Chapter: 8 WCDMA evolution: HSPA and MBMS Isael Diaz - - PowerPoint PPT Presentation

Department of Electrical and Information Technology

3G Evolution

Chapter:8

WCDMA evolution: HSPA and MBMS

02-Apr-2009 3G Evolution - HSPA and LTE for Mobile Broadband 1

Isael Diaz isael.diaz@eit.lth.se

02-Apr-2009 3G Evolution - HSPA and LTE for Mobile Broadband 2

Outline

• Evolution
• HSPA and MBMS
• Multiple Access
• Direct Sequence Spread Spectrum
• Network Architecture
• Protocol Architecture
• Physical Layer
• Channelization Codes
• Asynchronous Operation
• Power Control
• Soft handover
• Packet Data Session

WCDMA: Evolution

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HSDPA -improved downlink packet-data support

• Reduced delays
• 14Mbits/s peak data rate

~3xR99 capacity Enhanced uplink – improved Uplink packet-data support

• Reduced delays
• 5.74 Mbps peak data rate
• ~2xR99 capacity
• MBMS – Multimedia broadcast

Multicast Services

• Introduction of improved

broadcast servicios ('Mobile TV')

• MIMO and higher-order modulation
• 28 Mbps DL peak data rate
• 11 Mbps UL peak data rate
• Continuous Packet Connectivity
• 'Always on' user experience

*Image inspired “3G evolution HSPA and LTE Mobile Broadband”

WCDMA: HSPA and MBMS

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• HSPA (More details in

further chapters)

– Evolution of WCDMA – 14Mbps in DL – 5.8Mbps in UL

• MBMS (Further

explanation in Chapter 12)

– Enables broadcasting services such as TV, radio, traffic reports, etc.

WCDMA: Multiple Access

• CDMA

– Multiple users share physical medium in time and frequency – Based on interference robustness – All user have same carrier frequency – Each user has a unique code – Benefits from multi path environment

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*Image courtesy of Ericsson AB

WCDMA: DS-SS

• Direct Sequence Spread Spectrum

– Same carrier frequency – Looks like noise if correct spreading code is not used – To recover the transmitter signal the receiver needs the spreading code

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*Image courtesy of Ericsson AB

WCDMA: Network Architecture

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• An UE communicates with
• ne or more NodeBs
• NodeB is responsible for

– FEC – Modulation – Spreading

• RNC in charge of

– Control of one or more NodeBs – Charge of call set up – QoS – Radio resources (ARQ)

*Image inspired “3G evolution HSPA and LTE Mobile Broadband”

WCDMA: Protocol Architecture

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• PDCP

– Performs header compression

• RLC

– IP packet segmentation – ARQ protocol

• MAC

– Interfaces logical channels and transport channels

• PHY

– Coding, spreading, modulation, etc.

*Image inspired “3G evolution HSPA and LTE Mobile Broadband”

WCDMA: Physical Layer

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• 3.84Mchip/s
• Turbo coder 1/3
• QPSK for DL
• BPSK for UL
• Every specific spreading

codes corresponds to a each physical channel

• CPICH reference channel

for DL

*Image inspired “3G evolution HSPA and LTE Mobile Broadband”

WCDMA: Channelization Codes (OVSF)

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• Mutual orthogonality
• OVSF must be selected from different branches
• Different OVSF provide different spreading factors
• Different Spreading factors provide different data-rates
• Spreading factor is selected by the MAC layer
• Some channelization codes are pre-allocated (CPICH, cell

specific information, etc)

*Image inspired “3G evolution HSPA and LTE Mobile Broadband”

WCDMA: Asynchronous Operation

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• WCDMA does not require inter-base station synchronization

(no GPS dependency)

• Advantage

– Reduced deployment efforts

• Drawback

– BS interference to other BS – More challenging cell-search procedure – Complicated handover implementation

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WCDMA: Power control

• Formally named fast

closed/closed loop power control

• Attempts to avoid the

near-far problem by: – measuring the UE signal 1500 times/sec – Regulating the transmission power

• f both UE and BS

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WCDMA: Soft handover

• The UE communicates

with multiple cells simultaneously (active set)

– The RNC determines based on measurements which cells are part of the active set – Provides diversity against fast fading in both DL and UL – Typically a rake receiver is used – “Or of the downs” ensures that average power is kept low

*Image is courtesy of Ericsson AB

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WCDMA: Packet Data Session

• UE: Cell search

(connection request)

• RNC: Channelization

codes available

• RNC: Interference level
• RNC Connection

established

• Transmission power

varies according to traffic pattern

*Image inspired Ove Edfors, lecture on WCDMA

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WCDMA: Summary

• HSPA is the evolution of WCDMA
• Spread Spectrum
• A major milestone in mobile telecommunication
• Flexible radio interface
• Transmission power dependent on traffic pattern
• Sensitive to inter-cell interference
• Sensitive to near-far problem

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• Thank you for your attention