WCDMA Overview

* Outline

IntroductionWhat is different from GSMBasic Concept of 3G (UTRAN)WCDMA Coverage & CapacityCore network Architecture and EvolutionHSDPA Basics

* Introduction

Mobile networks established in mid 80s

It is widely recognized that there are three different generations as far as Mobile communications is concerned.

The first generation, 1G Speech The Second generation, 2G Speech+ DataThe Third Generation, 3G Speech+ High Data Speed

* Evolution from 2G to 3GBasic GSM and VAS are basically meant to produce mass services for mass people but due to requirements raised from end-users, more individual type of services is required.

3G introduces the new radio access method, WCDMA. WCDMA and its variants are global.

* Evolution from 2G to 3G

* GSM and WCDMA ComparisonSeparate users through different codesContinuous transmission and receptionCode planning No Frequency PlanningVariable Cell Radius: Cell BreathingRadio Link: 1 UE Many Node-BsPower is CapacityScrambling Code PlanningHard/Soft/Softer HandoverOrthogonal in time within a cellTime Slot Synchronization in timeFrequency planningFixed Cell RadiusRadio Link: 1 MS 1 RBS# of Frequencies limit capacityBSIC PlanningHard Handover

GSMWCDMABTSNodeBBSCRNCMSUE

* GSM Radio Access NetworkCore NetworkBSCBSCA/GbAbisUmMS

* WCDMA Radio Access NetworkIu= Iu PS - Gb Iu CS - A

* Development process for 3GThe third generation, 3G, is expected to complete the globalization process of the mobile communication. Again there are national and regional interests involved and difficulties can be foreseen.

* What is WCDMA.....Wide Band Code Division Multiple Access is a third generation mobile communication system. Its a wireless system where the telecommunication, datacom & media industry converge and is based on a Layered Architecture.

Convergence:

User Service convergenceDevice convergenceNetwork convergence

*From Single- to Multi-Service Networks

* Layered ArchitectureThe architecture of telecommunication networks, whether wireless or wire line has changed and they are now split into several horizontal layers that are more or less independent of each other.

* Multiple AccessThe cellular concept approaches the capacity limitation in terms of system coverage. Therefore, it does not alone help the per-cell capacity limitation as far as the simultaneous users are in question. From radio spectrum standpoint, it is extremely important how the radio resources are allocated to the simultaneous users.

Numbers of multiple accesses have been developed to combat the problem of simultaneous radio access allocation to the access requesters.

The main aspect of any multiple access scheme is the strategy how the available frequency band is allocated.

* Different Approaches

* WCDMA BandFrom 3G point of view, it has been decided (in mid-1999 by OHG) that therewill be three CDMA variants in use. Those are:

DS-WCDMA-FDD: Direct Sequence- Wideband Code Division Multiple Access - Frequency Division DuplexUplink: 1920 -1980 MHzDownlink: 2110 -2170 MHzDuplex Distance: 190 MHz

DS-WCDMA-TDD: Direct Sequence- Wideband Code Division Multiple Access Time Division DuplexLower Band: 1900 -1920 MHzUpper Band: 2010 -2025 MHz

MC-CDMA: Multi Carrier - Code Division Multiple AccessIt was chosen for private indoor services

* WCDMA BandwidthIn WCDMA, the data stream of the base station transmitter handles in downlink direction represents the traffic from the network to the terminal. This traffic uses several channels in the Uu interface. In the Uu interface the effective bandwidth for WCDMA is 3.84 MHz and with guard bands the required bandwidth is 5 MHz.

* WCDMA at a glance

* WCDMA Frequency allocations

* Basic ConceptThe principles of WCDMA technique are based on Spread Spectrum.

* Spread SpectrumThe main advantages of the spread spectrum are:

Its resistance to radio interference and jamming. It lowers the probability of intercept by an adversary. Its resistance to signal interference from multiple transmission signal branches. It providing multiple access facility with a reuse factor equal to one. It supporting means for measuring range, or the distance between two points. It yields the possibility of utilising diversity techniques, including multi-path diversity, as well as frequency and time diversity. It provides user access at any time without waiting for a free channel as far as the level of interference meets the system's tolerance.

