Channelisation Codes (2) - University of Hong Kongsdma/elec6040_2008/Part 6-3G systems-2.pdf · Main differences between 2G and 3G. ... – base transceiver station ... – compared

ELEC6040, Mobile Radio Communications, Dept. of E.E.E., HKUp. 51

Scram. #0 +Chan. #0

Scram. #0 +Chan. #1

Scram. #1 +Chan. #0

R.Scram. #0 +Chan. #0

R.Scram. #0 +Chan. #1

R.Scram. #1 +Chan. #0 R.Scram. #1

+Chan. #1

Channelisation Codes (2)


No, Does not affect transmission bandwidth

Yes, increases transmission bandwidthSpreading

Long 10ms code: Gold codeShort code: Extended S(2) code family

OVSFCode Family

Uplink: several millionsDownlink: 512

Number of codes under one scrambling code=spreading factor

Number of Codes

Uplink: (1) 10ms=38,400chips or (2) 66.7µs=256 chipsOption (2) can be used with advanced base station receiversDownlink: 10ms=38400 chips

4-256 chips (1.0-66.7µs)Downlink also 512 chips

Length

Uplink: Separation of terminalDownlink: Separation of sectors or cells

Uplink: Separation of DPDCH and DPCCH from the same terminalDownlink: Separation of downlink connections to different users in one cell

Usage

Scrambling CodeChannelisation Code

Channelisation Codes (3)


Transmit Diversity (1)WCDMA system: performance degraded by multipath channels– use several transmit antennas at the BS (transmit diversity) to improve the downlink

transmission performance– using multiple antennas at a MS: increase the complexity, not preferred

Two categories of transmit diversity– open loop mode: space time transmit diversity (STTD) (space time code: Alamouti

code)


Transmit Diversity (2)Transmit diversity via space time coding– Alamouti scheme: simple but ingenious– channel information is not required at transmitter side!!!– two transmit antennas systems

Tx Rx

1s

2s

1 1 1 2 2 1y h s h s n= + +*2s

*1s−

* *2 1 2 2 1 2y h s h s n= − +

1 111 2* ** *2 1 22 2

effH

y nsh hY

h h sy n⎡ ⎤ ⎡ ⎤⎡ ⎤⎡ ⎤

= = +⎢ ⎥ ⎢ ⎥⎢ ⎥⎢ ⎥−⎣ ⎦ ⎣ ⎦⎣ ⎦ ⎣ ⎦

h1

h2

{ } { } { }2 2 21 2

1 12 2 sigE s E s E s P= = =


Transmit Diversity (3)Alamouti scheme– SNR at receive side

1 111 2* ** *2 1 22 2

effH

y nsh hY

h h sy n⎡ ⎤ ⎡ ⎤⎡ ⎤⎡ ⎤

= = +⎢ ⎥ ⎢ ⎥⎢ ⎥⎢ ⎥−⎣ ⎦ ⎣ ⎦⎣ ⎦ ⎣ ⎦

11 2* * *2 1 2

HHeff

yh hZ H Y

h h y⎡ ⎤⎡ ⎤

= = ⎢ ⎥⎢ ⎥−⎣ ⎦ ⎣ ⎦

( )2 2

* * * *2 21 2 1 1 1 2 2 1 1 1 2 2

1 22 2 * * * *2 22 1 1 2 2 1 1 21 2

0

0

h h s h n h n s h n h nh h

s sh n h n h n h nh h

⎡ ⎤+ ⎡ ⎤ ⎡ ⎤+ +⎡ ⎤ ⎡ ⎤⎢ ⎥= + = + +⎢ ⎥ ⎢ ⎥⎢ ⎥ ⎢ ⎥⎢ ⎥ − −⎢ ⎥ ⎢ ⎥⎣ ⎦ ⎣ ⎦⎣ ⎦ ⎣ ⎦+⎢ ⎥⎣ ⎦

* *111 21 2 1 2

* ** * *2 1 22 1 2 1 2

nsh hh h h hh h sh h h h n

⎡ ⎤⎡ ⎤ ⎡ ⎤⎡ ⎤⎡ ⎤= + ⎢ ⎥⎢ ⎥ ⎢ ⎥⎢ ⎥⎢ ⎥−− −⎣ ⎦ ⎣ ⎦⎣ ⎦ ⎣ ⎦ ⎣ ⎦

Matched Filter

useful signal

noise

( ){ }

( )( )

