handoff & power control application note

Handoff & Power Control Application Notes R 16.1

Version 1.0

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CDMA Handoff & Power Control

Motorola Confidential and Proprietary 2

TABLE OF CONTENTS

1 CDMA Handoff Detection and Target Selection_________________________________ 3

1.1 General Discussion____________________________________________________ 3

1.2 CDMA Handoff Types_________________________________________________ 3

1.3 Complex Handoffs ____________________________________________________ 4

1.4 Database Assisted Handoff (DAHO) _____________________________________ 4

1.5 Inter-CBSC Soft Handoff ______________________________________________ 4

1.6 Handoff Modes_______________________________________________________ 5

1.7 Mobile Station Operation ______________________________________________ 5

1.8 Database Parameters__________________________________________________ 7 1.8.1 Complex Soft Handoff Database Parameters_____________________________ 9 1.8.2 Pilot Dominance__________________________________________________ 10

1.9 RF Measurements Used in CDMA Handoff and Power Control Detection _____ 11 1.9.1 Pilot ordering for Neighbor lists _____________________________________ 13

1.10 CDMA Cellsite Receive Antenna Selection _______________________________ 14

2 Reverse Channel Power Control ____________________________________________ 15

2.1 Introduction ________________________________________________________ 15

2.2 Open and Closed Loop _______________________________________________ 15

2.3 Reverse Power Control Algorithm ______________________________________ 17 2.3.1 Inner Loop ______________________________________________________ 17 2.3.2 Outer Loop______________________________________________________ 18

2.4 Database Parameters_________________________________________________ 19

3 Forward Channel Power Control____________________________________________ 20

3.1 Introduction ________________________________________________________ 20

3.2 Algorithm Specifics __________________________________________________ 21 3.2.1 Gain Settings ____________________________________________________ 22

3.3 Power Control Bit Description _________________________________________ 23 3.3.1 PCB Error Rate Effect _____________________________________________ 23

3.4 PMRM Message Description. __________________________________________ 24

3.5 Forward Power Control in Different SHO States. _________________________ 24

3.6 Database Parameters_________________________________________________ 25



1 CDMA Handoff Detection and Target Selection

1.1 General Discussion

For CDMA systems, handoff detection processing will take place in the XC/SDU and in the MM. The XC/SDU will detect the need to handoff, perform handoff preprocessing and identify events. The MM will determine the handoff type, perform target selection and perform channel allocation. Note: From hereon, for IS-95B capable mobiles, the mention of TAdd, TComp and TDrop thresholds shall have the following meanings:

• For Add condition/event/mode:

Above the TAdd threshold, shall mean above the Dynamic Threshold Add explained in section 1.7, ’Mobile Station Operation’. Above the TComp threshold, shall mean above the Dynamic Threshold Add and Tcomp x 0.5 dB.

• For Drop condition/event:

Below the TDrop threshold, shall mean below the max (Dynamic Threshold Drop, TDrop/2). Refer to section 1.7, ’Mobile Station Operation’, for more explanation of Dynamic Threshold Drop.

For non IS-95B capable mobiles, P_Rev < 3 or Soft_Slope = 0, the mention of TAdd, TComp and TDrop thresholds shall mean as they are, i.e., the existing IS- 95A MAHO parameters.

1.2 CDMA Handoff Types

IS-95 [3] 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” and is used to instruct the mobile to include new pilots in its active set. The other type called a “drop” that is used to instruct the mobile to exclude old pilots from its active set. Handoffs may be triggered by either Mobile Assisted Handoff (MAHO) or Database Assisted Handoff (DAHO) techniques. MAHO techniques depend on measurements made by the mobile and reported to the BTS. DAHO techniques depend on information on cell configuration stored in the CBSC/BTS along with the system’s knowledge of which cells/sectors control a particular call.

MAHO techniques may be used to trigger soft, softer and hard handoffs. DAHO techniques may be used to trigger hard handoffs only.

• Inter BTS, intra XC/SDU Soft Handoff: This handoff type is expected to be the highest 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 more cells and receives power control orders (for reverse link closed loop power control) from each cell in the soft handoff. This term will be used fairly often within the body of the document and can be used in a generic way.

• Inter BTS, Inter-CBSC Soft Handoff: This handoff type denotes a state where a mobile station maintains connections to multiple sectors located under control of different CBSCs. In this case the CBSCs, controlling the BTSs, are linked by



either special sub-rate trunk circuit connection or by a packet network connection.

• Intra BTS, Inter Sector, Intra XC/SDU Softer Handoff: This handoff type denotes a state where a mobile station maintains connections to multiple sectors all based at the same cellsite location.

• Inter or Intra BTS Hard Handoff: This handoff type denotes either a change in operating frequency, a change in 1.25ms frame offset, a change from an IS-2000 radio configuration1 to another, or a handoff in which the intersection of old active set pilots with new active set pilots is the null set.

• Hard Handoff to Analog: This handoff type is used to transition a multi-mode mobile station from CDMA operation to operation on an analog system.

1.3 Complex Handoffs 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 mobile’s 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 from another cellsite location (soft handoff).

The current system supports multiple add operations and multiple drop operations for inter-CBSC soft/softer and intra-CBSC soft/softer handoffs. A maximum active set size of 6 pilots is supported. Multiple add and multiple drop operations are limited to a single channel element each for each handoff detection event. Pilot shuffling with multiple add-drops, triggered from a single handoff detection event, is also supported to maintain an optimal active set when the number of soft/ softer legs is at the maximum. The system currently supports pilot shuffle involving channel elements in up to two BTSs in a single handoff direction message to the mobile station.

1.4 Database Assisted Handoff (DAHO) This handoff detection algorithm is used to determine when to transition a mobile station to another frequency band and/or air interface other than CDMA. Since normal CDMA Mobile Assisted Handoff (MAHO) handoff detection methods cannot be used to determine a suitable target, database-stored information concerning partially or fully overlapping handoff targets must be used to carry out the handoff process.

1.5 Inter-CBSC Soft Handoff Soft and softer handoffs can be performed with a cell under another CBSC by using inter-CBSC soft and softer handoff procedures to connect the target CBSC channel element to the source CBSC transcoder via an inter-CBSC subrate channel or an inter- CBSC packet network.

