MembersAman ShakyaBishal PoudelKrishna Kumar GuptaSandep Gupta

APresentation on CDMA 2000

and IP CDMA

R. Z. Ziemer, Colorado Springs, CO 2May 28-June1, 2001

Why CDMA?• Higher capacity• Improved performance in multipath by diversity• Lower mobile transmit power = longer battery life– Power control– Variable transmission rate with voice activity detection

• Allows soft handoff• Sectorization gain• High peak data rates can be accommodated• Combats other-user interference = lower reuse factors

CDMA Evolution Paths

2Mbps

153.6kbps

CDMA1xRTT

CDMA 1xEV-DV

CDMAIS-95

CDMA1xEV-DO

CDMA3x 5x

2G 2.5G 3G

9.6kbps

1993, the first CDMA standard IS-95 was issued; In 1995, CDMA technology was put into

commercialization in Hong Kong and America on large scale;

In April, 2001, China Unicom began to construct CDMA networks—the largest in the world (about 70Million line now);

At present, CDMA commercial networks are established in about 40 countries or area, almost 20% of all users in the world.

CDMA-Its History & Status

CDMA PCS 1900 MHz Spectrum Usage

Guard Bands

Forward link (i.e., cell site transmits)Reverse link (i.e., mobile transmits)1850 MHz

BTA

BTA

BTA

BTA

BTA

BTA

Paired Bands

MTA BTAMTABTA MTAMTA

1910 MHz

1930MHz

1990MHz

Data Voice

A D B E F C A D B E F C

15 51010 1515151515 555 55

Licensed Licensed

Unlicensed

0

Channel Numbers 299

300

400

699700

800

900

1199 0

299300

400

699700

800

900

1199

CDMA Frequency ChannelAssignment at 800 MHz Cellular

IS-95 Recommends to Start CDMA Deployment with Either the Primary or the Secondary Channel

1

334

667

991

1023

333

666

715

799

716

ChannelNumbers

A Band B Band A’A” B’

1019 37 78 119 160 201 242 283 384 425 466 507 548 589 630 691 777

CDMA A-Band Carriers CDMA B-Band Carriers

8 7 6 5 4 3 2 1 1 2 3 4 5 6 7 9 9 8

* **** Requires frequency coordination with

non-cellular interferers

** Requires frequency coordination with A-band carrier

A Band Primary Channel 283A Band Secondary Channel 691

B Band Primary Channel 384B Band Secondary Channel 777

736

Frequency Reuse

CDMA (IS-95)frequency reuse = 1 TDMA (IS-136)

frequency reuse = 7

Walsh Codes

• 64 Sequences, each 64 chips long– A chip is a binary digit (0 or 1)

• Each Walsh Code is Orthogonal to all other Walsh Codes– This means that it is possible to recognize and

therefore extract a particular Walsh code from a mixture of other Walsh codes which are “filtered out” in the process

– Two same-length binary strings are orthogonal if the result of XORing them has the same number of 0s as 1s

Coding Process on CDMA Forward Channels

WALSH19

BTSPilot Walsh 0

Walsh 19

Paging Walsh 1

Walsh 6

Walsh 11

Walsh 20

Sync Walsh 32

Walsh 42

Walsh 37

Walsh 41

Walsh 56

Walsh 60

Walsh 55

PN OFFSET 116BTS

PN OFFSET 226BTS

PN OFFSET 510BTS

S PN

372

x

x

xPN OFFSET

ANALOG

SUM/MUX PN OFFSET 372

d1 d2

t t t

d3

transmission receivingRaker combination

noise

Rake Receiver (1)

Rake Receiver (2)

Correlator 1

Correlator 2

Correlator 3

Search Correlator

Com

bine

r

To De-Interleaver, Viterbi Decoder

Multipath Delay Components

( 150 ms > Dt > 1ms)

Rake receiver can isolate multipath spaced > 1 chip length.

Rake Receiver (3)

• Handset uses combined outputs of the three traffic correlators “rake fingers”

• Each finger can independently recover a particular PN offset and Walsh code

• Fingers can targeted on delayed multipath reflections, or even on different BTSs

• Searcher continuously checks pilots

Intelligent Vocoder

Power ControlAutonomous power controlOn the Uplink tells the MS to vary it’s transmitted power

inversely with the power level it receive from the BS.

Direct power controlOn the Uplink measures Eb/No at the base station and sends

power Control Bits over the Downlink to the MS to instruct the MS to either increase or decrease its transmit power.

Downlink power controlAttempts to use minimum power needed to meet to a Frame

Error Rate (FER) threshold at the MS s.

Coverage

• The coverage radius is 2 times

of standard GSM.• Coverage of 1000 km2: GSM

needs 200 BTS 's, while CDMA

requires only 50.• Under the same coverage

conditions, the number of BTS

's is greatly decreased

Simple project design & convenient capacity expansion

13

2

4

3

2

4

24

4

1

2

3

1

4

2

31

4

GSM: N=4 Frequency reuse

11

1

1

11 1

11

1

1

1

1

1

1

1

11

1

11

1

Simple Network Planning

CDMA: N=1Frequency reuse

Functions of the CDMA Reverse Channels

• There are two types of CDMA Reverse Channels:– TRAFFIC CHANNELS are used by individual

users during their actual calls to transmit trafficto the BTS.

