Wireless Systems beyond 3G

Wireless IP / BEATS workshop [2003-06-03] 1

Wireless Systems beyond 3G

Erik Dahlman

Expert Radio Access Technologies

Ericsson Research

Not so many answers! Mainly questions and comments!


Air-interfaces beyond 3G

Two paths:– Evolution of 3G air-interface standards– Development of new Broadband Air-interface (”4G”)

What path to follow?What path to follow?

Is there a fundamental difference?Is there a fundamental difference?Sufficiently evolved 3G = ”4G” ?


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 (?)– …


Evolution of 3G Air-interface 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

Why an evolution of 3G standards?Why an evolution of 3G standards?


Evolution of WCDMA (”WCDMA Evolved”)

Rel 4 Rel 5 Rel 7

OFDM ?Enhanced Uplink?

WCDMA EvolvedWCDMA Evolved

MIMO ?

WCDMAWCDMA

Wider Bandwidth

?

... ?... ?

Enhanced Downlink(”HSDPA”)

Similar evolution in 3GPP2 (cdma2000)

HSDPA = High Speed Downlink Packet Access


Fast link adaptation

Channel-dependent scheduling

WCDMA Enhanced Downlink (”HSDPA”)

Basic principle:Basic principle:

Adapt to variations in Adapt to variations in instantaneous instantaneous radio-channel conditions!radio-channel conditions!

Short TTI

2 ms Fast retransmissions with soft combining

+

Higher-ordermodulation

16QAMQPSK

+


What does HSDPA offer?

Improved capacity– 100-200% improvement for ”best-effort” packet data (e.g. web-browsing)– Improved capacity also for streaming services (50%)

Support for very high data rates– Peak data rate 14 Mbps (theoretical)– Actual peak data rate depends on e.g. channel conditions

Significantly reduced delay– Higher data rates– Shorter TTI – Fast retransmissions

• Improved end-user quality• Improved overall efficiency when

interacting with higher-layer protocols


WCDMA Enhanced Uplink

HSDPA is a significant improvement to the WCDMA downlink– Higher downlink capacity– Reduced downlink delay

Need to consider means to enhance/evolve the WCDMA uplink !Need to consider means to enhance/evolve the WCDMA uplink !

Study item in 3GPP

Uplink may be a future bottle-neck– In terms of capacity– In terms of delay (contribution to overall round-trip delay)


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 !NOTE! Higher peak data rates is not a main target !

Techniques/features to be consideredTechniques/features to be considered:– Improved scheduling – Fast Hybrid ARQ with soft combining – Shorter TTI

– Fast ”DCH set-up”


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?


3G Evolution towards Wider Bandwidth

Further evolution of 3G air-interface standardsmay require wider transmission bandwidth

5 MHz

Alternatives

”Super-wideband” CDMA

Multi-carrier WCDMA

WCDMA

Is this still 3G?Is this still 3G?


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)


New Broadband Air-Interface

Research on Advanced Air-interface and Radio-network Technologies


Why a New Broadband Air-interface?

“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”

WWW New Radio

“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!”

Final version:


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 existDo such services exist ? ? They may and one needs to be prepared for it !

Research on New Broadband Air-interface needed Research on New Broadband Air-interface needed !


Requirements on

Future Broadband Air-interfaceas stated within WWI, Japan (NTT DoCoMo), etc.


Data-rate requirements

High ”Maximum Air-interface Data Rate”Maximum Air-interface Data Rate”– Downlink: > 100 Mbps [ >1 Gbps in special scenarios]

– Uplink: ?

High ”Achievable Maximum Data Rate”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 ! with reasonable TX power ! )

Very large maximum transmission bandwidth needed !Very large maximum transmission bandwidth needed !


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?


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


Some ”Important” Technologies


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


Some “Important” Technologies, cont’

Tight “Interlayer” Interaction– Tight interaction between the resource management and

the “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


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.)


Thank you for your attention!

[email protected]

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Wireless Systems beyond 3G