alcatel lucent drive test-1 part-2

Drive Test CDMADrive Test CDMA

Created byPulok Sinha (Trainer, ALUMS)

All Rights Reserved © Alcatel-Lucent 2009

( , )09320096525

ObjectivesObjectives

After successful completion of this program, you will be able to D ibDescribe

Multiple Access Approaches.p ppWhat is CDMA.Common Technical Terms in CDMACh l d T i CDMAChannels and Types in CDMAHandoff and typesMS StatesMajor Parameters in CDMA Drive testMajor Windows in Drive test

ll


Call Scenarios

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Multiple Access ApproachesMultiple Access Approaches


What is CDMAWhat is CDMA


What is CDMAWhat is CDMA

Definition:Definition:

Channel access method is Code Division Multiple Access.

CDMA is a Direct Sequence (DS) Spread Spectrum Modulationq ( ) p pTechnique, where in, a narrow band (of less than 10 kHz) userinformation (voice or data) is transmitted over a wide RFbandwidth (of 1.25 MHz); with many users occupying the sameRF transmission band but are separated by what are called“codes”.

Frequency reuse factor is 1 i e only one frequency is useFrequency reuse factor is 1 i.e. only one frequency is use.


Common Technical Terms In CDMACommon Technical Terms In CDMA


Common Technical Terms In CDMACommon Technical Terms In CDMABit, Chip, SymbolBit, Chip, Symbol

A bit is the input data which containinformationinformationA chip is the output of spreading and doesnot contain any information data. A chiprate is 1.2288 Mcpsrate is 1.2288 McpsA symbol is the output of the convolutionencoder, the repetition and the blockinterleaving. One Symbol is representedMultiple Chips

Processing GainProcessing GainggProcessing gain is the ratio of a spreadingrate to a data rate.G= Rc/Rbh


The processing gain in IS-95 system is 128,about 21dB, Rc = 1.2288Mcps & Rb = 9.6Kbps.


Forward Link (DL): Forward Link (DL): the direction from a base station to a mobile stationstation to a mobile station

Reverse Link (UL): Reverse Link (UL): the direction from a mobile station to a base station

Eb/No: Eb/No: Ratio of Transmitted energy per bit (Eb) to Thermal Noise (No), expressed in dB.

Eb/Nt Eb/Nt i f i d bi ( b)Eb/Nt: Eb/Nt: Ratio of Transmitted energy per bit (Eb) to Total Noise (Nt) including thermal, spurious, and interference from other CDMA users, expressed in dB.

Ec/Nt: Ec/Nt: Ratio of Transmitted energy per chip (Ec) to Total Noise (Nt), expressed in dB.


Common Technical Terms In CDMACommon Technical Terms In CDMAPN Sequence: PN Sequence: A Pseudo-random Noise (PN)

sequence is a sequence of binary numbers, which appears to be random but are actually which appears to be random, but are actually not random.

Long Code PN Code:Long Code PN Code:ggThe Long Code is a PN sequence that is2^42 - 1 chips long.It is generated at a rate of 1.2288 Mcps.

The functions of a long code: The functions of a long code: Scrambling the forward CDMA channelgControlling the insertion of a power controlbit.Spreading on the reverse CDMA channel toid tif th bil t ti


identify the mobile stations.

Common Technical Terms In CDMACommon Technical Terms In CDMAShort CodeShort Code

The Short Code is a PN sequence that is 215

h l hchips in length.This code is generated at 1.2288 Mcpsgiving a period of 26.67 msec.

The functions of a short code: The functions of a short code:

This code is used for final spreading of thep gsignalThe CDMA system applies the time offset ofshort PN code to distinguish betweensectorssectors.The minimum PN sequence offset is 64chips, that is to say, 512 PN offsets areavailable to identify the CDMA sectors (215

/64 512)


/64=512).

Common Technical Terms In CDMACommon Technical Terms In CDMAWalsh Code Walsh Code

CDMA defines a group of 64 orthogonalh b l ksequences, each 64 bits long, known as

Walsh Codes.Walsh codes are generated at 1.2288 Mcpswith a period of approximately 52 µs.with a period of approximately 52 µs.

The functions of a Walsh code: The functions of a Walsh code:

These are used to identify users on theforward link.

Th f d h l i h li d bThe forward channel is channelized by aWalsh code and the reverse channel by along code.



