cdma basics_2.pdf

April, 2001 Course 134v2.0 (c) 2001 Scott Baxter

Course 134

Current CDMA NetworksArchitectures, Algorithms, & Performance

Current CDMA NetworksArchitectures, Algorithms, & Performance


Section A

CDMA Principles ReviewCDMA Principles Review


CDMA: Using A New Dimension

■ All CDMA users occupy the same frequency at the same time! Frequency and time are not used as discriminators

■ CDMA operates by using CODING to discriminate between users

■ CDMA interference comes mainly from nearby users

■ Each user is a small voice in a roaring crowd -- but with a uniquely recoverable code

CDMA

Figure of Merit: C/I(carrier/interference ratio)

AMPS: +17 dBTDMA: +14 to +17 dB

GSM: +7 to 9 dB.CDMA: -10 to -17 dB.CDMA: Eb/No ~+6 dB.


DSSS Spreading: Time-Domain View

At Originating Site:■ Input A: User’s Data @

19,200 bits/second■ Input B: Walsh Code #23

@ 1.2288 Mcps■ Output: Spread

spectrum signal

At Destination Site:■ Input A: Received

spread spectrum signal■ Input B: Walsh Code #23

@ 1.2288 Mcps■ Output: User’s Data @

19,200 bits/second just as originally sent

Drawn to actual scale and time alignment

via air interface

XORExclusive-OR

Gate

1

1

Input A: Received Signal

Input B: Spreading Code

Output: User’s Original Data

Input A: User’s Data

Input B: Spreading Code

Spread Spectrum Signal

XORExclusive-OR

Gate

Originating Site

Destination Site


Spreading from a Frequency-Domain View

■ Traditional technologies try to squeeze signal into minimum required bandwidth

■ CDMA uses larger bandwidth but uses resulting processing gain to increase capacity

Spread Spectrum Payoff:Processing Gain

Spread SpectrumTRADITIONAL COMMUNICATIONS SYSTEM

SlowInformation

SentTX

SlowInformationRecovered

RX

NarrowbandSignal

SPREAD-SPECTRUM SYSTEM

FastSpreadingSequence

SlowInformation

SentTX

SlowInformationRecovered

RX

FastSpreadingSequence

WidebandSignal


CDMA Uses Code Channels

■ The purpose of a CDMA system is to transmit bits from one user to another

• Vocoder bits are the “payload” in voice calls• Fax or Web TCP/IP data bits are also possible

■ A CDMA signal uses many chips to convey just one bit of information

■ Each user has a unique chip pattern, in effect a channel made from codes

■ To recover a bit, integrate a large number of chips interpreted by the user’s known code pattern

■ Other users’ code patterns appear random and add up in a random self-canceling fashion; they don’t disturb the bit decoding decision being made regarding information transmitted on the proper code pattern

Building aBuilding aCDMA SignalCDMA Signal

Bitsfrom User’s Vocoder

Symbols

Chips

Forward Error Correction

Coding and Spreading


“Sneak Preview”: How One Traffic ChannelIs Transmitted by One Sector to a Mobile

Σ Σ Σ Σ

if 1 =if 0 =

1

AnalogSummingUsers

QPSK RF

ΣΣΣΣ

DemodulatedReceived

CDMA SignalDespreading Sequence(Locally Generated, =0)

matchesopposite

Decision:

Matches!( = 0 )

TimeIntegration

1

Opposite( =1)

+10

-26

Received energy: Correlation

-16

BTS

This figure illustrates the basic technique of CDMA signalgeneration at the sector and recovery at the mobile.The complete coding process uses two additional codes, as described in following slides.


Spreading: What we do, we can undo

■ Sender combines data with a fast spreading sequence, transmits spread data stream

■ Receiver intercepts the stream, uses same spreading sequence to extract original data

ORIGINATING SITE DESTINATION

SpreadingSequence

SpreadingSequence

InputData

RecoveredData

Spread Data Stream


“Shipping and Receiving” via CDMA

■ Whether in shipping and receiving, or in CDMA, packaging is extremely important!

■ Cargo is placed inside “nested” containers for protection and toallow addressing

■ The shipper packs in a certain order, and the receiver unpacks in the reverse order

■ CDMA “containers” are spreading codes

FedE

x

Data Mailer

FedE

x

DataMailer

Shipping Receiving


CDMA’s Nested Spreading Sequences

■ CDMA combines three different spreading sequences to create unique, robust channels

■ The sequences are easy to generate on both sending and receiving ends of each link

■ “What we do, we can undo”

SpreadingSequence

ASpreadingSequence

BSpreadingSequence

CSpreadingSequence

CSpreadingSequence

BSpreadingSequence

A

InputDataX

RecoveredDataX

X+A X+A+B X+A+B+C X+A+B X+ASpread-Spectrum Chip Streams

ORIGINATING SITE DESTINATION


One of the CDMA Spreading Sequences:Walsh Codes

■ 64 “Magic” Sequences, each 64 chips long■ Each Walsh Code is precisely Orthogonal with

respect to all other Walsh Codes• it’s simple to generate the codes, or• they’re small enough to use from ROM

WALSH CODES# ---------------------------------- 64-Chip Sequence ------------------------------------------0 00000000000000000000000000000000000000000000000000000000000000001 01010101010101010101010101010101010101010101010101010101010101012 00110011001100110011001100110011001100110011001100110011001100113 01100110011001100110011001100110011001100110011001100110011001104 00001111000011110000111100001111000011110000111100001111000011115 01011010010110100101101001011010010110100101101001011010010110106 00111100001111000011110000111100001111000011110000111100001111007 01101001011010010110100101101001011010010110100101101001011010018 00000000111111110000000011111111000000001111111100000000111111119 0101010110101010010101011010101001010101101010100101010110101010

10 001100111100110000110011110011000011001111001100001100111100110011 011001101001100101100110100110010110011010011001011001101001100112 000011111111000000001111111100000000111111110000000011111111000013 010110101010010101011010101001010101101010100101010110101010010114 001111001100001100111100110000110011110011000011001111001100001115 011010011001011001101001100101100110100110010110011010011001011016 000000000000000011111111111111110000000000000000111111111111111117 010101010101010110101010101010100101010101010101101010101010101018 001100110011001111001100110011000011001100110011110011001100110019 011001100110011010011001100110010110011001100110100110011001100120 000011110000111111110000111100000000111100001111111100001111000021 010110100101101010100101101001010101101001011010101001011010010122 001111000011110011000011110000110011110000111100110000111100001123 011010010110100110010110100101100110100101101001100101101001011024 000000001111111111111111000000000000000011111111111111110000000025 010101011010101010101010010101010101010110101010101010100101010126 001100111100110011001100001100110011001111001100110011000011001127 011001101001100110011001011001100110011010011001100110010110011028 000011111111000011110000000011110000111111110000111100000000111129 010110101010010110100101010110100101101010100101101001010101101030 001111001100001111000011001111000011110011000011110000110011110031 011010011001011010010110011010010110100110010110100101100110100132 000000000000000000000000000000001111111111111111111111111111111133 010101010101010101010101010101011010101010101010101010101010101034 001100110011001100110011001100111100110011001100110011001100110035 011001100110011001100110011001101001100110011001100110011001100136 000011110000111100001111000011111111000011110000111100001111000037 010110100101101001011010010110101010010110100101101001011010010138 001111000011110000111100001111001100001111000011110000111100001139 011010010110100101101001011010011001011010010110100101101001011040 000000001111111100000000111111111111111100000000111111110000000041 010101011010101001010101101010101010101001010101101010100101010142 001100111100110000110011110011001100110000110011110011000011001143 011001101001100101100110100110011001100101100110100110010110011044 000011111111000000001111111100001111000000001111111100000000111145 010110101010010101011010101001011010010101011010101001010101101046 001111001100001100111100110000111100001100111100110000110011110047 011010011001011001101001100101101001011001101001100101100110100148 000000000000000011111111111111111111111111111111000000000000000049 010101010101010110101010101010101010101010101010010101010101010150 001100110011001111001100110011001100110011001100001100110011001151 011001100110011010011001100110011001100110011001011001100110011052 000011110000111111110000111100001111000011110000000011110000111153 010110100101101010100101101001011010010110100101010110100101101054 001111000011110011000011110000111100001111000011001111000011110055 011010010110100110010110100101101001011010010110011010010110100156 000000001111111111111111000000001111111100000000000000001111111157 010101011010101010101010010101011010101001010101010101011010101058 001100111100110011001100001100111100110000110011001100111100110059 011001101001100110011001011001101001100101100110011001101001100160 000011111111000011110000000011111111000000001111000011111111000061 010110101010010110100101010110101010010101011010010110101010010162 001111001100001111000011001111001100001100111100001111001100001163 0110100110010110100101100110100110010110011010010110100110010110

EXAMPLE:Correlation of Walsh Code #23 with Walsh Code #59

#23 0110100101101001100101101001011001101001011010011001011010010110#59 0110011010011001100110010110011010011001011001100110011010011001Sum 0000111111110000000011111111000011110000000011111111000000001111

Correlation Results: 32 1’s, 32 0’s: Orthogonal!!