The method of performing inter-CBSC soft/softer handoffs via subrate channels and SCAP links between CBSCs is referred to as the trunking method, to distinguish it from the A1 method, using standardized IS-634 procedures, which may be implemented in the future, or from the method where bearer connection between CBSCs can be established through a common transport network. 1 IS-95 A/B type of radio channel are RC1 - Radio Configuration 1 and RC2 - Radio configuration 2 on both forward and reverse link while IS-2000 1X type of radio channel are RC3, 4, and 5 on the forward link and RC 3 or 4 on the reverse link.



A call can be in inter-CBSC soft/softer handoff with multiple target CBSCs at the same time. A call enters into inter-CBSC soft handoff when the mobile reports a viable candidate pilot that points to an XCSECT (external sector data base), and this XCSECT has inter-CBSC soft handoffs enabled. Note that the XCSECT can be residing in the source CBSC or can be backhauled from target CBSC as part of a previous inter-cbsc handoff procedure. Subsequent inter-CBSC soft and softer handoff operations may occur with pilots that are in the neighbor list of a target CBSC cell. Target CBSC neighbor lists are sent back to the source as part of the inter-CBSC soft/softer procedure. In these ‘remote neighbor lists’, the source checks for matches with candidates reported by the MS.

The source CBSC remains in control of the call until no source handoff legs remain. At this point the source determines if it should transfer control to a target CBSC via a hard handoff. Such a hard handoff is named “Anchor Handoff”. In general, all procedures and requirements specified for intra-CBSC soft and softer handoffs apply to inter-CBSC soft and softer handoffs, unless otherwise noted. However, separate handoff execution procedures have been specified for inter- CBSC soft handoff.

1.6 Handoff 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 station active set. Two modes are defined - “TAdd” and “TComp”. When operating in the TAdd mode, any time a pilot rises above the TAdd or the TComp threshold (i.e. a pilot has risen TComp X 0.5dB above any active set pilot), the system will attempt to add that pilot to the mobile station’s active set via a soft or a 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.

1.7 Mobile Station Operation IS-95B and above calls for the Add and Drop thresholds to be calculated dynamically by the MS using the formula below,

If: P_Rev_In_Use ≥ 4 and Soft_Slope ≠ 0

dBStrengthPilotActiveSlopeSoftInterceptAdd

AddThresholdDynamicn

j��

��

�×+= �

=1

log108

_

2

_

dBStrengthPilotActiveSlopeSoftInterceptDrop

DropThresholdDynamicj

n

iji �

�

�

�

��

�

�×+= �

>log10

8

_

2

_

Where Active Pilot Strength1 < ... < Active Pilot Strengthn and i = 1, 2,..., n-1.

Soft_Slope, Add_Intercept and Drop_Intercept are soft handoff parameters introduced by IS-95B and above for the calculations.

Note: The pilot strengths reported by the mobile station in a PSMM message are in dB (logarithmic scale). They cannot be summed to calculate the aggregate value. An Ec/Io



Conversion Table is used to convert a dB value to a linear integer value which can then be conveniently summed to provide the aggregate value of a set of pilots.

It is assumed that the mobile station operates as follows (from IS-95 [3]):

If P_Rev_In_Use ≥ 3 or Soft_Slope = 0

Any time a neighbor set or remaining set pilot rises above TAdd, the mobile station sends an RF: Pilot Strength Measurement Message (PSMM) or RF: Extended Pilot Strength Measurement Message (EPSMM) to the system. This is referred to as a TAdd indication. The mobile station will add this pilot to the candidate set and no further TAdd indications will be sent for this pilot. Subsequent PSMMs will contain strength measurements for this pilot.

Any time a candidate set pilot rises TComp x 0.5dB above any active set pilot, the mobile station sends a PSMM or RF: Extended Pilot Strength Measurement Message (EPSMM) to the system. This is referred to as a TComp indication. After an RF: Extended Handoff Direction Message or RF: General Handoff Direction Message or RF: Universal Handoff Direction message which does not include the TComp pilot in the new active set, the mobile station will resend the TComp indication for that pilot if the condition persists.

The mobile station removes pilots from the candidate set as follows:

When the pilot falls below the TDrop threshold for TTDrop seconds (the handoff drop timer has expired)

When the candidate set is full and the mobile station must add another pilot to it, the mobile station will remove the pilot for which the handoff drop timer is closest to expiring.

A candidate pilot is added to the active set

Any pilot which crosses TAdd and TComp thresholds simultaneously is treated as a TComp indication by the mobile station. The mobile station only sends one PSMM for that pilot.

Any time an active set pilot falls below the TDrop threshold for TTDrop seconds, the mobile station sends a PSMM or RF: Extended Pilot Strength Measurement Message (EPSMM) to the system. This is referred to as a TDrop indication. After an RF: Extended Handoff Direction Message, an RF: General Handoff Direction message, or an RF: Universal Handoff Direction message which does not remove the TDrop pilot from the new active set, the mobile station will resend the TDrop indication for that pilot if the condition persists.

If: P_Rev_In_Use ≥ 4 and Soft_Slope ≠ 0

Any time a neighbor set or remaining set pilot rises above max (Dynamic Threshold Add, TAdd/2), the mobile station sends an RF: Pilot Strength Measurement Message (PSMM) or RF: Extended Pilot Strength Measurement Message (EPSMM) to the system. This is referred to as a TAdd indication. The mobile station will add this pilot to the candidate set.

Any time a candidate set pilot rises above the Dynamic Threshold Add, the mobile station sends an RF: Pilot Strength Measurement Message (PSMM) or RF: Extended Pilot Strength Measurement Message (EPSMM) to the system. This is referred to as a TAdd indication. After an RF: Extended Handoff Direction Message or RF: General Handoff Direction Message or RF: Universal Handoff Direction message which does not



include the TAdd pilot in the new active set, the mobile station will resend the TAdd indication for that pilot if the condition persists.

Any time a candidate set pilot rises above the Dynamic Threshold Add and TComp 0.5dB above any active set pilot, the mobile station sends a PSMM to the system. This is referred to as a TComp indication. After an RF: Extended Handoff Direction Message or RF: General Handoff Direction Message or an RF: Universal Handoff Direction message which does not include the TComp pilot in the new active set, the mobile station will resend the TComp indication for that pilot if the condition persists.

