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Wireless Systems beyond 3G

Wireless Systems beyond 3G. Not so many answers! Mainly questions and comments!. Erik Dahlman Expert Radio Access Technologies Ericsson Research. Air-interfaces beyond 3G. Two paths: Evolution of 3G air-interface standards Development of new Broadband Air-interface (”4G”).

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Wireless Systems beyond 3G

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  1. Wireless Systems beyond 3G Not so many answers! Mainly questions and comments! Erik Dahlman Expert Radio Access Technologies Ericsson Research

  2. Air-interfaces beyond 3G • Two paths: • Evolution of 3G air-interface standards • Development of new Broadband Air-interface (”4G”) What path to follow? Is there a fundamental difference? Sufficiently evolved 3G = ”4G” ?

  3. What do we want for the future? • New and/or improved services • Possibility for higher data rates • Possibility for lower delay • ... • Lower cost • Improved capacity and coverage • More efficient spectrum utilization • Reduced deployment effort/cost • Lower-cost equipment (?) • …

  4. Evolution of 3G Air-interface Standards Why an evolution of 3G standards? • To satisfy new and/or changing user requirements • To ensure competitiveness • WCDMA competitive to other 3G technologies (and vice verse) • 3G competitive to alternative technologies

  5. Evolution of WCDMA (”WCDMA Evolved”) Rel 4 Rel 5 Rel 7 4G? WCDMA WCDMA Evolved Enhanced Downlink (”HSDPA”) Enhanced Uplink? OFDM ? MIMO ? Wider Bandwidth ? Similar evolution in 3GPP2 (cdma2000) ... ? ... ? HSDPA = High Speed Downlink Packet Access

  6. Channel-dependent scheduling + QPSK 16QAM Higher-ordermodulation + Fast link adaptation 2 ms Fast retransmissions with soft combining Short TTI WCDMA Enhanced Downlink (”HSDPA”) Basic principle: Adapt to variations in instantaneous radio-channel conditions!

  7. What does HSDPA offer? • Support for very high data rates • Peak data rate 14 Mbps (theoretical) • Actual peak data rate depends on e.g. channel conditions • Improved capacity • 100-200% improvement for ”best-effort” packet data (e.g. web-browsing) • Improved capacity also for streaming services (50%) • Significantly reduced delay • Higher data rates • Shorter TTI • Fast retransmissions • Improved end-user quality • Improved overall efficiency when interacting with higher-layer protocols

  8. WCDMA Enhanced Uplink • HSDPA is a significant improvement to the WCDMA downlink • Higher downlink capacity • Reduced downlink delay • Uplink may be a future bottle-neck • In terms of capacity • In terms of delay (contribution to overall round-trip delay) Need to consider means to enhance/evolve the WCDMA uplink ! Study item in 3GPP

  9. Enhanced Uplink, what are the targets? • Improved uplink capacity • Reduced uplink delay • Improved coverage for high data rates NOTE! Higher peak data rates is not a main target ! • Techniques/features to be considered: • Improved scheduling • Fast Hybrid ARQ with soft combining • Shorter TTI • Fast ”DCH set-up”

  10. MIMO within 3G Evolution • What is MIMO? • Any transmission scheme with multiple TX and RX antennas? • or • Multi-layer schemes (á la BLAST)? • Multi-layer schemes • Clearly interesting for the future • Within the scope of 3G evolution or for future air interface?

  11. 3G Evolution towards Wider Bandwidth Further evolution of 3G air-interface standardsmay require wider transmission bandwidth Alternatives WCDMA ”Super-wideband” CDMA Multi-carrier WCDMA 5 MHz Is this still 3G?

  12. Enhancements ”within” the 3G standards • Carried out in parallel to ”3G evolution” • Continuous work on means to improve 3G systems • New/advanced receiver structures • New/advanced antenna structures • New/advanced radio-network algorithms • etc. etc. • Mainly to improve system performance (capacity & coverage)

  13. New Broadband Air-Interface Research on Advanced Air-interface and Radio-network Technologies

  14. Why a New Broadband Air-interface? WWW New Radio “The need for new radio interface systems with significantly improved capabilities is motivated with the changed expected user behaviour towards the knowledge society to support future societal needs based on sustainable scenarios” Final version: “The need for new radio interface systems with significantly improved capabilities is motivated with changed expected user behaviourthat can not be satisfied with existing and evolving systems!”

  15. Why a New Broadband Air-interface? • To provide new wireless services not possible to providewith 3G evolution • To provide key wireless services much more efficientlycompared to 3G evolution Do such services exist ? They may and one needs to be prepared for it ! Research on New Broadband Air-interface needed !

  16. Requirements on Future Broadband Air-interface as stated within WWI, Japan (NTT DoCoMo), etc.

  17. Data-rate requirements • High ”Maximum Air-interface Data Rate” • Downlink: > 100 Mbps [ >1 Gbps in special scenarios] • Uplink: ? Very large maximum transmission bandwidth needed ! • High ”Achievable Maximum Data Rate” • High data rates in difficult radio environments (e.g. severe time dispersion) • High data rates at high terminal speed • High data rates with wide-area coverage (with reasonable TX power ! )

  18. Some additional requirements • Low delay • High system capacity • What is ”high”? Much better than 3G´? • Improved cell capacity [Mbps/MHz/cell] • Advanced antenna solutions • Efficient operation in small cells • New radio-network structures • How important is this?

  19. Requirement on Spectrum Flexibility • Need for very large maximum transmission bandwidth • Spectrum limitations • Spectrum flexibility needed • Multiple frequency bands • Differently-sized spectrum allocations • Support for multiple transmission bandwidths • Support for different duplex arrangements

  20. Some ”Important” Technologies

  21. Some “Important” Technologies • New” / “Advanced” Transmission Schemes • OFDM / multi-carrier • Advanced receiver structures • etc. etc. • Wideband Radio Technologies • Advanced Antenna Solutions • Multiple antenna elements at network and terminal • Advanced antenna solutions should be an integrated part of a future broadband air-interface

  22. Some “Important” Technologies, cont’ • Tight “Interlayer” Interaction • Tight interaction between the resource management andthe “physical layer” • Fast measurements and control • Exploit the spatial, frequency, and multi-user dimensions • New Radio-network Structures/Topologies • Relaying/multi-hop solutions? • Cellular “MUD” • Other novel approaches

  23. Beyond 3G @ Ericsson • Main focus on 3G evolution • High Speed Downlink Packet Access (“Enhanced Downlink”) • Enhanced Uplink • Further enhancements/evolution of 3G standards • Future Broadband Air-interface • Basic research on advanced air-interface and radio-network technologies • Long-term 3G evolution or “4G”? • WWI, Asian 4G discussions (Japan, China, etc.)

  24. Thank you for your attention! erik.dahlman@eab.ericsson.se

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