Unique Properties:Mutual Orthogonality


Other Sequences: Generation & Properties

■ Other CDMA sequences are generated in shift registers

■ Plain shift register: no fun, sequence = length of register

■ Tapped shift register generates a wild, self-mutating sequence 2N-1 chips long (N=register length)

• Such sequences match if compared in step (no-brainer, any sequence matches itself)

• Such sequences appear approximately orthogonal if compared with themselves not exactly matched in time

• false correlation typically <2%

A Tapped, Summing Shift Register

Sequence repeats every 2N-1 chips,where N is number of cells in register

An Ordinary Shift Register

Sequence repeats every N chips,where N is number of cells in register

A Special Characteristic of SequencesGenerated in Tapped Shift Registers

Compared In-Step: Matches Itself

Complete Correlation: All 0’sSum:Self, in sync:

Sequence:

Compared Shifted: Little Correlation

Practically Orthogonal: Half 1’s, Half 0’sSum:Self, Shifted:

Sequence:


Another CDMA Spreading Sequence:The Short PN Code

■ The short PN code consists of two PN Sequences, I and Q, each 32,768 chips long

• Generated in similar but differently-tapped 15-bit shift registers

• They’re always used together, modulating the two phase axes of a QPSK modulator

IQ

32,768 chips long26-2/3 ms.

(75 repetitions in 2 sec.)CDMA QPSK Phase ModulatorUsing I and Q PN Sequences

I-sequence

Q-sequence

ΣΣΣΣ

cos ωt

sin ωωωωt

chipinput

QPSK-modulated

RFOutput

*

* In BTS, I and Q are used in-phase.In handset, Q is delayed 1/2 chip toavoid zero-amplitude crossings whichwould require a linear power amplifier


Third CDMA Spreading Sequence: Long Code Generation & Masking to establish Offset

■ Generated in a 42-bit register, the PN Long code is more than 40 days long (~4x1013 chips) -- too big to store in ROM in a handset, so it’s generated chip-by-chip using the scheme shown above

■ Each handset codes its signal with the PN Long Code, but at a unique offset computed using its ESN (32 bits) and 10 bits set by the system

• this is called the “Public Long Code Mask”; produces unique shift• private long code masks are available for enhanced privacy

■ Integrated over a period even as short as 64 chips, phones with different PN long code offsets will appear practically orthogonal

Long Code Register (@ 1.2288 MCPS)

Public Long Code Mask(STATIC)

User Long CodeSequence

(@1.2288 MCPS)

1 1 0 0 0 1 1 0 0 0 PERMUTED ESNAND=

SUM

Modulo-2 Addition


Putting it All Together: CDMA Channels

■ The three spreading codes are used in different ways to create the forward and reverse links

■ A forward channel exists by having a specific Walsh Code assigned to the user, and a specific PN offset for the sector

■ A reverse channel exists because the mobile uses a specific offset of the Long PN sequence

BTS

WALSH CODE: Individual UserSHORT PN OFFSET: Sector

LONG CODE OFFSET: individual handset

FORWARD CHANNELS

REVERSE CHANNELS

LONG CODE:Data

Scrambling

WALSH CODES:used as symbols

for robustness

SHORT PN:used at 0 offset

for tracking

OneSector


Section B

IS-95 CDMA Forward and Reverse Channels

IS-95 CDMA Forward and Reverse Channels


How a BTS Builds the Forward Code Channels

BSC orAccess Manager

BTS (1 sector)

FECWalsh #1

Sync FECWalsh #32

FECWalsh #0

FECWalsh #12

FECWalsh #27

FECWalsh #44

Pilot

Paging

Vocoder

Vocoder

Vocoder

Vocoder

more more

Short PN CodePN Offset 246

Trans-mitter,

Sector X

Switch

more

a Channel Element

A Forward Channel is identified by:

❖ its CDMA RF carrier Frequency

❖ the unique Short Code PN Offset of the sector

❖ the unique Walsh Code of the user

FECWalsh #23

ΣΣΣΣQ

ΣΣΣΣI

x

x+

cos ωωωωt

sin ωωωωt

I Q


Functions of the CDMA Forward Channels

■ PILOT: WALSH CODE 0• The Pilot is a “structural beacon” which

does not contain a character stream. It is a timing source used in system acquisition and as a measurement device during handoffs

■ SYNC: WALSH CODE 32• This carries a data stream of system

identification and parameter information used by mobiles during system acquisition

■ PAGING: WALSH CODES 1 up to 7• There can be from one to seven paging

channels as determined by capacity needs. They carry pages, system parameters information, and call setup orders

■ TRAFFIC: any remaining WALSH codes• The traffic channels are assigned to

individual users to carry call traffic. All remaining Walsh codes are available, subject to overall capacity limited by noise

Pilot Walsh 0

Walsh 19

Paging Walsh 1Walsh 6

Walsh 11

Walsh 20Sync Walsh 32

Walsh 42

Walsh 37Walsh 41

Walsh 56Walsh 60

Walsh 55


Code Channels in the Reverse DirectionBSC, CBSC,Access

Manager

Switch BTS (1 sector)

Channel Element

Access Channels

Vocoder

Vocoder

Vocoder

Vocoder

more more

Receiver,Sector X

A Reverse Channel is identified by:❖ its CDMA RF carrier Frequency❖ the unique Long Code PN Offset

of the individual handset

Channel Element

Channel Element

Channel Element

Long Code Gen

Long Code Gen

Long Code Gen

Long Code Gen

more

a Channel Element

LongCodeoffset Long

Codeoffset Long

Codeoffset

LongCodeoffset

LongCodeoffset

LongCodeoffset

Channel Element

Long Code Gen


REG

1-800242

4444

BTS

Although a sector can have up to seven paging channels, and each paging channel can have up to 32 access channels, nearly all systems today use only one paging

channel per sector and only one access channel per paging channel.

Functions of the CDMA Reverse ChannelsThere are two types of CDMA Reverse Channels:

■ TRAFFIC CHANNELS are used by individual users during their actual calls to transmit traffic to the BTS

• a reverse traffic channel is really just a user-specific public or private Long Code mask

• there are as many reverse Traffic Channels as there are CDMA phones in the world!

■ ACCESS CHANNELS are used by mobiles not yet in a call to transmit registration requests, call setup requests, page responses, order responses, and other signaling information

• an access channel is really just a public long code offset unique to the BTS sector

• Access channels are paired to Paging Channels. Each paging channel can have up to 32 access channels.


Basic CDMA Network Architecture

Access Manageror (C)BSC

Switch BTS

Ch. Card ACC

Σα

Σβ

Σχ

TFU1

GPSRBSM

CDSU

CDSU

SBSVocodersSelectors

CDSU

CDSU

CDSU

CDSU

CDSU

CMSLM

LPP LPPENET

DTCs

DMS-BUS

TxcvrA

TxcvrB

TxcvrC

RFFEA

RFFEB

RFFEC

TFU

GPSR

GPS GPS

IOC

PSTN

CDSU DISCOCDSU

DISCO 1

DISCO 2

DS0 in T1Packets

ChipsRFChannel

ElementVocoder


Forward Traffic Channel: Generation Details from IS-95

Walshfunction

PowerControl

Bit

I PN

9600 bps4800 bps2400 bps1200 bps

or14400 bps7200 bps3600 bps1800 bps

(From Vocoder)

ConvolutionalEncoding and

Repetition SymbolPuncturing(13 kb only)

1.2288McpsLong PN Code

Generation

19.2ksps

800 Hz

R = 1/2

Q PNDecimator Decimator

User AddressMask

(ESN-based)

19.2ksps

1.2288Mcps

Scrambling

bits symbols chips

19.2ksps

28.8ksps

CHANNEL ELEMENT

MUX

BlockInterleaving


Reverse Traffic Channel: Generation Details from IS-95

9600 bps4800 bps2400 bps1200 bps

or 14400 bps7200 bps3600 bps1800 bps

28.8ksps

R = 1/3

1.2288McpsUser Address

MaskLong

PN CodeGenerator

28.8ksps Orthogonal

ModulationData Burst

Randomizer

307.2kcps

1.2288Mcps

Q PN(no offset)

I PN(no offset)

D

1/2 PNChipDelay

DirectSequenceSpreading

R = 1/2

ConvolutionalEncoder &Repetition

BlockInterleaver


Section C

IS-95 Operational DetailsVocoding, Multiplexing, Power Control

IS-95 Operational DetailsVocoding, Multiplexing, Power Control


Variable Rate Vocoding & Multiplexing

■ Vocoders compress speech, reduce bit rate, greatly increasing capacity

■ CDMA uses a superior Variable RateVocoder

• full rate during speech• low rates in speech pauses• increased capacity• more natural sound

■ Voice, signaling, and user secondary data may be mixed in CDMA frames

DSP QCELP VOCODER

Codebook

PitchFilter

FormantFilter

Coded Result Feed-back

20ms Sample

Frame SizesbitsFull Rate Frame

1/2 Rate Frame1/4 Rt.1/836

72144288

Frame Contents: can be a mixture ofPrimaryTraffic(Voice or

data)

Signaling(System

Messaging)

Secondary(On-Air

activation, etc)


Forward Power Control

■ The BTS continually reduces the strength of each user’s forwardbaseband chip stream

■ When a particular handset sees errors on the forward link, it requests more energy

■ The complainer’s chip stream gets a quick boost; afterward, continues to diminish

■ Each network manufacturer uses FER-based triggers and initial, minimum, and maximum traffic channel DGU values

ForwardRF

BSC BTS (1 sector)

SyncPilot

Paging

more

Short PN

Trans-mitter,

Sector XΣΣΣΣ I QUser 1

User 2User 3Vocoder/

Selector

Help!