The mobile station removes pilots from the candidate set as follows:

When the pilot falls below the TDrop threshold for TTDrop seconds (the handoff drop timer has expired)

When the candidate set is full and the mobile station must add another pilot to it, the mobile station will remove the pilot for which the handoff drop timer is closest to expiring. If more than one such pilot exists, the mobile station shall delete one such pilot that has the lowest strength. If no pilot in the candidate set has an enabled handoff drop timer, the mobile station shall delete from the candidate set the pilot that has the lowest strength.

A candidate pilot is added to the active set

Any pilot which crosses Dynamic Threshold Add and TComp thresholds simultaneously is treated as a TComp indication by the mobile station. The mobile station only sends one PSMM for that pilot.

Any time an active set pilot falls below the max(Dynamic Threshold Drop, TDrop/2) for TTDrop seconds, the mobile station sends a PSMM to the system. This is referred to as a TDrop indication. After an RF: Extended Handoff Direction Message or RF: General Handoff Direction Message or RF: Universal Handoff Direction message which does not remove the TDrop pilot from the new active set, the mobile station will resend the TDrop indication for that pilot if the condition persists.

1.8 Database Parameters The following are the database parameters which apply to handoff detection. Refer to the System Command Reference Manual for further information and default values.

TAdd - Pilot Detection Threshold - The threshold above which a pilot must rise in order for the MS to transmit a pilot strength measurement message. The system sends this parameter to the mobile station in the RF: Extended System Parameters Message, RF: Extended Handoff Direction Message, RF: General Handoff Direction Message, RF: Universal Handoff Direction message and the RF: In Traffic System Parameters Message.

TComp - Active Versus Candidate Set Comparison Threshold - The threshold which a candidate set pilot strength must rise above an active set pilot to cause the MS to transmit a pilot strength measurement message. The system sends this parameter to the mobile station in the RF: Extended System Parameters Message, RF: Extended Handoff Direction Message, RF: General Handoff Direction Message, RF: Universal Handoff Direction message and the RF: In Traffic System Parameters Message. This parameter is also used for handover detection event discrimination in the XC/SDU sub-system.

TDrop - Pilot Drop Threshold - The threshold below which a pilot strength must drop in order for the MS to transmit a pilot strength measurement message. The system sends



this parameter to the mobile station in the RF: Extended System Parameters Message, RF: Extended Handoff Direction Message, RF: General Handoff Direction Message, RF: Universal Handoff Direction message and the RF: In Traffic System Parameters Message.

TTDrop - Active or Candidate Set Drop Timer - The amount of time in seconds the MS will allow an active or candidate set pilot strength to remain below the drop threshold before action is taken to remove the pilot from the active or candidate set. The system sends this parameter to the mobile station in the RF: Extended System Parameters Message, RF: Extended Handoff Direction Message, RF: General Handoff Direction Message, RF: Universal Handoff Direction message and the RF: In Traffic System Parameters Message.

Soft_Slope - The slope use by the mobile station to calculate the Add and Drop thresholds for adding a pilot to the active set, or dropping a pilot from the active set. The system sends this parameter to the mobile station in the RF: Extended System Parameters Message, the RF: In Traffic System Parameters Message, RF: Universal Handoff Direction message, and the RF: General Handoff Direction Message.

Add_Intercept - The intercept use by the mobile station to calculate the Add threshold for adding a pilot to the active set. The system sends this parameter to the mobile station in the RF: Extended System Parameters Message, the RF: In Traffic System Parameters Message, RF: Universal Handoff Direction message, and the RF: General Handoff Direction Message.

Drop_Intercept - The intercept use by the mobile station to calculate the Drop threshold for dropping a pilot from the active set. The system sends this parameter to the mobile station in the RF: Extended System Parameters Message, the RF: In Traffic System Parameters Message, RF: Universal Handoff Direction message, and the RF: General Handoff Direction Message.

HandOffMode - Specifies to the XC/SDU which handoff mode to use. Currently two modes are defined. TAdd mode and TComp mode. TAdd mode tells the system to 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/SDU 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 to the 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/ SDU must use the same value as is contained in the MIB. The scope of this parameter is per sector.

NeighborList - Neighbor List - This list contains the entire neighbor sector PN offsets for the current call. This parameter is passed to the XC/SDU in both the SCAP: CDMA Update Parameters Message.

DAHO - DAHO Indicator - This parameter indicates whether a sector-carrier is near a border and contains neighboring or overlapping sectors operating on another frequency and/or non-CDMA signalling scheme.

DAHOHysTimer - DAHO Hysteresis Timer - This parameter is used to prevent ‘ping-pong’ handoffs between two sectors which have been marked with the DAHO flag. After



a hard hand-in, origination, or termination in a border sector, majority border checks will be disabled for a period of time in seconds equal to the value of this parameter.

HandoffMethod - Handoff Method - This parameter specifies the method (none, hard, soft trunking, soft aplus) to be used to hand the call off to a sector external to the CBSC. The scope of this parameter is per carrier and per external CDMA sector.

Inter-CBSC Soft Handoff Override - This parameter is used to ‘turn-off’ Inter- CBSC soft handoffs between two MMs. It is checked by both source (in handoff detection) and target procedures. When override is allowed, the alternative action of either no handoffs or hard handoffs is indicated (no handoffs, hard, no override). The scope of this parameter is per inter-CBSC trunk group.

AnchorHoMeth - Anchor Handoff Method - This per CBSC parameter indicates the condition upon which trigger the source MM to move a mobile in Inter- CBSC soft handoff from a source (or ‘anchor’) MM to a target MM once all the source legs have been dropped.

Num_Cand - Number Candidates - The maximum number of candidate pilots reported by the mobile station that will be considered, in strength order, for handoff.

ICTRKGRP:: ConnToggle: Indicates whether ICSRCHAN based or IP based inter-CBSC handoff connection type shall be used to conduct the soft handoff.

CBSC:: N-Way Hard Hand Out flag - This flag indicates whether N-way Hard Hand Out is turned on, turn on for hand down only, or turned off.

