Mobile Broadband: Vision & Evolution

1. Mobile Broadband: Vision & Evolution Siavash M. Alamouti, Intel Fellow Chief Technology Officer, Mobile Wireless Group

2. Outline • Intel Vision for Mobile Broadband • Mobile Internet Requirements • Mobile WiMAX Technical Overview • Mobile WiMAX Performance and Comparative Analysis • Evolution of Mobile WiMAX • Areas of Future Research

3. Acknowledgements • Hujun Yin, Intel • Material for overview and Comparative Performance • Pouya Taaghol, Intel • Material for Systems and Network Architecture • Jose Puthenkulam, Intel • Material for Standards Timelines • Shilpa Talwar, Intel • Material for Future Research

4. What is the Killer Application? Anything the Internet can provide today & possibly more need a mobile broadband technology that can meet the requirements of mobile internet

5. Mobile Internet Requirements • Low cost of devices and subscription • Transparency of service • Ubiquity of service • Ubiquity of user experience

6. Transparency: Data Rate Comparison of Wireline & Wireless Technologies Interesting rule of thumb: the actual capacity (Mbps per channel per sector) in a multi-cell environment for most wireless technologies is about 20% to 30% of the peak theoretical data rate.

7. WiMAX: Fixed, Nomadic, Mobile? • Industry has evolved from a vision of Fixed Wireless to Mobile Wireless • WiMAX industry is “aligned” on the vision that Fixed and Nomadic are special cases of Mobile and we need one technology for all to benefit from economies of scale. • IEEE 802.16e is the basis of Mobile WiMAX.

8. Cellular • OFDM Based • New Spectrum • Flexible All-IP Core Mobile Broadband 4G 1G 2G 3G Broadband Wireless 802.16d 802.16e Wireless LAN 802.11a/b/g 802.11n Wireline V.90 ADSL FTTH Mobile Broadband Evolution to 4G

9. Primary Devices for Mobile Broadband? • The gateway to the internet is the PC (desktops, laptops) • The larger the screen, the larger the required bandwidth • Primary devices for mobile internet will be smaller PCs (not larger handsets) • PC-like application processing power (service transparency) • Full Microsoft/MAC/Linux OS support (application transparency) • Always on experience • Leadership for a whole new class of devices (UMPCs) • Small form factor • Good battery life • Low cost

10. Mobile WiMAX Technical Overview

11. Scalability Traffic types, QoS with Service Flows, Advanced Scheduling Framework, Adaptive Modulation & Coding, ARQ, H-ARQ High Data Rates Support for operation in different frequency bands and Channelizations. Flexible frequency planning; Macro, Micro, Pico cell support QoS EAP authentication, Encryption with AES-CCM, CMAC Authentication mode, X.509 Certificates, Key Binding, Device and User authentication capability Secure Optimized Hard Handover, Fast BS Switching Handover, Power Management with Sleep and Idle modes Mobility OFDM to support higher PHY rates, Larger MAC frames with low overhead, Advanced FEC, Adaptive modulation, H-ARQ, MIMO and Beamforming support Security Mobile WiMAX Salient Features

12. Backup? IFFT Key Radio Technology: OFDMA • For large bandwidths TDMA and CDMA suffer from inter-symbol-interference in larger cells • Large bandwidth = small symbol duration • Symbols gets smaller and channel does not change • How to combat frequency selective fading? • parallel orthogonal flat narrowband channels • Orthogonal subcarriers, high spectral efficiency, efficient implementation • Efficient MIMO implementation OFDMA is a cost-effective technology for Mobile Internet

13. Complexity of MIMO-OFDM vs. MIMO-CDMA • Receiver complexity for MIMO-CDMA grows exponentially with bandwidth and linearly for MIMO-OFDM

14. CSMA/CA Efficient for unpredictable traffic in an unlicensed band Inefficient for predictable traffic (voice) “Sharing model” designed for unlicensed band No control of resource allocation policy Cellular Mobile WiMAX WiFi Mobile WiMAX Media Access • Fast dynamic scheduling • Contention access for bandwidth requests only • Resource allocation exclusively by BS – retains tight policy control by network • Efficient for both bursty, unpredictable traffic and voice • Static Allocation (slot or code based) • Efficient for voice traffic • Inefficient for bursty traffic (email, http) Optimal MAC for Mobile Internet