Reverse Power Control

■ Three methods work in tandem to equalize all handset signal levels at the BTS

• Reverse Open Loop: handset adjusts power up or down based on received BTS signal (AGC)

• Reverse Closed Loop: Is handset too strong? BTS tells up or down 1 dB 800 times/second

• Reverse Outer Loop: BSC has FER trouble hearing handset? BSC adjusts BTS setpoint

RX RF

TX RF Digital

BTSBSC

SetpointBad FER?

Raise Setpoint

Stronger thansetpoint?

ReverseRF

800 bits per second

Occasionally,as needed Handset

OpenLoop

ClosedLoop

Digital


Details of Reverse Link Power Control

■ TXPO Handset Transmit Power• Actual RF power output of the

handset transmitter, including combined effects of open loop power control from receiver AGC and closed loop power control by BTS

• can’t exceed handset’s maximum (typ. +23 dBm)

■ TXGA Transmit Gain Adjust• Sum of all closed-loop power

control commands from the BTS since the beginning of this call

TXPODUP x ≈≈≈≈ IF

LNA

Subscriber Handset

R

R

R

S

Rake

ΣΣΣΣ ViterbiDecoder

Vocoder

∼∼∼∼

FECOrthMod

Long PN

xx

xIF Mod

I

Q

x ~LO Open Loop

LO

Closed Loop Pwr Ctrl

IF

Receiver>>

<<Transmitter

PA

BTS

Typical TXPO:+23 dBm in a coverage hole0 dBm near middle of cell-50 dBm up close to BTS

0 dB

-10 dB

-20 dB

Typical Transmit Gain Adjust

Time, Seconds

TXPO = -(RXdbm) -C + TXGAC = +73 for 800 MHz. systems= +76 for 1900 MHz. systems


Course 134

CDMA Air Interface CapacityCDMA Air Interface Capacity


The Basic CDMA Capacity Equation

■ As this spreadsheet shows, actual traffic capacity is influencedstrongly by the degree of soft handoff actually in progress

Basic Capacity of a CDMA CellCase A Case B

Vocoder or Data Rate, kb/s 9.6 14.4 (9.6 for Rate Set 1, 14.4 for Rate Set 2)Bandwidth, MHz. 1.25 1.25 (IS-95/J-Std 008 is 1.25 MHz.)

Eb/No in dB 7 7 5.01 Eb/No as ratioVoice Duty factor 0.40 0.40 100% when talking, 12.5% when listening

Freq Reuse Efficiency 0.60 0.60 fraction of energy coming from within same cellSectorization Gain 2.55 2.55 (2.55 observed for 3-sector cells in tests)

Gross Number of Users/Cell 99.4 66.2Percentage of Users in Soft Handoff 50% 50%

Net Unique Users Per Cell 66.2 44.2


Capacity Issues with Current CDMA Networks

■ Today, CDMA networks for the most part are still single-carrier• this severely limits the capacity of one BTS to approximately 20

erlangs• implementing additional carriers brings logistical problems

involving handoffs and system acquisition by mobiles■ Multiple-carrier operation is essential to achieve reasonable

capacities■ Within networks, there are strategies for squeezing the most out of

overloaded single-carrier BTSs. Some of the main points are:• reduce Pilot, Sync, and Paging levels as low as possible,

thereby gaining precious additional energy for traffic channels• reduce BTS traffic channel DGU settings as low as possible

without provoking forward link FER.


Wireless System Capacity ComparisonsEach wireless technology (AMPS,

NAMPS, D-AMPS, GSM, CDMA) uses a specific modulation type with its own unique signal characteristics

■ Signal Bandwidth determines how many RF signals will “fit” in the operator’s licensed spectrum

■ Robustness of RF signal determines tolerable level of interference and necessary physical separation of cochannelcells

■ Number of users per RF signal directly affects capacity

■ In the following page, we will develop the number of users and traffic in erlangs per site for each of the popular wireless technologies

AMPS, D-AMPS, N-AMPS

CDMA

30 30 10 kHz Bandwidth

200 kHz

1250 kHz

1 3 1 Users

8 Users

22 Users1

1

11

11

11

111

111

1 23

4

432

56 17

Typical Frequency Reuse N=7



Vulnerability:C/I ≅ ≅ ≅ ≅ 17 dB

Vulnerability:C/I ≅ 6.5-9 dB

Vulnerability:EbNo ≅ 6 dB


Comparison of Wireless System Capacities

Fwd/Rev Spectrum kHz. 12,500 12,500 12,500 15,000 15,000 15,000 5,000 5,000 5,000 Technology AMPS TDMA CDMA TDMA GSM CDMA TDMA GSM CDMAReq'd C/I or Eb/No, db 17 17 6 17 12 6 17 12 6Freq Reuse Factor, N 7 7 1 7 4 1 7 4 1RF Signal BW, kHz 30 30 1250 30 200 1250 30 200 1250Total # RF Carriers 416 416 9 500 75 11 166 25 3RF Sigs. per cell @N 59 59 9 71 18 11 23 6 3# Sectors per cell 3 3 3 3 3 3 3 3 3#CCH per sector 1 1 0 1 0 0 1 0 0RF Signals per sector 18 18 9 22 6 11 6 2 3Voicepaths/RF signal 1 3 22 3 8 22 3 8 22SH average links used 1.66 1.66 1.66Unique Voicepaths/carrier 13.253 13.253 13.253Voicepaths/Sector 18 54 198 66 48 242 18 16 66Unique Voicepaths/Sector 18 54 119 66 48 145 18 16 39P.02 Erlangs per sector 11.5 44 105.5 55.3 38.4 130.9 11.5 9.83 30.1P.02 Erlangs per site 34.5 132 316.5 165.9 115.2 392.7 34.5 29.49 90.3Capacity vs. AMPS800 1 3.8 9.2 4.8 3.3 11.4 1.0 0.9 2.6

800 Cellular (A,B) 1900 PCS (A, B, C) 1900 PCS (D, E, F)

824 835 845 870 880894

869

849

846.5825

890

891.5

Paging, ESMR, etc.A B A B

A D B E F C unlic.data

unlic.voice A D B E F C

1850 MHz.

1910 MHz.

1990 MHz.

1930 MHz.

15 15 155 5 5 15 15 155 5 5


Multicarrier CDMA Capacity Implications

Fwd/Rev Spectrum kHz. 12,500 1,800 3,050 4,300 5,550 6,800 8,050 9,300 10,550 11,800 13,050 14,300 Technology AMPS CDMA CDMA CDMA CDMA CDMA CDMA CDMA CDMA CDMA CDMA CDMA

Req'd C/I or Eb/No, db 17 6 6 6 6 6 6 6 6 6 6 6Freq Reuse Factor, N 7 1 1 1 1 1 1 1 1 1 1 1

RF Signal BW, kHz 30 1250 1250 1250 1250 1250 1250 1250 1250 1250 1250 1250Total # RF Carriers 416 1 2 3 4 5 6 7 8 9 10 11

RF Sigs. per cell @N 59 1 2 3 4 5 6 7 8 9 10 11# Sectors per cell 3 3 3 3 3 3 3 3 3 3 3 3#CCH per sector 1 0 0 0 0 0 0 0 0 0 0 0

RF Signals per sector 18 1 2 3 4 5 6 7 8 9 10 11Voicepaths/RF signal 1 22 22 22 22 22 22 22 22 22 22 22

SH average links used 1 1.66 1.66 1.66 1.66 1.66 1.66 1.66 1.66 1.66 1.66 1.66Unique Voicepaths/carrier 1 13.3 13.3 13.3 13.3 13.3 13.3 13.3 13.3 13.3 13.3 13.3

Voicepaths/Sector 18 22 44 66 88 110 132 154 176 198 220 242Unique Voicepaths/Sector 18 13 26 39 53 66 79 92 106 119 132 145

P.02 Erlangs per sector 11.5 7.4 18.4 30.1 43.1 55.3 67.7 80.2 93.8 105.5 119.1 130.9P.02 Erlangs per site 34.5 22.2 55.2 90.3 129.3 165.9 203.1 240.6 281.4 316.5 357.3 392.7

Capacity vs. AMPS800 1 0.64 1.60 2.6 3.7 4.8 5.9 7.0 8.2 9.2 10.4 11.4

f

1 2 3 4 5 6 7 8 9 1011

CDMA Carrier Frequencies


Course 134

CDMA Network ArchitectureCDMA Network Architecture


BASE STATIONCONTROLLER

SUPPORTFUNCTIONS

BASE STATIONS

Mobile TelephoneSwitching Office

PSTNLocal CarriersLong Distance

CarriersATM Link

to other CDMANetworks(Future)

Structure of a Typical Wireless System

Voice Mail System SWITCH

HLR Home Location Register(subscriber database)


Signal Flow: Two-Stage Metamorphosis

BSC-BSMMTX BTS

Ch. Card ACC

Σα

Σβ

Σχ

TFU1

GPSRBSM

CDSU

CDSU


CDSU

CDSU

CDSU

CDSU

CDSU

CMSLM

LPP LPPENET

DTCs

DMS-BUS

TxcvrA

TxcvrB

TxcvrC

RFFEA

RFFEB

RFFEC

TFU

GPSR

GPS GPS

IOC

PSTN

CDSU DISCOCDSU

DISCO 1

DISCO 2

DS0 in T1Packets

ChipsRFChannel

ElementVocoder


Course 134

Nortel CDMA Network Architecture

Nortel CDMA Network Architecture

www.nortel.com


NORTEL CDMA System Architecture

BSC-BSMMTX BTS

CDSU DISCO

Ch. Card ACC

ΣΣΣΣα

ΣΣΣΣβ

ΣΣΣΣχ

TFU1

GPSRBSM

CDSU

CDSU

DISCO 1

DISCO 2


CDSU

CDSU

CDSU

CDSU

CDSU

CDSU

CMSLM

LPP LPPENET

DTCs

DMS-BUS

TxcvrA

TxcvrB

TxcvrC

RFFEA

RFFEB

RFFEC

TFU

GPSR

PSTN & Other MTXs

GPS GPS

IOC

Billing •Current Product Capabilities:•Each BSC can have up to 4 DISCO shelves

•About 240 sites, roughly 6000 erlangs capacity•Each MTX can have up to 2 BSCs


Switch: The Nortel MTX

■ Primary functions• Call Processing• Mobility Management

– HLR-VLR access– Intersystem call delivery (IS-41C)– Inter-MTX handover (IS-41C)

