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W-CDMA AIR INTERFACE FOR 3G SYSTEMS

W-CDMA AIR INTERFACE FOR 3G SYSTEMS . By Medapati, Sai Raghavendra Reddy Gadige, Raghunath. INTRODUCTION What is W-CDMA? Stands for Wideband Code Division Multiple Access

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W-CDMA AIR INTERFACE FOR 3G SYSTEMS

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  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

  9. 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

  10. 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

  11. 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.

  12. 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

  13. 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.

  14. 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

  15. Analysis • Commercial WCDMA network Development • WCDMA Subscribers base evolution

  16. WCDMA in Practice • Uplink Capacity of satellite based W-CDMA Systems

  17. 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.

  18. Contd… • Equation to calculate pole capacity. Where, LF = Load Factor < 1 ful= 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 Preq= Eb/(No+I0) 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

  19. Contd… • Equation to calculate the capacity of the mixture of users Where, k = user type and channel combination Rcap( 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.

  20. 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.

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

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

  23. 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.

  24. Literature Cited • http://scholar.lib.vt.edu/theses/available/etd-122199-153028/unrestricted/fakhrul_thesis.pdf • http://www.comlab.hut.fi/opetus/238/lecture4_Intro_to_WCDMA.pdf( intro to wcdma) • http://www.tech-faq.com/wcdma.shtml • http://0el70beril.blogspot.com/2007/06/technical-features.html • http://www.ericsson.com/technology/whitepapers/innovations_in_wcdma.pdf • http://en.wikipedia.org/wiki/2G • http://en.wikipedia.org/wiki/3G • http://en.wikipedia.org/wiki/W-CDMA • http://www.umtsworld.com/technology/wcdma.htm • http://www.researchinchina.com/report/Telecommunications/470.html • http://delivery.acm.org/10.1145/1300000/1292336/a4-shanmugan.pdf?key1=1292336&key2=1523038221&coll=GUIDE&dl=GUIDE&CFID=13694613&CFTOKEN=23668837

  25. Thank You…

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