* WCDMA Network The WCDMA network is a multi-service network of networks, providing both traditional telecommunications services and new internet based services over the same network with support for high bit rates.Network Architecture:3GPP (Third Generation Project Partnership) Reference Model:Based on 3GPP reference network model, the WCDMA network can be considered to consists of four major components:

User Equipment (UE)Access Network (AN)Core Network (CN)Network External to WCDMA

* 3GPP Release 1999 Reference ArchitectureCo-operatingNetworksUser EquipmentRadio Access NetworkCore NetworkNote: Not all interfaces are shown and namedBSCBTSUmAbisBSSFHLRDCEIRAUCEAGMSCGfGnSGSNGbGrGnSGSNGGSNGsGcGiGdIuCSMSC/VLRGHGpISDNPSTNPSPDNCSPDNPDN:- Intranet- Extranet- Internet- X.25MSC/VLRSCFMESIM-ME i/fSIMMS

* WCDMA ChannelsThe WCDMA radio access allocates bandwidth for users and the allocated bandwidth and its controlling functions are handled with term Channel.

WCDMA uses 3 Layers:

1. Logical Channels: Describe the types of information to be transmitted

2. Transport Channels: Describe how the Logical Channels are to be transferred.

3. Physical Channels: These are the transmission media providing the radio platform through which the information is actually transferred.

In GSM the Physical Channels and their structure is recognised by the BSC but in WCDMA the Physical Channels really exist in the Uu interface and the RNC is not necessarily aware their structure at all. Instead of Physical Channels the RNC sees Transport Channels.

* Channel Architecture

* UTRANThe main task of UTRAN is to create and maintain Radio Access Bearers (RAB) for communication between UEs and Core Network.

With RAB the Core Network elements are given an illusion about a fixed communication path to the UEs thus releasing them from the need to take care of radio communication aspects.

UTRAN is located between two open interfaces being Uu and Iu.

From the bearer architecture point of view the main task of UTRAN is to provide Bearer service over these interfaces.

* What is Radio Access Bearer (RAB) ?RAB The Radio Access Bearer (RAB) is the entity responsible for transporting radio frames of an application over the access network in UMTS.Controlled by the core network (CN)CN determines traffic class and QoS Real-Time ApplicationsStreaming Class: Preserve time relation between entities (packets) in a data streamConversational Class: Preserve time relation between entities within a certain delayNon-Real Time ApplicationsBackground Class: Destination is not expecting data. Preserve PayloadInteractive Class: Request / Response Pattern with preserved payload

*Conversational Speech12.2 kbps Circuit switchedConversational CS Data64 kbps Circuit switched RAB Examples

* RAB Attributes Transfer delayRAB Service Attributes Traffic Class Maximum bit rate [kbps] Delivery order Maximum SDU size SDU format information SDU error ratio Residual bit error ratio Delivery of erroneous SDUs Guaranteed bit rate Traffic handling priority Allocation/retention priority Source statistics descriptor Relocation requirementRAB asymmetry indicatorRABUERBSRNCCN

* UTRAN Architecture

* UTRAN & Interfaces

* NODE BThe BS is located between the Uu and Iub interfaces. Its main tasks are to establish the physical implementation of the Uu interface and, towards the network, the implementation of the Iub interface by utilising the protocol stacks specified for these interfaces.

Realization of the Uu interface means that the BS implements WCDMA radio access physical channels and transfers information from transport channels to the physical channels based on the arrangement determined by the RNC.

* Modulation MethodWCDMA uses Quadrature Phase Shift Keying (QPSK) as its modulation method in downlink direction and the Offset Quadrature Phase Shift Keying (OQPSK) in uplink direction.

The result is that the spectrum used for QPSK and OQPSK is the same but OQPSK has smoother signal. This allows the amplifiers to operate also on their non-linear operating area without problems.

The conventional QPSK could be used in both directions but then the UE would suffer power consumption problems and high prices.

* Receiver TechniqueThe WCDMA utilises multipath propagation.

On the other hand, to gain better capacity in the radio network, the transmit powers of the UEs (and BSs) should be relatively small. This decreases interference in the radio interface and gives more space for other transmissions and it is very useful that both the UE and the BS are able to collect many weak level signals.

This requires special type of receiver. One example of this kind of arrangement is called RAKE.

The purpose of the RAKE receiver is to improve the received signal level by exploiting the multi-path propagation characteristics of the radio wave.

* Diversity Technique

In general, diversity techniques are efficient means to overcome the radio signal deterioration due to shadowing and fading.

In addition to that utilizing diversity technique is a prerequisite for providing soft handover feature in the cellular systems. In WCDMA technology, typically polarisation diversity is utilized both for uplink and down transmission.

The purpose of multipath diversity is to resolve individual multipath components and combine them to obtain a sum signal component with better quality.

* RNC (Radio Network Controller)The RNC is switching and controlling element of the UTRAN. RNC is located between the Iub and Iu interface. It also has the third interface called Iur for inter-RNS connections.