Sector/Carrier::Radio Configuration Class Capability: This parameter indicates whether the BTS is capable of supporting 2Gvoice and packet data calls only, OR 2G voice and packet data calls and also 3G voice calls, or 2G voice and pacekt data calls and 3G voice and packet data calls, or 3G packet data calls only. The scope of this parameter is per carrier/sector.

CBSC::MSCIntVer: Indicates the IOS compliance of the MSC. This parameter can be set to Pre-3G or IOS_4_1

1.8.1 Complex Soft Handoff Database Parameters To support Complex Soft Handoff, sixteen sets of the following MM database parameters will be supported. All parameters are provisioned on a per CARRIER (carrier/sector) basis. Each CARRIER will point to one of the sixteen sets of available parameters. This will allow flexibility by allowing an operator to quickly alter the parameters affecting the operation of the Complex Soft Handoff feature. The strongest pilot in the MM’s internal active set will determine the set of parameters used for the next detection operation. For performing detection for the first SCAP: Handover Recognized received during a call, the set of parameters associated with the originating/terminating sector will be used.

MaxActSetSz - Maximum Active Set Size - This per CARRIER parameter specifies the maximum number of active legs (both soft and softer) allowed for the call. The maximum number of legs supported by currently deployed mobiles is six. RF : maxactivesetsize

MaxCEPerCall - Maximum Number of channel elements allowed in a call at any one time - This parameter specifies the maximum number of channel elements that may be allowed in a call. Current transcoder design allows only three simultaneous channel element connections.



MaxBTSLegs[N] - Maximum Number of Softer Legs Per BTS - There are three versions of this parameter, one for each of the total number of BTSs that may be involved in the call (range 1 - 3 with current transcoder hardware). The parameter is used to specify the maximum number of softer legs supported per BTS with N number of BTSs involved in the call.

Tcomp_Enab_Thresh - TCOMP Enable Threshold - For shuffle checks, handoff detection requires that the single pilot strength be greater than the value of this parameter before the shuffle is performed. For the case of the active pilot aggregate strength being greater than or equal to AggrStr, the XC/SDU uses this parameter to determine if the PSMM is pursuable, and the MM uses this parameter and XCTComp to determine which candidate pilots are pursuable. RF: tcompenathrsh

AggActLimit[N] - Aggregate Active Limit - This parameter set (three values) defines four buckets for PM statistics. This parameter is used to define buckets for both XC/SDU sub-systems and MM statistics.

EnaSofterShuffle - Enable Softer Shuffle - This parameter determines whether or not softer shuffle checks will be performed on candidate pilots reported to the MM in a SCAP: CDMA Handoff Recognized message from the transcoder subsystem.

EnaBtsShuffle - Enable BTS Shuffle - This parameter determines whether or not BTS shuffle checks will be performed on candidate pilots reported to the MM in a SCAP: CDMA Handoff Recognized message from the transcoder subsystem.

EnaSoftShuffle - Enable Soft Shuffle - This parameter determines whether or not soft shuffle checks will be performed on candidate pilots reported to the MM in a SCAP: CDMA Handoff Recognized message from the transcoder subsystem.

Soft_shuffle_comp - Soft Shuffle Comparison - Used in the soft shuffle check operation to determine if a soft shuffle operation should be performed, given the relative strengths of the candidate pilots. RF: softshufflecomp.

BTS_shuffle_comp - BTS Shuffle Comparison - Used in the BTS shuffle check operation to determine if a BTS shuffle operation should be performed, given the relative aggregate signal strengths of the candidate BTSs. RF: btsshufflecomp.

Softer_shuffle_comp - Softer Shuffle Comparison - Used in the softer shuffle check to determine if a softer shuffle operation should be performed, given the relative strengths of the candidate pilots. RF: softershufflecomp.

AggrStr[N] - Aggregate Active Set Strength Threshold - The MM and XC/ SDU aggregate active set threshold when the number of channel elements ‘N’ (one to three channel elements) are in the active set.

XCTComp - XC/SDU TCOMP - Used in the aggregate strength check of the CPP/SDU to determine whether to send a SCAP Handover Recognized message to the MM. The MM uses this parameter and Tcomp_Enab_Thresh to determine which candidate pilots are pursuable, if the active pilot aggregate strength is greater than or equal to AggrStr.

1.8.2 Pilot Dominance The transcoder filtering function - also referred to as pilot dominance - aims to lower the soft handoff rate and soft handoff factor by reducing unnecessary additions of pilots to the active set. By filtering PSMMs at the XC level, MM utilization is reduced by eliminating unnecessary handoff activity. Often in a call, PSMMs are generated by the mobile with add requests, but the Ec/Io level is relatively poor. In this case, adding the



pilot to the active set would contribute little help to the call, but would increase activity in the MM by requiring a handoff operation and would raise the soft handoff factor. Upon receiving a PSMM, there are three conditions under which the CPP will send a handoff recognized message to the mobility manager:

• Aggregate strength of the “keep”* active pilots is less than AggStrengthN

• Strongest candidate is XCTComp greater than any “keep” active and greater than TCompEnaThrsh

• TDrop event

*A “keep” active refers to an active pilot in a PSMM with the keep flag set to one.

The aggregate strength check is done to eliminate the need to add more pilots when the active set already exceeds a certain Ec/Io value. If the active set does not meet this value, a handoff recognized message is passed to the MM for handoff consideration. However, if the active set does meet this threshold, a second “back door” check is done to allow a strong candidate to be added even though the active set is relatively strong. It requires that the candidate be stronger than a minimum threshold (TcompEnaThrsh), and that it exceeds the strength of the weakest active pilot by some level (XCTComp). This back door check helps to ensure that the filter does not cause more dropped calls to occur under rapidly changing pilot conditions. To help guard against dropped calls due to discarded PSMMs, an enhancement is added to the pilot dominance algorithm. The enhancement uses PMRMs (Power Measurement Report Messages) generated by the mobile to trigger additional PSMMs. When a PSMM is discarded by the transcoder, a flag is set. If a PMRM is subsequently received and the flag is set, the aggregate strength of the pilots in the PMRM is compared to the appropriate AggStrengthN threshold. If the aggregate strength is below this threshold, a PMRO (Pilot Measurement Request Order) is sent to the mobile requesting another PSMM, and the flag is reset.