( )2 22 2 2 2 2 2

1 2 1 1 2 1 2

22 2 2 2* *1 21 1 2 2

12SNR at receiver: SNR=

2

sig sigE h h s h h P h h P

h hE h n h n σσ

⎧ ⎫+⎨ ⎬ + ⋅ + ⋅⎩ ⎭ = =++

useful signal noise


Transmit Diversity (4)Two categories of transmit diversity (con't)– close loop mode: based on the feedback information (FBI) sent via uplink

DPCCH

DPDCHDPCH

ΣCPICH1

ΣCPICH2

Determine FBI message from

Uplink DPCCH

Weight generation

w1

w2

Rx

Rx

Tx

Tx

Ant1

Ant2

w1 w2

Spread/scramble


Transmit Diversity (5)Transmit diversity: close-loop

Tx Rx

h1p

h2ph1 h2

channel information: h1~h2

( )2 21 2 Hr h s h s n= + +

*1 Hh s

*2 Hh s

( ){ }

( )

22 21 2

2

2 21 2

2

HSNR at receiver: SNR=

sig

E h h s

E n

h h P

σ

⎧ ⎫+⎨ ⎬⎩ ⎭

+ ⋅=

2 21 2H h h= +


Transmit Diversity (6)Performance comparison– two transmit antennas, BPSK modulation– identical independent distributed (i.i.d.) Rayleigh fading channel

( )2 21 2

alamouti 2SNR =2

sigh h P

σ

+ ⋅

( )2 21 2

tran_MRC 2SNRsigh h P

σ

+ ⋅=


Handover (1)

Intra-mode handover– FDD mode– relies on the Ec/N0 measurement performed on the common pilot channel (CPICH)– can be soft handover, softer handover or hard handover– soft handover needs relative timing information between the cells. BSs in WCDMA

is asynchronous; timing adjustment is needed to carry out coherent combining in the Rake receiver in soft handover

Inter-mode handover– Dual-mode FDD-TDD terminals operating in FDD handover to the TDD mode

Inter-system handover– Handover between UTRA (WCDMA) and GSM systems, UTRA (WCDMA) and

Multi-carrier CDMA systems


Handover (2)SSDT (site selection diversity transmit power control)– is a macro diversity method in soft handover mode

Benefits of SSDT– only one BS is transmitting signals to the MS=>reduce the interference caused by

multiple transmissions in a soft handover mode– when multiple BSs transmit to the same signals to the MS, a number of Rake fingers

are needed; if only one BS is considered, less fingers are needed– no power imbalance problem due to power control command reception error

Old BS

New BS

• Soft Handoff

New BS

1. The MS selects one of the cells from its active set to be primary and others non-primary2. Each cell is assigned a temporary identification (ID). MS periodically informs a primary cell ID to the connecting cells3. The non-primary cells switch off the transmission power


Power Control

Fast closed loop power control (inner loop power control)– one command per slot (1500Hz) (IS-95: 800Hz)– basic power adjustment step size: 1dB– applied to both uplink and downlink

Open loop power control– applied only prior to initiating the transmission on the RACH or CPCH (uplink)– adjust the transmit power on uplink based on the measurement on downlink– not very accurate: variation in the component properties, impact of environment,

different frequencies– in IS-95, being active in parallel with close loop power control, allow corner effects

or other sudden environmental changes to be recovered in UTRA (WCDMA), not needed to be operated simultaneously with fast closed loop power control


Link Parameters for WCDMA (1)Copied from T. Ojanpera and R. Prasad, WCDMA: Towards IP Mobility ...


Link Parameters for WCDMA (2)Copied from T. Ojanpera and R. Prasad, WCDMA: Towards IP Mobility ...

(downlink)(1.5kHz)


Summary - WCDMA vs. GSM Air Interface


Summary - WCDMA vs. IS-95 Air Interface


Main differences between 2G and 3G.Key system parameters of WCDMA: 5MHz bandwidth, 3.84Mcps, data rate: 144Kbps to 2Mbps; two duplex modes: FDD and TDD. System architecture of WCDMA: compared to that of GSM and GPRSUplink and downlink: spreading factor, modulation, detection, variable data ratesDesign criteria of UE in WCDMA. In uplink, why are DPCCH and DPDCH complex scrambled?Uplink and downlink: the multiplexing methods of DPCCH and DPDCH and the reasonSpreading and scrambling. In uplink, when to use long and short scramblingcodes, respectively? Diff. between channelisation codes and scrambling codesTransmit diversity: open loop (Space Time Coding) and close loopHandoff and power control: similar to IS95.

