W-CDMAAVIK DAS

ROLL-07 SEC-AECE 4th YEAR

WHAT IS W-CDMA W-CDMA stands for Wideband Code Division Multiple Access Its an air interface standard found in 3G mobile

telecommunications networks designed for “always-on” packet-based wireless service, so that computers entertainment devices and telephones may all share the same wireless network and be connected to the internet, anytime anywhere.

It was adopted as a standard by the ITU under the name "IMT-2000 direct spread."

It is the technology used in the Universal Mobile Telecommunications System (UMTS) and is also known as UMTS-FDD.

It utilizes the DS-CDMA channel access method and the FDD duplexing method to achieve higher speeds and support more users compared to most time division multiple access (TDMA) schemes used today.

History of W-CDMA Developed by NTT DoCoMo as the air interface for their 3G

network FOMA in the late 1990s. NTT DoCoMo submitted the specification to the International

Telecommunication Union (ITU) as a candidate for the international 3G standard known as IMT-2000 which eventually accepted W-CDMA as part of the IMT-2000 family of 3G standards.

Later, W-CDMA was selected as the air interface for UMTS, the 3G successor to GSM.

February1999 - Nokia claimed to have made the first WCDMA call in the world through the PSTN at the Nokia test network in Finland using a WCDMA terminal, WCDMA base station subsystem and Nokia GSM Mobile with switching centers connected to the PSTN.

April2001 - Ericsson and Vodafone UK claimed to have made the world's first WCDMA voice call over commercial network.

October2001 - NTT DoCoMo launched the first commercial WCDMA 3G mobile network.

Technical Features Support of high data rate transmission: 384 Kbps with wide area

coverage and 2 Mbps or higher with local coverage. Minimum bandwidth of 5MHz each for reverse-link(uplink) and

forward-link(downlink). Chipping frequency of 3.84 Mchips/sec. Support both Frequency Division Duplex (FDD) and Time Division

Duplex (TDD). QPSK Modulation is used for both reverse and forward-link

frequencies. Based on Direct Sequence CDMA(DS-CDMA) technique with frame

duration of 10ms. Multiuser detection and smart antennas can be used to increase

capacity and coverage. Adaptive power control based on SIR (Signal-to-Interference Ratio). Multiple types of handoff (or handover) between different cells

including soft handoff, softer handoff and hard handoff.

WCDMA Protocol Stack

Physical Layer Located in the user equipment between the MS(Mobile

Station) and BTS(Base Transceiver Station). Transmit direction – physical layer receives blocks of data

from higher layers(MAC layer) and multiplexes them onto a physical channel.

Receive direction – physical layer receives the physical channels, extracts and processes the multiplexed data and delivers it up to the MAC.

Other functions of Physical layer: Various handover functions Error detection and report to higher layers Chip rate processing Symbol rate processing Fast Close loop Power control

MAC Layer Data Link Layer MAC controls the flow of packets to and

from the network layer. It sends and receives data from control and user plane

service access points at the RLC layer and sends it to the physical layer.

Ciphering task is performed by the MAC layer. Responsible for traffic volume measurements across the

radio interface. Provide a multiplexing function that results in different logic

channels being mapped onto the same transport channel.

RLC(Radio Link Control) Layer Provide radio link services for use between the UE and the

network. Transfer data in 3 modes:

1. Transparent mode of data transfer – uses only physical layer protocol to transmit or receive data.

2. Acknowledged mode of data transfer – provides a very reliable mechanism for transferring data between two peer RLC entities.

3. Unacknowledged mode of data transfer – In this mode RLC signaling is added to the data to permit a variable relationship between the user of the data and the capabilities of the radio channel.

Provides segmentation and reassembly, which allows the RLC to segment large PDUs into smaller PDUs; concatenation service allows a number of PDUs to be concatenated.

Provides error correction by Automatic Repeat Request(ARQ) system and flow control.

RRC(Radio Resource Control) Layer

Responsible for configuration and control of all the layers that create the radio connection between the UE and the UTRAN(UMTS Terrestrial Radio Access Network).

RRC messages can be grouped into 4 categories: RRC connection management messages, RB control messages, RRC connection mobility messages and RRC measurement messages

Functions: Functions for connection establishment and release, Broadcast of system information, Radio bearer establishment/reconfiguration and release, RRC connection mobility procedures, Paging notification and release, Outer loop power control.

Non-Access Stratum Divided into 2 parts: Control Plane & User plane. Sub layers in Control Plane – GMM(GPRS Mobility

Management),CC(call(connection)control),MM(Mobility Management),SM(Session Management),SS (Supplementary Service)and SMS(Short Message Service).

GMM / SM protocol supports the mobility of user terminal so that the SGSN can know the location of a MS at any time and to activate, modify and deactivate the PDP sessions required by the MS for the user data transfer.

MM controls mobility issues and provides soft handover. CC support services such as call establishment, maintenance and

termination. Sub layers in User Plane – PDCP(Packet Data Convergence

Protocol) and BMC(Broadcast and Multicast Control) protocol. PDCP performs transfer of packet user data and header

compression and decompression of IP data streams. BMC provides support for Cell Broadcast Service(CBS) messages.

TDD & FDD

W-CDMA supports 2 different modes of operation: TDD(Time Division Duplex): In this duplex method, uplink

and downlink transmissions are carried over the same frequency band by using synchronized time intervals. Thus time slots in a physical channel are divided into transmission and reception part.

FDD(Frequency Division Duplex): The uplink and downlink transmissions employ two separated frequency bands each of 5MHz bandwidth for this duplex method. Uplink frequency of 1.92-1.98 GHz and downlink frequency of 2.11 -2.17 GHz.  

Power Control(1/2)The purpose of power control (PC) is to ensure thateach user receives and transmits just enough energy to prevent: Blocking of distant users (near-far-effect) Exceeding reasonable interference levels

Without PC received power levels would be

unequal

In theory with PC received power levels would be

equal

UE1UE2

UE3

UE1

UE1

UE2

UE2

UE3

UE3

Power Control (2/2) Power control can be divided into two parts: Open loop power control (slow power control)

UE transmitter sets its output power to a specific value. It is used for setting initial uplink and downlink transmission powers when a UE is accessing the network.

estimate the path loss from the signal received in DL 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)

Conclusion

3GPP is currently the main standardization body in charge of WCDMA and its evolutions

WCDMA is designed to provide backward compatibility and interoperability for all GSM, GPRS and EDGE switching equipment and applications.

WCDMA has been made compatible with cdmaOne and CDMA2000 systems.

Market share for WCDMA is growing rapidly More than 340 million WCDMA subscribers Fueled by various services such as mobile-TV and VoIP

BibliographyBOOKS 1. WCDMA design Handbook – Andrew Richardson2. WCDMA: requirements and practical design -Rudolf Tanner,

Jason P. Woodard 3. Mobile Computing - Raj Kamal

Websites4. www.sss-mag.com5. www.3g-generation.com6. www.3gtoday.com7. Wikipedia

THANK YOU!!