• Billing Data Capture• Calling Features & Services• Collecting System OMs, Pegs

■ High reliability, redundancy

MTX

CMSLM

LPP ENET

DTCs

DMS-BUS

PSTN & Other MTXs

CDMABSC

Unch. T1

IOC

CDMASBS

MAP,VDUs

Billing

LPP

CCS7

Ch.T1

ChT1


The Nortel BSC

■ Primary functions• vocoding• soft handoff management• FER-based power control• routing of all traffic and control

packets■ Scaleable architecture

• expand SBS to keep pace with traffic growth

• expandable DISCO

BSC

TFU1

GPSRBSM

CDSUCDSU

DISCO 1

DISCO 2


CDSU

CDSU

CDSU

CDSU

CDSU

CDSU

GPS

MTX(voicetrunks)

MTXLPP

BTSs

T1 channelized (24 DS0)T1 unchannelizedBCN link (HDLC)


The Nortel BTS

■ Base Transceiver Station■ Primary function: Air link

• generate, radiate, receive CDMA RF signal IS-95/J.Std. 8

• high-efficiency T1 backhaul• test capabilities

■ Configurations• 1, 2, or 3 sectors• 800 MHz.: indoor• 1900 MHz.: self-contained outdoor,

remotable RFFEs• new indoor, 800 MHz. & 1900 MHz.

multi-carrier options• Metrocell

BTS

CDSU DISCO

Ch. Card ACC

ΣΣΣΣα

ΣΣΣΣβ

ΣΣΣΣχ

TxcvrA

TxcvrB

TxcvrC

RFFEA

RFFEB

RFFEC

TFU

GPSRGPS

BSC


The Nortel BSM

■ Base Station Manager■ Primary functions: OA&M for CDMA

components• Configuration management

– BSC, BTS configuration and parameters

• Fault management– Alarm Reporting

• Performance management– interface for CDMA statistics

and peg counts collection• Security management• Unix-based

BSC BTS

CDSU DISCO

Ch. Card ACC

ΣΣΣΣα

ΣΣΣΣβ

ΣΣΣΣχ

TFU1

GPSR

CDSU

CDSU

DISCO 1

DISCO 2


CDSU

CDSU

CDSU

CDSU

CDSU

CDSU

TxcvrA

TxcvrB

TxcvrC

RFFEA

RFFEB

RFFEC

TFU

GPSR

GPS GPS

BSM

X-Windows terminals

Ethernet LAN

BSM Workstation

GNP TELCOWORKSERVER

SHELF---------HIGH

AVAILABILITY

NORTEL CDMA BSM

BCN Links


Nortel Operational Capacity Considerations

BSC-BSMMTX BTS

Ch. Card ACC

Σα

Σβ

Σχ

TFU1

GPSRBSM

CDSU

CDSU


CDSU

CDSU

CDSU

CDSU

CDSU

CMSLM

LPP LPPENET

DTCs

DMS-BUS

TxcvrA

TxcvrB

TxcvrC

RFFEA

RFFEB

RFFEC

TFU

GPSR

GPSGPS

IOC

PSTN

CDSU DISCOCDSU

DISCO 1

DISCO 2

Sufficient vocoders/selectors required in BSC SBS, one per

simultaneous call on the system. 8 Vocoders per SBS card, 12 cards per shelf, 4 shelves per

SBS cabinet.

One T-1 can carry all traffic originated by a

one-carrier BTS; special consideration required if

daisy-chaining

Forward RF Capacity: links use available

BTS TX power

Sufficient channel elements required for traffic of all sectors: one CE per link; 20

CE per Channel Card

64 Walsh Codes/sector



DISCO has 192 ports max. Each

BTS uses 1, SBS shelf 1, LPP CIU 1,

Link 2, Ctrl. 2, BSM 4.

Typical CM processorcapacity considerations

PSTN trunk groups must be dimensioned to

support erlang load.

DTC & ENET: One port perVocoder plus one port per

outgoing trunk.

CDMA LPP: One pairCIUs and One pairCAUs per

approx. 600 erlangs

Reverse RF Capacity: links cause noise floor rise, use mobile power

•1-2001 Current Product Capabilities:•Each BSC can have up to 4 DISCO shelves

•About 240 sites, roughly 6000 erlangs capacity•Each MTX can have up to 2 BSCs


Course 134

Lucent CDMA Network Architecture

Lucent CDMA Network Architecture

www.lucent.com


Lucent CDMA System Architecture

Access ManagerECP BTS

ChannelUnit

Cluster

ACU

ΣΣΣΣα

ΣΣΣΣβ

ΣΣΣΣχ

Baseband Combiner & Radio



PSTN & Other MTXs

ExecutiveCellular

Processor Complex (ECPC)

Circuit SwitchPlatform

CDMA SpeechHandling Equipment

Packet SwitchPlatform

CDMA MSC (NO BSC)

ATM

Three Sizes of CDMA MSC:•#5ESS-2000 large markets•Compact Digital Exchange (CDX) medium market•Very Compact Digital Exchange (VCDX) small mkts.

Two Access Manager sizes•Large: 16 MSCs, 200K BHCA, 222 BTSs, 500K HLR/VLR entries•Small: 32 BTSs, ~30K subs


The Lucent ECP

■ Executive Cellular Processor■ Primary functions

• Call Processing• Mobility Management

– HLR-VLR access– Intersystem call delivery (IS-41C)– Inter-MTX handover (IS-41C)

• Billing Data Capture• Calling Features & Services• Collecting System OMs, Pegs

■ High reliability, redundancy

ECP

ExecutiveCellular

Processor Complex (ECPC)


The Lucent #5ESS and Access Manager

■ Primary functions• vocoding• soft handoff management• FER-based power control• routing of all traffic and control

packets■ Scaleable architecture

• expand speech handlers• expandable packet switch

5ESS-2000 DCS

PSTN & Other MTXs

Circuit SwitchPlatform

CDMA SpeechHandling Equipment

Packet SwitchPlatform


The Lucent BTS

■ Primary function: Air link • generate, radiate, receive

CDMA RF signal IS-95/J.Std. 8• high-efficiency T1 backhaul• test capabilities

BTSChannel

UnitCluster

ACU

ΣΣΣΣα

ΣΣΣΣβ

ΣΣΣΣχ





Course 134

Motorola CDMA Network Architecture

Motorola CDMA Network Architecture

www.motorola.com


Motorola CDMA System ArchitectureOMC-R

CBSC

PCSCPersonal

CommunicationsSwitching

Center

PSTNDSC

EMX-2500or

EMX-5000

Mobility Manager

Transcoder

OMC-RProcessor

ApplicationProcessor

(or SC-UNO)

BTS (SC9600/4800/2400)

Group LineInterface (GLI)

MultichannelCDMA Card (MCC)

BTS (SC614T/611)

MotorolaAdvancedWidebandInterface(MAWI)

PCLocal

MaintenanceFacility


The Motorola PCSC

■ Personal Communications Switching Center■ Primary functions

• Call Processing• HLR-VLR access• Intersystem call delivery (IS-41C)• Billing Data Capture• Calling Features & Services

PSTNDSC

EMX-2500or

EMX-5000

EMX-2500

EMX-5000


The Motorola CBSC

■ Centralized Base Station Controller■ Mobility Manager

• allocation of BTS resources• handoff management• Call management & supervision

■ Transcoder• vocoding• soft handoff management• FER-based power control• routing of all traffic and control

packets

CBSC

Mobility Manager

Transcoder


The Motorola BTS Family■ Primary function: Air link

• generate, radiate, receive CDMA RF signal IS-95/J.Std. 8

• high-efficiency T1 backhaul

• test capabilities

BTS (SC9600/4800/2400)

Group LineInterface (GLI)

MultichannelCDMA Card (MCC)

BTS (SC614T/611)

MotorolaAdvancedWidebandInterface(MAWI)

PCLocal

MaintenanceFacility

SC611 Microcell

SC4852SC614T


Course 134

Samsung CDMA Network Architecture


www.samsungelectronics.com


Samsung Switching Architecture

■ Samsung offers both a large switching product, the SDX100, and asmall modular switch for wireless local loop (including ISDN) applications, the SDX-RB


Samsung CDMA BTS

■ Claimed capability for configuration up to 7 carriers■ Omni, 2-sector, 3-sector configurations■ Claimed capacity of approx. 20 calls/channel/sector■ Large RF Footprint■ 800, 1800, 1900 versions available■ Samsung has proposed to some customers BTS configurations

compatible with Nortel BSCs



■ Samsung’s network architecture is typical of other networks

• includes the same basic elements as Qualcomm, Nortel, Motorola, and Lucent

• uses Qualcomm chipsets■ To date, Samsung has not found

network customers in North America, despite live demonstrations at industry exhibitions

■ Samsung is known in North America primarily for its handsets


Course 134

CDMA Handset ArchitectureCDMA Handset Architecture


Functional Anatomy of a CDMA Handset

Duplexer &Bandpass

FiltersIF

BPFMixerLNA

LocalOscillator

(Synthesized)

ViterbiDecoder Vocoder

Search Correlator (Pilots)PN Generator Walsh =0

IF

CPU &Control

Algorithms

VocoderConv. Encoder& Symbol Rep.

