Download - CDMA Parameters & Optimization

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Motorola Confidential Proprietary 2

CHAPTER 1 INTRODUCTION 5

1.1 Scope 5

1.2 Description 5

CHAPTER 2 FORWARD POWER CONTROL PARAMETERS 6

2.1 Motorolas CDMA Forward Channel Power Control Execution 6

2.2 Parameter Impacts on System Performance 13

2.2.1 Forward Link Power Control For the 8 kHz Vocoder 13

2.2.2 Forward Link Power Control for the 13 kHz Vocoder 13

2.3 Parameter Descriptions 15

Customer Changeable Parameters - FER Targets 15

Fixed Parameters 15

CHAPTER 3 REVERSE LINK POWER CONTROL 19

3.1 CDMA Reverse Channel Power Control Execution 19

3.1.1 Closed Loop Reverse Power Control 20

3.1.2 Reverse Power Control Algorithm 22

3.2 Parameter Impacts on System Performance 25

CHAPTER 4 CELL SIZE PARAMETERS 28

4.1 Parameter Impacts on System performance 28


CHAPTER 5 HANDOVER PARAMETERS 31

5.1 Handover Types 31

5.1.1 Handover Modes 325.1.2 Inter-CBSC Soft Handoff 32

5.1.3 Fast Pilot Shuffle 34

5.1.4 Practical Considerations 34


CHAPTER 6 ACCESS AND SETUP PARAMETERS 39


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6.1. Idle Parameters 39

6.2 Access Parameters 39

6.3 Setup Parameters 41

CHAPTER 7 MIGRATION TO A NEW SOFTWARE RELEASE 46

CHAPTER 8 FIELD OPTIMIZATION WORK CATOGORIES 48

CHAPTER 9 FIELD OPTIMIZATION PROCEDURES 51

9.1 Common Problems with General Optimization 51

9.1.1 No Dominant Pilot 51

9.2 Unique Optimization Cases 52

9.2.1 Origination and Handoff to Far (>4 miles) Away Sites 52

9.2.2 Hard Handoff Optimization 529.2.3 Controlling Soft Handoffs 55

9.2.4 2nd Carrier Implementation 60

CHAPTER 10 N-WAY AND YOU 63

10.1 Background 63

10.1.1 Pilot Dominance 63

10.1.2 MM Handoff Processing 63

10.1.3 Complex SHO 63

10.2 N-Way Components and Algorithms 64

10.2.1 Enable vs. Disable 6410.2.2 Constraint Tables 64

10.2.3 Pilot Dominance 66

10.2.4 MM Filtering 69

10.3 Migration 77

10.3.1 Step 1 - Must Check 77

10.3.2 Step 2 Must Do 77

10.4 Performance Trends 79

10.4.1 Complex Off 80

10.4.2 RFLoss Set 80

10.4.3 SHO Factor Set 80

10.4.4 BTS Shuffle (MR sc991274 and sc994314) 81

10.5 Interaction with Other Features 81

10.6 Call Detail Logs (CDLs) 83

CHAPTER 11 WILL SYSTEMS 83


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Chapter 1 Introduction

1.1 Scope

This purpose of this document is to provide the reader with sufficient information to optimize aCellular or PCS CDMA system through the modification of RF system parameters.

The document divides the parameters into the following five major groups:

Forward Power Control Parameters Reverse Power Control Parameters Cell Size Parameters Handover Parameters Other Customer Adjustable parameters.

Finally, this document will present recommended Field Optimization Techniques along with atrouble-shooting chart. For a more basic primer on CDMA refer to

http://www.pamd.cig.mot.com/~sfdez/cdma.net.ops.pdfwhich is a 260 page presentation by

Antonio Shappley.

1.2 Description

There are three categories of parameters. First, are the Customer Changeable Parameters that can

be adjusted through the system design and field optimization steps. These typically are handoff

parameters and forward ERP. Second, are the Customer Changeable Parameters that are difficult

to analyze in the field and require a calibrated laboratory evaluation to obtain repeatability. These

typically include the Power Control parameters. Finally, there is the category of parameters that

should not be changed by the customer.


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Chapter 2 Forward Power Control Parameters

2.1 Motorolas CDMA Forward Channel Power Control Execution

Introduction

The purpose of forward channel power control is to minimize the amount of power transmitted to

a particular mobile station on the forward link. Minimizing power in a CDMA system reduces

interference and thus increases forward channel capacity. However, there is a trade-off between

this forward channel capacity and the forward link voice quality that mobile stations will

experience. The power control algorithm must balance power against acceptable voice quality.

The CDMA Air Interface Spec, IS-95A / J-STD-008, provides a mechanism for forward power

control but does not specify the algorithm for the infrastructure to implement. IS-95A / J-STD-

008 allows the infrastructure to control how a mobile station generates and transmits Power

Measurement Report Messages. This message specifies the number of frame errors a mobile

station has experienced. The mobile station can be directed to generate this message periodically

and/or when an error threshold is reached.

This note does not describe power control algorithm improvements that will be implemented in

future code releases.

Algorithm Overview

The basic idea of the algorithm is that the infrastructure will periodically reduce a traffic channelsforward gain setting. Reducing the gain has the effect of reducing the power delivered to a

mobile station. At some point, the infrastructure may reduce the gain to a point where mobile

station voice quality will soon be degraded. The mobile station will generate and transmit the

Power Measurement Report Message (PMRM) specifying the number of frame errors received

and the total number of frames over which these errors occurred. This essentially provides a short

term FER for the forward channel to the infrastructure.

The infrastructure equipment receives the PMRM and determines that the error threshold has

been reached. The infrastructure then increases the gain to all forward links corresponding to the

given mobile station, restoring FER to an acceptable level, thus preserving voice quality. The

infrastructure then restarts the periodic gain reductions after a specified delay.

See Figure 1for a graphic representation.


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Forward Power Control Illustration

Forward Gain Setting

Time (frames)

Infrastructure periodically steps

down forward gain settingMobile station measuresexcessive frame errors, sendsPMRM

PMRM received,gain setting increased

Figure 1.

There are several parameters which control the behavior of the algorithm. The Mobility Manager

(MM) and Operations and Maintenance Center Radio (OMCR) are responsible for provisioning

and downloading these parameters. All of the Forward Power Control (FPC) parameter settings

were derived by analysis, simulator results, and lab/field tests. Motorola does not recommend

that the FPC parameters be changed without careful consideration and consultation withMotorola. Motorolas goal is have a generic set of FPC parameters that work for all systems.

Current Forward Power Control lab testing may result in some changes to the parameters to

enhance capacity while maintaining quality.

Gain Settings

The algorithm uses minimum gain settings which prevents the power to a mobile station from

falling below a certain level. The reason for doing this is to mitigate the stop sign effect. The

stop sign effect is when a mobile station comes to rest in a good coverage location, it may allow

its power level to drop significantly. When the mobile station resumes motion, its power

requirements will increase faster than the forward channel power control loop can deliver. The

minimum gain is therefore a trade-off between minimum gain and forward link voice quality.

The algorithm allows the gain floor and ceilings to be set as a function of the number of forward

links (i.e. the soft hand-off state). Due to the diversity benefit of soft hand off exceeding the


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degradation caused by the additional interference, 3 way gain settings would be lower than 2 way

gain settings, and the 2 way gain settings would be lower than the 1 way settings.

The following equations below show the desired relationship between Page and Sync power to

Pilot power. These ratios are determined based on analysis and simulations of idealized and non-

idealized (XLOSS and measured pathloss data) systems with verification through field trials. Thevalues were chosen to minimize the interference caused by the paging and sync channel, in order

to maximize forward link capacity while maintaining adequate paging and sync channel coverage.

Ppage(9600) = 0.75 * Ppilot

Ppage(4800) = 0.40 * Ppilot

Psync(1200) = 0.10 * Ppilot

where

Ppilot is pilot power at the top of the frame1

Ppage is the page power at the top of the frame

Psync is the sync power at the top of the frame

The pilot, page, sync, and traffic channel powers are set by setting corresponding digital gain

levels that are proportional to voltage. Hence, we have the relationship:

Ppage =Gpage

Gpilot

2

Ppilot

Ptch =Gtch

Gpilot

2

Ppilot

For example, the increase in TCH power could be determined from a TCH gain increase by

Ptch2 =Gtch2

Gtch1

2

Ptch1 =Gtch1+ x

Gtch1

2

Ptch1 =x

Gtch1+1

2

Ptch1

where

Gtch1 is the traffic channel gain of mobile k before a gain increase

Gtch2 is the traffic channel gain of mobile k after the gain increasex is the traffic channel gain increase

The dynamic range of a TCH can easily be derived by

1Frame refers to the Site Interface Frame in a SC9600 system and the Base Transceiver Site for SC60X,

SC24X0, and SC4850 systems.


