WCDMA

1. SEMINAR REPORT ON
WIDEBAND CODE-DIVISION
MULTIPLE ACCESS(WCDMA)
DEPARTMENT OF ELECTRONICS AND
COMMUNICATION
SUBMITTED TO: SUBMITTED BY:
MRS. MEENAKSHI AWSATHI SABAL KUMAR
SR.ASSTT. PROFESSOR EC-B(3RD YEAR)

2. CONTENT
INTRODUCTION :WCDMA
BASICS OF WCDMA
SPECIFICATIONS
GENRATION OF WCDMA
SPREADING PRINCIPLE
CODES
POWER CONTROL
WCDMA HANDOVERS
ADVANTAGES OF WCDMA
CURRENT WCDMA MARKET

3. WCDMA
 WCDMA: A high speed 3G mobile wireless technology with capacity
to offer higher data rate than CDMA.
 WCDMA has the capacity to easily handle bandwidth-intensive
applications such as video, data, and image transmission necessary
for mobile internet services.
 WCDMA was adopted as a standard by the International Mobile
Telecommunications-2000 (IMT 2000) with the intention to create a
global standard for real time multimedia services and international
roaming.
 WCDMA is direct spread technology, which means that it will spread
its transmissions over a wide, 5MHz carrier.
 WCDMA is the leading 3G wireless standard in the world today.

4. BASICS OF THE WCDMA
 WCDMA users share same radio resources whereas TDMA or
FDMA users have their own radio resources allocated.
 User signals are differentiated based on codes.

5. GENERATION OF WCDMA
Channelization Scrambling
code code
Channel QPSK
data
Channel Chip rate Chip rate
bit rate (always 3.84 Mchips/s)

6. SPREADING PRINCIPLE
Direct Sequence Spreading - Code Division Multiple Access (DS-CDMA)
 Separates users through different codes
 Codes are used for two purposes:
 Differentiate channels/users
 Spreading the data over the entire bandwidth
t
MS 1
MS 2
Code MS 3
• WCDMA (5 MHz)
f
• IS-95 (1.25 MHz)
5 MHz • CDMA2000 (1.25, 3.75 MHz)

8. SPREADING CODES
Spreading code = Scrambling code + Channelization code
Scrambling codes
 Separates different mobiles (in uplink)
 Separates different cells (in downlink)
Channelization codes
Separates different channels that are transmitted on the same scrambling
code
 Orthogonal Variable Spreading Factor (OVSF) codes
 Period depends on data rate

9. CHANNELIZATION CODES
 Channelization Codes have different length depending on the bit rate
 In the Downlink, Channelization Codes are used to distinguish between data (and
control) channels coming from the same RBS
CC3, CC4
CC1, CC2
CC5, CC6, CC7
 In the Uplink, Channelization Codes are used to distinguish between data (and
control) channels from the same UE
CC1, CC2
CC1 , CC2, CC3
CC1, CC2, CC3, CC4

10. SCRAMBLING CODES
 After the Channelization Codes, the data stream is multiplied by a special code to
distinguish between different transmitters.
 Scrambling codes are not orthogonal so they do not need to be synchronized
 The separation of scrambling codes is proportional to the code length – longer
codes, better separation (but not 100%)
 Scrambling codes are 38400 chips long

11. SCRAMBLING CODES
 In the Downlink, the Scrambling Codes are used to distinguish each cell (assigned by
operator – SC planning)
 In the Uplink, the Scrambling Codes are used to distinguish each UE (assigned by network)
Cell “1” transmits using SC1
SC1 SC1
SC3 SC4
Cell “2” transmits using SC2
SC2 SC2
SC5 SC6

12. POWER CONTROL IN WCDMA
 The purpose of power control (PC) is to ensure
that each user receives and transmits just
enough energy to prevent:
 Blocking of distant users (near-far-effect)
 Exceeding reasonable interference levels Without PC received
UE1 power levels would
UE2 be unequal
UE3
UE1
UE2
In theory with PC
UE1 UE2 UE3 received power levels
would be equal
UE3

13.  Power control can be divided into two parts:
 Open loop power control (fast power control)
 Used to compensate e.g. free-space loss in the beginning of the call
 Based on distance attenuation
 Closed loop power control (slow power control)
 Used to eliminate the effect of fast fading
 Applied 1500 times per second
 Closed loop power control can also be divided into two parts:
 Inner loop power control
 Measures the signal levels and compares this to the target value and if the
value is higher than target then power is lowered otherwise power is
increased
 Outer loop power control
 Adjusts the target value for inner loop power control
 Can be used to control e.g. the Quality of Service (QOS)

14.  Example of inner loop power control behavior:
 With higher velocities channel fading is more rapid and 1500 Hz power control may
not be sufficient

15. WCDMA Handovers
WCDMA handovers can be categorized into three different types
which support different handover modes
Intra-frequency handover
 WCDMA handover within the same frequency and system. Soft,
softer and hard handover supported
Inter-frequency handover
 Handover between different frequencies but within the same
system. Only hard handover supported
Inter-system handover
 Handover to the another system, e.g. from WCDMA to GSM. Only
hard handover supported

16. WCDMA Handovers
 Soft handover
 Handover between different base
stations
 Connected simultaneously to
multiple base stations
 The transition between them
should be seamless
 Downlink: Several Node BS
transmit the same signal to the
UE which combines the
transmissions
 Uplink: Several Node BS receive
the UE transmissions and it is UE: USER EQUIPMENT
required that only one of them
receives the transmission BS:BASE STATION
correctly

17. WCDMA Handovers
 Softer handover SECTOR B
 Handover within the coverage
area of one base station but
between different sectors UE1
 Procedure similar to soft
handover BS 2
 Hard handover
 The source is released first and
then new one is added
 Short interruption time SECTOR A CELLS

18. CURRENT WCDMA MARKETS
 GSM+WCDMA share currently over 86%.
Around 260 WCDMA networks in over 105 countries.
 CDMA share decreasing every year.
More than 340 million WCDMA subscriber.

19. WCDMA SPECIFICATIONS
 CHANNAL BANDWIDH : 5MHZ
 DUPLEX MODE : FDD and TDD
 CHIP RATE : 3.84Mbps
 FRAME LENTH : 10ms
 SPREADING MODULATION BALANCED QPSK(DOWNLINK)
DUAL CHANNEL QPSK(UPLINK)
 DATA MODULATION : QPSK (DOWNLINK)
BPSK(UPLINK)
 CHANNEL CODING : CONVOLUTIONAL and TURBO
CODES
 COHERENT DETECTION : USER DEDICATED TIME
MULTIPLEXED PILOT
 HANDOVER : SOFT HANDOVER and FREQUENCY
HANDOVER

20. ADVANTAGES OF WCDMA
SERVICE FLEXIBILITY
SPECTRUM EFFICIENCY
CAPACITY AND COVERAGE
EVERRY CONNECTION CAN PROVIDE MULTIPLE SERVICE
NETWORK SCALE ECONOMICS
OUTSTANDING VOICE CAPABILITY