CDMA Overview & BSNL Plans

7/27/2019 CDMA Overview & BSNL Plans

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CDMA: Code Division Multiple Access

Large number of transmissions are combined on thesame RF channel at the same time but are

separated by “codes”.

CDMA is a method in which users occupy the same

time and frequency allocations, and are channelized by

unique assigned codes. The signals are separated at the

receiver by using a correlator that accepts only signal

energy from the desired channel. Undesired signalscontribute only to the noise.

A CDMA system uses effective power control process.



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Advantages:-

The main advantages of this technologyare:

1. Fast Network deployment.

2. Reduced service interruptions.

3. Low Maintenance & operational cost.

4. Better system coverage flexibility

5. Higher capacity



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Salient Features of CDMA

• It is an advanced comm. Technology.• It has Anti-jam and security features.

• Large capacity as compared to other Technology

like FDMA and TDMA.• It uses spread spectrum technology

• Better use of multipath



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TECHNICAL PATRAMETERS of CDMA

CDMA Standard IS-95A/B, CDMA 2000, 1x or 3x

Frequency 824-844 & 869-889 Mhz (In India)

824-849 & 869-894 Mhz (ITU Standard)

Access Method CDMA

Duplexing Method FDD

Modulation QPSK/ OQPSK

RF Channel Spacing 1.25 MHz

Voice Coding Algorithm Q-CELP/EVRC

Voice Coding Rate 8K/13 K



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C

D

B

A C

F

G

EB

A

E

G B

D

C

FE

G

F

C E B

D

C

FD

B

A

Frequency Reuse pattern of

7 (FDMA)

Frequency Reuse

In CDMA reuse patterns are not required.

Subscriber in every cell can use the same frequency at the same

time. Subscriber is discriminated from another by the

assignment of a unique code to every conversation.

A

A

A

A A

A

A

AA

A

A

AA

A

A

AA

A

A

AA

A

A

A

AA

A

A

CDMA Frequency

Reuse



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SPREADING SPECTRUM

Shannon’s Equation

C= W Log (1+S/N)

Where C=Capacity (bps)

W=Bandwidth

S=Signal Power

N=Noise Power

• Shannon’s Capacity Equation is basis for spread spectrum.

System with large band width and can operate at very low SNR

level & can provide acceptable data rate per user.

• Therefore in CDMA- All users uses same 1.25 MHz spectrum.

- Each user has unique Digital code identifier.

- Digital codes separate users to avoid interference.



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Spreading Codes

CDMA systems use two types of code sequences:• Orthogonal sequences (Walsh codes).

• Pseudorandom Noise (PN) sequences.

Long codes (242 =4400 Billion)

Short codes (215 =32768)



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Walsh Codes:-

In CDMA the traffic channels are separated byUnique “Walsh” code. These are

(a) 64 codes of 64 Bit Length.

(b) Forwarded traffic channel Codes.(c) All codes are orthogonal to each other.

(d) These codes provide Isolation between

multiple signals transmitted by base stations



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The basic concept behind creation of the code is

as follows:

(a)Repeat the function right

(b)Repeat the function below

(c) Invert function (diagonally)

Fig: Seed 0 0 0 0 0 0 0

0 1 0 1 0 1

0 0 1 1

0 1 1 0



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LONG CODE

(a) 242 Bits polynomials.

(b) Forwarded channel Data (traffic and paging chls) scrambled.

(c) Provides channelizations for the reverse chls.

(d) This code is unique for every subscriber.

(e) It is known as user address mask or user identification.

(f) Subscriber are differentiated as no two same codes are used.

SHORT CODE

(a) This PN sequence is based on 215 characteristics polynomial.

(b) Differentiates cells and sectors.

(c) Identification cells and sectors.

(d) Each cell uses different codes.



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CDMA Channels (IS-95A)

•Forward Link Channels

Pilot Channel

Sync Channel

Paging Channel

Traffic Channel

•Reverse Link Channels

Access Channel

Traffic Channel



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CDMA CHL ARCHITECTURE

Pilot channel (W0)

The pilot is used by the subs unit to obtain initial

system synchronization and to distinguish cell

sites. Every sector of every cell site has a unique

pilot channel.• Transmitted constantly

• Allows the mobile to acquire the system.

• Provides mobile with signal strength comparison.

• Approximately 20% of the radiated power is inthe pilot.

• Has unique PN Offset(215 ) for each cell or sector.



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Sync channel (W32)

Used during system Acquisition stage. Sync chl

provides the subs unit with network informationrelated to cell site identification, pilot transmit

power & cell site PN offset.