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Ptch_ max =Gtch_ max

Gpilot

2

Ppilot

Ptch_min =Gtch_min

Gpilot

2

Ppilot

Where Gtch_max = 127 (currently) and Gtch_min = 1

We use fixed pilot gain settings and do not vary them with traffic load. Fixed pilot gain settings

are based on designing to a fully loaded system with the constraint that pilot Ec/Io is acceptable

everywhere in the system.

PMRM Message Description

The Power Measurement Report Message (PMRM) is sent by the mobile to serving base stations

periodically (every PWR_REP_FRAMES) to indicate its current quality level and/or sent non-

periodically to indicate that the number of bad frames exceeds a threshold

(PWR_REP_THRESH) in a time window which is at most PWR_REP_FRAMES long (see

pertinent sections in IS-95A / J-STD-008).

PWR_THRESH_ENABLE =1 - enable threshold method for sending PMRM message

PWR_PERIOD_ENABLE =0 - disable periodic method for sending PMRM message

PWR_REP_FRAMES =9 (corresponding mobile parameter TOT_FRAMES)

PWR_REP_THRESH =3 (corresponding mobile parameter BAD_FRAMES)

PWR_REP_DELAY = 3 - four times this value (in terms of frames) is the time the mobile

waits after sending in a PMRM message. This delay prevents

repeatedly sending the message should the mobile be in a bad

location such that it gets a string of Frame erasures.

General

It is important to understand the definition of a bad frame on the forward link since this drives

forward power control. A Bad Frame is indicated when a 9600 baud frame is detected but CRC

fails, frame rate determination is not possible, or quality thresholds in rate determination are notmet. See IS-95A, 6.1.3.3.2 / J-STD-008 2.1.3.3.2 for more details.

Full rate frames have higher FER than lower rate frames due to PCB puncturing. This effects

power control parameter optimization. That is, we tend to shoot for lower than 1% composite

FER to obtain a desired full rate FER of 1%.


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Care must be taken in setting the parameter values that affect how the mobile station generates

Power Measurement Report Messages (PMRMs). It is possible to cause the mobile to send this

message every 5 frames (every 100 ms) in periodic mode. Not only is this likely to significantly

degrade reverse link voice quality, but no additional information is being sent.

This algorithm does not presume that PMRMs are being generated in either the threshold orperiodic modes. Anytime a PMRM is received, the number of errors is compared with a

threshold. If the threshold is reached, the forward gain settings are increased.

Note that if threshold reporting is turned on, the parameter FwdPwrThresh must be set to be less

than PwrRepThresh. If it is not, the infrastructure will never detect excess errors and

consequently the forward power control algorithm will not work.

The Power Measurement Report Message is sent when the number of Frame Erasures at the

mobile exceeds a threshold PwrRepThresh in a window PwrRepFrames long. An equation can be

derived which predicts the mobiles FER based on current forward power control parameters

which is given in Figure 2.0 below.

Example of Motorola's IS-95A / J-STD-008 FPC

1% FER

Gain

o

o oo

o

o oo

stepDown(=2)stepUp(=20)

deltatime (=25)

FE

deltatime*(stepUp/stepDown)

time (frames) -->

PwrRepDelay

113 11312

PwrRepFrames

StepDownDelay(=50)

250

FER= PwrRepThresh/[deltatime*(stepUp/stepDown)+MAX(PwrRepDelay,StepDownDelay)]

Equation

dP = 20 log (1 + stepUp/Gtch_current)

Figure 2.0.

The forward link FER equation given in Figure 2.0has been verified in the lab to be accurate for

a static channel and for a Rayleigh channel for a smaller range of settings. The equation noted

below can be used to calculate a predicted FER given a steady state channel (same speed, delay

spread, etc.).


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FER=Pwr RepThresh

deltatime stepUp

stepDown

+ MAX Pwr RepDelay,StepDownDelay( )

It was found that the equation is more accurate when the numerator is modified to account for the

actual delay in applying the forward gain correction. Note that this equation is not meant to be

used as the sole method of choosing forward power control parameters but is part of a process

based also on simulations, lab tests, and field tests to determine the best possible parameters and

gain settings.


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Forward Power Control in different SHO States

When an IS-95A / J-STD-008 mobile originates, its initial forward link power is set based on

either the paging channel gain (PchGain) or the maximum 3-way gain (MaxGain3Way) whichever

is larger. After the mobile has changed hand-off state (gone into 2 or 3 way soft/softer hand-off)and returns to the single link state its maximum allowed gain is the maximum 1-way gain

(MaxGain1Way). The assumption here is that if the system is designed and operating properly

then the MaxGain1Way gain can be less than the origination gain setting because the mobile will

go into soft handoff when ever it runs into a high interference area. That is, it is assumed that all

high interference areas coincide with soft or softer hand-off regions and there are no coverage

holes that would be mitigated by restricting the 1-way TCH gain to the origination gain level

instead of the maximum 1-way gain. Figure 3.0below is a state diagram describing forward

power control.

The forward link gain of a mobile will change depending on soft handoff transitions that occur.

Prior to R6, the gain would jump to the nominal level whenever a handoff transition would occur.As of release six, when a soft add occurs (a channel element is added), the gain is set to the nom

value for the number of links. When a soft or softer drop or softer add occurs, the gain is set to

nom if its current value is greater than the nominal value or remains the same if the current value

is less than nom. The effects will be an increase in forward link capacity because mobiles will ride

at a lower average gain level and an increase in PMRM rate due to the gain not being bumped up

as often automatically.

State Diagram of Forward Power Control

TCH Gain UpdateGminTchGainGmax

ORIG.

1-way 2-way 3-way

Gmin=MinGain1WayGmax=MAX(PchGain,MaxGain3Way)

Gtch=MAX(PchGain,MaxGain3Way)

Gmin=MinGain2WayGmax=MaxGain2Way

Gmin=MinGain3WayGmax=MaxGain3Way

NomGain1WayTchGainMaxGain1WayGmax = MaxGain1Way

GminTchGainGmaxTCH Gain Update

A=NomGain2WayTchGainMaxGain2Way (softer)=NomGain2Way (soft)

A B

TCH Gain Update

B=NomGain3WayTchGainMaxGain3Way (softer)=NomGain3Way (soft, soft-softer)

NomGain2WayTchGainMaxGain2Way

GminTchGainGmax

(1) Wait OrigDelay frames before reducing TCH Gain every deltatime frames by StepDown units on Origination

(2) Increase TCH Gain by StepUp units whenever a PMRM message is received.

(3) Wait StepDownDelay frames after StepUp before continuing with TCH Gain reduction every deltatime frames

(4) The TCH Gain must fall inside limites based on n-way state or state transition

Figure 3.


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Fast Power Down on Origination

In order to reduce the forward link power from the OrigGain more quickly, release six adds a fast

power down on origination feature. If no soft handoffs have occured after OrigDelay expires, the

gain will be reduced immediately to NomGain1Way then reduced further in steps of twiceStepDown. This process will continue until the MinGain1Way is hit, the mobile generates a

PMRM, or a soft handoff occurs. The benefit from this feature will be seen most from mobiles

that do not enter into soft handoff immediately following origination such as stationary or

pedestrian traffic or WiLL users.

2.2 Parameter Impacts on System Performance

2.2.1 Forward Link Power Control For the 8 kHz Vocoder

The explanation of the power control execution is shown below (from a joint technical meetingnote). There are no suggested field changeable forward power control settings. The default gain

settings have been set so that capacity is maximized while individual frame erasure rates are still at

an average of 1%. Operators might be willing to trade capacity in the early stages in order to

have lowered frame erasures rates in marginal coverage or multiple pilot zones. Keeping this in

mind, a few of the effects of changing the forward power control parameters will be explained.

To help control bursts of errors the MaxGain1-2-3 way settings can be changed to allow the

Power Measurement Report Message (PMRMs) to increase the gain to the maximum of 127.

The effects of this change would:

Decrease the FER rate when multiple PMRMs are sent in a row Increase the overall system interference Reduce call drop rate (for a lightly loaded system) Provide the high Eb/No that the mobile requires for non-optimal conditions

The combination of StepUp/StepDown can be changed to effect the overall FER. The step up is

currently 20, the step down 1 and delta time 50. Increasing delta time will allow more time

between PMRMs and will lower the FER in areas that are covered/optimized. For a system

with limited forward coverage the increase in forward power will create coverage holes prior to

reverse link rise problems. System designs that are marginal in terms of the forward link, such

that raising forward power and forward TCH gain should be prepared to add cells in order tocompensate for the coverage holes that will appear with larger user densities.