1.9 RF Measurements Used in CDMA Handoff and Power Control Detection While TDMA systems offer a plethora of RF related measurements to use in handoff detection, CDMA seems to be rather sparse in this regard. Nevertheless, there appears to be some latitude for creativity in this area. The list below elaborates on the usefulness of each measurement. Specific usage of measurements can be found in the procedures sections dealing with handoff and power control. Due to the particulars of the CDMA air interface, it will not be possible to use the GSM 05.08 algorithm to perform handoff detection. Instead, CDMA relies on the mobile station to provide an event to the infrastructure equipment to serve notice that a threshold has been crossed as well as provide MAHO measurements to assist in establishing target suitability.

For handoff, the main piece of data to contend with is the contents of the pilot strength measurement message. The RF: Pilot Strength Measurement Message or RF: Extended Pilot Strength Measurement Message is sent autonomously by the mobile station in response to a particular pilot crossing the T_ADD, T_COMP, or T_DROP thresholds. The message contains PN phase measurements and strengths of the pilots that the mobile station is monitoring. The PN phase measurements are in chip offsets relative to the zero phase pilot offset (i.e. relative to system time).

The pilot strength measurement is actually a chip to noise power ratio whose value is always less than 1.0. The mobile returns a logarithmic compression of this measurement equal to



��

��

�×−

010log102

I

Ec

Where Ec is the received pilot energy per chip and I0 is the total received spectral density (note this results in the higher the value the lower the measurement, and vice-versa). Thus, pilot strengths and PN phase will be used in tandem both to determine the need to handoff as well as choose appropriate targets.

On the reverse link, frame errors or frame quality depending on the frame rate is detected by the MCC. The frame quality and data rate will be reported by the MCC in the encoded frame to the selector. The selector determines frame erasures from this information. A frame erasure rate (FER) can be generated in the XC/SDU after a sufficient number of frames have been received to begin forming the statistic. Typically, 1% of the frames in error will be tolerated in the system for a voice application. Note that due to soft handoff, the reverse FER for a call is not necessarily determined by an individual MCC circuit. Reverse FER is determined after frame selection from all MCCs involved in the call.

On the forward link, frame errors are detected by the mobile station and reported to the base station equipment in the RF: Power Measurement Report Message or EIB. This RF: Power Measurement Report message contains the number of errors detected over a certain number of frames. The mobile station may send this message either periodically or when a threshold of bad frames has been reached. The message also contains a report of pilot strengths for pilots included in the current mobile station active set.

All soft handoff decisions are based on the Ec/Io information and the “keep-flag” status from the PSMM (Pilot Strength Measurement Message) sent by the mobile station. The PSMMs are triggered when a Tadd, Tcomp, or a Tdrop event occurs. The soft handoff parameters are set on a sector basis, and are sent to the mobile station by the System Parameter Message on the Paging Channel or by the Extended Handoff Direction Message on the Forward Traffic Channel.

The System Parameter Message is sent at least once every 1.28 seconds over the Paging Channel. The Extended Handoff Direction Message is sent each time a handoff criteria is met. If there are more than one sector in the Extended Handoff Direction Message (i.e. calls that are instructed to transition into a soft handoff state), the MM will use the following criteria in selecting the soft handoff parameters in those instances when the values are different for each of the involved sectors (Figure 1):

1. The value of TDrop shall be the largest value from each of the sectors involved

2. The value of TAdd TComp and TTDrop shall be the smallest value from each of the sectors2

3. The value of SrchWinA, SrchWinR, SrchWinN shall be the largest value from each of the sectors involved



Figure 1 Parameter derivation during Handoff

1.9.1 Pilot ordering for Neighbor lists The neighbor list at the mobile station will be updated (via the Neighbor List Update Message on the TCH) provided that one of the following conditions is met:

• Always send a Neighbor List Update on a handoff add situation (either soft or softer).

• Send a Neighbor List Update on a handoff drop situation only if the last time the list was sent to the mobile station had to be truncated (i.e. was > N8m, or 20, neighbors)

The maximum number of pilots in a neighbor list created by the base station is 20 neighbor pilots. The MM will enter the neighbor pilots into the list in the order of decreasing priority, as determined by the order of the neighbors in the system database. In the case of the mobile station having more than one pilot in the active set, the MM will “merge” the database entries in a round robin order. When the total amount of neighbor pilots associated with each of the pilots in the active set exceeds 20, the lowest priority neighbors will be truncated off the list. Please refer to the following Soft Handoff Neighbor List “Merge” Example (Figure 2).



Figure 2 Neighbor List Merging

The NGHBR_MAX_AGE parameter is recommended to be set to 0, as the list will always contain the most updated neighbors. This will prevent the mobile station from leaving “aged” pilots in the neighbor list; thus, forcing a direct replacement.

1.10 CDMA Cellsite Receive Antenna Selection During a call, and regardless of soft or softer handoff conditions, the MCC will need to check for significant reverse channel energy on a per sector basis related to the call Figure 3). When finding a signal with significant energy that exceeds the energy being used by one of the fingers, the MCC shall dedicate a finger to that new signal. If the signal drops below another threshold, then the finger is dropped from combining. The MCC is configured to operate in a sectored or omni mode. This is to prevent wasted processing time looking for signals where there are no sector inputs.



Figure 3 Reverse Channel Link Management

2 Reverse Channel Power Control

2.1 Introduction In the current CDMA system, the reverse power control procedures are based upon a Motorola method which has been created from system and channel simulations in the receiver technology group and receiver performance testing both on the bench and in the field.

Note that only the MCCce being assigned as fundamental channel does the reverse power control.

2.2 Open and Closed Loop Reverse power control consists of open and closed loop components. The open loop, which is performed at the mobile (Figure 4), accounts 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, relatively slow (with respect to the closed loop)



generating new updates roughly every 20 ms. The amount of mobile transmit power necessary to close the reverse link is estimated by subtracting total noise plus interference measured at the mobile antenna from a “turn around” factor (k). The open loop mobile transmit power estimate will be re- fined by reverse closed loop power control.

mr

mt PkP −=

WIWIWNWN cootho ++=

Where, mtP is the transmitted power from the serving mobile to the base station, m

rP is

the total power measured at the mobile antenna, WN th is receiver thermal noise and

other non-CDMA system noise, and ambient noise components, oI is the home cell

power spectral density, and coI is the other CDMA cell interference power spectral

density.

