Analysis and Comparison of 3G Technologies.ppt

7/22/2019 Analysis and Comparison of 3G Technologies.ppt

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Wireless Curriculum Development Section

ISSUE

1

Analysis and Comparison of 3G Technologies

1.0


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2Confidential Information of Huawei.

No Spreading without Permission. Security Level: Internal

Course Contents

Chapter 1 WCDMA Technology Features

Chapter 2 cdma2000 Technology Features

Chapter 3 TD-SCDMA Technology Features

Chapter 4 Technologies Comparison


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WCDMA Network Features


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WCDMA Technical Features

Modulation mode: QPSK (uplink), QPSK (downlink)

Voice coding: AMR

Channel coding: Convolutional code and Turbo code

Demodulation mode: Pilot-assisted coherence

demodulation

Transmit diversity mode: TSTD, STTD, and FBTD

Power control: Uplink/downlink closed loop control

and outer-loop power control

BTS synchronization mode: Supportsynchronous/asynchronous BTS operation

Signal bandwidth: 5 MHz Chip rate: 3.84 Mcps


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Course Contents






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cdma2000 RTT Features


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Technical Features of cdma2000 1X

IS-95A/B is a subset of cdma2000.

Chip rate: 1.2288 Mcps

Spread-spectrum modulation: QPSK (forward), HPSK (reverse)

Reverse pilot and coherence demodulation

Fast forward and reverse quick power control

Forward transmit diversity: OTD and STSAddition of Turbo code for channel coding

Variable frame length: 5ms, 10ms, 20ms, 40ms, 80ms

Support F-QPCH and extend the standby time of the mobile station

Maximum speed of 307.2 kbps

Support QoS negotiation Support multi-media services

Support 8K/13K QCELP 8 kbps EVRC

The channel capacity is twice of the IS-95A/B


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Technical Features of cdma2000 3X

0 1MHz 2 MHz 3 MHz 4 MHz 5 MHz

0 1MHz 2 MHz 3 MHz 4 MHz 5 MHz

1.25 MHz

Forward

Link

Reverse

Link

0 1MHz 2 MHz

0 1MHz 2 MHz

1.25 MHz

Forward

Link

Reverse

Link

Chip rate: 3*1.2288 McpsPeak access rate: 2Mbps


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Evolution to cdma2000

1 IS-95A/B carrier cdma2000 1Xcarrier

cdma2000 is compatible with the IS-95A/B.

SCH is added to support the packet services.IS-95A/B can be evolved into cdma2000 by adding cdma2000 1X BSC

and cdma2000 BTS. That is, the services can be evolved smoothly by

adding relevant equipment.

1 IS-95A/Bcarrier

+ 2 cdma2000 1Xcarriers


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Course Contents






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TD-SCDMA Network Features

The CN is evolved from the GSM/GPRS network and is compatible with the

GSM/GPRS network.

The CN can be based on TDM, ATM, and IP technologies and evolved into a

total-IP network.

Logically, the CN is divided into CS and PS, which respectively complete

the circuit-switched services and packet-switched services.

The ATM-based UTRAN can process the voice and packet services and be

evolved into an IP network.

The MAP and GPRS tunneling technologies are the core of the mobility

management mechanism in the WCDMA technology.

The TD-SCDMA system will adopt the CN structure of the WCDMA

system.


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Technical features of TD-SCDMA Technology

TD-SCDMA is proposed by the CWTS. It is the first time that the

Chinastelecommunication standards are accepted by the ITU.

Smart antenna + Combined detection

Multi-slot CDMA + DS-CDMA

SynchronousCDMA

Channel coding/decoding + interleaving

(same as 3GPP) Relay handoff

Smart Antenna

Synchronous CDMA

Software Radio

Main features of TD-SCDMA Key technologies of TD-SCDMA


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Course Contents






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Comparison between Three 3G Technologies

WCDMA cdma2000 TD-SCDMA

Receiver structure Rake Rake Rake

Support closed-loop

power control

Yes Yes Yes

handoffSoft handoff and

hard handoff

Soft handoff and

hard handoff

Relay handoff

Demodulation modeCoherence

demodulation

Coherence

demodulation

Coherence

demodulation

Chip rate (Mcps) 3..8 N*1228 1.2

Transmit diversity

mode

TST, STT, and FBT OT and ST None

Synchronization mode Asynchronous Synchronous Synchronous

Core network GSM ANSI-41 GSM


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Advantages of TD-SCDMA System

TD-SCDMA system improves the spectrum efficiency. Paired band is not

required and allocation of bands is more simple. In contrast, the FDD of the

WCDMA system requires paired bands.