2.2.2 Forward Link Power Control for the 13 kHz Vocoder

Erasure Indicator Bit (EIB)


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Specific to Rate Set 2 only is the Erasure Indicator Bit. EIB is effective as of release seven and

works in addition to the PMRM method of increasing the forward channel gain. The MCC sends

the EIB to the transcoder. If the call is in soft handoff, the XC performs its selector function

where each EIB must be an erasure for the outcome to be an erasure. The XC then sends the

selected EIB to the MCCs on the next forward frame. If the EIB is an erasure, the forward gain

will be increased by StepUp. The effect of EIB will be to speed up the forward power control.


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2.3 Parameter Descriptions

Customer Changeable Parameters - FER Targets

The FER targets can be changed by the customer in order to get a higher capacity while trading

off average forward FER. The regions that benefit most are those with high load and highmultipilot. These regions will experience less degradation during loaded and will have more

capacity before they experience degradation in the RF loss rates. Currently, release 7 and 8/8.1,

the FER targets only automatically apply to rate set 1 systems (8k). This is to aid the

parameterization of systems with mixed rate sets. The reverse link is not effected by the FER

targets in any release so far.

Systems with either rate set can take advantage of the concept of FER targeting by changing these

parameters. This can be especially useful for rate set2 systems that have an inherent lower

capacity due to the increase in Eb/No required for the higher data rate.

FER Target Delta Time Down Delay Step Up Step Down

FERA 35 75 20 1 .6% .7%

FERB 20 40 20 1 .9% 1.0%

FERC 10 20 20 1 1.5% 1.6%

FERD 7 20 15 1 2.5% 2.5%

* Assumes that the TCH gain settings are per defaults as noted in the parameter guide located at

http://scwww.cig.mot.com/~dillon

Fixed Parameters

MinGain1Way This is the lowest forward traffic channel digital gain level to which the

MCC will trickle down when a mobile is not in a soft or softer handoff.

NomGain1Way This is the starting forward traffic channel digital gain level for a mobile

which is not in a soft or softer handoff, except on an origination or

termination (see MaxGain3Way).

MaxGain1Way This is the maximum forward traffic channel digital gain level for a mobile

which is not in a soft or softer handoff, except on an origination or

termination (see MaxGain3Way).


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MCC will trickle down when a mobile is in a 2 way soft or softer

handoff.

NomGain2Way This is the starting forward traffic channel digital gain level for a mobilewhich has entered a 2 way soft or softer handoff.


which is in a 2 way soft or softer handoff.


MCC will trickle down when a mobile is in a 3 way soft or softer

handoff.

NomGain3Way This is the starting forward traffic channel digital gain level for a mobile

which has entered a 3 way soft or softer handoff.


which is in a 3 way soft or softer handoff. It may also be both the initial and

maximum setting at call origination or termination (refer to PchGain).

PchGain Specifies the gain setting for a sectors paging channel. It may also be both

the initial and maximum setting at call origination or termination The MCC

will use the larger of MaxGain3Way and PchGain in this situation.

StepUp Specifies the amount of the increase in forward channel digital gain by the

MCC when a gain increase is requested by the XC.

StepDown Specifies the amount of the periodic decrease in forward channel digital

gain by the MCC.

DeltaTime This is the amount of time (specified as a number of air interface frames) an

MCC channel element waits between gain step downs.

StepDownDelay This is the amount of time (specified as a number of air interface frames) an

MCC channel element waits after a gain step up before step downs resume.


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OrigDelay This is the amount of time (specified as a number of air interface frames)

the channel element waits after an origination or termination before step

downs begin. This delay is to provide ample time for the mobile station to

request a two or three way soft handoff after a call setup.

MinPcbGain This parameter specifies the minimum gain setting for the reverse channel

closed loop power control bits transmitted on the forward channel.

PcbGainFact This parameter specifies the factor the infrastructure equipment multiplies

the current forward channel gain setting to determine what the power

control bit gain should be set to. Its range is 1 < PcbGainFact < 5 and it

can be set in increments of 0.25. Note that the PCB gain is a function of

the mobiles soft handoff state and uses the PcbGainFact value in its

calculation.

FwdPwrThresh This is the threshold against which the ERRORS_DETECTED field of the

RF: Power Measurement Report Message will be compared to determine

if a power step up is required for that mobile station. This parameter is

closely related to PwrRepThresh and must be set with this in mind.

PMRM Message Parameters

PwrThreshEna Enables threshold reporting mode (as specified in IS-95A / J-STD-008) in

the mobile station. Sent to the mobile station in the RF: System Parameters

Message as PWR_THRESH_ENABLE. Currently set at 1 to enable

threshold reporting.

PwrPeriodEna Enables periodic reporting mode (as specified in IS-95A / J-STD-008) in

the mobile station. Sent to the mobile station in the RF: System ParametersMessage as PWR_PERIOD_ENABLE. Currently set at 0 to disable

periodic reporting.

PwrRepThresh If threshold mode reporting (as specified in IS-95A / J-STD-008) is

enabled, this is the number of frame errors which will cause the mobile

station to send an RF: Power Measurement Report Message. This


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parameter can be set to values from 0 to 31 frames. This parameter is sent

to the mobile station in the RF: System Parameters Message as

PWR_REP_THRESH.

PwrRepFrames This specifies to the mobile station the number of frames over which it willcount frame errors. This parameter can be set to certain values between 5

and 905 frames (refer to IS-95A / J-STD-008). This parameter is sent to

the mobile station in the RF: System Parameters Message as

PWR_REP_FRAMES.

PwrRepDelay This parameter specifies to the mobile station how many frames to delay

after sending an RF: Power Measurement Report Message before it

resumes counting frames and frame errors. It can be set to values between

0 and 124 in intervals of 4 frames. This parameter is sent to the mobile

station in the RF: System Parameters Message as PWR_REP_DELAY.


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Chapter 3 Reverse Link Power Control

3.1 CDMA Reverse Channel Power Control Execution

Purpose

The purpose of this note is to give standard background information on reverse power control and

to give additional information as an aid for setting certain power control parameters which effect

system performance. The ultimate goal as stated in a previous note on forward power control is

to minimize the number of required customer changeable power control parameters without

sacrificing system performance.

Introduction

To simultaneously achieve high capacity and quality, IS-95A / J-STD-008 CDMA utilizes channel

power control. Reverse link (mobile to cell) power control varies the power transmitted by the

mobile to ensure that the power from each mobile arrives at the cell site at the minimum possible

level. If the mobiles transmit power is too low, voice quality will be degraded. If the mobiles

power is too high, the mobile may have high quality, but the resulting excess interference will

degrade capacity. Reverse Power Control consists of open and closed loop components. A

discussion on each is in the following sections.

Open Loop Reverse Power Control

The reverse power control open loop, which is performed at the mobile, attempts to account for

common or symmetrical losses on the reverse and forward links mainly due to pathloss and

shadowing (lognormal or slow fading). It is by necessity then, a relatively slow (with respect to

the closed loop) lowpass filtered process. Figure 1.below shows the reverse power control open

loop and the mobile portion of the inner closed loop.

Reverse Power Control Open Loop & Mobile Portion of Inner Closed Loop.


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AGC

DE-INTERLEAVE DEMOD

K- NoW

STRIP

PCB

1 dB

-1 dB

PCB

+Z

-1

INTEGRATOR

OPEN LOOPPC ESTIMATOR

ANTENNA

+

p = NoWr

m

NoW = NthW+IoW+IocW

t_ol

mp

t_cl

mp

t

mp

MOBILE STATION

K - turn around factor = -73 dBm2

CLOSED (Inner) LOOP

OPEN LOOP

INIT PWR (dB)

+NOM_PWR(dB)

sum accessprobecorrections(dB)

Figure 1.

The amount of mobile transmit power (Ptm

) necessary to close the reverse link is estimated by

subtracting total noise plus interference measured at the mobile antenna (Pr

m =NoW) from a

turn around factor (k = -73 dB). The open loop mobile transmit power estimate will be refined

by reverse closed loop power control.

Pt

mk P

r

m=

NoW NthW IoW IocW+ +=

where

NthW - receiver thermal noise and other non-CDMA system noise

IoW - serving cell power

IocW - other CDMA cell interference power

3.1.1 Closed Loop Reverse Power Control

The closedpower control loop consists of an inner and outer loop. The outer loopis maintained

at the base station and provides a means, based on received frame quality information (every 20

ms), to maintain consistent call quality. Theinner loopis distributed between the mobile and the

base station and provides a means, via a 800 Hz power control channel (sending power control

bits (PCB) by puncturing symbols on the forward channel), of varying the mobile transmit power

to achieve a necessary signal to noise level at the base station receiver.


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The closed loop accounts for non-symmetrical (uncorrelated) losses between the reverse and

forward links due to Raleigh/Rician (fast) fading, interference level variation (e.g. voice activity or

loading), differences in transmit and receive antenna gains, and other associated losses

(combiners, connectors, duplexors, etc.). It is the fast power control loop being updated every

1.25 ms (once every power control group (PCG)) that solves the near-far problem and effectively

mitigates small to medium received power variations due to Raleigh fading at slow speeds. Thiseffectiveness is mitigated for sub-rate mobile transmissions.

