Department of Electrical and Information Technology

3G Evolution

Chapter:8WCDMA 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 – improvedUplink packet-data support - Reduced delays - 5.74 Mbps peak data rate - ~2xR99 capacity

- MBMS – Multimedia broadcastMulticast 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 one 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 of 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