CdmaOne (IS-95A/B) 1.

cdmaOne (IS-95A/B) 1

References Viterbi, Andrew J. (1995), CDMA Principles of Spread Spectrum Communication, Addison-Wesley, ISBN Lee, William.C.Y. (1995), Mobile Cellular Telecommunications, 2nd Edition, McGraw Hill, ISBN Gilhousen, K.S., Jacobs, I.M., Padovani, R., Viterbi, A.J., Weaver, L.A. and Wheatley, C.E. (1991), “On the Capacity of a Cellular CDMA System”,” IEEE Trans. on Vehicular Technology 40(2), Rappaport, T.S.; Wireless Communications Principles and Practice; Prentice-Hall; 1996; ISBN TIA/EIA Interim Standard 95A and ANSI J-STD-008, available through: Global Engineering Documents 15 Inverness Way Englewood, CO 80112

Introduction

TIA/EIA-95 and related standards.
Describes a family of related services including: cellular, PCS, Fixed Wireless, and satellite communications.

ANSI J-STD-008 Requirements for 1. 8 to 2
ANSI J-STD-008 Requirements for 1.8 to 2.0 GHz CDMA Personal Communications System (PCS) Requirements For PCS Operation Requirements For Base Station CDMA Operation Message Encryption & Voice Privacy CDMA Call Flow Protocol Layering CDMA Constants CDMA Retrievable & Settable Parameters Personal Station Database

TIA/EIA-95 TIA/EIA-95 = IS-95A + TSB-74 + J-STD-008 - Analog Details
+ Corrections + New Capabilities

Conventional Approaches
FCC Allocations

The CDMA “Cocktail Party”
“Guten Tag” “Bonjour” “Shalom” “Hello” “Buenos Dias”

CDMA Cellular Network Architecture

Cells and Sectors Sector Sector Sector Cell

Terminology: Bit, Symbol and Chip
add check bits Information A/D Mux Information Bits Code Symbols FEC Code Generator Spreader PSK + Chips Chips

A/D PCM 4K 8K 64K Analog Signal LPF Sample Clock Quantize Digital
Binary Encode

Error Detection Codes Block of data bits CRC Bits
Additional check bits CRC Bits

Error Correction Codes
Noise errors { 1 11111 11001 1 Repeater Channel Receiver

CDMA is Spread Spectrum
C = W log2(1 + S/N) C = Capacity (bps) W = Bandwidth (Hz) S/N = Signal-To-Noise Ratio S = Signal Power N = Noise Power

BPSK 1 1 Digital Signal BPSK -sinwct (logic 0) sinwct (logic 1)

QPSK 10 00 11 01

OQPSK tb b0 b1 b2 b3 b4 tb a0 a1 a2 a3 I-Channel Input Data Q-Channel

Fading 5V 5V 5V 5V

Coherent/Non-coherent
FWD RVS

Signal-to-Noise Ratio
PS PN SNR=10 LOG

Correlation +1V +1V -1V -1V +1V +1V -1V +1V 0 V -1V
Complete Correlation No Correlation

Eb/No In Digital Communication Systems Eb/No is Used
Tx 1 Rx 1 1 1 Eb/No = (PS/PN)(W/R)

Design Considerations

Multipaths

Delay Profiles

Shadowing Signals are Blocked by an Obstacle
Forward and Reverse Links are impacted in the same way

Fast Fading Reflections can combine destructively
Reverse Link Fading is independent of Forward Link Signal Strength Reverse Link Forward Link Distance

Frequency Selective Fading

Rate of Fading

Spread Spectrum Principles

Spread Spectrum Direct Sequence
RF modulated with m(t) BPSK or QPSK Modulator s(t) PN Stream Data m(t) PN Clock Spectrum s(t) f Modulator Generator

Capacity W = 1.288MHz R= 9.6Kbps Ga= Sectorization gain for 3 sector site 2.65 Gv = voice activity gain = 1/0.4 h= Ratio of thermal noise density to total interference density = 0.05 F = Reduction Factor due to imperfect power control =0.75 f = Other cell Interference Factor = 0.55 Eb/No= 3.5dB=2