The portion of the closed loop reverse link power control algorithm performed at the base station

is shown in Figure 2below.


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Reverse Power Control Outer Loop & BTS portion of Inner Closed Loop

AGC

ANTENNA

AGC

ANTENNA

FHT

FQIDEMOD.

DECODER FrameQuality Info

A

1

2

FHT

FHT

DESPREAD FHT

A Eb/No threshold

+ -

+

SET PCB

PCB

M = EstimatedEb/No

m(n)

ADJUST OUTER LOOP

THRESHOLDFrameQuality Info

C

O

M

B

I

NE

R

DESPREAD

DESPREAD

DESPREAD

fingerinfo.

ACCUMULATEOVER 6 WALSHSYMBOLS

WinningWalsh SymbolInfo

Outer Loop Threshold Computer

IF(-)PCB=1 (-1dB)

ELSEPCB=0 (+1dB)

(DEMOD STATE)

OtherInfo

FIGURE 2.

3.1.2 Reverse Power Control Algorithm

3.1.2.1 I nner L oop

Referring to Reverse Power Control Outer Loop & BTS portion of Inner Closed Loop above the

inner loop of the reverse power control algorithm is now summarized.

1) For each walsh symbol interval (n) compute the winning Walsh symbol energy, Ewin.

2) Compute Power Control Metric m(n) =Ewin

k where k is a scale factor.

3) Compute Power Control Group metric measured of all 6 winning walsh symbols in the PCG.

M m n( )n 0=

5

=

4) Compare M to the Outer Loop threshold to increase or decrease mobile TX power via

puncturing power control bit (PCB) on forward traffic channel link.


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Power is changed at the mobile by transmission of the Power Control Bit (PCB) by puncturing on

the forward traffic channel link at the BTS. The mobile power level is increased (PCB set to 0) if

the Power Control Group metric (M) is less than or equal to the current outerloop Threshold.

The mobile power level is decreased (PCB set to 1) if M is greater than the current outerloop

threshold. How much and when to increase or decrease mobile power determines algorithmperformance and has a direct impact on system capacity. The Power Control Group metric (M) is

related to Eb/No as given by the relation in Figure 3.

Delay in sending and applying the PCB degrades reverse power control performance. The error

rate of the PCB also has a performance impact. The increase in reverse link Eb/No required for

1% full rate FER operation due to degrading the PCB error rate from 1% to 5% is less than 0.3

dB. The elevated gain requirement of the PCB (with respect to the TCH gain) needed for a

nominal PCB error rate can be traded off against the excess interference it creates on the forward

link. Note that a requirement in IS-98 requires that during soft handoff a mobile must ignore a

links PCB if the fingers Ec/Io falls below some threshold. This threshold level is left up to the

mobile manufacturer. This requirement along with diversity combining PCBs during softerhandoff can help reduce the required PCB gain.

3.1.2.2 Outer Loop

The outerloop threshold is controlled as a function of frame quality. The goal is to maintain a

consistent call quality level. One possible implementation is to degrade the threshold until

erasures occur and then increase it up by some step size depending on whether the erasure was

considered a full rate or sub-rate frame.

3.1.2.3 I ni tiali zation & RPC Parameter Discussion

After a mobile has originated using the access channel the maximum, nominal, and minimum outer

loop thresholds are set to maxpwr, NomPwr, and minpwr. For example,

RPCMaxEbNo = 9.0 dB (per Antenna) (3435)

RPCNomEbNo = 8.0 dB (2810)

RPCMinEbNo = 5.0 dB (1646)

pwrctl_threshold = RPCNomEbNo

The maximum threshold variable (RPCMaxEbNo) restricts any particular mobile from requiring

too much Eb/No (power) to achieve its desired call quality. The minimum threshold

(RPCMinEbNo) serves to keep fingers in lock at slow speeds and avoids consecutive full rate

frame erasures. A nominal threshold variable (RPCNomEbNo) is used for initializing the power

control threshold at call origination/termination. The step sizes updating the outerloop threshold

are given as:


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RPCUpPFull = 750 (1.3 dB - based on Eb/No reference of 8.0 dB)

RPCUpPNFull = 500 (0.9 dB)

RPCDownP = 8 (0.014 dB)

Note that the step sizes can be specified in terms of Eb/No (dB) values or energy values as given

above2

. The mapping is based on the Winning Walsh symbol energy (M) vs. Eb/No relationship(see Figure 3). A nominal Eb/No value is chosen as a reference when using this relationship

(which is realized as a set of tables) to set the above parameters from the database.

2 4 6 8 10 12

0

2000

4000

6000

8000

10000

Eb/No (dB)

Power Control Threshold Table

M

2 fingers

Figure 3. Relationship between winning walsh symbol metric (M) and Eb/No given twopaths (BSM chip set).

The desired call quality in terms of full rate FER is approximated by the relation

FR FER = 100 RPCDown

RPCUpPFull

and hence is sensitive to the step sizes chosen, especially the step down size.

For example, if the full rate step up size (RPCUpPFull) is equal to 750 energy units and stepdown size (RPCDownP) is 8 units then it would take RPCUpPFull/RPCDownP (= 750/8 in

Walsh Symbol Units or 1.3/0.014 in dB Eb/No) frames for the outerloop threshold to relax to its

previous level at which the frame erasure occurred. Assuming another erasure occurs when the

2.

. The Eb/No values can be converted to finger energy values by indexing the Winning Walsh Symbol Energy (M) versus Eb/No table value using a

nominal value in the normal operating range (in this case we use the nominal threshold of 8.0 dB). Computing the difference energy between 8.014and 8.000 dB Eb/No for two antennas results in the step down energy value of 8 (=57*0.014/0.10) decimal. Using a 7 dB reference maps 750 to 1.8dB and 1% of 1.8 = 0.018 dB. The difference between 7.018 and 7.000 maps to a step down energy value of 8 (=44*0.018/0.10).


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original level is achieved, the mean number of frames between erasures will be 94, giving a full

rate frame erasure rate of about 100/94 =1.1%. Useable delay spread improves this relationship.

The larger the full rate step up size the more excess interference is created. If the step up size is

set too small then the larger the chance of consecutive full rate frame erasures. Simulations, Lab

tests and field results indicate that the size should be in the range (500,750) or approximately 1.0to 2.0 dB.

3.2 Parameter Impacts on System Performance

The explanation of the power control execution is shown below (from a joint technical meeting

note). There are very few suggested field changeable reverse power control settings. The default

gain settings have been set so that capacity is maximized while individual full rate frame erasure

rates are still at an average of 1%. Operators might be willing to trade capacity in the early stages

in order to have lower frame erasure rates.

Reverse bursts should only occur if the maximum set point requirements are exceeded or due to a

stop sign effect during a ramp up from the minimum target set point. Usually the first choice is to

raise the maximum Eb/No set point. Raising the set of Max-Nom-Min should eliminate all bursts.

Reverse average FER can be reduced by decreasing the step down rate (RPCDownP). However,

these changes are not recommended.

In general, with voice traffic the reverse power control settings have been lab/field verified to

provide better than 1% full rate when power control bits are being received at the mobile (good

forward link conditions). Reverse composite FER will typically range from 2 to 4% while still

achieving 1% full rate FER and acceptable voice quality.

3.2.1 Parameter Descriptions

Closed Loop Power Control Parameters

RPCMaxEbNo Reverse Power Control Maximum Eb/No. Reverse power control

algorithm parameter which specifies maximum Eb/No the power control

threshold is allowed to rise to. This data is used to derive the actual

threshold used by the algorithm. Range 2.0 - 14.9 dB, in 0.1 increments.

Optional parameter; if skipped, uses current value. Current recommendedvalue 12.0. All mobile station reverse power control parameters are set

using the EDIT SECTOR MSRRPC command.

Open Loop Power Control Parameters

NomPwr Access Channel Nominal Transmit Power Offset. The correction factor the

mobiles are to use in the open loop power estimate. Sent to the mobile in


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the Access Parameters Message, Please refer to IS-95A / J-STD-008 for

the complete definition. Range -8 to 7 dB. Optional parameter; if skipped,

uses current value. Initial standard value 0.

InitPwr Initial Power for Access. The correction factor to be used by mobile

stations in the open loop power estimate for the initial transmission on anaccess channel. Sent to the mobile in the Access Parameters Message,

Please refer to IS-95A / J-STD-008 for the complete definition. Range -16

to 15 dB. Optional parameter; if skipped, uses current value. Initial

standard value 0. Current recommended value -4.

Closed Loop Power Control Parameters

All closed loop power control parameters are edited using edit SECTOR BTSRPC.

