  Extend range (outdoor coverage) and lower cost (gain limits) Multipath diversity gain  Improve reliability MIMO (multiple antennas at AP and laptop)  Increase data rates

Smart Antennas Adaptive MIMO Adapt among: antenna gain for range extension interference suppression for capacity (with frequency reuse) MIMO for data rate increase With 4 antennas at access point and terminal, in 802.11a have the potential to provide up to 216 Mbps in 20 MHz bandwidth within the standard In EDGE/GPRS, 4 antennas provide 4-fold data rate increase (to 1.5 Mbps in EDGE) In WCDMA, BLAST techniques proposed by Lucent

Delay Spread Robustness When path length differences approach data rate, ISI degrades performance: 802.11b/a can only tolerate about 200 ns rms of delay spread Outdoor environment can have several microseconds of delay spread => Enhance receiver with equalizer in 802.11b and 802.11a

Capacity When users in adjacent cells request same data stream (video/audio), use simulcasting (same signal at same frequency from all access points) In 802.11a, enhances coverage while frequency reuse of 1 increases capacity Lack of cochannel interference enhances MIMO advantage Adaptively adjust between simulcasting and unicasting

High performance/price High ubiquity and mobility Standards Evolution Peak Data Rate $ 500,000 $ 1000 $ 100 $ 500 $ 10 $/Cell $/Sub High performance/price 100 Mbps 802.11a 5.5GHz Unlicensed 10 Mbps 802.11b 2.4GHz Unlicensed 802.11a + 3G Wireless ~ 2GHz 1 Mbps BlueTooth 2.4GHz 100 kbps High ubiquity and mobility Range 10 feet 100 feet 1 mile 10 miles 2 mph 10 mph 30 mph 60 mph Mobile Speed

Issues: FFT G Data rate: 6, 9, 12, 18, 24, 36, 48, 54 Mbps Modulation: 3.2 ms FFT G 4 ms 52=48+4 tones 64 point FFT Issues: Data rate: 6, 9, 12, 18, 24, 36, 48, 54 Mbps Modulation: BPSK, QPSK, 16QAM, 64QAM Coding rate: 1/2, 2/3, 3/4 Subcarriers: 52 - insufficient for high data rates in wide area Pilots subcarriers: 4 - insufficient if number of subcarriers increased FFT size: 64 - too small for number of carriers in crowded spectrum Symbol duration: 4 ms - too short for efficient wide area operation Guard interval: 800 ns - too short for wide area operation Subcarrier spacing: 312.5 kHz - too large for narrow channels Bandwidth: 16.56 MHz - too large for spectrum available Channel spacing: 20 MHz Carrier accuracy: 20 ppm - leads to too much carrier error Carrier error @5.8GHz: 114 kHz - too much for narrower channel spacing, even at 1.9 GHz

User data rates (Mbps): 204.8 ms FFT G 230.4 ms 832=768+64 tones 2048 point FFT Changes for high-mobility operation: Data rate: 1.66, 2.5, 3.33, 5, 6.66, 10, 13.33, 15 Mbps Modulation: BPSK, QPSK, 16QAM, 64QAM Coding rate: 1/2, 2/3, 3/4 BPSK QPSK QAM16 QAM64 1.66 3.33 6.66 R=1/2 13.33 R=2/3 2.5 5 10 15 R=3/4 User data rates (Mbps): subcarriers: 832 = 52*16 Pilot subcarriers: 64 = 4*16 FFT size: 2048 = 64*32 Symbol duration: 230.4 ms = 3.2*64 + .8*32 Guard interval: 25.6 ms = .8*32 Subcarrier spacing: 4.833 kHz = 312.5/64 Bandwidth: ~5 MHz » 16.56/4 Channel spacing: 5 MHz » 20/4 Carrier accuracy: .5 ppm for 5 GHz, 1 ppm for 2.4 GHz Carrier error @5.8GHz: 2.9 kHz, 1.9 kHz @ 1.9 GHz

OFDM tradeoffs DVB-T 2k mode 802.11a 4G Data rate 6, 9, 12, 18, 24, 36, 48, 54 Mb/s 2.56-8.96 Mb/s 4.98-31.67 Mb/s Tone modulation BPSK, QPSK, 16QAM, 64QAM QPSK, “16QAM,” “64QAM” QPSK,16QAM Coding rate 1/2, 2/3, 3/4 1/2, 2/3, 3/4, 7/8 [1/2, 2/3, 3/4, 5/6, 7/8] + RS(204,88) Nt 52 640 1705 tB 4 ms 200 ms 231-280 ms tB-tF 800 ns 40 ms 7-56 ms ft 312.5 kHz 6.25 kHz 4.464 kHz fB 16.56 MHz 4 MHz 7.6 MHz fop ~5 GHz ~2 GHz ~500 MHz

Smart Antennas for Cellular and 802.11 Conclusions Smart antennas can improve user experience and system capacity by reducing interference, extending range, increasing data rates, and improving quality Smart antennas are implemented in the physical layer with little or no impact on standards We will leverage our expertise and experience in the development and deployment of smart antennas for cellular to develop smart antennas for WLANs