Applications Cellular PCS Fixed Wireless Satellite

Cellular Spectrum A” ////// (1 MHz) CDMA CDMA A (10 MHz) ////// //////
Transmitter Frequency Assignment(MHz) Mobile Base Valid CDMA Frequency Assignments Analog Channel Count CDMA Channel Number System A” (1 MHz) ////// 880,650 835,650 991 1012 1013 1023 1 311 312 333 334 355 356 644 645 666 667 688 689 694 695 716 717 738 739 777 778 799 22 11 289 6 39 CDMA CDMA A (10 MHz) ////// ////// B (10 MHz) CDMA ////// ////// A’ (1.5 MHz) CDMA ////// ////// B’ (2.5 MHz) CDMA //////

A Cellular CDMA Channel
Reverse CDMA Channel Forward CDMA Channel 1.25MHz 1.25MHz CDMA Channel Frequency Frequency 758 MHz 45 MHz 758 MHz

Transmitter Frequency Assignment(MHz)
PCS Spectrum Valid CDMA Frequency Assignments CDMA Channel Number Transmitter Frequency Assignment(MHz) Personal Station Base Station Block Designator Not Valid 0 - 24 A (15 MHz) Valid Cond. Valid Cond. Valid D (5 MHz) Valid Cond. Valid B (15 MHz) Cond. Valid Valid Cond. Valid Cond. Valid E (5 MHz) Valid Cond. Valid Cond. Valid F (5 MHz) Valid Cond. Valid Cond. Valid C (15 MHz) Valid Not Valid

A PCS CDMA Channel Reverse CDMA Channel Forward CDMA Channel 1.25MHz
Frequency Frequency 25 MHz 80 MHz 25 MHz

Frequency Reuse in FDMA and TDMA Systems
Cell 1 Cell 2 If Cell 1 and Cell 2 were both on the same frequency in conventional cellular systems, the overlap area would have a frequency conflict.

Frequency Reuse Pattern of 7
D E F G B C A

CDMA Frequency Reuse A

Power Control is Required
Near-far Problem Path Loss Fading

Soft Handoff

Better Use of Multipath
BSC Cell The mobile can adjust for differing path delays and phase shifts of the different multipath arrivals and then combine the arrivals coherently.

Rake Receiver Correlator 1 Combiner Correlator 2 Correlator 3 Searcher

Variable Rate Vocoder Codec Vocoder about 200 milliseconds
CDMA takes advantage of periods of reduced speech activity

Variable Rate Vocoder Vocoder Data Rates Rate Set 1: 9600bps TX Rate
Vocoder Rate 8550 4000 2000 800 Tx Rate 9600 4800 2400 1200 Full Half Quarter Eighth Vocoder Data Rates Rate Set 2: 14.4Kbps TX Rate Vocoder Rate 13300 6200 2700 1000 Tx Rate 14400 7200 3600 1800 Full Half Quarter Eighth

Framing for Rate Set 2 (1 frame generated every 20 msec)
Mode Bit Full Rate 1 267 bits 12 bit CRC 8 Tail Bits Half Rate 1 125 bits 10 bit CRC 8 Tail Bits Quarter Rate 1 55 bits 8 bit CRC 8 Tail Bits Eighth Rate 1 21 bits 6 bit CRC 8 Tail Bits

Capacity CDMA TDMA Analog
Ref: Overview, Sects , pp 14-17; sec 4.1, pp19-26 All of the features and attributes discussed so far contribute to the capacity of a CDMA System. As a result, the capacity of a CDMA System is more than 10 times that of current analog systems. CDMA TDMA Analog

service with smaller margin. operation at lower Eb/Io.
Greater Coverage The Eb/Io received is normally the amount that’s required plus some margin. In CDMA systems, the Eb/Io required is generally lower because strong Convolutional codes are applied to all of the information bits, rather than to just some of the bits. The margin required is also lower due to the Soft Hand-off capability. These combine to produce a significant range advantage. The amount of advantage is situation dependent and is impacted strongly by the terrain. CDMA has a 5-10 dB link budget advantage which results in a significant range advantage (Eb/Io)received = (Eb/Io)required + Margin Soft Hand-off enables CDMA to provide acceptable level of service with smaller margin. Strong coding enables operation at lower Eb/Io.