Yields Equal no's of 0’s and 1’s

A orthogonal Code

Input Data

Yields all zeros

Yields the input data


Common Technical Terms In CDMACommon Technical Terms In CDMARake receiver:Rake receiver:

Receive set

Correlator 1

Correlator 2 Combiner The combined signal

Correlator 3

Searcher correlator Calculate the time delay and

signal

time delay and signal strength

s(t) s(t)

tt


Common Technical Terms In CDMACommon Technical Terms In CDMARakeRake receiverreceiver::

A rake receiver is a radio receiver designed to counter theA rake receiver is a radio receiver designed to counter theeffects of multipath fading.

It does this by using several "sub-receivers" called fingers.

The RAKE receiver provides for the coherent combination ofmultipath components from a single base station and multiplecells/sectors jointly in a CDMA Handoff scenario led fingers/ j y g

Each finger can independently recover a particular PN offsetand Walsh code

Searcher continuously checks pilots


Channels and TypesChannels and Types


Channels and TypesChannels and TypesPhysical Channels:Physical Channels:

Physical channels are described in terms of a wideband RFchannel and code sequencechannel and code sequence.Each RF channel is 1.2288 MHz wide.For each RF channel, there are 64 Walsh sequences (W0through W63) commonly referred to as CDMA code channels.

Logical Channels:Logical Channels:The channel that carry specific types of information are knownThe channel that carry specific types of information are knownas logical channels.Logical channels in CDMA are divided into two categories:Traffic Channels and Control ChannelsTraffic Channels and Control Channels.− For the forward link : 3 Control/Signaling channels and 1 Traffic Channel

(per user).− For the Reverse Link : 1Signaling Channel and 1 Traffic Channel per user.


g g p


Logical ChannelsLogical Channels::Forward Link Logical Channels:Forward Link Logical Channels:

The Pilot ChannelSync ChannelP i Ch lPaging ChannelsTraffic Channels

Reverse Link logical ChannelsReverse Link logical ChannelsAccess Channels andTraffic ChannelsTraffic Channels.


Channels and TypesChannels and TypesForward Link and Walsh Code Assignment:Forward Link and Walsh Code Assignment:



Pilot Channel:Pilot Channel:

Pilot channel ser es as beacon for the sectorPilot channel serves as beacon for the sector

Always transmitted on Walsh code 0.

The Pilot channel provide mobile handset initial systemsynchronization and timing of forward Channel.

MS gets the frequency and phase tracking of signals from theMS gets the frequency and phase tracking of signals from thecell site.

Pilot channel is just the PN short code with specific offset withno information as all 64 bits are 0.

Pilot Channel provides a means for signal strengthcomparisons between base stations


comparisons between base stations.

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Synchronization Channel:Synchronization Channel:Sync channel carries system timing and system configurationSync channel carries system timing and system configurationinformation.

Always transmitted on Walsh Code 32.

Sync channel provides cell site identification, pilot transmitpower, and the pilot pseudo-random (PN) phase offsetinformation.

Sync channel incorporates in 80 ms super frame structure;each super frame contains 96 bits , yielding a data rate of (96bits/80 ms) = 1,200 bps.

Each superframe contains 3 sync channel frames of equallength and duration of 26.66 7ms .

This means that they align with the timing on the Pilot


This means that they align with the timing on the Pilotchannel.

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Paging Channel:Paging Channel:

The paging channel is used to send control information.

The basic paging frame is 20 msec.

4 frames are grouped to form a slots. A slot is 80 msec.

Slots are grouped into cycles. A cycle consists of 2048 slots( l d ti 163 84 )(cycle duration 163.84 s) .

There may be one to seven paging channels per sector eachmobile only monitors one paging channel

Successful accesses of Paging Channel are normally followedby an assignment to a dedicated traffic channel.



Forward Traffic Channel:Forward Traffic Channel:

Forward traffic channel carries the actual phone call and carries the voice and mobile power control information from the base station to the mobile unit.

Assigned dynamically, in response to MS accesses, to specific MS

l d fAlways carries data in 20 ms frames.

Carry variable rate traffic frames, either 9600, 4800, 2400 or 1200 bpsp

The 800 bps reverse link power control sub-channel is carried on the traffic channel



Access Channel:Access Channel:

Access Channel is used by MS to initiate a call or to respond a “page”.

Access Channel is used in reverse linkAccess Channel is used in reverse link.

An Access Channel is selected randomly by the mobile unit from the total number of access channels available from the

ll/serving cell/sector.

Access Channels are identified by a distinct “Access Channel Long PN Code”.g

Registration is done on Access Channel.



Reverse Traffic Channel:Reverse Traffic Channel:

Reverse traffic Channel is identical to forward traffic channel in function.

Each Traffic Channel is identified by long PN code which is Each Traffic Channel is identified by long PN code which is unique

Apart from the traffic i.e. speech data, signaling information l ff h lare also sent in Reverse Traffic Channel

.


