Fourth Generation Cellular Systems and Smart Antennas Jack

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 (until 3/22/02 – then www. allcomms. com) AT&T Labs - Research

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 AT&T Labs - Research

OUTLINE • Current Systems • Current Trends • Strategy Proposal • Technical Issues AT&T Labs - Research

Current Systems Peak Data Rate High performance/price 100 Mbps 802. 11 a 5. 5 GHz Unlicensed 10 Mbps 802. 11 b $/Cell $/Sub $ 500, 000 $ 500 $ 100 $ 10 2. 4 GHz Unlicensed 1 Mbps Blue. Tooth 100 kbps 2. 4 GHz High ubiquity and mobility 3 G Wireless ~ 2 GHz 10 feet 2 mph 100 feet 10 mph 1 mile 30 mph 10 miles Range 60 mph Mobile Speed AT&T Labs - Research

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) AT&T Labs - Research

Barker 1 ms 11 chips CCK 727 ns 8 chips Key 802. 11 b Physical Layer Parameters: Data rate: Modulation/Spreading: Transmission modes: (dynamic rate shifting) Chip rate: Frequency band: Bandwidth: Channel spacing: Number of channels: Carrier accuracy: 1, 2, 5. 5, 11 Mbps (adaptation to our needs for 1 Mbps only) 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) 11 MHz Industrial, Scientific and Medical (ISM, unlicensed) 2. 4 - 2. 4835 GHz 22 MHz - TDD 5 MHz Total of 14 (but only the first 11 are used in the US) ± 25 ppm AT&T Labs - Research

3. 2 ms FFT 52=48+4 tones 64 point FFT G 4 ms Key 802. 11 a Physical Layer Parameters: Data rate: Modulation: Coding rate: Subcarriers: Pilot subcarriers: FFT size: Symbol duration: Guard interval: Subcarrier spacing: Bandwidth: Channel spacing: Frequency band: Number of channels: Carrier accuracy @5. 8 GHz: 6, 9*, 12, 18*, 24, 36*, 48*, 54* Mbps BPSK, QPSK, 16 QAM, 64 QAM* 1/2, 2/3, 3/4* User data rates (Mbps): 52 BPSK QAM 16 QAM 64 4 R=1/2 6 12 24 64 R=2/3 48 4 ms R=3/4 9 18 36 54 800 ns 312. 5 k. Hz 16. 56 MHz - TDD 20 MHz Unlicensed national infrastructure (U-NII) Total of 12 in three blocks between 5 and 6 GHz 20 ppm 114 k. Hz * optional AT&T Labs - Research

Current Trends • Enterprise and Home users are all potential public WLAN users when they are away from the office or home. • Players: Mobile. Star, Way. Port, Aer. Zone, … – Soon to cover 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 Way. Port 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 AT&T Labs - Research

Community 802. 11 b LANs • North America – Bay Area Wireless User Group – Equip 2 rip (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 Media. Poli (Helsinki) • Bay Area 802. 11 b Access Point Map Australia AT&T Labs - Research

Possible Strategies • Broadband Residential Access – Provide 802. 11 b’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. 11 b 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 AT&T Labs - Research

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 AT&T Labs - Research

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. 11 b) – Extend range and migrate to: • • • Voice (802. 11 e) Audio (music) Video Mobility Higher data rates (54 Mbps - 802. 11 a => 216 Mbps) – Virtual personal/office (remote workforce) environment AT&T Labs - Research

Internet Roaming • Seamless handoffs between WLAN and WAN – high-performance when possible Cellular Wireless – ubiquity with reduced throughput • management/brokering of consolidated WLAN and WAN access • adaptive or performance-aware applications – I-mobile, CC/PP, location based Internet Wireless LAN’s Enterprise Home Public AT&T Labs - Research

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) AT&T Labs - Research

Physical Layer Enhancements Peak Data Rate High performance/price 100 Mbps 802. 11 a 5. 5 GHz Unlicensed 10 Mbps 802. 11 b 2. 4 GHz Unlicensed 1 Mbps $/Cell $/Sub $ 500, 000 $ 500 $ 100 $ 10 Enhanced Blue. Tooth 100 kbps 2. 4 GHz High ubiquity and mobility 3 G Wireless ~ 2 GHz 10 feet 2 mph 100 feet 10 mph 1 mile 30 mph Range 10 miles 60 mph Mobile Speed AT&T Labs - Research

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. 11 a – Equalizers for delay spread robustness – Adaptive coding/modulation, dynamic packet assignment, power control (using cellular techniques – radio resource management - in WLANs) – Modification of 802. 11 a (a+) for the outdoor environment AT&T Labs - Research

Physical Layer Enhancements • Physical Layer research – Experiments: • • 20 MHz MIMO channel measurements Smart antennas in 802. 11 b/a 216 Mbps MIMO 802. 11 a 4 G streaming downlink AT&T Labs - Research

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

Smart Antennas for Cellular • Key enhancement technique to increase system capacity, extend coverage, and improve user experience SIGNAL Uplink Adaptive Antenna SIGNAL OUTPUT INTERFERENCE BEAMFORMER WEIGHTS SIGNAL Aggressive frequency re-use High spectrum efficiency Increased co-channel interference BEAMFORMER Downlink Switched Beam Antenna BEAM SELECT SIGNAL OUTPUT 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 4 x bit rates & capacity increase in full mobile & indoor/outdoor environments (4 Tx and 4 Rx antennas) – 216 Mbps 802. 11 a – 1. 5 Mbps EDGE – WCDMA AT&T Labs - Research