TD-SCDMA system is suitable for asymmetrical services such as Internet,

multimedia applications, and file transfer service, because the

uplink/downlink resources can be allocated flexibly. In contrast, the WCDMA

system wastes an uplink band.

The uplink and downlink are correlated. They work at the same band. Thus,

the symmetry features of band allows the introduction of new technologies

such as the smart antenna to improve the performance and reduce the cost.

In contrast, the uplink and downlink work at different bands in the WCDMA

and thus are not correlated.

The investment on the TDD equipment is low. As the channel are correlated,

the receiver can be simplified. It sets no requirements on the TX and RX

isolations and thus the monolithic IC can be used in the RF transceiver.


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Disadvantages of TD-SCDMA System

Synchronization between BTSs: To reduce the interference between BTSs,

synchronization between BTSs is required.

Interference: Synchronization is very important in the telecommunications

system. The TDD system is itself a synchronous system and sets strict

requirements on the synchronization. In addition, the fact that the uplink

and downlink operate at the same band adds more interferences to the

system.

Coverage area: The coverage area of the TD-SCDMA system is smaller

than that of the WCDMA system.

Travel speed: ITU-R requires the TDD to support a maximum travel speed

of 120 km/h. However, the FDD system can support a maximum travel

speed of 500km/h.

Transmit power: TD-SCDMA requires a large instantaneous transmit power

due to the pulse power interference just like that of TDMA. This problem

does not occur to the FDD system, because the power is transmitted on all

slots in the FDD system.


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Analysis of Key Technologies (1)

WCDMA cdma2000

Channelbandwidth/Chiprate

5MHz/3.84Mcps

The multipath recognition accuracy is

three times of that of cdma2000

The air-interface anti-fading capability is

improved.

Compared with the chip rate of 1.2288

Mcps, the capacity of WCDMA can

increase by 10% in high-speed

movement.

1.25MHz/1.2288Mcps

The number of detached multipaths is

less than that of WCDMA. However,

the band planning and request

become flexible.

cdma2000 can also offer the voice

and data bearer services. However,

twice more RF components are

needed compared with the WCDMA.


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Voice

coding/decoding

Provide AMR voice services

at eight rates

Provide up to 12.2 kbps voice

service when the system load

is not heavy.

Dynamically change the AMR

rate when the system load isheavy. The rate can be lowed

to 4.75 kbps to serve more

subscribers.

Allow operators to

dynamically adjust the

capacity and QoS of thenetwork

Provide two variable rate

coding schemes:

8Kbps(EVRC) and

13Kbps(QCELP)

Not dynamically selected

by the network

Generally EVRC is

employed


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WCDMA cdma2000

Powercontrol

1500Hz fast power control for inner

loop

Offer better anti-fadingperformance and optimized

communication quality

Increase capacity and coveragearea

800Hz fast power control for inner

loop

Syn.

Asynchronous orsynchronous

(optional)

Independent from the GPS andfacilitate the BTS networking

The handset consumes 13% morepower in the asynchronous mode.

Synchronous (GPS)

Simplify the handoff andcell-searching processes


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WCDMA cdma2000

Handoff

Soft handoff /Softer handoff/Inter-frequency handoff/GSM-WCDMA handoff

Introduce compressed mode and do

not interrupt the connection during the

measurement of foreign frequency or

system.

Reduce the call-drop rate of the

system.

Soft handoff/Softer handoff/Inter-frequencyhandoff/IS-95-cdma2000 handoff

Interrupt the communication with the

source carrier and then synchronize and

measure on the new carrier.

The voice quality is not steady. Call-drop

may occur.



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Transmitdiversity

technology

Support open-loop TX diversity

(including TSTD and STTD)

and closed-loop TX diversity

More adaptable to the wireless

channel environment

Supported by the terminals

In the case of low-speed

movement, the closed-loop TX

diversity provides higher

diversity gain and thus

improves the system downlink

capacity and coverage area.

Support open-loop TX diversity

(including OTD and STS)

Not supported by terminals at

present


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Compared with dual-antenna RX/TX diversity, the 4-antenna multi-

beam handoff can double the system capacity and increase the

coverage area by 50%.

Employment of smart antenna in constructing a mobile network can

save 27%cost per subscriber.

Key technologies supportingthe smart antenna

WCDMA cdma2000

Multi-beam switchingtechnology

Implemented in the whole coveragearea

Implemented in some hot spots

Self-adaptive antenna arraytechnology

Dedicated pilot is defined in thestandards. Thus, the implementation ofthis technology is easy.

Downlink dedicated pilot is not defined.Thus, the implementation of thistechnology is difficult.

WCDMA standard can better support the smart antenna technology.

Analysis of Smart Antenna

Smart antenna is one of the key enhanced technologies in

the 3G system.


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Analysis and Comparison of 3G Technologies.ppt

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