Fixed Wireless (Wireless Local Loop)
Operation and Maintenance Center Base Station Manager Home Location Center Radio Frequency Unit Network Interface Switch CDMA Interconnect Selector Bank Local Exchange Backhaul Interface Digital Shelf Call Control Process Radio Transceiver BSC BTS

Globalstar Low Earth Orbit Satellite System
Gateway Gateway SOCC Prime Alternate GOCC Prime Alternate Worldwide Coverage Providing Voice, Data, Fax, Paging & Position Location Fixed & Mobile Users Constellation of 48 LEO Satellites CDMA Technology

Codes in CDMA 53

Introduction Orthogonal Codes Pseudorandom (PN) codes

0000 0101 Orthogonal Sequences Example:
Orthogonal functions have zero correlation. Two binary sequences are orthogonal if the process of “XORing” them results in an equal number of 1’s and 0’s. Example: 0000 0101

Generating Orthogonal Sequence
0 0 0 1 SEED Repeat Right Below Invert (diagonally)

Walsh Codes

Orthogonal Spreading 1 Walsh Function #59 Pattern to be Transmitted
Walsh Function #59 Pattern to be Transmitted

Orthogonal Spreading +1 -1 1 1 1 User Data Orthogonal Sequence 0 1 1 0
1 1 User Data Orthogonal Sequence Tx Data +1 -1

Decoding Using a Correct Orthogonal Code
Rx Data Correct Function 1 1 1 +1 -1

Decoding Using an Incorrect Orthogonal Code
Rx Data Incorrect Function ? ? ? ? ?

Example: Spreading Spread Waveform Representation of User A’s signal
+1 A=00 Walsh Code for A = 0101 -1 Spread Waveform Representation of User B’s signal +1 B=10 Walsh Code for B = 0011 -1 +1 Spread Waveform Representation of User C’s signal C=11 Walsh Code for C = 0000 -1 Analog Signal Formed by the Summation of the Three Spread Signals +1 -3

Despreading Received Composite Signal +1 -3
Walsh Code for User A = 0101 +1 -1 +3 Product -1 Average=(5-1)/4=1 Average=(5-1)/4=1 “0” “0”

Pseudorandom Noise (PN) Codes
Two Short Codes (215 = 32,768) Termed “I” and “Q” codes (different taps ) Used for Quadrature Spreading Unique offsets serve as identifiers for a Cell or a Sector Repeat every msec (at a clock rate of Mcps) One Long Code (242= 4400 Billion) Used for spreading and scrambling Repeats every 41 days (at a clock rate of Mcps)

Autocorrelation of a PN Code
(# of agreements - # disagreements)/N -1/N 1 PN Chip Period of the Code

+ PN Code Generation 1 Seed Register with 001
Out 1 Seed Register with 001 Output will be a seven sequence digit that repeats continuously

PN Code Generation + + + + + + + 1 1 1 1 1 1 1 1
1 + + 1 1 1 + + 1 1 1 1 Sequence = + + 1 1 1 1 Clock Pulse D3 D2 D1 1 2 3 4 5 6 7

PN Offset (Masking) Masking will cause the generator to produce the same sequence, but offset in time. Out 1 +

Sequence Produced by a Masked Generator
1 1 1 1 1 1 1 1 1 1 Sequence = 1 1 1 1 1

Lookup Table for PN Offsets
Mask 001 010 011 100 101 110 111 Offset (in chips) 7 6 4 5 1 3 2 Transmitted Sequence

Physical Layer 71

Forward Traffic Channel Generation
Ref: Overview, pg. 31, Sect 4.3.1

Filtering & Up Conversion
Forward Traffic Channel

Convolutional Coding Convolutional Coding

Rate 1/2 Coding Convolutional Coding, Rate 1/2, Constraint Length 9

Rate 3/4 Coding Rate 3/4 coding is achieved by puncturing the symbol stream output from a Rate 1/2 coder. Every 3 bits will result in 6 symbols produced by the Rate 1/2 coder. Of these 6 symbols, only 4 will be transmitted. 2 will be deleted or “punctured” according to a fixed pattern. This fixed pattern enables the receiver to identify the position of the missing symbol, then attempt to decide on the proper value of each missing symbol using the error correcting capability of the code.

Coding Gain Uncoded BPSK Rate 1/2 K = 9 10-1 10-6 Bit Error
Probability Eb/No (dB) 11 dB 4 dB Rate 1/2 K = 9

Symbol Repetition Rate Set 1

Symbol Repetition reduces the “energy per symbol” requirement.
EnergySYM = Power X DurationSYM Redundant symbols reduce the “energy per symbol” requirement. Lower energy in a symbol = lower power level = lower interference

Interleaving

Interleaving @ Full Rate
Forward Traffic Channel Full Rate Interleaver Output Array R E A D W R I T E Full Rate Interleaver Input Array