BlockInterleaver

OrthogonalModulator

Data BurstRandomizer

Direct Seq.Spreading

QuadratureSpreading

BasebandFiltering

IF Modulator

PowerAmplifier

IF

AntennaReceiver

Transmitter

bits

bitsaudio

audio

symbolschips

Mixer

chips symbols symbols

RF IF

RF

RF

LO

LO

IF

Open Loop Pwr Control

messages

messagesLONG CODE Generator

IF

IF Transmit Gain Adjust: Closed Loop Pwr Control

Traffic CorrelatorPN Generator Walsh Generator




The Rake Receiver

■ Every frame, handset uses combined outputs of the three trafficcorrelators (“rake fingers”)

■ Each finger can independently recover a particular PN offset andWalsh code

■ Fingers can be targeted on delayed multipath reflections, or even on different BTSs

■ Searcher continuously checks pilots

Handset Rake Receiver

RF

PN Walsh

PN Walsh

PN Walsh

SearcherPN W=0

ΣVoice,Data,

Messages

Pilot Ec/Io

BTS

BTS


CDMA Soft Handoff Mechanics

■ CDMA soft handoff is driven by the handset• Handset continuously checks available pilots• Handset tells system pilots it currently sees• System assigns sectors (up to 6 max.), tells handset• Handset assigns its fingers accordingly• All messages sent by dim-and-burst, no muting!

■ Each end of the link chooses what works best, on a frame-by-frame basis!

• Users are totally unaware of handoff


RFPN Walsh

PN Walsh

PN Walsh

SearcherPN W=0

ΣVoice,Data,

Messages

Pilot Ec/Io

BTS

BSCSwitch

BTS

Sel.


Adventures in Call Processing5 Minutes in the Life of a CDMA Handset

Adventures in Call Processing5 Minutes in the Life of a CDMA Handset

30 Seconds

(that’s all we’ve got time to do in one day!)


Our Call Processing Adventures

■ Layer-3 Messaging Review■ Let’s Acquire the System!■ Let’s do an Idle Mode Handoff!■ Let’s Register!■ Let’s Receive an Incoming Call!■ Let’s Make an Outgoing Call!■ Let’s End a Call!■ Let’s Receive Notification of a Voice Message!■ Let’s Do a Handoff!


Layer-3 Messaging ReviewLayer-3 Messaging Review

CDMA Call Processing


How CDMA Messages are Sent

■ CDMA messages on both forward and reverse traffic channels are normally sent via dim-and-burst

■ Messages include many fields of binary data

■ The first byte of each message identifies message type: this allows the recipient to parse the contents

■ To ensure no messages are missed, all CDMA messages bear serial numbers and important messages contain a bit requesting acknowledgment

■ Messages not promptly acknowledged are retransmitted several times. If not acknowledged, the sender may release the call

■ Field data processing tools capture and display the messages for study

MSG_TYPE (‘00000110’)

ACK_SEQ

MSG_SEQ

ACK_REQ

ENCRYPTION

ERRORS_DETECTED

POWER_MEAS_FRAMES

LAST_HDM_SEQ

NUM_PILOTS

PILOT_STRENGTH

RESERVED (‘0’s)

8

3

3

1

2

5

10

2

4

6

0-7

NUM_PILOTS occurrences of this field:

Field Length (in bits)

EXAMPLE: A POWER MEASUREMENT

REPORT MESSAGE

t


Message Vocabulary: Acquisition & Idle StatesSync Channel

Sync Channel Msg

Pilot Channel

No Messages

Paging Channel

Access Parameters Msg

System Parameters Msg

CDMA Channel List Msg

Extended SystemParameters Msg

Extended NeighborList Msg

Global ServiceRedirection Msg

Order Msg•Base Station Acknowledgment

•Lock until Power-Cycled• Maintenance required

many others…..

AuthenticationChallenge Msg

Status Request Msg

Feature Notification Msg

TMSI Assignment Msg

Channel AssignmentMsg

SSD Update Msg

Service Redirection Msg

General Page Msg

Null Msg Data Burst Msg

Access Channel

Registration Msg

Order Msg• Mobile Station Acknowldgment• Long Code Transition Request

• SSD Update Confirmationmany others…..

Origination Msg

Page Response Msg

Authentication ChallengeResponse Msg

Status Response Msg

TMSI AssignmentCompletion Message

Data Burst Msg

BTS


Message Vocabulary: Conversation State

Reverse Traffic Channel

Order Message• Mobile Sta. Acknowledgment

•Long Code Transition Request

• SSD Update Confirmation• Connect

Authentication ChallengeResponse Msg

Flash WithInformation Msg

Data Burst Message

Pilot StrengthMeasurement Msg

Power MeasurementReport Msg

Send Burst DTMF Msg

OriginationContinuation Msg

Handoff Completion Msg

Parameters ResponseMessage

Service Request Msg

Service Response Msg

Service ConnectCompletion Message

Service Option ControlMessage

Status Response Msg

TMSI AssignmentCompletion Message

Forward Traffic ChannelOrder Msg

• Base Station Acknowledgment • Base Station Challenge

Confirmation• Message Encryption Mode

AuthenticationChallenge Msg

Alert WithInformation Msg

Data Burst Msg

Analog HandoffDirection Msg

In-Traffic SystemParameters Msg

Neighbor ListUpdate Msg

Send Burst DTMF Msg

Power ControlParameters Msg.

Retrieve Parameters Msg

Set Parameters Msg

SSD Update Msg

Flash WithInformation Msg

Mobile StationRegistered Msg

Status Request Msg

Extended HandoffDirection Msg

Service Request Msg

Service Response Msg

Service Connect Msg

Service OptionControl Msg

TMSI Assignment Msg


Let’s Acquire the System!Let’s Acquire the System!



Find a Frequency with a CDMA RF Signal

Mobile scans forward link frequencies:(Cellular or PCS, depending on model)

History ListPreferred Roaming List

until a CDMA signal is found.NO CDMA?! Go to AMPS,

or to a power-saving standby mode

HISTORYLIST

Last-used:Freq/SID xFreq/SID yFreq/SID zFreq/SID tFreq/SID uetc.

FREQUENCY LISTS:PREFERREDROAMINGLIST

Freq/SID 1Freq/SID 2Freq/SID 3Freq/SID 4Freq/SID 5etc.

Forward Link Frequencies(Base Station Transmit)

A D B E F C unlic.data

unlic.voice A D B E F C

1850MHz. 1910MHz. 1990 MHz.1930MHz.

1900 MHz. PCS Spectrum

824 MHz. 835 845 870 880 894

869

849

846.5825

890

891.5

Paging, ESMR, etc.A B A B

800 MHz. Cellular Spectrum

Reverse Link Frequencies(Mobile Transmit)


Find Strongest Pilot, Read Sync Channel

Rake Fingers!"#

Reference PN

Active Pilot

Ec/Io

00

32K512

ChipsPN

1. Pilot Searcher Scans the Entire Range of PNs

All PN Offsets0

-20

98/05/24 23:14:09.817 [SCH] Sync Channel MessageMSG_LENGTH = 208 bitsMSG_TYPE = Sync Channel MessageP_REV = 3MIN_P_REV = 2SID = 179NID = 0PILOT_PN = 168 Offset IndexLC_STATE = 0x0348D60E013SYS_TIME = 98/05/24 23:14:10.160LP_SEC = 12LTM_OFF = -300 minutesDAYLT = 0PRAT = 9600 bpsRESERVED = 1

2. Put Rake finger(s) on strongest available PN, decode Walsh 32, and read Sync Channel Message

SYNC CHANNEL MESSAGE


RF≈ x ≈

LO Srch PN??? W0

F1 PN168 W32F2 PN168 W32F3 PN168 W32


The System Determination Algorithm (SDA)

Preferred Only Bit TRUEFALSE

Acquisition Index0 CDMA channels

CDMA channelsAnalog BlockAnalog Block

123

350,40050, 100AB

System RecordsSID Priority4139

NID65535

PREFPref

GEONew

Index Roam IndicatorMore 0 Off

59 65535 Pref Same More 2 On52 65535 Pref Same More 3 Flash67 65535 Neg Same Same 3 Short-short-long

4412 65535 Pref New More 1 Off

61737 226 Neg New More 0 Off: : : : : : :

Every three minutes idle phones rescan for any more-preferred signals in the current Geo Group. This is called “climbing the GEO group”.

65535 is a “wildcard” NID. The phone is to accept any NID it sees on this system.

There are 29 Acq Indexes in the current PRL. It is normal for some to contain duplicate channels.

The last system record is not a real system. It merely contains the version number of the PRl and is used by some phones to allow displaying the version.

Preferred “more” than the following record.

Some records are merely analog “Guideposts” to allow the phone to recognize where it is and position into the proper GEO group “GEO confinement”.

When the phone loses service, it scans the list of channels in its current GEO group.

