3 rd Generation WCDMA UMTS Wireless Network BY

3 rd Generation WCDMA / UMTS Wireless Network BY PRATHEEBA. V(132242601013) M. TECH COS 1

UMTS: ¡ ¡ This is the successor of 2 G (GSM) network specification in which much more consideration was given for higher data rates to support a variety of applications by mobile users. UMTS uses a totally different air interface for radio communications hence different from 2 G in many ways and require specialized handsets for the new networks based on UMTS. WCDMA is the air interface technology being used in UMTS networks. The network architecture has a core network and access network known as UTRAN (Universal Terrestrial Radio Access Network) which consists of node B and RNC (Radio Network Controller) analogues to BTS and BSC in 2 G networks. 2

W-CDMA: ¡ ¡ ¡ W-CDMA or WCDMA (Wideband Code Division Multiple Access), along with UMTS-FDD, UTRA-FDD, or IMT-2000 CDMA Direct Spread is an air interface standard found in 3 G mobile telecommunications networks. It supports conventional cellular voice, text and MMS services, but can also carry data at high speeds, allowing mobile operators to deliver higher bandwidth applications including streaming and broadband Internet access. The main feature behind WCDMA technique is that the 5 MHz channel bandwidth is used to send the data signals over the air interface and in order to achieve this original signal is mixed with a pseudo random noise code which is also known as Direct Sequence CDMA. 3

¡ ¡ This is a unique code for each user and only the users who are having the correct code can decode the message. So with the high frequency associated with the pseudo signal, original signal is modulated in to higher frequency signal and due to high spectrum original signal spectral components sink in the noise. Frequency band assigned for FDD-WCDMA consists of 19201980 and 2110 -2170 MHz Frequency paired uplink and downlink with 5 MHz band width channels and duplex distance is 190 MHz s. Originally WCDMA uses QPSK as the modulation scheme 4

Evolution : From 2 G to 3 G Source : Northstream, Operator Options for 3 G Evolution, Feb 2003. 5

Evolution : From 2 G to 3 G Primary Requirements of a 3 G Network ¡ Fully specified and world-widely valid, Major interfaces should be standardized and open. ¡ Supports multimedia and all of its components. ¡ Wideband radio access. ¡ Services must be independent from radio access technology and is not limited by the network infrastructure. 6

Standardization of WCDMA / UMTS WCDMA Air Interface, Main Parameters Multiple Access Method DS-CDMA Duplexing Method FDD/TDD Base Station Synchronization Asychronous Operation Channel Separation 5 MHz Chip Rate 3. 84 Mcps Frame Length 10 ms Service Multiplexing Multiple Services with different Qo. S Requirements Multiplexed on one Connection Multirate Concept Variable Spreading Factor and Multicode Detection Coherent, using Pilot Symbols or Common Pilot Multiuser Detection, Smart Antennas Supported by Standard, Optional in Implementation 7

UMTS System Architecture Iu Node B RNC USIM Cu ME MSC/ VLR GMSC External Networks Uu Node B Iub Iur HLR Node B RNC Node B UE UTRAN SGSN GGSN CN 8

UMTS Bearer Services UMTS TE MT CN Iu EDGE NODE UTRAN CN Gateway TE End-to-End Service TE/MT Local Bearer Sevice External Bearer Service UMTS Bearer Service Radio Access Bearer Service Radio Bearer Service Iu Bearer Service UTRA FDD/TDD Service Physical Bearer Service CN Bearer Service Backbone Network Service 9

WCDMA Air Interface UE UTRAN CN Wideband CDMA, Overview ¡ DS-CDMA, 5 MHz Carrier Spacing, ¡ CDMA Gives Frequency Reuse Factor = 1 ¡ 5 MHz Bandwidth allows Multipath Diversity using Rake Receiver ¡ Variable Spreading Factor (VSF) to offer Bandwidth on Demand (Bo. D) up to 2 MHz ¡ Fast (1. 5 k. Hz) Power Control for Optimal Interference Reduction ¡ Services multiplexing with different Qo. S l l Real-time / Best-effort 10% Frame Error Rate to 10 -6 Bit Error Rate 10

WCDMA Air Interface UTRAN UE CN Direct Sequence Spread Spectrum Spreading User 1 f Wideband f Spreading Received User N f Wideband Multipath Delay Profile Code Gain Despreading f f Narrowband f Þ Frequency Reuse Factor = 1 Variable Spreading Factor (VSF) Spreading : 256 Wideband t User 1 f Wideband f Spreading : 16 Narrowband t Þ 5 MHz Wideband Signal allows Multipath Diversity with Rake Receiver User 2 f Wideband f Þ VSF Allows Bandwidth on Demand. Lower Spreading Factor requires Higher SNR, causing Higher Interference in exchange. 11

WCDMA Air Interface UE UTRAN CN Mapping of Transport Channels and Physical Channels Broadcast Channel (BCH) Forward Access Channel (FACH) Primary Common Control Physical Channel (PCCPCH) Secondary Common Control Physical Channel (SCCPCH) Paging Channel (PCH) Random Access Channel (RACH) Dedicated Channel (DCH) Physical Random Access Channel (PRACH) Dedicated Physical Data Channel (DPDCH) Dedicated Physical Control Channel (DPCCH) Downlink Shared Channel (DSCH) Physical Downlink Shared Channel (PDSCH) Common Packet Channel (CPCH) Physical Common Packet Channel (PCPCH) Synchronization Channel (SCH) Common Pilot Channel (CPICH) Acquisition Indication Channel (AICH) Highly Differentiated Types of Channels enable best combination of Interference Reduction, Qo. S and Energy Efficiency, Paging Indication Channel (PICH) CPCH Status Indication Channel (CSICH) Collision Detection/Channel Assignment Indicator Channel (CD/CA-ICH) 12