Summary of WCDMA


CDMA2000


IntroductionCDMA2000 (standardized by 3GPP2)– based on IS-95 (or cdmaONE), backward compatible with IS-95

Two phases– CDMA2000 1XRTT: using 1.25MHz, provide higher data rates– CDMA2000 3XRTT: using multiples of 1.25MHz, options of multicarrier

transmission or direct sequence spreading

MuticarrierCDMA

5MHz

1.25MHz 1.25MHz

f

Single carrier DS-CDMA

5MHz

BW

fG G


System Architecture

New functional elements for packet

data service


Network Elements (1)Mobile Station (MS)– all functionalities of IS-95 terminals + additional features and capabilities to support

new packet data services + enhanced signaling messagesBase Station (BS)– base transceiver station (BTS) + base station controller (BSC)– compared to IS-95: similar basic functionalities, significant hardware and software

changes to provide multimedia servicesPacket Control Function (PCF)– belongs to radio access network– manages the buffering and relay of packet between the BS and the PDSN

Packet Data Service Node (PDSN)– acting as a foreign agent (FA), providing routing services– managing the radio-packet (R-P) interface and PPP sessions for mobile users– Initiating authentication, authorization and accounting for the mobile user to the

AAA server and receiving service parameters for the mobile user from the AAA server


Network Elements (2)

Home Agent (HA)– mobile IP registration– packet forwarding

Authentication, Authorization and Accounting (AAA)– authentication: user and device identity verification for network access and user-

based QoS requests, authentication to establish dynamic security associations between network entities

– authorization: has access to subscribers profiles, the device register and the operator's policy repository; decides whether a user or device is authorized for a particular service with a specific QoS

– accounting: collecting and storing the billing-related data concerning the offered services, their associated QoS and the multimedia resources requested and used y individual subscribers


Forward Channels

Common channels

Pilot channels: Pilot Channel (F-PICH)Transmit Diversity Pilot Channel (F-TDPICH)Auxiliary Pilot Channel (F-APICH)Auxiliary Transmit Diversity Channel (F-ATDPICH)

Synchronization Channel (F-SYNCH)Broadcast channel: Broadcast Control Channel (F-BCCH)Paging channels: Paging Channel (F-PCH)

Quick Paging Channel (F-QPCH)Control channels: Packet Data Control Channel (F-PDCCH)

Common Assignment Channel (F-CACH)Common Power Control Channel (F-CPCCH)Common Control Channel (F-CCCH)

Dedicated channels

Fundamental Channel (F-FCH)Supplemental Channel (F-SCH)Dedicated Control Channel (F-DCCH)Auxiliary Pilot Channel (F-APICH)

Trafficchannels

Sharedchannel Packet Data Channel (F-PDCH) Traffic

channel

Radio Interface - Physical Layer


Forward Channels (1)Common Channels: carry information directed to one or more MSDedicated Channels: assigned to one and only one MS


Forward Channels (2)

F-PDCH– the only shared channel– similar to a dedicated channel in many physical characteristics, only a single MS

decodes this channel at a time– assigned to a MS by Layer 2 signaling, short assignment: 1.25, 2.5 or 5ms

F-FCH and F-SCH: user data

F-PDCCH: signaling support for F-PDCHF-CACH and F-CPCCH: support a

form of reverse link access procedure(reservation access mode)

F-DCCH: control + user data

F-PDCH: bursty data, high speed, non-real time

Traffic CH

Control CH


Forward Channels (3)Functional Construction– Modulation, coding and spreading (MCS) characteristics of physical channels vary

greatly as the standard evolved– In case of traffic channels, the fundamental functional building blocks are common

to all channelsFunctional Block Diagram for Forward Traffic Channels

Block encoder

Conv. orTurbo

encoder

Symbol repetition or puncturing

Interleaver

Modulator Orthogonal spreading

Quadraturespreading Filter

source bits

long code

Scrambling

cos(2πfct)

sin(2πfct)

s(t)