Handsets can be programmed with their Preferred Only bit set to True or False. If True, the handset can only used preferred systems. If False, the handset can use non-preferred systems, but will prefer preferred systems when available.


How Idle Mobiles Choose CDMA Carriers■ At turnon, Idle mobiles use proprietary algorithms to find the initial CDMA

carrier intended for them to use■ Within that CDMA signal, two types of paging channel messages could

cause the idle mobile to choose another frequency: CDMA Channel List Message and GSRM

Go to last frequency from MRU

Strongest PN, read

SyncIs SID

permitted?

No Signal

Preferred Only Bit 0

Denied SIDRead

Paging Channel

CDMA Ch List Message

Global Svc Redir Msg

HASH using IMSI

my ACCOLC? redirect

Is better SID

available?

PRLMRU Acq IdxYes

NoF1F2F3

to Analog

to another CDMA frequency or system

Config Messages:

remain

Steps from the CDMA standards

Steps from proprietary

SDAs

Proprietary SDA

databases

Start

LegendTypical MobileSystem Determination Algorithm


How an Idle Mobile might change Carriers:

■ Method 1: Hashing from CDMA Channel List Message• Message gives list of carrier frequencies used on its sector• Mobiles Hash using their IMSIs (phone number), randomly select• After hashing, the mobile will immediately jump to its chosen carrier• End result: roughly equal division of idle mobiles among all available

carriers

How Mobiles

Frequencies in Channel

List

Hash 310 Digit IMSI Use Freq. #

6153000124 16153000125 26153000126 1

6153000127 1

6153000128 36153000129 36153000130 1

6153000131 2

6153000132 16153000133 1

98/05/24 23:14:10.786 [PCH] CDMA Channel List MessageMSG_LENGTH = 96 bitsMSG_TYPE = CDMA Channel List MessagePILOT_PN = 168 Offset IndexCONFIG_MSG_SEQ = 0CDMA_FREQ = 100 CDMA_FREQ = 125 CDMA_FREQ = 175 RESERVED = Field Omitted

TYPICAL CDMA CHANNEL LIST MESSAGE


How an Idle Mobile might change Carriers:■ Method 2: GSRM Global Service Redirection Message

• A GSRM on the Paging Channel redirects to another carrier or system, all mobiles whose Access Overload Classes (ACCOLC) are listed within the message

• A phone’s ACCOLC is normally equal to the last digit of its number• The GSRM can be set to send any desired ACCOLC groups of

mobiles to other carriers; chosen ACCOLCs determine percentages• Either GSRM or Hashing methods can be used, but not both!

98/05/17 24:21.566 Paging Channel: Global Service RedirectionPILOT_PN: 168, MSG_TYPE: 96, CONFIG_MSG_SEQ: 0Redirected access overload classes: { 0, 1 }, RETURN_IF_FAIL: 0, DELETE_TMSI: 0, Redirection to an analog system: EXPECTED_SID = 0 Do not ignore CDMA Available indicator on the redirected analog systemAttempt service on either System A or B with the custom system selection process

EXAMPLE GLOBAL SERVICE REDIRECTION MESSAGE


The Configuration Messages

■ After reading the Sync Channel, the mobile is now capable of reading the Paging Channel, which now monitors constantly

■ Before it is allowed to transmit or operate on this system, the mobile must collect a complete set of configuration messages

■ Collection is a short process -- all configuration messages are repeated on the paging channel every 1.28 seconds

■ The configuration messages contain sequence numbers so the mobile can recognize if any of the messages have been freshly updated as it continues to monitor the paging channel

• Access parameters message sequence number• Configuration message sequence number• If a mobile notices a changed sequence number, or if 600

seconds passes since the last time these messages were read, the mobile reads all of them again


Go to Paging Channel, Get Configured

Rake Fingers!"#

Reference PN

Active Pilot

Ec/Io

00

32K512

ChipsPN

All PN Offsets0

-20

Keep Rake finger(s) on strongest available PN, decode Walsh 1,

and monitor the Paging Channel

Read the Configuration Messages

Access Parameters Msg

System Parameters Msg

CDMA Channel List Msg

Extended SystemParameters Msg (*opt.)

(Extended*) NeighborList Msg

Global ServiceRedirection Msg (*opt.)

Now we’re ready to operate!!


RF≈ x ≈

LO Srch PN??? W0

F1 PN168 W01F2 PN168 W01F3 PN168 W01


Two Very Important Configuration Messages

98/05/24 23:14:10.427 [PCH] MSG_LENGTH = 184 bitsMSG_TYPE = Access Parameters MessagePILOT_PN = 168 Offset IndexACC_MSG_SEQ = 27ACC_CHAN = 1 channelNOM_PWR = 0 dBINIT_PWR = 0 dBPWR_STEP = 4 DbNUM_STEP = 5 Access Probes MaximumMAX_CAP_SZ = 4 Access Channel Frames MaximumPAM_SZ = 3 Access Channel FramesPersist Val for Acc Overload Classes 0-9 = 0Persist Val for Acc Overload Class 10 = 0Persist Val for Acc Overload Class 11 = 0Persist Val for Acc Overload Class 12 = 0Persist Val for Acc Overload Class 13 = 0Persist Val for Acc Overload Class 14 = 0Persist Val for Acc Overload Class 15 = 0Persistance Modifier for Msg Tx = 1 Persistance Modifier for Reg = 1 Probe Randomization = 15 PN chipsAcknowledgement Timeout = 320 msProbe Backoff Range = 4 Slots MaximumProbe Sequence Backoff Range = 4 Slots Max.Max # Probe Seq for Requests = 2 SequencesMax # Probe Seq for Responses = 2 SequencesAuthentication Mode = 1Random Challenge Value = Field OmittedReserved Bits = 99

ACCESS PARAMETERS MESSAGE 98/05/24 23:14:11.126 [PCH] System Parameter MessageMSG_LENGTH = 264 bitsMSG_TYPE = System Parameters MessagePILOT_PN = 168 Offset IndexCONFIG_MSG_SEQ = 0SID = 179 NID = 0REG_ZONE = 0 TOTAL_ZONES = 0 ZONE_TIMER = 60 minMULT_SIDS = 0 MULT_NID = 0 BASE_ID = 8710BASE_CLASS = Public MacrocellularPAGE_CHAN = 1 channelMAX_SLOT_CYCLE_INDEX = 0HOME_REG = 0 FOR_SID_REG = 0 FOR_NID_REG = 1POWER_UP_REG = 0 POWER_DOWN_REG = 0PARAMETER_REG = 1 REG_PRD = 0.08 secBASE_LAT = 00D00'00.00N BASE_LONG = 000D00'00.00EREG_DIST = 0SRCH_WIN_A = 40 PN chipsSRCH_WIN_N = 80 PN chipsSRCH_WIN_R = 4 PN chipsNGHBR_MAX_AGE = 0PWR_REP_THRESH = 2 framesPWR_REP_FRAMES = 56 framesPWR_THRESH_ENABLE = 1PWR_PERIOD_ENABLE = 0PWR_REP_DELAY = 20 framesRESCAN = 0T_ADD = -13.0 Db T_DROP = -15.0 dB T_COMP = 2.5 dBT_TDROP = 4 secEXT_SYS_PARAMETER = 1RESERVED = 0GLOBAL_REDIRECT = 0

SYSTEM PARAMETERS MESSAGE


Four Additional Configuration Messages

98/05/24 23:14:10.946 [PCH] Extended System Parameters MessageMSG_LENGTH = 104 bitsMSG_TYPE = Extended System Parameters MessagePILOT_PN = 168 Offset IndexCONFIG_MSG_SEQ = 0 RESERVED = 0PREF_MSID_TYPE = IMSI and ESNMCC = 000 IMSI_11_12 = 00 RESERVED_LEN = 8 bitsRESERVED_OCTETS = 0x00 BCAST_INDEX = 0RESERVED = 0

EXTENDED SYSTEM PARAMETERS

98/05/17 24:21.566 Paging Channel: Global Service RedirectionPILOT_PN: 168, MSG_TYPE: 96, CONFIG_MSG_SEQ: 0Redirected access overload classes: { 0, 1 }, RETURN_IF_FAIL: 0, DELETE_TMSI: 0, Redirection to an analog system: EXPECTED_SID = 0 Do not ignore CDMA Available indicator on the redirected analog systemAttempt service on either System A or B with the custom system selection process

GLOBAL SERVICE REDIRECTION

98/05/24 23:14:11.486 [PCH] Neighbor List MessageMSG_LENGTH = 216 bitsMSG_TYPE = Neighbor List MessagePILOT_PN = 168 Offset IndexCONFIG_MSG_SEQ = 0PILOT_INC = 4 Offset IndexNGHBR_CONFIG = 0 NGHBR_PN = 220 Offset IndexNGHBR_CONFIG = 0 NGHBR_PN = 52 Offset IndexNGHBR_CONFIG = 0 NGHBR_PN = 500 Offset IndexNGHBR_CONFIG = 0 NGHBR_PN = 8 Offset IndexNGHBR_CONFIG = 0 NGHBR_PN = 176 Offset IndexNGHBR_CONFIG = 0 NGHBR_PN = 304 Offset IndexNGHBR_CONFIG = 0 NGHBR_PN = 136 Offset IndexNGHBR_CONFIG = 0 NGHBR_PN = 384 Offset IndexNGHBR_CONFIG = 0 NGHBR_PN = 216 Offset IndexNGHBR_CONFIG = 0 NGHBR_PN = 68 Offset IndexNGHBR_CONFIG = 0 NGHBR_PN = 328 Offset IndexNGHBR_CONFIG = 0 NGHBR_PN = 112 Offset IndexRESERVED = 0

NEIGHBOR LIST

98/05/24 23:14:10.786 [PCH] CDMA Channel List MessageMSG_LENGTH = 72 bitsMSG_TYPE = CDMA Channel List MessagePILOT_PN = 168 Offset IndexCONFIG_MSG_SEQ = 0CDMA_FREQ = 283RESERVED = Field Omitted

CDMA CHANNEL LIST MESSAGE


Let’s do an Idle Mode Handoff!