Referring to the Bearers, the RNC is a switching point between the Iu Bearer and Radio Bearer(s).

* RNC FunctionThe whole functionality of RNC can be classified into two parts:

UTRAN Radio Resource Management UTRAN Control Functions

* Radio Resource ManagementThe RRM is a collection of algorithms used to guarantee the stability of the radio path and the QoS of radio connection by efficient sharing and managing of the radio resources.

The RRM algorithms to be shortly presented here are:

Handover ControlPower ControlAdmission Control and Packet SchedulingCode Management

* Handovers

* WCDMA Handover Scenarios

* Soft Handover In WCDMA system, the majority of handovers are intra-frequency soft handovers

* Concept of Soft/Softer HandoverCell ACell BCell CThe UE measured the CPICH Signal strenght (RSCP) and quality (Ec/No) to determine which cell to add in the active set

Add and remove from active set is based on relative measurments

*Inter Radio Access Technology (IRAT) handover

* Hand over from/to GSM

* POWER CONTROLPower control is an essential feature of any CDMA based cellular system. In WCDMA, power control is employed in both uplink and downlink.

Downlink power control is basically for minimising the interference to other cells and compensating for other cells' interference as well as achieving acceptable SIR.

To manage the power control properly in WCDMA, the system uses different two defined power control: Open Loop Power Control Closed Loop Power Control (CLPC), including Inner and Outer Loop Power Control mechanisms

* Types of Power ControlOpen Loop Power Control (OLPC): Basically used for uplink power adjusting, the UE adjusts its transmission power based on estimate of the received signal level from the BS Common Pilot Channel (CPICH) when the UE is in idle mode and prior to Physical Random Access Channel (PRACH) transmission.

Closed-Loop Power Control (CLPC): Utilised for adjusting the transmission power when the radio connection has already been established. Its main target is to compensate the effect of rapid changes in the radio signal strength and hence it should be fast enough to respond to those changes.

* Admission Control and Packet SchedulingWCDMA Radio Access has several limiting factors, but the most difficult to control is the interference occurring in the radio path. When the WCDMA cellular network is planned, one of the basic criteria for planning is to define the acceptable interference level with which the network is expected to function correctly. The main task of Admission Control is to estimate whether a new call can have access to the system without sacrificing the bearer requirements of existing calls.

Also responsible to handle packet connections with bursty traffic, having a very random arrival time, number of packet call per session, reading time, as well as number of packets within a call.

* Code ManagementRNC manages both Channelisation and Scrambling Codes used in the Uu interface connections.In principle, the BS could manage them, but then the system may behave unstable when the RNC is otherwise controlling the radio resources. The Uu interface requires two kinds of codes for proper functionality: Every Cell uses 1 Scrambling Code, the UE is able to make separation between cells by recognising this code. Under every Scrambling Code the RNC has a set of Channelisation Codes.

* Control FunctionsIn order for the UTRAN to control and manage the radio bearers, which is essential to provide the Radio Access Bearer (RAB) service, it should perform other functions in addition to the RRM algorithms.

These can be classified as:

System Information BroadcastingRandom Access and Signalling Bearer SetupRadio Bearer ManagementUTRAN Security FunctionsUTRAN level mobility managementDatabase HandlingUE positioning

* WCDMA in nutshell

* What is Coverage in WCDMASignal does not mean Coverage in WCDMAPilot Signal - RSCPPilot Ec/NoService CoveragePilot RSCPPilot Ec/No

* Capacity Considerations Effect of different user distributionHigh power usageLow capacityLow power usageHigh code usageCode limited scenarioPower limited scenario

* CELL CAPACITYIn GSM the TRX capacity calculation is very straightforward procedure but because in WCDMA the radio interface is handled differently and the system capacity is limited by variable factors, the capacity of the WCDMA TRX is not very easy to be determined.

The capacity of a cell depends on the downlink Scrambling Code amount assigned for the cell (minimum is 1). Every downlink Scrambling Code then has a set of Channelisation Codes under it and every call/transaction requires one Channelisation Code to operate.

In WCDMA technology, all the users share the common physical resource, being frequency band in 5 MHz slices. All users of the WCDMA TRX co-exist on the frequency band at the same moment of time and different transactions are for the people is the capacity of the WCDMA TRX.

Some assumptions: All the subscribers under the TRX coverage area are equally distributed so that they have equal distances to the TRX antenna. The Power level they use is the same and thus the interference they cause is on the same level. Subscribers under the TRX use the same baseband bit rate, i.e. also the same Symbol Rates.