• Used by mobile to synchronize with the system

• Transmits sync message with

- Pilot PN offset - System time

- Long PN code - System ID

- Network ID - Paging chl data rate

• Tx at 1200 bps



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PAGING CHLS (W1-W7)

On this chl base station can page the subs unit and it can

send call set-up and traffic chl assignment information.

• Means of communication between base to mobile station.

• Paging CHL data Rates can be 2.4,4.8 or 9.6 KBPS.

• CDMA assignment has 7 paging CHLS.

Provides mobile with

- System Parameter message - Neighbour list

- Access Parameter list - CDMA Channel list

• Used by base station to :

- Page mobile - Transmit overhead information

- Assign mobile to traffic channel



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Access CHLS.

Provides communication from Mobile to base

station when mobile is not using traffic Chl. The

access chl is used for call origination & for

response to pages, orders & registration

requests. It is paired with corresponding paging

chl.(b) Each Access CHL use long PN code.

(c) Base station responds to transmission on aparticular Access CHL.

(d)Mobile responds to base station message byEmitting on Access CHL.

(e) Tx at 4800bps



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Traffic Channels ( W8-W31 & W33-W63)

The traffic chl carries the actual call. That is, thevoice and control information between the subs unit

& base station.

TX upto 9.6kbps on rate set 1 and upto 14.4kbpson rate set 2.



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Rake receiver

CDMA mobiles use rake receivers. The rake receiver essentially a

set of four or more receivers (or fingers). One of the receivers

constantly searches for different multipaths and helps to direct the

other three fingers to lock onto strong multipath signals. It has the

following advantages:

•Reduces the Multipath Fading.

•Used during the Hand off procedures.

Correlator 1

Correlator 2

Correlator 3

Searcher

c

o

m

b

i

n

e

r

CDMA mobile rake receiver



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Power control

CDMA will not work without an effective power control, because of

the near-far problem, fading & varying path loss.Open loop power control:

An original estimate is made by the mobile. Mobile adjusts its trans

power according to changes in its received power from the base

station.

Closed loop power control:

BTS Compares the received power of mobile with the threshold

value & takes the decision for increasing or decreasing the power ofmobile. It also Commands the mobile to adjust the output power

accordingly.



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Data only 2.4 Mbps

RF backward compatible

CDMA2000 1xIS-95A

CDMA2000 1xEV-DO

IS-95B

Evolution of CDMA Networks

Voice, 14.4K Voice, 64K



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Salient Features of CDMA 2000 1x

•Backward Compatibility with IS-95A & IS-95B

•Support for High data rates on same 1x Carrier

•Higher capacity for voice communication

•Increased battery life

•Faster forward Power control (relative to IS-95)

• New Radio Configuration to support high data rates and more

voice capacity.



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Architecture of CDMA 2000 1x Network:



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Architecture of CDMA 2000 1x Network:

CDMA 2000 1x Network Architecture is divided in to

three parts.

•CS-CN (Circuit Switched Core Network)

•PS-CN (Packet Switched Core Network)

•RAN (Radio Access Network)



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Circuit Switched Core Network:

This section is dedicated for voice communication and

also for wireless authentication. This section includes four

parts

MSC (Mobile Switching Center)

HLR (Home Location Register)

VLR (Visitor Location Register)

AUC (Authentication Center)



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Packet Switched Core Network: To provide better connectivity

to the internet a new core network i.e. PS-CN is introduced to the

CDMA 2000 1x network. This section includes four parts

PDSN (Packet Data Serving Node)

AAA Server

Home Agent/ Foreign Agent Server



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RAN (Radio Access Network): As in IS-95 RAN is

composed of number of BSCs & BTSs The CDMA 2000 1x

RAN is enhanced to support a higher no. of users on air

interface or in other words it has a better spectral efficiencyrelative to IS-95. It is also modified to support the new packet

data services on same 1.25 Mhz channel. This is achieved by

software up-gradation at BTS and BSC and addition of a new

hardware unit called Packet Control Function (PCF) at BSC.

The CDMA 2000 1x air interface is very different from IS-95

but still maintains the backward compatibility with IS-95.



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CDMA 2000 1X Deployment

Initially BSNL was using CDMA WLL technology inAccess Network only with limited mobility.

With the time the CDMA technology advanced and BSNL

decided to introduce MSC based CDMA 2000 1xtechnology in the network.