Handoff and TypesHandoff and Types


Handoff and TypesHandoff and TypesHandoffHandoff

Handoff is transfer of services of a mobile station from onebase station to another.

Handoffs are initiated and terminated as a result of the pilotpsignal strength as measured by the mobile unit in terms ofEc/Io.

Handoff Can be Classified as− Idle Handoff− Traffic handoff


Handoff and TypesHandoff and TypesIdle HandoffIdle Handoff

Th t f t f i ti f th P i Ch l fThe act of transferring reception of the Paging Channel fromone base station to another, when the mobile station is in theMobile Station Idle state.

Idle handoff occurs in following condition

− Deterioration in reception level− Another pilot is stronger by a certain level.


Handoff and TypesHandoff and TypesTraffic HandoffTraffic Handoff

Th t f t f i h i f b t ti tThe act of transferring speech services from one base station toanother, when the mobile station is in the Traffic channel state(i.e. call is going on).

Traffic Handoff can be further subdivided into−Soft Hand-off

S ft H d ff−Softer Hand-off−Hard Hand-off


Handoff and TypesHandoff and TypesSoft HandoffSoft Handoff

Th bil i t ith lti l BS' d i thThe mobile communicates with multiple BS's during thehand-off.The different BS's links act as diversity receptionCDMA ft h d ff i d i b th h d tCDMA soft handoff is driven by the handsetHandset continuously checks available pilotsHandset tells system pilots it currently seesHandset assigns its fingers accordingly


Handoff and TypesHandoff and TypesSofter HandoffSofter Handoff

H d ff b t t t i llHand-off between two sectors in same cellThe mobile communicates with two sectors during the hand-

offSi l bi i i d t th hi l l i k iSignal combining is done at the chip level using rake receiver

Hard HandoffHard HandoffHard HandoffHard Handoff

Hand-off to a BS controller that does not support soft hand-offCDMA t CDMA diff t f i− CDMA to CDMA on different frequencies

− CDMA to CDMA on different bands− CDMA to analog (AMPS)


Pilot PollutionPilot Pollution

It is defined as the presence of more than three pilots having significant power.

Leading to good receive power but poor Ec/Io.

Effects of Pilot Pollution are as follows─ High FER─ Poor Hand-off─ Increase Drop Calls


MS StatesMS States


MS StatesMS StatesMS Call Processing StatesMS Call Processing StatesWhen a mobile unit is powered on, it first performs CDMA carrierselection d b i f th f ll i t tselection and can be in one of the following states.

In the system initialization state, acquires the pilot channeland the sync channel, obtains the system time and systemconfiguration.In the system idle state, acquires the paging channel andconstantly monitors it for system parameters and messages or

d f th b t tiorders from the base station.In the system access state, gains access to an access channelin order to communicate with the base station for respond to apage message register authenticate or originate a callpage message, register, authenticate, or originate a call.In Traffic Channel State, speech communication is done onforward and reverse Traffic Channels.


Major Parameter in CDMA Drive TestMajor Parameter in CDMA Drive Test


Major Parameter in CDMA Drive TestMajor Parameter in CDMA Drive TestEc/IoEc/Io

Ratio of Transmitted energy per chip (Ec) to Total Noise including selfRatio of Transmitted energy per chip (Ec) to Total Noise including self interference (Io), expressed in dB

Ec is the energy of a single sector’s Pilot

Io is the sum of all the signals reaching the mobile.

Ec/Io is the important indicator for network performance

If the pilot of a certain sector is weak, Traffic Channels of that sector are also weak

Bad Ec/Io can indicate problems like pilot pollution, forward link interference (indicate neighbor list problems).

Ec/Io also indicate traffic load at the sector


/

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Major Parameter in CDMA Drive TestMajor Parameter in CDMA Drive TestFER:FER:

FER stand for Frame Erasure Rate

FER is an excellent call quality “summary” statistic

FER is the end-result of the whole transmissionlink• if FER is good, then any other problems aren’t

having much effect• if FER is bad – that is indication of a problem


Major Parameter in CDMA Drive TestMajor Parameter in CDMA Drive TestMobile Receive Power:Mobile Receive Power:

Mobile Receive Power expressed in dBm.Mobile Receive Power expressed in dBm.

Measurement includes all RF signals in the carrier bandwidth, not just RF signals from the serving BTSnot just RF signals from the serving BTS

Receive power is important,

− too little receive signal (-100 or weaker) would leave to much noise in the signal , bad FER and other problems.