Figure 4 Mobile Power Control Schematic

The closed power control loop consists of an inner and outer loop. The outer loop is maintained at the base station and involves feedback based on frame erasures (FE) to determine an Eb/No setpoint in order to maintain a constant FER. The inner loop is distributed between the mobile and the base station where the feedback mechanism is based on the power control bit (PCB). The closed loop accounts for non-symmetrical (uncorrelated) losses between the reverse and forward links due to Raleigh/Rician (fast) fading, interference level variations (e.g. voice activity or loading), differences in an antenna’s transmit and receive gain, and other associated losses (combiners, connectors, duplexers, etc.). It is the fast power control loop being updated at an 800 Hz



rate (once every power control group) that effectively mitigates small to medium power variations due to fast fading. Fast power control is most effective at slow speeds where interleaving is not. (Note: the smaller the power swings or variations measured at the serving base station for each mobile the smaller can be the transmitted mobile power necessary to achieve a 1% FER. This lower required power level results in less interference and hence allows more channels to be supported.) The portion of the closed loop reverse link power control algorithm performed at the base station is shown in Figure 5,

Figure 5 BTS Power Control Schematic

2.3 Reverse Power Control Algorithm

2.3.1 Inner Loop Referring to Figure 5, Reverse Power Control Outer Loop & BTS portion of Inner Closed Loop, above the inner loop of the reverse power control algorithm is now summarized.

For each Walsh symbol interval (n) compute the winning Walsh symbol energy (Ewin) obtained from the combined correlation vector determined from the FHT output of each demodulator (finger) that is locked.

Compute Power Control metric m(n) = Ewin/k where k is a scale factor.

Compute Power Control Group metric (M) from the six winning Walsh symbols during a PCG interval.

( )�=

=5

0n

nmM



Compare M to the Outerloop threshold to determine whether to increase or decrease mobile TX power via a power control bit (PCB) multiplexed on the forward traffic channel link.

The number of fingers (demodulators) in lock is accounted for when applying the outerloop power control (instantaneous) threshold (PCT). The adjusted outerloop power control threshold used to compare to M is obtained from a set of four registers updated every time the outerloop power control algorithm is executed (20ms) and indexed based on the number of fingers locked. These registers, hence, contain the current adjusted outerloop power control threshold corresponding to the number of fingers in lock. Register 1 and 2 are loaded with the outerloop power control threshold directly adjusted by the outerloop power control algorithm and correspond to the case where 1 and 2 fingers are locked respectively. Register’s 3 and 4 contain outerloop power control threshold +500 and +1000 units respectively and correspond to the case when 3 and 4 fingers are in lock, again respectively. The offsets used for the 3 and 4 finger case account for the increase in the energy of M due primarily to the demodulation noise of the new finger. The signal associated with the new finger consists mainly of noise since typically the Eb/No of the finger will be low at the time of lock. Applying this offset in the manner described above prevents a possible frame erasure from occurring whenever a new finger is added and makes the adjustment transparent to the outerloop power control algorithm.

Power is changed at the mobile by transmission of the Power Control Bit (PCB) by puncturing coded symbols on the forward traffic channel link of the serving BTS every 1.25 ms. The mobile transmit 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 algorithm performance 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 8.

Delay in sending and applying the PCB degrades reverse power control performance. The error rate of the PCB also has a performance impact especially during soft and softer handoff. 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-98B requires that during soft handoff a mobile must ignore a link’s PCB if the finger’s Ec/Io falls below some threshold. This threshold level is left up to the mobile manufacturer. This requirement along with diversity combining PCB’s during softer handoff can help reduce the required PCB gain.

2.3.2 Outer Loop Outer loop power control executes once every 20 ms using the current frame’s rate decision as an input to the process of updating a channel’s power control threshold (PCT) and power control target threshold (PCTT). The power control threshold is used by the inner loop of power control as a means of estimating the mobile’s instantaneous power output in a power control group so that the base station can send a valid power up or power down to the mobile in the following power control bit. The power control target threshold is used by the outer loop power control algorithm as a means of keeping the current full rate frame erasure rate constant at an assigned target FER while accommodating for any sudden changes in velocity at the mobile.



2.4 Database Parameters

• repframes Forward Power Control Reporting Frame Count. Specifies the number of frames over which the MS will count bad frames in order to transmit the power measurement report message. Also used as the number of frames for periodic reporting. The parameter is converted to frames in the MS by the following equation: frames = [2(PWR_REP_FRAMES/2) x 5] Please refer to applicable IS-95 standard for complete definition. Valid range 0-15. Optional parameter; if skipped, uses current value. Initial standard value 9.

• thrshenable - Forward Power Control Threshold Report Mode Indicator. Enables MS to transmit threshold generated power measurement report messages. Please refer to applicable IS-95 standard for complete definition. Valid range DISABLE, ENABLE. Optional parameter; if skipped, uses current value. Initial standard value ENABLE.

• repthrsh - Forward Power Control Reporting Threshold. This parameter specifies the number of bad frames received by the MS during a measurement period before the MS will transmit a power measurement report message (if threshold reporting is enabled). Please refer to applicable IS-95 standard for complete definition of its use within the System Parameters Message. Valid range 0-31. Optional parameter; if skipped, uses current value. Initial standard value 3.

• reportdelay - Forward Power Control Report Delay. The period that the MS delays before restarting its bad frame counter after sending a power measurement report message. Its value is in units of 4 frames. Please refer to applicable IS-95 standard for complete definition. Valid range 0, 4, 8, ..., 120, 124 frames. Optional parameter; if skipped, uses current value. Initial standard value 8.

• periodenable - Forward Power Control Period Report Mode Indicator. Enables MS to transmit periodic power measurement report messages. Please refer to applicable IS-95 standard for complete definition. Valid range DISABLE, ENABLE. Optional parameter; if skipped, uses current value. Initial standard value DISABLE.

• maxebno - Reverse Power Control Maximum Eb/No. 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 MCC. Valid range 2.0 - 14.9 dB, 0.1 Increments. Optional parameter; if skipped, uses current value. Initial standard value 11.0.