15. Smart Antennas and MIMO

16. Smart Antenna Support 2 Tx / 2 Rx • Space Time Block Coding (STBC) • Reduces fade margin by spatial diversity • Open loop • Peak rate is not increased • Spatial Multiplexing (SM) • Increases peak rate • Open loop • Requires good SINR and low spatial correlation • Adaptive MIMO switch (AMS) • Optimally select STBC or SM to adapt to channel condition • Reduced feedback • Significantly improves capacity • AAS (beamforming) • Improves link budget • Reduce interference • Minor change to client • 4 or more antennas for significant impact 1 Tx / 2 Rx 1 Tx / 2 Rx Minimum Configuration for Mobile WiMAX Wave II

17. MIMO-OFDMA Architecture MIMO operation in frequency domain • Flat subcarriers - hij is scalar • Simple frequency domain one-tap equalizer • Scalable with bandwidth h11 h21 H = h12 h22 Multi-Element Transmitter Multi-Element Receiver h11 h12 IFFT h21 MIMO Encoder MIMO Sub-ch Mapping MIMO Decoder FFT h22 IFFT y = Hs + n

18. DL Adaptive MIMO Switching (AMS) STBC Encoder AMS Channel Encoder Symbol Mapper MCS SM Encoder MIMO mode LA Decision Unit CSI SNR MCS: Modulation and Coding Scheme LA: Link Adaptation CSI: Channel State Information SNR: Signal-to-Noise Ratio

19. ~2 dB ~1 dB Performance of AMS Spectral efficiency (SE) AMS overcomes the deficiencies of STBC and SM and leads to spectral efficiency very close to the ideal one at both low and high SNR regions

20. Sub-carrier Time P1 P1 P2 MS1 MS2 P2 Up Link Collaborative MIMO • MSs spatially uncorrelated • no 3dB power penalty

21. System Architecture

22. Mobile WiMAX Network Flat & Very-Flat Architectures Flat Architecture ASN CSN ASN GW BS R6 R3 R8 Policy Server HLR HSS MIP HA R1 DHCP AAA R6 BS R3 R5 (Roaming) R4 R1 ASN Another Operator’s CSN MS Policy Server Very Flat Architecture HLR HSS MIP HA DHCP AAA NSP (Network Service Provider) NAP (Network Access Provider) Mobile WiMAX networks offer co-existence & interoperability of Flat and Very-Flat solutions

23. Backup? Application IP IP MIP (PMIP) MIP 802.16 MAC 802.16 MAC L2 L2 L1 802.16 Phy L1 802.16 Phy MS ASN CSN R1 IP R3 3G User Plane and Data Flow Comparison of User Planes & Data Flows too many protocols, too many nodes Mobile WiMAX User Plane and Data Flow Simple. Few protocols. Easy-to-implement. Mostly, IETF protocols. Few MS requirements

24. WLAN Access IWK WiMAX ASN WiMAX CSN Policy Server Mobility Anchor Auth Server Billing Mobile Device Provisioning System 3GPP Access (GSM, UMTS, HSPA, LTE) 3GPP SAE Core PCRF SAE GW HSS OCS MME/UPE Mobile WiMAX- 3GPP SAE Interworking All-IP Core Network BS & Radio Functions PDN IMS Internet SAE integrates WiMAX to operator’s core network as other 3GPP access technologies are with seamless vertical mobility

25. Mobile WiMAX Comparative Performance

26. Simulation methodology and assumptions • Methodology based on CDMA2000 methodology specified by 3GPP2, now also adopted by 3GPP • Channel models exhibit lesser delay spread than realistic broadband channels and will hence benefit the other technologies and soften the performance advantage of WiMAX • Only standards-based features are included. Simulation results do not include: • Adaptive Antenna Systems (AAS) • Interference cancellation or mitigation (at BS or MS) • Novel receiver designs • Novel frequency/space scheduling (very simple scheduler) • Compared technologies’ performance are based on two receivers in MS and BS with known receiver combining techniques