CRC: Error detection Rate matching

PNI PNQ


Functional Blocks (1)Forward link data scrambling– provides privacy of communication: scrambling sequences unique among users– uses a long PN sequence, maximum length linear shift sequences (MLLSRS),

sequence period 242-1– applies a user-specific (for dedicated channels) or code channel-specific (for

common channels) mask to get a unique sequence– the masking process effectively shifts the MLLSRS, resulting in a unique long PN

sequence

user-specific or code channel-specific


Functional Blocks (2)Forward link modulation– forward link: strong common pilot signal, higher order modulation

BPSKF-SYNCH

un-modulatedF-PICH

QPSKAll Others

adaptive modulation with QPSK, 8PSK, 16QAMF-PDCH

BPSKF-PCH

Modulation schemeForward link channel

known pilot symbols

important, low BER

to provide higher data rate when channel is good


Functional Blocks (3)

QPSK vs. BPSK– Advantages of QPSK: higher bandwidth efficiency, increase coding gain


Functional Blocks (4)QPSK vs. BPSK (cont'd)– Disadvantages of QPSK: more sensitive to inaccurate carrier-phase recovery, larger

SINR degradation– Advantages of BPSK: less sensitive to inaccurate carrier-phase recovery, smaller

SINR degradation

– Forward link: carrier phase estimated by higher powered F-PICH, resulting in small phase error => QPSK is better than BPSK

carrier phaseerror

decisionerror

carrier phaseerror

correctdecision

QPSK BPSK


Functional Blocks (5)Forward link orthogonal spreading– orthogonal code: Walsh code– spreading factor: 4~128, exceptions: F-APICH and F-ATDPICH: 512– achieves bandwidth expansion

– at most 61 length-64 Walsh codes for traffic transmission

Source: V. K. Garg, IS-95 CDMA and cdma2000


Functional Blocks (6)Forward link quadrature spreading (complex spreading)– Purpose: separate different BSs and reduce multipath interference– a pair of short PN sequences (215) are used: one for I branch and one for Q branch

PNI(x)=x15+x13+x9+x8+x7+x5+1PNQ(x)=x15+x12+x11+x10+x6+x5+x4+x3+1

– all BSs use identical short PN sequences but distinct transmission timing offsets

82ELEC6040, Mobile Radio Communications, Dept. of E.E.E., HKUp. 82

Input power

Out

put p

ower

Operationpoint

Peak

Back-off

AveragePeak

time

Why is complex spreading necessary?

Peak-to-average ratio

The power amplifier can be used more efficiently by reducing the peak-to-average ratio, resulting in reducing the power consumption of power amplifier


( )kk tE φω +0cos

( )kk tE φω +− 0sin

)(, nCg kPk ⋅

)()( , nCmjD kDk ⋅

)()( njSnS QI +

( )tSk

)(th

)(th

)Re(⋅

)Im(⋅complex spreading

It can reduce the signal envelope variation, due to the correlation of Re(.) and Im(.)

Transmitter Model of Complex Spreading


( )kk tE φω +0cos

( )kk tE φω +− 0sin

)(, nCg kPk ⋅

)()( , nCmD kDk ⋅

)(nSI( )tSk

)(th

)(th

)(nSQ

Transmitter Model of Dual-Channel Spreading

I and Q channels are uncorrelated.


Normalized deviation of complex spreading and dual-channel spreading signals

00.2

0.25

0.3

0.35

0.4

0.45

I/Q unbalanced power ratio -- g

ND

50.2 0.4 0.6 0.8 1.25 1.67 2.51 ∞

Dual-channel spreadingComplex spreading

Normalized Deviation of Envelope


Forward Link Transmit DiversityTransmit diversity– two antennas are used to transmit the same code channel– achieve increased diversity gain, improve forward-link performance

Two modes– Orthogonal Transmit Diversity (OTD): take advantage of the decoding process,

achieve diversity in the Viterbi decoder path metrics, code dependent, the more powerful the code, the better the performance

– Space Time Spreading (STS): based on Alamouti code

0T2T

dk(n+1) dk

(n)

OTD encoder

0T2T

dk(n) dk

(n)

-dk(n+1) dk

(n+1)

0T2T

dk(n+1) dk

(n)

STS encoder

0T2T

dk(n)+ [dk

(n+1)]*

dk(n+1)+ [dk

(n)]*

dk(n)- [dk

(n+1)]*

dk(n+1)- [dk

(n)]*

Source: A. Dabak, S. Hosur, T. Schmidl, and C. Sengupta, “A comparison of open loop transmit diversity schemes for third generation wireless systems,” in Proc. WCNC, vol. 1, 2000.