• nomebno - Reverse Power Control Nominal Eb/No. Specifies the Eb/No starting point of the power control threshold. This data is used to derive the threshold used on the MCC. Valid range 2.0 - 14.9 dB, in 0.1 increments. Optional parameter; if skipped, uses current value. Initial standard value 9.0.

• minebno - Reverse Power Control Minimum Eb/No. 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 MCC. Valid range 2.0 - 14.9 dB, in 0.1 increments. Optional parameter; if skipped, uses current value. Initial standard value 6.0.



• cdlthresh - High Set Point Count Threshold. The threshold for the number of consecutive times during a call that a TCH was unable to increase the reverse channel set point due to maximum set point ceiling. The threshold is used for the Reverse TCH Power Control Metric stored in the CDL. Valid range 0 - 255. Optional parameter; if skipped, uses current value. Initial standard value 128.

• rpcmaxecio - This is the minimum reverse pilot channel chip energy to spectral energy ratio. The range is: -31.875 to 0 dB, in 0.125 increments. The default is: -22.00. This is an optional parameter.

• rpcnomecio - This is the nominal reverse pilot channel chip energy to spectral energy ratio. The range is: -31.875 to 0 dB, in 0.125 increments. The default is: -23.00. This is an optional parameter.

• rpcminecio - This is the maximum reverse pilot channel chip energy to spectral energy ratio. The range is: -31.875 to 0 dB, in 0.125 increments. The default is: -25.00. This is an optional parameter.

3 Forward Channel Power Control

3.1 Introduction This section discusses the forward power control mechanisms provided by the SuperCell system.

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 the amount of forward link power dedicated to a mobile station and the forward link voice quality that mobile station will experience. The power control algorithm must balance power against acceptable voice quality.

The CDMA air interface IS-95 [3] provides a mechanism for forward power control but does not specify the algorithm for the infrastructure to implement. IS-95 allows the infrastructure to control how a mobile station generates and transmits RF: 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. J-STD-008 and some IS-95 standards support Erasure Indicator Bit (EIB) for Rate Set 2 calls. The EIB indicates whether a forward frame was an erasure frame or not. This is a good indication of whether the forward power gain should be adjusted or not.

Rate Set 1 and 2 calls

The basic idea of the algorithm is that the MCCs will periodically reduce a traffic channels forward gain setting will be periodically reduced. Reducing the gain has the effect of reducing the power delivered to a mobile station. At some point, the MCCs may reduce the gain may be reduced to a point where acceptable voice quality is no longer being delivered to the mobile station. The mobile station will generate and transmit the RF: 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 XC receives the PMRM and determines that the error threshold has been reached. The XC then sends the SCAP: CDMA Increase Forward Gain Message to the MCCs involved in the call. Upon receiving this indication, the MCCs will increase the current forward channel gain setting restoring voice quality to an acceptable level.The MCCs then restart tThe periodic gain reductions will then be restarted.

3.2 Algorithm Specifics The automatic forward power control algorithm specified in this version of the SFS is the algorithm currently implemented in the CDMA simulator. The algorithm is based on the Qualcomm algorithm as specified in the paper “Power Control Issues”. Note that the gain redistribution described in this paper is not being used. There are at least two advantages to this equal gain approach:

• Allows optimization of the forward link by minimizing soft handoff region size.

• Allows for constant fraction of traffic channel power to pilot power for all forward links corresponding to a particular mobile which is helpful (although not necessarily optimal) when the mobile is weighting its fingers based on finger Ec/Io for combining.

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 that when a mobile station comes to rest in a good coverage location long enough such that its power level drops significantly. When the mobile station resumes motion, it 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 TCH gain floor (minimum gain threshold) and ceiling (maximum gain threshold) as well as a nominal gain threshold to be set as a function of the number of forward links determined by the handoff state. It is expected that minimum gain threshold setting can be lowered for the 2 and 3 forward link case because the stop sign effect has a much higher probability of being mitigated for this case than for the single forward link case. That is, due to the channel characteristic achieved with multiple forward links a single gain increase performed on reception of a RF: Power Measurement Report Message (PMRM) is enough to mitigate further frame errors. The nominal thresholds are used for synchronization of TCH gain on adding soft forward links and for reducing interference when the TCH gain is above the nominal level on adding soft or softer forward links. The nominal thresholds are chosen to be at a level that would be slightly less than the expected TCH gain would be for a loaded system. Although not done in practice it is also possible to set the maximum gain threshold differently dependent on the number of forward links. Depending on system design (including handoff parameter settings) the diversity benefit of soft/softer hand off can exceed the degradation caused by the additional interference found in multi-coverage areas. When this is the case, the 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 current system requires that power control and control channel parameter settings be input as digital gain settings. Conversion back and forth between gain settings and ERP is possible.

Care must be taken in setting the parameter values which affect how the mobile station generates RF: Power Measurement Report Messages (PMRMs). It is possible to cause the mobile to send this message every 5 frames (every 100ms). Not only is this likely to



significantly degrade reverse link voice quality, but also depending on how many mobile stations there are the XC could be overloaded attempting to process the messages.

This algorithm does not presume that PMRMs are being generated in either the threshold or periodic modes. Anytime a PMRM is received, the number of errors is compared with a threshold. If the threshold is reached, the MCCs are requested to increase the forward gain settings.

Note that if threshold reporting is turned on, the parameter FwdPwrThresh must be set to be less than or equal to PwrRepThresh. If it is not, the XC will never detect excess errors and consequently the forward power control algorithm will not work.

3.2.1 Gain 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. The values 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) = 0.75Ppilot

Ppage(4800) = 0.40Ppilot

Psync(1200) = 0.10Ppilot

Where,

Ppilot is pilot power at the top of the site interface frame (SIF)

Ppage is the page power at the top of the SIF

Psync is the sync power at the top of the SIF

The pilot, page, sync, and traffic channel powers are set by setting corresponding digital gain levels which are proportional to voltage. Hence, we have the relationship:

Ppage = (rate/9600bps)*(Gpage/Gpilot)^2*Ppilot

Ptch = (Gtch/Gpilot)^2*Ppilot

Where rate is the baud rate of the paging channel. Note traffic channel gains are full rate.