UTRAN UE UTRAN CN UMTS Terrestrial Radio Access Network, Overview ¡ Two Distinct Elements : Base Stations (Node B) Radio Network Controllers (RNC) ¡ ¡ 1 RNC and 1+ Node Bs are group together to form a Radio Network Sub-system (RNS) Handles all Radio-Related Functionality l l ¡ Soft Handover Radio Resources Management Algorithms Maximization of the commonalities of the PS and CS data handling Node B RNC Node B RNS Iur Iub Node B RNC Node B RNS UTRAN 13

Core Network UE UTRAN CN Core Network, Overview Changes From Release ’ 99 to Release 5 ¡ A Seamless Transition from GSM to All-IP 3 G Core Network ¡ Responsible for Switching and Routing Calls and Data Connections within, and to the External Networks MSC/ VLR (e. g. PSTN, ISDN and Internet) ¡ Divided into CS Network and PS Network GMSC External Networks ¡ HLR Iu SGSN GGSN CN 14

Core Network UE UTRAN CN Core Network, Release ‘ 99 CS Domain : l The switch that connects to external networks PS Domain : l HLR Holds a copy of the visiting user’s service profile, and the precise info of the UE’s location Gateway MSC (GMSC) ¡ ¡ Switching CS transactions Visitor Location Register (VLR) ¡ l Serving GPRS Support Node (SGSN) ¡ Similar function as MSC/VLR Iu-ps ¡ SGSN l Home Location Register (HLR) Gateway GPRS Support Node (GGSN) ¡ Similar function as GMSC GGSN Register : ¡ l GMSC Mobile Switching Centre (MSC) ¡ l MSC/ VLR Iu-cs External Networks ¡ ¡ Stores master copies of users service profiles Stores UE location on the level of MSC/VLR/SGSN 15

Core Network UE UTRAN CN Core Network, R 5 ¡ 1 st Phase of the IP Multimedia Subsystem (IMS) l l ¡ Enable standardized approach for IP based service provision Media Resource Function (MRF) Call Session Control Function (CSCF) Media Gateway Control Function (MGCF) Iu-cs Iu-ps MSC GMSC MGW SGSN GGSN HSS External Networks CS Domain : l MSC and GMSC ¡ l Control Function, can control multiple MGW, hence scalable MSG ¡ ¡ Services & Applications Replaces MSC for the actual switching and routing MRF IMS Function CSCF MGCF Services & Applications PS Domain : l Very similar to R’ 99 with some enhancements 16

Radio Resources Management ¡ Network Based Functions l Admission Control (AC) ¡ l Load Control (LC) ¡ l Manages situation when system load exceeds the threshold and some counter measures have to be taken to get system back to a feasible load. Packet Scheduler (PS) ¡ ¡ Handles all new incoming traffic. Check whether new connection can be admitted to the system and generates parameters for it. Handles all non real time traffic, (packet data users). It decides when a packet transmission is initiated and the bit rate to be used. Connection Based Functions l Handover Control (HC) ¡ ¡ l Handles and makes the handover decisions. Controls the active set of Base Stations of MS. Power Control (PC) ¡ ¡ Maintains radio link quality. Minimize and control the power used in radio interface, thus maximizing the call capacity. Source : Lecture Notes of S-72. 238 Wideband CDMA systems, Communications Laboratory, Helsinki University of Technology 17

Connection Based Function Power Control ¡ Prevent Excessive Interference and Near-far Effect ¡ Open-Loop Power Control l l ¡ If quality < target, increases SIRTARGET Rough estimation of path loss from receiving signal Initial power setting, or when no feedback channel is exist Fast Close-Loop Power Control l l ¡ Outer Loop Power Control Feedback loop with 1. 5 k. Hz cycle to adjust uplink / downlink power to its minimum Even faster than the speed of Rayleigh fading for moderate mobile speeds Outer Loop Power Control l l Fast Power Control If SIR < SIRTARGET, send “power up” command to MS Adjust the target SIR setpoint in base station according to the target BER Commanded by RNC 18

Connection Based Function Handover ¡ Softer Handover l l l ¡ Soft Handover l l ¡ A MS is in the overlapping coverage of 2 sectors of a base station Concurrent communication via 2 air interface channels 2 channels are maximally combined with rake receiver A MS is in the overlapping coverage of 2 different base stations Concurrent communication via 2 air interface channels Downlink: Maximal combining with rake receiver Uplink: Routed to RNC for selection combining, according to a frame reliability indicator by the base station A Kind of Macrodiversity 19

WCDMA vs cdma 2000 Adopted by Telecommunications Industry Association, backward compatible with IS-95, lately moved to 3 GPP 2 (in contrast to 3 GPP for WCDMA) as the CDMA Multi. Carrier member of the IMT-2000 family of standard Some of the Major Differences WCDMA cmda 2000 Remarks Spread Sprectrum Technique 5 Mhz Wideband DS-SS Multicarrier, 3 x 1. 25 MHz Narrowband DS-SS, 250 k. Hz Guard Band Multicarrier does not requires a contiguous spectral band. Both scheme can achieve similar performance Chip Rates 3. 84 Mcps 3. 6864 Mcps (1. 2288 per carrier) Chip Rate alone does not determine system capacity Frame Lengths 10 ms 20 ms for data, 5 ms for control Response and efficiency tradeoff Power Control Rate 1. 5 k. Hz 800 Hz Higher gives better link performance Base Station Synchronization Asynchronous Synchronized Asynchronous requires not timing reference which is usually hard to acquire. Synchronized operation usually gives better performance 20

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