27. WiMAX, EVDO and HSPA Features [1]

28. System Configuration

29. Channel Models with Relatively Smaller Delay Spread (according to EV-DV Methodology)

30. WiMAX, HSPA and EVDO Comparison • 1Tx 2Rx Rake receiver for EVDO and HSPA • 2x2 Adaptive MIMO for WiMAX DL • 1x2 Collaborative MIMO for WiMAX UL

31. Mobile WiMAX, HSPA and EVDO Comparison results do not include possible improvements with AAS or interference canceling receivers

32. Beyond Access Opportunity • Old Model: Walled Garden • Advantage: complete control • Disadvantage: few applications, no leveraging of creative Internet application • Broadband Model: Open Internet (Dumb Pipe) • Advantage: access to all applications over the internet • Disadvantage: operator revenues limited to access • Mobile WiMAX Model: Smart Pipe • Mobile operators partner with content and application providers to deliver enhanced mobile services • Advantage: user transparent quality access to Internet applications, opportunity for shared revenue on contents • Win-Win

33. 802.16 Evolution Vision IEEE 802.16 Standards WiMAX Forum Profiles Networks Targeted TDD Solution for Sprint, Clearwire, KT… 802.16e + Corrigendum2 Mobile WiMAX System Profile Release 1 (R1) (2006) 802.16REV Mobile WiMAX System Profile Release 1.x (R1.x) (2007) FDD Solution (for FDD Spectrum) ? 802.16m Mobile WiMAX System Profile Release 2 (R2) (2008) Global TDD & FDD Europe, etc. • IEEE 802.16m PAR Approved Dec ‘06; Work Starts Jan ‘07; Completion expected Q2 ’08 • IEEE 802.16 REV PAR starts Jan ’07 and Work Starts May’07; Completion Q4,’07 • Mobile WiMAX R2 will be fully backward compatible with R1. • Harmonized spectrum for IMT-2000 and IMT-Advanced available for Mobile WiMAX • Mobile WiMAX R1 already competitive with 3GPP LTE and 3GPP2 AIE • Mobile WiMAX R2 expected to deliver superior performance to 3GPP-LTE and 3GPP2 AIE • Strong support of 802.16e/WiMAX community for 802.16m

34. 802.16m Candidate Requirements Competitive Comparison

35. Areas of Future Research

36. How to Increase System Capacity? • Can we go higher in frequency? • As frequency increases, the line-of-sight range: • decreases with frequency if both antenna’s dimensions are scaled with wavelength • remains constant if one of the antenna’s physical dimensions is held fixed • increases with frequency if both antenna’s physical dimensions are held fixed • Capacity increases: • linearly with RF bandwidth • as logarithm of signal to noise plus interference ratio • linearly with number of independent spatial channels (cells, sectors, MIMO channels,…) antenna gain aperture size (m2) Frequency (Hz) smaller cells, larger bandwidths, higher order MIMO, and interference management Speed of light (m/sec)

37. System Capacity Metric • A meaningful metric is needed to study capacity of scaleable systems • ArealCapacity = Sum information rate of users in a cell, normalized by cell area & bandwidth • The metric provides insight into means for increasing capacity • Increase single-link capacity between client & BS (Rk) • Increase multi-link Cell capacitybetween clients in a cell & BS • Decrease Cell area, which is a standard cellular approach Cell Capacity

38. Transmission Interference Interference Limits Capacity Growth In-Cell interference: 2 devices attempt to access BS simultaneously Out-Cell interference: interference from clients in neighboring cells

39. Interference: a theoretical perspective • Cell capacity with N users in a cell is no more than a constant due to in-cell and out-cell interference • Single cell medium-access methods (TDM, FDM) improve capacity, but still bounded by constant • Multi-cell multi-user co-operative techniques promise to eliminate interference by treating it as useful information, and approach SNR limited capacity. Users add a new dimension to capacity improvement

40. Key Cooperative Technologies for 4G NETWORK LAYER Interference co-ordination Intelligent Relays Channel-aware routing Network coding PHYSICAL LAYER Interference cancellation Multi-user MIMOSuperposition coding MAC LAYER Fast link adaptationTraffic-aware scheduling Multi-cell scheduling