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CDMA Overview & BSNL Plans

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10/21/2014 1 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

    Shannons Equation

    C= W Log (1+S/N)

    Where C=Capacity (bps)

    W=Bandwidth

    S=Signal Power

    N=Noise Power

    Shannons 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 Walshcode. 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 only2.4 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. 6991toRs. 17200and 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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