* CALCULATIONSUnder these circumstances:

A value called Processing Gain (Gp) - Its a relative indicator informing what is the relationship between the whole bandwidth available (BRF) and the Baseband bit rate (B Information).G p = B RF/ B Information

or G p = Chip rate/ Data rate

The system chip rate is constant; 3.84 Mcps (3840000 chips per second). Hence, as an example the Bearer having the bit rate 30 kb/s will have the Spreading Factor 128:

Assume that SNR = Eb/No is 3 dB, then

Users per TRX will be : 128/2 = 64

* Designing for LoadRAB Coverage UnloadedRAB Coverage High LoadCoverage shrinks with load due to cell breathing.

Coverage and capacity evaluation should be performed early in the design.

Capacity per sector is specified, then coverage is evaluated under corresponding load.

Coverage and capacity can be traded off.Large coverage footprint, low capacity.Smaller coverage footprint, high capacity.

* Transport DesignDesign Criteria:Up to 6 Node-Bs grouped into one cluster of a Sub-hubUp to 4 Sub-Hub clusters grouped into 1 hub.STM-1 from Hub/Sub-Hub to RNC through media

Interfaces:End node-B: E1 interface.Sub-Hub: E1 interface southbound and STM-1 interface northbound.Hub: STM-1 interface.

* 3GPP (3rd Generation Partnership Project) release outline

3GPP Releases

3GPP Release 1999

Release 4

Release 5

Future evolution with R6, R7..

* 3GPP Releases - Time Schedule19982001199920003GPP Release 43GPP Release 1999Q2Q1Q3Q2Q3Q4Q4Q1Q1Q2Q3Q4Q4Q3Q1109785423111213GPP TSGsPlenary Meetings6Q220021817191615141322212023Q3Q4Q1Q2Q3Q4Q120033GPP Release 5Versions of3GPP Release 19993GPP Release 6

*Core Network - Architecture and Evolution

* How Does My Network Topology Look Today ?

SGSNIP BackboneGGSNSGSNGGSNInternetGPRS - Network BaselineGSM - Network BaselineBSCBSCGSM RANBSCBSCGSM RANTDM BackboneMSCMSCHLR/AUC

*How Would this look with WCDMASGSNWCDMA IntroductionBSCBSCGSM RANBSCBSCGSM RANMSCMSCGGSNSGSNGGSNInternetHLR/AUC

* Soft switch ConceptLayered Architecturenetwork

* What is Mobile Softswitch?Classic MSC (control and switching)MSC Server(Control)Mobile Media Gateway (Switching) Mobile Softswitch Solution Classic MSC Solution

* Distributed switching, Local Switching

* MSC Server ApplicationServersApplicationService enablersServices/applicationsControlServersControlMSCHLR/AuC/FNRGMSC/TransitConnectivityMGWMGWServerServerPSTN/ ISDNInternet IntranetsGGSNSGSNSGWUser dataGSMEDGEWCDMA

* Media GatewayApplicationServersApplicationService enablersServices/applicationsControlServersControlMSCHLR/AuC/FNRGMSC/TransitConnectivityMGWMGWServerServerPSTN/ ISDNInternet IntranetsGGSNSGSNSGWUser dataGSMEDGEWCDMA

* M-MGw InterfacesMGWHTTP, FTP,S-FTP, IIOP,SSH,TELNETATM ATM IuUP, AAL2)TDM Q.AAL2Q.AAL2RANAP, 3GPP 24.008BICCO&MISUPIP (NbUP, RTP)BSSAPTDM (A)GCP(GPS)SynchM-MGw-(NbUP, I.trunk, AAL2)(MSC/TSC ServerBSCRNCPSTN other networksM-MGw(Mc)ATM, IP IP Positioning the M-MGw in the Network

*What is High Speed Downlink Packet Access (HSDPA)Smooth Upgrade Short time to market with existing sites

* HSDPA Basic Principles

Lets be ready.

Layered Architecture is a way to make the network more flexible and efficient by separating applications, control, connectivity and access in different nodes.Ericsson Mobile Softswitch Solution implements layered architecture by separating call control and switching into separate nodes. The MSC-Server handles call control while the mobile media gateway handles switching.These are also the nodes that constitute the mobil softswitch offering.

Thanks to Jens Poscher for giving me the opportunity to present the ongoing PRAN activities within Ericsson Personal introduction. Let me introduce myself. My name is Pedro Torres, currently working at IP Infrastructure solutions for the MU Iberia. I am involved in the PRAN System Design group developing the technical solution together with some other people in the room. 3) And if you have any questions or would like to have additional information you can contact me by mail, phone or over a beer after my presentation