RPCNomEbNo Reverse Power Control Nominal Eb/No. Reverse power control algorithm

parameter which specifies the Eb/No starting point of the power control

threshold used in the algorithm. Range 2.0 - 14.9 dB, in 0.1 increments.

Optional parameter; if skipped, uses current value. Current recommended

value 11.0.

RPCMinEbNo Reverse Power Control Minimum Eb/No. Reverse power control

algorithm parameter which specifies the minimum Eb/No the power control

threshold is allowed to fall to. This data is used to derive the actual

threshold used by the algorithm. Range 2.0 - 14.9 dB, in 0.1 increments.

Optional parameter; if skipped, uses current value. Current recommended

value 8.0.

RPCEraLim Reverse Power Control Frame Erasure Count Limit. Reverse power

control algorithm parameter specifying the number of consecutive sub-rate

frame erasures allowed before an adjustment to the power control

threshold is made. Range 0-255 frames. Optional parameter: if skipped,

uses current value. Current recommended value 2.

RPCUpPFull Reverse Power Control Power Increment Step Full Rate. Reverse power

control parameter algorithm parameter which specifies the amount the

power will have to be increased due to a frame error which was likely to

have been a full rate frame. This data is used to derive the threshold step

used in the algorithm. Range 0.00 to 5.00 dB, in 0.01 increments. Optional


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parameter: if skipped, uses standard value. Current recommended value

1.30.

RPCUpPNFull Reverse Power Control Power Increment Step Not Full Rate. Reverse

power control parameter algorithm parameter which specifies the amountthe power will have to be increased due to a run of frame errors which

were not likely to have been full rate frames. This data is used to derive

the amount the power control threshold will be increased due to a run of

errors which were not likely to have been full rate frames. Range 0.00 to

5.00 dB, in 0.01 increments. Optional parameter: if skipped, uses current

value. Current recommended value .90.

RPCDownP Reverse Power Control Down Step Size. Reverse power control algorithm

parameter which specifies the amount the power will be decreased due to a

good frame. This data is used to derive the threshold step used in thealgorithm. Range 0.00 to 5.00 dB, in 0.01 increments. Optional parameter:

if skipped, uses current value. Current recommended value 0.014.


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Chapter 4 Cell Size Parameters

4.1 Parameter Impacts on System performance

As a general philosophy, access and traffic channel window sizes should be kept to their minimumin order to allow maximum searcher performance (multiple scans) for both the BTS-MCCCE

(channel element) and mobile station. In addition, smaller access windows allow for reduced

preamble size that can increase the paging throughput and paging response time by reducing the

slot size. Rere to the call flow chapter to see where these parameters effect the calls setup and

possible drop rates. After release 5 the PamSz and AchPamWinSz is derived from the cell radius

parameter. However, the TchAcWinSz still needs to manually be set so that the softhandoffs

from large surrounding cells will function properly.

See Doug Bohrers documentation on the searcher algorithm at

(http://scwww.cig.mot.com/~bohrer/)

There are a few parameter that are effected for systems with cells radii greater than 7-9

kilometers (75 chips). See the following chart for specific settings. The groups are:

Cell Radius - For big cells the default of 8.1 km must be increased to compensate for theincreased cell range.

Traffic Window - For big cells the default of 125 for TchAcqWinSz must be increased tocompensate for the increased cell range. This window should always be as large or larger than

the AchPamWinSz in order to be able to aquire the traffic channel. Use the table below to

convert cell radius to chips.

Mobile Search Windows- For big cells the defaults of SrchWinN, SrchWinR must beincreased so that mobile can acquire cells with large differential time-distance separations. PNInc- For big cells larger PN increments must be used in order avoid confusing PSMMs.

This is set in conjunction with the mobile neighbor/remaining search windows.

Cell Radius vs. PamSz and Preamble window size

Cell radius window size PamSz

0.0 to 0.9 12 0

1.0 to 2.9 25 0

3.0 to 3.9 37 0

4.0 to 5.9 50 0

6.0 to 6.9 62 1

7.0 to 8.9 75 1

9.0 to 9.9 87 1

10.0 to 11.9 100 1


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12.0 to 12.9 112 2

13.0 to 14.9 125 2

15.0 to 15.9 137 2

16.0 to 17.9 150 2

18.0 to 18.9 162 2

19.0 to 20.9 175 3

21.0 to 21.9 187 3

22.0 to 23.9 200 3

24.0 to 24.9 212 3

25.0 to 26.9 225 3

27.0 to 27.9 237 4

28.0 to 29.9 250 4

30.0 to 30.9 262 4

31.0 to 32.9 275 4

33.0 to 33.9 287 434.0 to 35.9 300 5

36.0 to 36.9 312 5

37.0 to 38.9 325 5

39.0 to 39.9 337 5

40.0 to 41.9 350 5

42.0 to 42.9 362 6

43.0 to 44.9 375 6

45.0 to 45.9 387 6

46.0 to 47.9 400 6

48.0 to 48.9 412 7

49.0 to 50.9 425 7

51.0 to 52.9 437 7

53.0 to 53.9 450 7

54.0 to 55.9 462 7

56 475 8

4.2 Parameter Descriptions

To see how these parameters effect the call success rate during access, setup or stable calls see

the call flow chapter.

Access and Traffic Windows (see chart for values).

CellRadius This parameter (as of release six) defines the radius of the cell and

automatically sets the PamSz and AchPamWinSz described below. The


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Chapter 5 Handover Parameters

5.1 Handover Types

IS-95 allows for several types of handoff to take place. The following list elaborates and

summarizes each possible type of supported handoff. Some of the handoff types reflect the

implementation of CDMA rather than IS-95. Note that there are always two types of soft and

softer handoff. One type called an add is used to instruct the mobile to include a new pilot in its

active set. The other type called a drop is used to instruct the mobile to exclude an old pilot

from its active set.

Inter BTS, intra transcoder (XC) Soft Handoff: This handoff type is expected to be thehighest percentage of handoffs in CDMA systems as this type contributes to the greatest

amount of reverse channel interference reduction and capacity increase. A mobile station has

simultaneous connections to two or three cells and receives power control orders (for reverse

link closed loop power control) from each cell in the soft handoff.

Intra BTS, Inter Sector, and Intra XC Softer Handoff: This handoff type denotes a statewhere a mobile station maintains connections to multiple sectors all based at the same cellsite

location.

Inter CBSC soft handoff where the new additional link is an XC Sector neighbor from anadjacent CBSC. Calls progresing into the new CBSC, dropping all legs from the original

CBSC, will be hard handed off into best pilot on the new CBSC.

Inter or Intra BTS Hard Handoff: This handoff type denotes either a change in operatingfrequency, a change in 1.25 ms frame offset, or a handoff in which the intersection of old

active set pilots with new active set pilots is the null set.

Hard Handoff to N/AMPS: This handoff type is used to transition a dual/tri mode mobilestation from CDMA operation to operation on an analog system.

A complex handoff in a CDMA system is defined as a handoff instruction to the mobile station

which makes more than one change to the mobiles active set. For example, MAHO

measurements from the mobile station may indicate that it is desirable to enter into a state where

new connections are supported from both the current cellsite location (softer handoff) and fromanother cellsite location (soft handoff).

This type of handoff is not supported by the current system. The BSS will only send RF:

Extended Handoff Direction Messages that add or drop a single pilot from a mobile stations

active set. Some documentation on handoff issues from good starting site by Sam Fernandez

http://www.pamd.cig.mot.com/~sfdez/handoffs.htm


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DAHO Application Note

http://scwww.cig.mot.com/people/cdma/PjM/product/white_papers/main.html

DAHO Product Launch Information

http://www.acpg.cig.mot.com/w3/apd/PIOI/new/launch.html

SC-2.5.1 Pilot Beacon Application Note

[Note that this applies to Release 2.5.] http://scwww.cig.mot.com/people/cdma/PjM/product/white_papers/main.html

Inter-CBSC SHO (Trunking) Home Page

http://www.sc.cig.mot.com/~pedzi/inter_cbsc/ic_deployment.html

Multi-Carrier Application Note (Preliminary)

http://www.pamd.cig.mot.com/nds/NDShomepage.html, under App Notes

CDMA Call Processing SFS

http://scwww.cig.mot.com/~sherwink/DOC/SFS.pdf.html, under

SCELL-CDMA-CP-SFS-001, v 6.0

CDMA Handoff & Power Control SFS

http://scwww.cig.mot.com/~sherwink/DOC/SFS.pdf.html, under

SCELL-CDMA-HOPC-SFS-003, v 6.0

5.1.1 Handover Modes

The system is required to support various handoff modes. The handoff mode defines how the

handoff detection algorithm and execution procedures operate. The mode defines what triggers

the system to add a pilot to the mobile stations active set. Two modes are defined - TAdd and

TComp. When operating in the TAdd mode, any time a pilot rises above the TAdd threshold or

the TComp threshold (i.e. a pilot has risen TComp + 0.5dB above any active set pilot), the system

will attempt to add that pilot to the mobile stations active set via a soft or softer handoff. When

operating in the TComp mode, a pilot must rise above the TComp threshold before the system

attempts to add it to the mobile station active set.