Reverse Channels (1)

Reverse Channels

Common channels

Access Channel (R-ACH)Enhanced Access Channel (R-EACH)Common Control Channel (R-CCCH)

Dedicated channels

Fundamental Channel (R-FCH)Supplemental Channel (R-SCH)Dedicated Control Channel (R-DCCH)Pilot Channel (R-PICH)Channel Quality Indicator Channel (R-CQICH)Acknowledgment Channel (R-ACKCH)

Trafficchannels


Reverse Channels (2)

Common Channels– employ a base station-specific PN sequence, simultaneous transmissions by multiple

MSs on the same common channel cannot be discriminated, possibility for collisions– contention-based channels, use specialized random access protocols– carry signaling in support of registration, authentication, call origination, or small

amounts of user data

Dedicated Channels– spread by mobile-specific PN sequences, can be discriminated at BS– R-FCH, R-DCCH: carry signaling or user traffic– R-SCH: carry only user traffic– R-CQICH and R-ACKCH: in support of F-PDCH (Forward-Packet Data CHannels)


Reverse Channels (3)Functional Block Diagram for Reverse Traffic Channels

Block encoder

Conv. orTurbo

encoder

Symbol repetition or puncturing

Interleaver

Orthogonal spreading

Quadraturespreading Filter

source bits

cos(2πfct)

sin(2πfct)

s(t)

CRC: Error detection Rate matching

long code

PNI PNQOther channels' modulation symbols


Functional Blocks (1)Reverse link modulation– reverse link: dedicated pilot channel, code-multiplexed with data symbols, limited

transmit power, carrier-phase estimation error is large => BPSK modulationReverse link orthogonal spreading– orthogonal code: Walsh code, spreading factor: 2~64


Functional Blocks (2)W1,0

W2,0 W2,1

W4,0 W4,2

W8,0 W8,4

W16,0 W16,8

W8,2 W8,6

W4,1 W4,3

W8,1 W8,5 W8,3 W8,7

W32,0W32,16

W64,0W64,32 W64,16 W64,48

W16,12W16,4 W16,2W16,10 W16,6W16,14 W16,1 W16,9 W16,5W16,13 W16,3W16,11 W16,7W16,15

R-SCH 1R-SCH 2

R-PICH R-DCCH R-FCHR-EACH or

R-CCCHR-CQICHR-ACKCH

Tree Structure of Walshfunctions for reverse

physical channels


Functional Blocks (3)Reverse link quadrature spreading– Purpose: separate different MSs and code channels– a pair of short PN sequences (215) are used: one for I branch and one for Q branch– a long code mask is needed to discriminate users' signals at the BS

PNI' PNQ'Same as

those used in forward

link

PNI' PNQ'


Handoff (1)Hard handoff– interfrequency handoff– CDMA2000: operate on multiple carriers, sometimes require a MS's handoff to a

different carrierSoft handoff– forward link: multiple BSs transmit identical traffic channels data symbols, the MS

combines the demodulated signals prior to frame decoding, spatial diversity– reverse link: multiple BSs receive same data symbols from the MS, decode

independently and send to BSC, BSC chooses the one with the highest quality, selection combining, weaker spatial diversity

Softer handoff– forward link: same as that in soft handoff– reverse link: some BSs are with the same BTS, the BTS can combine the

demodulated signals prior to frame decoding


Handoff (2)Softer handoff– when MS has n+m BSs in the active set, n of them corresponds to different BTSs,

the MS is in n-way soft, m-way softer handoff

BTS1BTS2

two way soft handoff

one way soft two way softer

handoff

two way softer handoff


Power Control (1)Review– Power control is especially important in CDMA systems.

Reverse link power control– consists of open loop and close loop power controls, two control loops operate

concurrently (different to WCDMA)– Open loop: long-term channel variation (distance, shadowing)– Close loop: short-term channel variation (fast fading) and open loop inaccuracy

Reverse link open loop power control– Principle: the larger the received signal strength, the smaller the transmission loss

between MS and BS is expected to be, and vice versa – MS sets its transmit power inversely proportional to the total received power


Power Control (2)Reverse link close loop power control– cooperate with BS: inner loop and outer loop– MS receives power control commands on the F-PCSCH– power control step size: 1dB, frequency: 800Hz (same as IS-95)

close loop power control - inner loop– BS estimates the received SNR on R-PICH, compares it against that allocated to the