Let’s do an Idle Mode Handoff!



Idle Mode Handoff

■ An idle mobile always demodulates the best available signal• In idle mode, it isn’t possible to do soft handoff and listen to

multiple sectors or base stations at the same time -- the paging channel information stream is different on each sector, not synchronous -- just as the TV news programs on different networks are not in sync word-by-word if viewed together

• Since a mobile can’t combine signals, the mobile must switch quickly, always enjoying the best available signal

■ The mobile’s pilot searcher is constantly checking neighbor pilots■ If the searcher notices a better signal, the mobile continues on the

current paging channel until the end of the current superframe, then instantly switches to the paging channel of the new signal

• The system doesn’t know the mobile did this! (Does NBC’s Tom Brokaw know you just switched your TV to CNN?)

■ On the new paging channel, if the mobile learns that registration is required, it re-registers on the new sector


Idle Mode on the Paging Channel: Meet the Neighbors, track the Strongest Pilot

Ec/Io

All PN Offsets

00

32K512

ChipsPN

0

-20

Neighbor Set

The phone’s pilot searcher constantly checks the pilots listed in the Neighbor List Message

If the searcher ever notices a neighbor pilot substantially stronger than the current reference pilot, it becomes the new reference pilot

and the phone switches over to its paging channel on the next superframe.This is called an idle mode handoff.

Rake Fingers !"#

Reference PN

Active Pilot

SRCH_WIN_A

SRCH_WIN_N

Mobile Rake RX

Srch PN??? W0

F1 PN168 W01F2 PN168 W01F3 PN168 W01


Phone Operation on the Access Channel

■ A sector’s Paging Channel announces 1 (typ) to 32 (max) Access Channels: PN Long Code offsets for mobiles to use if accessing the system.

• For mobiles sending Registration, Origination, Page Responses

• Base Station always listening!■ On the access channel, phones are not

yet under BTS closed-loop power control!■ Phones access the BTS by “probing” at

power levels determined by receive power and an open loop formula

• If “probe” not acknowledged by BTS within ACC_TMO (~400 mS.), phone will wait a random time (~200 mS) then probe again, stronger by PI db.

• There can be 15 max. (typ. 5) probes in a sequence and 15 max. (typ. 2) sequences in an access attempt

• most attempts succeed on first probe!■ The Access Parameters message on the

paging channel announces values of all related parameters

ACCESS

RV TFC

BTS

Channel Assnmt. Msg.

Origination Msg

Base Sta. Acknlgmt. Order

TFC frames of 000s

TFC preamble of 000s


Mobile Sta. Ackngmt. Order

Service Connect Msg.

Svc. Connect Complete Msg


Call is Established!

MSProbing

PAGING

FW TFC

PAGING

RV TFC

FW FC

RV TFC

FW TFC

FW TFC

A Successful Access Attempt

a Probe Sequencean Access Attempt

Success!

an Access Probe


Let’s Register!Let’s Register!



Registration

■ Registration is the process by which an idle mobile lets the system know it’s awake and available for incoming calls

• this allows the system to inform the mobile’s home switch of the mobile’s current location, so that incoming calls can be delivered

• registration also allows the system to intelligently page the mobile only in the area where the mobile is currently located, thereby eliminating useless congestion on the paging channels in other areas of the system

■ There are many different conditions that could trigger an obligation for the mobile to register

• there are flags in the System Parameters Message which tell the mobile when it must register on the current system


An Actual Registration

16:18:27.144 Access Channel: Registration ACK_SEQ: 7 MSG_SEQ: 1 ACK_REQ: 1 VALID_ACK: 0ACK_TYPE: 0MSID_TYPE: 3, ESN: [0x 01 99 0d fc]MFR 1, Reserved 38, Serial Number 69116,IMSI: (Class: 0, Class_0_type: 1) [0x 01 8d 31 74 29 36]00-416-575-0421AUTH_MODE: 0REG_TYPE: Timer-basedSLOT_CYCLE_INDEX: 2MOB_P_REV: 1EXT_SCM: 1SLOTTED_MODE: 1MOB_TERM: 1

REGISTRATION MESSAGE

18:26.826 [PCH] System Parameters Message Pilot_PN: 32CONFIG_MSG_SEQ: 14 SID: 16420 NID: 0,REG_ZONE: 0 TOTAL_ZONES: 0 Zone timer length (min): 1MULT_SIDS: 0 MULT_NIDS: 0 BASE_ID: 1618 BASE_CLASS: ReservedPAG_CHAN: 1 MAX_SLOT_CYCLE_INDEX: 2 HOME_REG: 1 FOR_SID_REG: 1 FOR_NID_REG: 1, POWER_UP_REG: 1 POWER_DOWN_REG: 1 PARAMETER_REG: 1 Registration period (sec): 54 Base station 0°00´00.00¨ Lon., 0°00´00.00° Lat. REG_DIST: 0SRCH_WIN_A (PN chips): 28 SRCH_WIN_N (PN chips): 100, SRCH_WIN_R (PN chips): 130 NGHBR_MAX_AGE: 2PWR_REP_THRESH: 2 PWR_REP_FRAMES (frames): 15PWR_THRESH_ENABLE: 1 PWR_PERIOD_ENABLE: 0, PWR_REP_DELAY: 1 (4 frames) RESCAN: 0, T_ADD: -14.0dB T_DROP: -16.0dB T_COMP: 2.5dB, T_TDROP: 4s EXT_SYS_PARAMETER: 1 EXT_NGHBR_LIST: 1 GLOBAL_REDIRECT: 0

SYSTEM PARAMETERS MESSAGE

16:18:27.506 Paging Channel: Order ACK_SEQ: 1 MSG_SEQ: 0 ACK_REQ: 0 VALID_ACK: 1 MSID_TYPE: 2 IMSI: (Class: 0, Class_0_type: 3) [0x 02 47 8d 31 74 29 36] (134) 00-416-575-0421Order type: Base Station Acknowledgement Order

BASE STATION ACKNOWLEDGMENT

The System Parameters Message tells all mobiles when they should register.

This mobile notices that it is obligated to register, so it transmits a Registration

Message.

The base station confirms that the mobile’s registration message was received. We’re officially registered!


Let’s Receive an incoming Call!

Let’s Receive an incoming Call!



Receiving an Incoming Call

■ All idle mobiles monitor the paging channel to receive incoming calls.

■ When an incoming call appears, the paging channel notifies the mobile in a General Page Message.

■ A mobile which has been paged sends a Page Response Message on the access channel.

■ The system sets up a traffic channel for the call, then notifies the mobile to use it with a Channel Assignment Message.

■ The mobile and the base station notice each other’s traffic channel signals and confirm their presence by exchanging acknowledgment messages.

■ The base station and the mobile negotiate what type of call this will be -- I.e., 13k voice, etc.

■ The mobile is told to ring and given a “calling line ID” to display.■ When the human user presses the send button, the audio path is

completed and the call proceeds.


An Actual Page and Page Response

98/05/24 23:14:46.425 [ACH] Page Response MessageMSG_LENGTH = 216 bitsMSG_TYPE = Page Response MessageACK_SEQ = 1 MSG_SEQ = 2 ACK_REQ = 1VALID_ACK = 1 ACK_TYPE = 2MSID_TYPE = IMSI and ESN MSID_LEN = 9 octetsESN = 0xD30E415C IMSI_CLASS = 0IMSI_CLASS_0_TYPE = 0 RESERVED = 0IMSI_S = 6153300644AUTH_MODE = 1AUTHR = 0x307B5 RANDC = 0xC6 COUNT = 0MOB_TERM = 1 SLOT_CYCLE_INDEX = 0MOB_P_REV = 3 SCM = 106REQUEST_MODE = Either Wide Analog or CDMA OnlySERVICE_OPTION = 32768 PM = 0NAR_AN_CAP = 0 RESERVED = 0

PAGE RESPONSE MESSAGE

98/05/24 23:14:46.127 [PCH] General Page MessageMSG_LENGTH = 128 bits MSG_TYPE = General Page MessageCONFIG_MSG_SEQ = 1 ACC_MSG_SEQ = 20CLASS_0_DONE = 1CLASS_1_DONE = 1 RESERVED = 0BROADCAST_DONE = 1 RESERVED = 0ADD_LENGTH = 0 bits ADD_PFIELD = Field OmittedPAGE_CLASS = 0 PAGE_SUBCLASS = 0MSG_SEQ = 1 IMSI_S = 6153300644SPECIAL_SERVICE = 1SERVICE_OPTION = 32768RESERVED = Field Omitted

GENERAL PAGE MESSAGE

98/05/24 23:14:46.768 [PCH] Order MessageMSG_LENGTH = 112 bitsMSG_TYPE = Order MessageACK_SEQ = 2 MSG_SEQ = 0 ACK_REQ = 0VALID_ACK = 1 ADDR_TYPE = IMSI ADDR_LEN = 40 bitsIMSI_CLASS = 0 IMSI_CLASS_0_TYPE = 0 RESERVED = 0 IMSI_S = 6153300644ORDER = Base Station Acknowledgement OrderADD_RECORD_LEN = 0 bitsOrder-Specific Fields = Field Omitted RESERVED = 0


The system pages the mobile, 615-330-0644.