5.1.2 Inter-CBSC Soft Handoff

Introduced in release seven is inter-CBSC SHO. This refers to a method of performing soft

handoffs between cells under different CBSCs. It eliminates the need for pilot beacons at CBSC

borders and allows much more reliable handoffs to occur between CBSCs on the same frequency

than the past hard handoff method.

Adjacent CBSCs must be connected to each other with spans which carry signalling and traffic for

handoff legs on the other CBSC. The ability to add soft handoff legs is done with XCSECTs in

the source CBSCs sectop list. When a sector from an adjacent CBSC is added to the active set,

the traffic and signalling information is backhauled to the source CBSC via the spans which

interconnect CBSCs. At some point while the mobile is moving from one CBSC to another,

control of the call will need to be moved to the target CBSC. This is done by moving the

vocoding function of the call from one CBSC to the other, called an anchor handoff. At the point


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where the anchor handoff is determined to be attempted, a hard handoff will occur, transitioning

the mobile from its current N-way handoff state down to 1-way where the active sector is the

strongest of the current actives.

When a call is in inter-CBSC sho, and information has to be backhauled through another CBSC,

an extra delay is incurred in completing soft handoff adds and drops, approximately 100ms. Thisis one reason why it is beneficial to eventually move the anchor to the other CBSC once the

mobile is sufficiently inside its coverage. In addition, inter-CBSC shos will cause a slight

reduction in MM capacity with respect to intra-CBSC shos, so the quicker the anchor is moved,

the less of an impact there will be on MM utilization.

Anchor Handoff Methods

There are four methods for completing the anchor handoff, configurable on a per cbsc basis

(Legs_Remote, No_Legs_Wait, No_Legs, and Keep_Soft). Below is a description of the

methods along with some reasoning behind the usage of each.

Keep_Soft inhibits all anchor handoffs. It never allows control of the call to be transfered to the

target CBSC and would eventually cause the call to be dropped if the mobile moves through the

target CBSC and into the coverage of a third. It eliminates the risk of moving the call from N-

way to 1-way.

The Legs_Remote method performs the anchor handoff when there are no XCSECTORs or

anchor sectors in the active set from the perspective of the source CBSC. In other words, when

all the active set pilots are on the target CBSC and are not XCSECTORs of the source CBSC,

this criterion is met. Next to Keep_Soft, this is the slowest of the methods at moving the anchor.

This is also the most conservative method with respect to avoiding ping-pong of the anchor back

to the original CBSC because the mobile will be deep inside the coverage of the target.

No_Legs refers to a method where the anchor handoff is completed when no anchor sectors from

the source CBSC are in the active set. The active set needs to include only sectors that are not

local to the source CBSC. This is the quickest of all the anchor handoff methods and has the

potential of causing ping-pong of the anchor between CBSCs in rapidly changing pilot

environments. It could be advantageous, however, in a scenario where multiple CBSC boundaries

are geographically close together requiring a quicker anchor handoff to facilitate inter-CBSC sho

with another CBSC.

The No_Legs_Wait method will cause an anchor handoff once the No_Legs criteria is met and

one of the following occurs: the call goes into one-way sho, the best active pilot is tcomp above

the second best active pilot, or the Legs_Remote criteria is met. This is the only method that

includes any type of dominance criteria for deciding when to move the anchor.

Each method varies on the timing in which it will attempt the anchor handoff. Attempting the

handoff too early may cause ping-pong between CBSCs especially in environments of rapidly

changing pilots. At the same time, waiting excessively long to move the anchor will cause


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additional delay in soft handoffs while the information is backhauled through the the target CBSC.

No_Legs_Wait will generally provide the best compromise between these two issues.

5.1.3 Fast Pilot Shuffle

This feature will reduce the number of dropped calls in the CDMA system under the followingconditions:

The call is in three-way soft handoff None of the current pilots is a candidate to be dropped A better candidate pilot is available.

In the current implementation, a new pilot will not be added to the handoff until one of the active

pilots falls below the TDrop threshold for the corresponding TTDrop time interval. By the time

this happens, a candidate pilot may have created such a strong interference that a RF loss results

and the call is consequently dropped. In order to reduce the number of dropped calls in this

situation, a mechanism is needed to drop one of the active pilots and replace it with the strong

candidate pilot. This can be accomplished by recognizing when the scenario described above is

taking place, and taking action to drop the weakest active pilot so that the strong (or strongest, if

more than one) candidate pilot is added to the handoff. Specifically, the following needs to be

implemented: If a call is in three-way handoff and the CDMA System receives a Pilot Strength

Measure Message (PSMM) from the mobile containing only add events (TAdd and/or TComp

events), the CDMA System shall reevaluate the active pilot set as follows: If the strongest

candidate pilot is a TComp event, the CDMA System shall initiate a drop of the weakest active

pilot. If the strongest candidate pilot is a TAdd event, the CDMA System shall compare the Ec/Io

of the candidate to the Ec/Io of the current active pilots. If the candidate Ec/Io is greater than the

Ec/Io of two or more of the active pilots, the CDMA System shall initiate a drop of the weakest

active pilot. Upon completion of the drop, a PSMM shall be solicited. As a result of PSMM

request, the candidate pilot set will be reevaluated and the strongest pilot will be added to the

handoff if appropriate (already implemented, but mentioned here for completeness).

T_COMP, which previously had seen little utility in soft handoff operations, will be a primary

concern. Any candidate set pilot that is T_COMP dB better than an active set pilot (when in 3-

way SHO) will be used to trigger a pilot shuffle. This should generally be set as high as possible

in order to inhibit Tcomp shuffle events over the worst pilot. The better alternitive is to force the

shuffle to be a better than 2 active pilots than Tcomp over the worst since a small fade will cause

excessive shuffling.

5.1.4 Practical Considerations

SifPilotPwr

Increase from system design settings to maintain coverage, become a dominant server, or change

SHO corners for good metric route numbers. Decrease to allow another pilot to dominate or

because of shared or limited LPA concerns in an otherwise good area. This setting can range

from a standard value of 33-34 to 39 dBm at the top of the frame.


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TAdd/TDrop/TTDrop(TTT)

Handoff Mode - The handoff mode will determine the system optimization that follows, i.e. asystem that has been optimized while set to TComp mode will not behave the same as a

system in TAdd mode. New or different trouble corners appear and SHO locations shift.

During the initial design phase, the amount of effective channel elements per call helps totarget the desired mode. TComp will allow the reduction of channel elements, but in the field

has compared poorly for increased RF loss rates and frame erasure rates. TAdd mode has

been able to provide higher call metrics at the expense of increased channel element use

provided by the extra diversity.

Considerations - There are two effects that should be taken into consideration when settingTTT. The first is the messaging rate. Messaging should be minimized in order to save

XC/CPP utilization and to minimize extra signaling for both voice quality and chances of layer

2 failures (missing ACK Required messaging). For instance, TComp mode will have reduced

PSMM rates (60-80%). The second item to balance is the channel/subscriber ratio, which can

range from 1.3 - 2. TComp mode will have a reduced number of channels per subscriber aswell. One of the main considerations in providing CPP(s) requirements is the call model

which in part depends on the handoff mode.

Typical Ranges - Tadd ranges from -10 to -14 dB in our current systems. Tdrop ranges froma range of -11 to - 16 dB. One important aspect of these two parameters is the difference

between the two settings. There will be more messaging/SHO transitions for a delta (TAdd-

TDrop) of 1 as opposed to 2 dB. TTDrop ranges from 1 (1 second) to 4 (6 seconds). This

should be set as long as possible to slow down messaging and Ping-Pong effects. From field

experience, TTDrop of 3 seems to require less cell site level optimization, but results in about

increase of 33% PSMMs and about 20% SHOs over a TTDrop setting of 4.

Real Life Target Setting - For lowered TAdd/TDrops more channel elements will be used andinitially the system will have lower FER due to diversity. Two examples, illuminate the issues

involved in this problem. The first network is at Tadd of -14 and Tdrop of -16, these values

were chosen after drive testing many tight corners - small cells, where the pilots would shift

strength rapidly requiring earlier PSMM(s). These settings caused some problems due to the

low thresholds, which forced the optimization issue of getting out of 3-way situations. The

best way to accomplish this is the reduction of TTDrop to bounce out of 3-way handoffs. The

channel element usage is higher than was originally designed due to this optimization. In a

second network, where these intense RF problems did not exist. TAdd is-12 and TDrop is -

13 by using these parameters the system has been much easier to optimize and the channelutilization is lower, at about around 1.4 channel/subscriber. TTDrop for both systems is at 3

or 4 seconds for most of the cells.

