Fourth Generation Cellular Systems and Smart Antennas Jack H. Winters April 8, 2002

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

Current Systems 10 feet100 feet1 mile10 miles 100 kbps 1 Mbps 10 Mbps 100 Mbps 3G Wireless ~ 2GHz BlueTooth 2.4GHz a 5.5GHz Unlicensed b 2.4GHz Unlicensed Peak Data Rate Range 2 mph10 mph30 mph 60 mph $ 500,000 $ 1000 $ 100 $ 500 $ 100 $ 10 $/Cell $/Sub High performance/price High ubiquity and mobility 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)

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 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) Barker Key b Physical Layer Parameters: Chip rate:11 MHz Frequency band:Industrial, Scientific and Medical (ISM, unlicensed) GHz Bandwidth:22 MHz - TDD Channel spacing:5 MHz Total of 14 (but only the first 11 are used in the US) Number of channels: Carrier accuracy:±25 ppm Transmission modes: (dynamic rate shifting) CCK 1  s 11 chips Barker 727 ns 8 chips CCK

Unlicensed national infrastructure (U-NII) Total of 12 in three blocks between 5 and 6 GHz 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 Pilot subcarriers:4 G 3.2  s 4  s FFT 52=48+4 tones 64 point FFT Key a Physical Layer Parameters: Symbol duration: 4  s Guard interval:800 ns Subcarrier spacing:312.5 kHz Bandwidth:16.56 MHz - TDD Channel spacing:20 MHz 20 ppm FFT size:64 Carrier accuracy: Carrier kHz BPSKQPSKQAM16QAM R=1/2 48 R=2/ R=3/4 User data rates (Mbps): * optional Frequency band: Number of channels:

Current Trends Enterprise and Home users are all potential public WLAN users when they are away from the office or home Spontaneous appearance of neighborhood/residential access sites via consumer broadband wire-line connections Players: –WayPort: Covers over 400 hotels & 50 airports US, Canada, UK –Aggregators: Deep Blue Wireless (hotels and coffee houses) Joltage Sputnik hereUare Boingo Wireless WayPort and Dell team to give customers wireless public Internet Access –

Community b LANs 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 b Access Point Map

Possible Strategies Broadband Residential Access –Provide 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 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

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 a => 216 Mbps) –Virtual personal/office (remote workforce) environment

Internet Roaming 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 Enterprise Home Public Internet Wireless LAN’s

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 10 feet100 feet1 mile10 miles 100 kbps 1 Mbps 10 Mbps 100 Mbps 3G Wireless ~ 2GHz BlueTooth 2.4GHz a 5.5GHz Unlicensed b 2.4GHz Unlicensed Peak Data Rate Range 2 mph10 mph30 mph 60 mph $ 500,000 $ 1000 $ 100 $ 500 $ 100 $ 10 $/Cell $/Sub High performance/price High ubiquity and mobility Mobile Speed Enhanced

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

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

Smart Antennas 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) SIGNAL INTERFERENCE BEAMFORMER WEIGHTS SIGNAL OUTPUT

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

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 a –1.5 Mbps EDGE –WCDMA

Rx MIMO Channel Testing W1W1 W2W2 W3W3 W4W4 LO Synchronous test sequences Rx Perform timing recovery and symbol synchronization Record 4x4 complex channel matrix Evaluate capacity and channel correlation LO Mobile Transmitters Test Bed Receivers with Rooftop Antennas Terminal Antennas on a Laptop Tx Rooftop Base Station Antennas 11.3 ft Prototype Dual Antenna Handset 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  beams 4 patch antennas at 1900 MHz separated by 3 inches ( /2 wavelengths) Laptop prototype made of brass with adjustable PCB lid

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

Smart Antennas for 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 AP Smart Antenna Interference Smart Antennas can significantly improve the performance of WLANs AP Smart Antenna

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 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

Smart Antennas for Cellular and 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

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 b and a

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

Standards Evolution 10 feet100 feet1 mile10 miles 100 kbps 1 Mbps 10 Mbps 100 Mbps 3G Wireless ~ 2GHz BlueTooth 2.4GHz a a 5.5GHz Unlicensed b 2.4GHz Unlicensed Peak Data Rate Range 2 mph10 mph30 mph 60 mph $ 500,000 $ 1000 $ 100 $ 500 $ 100 $ 10 $/Cell $/Sub High performance/price High ubiquity and mobility Mobile Speed

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 Symbol duration: 4  s - 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 G 3.2  s 4  s FFT Carrier accuracy:20 ppm - leads to too much carrier error Carrier kHz - too much for narrower channel spacing, even at 1.9 GHz Issues: Data rate:6, 9, 12, 18, 24, 36, 48, 54 Mbps Modulation:BPSK, QPSK, 16QAM, 64QAM 52=48+4 tones 64 point FFT FFT size:64 - too small for number of carriers in crowded spectrum

Coding rate:1/2, 2/3, 3/4 subcarriers: G  s FFT Data rate:1.66, 2.5, 3.33, 5, 6.66, 10, 13.33, 15 Mbps Modulation:BPSK, QPSK, 16QAM, 64QAM 832 = 52*  s 832= tones 2048 point FFT Changes for high-mobility operation: FFT size:2048 = 64*32 Symbol duration:  s = 3.2*64 +.8*32 Guard interval: 25.6  s =.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 kHz, GHz Pilot subcarriers:64 = 4*16 BPSKQPSKQAM16QAM R=1/ R=2/ R=3/4 User data rates (Mbps):

OFDM tradeoffs a DVB-T 2k mode 4G Data rate 6, 9, 12, 18, 24, 36, 48, 54 Mb/s Tone modulation BPSK, QPSK, 16QAM, 64QAM Coding rate 1/2, 2/3, 3/4 NtNt 52 tBtB 4  s t B -t F 800 ns ftft kHz fBfB MHz f op ~5 GHz Mb/s QPSK, “16QAM,” “64QAM” [1/2, 2/3, 3/4, 5/6, 7/8] + RS(204,88)  s 7-56  s kHz 7.6 MHz ~500 MHz Mb/s QPSK,16QAM 1/2, 2/3, 3/4, 7/  s 40  s 6.25 kHz 4 MHz ~2 GHz

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 a –Equalizers for delay spread robustness –Adaptive coding/modulation, dynamic packet assignment, power control (using cellular techniques – radio resource management - in WLANs) –Modification of a (a+) for the outdoor environment –Simulcasting for video