− too much received signal (-35 dBm or higher) could drive thetoo much received signal ( 35 dBm or higher) could drive thephone’s sensitive first amplifier into overload, causing codedistortion received CDMA Signals


Major Parameter in CDMA Drive TestMajor Parameter in CDMA Drive TestMobile Transmit Power:Mobile Transmit Power:

Mobile Transmit Power the actual RF power outputMobile Transmit Power the actual RF power outputof the handset transmitter.

Maximum handset transmit power is 23 dBm.

Mobile Transmit Power is indicator for Reverse linkinterference. If only this parameter is bad, itmeans there is external reverse link interference.

Typical Tx power+23 dBm in a coverage hole0 dBm near middle cell0 dBm near middle cell-50 dBm up close to BTS


Major Parameter in CDMA Drive TestMajor Parameter in CDMA Drive TestTransmit Gain AdjustTransmit Gain Adjust

S f ll l d l t l d f th BTS Sum of all closed-loop power control commands from the BTS since the beginning of the call

TXGA i l t d t TXPO d i i bTXGA is related to TXPO and is given byTXPO = -(RX dBm) - C + TXGAC = +73 for 800 MHz systems

= +76 for 1900 MHz systems y

The more positive the gain adjust is, the greater the possibility of reverse link noise rise

Range from -25 to 25


Major Parameter in CDMA Drive TestMajor Parameter in CDMA Drive TestConclusion:Conclusion:

M bil R i P d M bil T it th Mobile Receive Power and Mobile Transmit power are the indicator for coverage signal.

If MS R i d E /I h k l it h th t th If MS Receive power and Ec/Io has weak value it show that the coverage at that area is weak.

/ d h d f ll fEc/Io and FER are the indicator for call performance.

Weak Ec/Io will be followed with weak FER. It means there is problem


Major Parameter in CDMA Drive TestMajor Parameter in CDMA Drive TestAcceptable values:Acceptable values:

Ec/Io

>= -6 VERY GOOD

>= -9 to <= -6 GOOD

FER

< 1 VERY GOOD

>= 1 to <=2 GOOD

>= -13 to <= -9 OK

>= -15 to <= -13 POOR

<= -15 VERY POOR

>= 2 to <=3 OK

>= 3 to <=5 POOR

> 5 VERY POOR

Mobile Tx Power

<-12 VERY GOOD

>= -12 to <= -5 GOOD

Mobile Rx Power

>= -45 VERY GOOD

>= -65 to <= -45 GOOD

>=-5 to <=8 OK

>= 8 to <= 18 POOR

>= 18 VERY POOR

>= -85 to <= -65 OK

>= -90 to <= -85 POOR

<= -90 VERY POOR


Major Windows in Drive TestMajor Windows in Drive Test


Radio ParameterRadio Parameter


Radio ParameterRadio ParameterRF MODE: Gives one of the mode that is

in use0: Analog0: Analog1: CDMA cellular2: CDMA PCS3: Sleep mode4 GPS4: GPS5: 1xEV-DO

Active Set Ec/Io sum:Total signal strength (Ec/Io in dB) for allTotal signal strength (Ec/Io in dB) for all

active set members. The summing isdone in the mW domain.

Range: -32…0 dBge 32 0 dRx Power:Received signal power. Valid for both 1x

and EV-DO.


Range: -120…10 dB

Radio ParameterRadio Parameter

Tx Power:Tx Power parameter Valid for both 1xTx Power parameter. Valid for both 1x

and EV-DO.Range: -127…36 dB

Tx Adjust:Tx Adjust power control parameter.

Valid for both 1x and EV-DO. Equal toClosed Loop Adjust parameter when inClosed Loop Adjust parameter when inEV-DO mode.

Range: -128…127 dB

FER Total [%}:Frame error rate calculated over all

forward channels.R 0 100%


Range: 0…100%

Radio ParameterRadio ParameterFER FCH [%]: Frame error rate on the FCH(Fundamental Channel).( )Range: 0…100%

FER SCH0 [%]:FER SCH0 [%]:Frame error rate on the SCH(Supplemental Channel 0).Range: 0…100%g

FER SCH1 [%]:Frame error rate on the SCH1(Supplemental Channel 1).Range: 0…100%


Active, Candidate and Neighbor SetActive, Candidate and Neighbor Set


Active, Candidate and Neighbor SetActive, Candidate and Neighbor SetThese Windows Give the List of BaseStation sectors for

• Active Set,• Candidate Set and• Neighbor set

Respective PN Offset, Band,Channel, Ec/Io, etc. for each sectors.

These are use in the process ofHandover.