Interleaving @ Half Rate
Input Output

Interleaving - No Transmission Errors
D*QD*QD*QI*UI*UI*UG*AG*AG*AIBLIBLIBLTYCTYCTYCA*OA*OA*OL*ML*ML*M**M**M**M OUT READ IN READ OUT D I G I T A L * * * * B Y * * * Q U A L C O M M DECODE

Interleaving - With Transmission Errors
D*QD*QD*QI*UI*UI*UG*AG*AG*AIBLIBLIBLTYCTYCTYCA*OA*OA*OL*ML*ML*M**M**M**M OUT READ IN READ OUT D I G I T A L * * * * B Y * * * Q U A L C O M M D*QD*QD*QI*UI*UI???*AG*AG*AIBLIBLIBLTYCTYCTYCA*OA*OA*????L*ML*M**M**M**M DECODE ERRORS

Scrambling the Signal

Signal Is Scrambled Using the Long Code

Data Scrambling Decimator

The Power Control Sub-Channel

Orthogonal Spreading The Code That Divides

Forward Traffic Channel
Orthogonal Spreading Forward Traffic Channel

Forward CDMA Code Channels
Forward Traffic Channel If Less than 7 Paging Channels Are Used, Each Unused Walsh Code Becomes a Traffic Channel.

Forward Traffic Channel
Quadrature Spreading Forward Traffic Channel

PN Offset — Cell Identification

Forward CDMA Channel I & Q Mapping

Filter Mask

Forward Traffic Channel Parameters Rate Set 1

Forward Traffic Channel Parameters Rate Set 2

A Channel Element set up as a Traffic Channel

Pilot Channel Generation
• Phase Reference Timing Reference Signal Strength

Sync Channel Generation
Provides the Mobile with Timing Information to Enable Synchronization.

Sync Channel Parameters

A Channel Element set up to support both Pilot and Sync Channels

Paging Channel Generation
Used to Notify the Mobile of Incoming Calls and to Send Overhead Information.

Paging Channel Long Code Mask
00000 PCN PILOT_PN 8 9 20 21 23 24 28 29 41 PCN = Paging Channel Number PILOT_PN = PN offset for the Forward CDMA Channel

Paging Channel Parameters

Demodulation of the Forward CDMA Channel

Reverse Traffic Channel

Filtering & Up Conversion

Convolutional Coding

Rate 1/3 Encoding

Rate 1/2 Coding

Interleaving

Written into the interleaver by columns; read out by rows.
Interleaving Written into the interleaver by columns; read out by rows.

Orthogonal Modulation

Data Burst Randomizer

Mobile Burst Mask

Data Burst Randomizing

Gating Off Transmitter reduces average power
Symbol repetition on the Reverse Traffic Channel is done for convenience. The repeated symbols are not actually transmitted. Repeating symbols is simply a convenient way of maintaining the alignment and timing between symbols to allow for “Gating” the transmittter off. This method of turning off the transmitter reduces the average power transmitted from the mobile.

Direct Sequence Spreading

Reverse Traffic Channel Mask

Reverse Channel Separation

Quadrature Spreading 1/2 PN chip delay

Reverse CDMA Channel I&Q Mapping
The use of offset QPSK on the reverse link allows the power amplifier to operate more closely to the 1 dB compression point of the amplifier.

Baseband Filtering

Reverse Traffic Channel Parameters

Access Channel Generation
Respond to Pages Request a Traffic Channel

Access Channel Long Code Mask
ACN BASE_ID PCN PILOT_PN 8 9 24 25 27 28 32 33 41 ACN = Access Channel Number PCN = Paging Channel Number BASE_ID = Base Station Identification PILOT_PN = PN offset for the Forward CDMA Channel

Access Channel Parameters

Demodulation of the Reverse CDMA Channel

Section 5 Review Forward CDMA Channel Generation and Demodulation
Reverse CDMA Channel Generation and Demodulation

Power Control

Forward Link Characteristics

Reverse Link Characteristics The Near-Far Effect
Subscribers Closer to the Cell Have Smaller Path Loss Path Loss Can Vary by 80 dB or more

Power Control Requirements
Required Eb/I0 Ensure the receiver gets enough Eb/I0

Power Control Requirements

The Design Choice Closed Loop Control

Step 1: Open Loop Control

k – Mean Receive Power (dBm) + Access Probe Corrections
Open Loop Equation Transmit Power (dBm) = k – Mean Receive Power (dBm) + Parameters + Access Probe Corrections

Access Probes

in Mean Receive Power (msec)
Open Loop Response Mean Output Power (Normalized to Final Value in dB) Time After Step Change in Mean Receive Power (msec)