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

= [1+X/Gtch1]^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 increase

X is the traffic channel gain increase

The dynamic range of a TCH can easily be derived:

Ptch_max = (Gtch_max/Gpilot)^2*Ppilot where Gtch_max = 127 (currently)



Ptch_min = (Gtch_min/Gpilot)^2*Ppilot where Gtch_min = 1

Fixed pilot gain settings are used and do not vary 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.

Setting Power Control Bit (PCB) Gain Levels:

The power control subchannel is described along with the relationship between reverse link closed loop power control performance and forward link capacity that is determined by the PCB gain settings used. Note that the PCB setting is only performed by the fundamental channels.

3.3 Power Control Bit Description In IS-95A a power control subchannel is created to allow close loop reverse power control by puncturing (replacing) TCH symbols with power control bits (PCBs) on each forward link. Two traffic channel (TCH) symbols are replaced every 1.25 ms (also known as a power control group (PCG) interval) for Rate Set 1 operation to offset the processing/coding gain loss (no convolutional coding benefit). For rate set 2 only 1 TCH symbol is replaced per PCB. In the case of soft handoff where there are multiple BTS forward links the PCBs are voted such that the mobile always powers down (PCB=1) by 1 dB unless all the bits indicate to power up (PCB=0) in which case the mobile powers up by 1 dB. In the case of softer handoff or multiple rays due to delay spread the PCBs from each mobile demodulator (finger) can be diversity combined.

3.3.1 PCB Error Rate Effect The effectiveness of the reverse power control loop for a single link begins to degrade (causes significant increase in required 1% FER Eb/No) as the PCB error rate exceeds 10% (see Figure 6 below based on Markov source). During Soft Handoff forward link imbalances can cause high PCB error rates with respect to the weaker link. This can impair voting such that the mobile fails to power up when necessary or, in some cases, even powers down for a significant time duration when it should really be powering up. This SHO problem is mitigated to some degree by IS-98 9.3.8 which specifies that a PCB should not be used to vote if the corresponding mobile finger's Ec/Io falls below a certain threshold. Note that this threshold is usually left up to the mobile manufacturer. So far this threshold is typically based on whether the mobile demodulator (finger) is locked or not where the finger locking threshold ranges from -18.75 dB to -25.00 dB



Figure 6 Eb/No V/s PCB Error Rate

3.4 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 it’s 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-95).

PWR_THRESH_ENABLE - enable threshold method for sending PMRM message

PWR_PERIOD_ENABLE - disable periodic method for sending PMRM message

PWR_REP_FRAMES - (corresponding mobile parameter TOT_FRAMES)

PWR_REP_THRESH - (corresponding mobile parameter BAD_FRAMES)

PWR_REP_DELAY - 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.

3.5 Forward Power Control in Different SHO States. When an IS-95 mobile originates, it’s initial forward link power is set to the level given by OrigGain. After the mobile has changed handoff state (gone into 2 or 3 way soft/softer handoff) 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 whenever it runs into a high interference area. That is, it is assumed that all high interference areas coincide with soft or softer handoff 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 7below is a state diagram describing forward power control of a fundamental channel. Note the transition between the 1-way and 3-way states is not



shown. For a supplemental channel, the Min, Nom, and Max gain corresponding to a handoff state will be factored by a parameter Supp_Scale_Factor received in the SCAP: CDMA Supplemental Channel Assignment or SCAP: CDMA RF Supplemental Resource Configure message.

Figure 7 Power Control State Diagram

3.6 Database Parameters The following are the system database parameters which apply to forward power control. These are provided in this document as a convenience to the reader. Please refer System Command Reference Manual for additional information and default values.

• MinGain1 - 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.

• NomGain1 - 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, termination or hard handoff (see OrigGain).

• MaxGain1 - 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, termination or hard handoff (see OrigGain). The MCC channel elements increase gain levels as directed by the XC.

• MinGain2 - This is the lowest forward traffic channel digital gain level to which the MCC will “trickle down” when a mobile is in a 2 way soft or softer handoff.

• NomGain2 - This is the starting forward traffic channel digital gain level for a mobile which has entered a 2 way soft or softer handoff.

• MaxGain2 - This is the maximum forward traffic channel digital gain level for a mobile which is in a 2 way soft or softer handoff. The MCC channel elements increase gain levels as directed by the XC.



• MinGain3 - This is the lowest forward traffic channel digital gain level to which the MCC will “trickle down” when a mobile is in a >=3 way soft or softer handoff.

• NomGain3 - This is the starting forward traffic channel digital gain level for a mobile which has entered a >=3 way soft or softer handoff.

• MaxGain3 - This is the maximum forward traffic channel digital gain level for a mobile which is in a >=3 way soft or softer handoff. The MCC channel elements increase gain levels as directed by the XC.

• PchGain - Specifies the gain setting for a sectors paging channel.

• 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.

• OrigDelay - This is the amount of time (specified as a number of air interface frames) an MCC channel element waits after an origination, termination, or hard handoff 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.

• 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. TheMMsends this parameter to the XC in the SCAP: CDMA XC Channel Assigned message, the SCAP: CDMA XC Handoff Direction message, and the CDMA XC Hard Handoff Channel Assigned message This parameter is closely related to PwrRepThresh and must be set with this in mind.

• PwrThreshEna - Enables threshold reporting mode (as specified in IS-95) in the mobile station. Sent to the mobile station in the RF: System Parameters Message as PWR_THRESH_ENABLE.

• PwrPeriodEna - Enables periodic reporting mode (as specified in IS-95) in the mobile station. Sent to the mobile station in the RF: System Parameters Message as PWR_PERIOD_ENABLE.

• PwrRepThresh - If threshold mode reporting (as specified in IS-95) is enabled, this is the number of frame errors which will cause the mobile station to send an RF: Power Measurement Report Message. This 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 will count frame errors. This parameter can be set to certain values between 5 and 905 frames (refer to IS-95). 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.

• 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 is used in specifying the final factor the MCC card multiplies the current full rate forward channel gain setting to determine what the power control bit gain should be set to. Its range is 0.25 - 5.00, increments of 0.25. Optional parameter; if skipped uses current value. Initial standard value 1. Note that the PCB gain is also a function of the number of forward links active.

handoff & power control application note

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