MS (target), and sets the power control bitclose loop power control - outer loop– tracks QoS and adjust the R-PICH target SNR used by the inner loop– A measure of QoS: R-FCH FER

close loop imperfections– power control commands received in error: power control commands are transmitted

uncoded to minimize the turnaround time– incorrect SNR estimate: the received R-PICH SNR is only on average equal to the

target but exhibits fluctuations that are more pronounced when the MS moves at high speed (fast fading)


Power Control (3)Reverse link power control in soft handoff– Soft handoff: multiple BSs receive the identical signals from the MS, each BS sends

a power control command based on the received R-PICH SNR, MS receives different commands

– Rule: or-of-the-downs, the MS increase the transmit power if and only if all received power control commands are up commands; the MS is power controlled by the BS with the best reverse link

– maximizes reverse-link capacity (low transmit power, low interference to the system), guarantees that the MS can close the reverse link at all times with at least one BS

Reverse link power control in softer handoff– Softer handoff: the active set includes two or more BSs with the same BTS, the BTS

soft-combines the received signals of these BSs– inner loop power control: based on the combined received SNR– same power control command is sent from these BSs to the MS; MS combines the

power control subchannels to obtain a single power-control command


Power Control (4)Forward link power control– consists of open loop and close loop power controls (different to WCDMA)

Forward link open-loop power control– used when the forward traffic channel is initialized (e.g., call setup), the BS selects

its initial transmit power level and initializes the code channel gain, no reference, implementation dependent

– simplest solution: initialize the transmit power to the maximum allowable level to maximize call setup reliability

– done once and only once at call set up (different to reverse link)Forward link close-loop power control– activated when the MS receives two consecutive good frames at call set up and starts

reverse link transmission– BS receives power control commands on the R-PCSCH and adjusts the transmit

power accordingly


Power Control (5)

Forward link close-loop power control: inner loop– MS estimates the SNR of received F-FCH, compares it against the target value, and

sets the power control command– power control rate: 800Hz

Forward link close-loop power control: outer loop– BS sends the target F-FCH FER to MS; MS measures the FER, compares it against

the target FER, and decides the target SNR value of F-FCH– implementation dependent

Forward link power control in soft handoff– MS sends the power control command to multiple BSs in the handoff active set– due to transmission error, some BSs may receive an up command while others may

get a down command => a drift of the F-FCH transmit power of one BS relative to the other

– degrades MS receiver performance => researches on reducing the transmit power drift


Summary - Link Parameters for cdma2000

Copied from T. Ojanpera and R. Prasad, WCDMA: Towards IP Mobility ...


Summary - Link Parameters for cdma2000 (Con't)

cdma2000 1x cdma2000 3x

2 - 512


Comparison between WCDMA & cdma2000 (1)

Adapted from T. Ojanpera and R. Prasad, “An overview of air interface multiple access for IMT-2000 / UMTS,” IEEE Communication Magazine, vol. 36, p. 85, Sep. 1998.

3.84Mchips/s

WCDMA CDMA20005MHz 1.25, 5MHz

1.2288 Mchips/s for direct spreading3.6864 Mchips/s for multicarrier spreading


Comparison between WCDMA & cdma2000 (2)

Adapted from T. Ojanpera and R. Prasad, “An overview of air interface multiple access for IMT-2000 / UMTS,” IEEE Communication Magazine, vol. 36, p. 85, Sep. 1998.

WCDMA CDMA2000

( 3.84Mchips/s)

( 1.5KHz)

215

2-512


Summary of cdma2000

cdma2000 1xRTT and 3xRTT: bandwidth: 1.25MHz and 5MHz, respectively.cdma2000 system architecture: compare to that of IS-95 and WCDMAUnderstand the concepts of common channel, dedicated channel and shared channel. Detailed names and functions of specific channels: not requested.Why do different channels employ different modulation schemes? Comparison between QPSK and BPSK.Understand complex spreading and dual channel spreading: diagrams, comparisons.Transmit diversity: compared to that of WCDMA.Handoff and power control: similar to IS95 with some new operations.Measures or techniques employed in physical layer (uplink/downlink) of cdma2000 to increase the transmission rate compared to IS95: spreading factors, channel coding, modulation, multi-code transmission.

Documents

Channelisation Codes (2) - University of Hong Kongsdma/elec6040_2008/Part 6-3G systems-2.pdf · Main differences between 2G and 3G. ... – base transceiver station ... – compared