Step 2: Fast Closed Loop Base Station Makes a Comparison

Mobile Transmits Bursts

Puncturing the Power Control Bits
User Data Power Control Bit Transmitted Sequence

Pseudorandom Bit Placement

Bit Error Rate vs. Delay

Impact on Apparent Voice Activity

Impact of the “Bursty” Mobile Transmission

Power Control During a Soft Handoff
Increase Power Decrease ? Multiple Commands Can Be Received By The Mobile Mobile Must Resolve The Conflict

Typical Closed Loop Histogram

Reverse Outer Loop Power Control

The Reverse Power Control Response

Max Transmit Power IS-95A Subscriber Units

Max Transmit Power PCS Subscriber Units

Min Transmit Power Subscriber Units
Mobile Transmit & Receive Power -100 -80 -60 -40 -20 20 40 1 2 3 4 5 Time dBm Mobile Receive Mobile Transmit Min TX Power specification

Forward Link Power Control
Cell Transmits Report of Frame Errors

Forward Power Control 9600 bps Transmission Rate

Forward Power Control 14.4 kbps TX Rate

Malfunction Control Malfunction Timer Lock Orders
Closed Loop Power Control

Call Processing

Mobile Station Call Processing States

Message Flow

Initialization State

System Determination

Pilot Channel Processing
Forward Traffic Channel Sync Paging Forward CDMA Channel

Sync Channel Structure

Convolutional encoder not zeroed out after each frame
Sync Channel Frames S O M 31 Information Bits 32 bits / ms 26.67 ms frame period Convolutional encoder not zeroed out after each frame No CRC bits at frame level SOM (Start Of Message)

Sync Channel Timing

Idle State

Paging Channel Structure

Slotted Paging

Paging Slot Determination

Paging Channel Frames 20 ms Frame Period 10 ms Half Frames
Synchronized Capsule Indicator 9600 bps or 4800 bps Convolutional Encoder Not Zeroed Out After Each Frame No CRC Bits At Frame Levelh

Paging Channel Overhead Information
System Parameters Message Extended System Parameters Msg Access Parameters Message Neighbors List Message Extended Neighbors List Msg CDMA Channel List Message Global Service Redirection Msg

System Access State

Access Channel Structure

Access Channel Frames 20 ms Frame Period 4800 bps
Tail Bits Zero Convolutional Encoder No CRC Bits At Frame Level Preamble Comprised of Zero Filled Frames

Access Channel Request and Response Attempts
Access Channel Probing

Access Channel Request and Response Attempts
(continued)

Access Procedure

Access Channel Failure Mechanisms
Power Related Size Related Timing Related BS Related

Mobile Station Traffic Channel Substates

Traffic Channel Frames

Traffic Channel Message Structure

Mobile Station Organization

Traffic Channel Failure Mechanisms
Mobile Ack Failure Mobile Fade Timer Mobile Bad Frames BS Ack Failure BS Bad Frames

Acknowledgement Failure
Mobile Acknowledgement Failure

Mobile Fade Timer

Mobile Bad Frames

Section 8 Registration

Introduction to Registration

Boundaries Systems, Networks, and Zones

Determining Roaming Status
Cellular Service is normally subscribed to from a particular system. Obtaining Service from another system is possible, but additional charges are generally incurred. Users travelling outside their normal Service area are are said to be “Roaming”.

<27,1> ; <27,2> The Mobile’s “Home”
System 27, Network 1 System 27, Network 2 The Mobile maintains a “Home List”. System/Network combinations on this list are considered to be the mobile’s “HOME” serving areas.

Roaming Status

Types of Registrations

Autonomous Registration

Non-Autonomous Registration

Base Station Infers Location/Status

Multiple System Registration

Access Probing Persistence delay is added
at the beginning of a request attempt (such as an autonomous registration). Persistence Delay

Mobile Parameters that impact registrations.
` MOB_TERM_FOR_SID = No MOB_TERM_FOR_NID = No MOB_TERM_HOME = No I don’t want to receive calls here! User Preferences are reflected in Mobile Parameters

The Registration Message
Section Review Name MIN ESN Location Desired Slot Cycle Station Class Mark Billing Information . Database Base Station Systems And Networks Roaming Types Of Registrations Multiple System Registration Registration Parameters SYSTEM PARAMETERS MESSAGE ACCESS PARAMETERS MESSAGE MOB_TERM_FOR_SID MOB_TERM_FOR_NID MOB_TERM_HOME SLOT_CYCLE_INDEX SID/NID LIST The Registration Message

Section 9 Handoffs

Types of CDMA Handoffs

Multi-Cell “Soft” Handoff

Multi-Sector “Softer” Handoff
Can have up to 2 sectors involved (same cell) Voice data is combined at cell and passed as one frame to the Base Station Controller (switch) Mobile receives Forward Link from each cell (Two Walsh codes)

One Channel Element can transmit thru multiple sectors.