Additionally CDMA 2000 1x technology provides manyvalue added services like packet data up to 144kbps, SMSand VMS.

About 6 to 8 millions lines of CDMA 2000 1x MSC Basedequipment has been commissioned in various circles.



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CDMA 2000 1x EV-DO:

Although IS-2000 is already capable of meeting the 3G data rate requirement of 2

Mbps (By using 3x option) Qualcomm proposed a new standard 1xEV-DO (1x

Evolution for Data Optimized) in March of 2000 as another option that supportshigh-rate data services.

EVDO is optimized for delivering high speed IP wireless data to many mobile and

stationary terminals running multiple applications. EVDO is designed for an

always on user experience.

Salient features of EV-DO

• EV-DO uses both CDMA and TDMA.

• Uses its own dedicated 1.25 Mhz carrier.

• It can support a maximum data rate of 2.4 Mbps in forward link.

• It can support a maximum data rate of 153.6 Kbps in reverse link.

• No power control on forward link is required.

• RF system components may be shared with 1xRTT.



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CDMA 2000 1X EV-DO Deployment

HLR

MSC

BSC/

PCF

PDSN

AAA

InternetBTSDevice

Channel Card

and RF Carrier

Software

Upgrade

• 1xEV-DO leverages from existing 1x core network components, same AAA server and PDSN

• New 3G BSC (BSCB) is required to connect with EV-DO BTS & High capacity PDSS-200

• PDSS-200 is provided on zonal basis.

•Generally 2 E1 are provided to connect BSCB with PDSS.



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CDMA 2000 1x Technology supports the following Value

added services

-Short message Services-VMS

-Internet ( Packet Data up to 144Kbps)

Internet

WLL internet can be accessed in the following ways

-Using FWT

-Using NIC (Network Interface Card)

-Using USB Modem



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Tariff for Data Services using CDMA Technology

(A) Network Interface Card (NIC) : For internet speed up to 144 Kbps.

(B) EVDO Card : Internet speed up to 2.4 Mbps

Tariff for Data services on CDMA 2000 IX by using BSNL Internet Connect Card:

The tariff for this service will be as follows:-

Network Interface Card (NIC) EVDO Card

Registration Charges NIL NIL

Activation Charges 250.00 250.00

Internet connect Card Sale Price 4500.00 6500.00

Alternate to Purchase of Modem

(a) Monthly fixed charges 150.00 200.00

b) Security Charges ( Refundable) 1000.00 1000.00

Fixed Monthly Charges

for accessing Internet only) 250.00 550.00

Fixed monthly charges, free calls, As per plan selected by the customer

unit rate, pulse etc. for voice calls



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EVDO Card



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VALUE ADDITION

BSNL has made provision for following valueadditions in CDMA technology services.

WIN (Installed at Vadodara) CDR BASED BILLING : Billing System of CDMA is

planned to be integrated with CMTS BCCS.

SMSC

UMS OTA (Installed at Kolkata)

PCN

LIS (Installed at Vadodara)



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PDSS, SMSC & UMS are provided at Zonal

Basis.Zone PDSS SMSC/UMS

North Noida Jaipur

West Vadodara Pune

South Bangalore Bangalore

East Kolkata Kolkata



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PRESENT BSNL POLICY FOR

CDMA WLL

Presently CDMA technology is being used to provide

mobility within one SDCA area.

BSNL has got the full mobility license on CDMA WLLunder UASL.

BSNL plans to provide CDMA WLL data services with full

mobility in all cities using 1x EV-DO technology.

BSNL is also providing the prepaid services using CDMA

Technology.



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BSNL is providing solutions for Bank ATMs connectivity

using CDMA with MPLS.

Wireless access to ATM at a cheaper price & also in nonfeasible areas.

Mobile ATM facility can also be provided by using CDMA

technology.



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USO OBLIGATIONS

Rural DELs : Out of total 2642 SDCAs in the

countries, USO, DOT had invited tender for 1687

SDCAs for clearing waiting list. BSNL was allotted 1267 SDCAs for this

purpose. BSNL has planned to clear the waiting

list by extending the WLL COVERAGE in these

SDCAs and giving the connections on demand.



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SUPPORT FROM USO FUND Provision of Rural DELs in 1267 specified

SDCAs allotted to BSNl by USO Fund from

01/04/2005 to 31/03/2007

The front loaded rate varies from Rs. 6991 toRs. 17200 and annual rate varies from Rs. 0

to Rs. 3100. Total likely support from USOFUND is Rs. 600 Cr in next two years.



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THANKS !!

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