Active, Candidate and Neighbor SetActive, Candidate and Neighbor SetActive Set

The active set contains the pilots ofthose sectors that are actively

i ti ith th bilcommunicating with the mobile ontraffic channels.If the active set contains more thanone pilot, then the mobile is

i t i i ti ith llmaintaining connection with allthose sectors on separate trafficchannels.The active set can contain at least sixil tpilots.

Candidate SetCandidate set contains pilots whoseEc/Io are sufficient to make themh/o candidates.The candidate set can contain atleast six pilots


least six pilots.

Active, Candidate and Neighbor SetActive, Candidate and Neighbor SetNeighbor SetIt contains those pilots that are in the

neighbor list of the mobile’s current neighbor list of the mobile s current serving sector.

Neighbor set can contain at least 20 pilots.


Serving WindowServing Window


Serving WindowServing WindowRF MODE: Gives one of the mode that is in use

0: Analog0: Analog1: CDMA cellular2: CDMA PCS3: Sleep mode4 GPS4: GPS5: 1xEV-DO

RF Channel No: Gi h R Ch l i d di Gives the RF Channel no. in use depending

upon the band class (0 ... 1023)

Band:Gives the band in which system isGives the band in which system is

operating.Country ID:Shows the Mobile Country Code, MCC.


For India MCC is 405.

Serving WindowServing WindowNetwork ID:It gives the Network Identification (NID),

number of network operator. This fieldpuniquely identifies a network within acellular system. It is 16 bit number.

Ranges : 0-65535

System ID:It shows System Identification (SID).

This field uniquely identifies theq ycellular system. System IdentityNumber (SID) includes 15 bits.

Ranges from 0-65535

Base Id:This field conveys the base station

identification number


identification number.Ranges : 0-65535

Serving WindowServing WindowCDMA Rx State:In which State the mobile is. One of:•“Entering CDMA”g•“Sync Channel”•“Paging Channel”•“Traffic Channel Initialization”• “Traffic Channel”• Traffic Channel•“Exit”

Searcher Window A:Size of search window used for pilots inSize of search window used for pilots inthe active set.Ranges: 0 - 15

Searcher Window N:Size of search window used for pilots inthe neighbor set.R 0 15


Range: 0 – 15

Serving WindowServing WindowSearcher Window R:Size of search window used for pilots inthe remaining set.R 0 15Range: 0 – 15

T-Add:Pilot detection threshold, if Ec/Io of a/pilot is greater than the pilot detectionthreshold, Pilot will be added to thecandidate set.R f 32 0 dBRanges from: -32 ... 0 dB

T-Comp:Active set versus candidate setcomparison threshold, MS transmit aPilot Strength Measurement Messagewhen the strength of a pilot in theCandidate Set exceeds the threshold.


Candidate Set exceeds the threshold.Range: 0…8 dB

Serving WindowServing WindowT-Drop:Pilot drop threshold, Pilot is removedfrom candidate set and placed in thepneighbor set if the strength of that pilotdrops below the pilot drop threshold.Ranges from: -32 ... 0 dB

T – T Drop:Drop timer value in seconds. After apilot drops below T-Drop and remain forp p pT – T Drops time, then if the pilot ismember

• the active set a pilot strengthmeasurement message is issuedmeasurement message is issued• the candidate set, this pilot is movedto the neighbor set.

Range: 0 1 s 319 s


Range: 0.1 s ... 319 s

Call ScenariosCall Scenarios



Good Call ScenarioGood Call Scenario

Low forward FER

Receive power > -100dBm

Good Ec/Io (> -10 dB)

Normal Transmit Gain Adjust

Transmit power < +20dBm

Good MessagingGood Messaging



Bad Coverage ScenarioBad Coverage Scenario

High forward FERHigh forward FER

Low receive power (<-100 dBm)

Low Ec/Io (< -10 dB)

Higher-than-normal Transmit

Gain Adjust

Higher-than-normal transmit

power (> +20 dBm)

Poor messaging on both links


Call ScenariosCall ScenariosForward Link Interference Forward Link Interference ScenarioScenario

High forward FER

Good receive power (> -100 dBm)

Low Ec/Io (< -10 dB)

Higher-than-normal Transmit g

Gain Adjust

Normal transmit power (< +20 p (

dBm)

Poor forward link messaging


Poor forward link messaging


Reverse Link Interference ScenarioReverse Link Interference Scenario

Good forward FER

Good receive power (> -100 dBm)

Good Ec/Io (> -10 dB)

Higher-than-normal Transmit Higher than normal Transmit

Gain Adjust

Higher-than-normal transmit Higher than normal transmit

power (< +20 dBm)

Poor reverse link messaging


Poor reverse link messaging

QuestionsQuestions


alcatel lucent drive test-1 part-2

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