Multi-Cell / Multi-Sector Handoff

Soft Handoff Increases Capacity
CDMA Soft Handoff typically begins closer to the previous Base Station which results in less power TX. Hard Handoff typically occurs farther away from the serving Base Station = More power required

Typical Soft Hand-off Percentages
Two-way Hand-off (20% of time) Three-way Hand-off (10% of time) No Hand-off (70% of time)

CDMA to Analog Hard Handoff

Hard Hand-off Between CDMA Systems
Three Types of Hard Hand-offs Disjoint Cells Frequency Differences Frame Offset Differences

Hand-off Between Disjoint Cells
BSC Three Types of Hard Hand-offs Disjoint Cells Frequency Differences Frame Offset Differences

Frequency Differences
CDMA Channels Status 644 777 Loaded to Capacity Available CDMA Channels Status 644 Current Channel Same CDMA Channel not Available in the next cell

Frame Offset Differences can cause Hard Hand-off
1.25 msec frame offset Even Second Mark 20 msec frame Timing in the current serving cell Timing in the new cell

Idle Handoff

The Searching Process

Pilot Sets Active Set Candidate Set Neighbor Set Remaining Set There are four sets of pilots maintained by the Mobile for Handoffs: Active Set Candidate Set Neighbor Set Remaining Set

Searcher Window Sizes Searcher Window Sizes SRCH_WIN_A SRCH_WIN_N SRCH_WIN_R Window Size (PN chips) 4 8 60 1 6 9 80 2 10 100 3 11 130 14 12 160 5 20 13 226 28 320 7 40 15 452 Search Windows reduce the time the Mobile needs to search for pilot signals. Window search size is specified in the System Parameters Message initially and updated in both the System Parameters Message and the Handoff Direction Message. SRCH_WIN_A: Specifies window size for Active Set and Candidate Set SRCH_WIN_N: Specifies window size for Neighbor Set SRCH_WIN_R: Specifies window size for Remaining Set

Handoff Signaling Messages
• Pilot Strength Measurement Message Handoff Direction Message Handoff Completion Message Analog Handoff Direction Message Extended Handoff Direction Message

Parameters That Regulate Handoff Signaling
Ec/Io Cell A Cell B Guard Time (T_TDROP) Add Threshold (T_ADD) Drop Threshold (T_DROP) Soft Handoff Region Mobile Detects new pilot signal with sufficient strength to use for call processing Sends Pilot Strength Measurement Message to Base Station via existing reverse traffic channel Base Station Allocates forward traffic channel associated with reported pilot Sends Handoff Direction Message to Mobile to use new cell/sector Receives Handoff Direction Message and begins decodingHandoff Completion Message on reverse traffic channels Time

T_COMP & PSMM Reporting

Handoff Drop Timer Expiration Values

Transitioning Between Pilot Sets

Moving Pilots from the Active Set
Origin Set Destination Set Event Active Candidate HDM not including the pilot is received and the associated timer (T_TDROP) has not expired Active Neighbor HDM not including the pilot is received and the associated timer (T_TDROP) has expired Active Remaining Not used. Active pilots do not move directly to the Remaining set

Moving Pilots from the Candidate Set
Origin Set Destination Set Event Candidate Active HDM including the pilots received Candidate Neighbor Timer (T_TDROP) has expired or Candidate Set overflow occurred. Candidate Remaining Not used.

Moving Pilots from the Neighbor Set
Origin Set Destination Set Event Neighbor Active HDM the pilot is received Neighbor Candidate Pilot strength exceeds (T_ADD) Neighbor Remaining Age counter exceeds NGHBR_MAX_AGE or Neighbor Set overflow occurred.

Moving Pilots from the Remaining Set
Origin Set Destination Set Event Remaining Active HDM the pilot is received Remaining Candidate Pilot strength exceeds T_ADD. Remaining Neighbor Neighbor List Update Message including the pilot is received.

Call Processing During Handoff (From Cell A to Cell B)

CdmaOne (IS-95A/B) 1.

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