System Deployment - For ease of deployment it is best to start with the same TAdd, TDrop,TTDrop settings on all cells. First of all, it is simpler because after an SHO add occurs

between different cells, with different TTT settings the mobile will have a new set of TTT.

The algorithm used to combine TTT optimizes the parameters in order to allow the fast cell to


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add a pilot to a call as soon as it crosses the TAdd threshold. TComp mode

tells the system to wait for a pilot to rise above the TComp threshold

before it is added to a call. This data exists in the XC database, not in the

MIB.

PilotInc Pilot PN Sequence Offset Index Increment - The mobile station uses this

field to determine how remaining set pilots should be searched. It is set tothe largest increment such that the pilots of the neighboring sectors are

integer multiples of the increment. This data is sent to the mobile station in

the RF: Neighbor List Message and the RF: Neighbor List Update

Message. The XC must use the same value as is contained in the MIB.

This should be set as large as possible to speed up the search time for the

mobiles remaining set neighbors. Also, large PilotInc values allow for

large cells to be used without concern for PN-Offset ambiguity in PSMM

reports. However, the complications of re-using PN-Offsets (PN-Offset

Planning) pulls the PilotInc down to lower values. See Sams presentation

on this issue at http://www.pamd.cig.mot.com/~sfdez/pn.pdf

NeighborList Neighbor List - This list contains all of the neighbor sector PN offsets for

the current call. This parameter is passed to the XC in both the SCAP:

CDMA Update Parameters Message and the SCAP: CDMA XC Channel

Assigned Message. The neighbor list should be input in order. The order

is sorted by source to target handoff likely hood (or hits). The hit list is the

number of times that the neighbors in the target list were handoff

candidates for that source. Having the correct order will allow the mobile

to maintain the best neighbor list which greatly speeds up the search speed

for the best neighbor set. The list can be created with simulation or during

FOA activities. The maximum list for each sector is 20. However, the listsshould be minimized in order to allow the best combined lists to be sent in

the Update Neighbor list message, which is sent after a handoff addition.

Mobile Search Windows*

SrchWinA The active pilot set search window size. This size is made large enough to

incorporate 95% of the expected delay spread energy. From delay spread

surveys this number was found to be 8 us. The window size has been set

to 5 which corresponds to 20 PN chips or 16 us. Since the active set

search window is based on the earliest arriving "usable" delay spread

component (IS-95A 6.6.2.1.4.1 / J-STD-008 2.6.2.1.4.1) for a given pilotthen we account for +- 8 us about that ray and hence would acquire about

95% of all delay spread energy. In some extreme cases for some sectors in

some cities usable rays will exist outside this window. Hence, this window

size also needs to be set on a per sector basis. This will be extremely

difficult to do without knowing the delay spread environment for each

3*

From a Motorola Internal Memo by Bob Love, 9/5/95.


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sector. Just increasing all active pilot search window sizes would reduce

the likelihood of missing pathlogical rays (usable rays >8 us from earliest

arriving "usable" delay spread component) but at the expense of increasing

PN hypothesis search time. Increasing PN hypothesis search time would

increase soft handoff delay. Unless specific information is known for a

given site then I would still recommend using a SrchWinA size of 5 (+-8us). If the site is on a waterfront across from other sites or is near

mountains then the size should probably be increased to 6 (+-11 us) or

more.

SrchWinN The Neighbor pilot set search window size. This size is made large enough

to account for differential time delay between the mobile and a potential

handoff cell given in the mobile's neighbor list. The worst case differential

delay would be the case when the mobile is next to a serving site and tries

to handoff to another distant site. Currently, the neighbor window size is

set to 6 (28 PN chips) which allows for a worst case separation of about 2miles (3300 meters) between cells. If the mobile was "n" miles from its

serving site before going into handoff with a site slightly less than 2 miles

away from the mobile then the current setting would still work. There are

some sites in Hong Kong and Los Angeles that appear to handoff to sites

that are up to 4 miles away. For these sites, the SrchWinN size should be

increased to 8 (see (5) below) to account for the worst case SHO mobile

position possibility.

Window Size in terms of Distance (assume loss of 2 PN chips due to inaccuracies)

6 1.95 miles (3175 meters)7 2.86 miles (4640 meters)

8 4.36 miles (7082 meters)

9 5.86 miles (9524 meters)

SrchWinR Similar to SrchWinN except the sites will typically be further away. Our

current infrastructure does not promote remaining set pilots to the

candidate set.


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Chapter 6 Access and Setup Parameters

The call flow progression can be broken into idle, access, setup and stable traffic operation.

These generic catogories can be used in order to understand how the correct parameterization of

the system will effect the success rate and capacity of calls in a CDMA system. The most time

critical portion of a call is the transition from access to stable traffic since the mobile isunprotected from interference from other pilots in the time before the system is able to add them

to the active set by means of handoff operations after arriving on the traffic channel.

6.1. Idle Parameters

The parameters that effect the performance of the mobile during its time spent on in idle mode are

shown. The success of good idle settings effects the ability of the system to respond to the first

probe. This quiets the mobile which is not under closed loop power control and allows for a

faster call setup, reducing the latency. The worst case occurs when the mobile has exhausted its

probe sequences or lost the paging channel during the origination attempt. The neighbor list is

used in idle mode to help the mobile search the best pn offsets. The correct active search

window allows the mulitpath to be used to enhance the current pilots Ec/Io as opposed to

causing self interference. The correct neighbor list window size allows the mobile to see new

pilots. The chart explains how each parameter plays is associated with successful idle settings

such that the mobile is on the best pilot during the origination.

Parameter Set High Set Low Set Correctly

Neighbor list order important

SrchWinA slows searcher misses multipath balance to get

multipath/speed

SrchWinN slows searcher misses neighbors must see far neighbors

SrchWinR slows searcher misses neighbors should be added to the

neighbor list

6.2 Access Parameters

The access attempt success is dependent on the strength of the probe received at the base station

and the window used by access channel. They key customer changable parameter is the cell

radius. Although the default value of 10 km covers 95% of urban cells adjustment may be

necessary for larger cells. In general , the access channel is set to provide the most rapid response

probe and probe response due to the importance of getting the mobile onto the traffic channel and

into n-way. The chart explains how each parameter plays is associated with successful accesssettings such that the mobiles first probe is received by the access channel.

Parameter et High Set Low Set Correctly

Cell Radius slows searching miss probes always pick larger than expected

cell size

AchPamEbNo miss good probes excessive falsing rate set to target falsing rate

AchPamIPer NA NA must match AchPamEbNo


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AchPamWinSz slows searching miss probes always pick larger than expected

cell size

NumStep adds delay will not get full mobile tx

range

full range of mobile power

quickly

MaxCapSz adds delay multiple probes all dialing sequences should fit

into one probe

PamSz adds delay miss probes hardcoded/derivedPsist0To9 adds delay NA set to minimize delays

Psist10 adds delay NA set to minimize delays






MsgPsist NA NA set to minimize delays

RegPsist NA NA set to minimize delays

ProbePnRan adds delay probe collisions set to minimize delays

ProbeBkoff adds delay probe collisions set to minimize delaysBkoff adds delay probe collisions set to minimize delays

MaxReqSeq adds to delay of setup possible lower send-

connection ratios

set to minimize delays

MaxRspSeq adds to delay of setup possible lower send-

connection ratios

set to minimize delays

AccTmo excessive delay to 2nd probe NA set to response time of BS Ack

NomPwr excessive interference won't see first probe correctly set for highly loaded

sytem

InitPwr excessive interference won't see first probe correctly set for highly loaded

sytem

PwrStep full range of mobile power will not exercise range balance interference/power range

The following call flow shows a successful access attempt. Once the MM is aware of the call

activity, it will be logged for system statistics.


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MSC MM FEP GPROC XCDR KS GLI PG-ACC TCH MS

[1] Origination Message

[2] Base Station Ack Order

[3] Start T42m (12 sec)

[4] CHI: Channel Required

[5] LAPD: Channel Required

[6] LAN: Channel Required

MOBILE ACCESS PARAMETERS

Strength OpenLoop + Nom + Init

Number of Probes NumStep - number per sequence MaxRespSeq,MaxReqSeq

Step up for each subseqent probe PwrStep

Probe Size PamSz - preamble size MaxCapSz - maximum capsule size

Persistance Settings Psist0-15 ProbePnRan, ProbeBkOff BackOff

BTS RX ACCESS PARAMETERS

Access Threshold AchPamEbNo AchPamIPer

Cell Radius

BTS TX ACCESS PARAMETERS

Paging Channel Gain

PM PEG

PMC 10-1PMC 20-5

6.3 Setup Parameters

The setup portion of the call flow begins with after the base station has acknowledged the

mobiles origination sequence. At this point, the system will record the success or failure of the

call in both the call detail logs and performance management system at the operations and

maintainance center (OMCR). The delay incurred in receiving the probe acknowledment and

the probe strength are the two reminents of the access channel that will effect call setup

performance. A fast channel assigment time is key to reducing the latency associated in placingthe mobile on the traffic channel. The parameters associated with call setup are shown below.