– ACCESS CHANNELS are used by mobile stations not yet in a call to transmit registration requests, call setup requests, page responses, order responses, and other signaling information

Coding Process on CDMAReverse Channels

• Each mobile is uniquely identified by the User Long Code, which it generates internally.

• All mobile stations transmit simultaneously on the same 1.25 MHz wide frequency band.

• Any nearby BTS can dedicate a channel element to the mobile station and successfully extract its signal.

• Mobile stations also use the other CDMA spreading sequences, but not for channel-identifying purposes.

• Short PN Sequences are used to achieve phase modulation.

• Walsh Codes are used as Orthogonal Modulation to give ultra-reliable communications recovery at the BTS.

Benefits of the cdma2000 1x Standards

• Increased mobile standby battery life (via Quick Paging Channel)

• Total backward compatibility to reuse switch and call processing features

• 2-3 dB better coverage• High speed 153.6 kbps packet data capabilities• cdma2000 1x = 1.25 MHz Radio Transmission

Technology

Example of cdma2000 1x Network

HandOff in CDMA:

CDMA channel Structure• CDMA Forword Channels:

– 64 Walsh codes channels:• 1 paging channel• 1 sync channel• 1 paging channel• Unsed channels up to 6 channels• Traffic channels: 55 channel at least

Forword traffic Channel Generation 8Kb Vocoding

23

24

25

26

27

CDMA Advantages

• Spread Spectrum• Soft & Softer Handoff• Rake Receiver• Variable Rate Vocoder• High quality voice• Power Control• Coverage• Simple Network Planning• Green Handset• Smooth migration to 3G and the operator’s benefit is

protected at the most

Why IP CDMA

• Expensive Transmission Network• Slow provisioning of new services• Complicated Network Architecture• Distributed Operation & Maintenance

Migration to IP CDMA

It occurs in two stages• from legacy circuit-switched MSC based

network solution to Soft switch based solution.

• from Soft switch based solution to IMS based solution.

1.Soft switch based solution• Intended to facilitate a smooth migration of the present Circuit Switched

MSC based CDMA 2000 1x Network to a Network based on IP.• CDMA2000 1x core network based on IP separates services from control

and call from bearer.• It can be interconnected with other CDMA2000 Networks and PSTNs /

PLMNs and is compatible with existing CDMA 2000 1x mobile networks.

Functional elements involved

• Soft switch– Contains emulation for functionality of MSC,HLR & SCP for

IP Based CDMA 2000 1x Core Network.– Provides support for existing Mobile Stations an IP core

network environment.– Also supports the features and capabilities provided in a

legacy network in a manner transparent to the user.

Functional elements involved

• Media Gateway (MGW)– Acts as an Inter working Function between circuit switched and packet

switched networks and provides the interface for the media path conversion between the circuit network and circuit clients, and the packet network and its clients.

– It is responsible for voice and circuit switched data services bearer in the core network, implements service transmission and format conversion within mobile networks or between mobile networks and fixed networks.

– With the help of Soft switch, MGW provides basic services, supplementary services and intelligent services.

Functional elements involved

• Signaling Gateway (SGW)– It provides the necessary interworking of various

elements like MSC, HLR , SCP,MGW, SS7 systems, PSTN etc.

– It converts SS7 signaling in the PSTN/PLMN network to IP packets to be carried over the IP network.

– It transports SS7 messages received from PSTN,PLMN etc over E1 to CDMA soft switch and Media Gateway and it also transports signaling messages (SS7 or RTP) received from RAN(BSC).

Functional elements involved

• IP RAN– The Radio Access Network comprising of BTS and

BSC– supports IP in the backhaul– can directly interface, for signaling, with the IP

Soft switch rather than through the Media Gateway.

2. IMS(IP Multimedia Subsystem) based solution

• IMS (MMD-Multi Media Domain) supports only IP-based signaling and provides support for SIP capable Mobile Stations in an IP core network environment.

• The IMS standards are still evolving and no commercial deployment of IMS-based network is expected.

Features Of IP CDMA

• Soft switch– Separation of the control from bearer– Control and management functions of resources on the

MGW– Access to the IP based RAN in the IP transmission mode– The underlying packet transport technology is Internet

Protocol (IP)– Interfaces & Signaling, Inter Working, Protocols and

Interaction with other IN network elements are as per standard specification referred by3GPP2, IETF, ITU etc.

– Integration with IP Multimedia Sub System (IMS)

Features Of IP CDMA

• Other Features– Lawful Interception• Capturing, monitoring and recording of a specific data

stream.• Filtering and storing call related information for targets

in a separate file, for transferring to Law Enforcement Agencies.

• Interfaces to circuit switched MSC based CDMA Network & PSTN Network– capability to connect with other circuit switched

based PSTN switch / MSCs with an appropriate interface.

– support IETF standards like SIGTRAN, SIP, SIP-T, etc. so as to be easilyinteroperable with other wireless and wireline next generation networks.

• Interoperability– field deployed commercially across multiple

countries and networks with various technologies /vendors of MGW, Soft switch and signaling Gateway, legacy Network etc.

• Billing/Charging– capable of generating CDRs in desired format for

end user billing as well as inter carrier accounting details.

• Network Management System (NMS)– possible to have remote workstations, with

complete GUI tools for operation & management of the system at the remote locations.

– Support interface like SNMP, CORBA, TCP / IP etc., to enable it to work with a remote NMS.

Thank You