MIMO Channel Testing Mobile Transmitters W 1 Tx W 2 • Perform timing recovery and symbol synchronization Rx • Record 4 x 4 complex channel matrix Rx Tx • Evaluate capacity and channel correlation Rx Tx W 4 Synchronous test sequences Rx Tx W 3 Test Bed Receivers with Rooftop Antennas LO Terminal Antennas on a Laptop LO 11. 3 ft Prototype Dual Antenna Handset Rooftop Base Station Antennas Mobile Transmitters AT&T Labs - Research

MIMO Antennas Base Station Antennas Laptop Prototype • 4 patch antennas at 1900 MHz separated by 3 inches ( /2 wavelengths) • Laptop prototype made of brass with adjustable PCB lid • 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 AT&T Labs - Research

MIMO Field Test Results • Measured capacity distribution is close to the ideal for 4 transmit and 4 receive antennas AT&T Labs - Research

Smart Antennas for WLANs Smart Antenna AP Interference Smart Antennas can significantly improve the performance of WLANs • TDD operation (only need smart antenna at access point or terminal for performance improvement in both directions) • 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 AT&T Labs - Research

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. 11 a 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 AT&T Labs - Research

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 AT&T Labs - Research

Delay Spread Robustness • When path length differences approach data rate, ISI degrades performance: – 802. 11 b/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. 11 b and 802. 11 a AT&T Labs - Research

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. 11 a, enhances coverage while frequency reuse of 1 increases capacity – Lack of cochannel interference enhances MIMO advantage – Adaptively adjust between simulcasting and unicasting AT&T Labs - Research

Standards Evolution Peak Data Rate High performance/price 100 Mbps 802. 11 a 5. 5 GHz Unlicensed 10 Mbps 802. 11 b $/Sub $ 500, 000 $ 500 $ 100 $ 10 802. 11 a + 2. 4 GHz Unlicensed 1 Mbps $/Cell Blue. Tooth 100 kbps 2. 4 GHz High ubiquity and mobility 3 G Wireless ~ 2 GHz 10 feet 2 mph 100 feet 10 mph 1 mile 30 mph Range 10 miles 60 mph Mobile Speed AT&T Labs - Research

3. 2 ms FFT G 4 ms 52=48+4 tones 64 point FFT Issues: Data rate: Modulation: Coding rate: Subcarriers: Pilots subcarriers: FFT size: Symbol duration: Guard interval: Subcarrier spacing: Bandwidth: Channel spacing: Carrier accuracy: Carrier error @5. 8 GHz: 6, 9, 12, 18, 24, 36, 48, 54 Mbps BPSK, QPSK, 16 QAM, 64 QAM 1/2, 2/3, 3/4 52 - insufficient for high data rates in wide area 4 - insufficient if number of subcarriers increased 64 - too small for number of carriers in crowded spectrum 4 ms - too short for efficient wide area operation 800 ns - too short for wide area operation 312. 5 k. Hz - too large for narrow channels 16. 56 MHz - too large for spectrum available 20 MHz 20 ppm - leads to too much carrier error 114 k. Hz - too much for narrower channel spacing, even at 1. 9 GHz AT&T Labs - Research

204. 8 ms FFT 832=768+64 tones 2048 point FFT G 230. 4 ms Changes for high-mobility operation: Data rate: Modulation: Coding rate: subcarriers: Pilot subcarriers: FFT size: Symbol duration: Guard interval: Subcarrier spacing: Bandwidth: Channel spacing: Carrier accuracy: Carrier error @5. 8 GHz: 1. 66, 2. 5, 3. 33, 5, 6. 66, 10, 13. 33, 15 Mbps BPSK, QPSK, 16 QAM, 64 QAM 1/2, 2/3, 3/4 User data rates (Mbps): 832 = 52*16 BPSK QAM 16 QAM 64 64 = 4*16 R=1/2 1. 66 3. 33 6. 66 2048 = 64*32 R=2/3 13. 33 230. 4 ms = 3. 2*64 +. 8*32 R=3/4 2. 5 5 10 15 25. 6 ms =. 8*32 4. 833 k. Hz = 312. 5/64 ~5 MHz » 16. 56/4 5 MHz » 20/4. 5 ppm for 5 GHz, 1 ppm for 2. 4 GHz 2. 9 k. Hz, 1. 9 k. Hz @ 1. 9 GHz AT&T Labs - Research

OFDM tradeoffs 802. 11 a 4 G DVB-T 2 k mode 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 Coding rate BPSK, QPSK, 16 QAM, 64 QAM QPSK, 16 QAM QPSK, “ 16 QAM, ” “ 64 QAM” 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 t. B 4 ms 200 ms 231 -280 ms t. B-t. F 800 ns 40 ms 7 -56 ms ft 312. 5 k. Hz 6. 25 k. Hz 4. 464 k. Hz f. B 16. 56 MHz 4 MHz 7. 6 MHz fop ~5 GHz ~2 GHz ~500 MHz AT&T Labs - Research

Physical Layer Enhancements Summary • Physical Layer research – Smart antennas for range/capacity enhancement (keeping within standards, using TDD) – Smart antennas using MIMO for 216 Mbps 802. 11 a – Equalizers for delay spread robustness – Adaptive coding/modulation, dynamic packet assignment, power control (using cellular techniques – radio resource management - in WLANs) – Modification of 802. 11 a (a+) for the outdoor environment – Simulcasting for video AT&T Labs - Research