Parameter Set High Set Low Set Correctly

XC State 2 reserves mcc resource cause CFC6 set high enough to not get

CFC6

XC State 3 reserves mcc resource cause CFC7 set high enough to not get

CFC7

XC State 4 will not peg correct CFC cause CFC9 set high enough to not get

CFC9

XC State 7 will not peg correct CFC cause CFC13 set high enough to not get

CFC13

Acquistion Count delays XC state change

from invalid to valid

possible false set for minimal delay on

XC state change also used

to transition rf loss counter

MccCpT1 reserves mcc resource will cause no tch preamble set high enough to not get

CFC5

Orig Gain NA NA hardcoded to 127

Orig Delay excessive interference setup failures allow mobile to get into

SHO state


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TchPamEbNo excessive interference high falsing rate set to target in lab

TchPamWinSz slows searching lock to multipath outside of

main ray

set to expected mulitpath

window

TchPamlPer NA NA tied to PamEbNo

The parameters are shown in the call flow. The first portion shows the parameters used up to thepoint of sending out preamble to the mobile before the mobile has received the channel assign.

Note that some of the A+ and MM timers have been removed in order to reduce the complexity

of the call flow. The MM/A+ timers are used in order to remove resources in error legs and are

not usually triggered.

MSC MM FEP GPROC XCDR KSW GLI PG-ACC TCH MS

[22] LAPD: XC Channel Assigned

[23] Start XcCpT1

[24] MCAP: Traffic Channel BTS Link Request

XC PARAMETER

starts XC state 1,2 timer

PM PEGS

PMC 01-1PMC 10-2PMC 20-1PMC 20-2PMC 20-3PMC 20-4

PMC 20-7PMC 20-8PMC 25-7PMC 60-2

PMC 01-3PMC 71-1

[30] MCAP: Traffic Channel State Change

[XCDR channel,New_State=MCC_idle, Invalid_Speech, or Valid_Speech]

[31] Stop XcCpT1

[32] LAPD: Channel Assigned

XC PARAMETER

state 2 complete

if XC state 2 expires CFC=6 results

start state 3 timer

[34] CHI: Channel Assigned

[35] Start MccCpT1

[36] IS-95 frames

[37] CHI: Target Channel Designation

[CDMA Freq, WC, encryption mode=0,frame offset=0,MIN, ESN, Band Class,MSID Type, MS Prot. Rev., Transmit Addr]

BTS SETUP PARAMETERS

Transmit Preamble Orig Gain

Timer MccCpT1 starts, after thispoint if the mobile does not arrive onTCH with premable a CFC will result

[33] LAPD: Channel Assigned

The next step is to send the channel assignment message on the paging channel and hope that he

mobile will be able to see the preamble frames being sent on the traffic channel. If the mobile

receives 2 frames in 200 ms it will transmit preamble back on the reverse link on the traffic

channel. If no mobile response is received in MccCpT1 the call final class CFC5 is pegged.


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MSC MM FEP GPROC XCDR KSW GLI PG-ACC TCH MS

[65] MCAP: Layer 3 Message Request

[XCDR Channel,Magic Number,ackr=1,Service Option Response Order or Service Connect Message,(ack_req,service option)]

[66] Service Option Response Order/Service Connect Message

[67] IS-95 frames

[68] Mobile Station Ack Order

[69] MCAP: Layer 3 Message Confirm

(Indicates that Service Option Response Order/Service Connect Message was acked)

[70] Service Connect Complete Message

(Sent if XCDR sent a Service Connect Message)

XC PARAMETER

if XC state 7 expires CFC=13 resultswhich is no service optionacknowledgement


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Chapter 7 Migration To a New Software Release

When a new software release is loaded onto the infrastructure, there will generally be parameter

changes that go along with that release due to algorithm changes, further testing, etc. Care

should be taken when doing these changes to ensure a smooth transition from one release to thenext. The following section is a general description of the order in which these changes should be

made and what statistics should be monitored for each. Its always recommended to complete at

least a one to two hour metric route drive after each step and analyze mobile logs for messaging

rates, FER, etc. The time frame of completing all of the changes will affect the appropriate soak

period of each step, but at least one day is needed to get a large enough sample size, preferably

three days or more.

Step 1 : Necessary Changes

The first step is taken immediately after the load. It includes all changes necessary to keep system

performance consistent with the previous load. These may include timers, database modifications,or newly created parameters due to new features.

Monitor dropped call rate, access failure rate, soft handoff failure rate, and mm utilization

percentage through performance management statistics. Also, keep a close eye on CFC

percentages as timer changes can cause odd CFCs to occur (6, 80, 255, etc.) if not done properly.

See chapter six of this document for details on what CFCs are affected by the expiration of

particular timers.

Step 2 : Forward Power Control

Modifications of power control on the forward link should be done next. This should be done

second for a couple of reasons. First, the forward link is generally most sensitive to change

compared to the reverse link. There is obvious value to doing these changes early in order to

gauge their effects as soon as possible. Additionally, most CDMA systems are overwhelmingly

forward link limited. Therefore, the benefits of forward link parameter changes will be seen

earlier rather than later.

Categories of forward power control parameters are forward traffic channel gains (tchgain),

mobile station forward power control (msfpc), and base station forward power control (btsfpc).

It is generally recommended that tchgain changes be done first to ensure that the new settings do

not cause the gain to settle too low or have an undesired effect on the frame erasure rate. Msfpcand btsfpc modifications will affect the speed of power control and can be completed after tchgain

changes.

Dropped call rate and soft handoff failure rate should be monitored. Forward FER and PMRM

rate are the most likely things to be affected by these changes and should be analyzed via a drive

test.


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Step 3: PPS Powers

Next in line for possible changes, if recommended, are the ppsgains. These include the gain of the

pilot, paging, and sync channels. Sifpilotpwr is normally changed on a per sector basis and would

not be included in the modifications. These should come after the forward power control changes

because modifications of the power in the overhead channels can create holes if set too low andcause excess interference if set too high.

Dropped call rate and access failure rate should be closely monitored after these changes. If

modifications are made to the paging channel, a drive test should include a before and after

analysis of the paging CRC error rate.

Step 4: Reverse Power Control

RPC changes (btsrpc) can be done later in the migration because small changes in the EbNos will

have little noticeable effect on system performance and are normally less critical due to most

systems forward link limitation. Lower nominal and minimum values will help to reduceinterference in reverse link limited scenarios.

Dropped call rate and access failure rate should be monitored via pm stats. If SMAP is available,

it would be valuable to compare reverse link FER performance.

Step 5: Other Changes

This step may include modifications of mobile initial power (msrpc), access channel (pachgen,

macc), reverse traffic channel (tchgen), timers (cpparms, aparms), or global handoff parameters

(maho). These will usually be minimal in number and may need to be changed in additional steps

depending on the volume and particular changes being made.

What to monitor will depend upon what changes were made. In case it isnt obvious yet, access

failure rate and dropped call rate are good things to keep an eye on. Additional statistics will

vary.


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Chapter 8 Field Optimization Work Catogories

Unloaded CDMA system optimization is fairly straightforward. Here are the main activities that

comprise a thorough optimization process.

Coverage

Description/Purpose - A grid drive to show Ec/Io, mobile Tx power and other physical layerquantities that will provide statistics in support of the margin that the system will have for

growth. It will not be able to predict call success rate.

Staff - 1 van driver, 1 mobile-dm /GPS operator, 1 BSC-SMAP operator. Output - Ec/Io, forward/reverse erasure rates, mobile Tx power, SHO states all associated

with position. Poor coverage locations can be located. System design assumptions about

coverage, capacity, cell ownership can be confirmed.

Performed - Performed initially to spot equipment calibration, antenna problems, poorcoverage locations. Performed after optimization is complete. Performed after system is

commercial during busy hour to locate effects of cell breathing/loading.

Metric Route

Description/Purpose - A metric route is used to predict call success rate. It will also confirmaccess windows/thresholds/performance. The metric route should consist of a drive

containing the highest automobile traffic highways/roads covering the city and be about one

hour in length. If you can not create a single Metric Route that requires less than one hour to

drive, then it is advisable to divide the metric route into smaller routes that meet the time

criteria.

Staff - 1 van driver, 1 mobile-dm /GPS operator, 1 BSC-SMAP operator.

Output - Call statistics including: origination attempt success rates, L-M and M-L successrates, failure causes/locations, audio quality verification. Metric for commercial dateprediction.

Performed - Repeated until results are stable. Re-driven after SifPilotPwr changes or SHOoptimizations to check for unknown effects. And re-driven after tape upgrades.