1. Fourth Generation Cellular Systems and Smart Antennas Jack H. Winters April 9, 2002 jack@jackwinters.com

2. 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

3. OUTLINE Current Systems Current Trends Strategy Proposal Technical Issues

4. Current Systems 10 feet100 feet1 mile10 miles 100 kbps 1 Mbps 10 Mbps 100 Mbps 3G Wireless ~ 2GHz BlueTooth 2.4GHz 802.11a 5.5GHz Unlicensed 802.11b 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

5. Cellular Data CDPD (US) < 10 kbps GPRS = 30-40 kbps EDGE = 80 kbps WCDMA = 100 kbps (starting in Japan, but not for several years in US)

6. Data rate: 1, 2, 5.5, 11 Mbps 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) Barker Key 802.11b Physical Layer Parameters: 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 Total of 14 (but only the first 11 are used in the US), with only 3 nonoverlapping channels Number of channels: Transmission modes: (dynamic rate shifting) CCK 1  s 11 chips Barker 727 ns 8 chips CCK

7. Unlicensed national infrastructure (U-NII), 5.5 GHz 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 802.11a 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 FFT size:64 : BPSKQPSKQAM16QAM64 61224 R=1/2 48 R=2/3 9183654 R=3/4 User data rates (Mbps): Frequency band: Number of channels:

8. Current Trends Business WLANs dominate, but home usage growing faster (8 million WLANs sold last year) Spontaneous appearance of neighborhood/residential access sites via consumer broadband wire-line connections Public WLAN offerings for enterprise and home users when they are away from the office or home –Players: Wayport: Covers over 450 hotels & 9 airports US, Canada, UK Aggregators: –Deep Blue Wireless (hotels and coffee houses) –Joltage –Sputnik –hereUare –Boingo Wireless//

9. Community 802.11b 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 802.11b Access Point Map

10. 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

11. 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

12. 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 Audio (music) Video Mobility Higher data rates (54 Mbps - 802.11a and higher) Virtual personal/office (remote workforce) environment

13. Technical Issues Voice/Music streaming/Video streaming (802.11e) Universal coverage (Internet roaming) Range Higher data rates Capacity/Interference) Key constraint: Stay within existing standards/standard evolution (enhance performance within standards and drive standards evolution)

14. 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 Nokia GPRS/802.11b PCMCIA card NTT DoCoMo WLAN/WCDMA trial Cellular Wireless Enterprise Home Public Internet Wireless LAN’s

15. Technical Issues Voice/Music streaming/Video streaming (802.11e) Universal coverage (Internet roaming) Range Higher data rates Capacity/Interference) Key constraint: Stay within existing standards/standard evolution (enhance performance within standards and drive standards evolution)

16. Wireless System Enhancements 10 feet100 feet1 mile10 miles 100 kbps 1 Mbps 10 Mbps 100 Mbps 3G Wireless ~ 2GHz BlueTooth 2.4GHz 802.11a 5.5GHz Unlicensed 802.11b 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

17. Enhancements Smart Antennas (keeping within standards): –Range increase –Interference suppression –Capacity increase –Data rate increase using multiple transmit/receive antennas (MIMO) Radio resource management techniques (using cellular techniques in WLANs): –Dynamic packet assignment –Power control –Adaptive coding/modulation/smart antennas Modification of 802.11a/4G (a+) for one cellular/WLAN standard

18. Smart Antennas Smart Antennas significantly improve performance: Higher antenna gain with multipath mitigation (gain of M with M-fold diversity)  Range extension Interference suppression (suppress M-1 interferers)  Quality and capacity improvement With smart antennas at Tx/Rx  MIMO capacity increase(M-fold) SIGNAL INTERFERENCE BEAMFORMER WEIGHTS SIGNAL OUTPUT

19. In 1999, combining at base stations changed from MRC to MMSE for capacity increase 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 in cellular (IS-136)

20. 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 total transmit power (with sufficient multipath) – only an increase in DSP –Indoors – up to 150-fold increase in theory –Outdoors – 8-12-fold increase typical AT&T measurements show 4x bit rates & capacity increase in all mobile & indoor/outdoor environments (4 Tx and 4 Rx antennas) –216 Mbps 802.11a (4X 54 Mbps) –1.5 Mbps EDGE –WCDMA

21. 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

22. DIVERSITY TYPES Spatial: Separation – only ¼ wavelength needed at terminal Polarization: Dual polarization (doubles number of antennas in one location Pattern: Allows even closer than ¼ wavelength  4 or more antennas on a PCMCIA card  16 on a handset  Even more on a laptop

23. 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

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

25. 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) 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

26. 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

27. Radio Resource Management Use cellular radio resource management techniques in WLANs: Adaptive coding/modulation, dynamic packet assignment, power control – Not available on market Current system administrators and users unaware of capacity/coverage issues Performance statistics generated in current WLANs, but interpretation difficult –Techniques: Use software on controller PC for multiple access points to analyze data and control system Power control to permit cell ‘breathing’ (for traffic spikes) Dynamic AP channel assignment –Combination of radio resource management and smart antennas yields greater gains than sum of gains

28. Cell Breathing in WLAN Systems Measure traffic load for each access point Shrink overloaded cell by reducing RF power Expand others to cover abandoned areas AP

29. Adaptive Channel Assignment 31 2 2 3 23 1 1 31 2 2 2 33 3 2 Initial Assignment After one iteration Assign channels to maximize capacity as traffic load changes Cochannel interference High traffic load

30. Standards Evolution 10 feet100 feet1 mile10 miles 100 kbps 1 Mbps 10 Mbps 100 Mbps 3G Wireless ~ 2GHz BlueTooth 2.4GHz 802.11a 5.5GHz Unlicensed 802.11b 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 802.11a+

31. 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 error @5.8GHz:114 kHz - too much for narrower channel spacing, even at 1.9 GHz Issues for 802.11a: 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

32. Coding rate:1/2, 2/3, 3/4 subcarriers: G 230.4  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*16 204.8  s 832=768+64 tones 2048 point FFT Changes for high-mobility operation: FFT size:2048 = 64*32 Symbol duration: 230.4  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 error @5.8GHz:2.9 kHz, 1.9 kHz @ 1.9 GHz Pilot subcarriers:64 = 4*16 BPSKQPSKQAM16QAM64 1.663.336.66 R=1/2 13.33 R=2/3 2.551015 R=3/4 User data rates (Mbps):

33. OFDM tradeoffs 802.11a 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 312.5 kHz fBfB 16.56 MHz f op ~5 GHz 4.98-31.67 Mb/s QPSK, “16QAM,” “64QAM” [1/2, 2/3, 3/4, 5/6, 7/8] + RS(204,88) 1705 231-280  s 7-56  s 4.464 kHz 7.6 MHz ~500 MHz 2.56-8.96 Mb/s QPSK,16QAM 1/2, 2/3, 3/4, 7/8 640 200  s 40  s 6.25 kHz 4 MHz ~2 GHz

34. Conclusions We evolving toward our goal of universal high-speed wireless access, but technical challenges remain These challenges can be overcome by the use of: –Smart antennas to reduce interference, extend range, increase data rate, and improve quality, without standards changes –Radio resource management techniques, in combination with smart antennas – further enhanced by a standards evolution to 4G