WCDMA

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 ENHANCEMENT IN WCDMA SPECIFICATION OF WCDMA

3. Definition of 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 Channel data Channelization code Scrambling code Channel bit rate Chip rate Chip rate (always 3.84 Mchips/s) QPSK

6. Separates users through different codes Codes are used for two purposes : Differentiate channels/users Spreading the data over the entire bandwidth f Code t MS 1 MS 2 MS 3 5 MHz WCDMA (5 MHz) IS-95 (1.25 MHz) CDMA 2000 (1.25, 3.75 MHz) SPREADING PRINCIPLE Direct Sequence Spreading - Code Division Multiple Access (DS-CDMA )

7. User information bits are spread into a number of chips by multiplying them with a spreading code The chip rate for the system is 3.84 Mchip/s and the signal is spread in 5 MHz The Spreading Factor (SF) is the ratio between the chip rate and the symbol rate The same code is used for de/spreading the information after it is sent over the air interface. Information signal Spreading signal Transmission signal SPREADING PRINCIPLE

8. 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. SPREAD SPECTRUM GAIN

10. BENEFITS OF SPREADING MOD DEM DET F MOD - modulation DEM - demodulation F - filtering DET - detection NBI - narrow-band interference WBI - wide-band interference 384 kbps 1 1 f P Spreading code 3.84 Mcps 2 Spreading factor Processing gain G = R chip R bit f P 2 WBI NBI 3 f P WBI NBI 3 4 P f 4 5 f P 5

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

12. 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 SCRAMBLING CODES

13. 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) SC3 SC4 SC5 SC6 SC1 SC1 Cell “1” transmits using SC1 SC2 SC2 Cell “2” transmits using SC2

14. SCRAMBLING CODE PLANNING 64 Code Groups SC are organized in Code Groups. The first SC in each Code Group differs from the first SC in the subsequent Code Group by a multiple of 8

15. 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 UE1 UE2 UE3 UE1 UE2 UE3 UE1 UE2 UE3 Without PC received power levels would be unequal In theory with PC received power levels would be equal

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

17. Power control can be divided into two parts : Open loop power control (slow power control ) Used to compensate e.g. free-space loss in the beginning of the call Based on distance attenuation estimation from the downlink pilot signal Closed loop power control (fast 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 )

18. HANDOVER IN CDMA

19. Current WCDMA markets GSM+WCDMA share currently over 86% CDMA share decreasing every year

20. 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

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

22. 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

23. 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 required that only one of them receives the transmission correctly

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