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W-CDMA AIR INTERFACE FOR 3G SYSTEMS By Medapati, Sai Raghavendra Reddy Gadige, Raghunath.

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Presentation on theme: "W-CDMA AIR INTERFACE FOR 3G SYSTEMS By Medapati, Sai Raghavendra Reddy Gadige, Raghunath."— Presentation transcript:

1 W-CDMA AIR INTERFACE FOR 3G SYSTEMS By Medapati, Sai Raghavendra Reddy Gadige, Raghunath

2 INTRODUCTION  What is W-CDMA?  Stands for Wideband Code Division Multiple Access  It is a type of 3G cellular network. It acts as an air interface for 3G systems.  It is an ITU’s IMT-2000 standard.  Uses CDMA technology  Uses 5MHz wide frequency band.

3 Evolution from 2G to 3G  From 2G to 2.5G  GPRS (General Packet Radio Service)  data rates 56 kbps to 114 kbps  From 2.5G to 2.75G  GPRS to EDGE (Enhanced Data rates for GSM Evolution)  From 2.75G to 3G  EDGE to UMTS (Universal Mobile Telecommunications Service)  Data rates 144kbps, 384kbps, 2 Mbps. Compare…

4 Development  GSM Successful, Plans 3G systems  CoDiT (Code Division Testbed) started, first W-CDMA  FRAMES ( Future Radio wideband Multiple Access Systems) started, to support European 3G standards  5 groups formed by ETSI (European Telecommunications Standard Institute)

5 Contd…  W-CDMA developed by NTT DoCoMo as air interface for 3G FOMA (Freedom of Mobile Multimedia Access)  ITU accepted W-CDMA as IMT-2000 standard.  W-CDMA adopted in 55 countries

6 Technical Features  Data rates 384 kbps (wide coverage), 2 Mbps (local coverage)  Operates in 2 modes FDD and TDD  High service flexibility  Efficient packet access

7 Contd…  Supports inter frequency handover, handover to other systems  Uses 5 MHz wide frequency band. High speed.  Built in support for future technologies and coverage enhancing technologies.

8 Technologies Used  Asynchronous Network Operation  Cell Search  As Asynchronous, no need to search for base stations  Uses common base station code with unique base station time shifts  Soft Handover  Communicates same information through 2 or more base stations  Per call synchronization


10 Contd…  Compressed mode  Mobile devices dual mode  Handover from WCDMA to GSM crucial  Compressed mode, SF is changed and compress the transmitting and receiving information for a short time span.  Remaining time for measuring other frequencies. Measures sent to network


12 Contd…  Uplink Power Control  Due to near-far problem  Power control for uplink needed  Open loop and Closed loop  Closed loop is used with update rate of 1500 Mhz. 2G systems use update rate of 800 Mhz


14 Contd…  Random access  RACH( Random Access Channel), initial access.  RACH codes transmitted through downlink  Scrambling codes and a signature are randomly selected and sent with increasing power  Sufficient power, acquisition indicator.


16 Contd…  Coherent Uplink Detection  Used for data reception.“Pilot symbols” used in Uplink and Downlink.  CDMA2000 adopted these Pilot symbols  OVSF Codes  higher flexible bearer system to send all kinds of data  OVSF (Orthogonal Variable Spreading Factor) codes, formed form code tree principle.  Reduces interference, minimizes crosstalk  Data Rate Indication  TFCI (Transport Format Combination Indicator)  Blind-rate detection

17 Contd…  Speech Codec  Speech signal transmitted efficiently with high capacity, speech codec required  12. 2 kbps AMR codec used  High-speed Packet Data  HSPA (High-Speed Packet Access) an extension of W-CDMA  Enhanced data rates up to 100 Mbps  These are the 4 schemes used in HSPA shared channel with channel dependent scheduling, fast link adaption, hybrid ARQ with sort combining, a short TTI are used.

18 Contd…  Broadcast and Multi cast Services  MBMS (Multimedia Broadcast and Multicast Service)  The user residing at the cell edge, signal from adjacent base station is used. Downlink soft handover used.  Increase in data rates and coverage  W-CDMA uses same carrier for MBMS where CDMA2000 uses separate carrier and separate receiver


20 Analysis  Commercial WCDMA network Development  WCDMA Subscribers base evolution

21 WCDMA in Practice  Uplink Capacity of satellite based W- CDMA Systems

22 Contd…  The commercial and military operations now a days using satellite based WCDMA systems.  The main factors to be considered are Uplink and Downlink Capacity.  There are 2 types of WCDMA used in this system. Terrestrial WCDMA and GEOS( Geosynchronous) WCDMA.

23 Contd…  Equation to calculate pole capacity. Where, LF = Load Factor < 1 f ul = Adjacent beam to within- beam MAI b = reduction in adjacent beam MAI due to beam forming G (lambda/μ ) = 1+ (2.32/ sqrt( lambda μ ) ) : Effect of dynamic traffic W = 3.84 MChips/sec P req = E b /(N o +I 0 ) required to meet QOS M = Channel fade margin needed to guarantee 99% availability ≥ 1 PC Gain = Reduction in fade margin due to power control ≥ 1 L = Losses (implementation losses) ≤ 1

24 Contd…  Equation to calculate the capacity of the mixture of users Where, k = user type and channel combination R cap ( i) = Capacity of all users belonging to ith channel  The above two equations are used to calculate the uplink capacity of satellite based WCDMA systems.

25 Advantages  W-CDMA provides faster data connection ( 384kbps and in future 10Mbps  Can do all the activities that a normal phone does (SMS, MMS, INTERNET etc.) and supports fast video streaming.  Simultaneous usage of all the activities even on call.  We will only be billed for the data transferred but not for the time connected.

26 Contd…..  In W-CDMA, cells use single frequency with differentiated codes.  Cell planning is easier.  Uses asynchronous operation.  Longer battery life.

27 Limitations  Uses wide frequency band. Mechanism for maximum usage.  Cell planning is easier but it should be done carefully.

28 Conclusion  Drastic change in cellular technology  HSPDA ( High Speed Downlink Packet Access). Extension of UMTS.  W-CDMA used in almost every 3G mobile.  Research on 4G started.

29 Literature Cited   intro to wcdma)          shanmugan.pdf?key1=1292336&key2=1523038221&coll=GUIDE&dl=GUIDE&CFID=13694613&CFTO KEN=23668837

30 Thank You…

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