The base station confirms that the mobile’s page response was received. Now the

mobile is waiting for channel assignment,expecting a response within 12 seconds.

The mobile responds to the page.


Channel Assignment and Traffic Channel Confirmation

18:14:47.598 Reverse Traffic Channel: Order ACK_SEQ: 0 MSG_SEQ: 0 ACK_REQ: 0 ENCRYPTION: 0Mobile Station Acknowledgement Order

MOBILE STATION ACKNOWLEDGMENT

18:14:47.027 Paging Channel: Channel Assignment ACK_SEQ: 2 MSG_SEQ: 1 ACK_REQ: 0 VALID_ACK: 1MSID_TYPE: 2 IMSI: (Class: 0, Class_0_type: 0) [0x 01 f8 39 6a 15] 615-330-0644 ASSIGN_MODE: Traffic Channel AssignmentADD_RECORD_LEN: 5 FREQ_INCL: 1 GRANTED_MODE: 2CODE_CHAN: 43 FRAME_OFFSET: 2ENCRYPT_MODE: Encryption disabledBAND_CLASS: 800 MHz cellular bandCDMA_FREQ: 283

CHANNEL ASSIGNMENT MESSAGE

18:14:47.581 Forward Traffic Channel: Order ACK_SEQ: 7 MSG_SEQ: 0 ACK_REQ: 1 ENCRYPTION: 0 USE_TIME: 0 ACTION_TIME: 0Base Station Acknowledgement Order


Only about 400 ms. after the base station acknowledgment order, the mobile receives

the channel assignment message.

The base station is already sending blank frames on

the forward channel,using the assigned Walsh code.

The mobile sees at least two good blank frames in a row on

the forward channel, and concludes this is the right traffic channel. It sends a preamble of two blank frames of its own on the reverse traffic channel.

The base station acknowledges receiving the mobile’s preamble.

The mobile station acknowledges the base station’s acknowledgment.

Everybody is ready!


Service Negotiation and Mobile Alert

18:14:47.835 Reverse Traffic Channel: Service Connect Completion ACK_SEQ: 1 MSG_SEQ: 3 ACK_REQ: 1 ENCRYPTION: 0 SERV_CON_SEQ: 0

SERVICE CONNECT COMPLETE MSG.

18:14:47.760 Forward Traffic Channel: Service Connect ACK_SEQ: 0 MSG_SEQ: 1 ACK_REQ: 0 ENCRYPTION: 0USE_TIME: 0 ACTION_TIME: 0 SERV_CON_SEQ: 0Service Configuration: supported Transmission: Forward Traffic Channel Rate (Set 2): 14400, 7200, 3600, 1800 bps Reverse Traffic Channel Rate (Set 2): 14400, 7200, 3600, 1800 bps Service option: (6) Voice (13k) (0x8000) Forward Traffic Channel: Primary Traffic Reverse Traffic Channel: Primary Traffic

SERVICE CONNECT MESSAGENow that both sides have arrived on the

traffic channel, the base station proposes that the requested call

actually begin.

The mobile agrees and says its ready to play.

18:14:47.961 Forward Traffic Channel: Alert With Information ACK_SEQ: 3 MSG_SEQ: 1 ACK_REQ: 1 ENCRYPTION: 0SIGNAL_TYPE = IS-54B Alerting ALERT_PITCH = Medium Pitch (Standard Alert)SIGNAL = Long RESERVED = 0RECORD_TYPE = Calling Party NumberRECORD_LEN = 96 bitsNUMBER_TYPE = National NumberNUMBER_PLAN = ISDN/Telephony Numbering PlanPI = Presentation Allowed SI = Network ProvidedCHARi = 6153000124 RESERVED = 0 RESERVED = 0

ALERT WITH INFORMATION MESSAGE

The base station orders the mobile to ring, and gives it the calling party’s number to display.

18:14:48.018 Reverse Traffic Channel: Order ACK_SEQ: 1 MSG_SEQ: 4 ACK_REQ: 0ENCRYPTION: 0 Mobile Station Acknowledgement Order

The mobile says it’s ringing.

SERVICE CONNECT COMPLETE is a major milestone in call processing. Up until now, this was an access attempt.

Now it is officially a call.


The Human Answers! Connect Order

The mobile has been ringing for several seconds. The human user finally comes over and presses the send

button to answer the call.

Now the switch completes the audio circuit and the two callers can talk!

18:14:54.920 Forward Traffic Channel: Order ACK_SEQ: 0 MSG_SEQ: 1 ACK_REQ: 0 ENCRYPTION: 0 USE_TIME: 0 ACTION_TIME: 0 Base Station Acknowledgement Order


18:14:54.758 Reverse Traffic Channel: Order ACK_SEQ: 6 MSG_SEQ: 0 ACK_REQ: 1 ENCRYPTION: 0 Connect Order

CONNECT ORDER


Let’s make an Outgoing Call!Let’s make an Outgoing Call!



Placing an Outgoing Call

■ The mobile user dials the desired digits, and presses SEND.■ Mobile transmits an Origination Message on the access channel.■ The system acknowledges receiving the origination by sending a

base station acknowledgement on the paging channel.■ The system arranges the resources for the call and starts

transmitting on the traffic channel.■ The system notifies the mobile in a Channel Assignment Message

on the paging channel.■ The mobile arrives on the traffic channel.■ The mobile and the base station notice each other’s traffic channel

signals and confirm their presence by exchanging acknowledgment messages.

■ The base station and the mobile negotiate what type of call this will be -- I.e., 13k voice, etc.

■ The audio circuit is completed and the mobile caller hears ringing.


Origination17:48:53.144 Access Channel: Origination ACK_SEQ: 7 MSG_SEQ: 6 ACK_REQ: 1 VALID_ACK: 0 ACK_TYPE: 0 MSID_TYPE: 3 ESN: [0x 00 06 98 24] MFR 0 Reserved 1 Serial Number 170020 IMSI: (Class: 0, Class_0_type: 0) [0x 03 5d b8 97 c2] 972-849-5073AUTH_MODE: 0 MOB_TERM: 1SLOT_CYCLE_INDEX: 2 MOB_P_REV: 1 EXT_SCM: 1DualMode: 0 SLOTTED_MODE: 1 PowerClass: 0REQUEST_MODE: CDMA only SPECIAL_SERVICE: 1 Service option: (6) Voice (13k) (0x8000) PM: 0 DIGIT_MODE: 0 MORE_FIELDS: 0 NUM_FIELDS: 11Chari: 18008900829 NAR_AN_CAP: 0

ORIGINATION MESSAGE

17:48:53.487 Paging Channel: Order ACK_SEQ: 6 MSG_SEQ: 0 ACK_REQ: 0 VALID_ACK: 1 MSID_TYPE: 2IMSI: (Class: 0, Class_0_type: 0) [0x 03 5d b8 97 c2] 972-849-5073 Base Station Acknowledgement Order


The mobile sends an origination message

on the access channel.

The base station confirms that the origination message

was received.17:48:54.367 Paging Channel: Channel Assignment ACK_SEQ: 6 MSG_SEQ: 1 ACK_REQ: 0 VALID_ACK: 1MSID_TYPE: 2 IMSI: (Class: 0, Class_0_type: 0) [0x 03 5d b8 97 c2] 972-849-5073 ASSIGN_MODE: Traffic Channel Assignment, ADD_RECORD_LEN: 5 FREQ_INCL: 1 GRANTED_MODE: 2CODE_CHAN: 12 FRAME_OFFSET: 0 ENCRYPT_MODE: Encryption disabled BAND_CLASS: 1.8 to 2.0 GHz PCS band CDMA_FREQ: 425

CHANNEL ASSIGNMENT MESSAGE

The base station sends a Channel Assignment

Message and the mobile goes to the traffic channel.


Traffic Channel Confirmation

17:48:54.835 Reverse Traffic Channel: Order ACK_SEQ: 0 MSG_SEQ: 0 ACK_REQ: 0 ENCRYPTION: 0 Mobile Station Acknowledgement Order

MOBILE STATION ACKNOWLEDGMENT17:48:54.757 Forward Traffic Channel: Order ACK_SEQ: 7 MSG_SEQ: 0 ACK_REQ: 1 ENCRYPTION: 0USE_TIME: 0 ACTION_TIME: 0 Base Station Acknowledgement Order


The base station is already sending blank frames on

the forward channel,using the assigned Walsh code.

The mobile sees at least two good blank frames in a row on

the forward channel, and concludes this is the right traffic channel. It sends a preamble of two blank frames of its own on the reverse traffic channel.

The base station acknowledges receiving the mobile’s preamble.

The mobile station acknowledges the base station’s acknowledgment.

Everybody is ready!


Service Negotiation and Connect Complete

17:48:55.137 Reverse Traffic Channel: Service Connect Completion ACK_SEQ: 1, MSG_SEQ: 0, ACK_REQ: 1, ENCRYPTION: 0, SERV_CON_SEQ: 0

SERVICE CONNECT COMPLETE MSG.

17:48:55.098 Forward Traffic Channel: Service Connect ACK_SEQ: 7 MSG_SEQ: 1 ACK_REQ: 1 ENCRYPTION: 0USE_TIME: 0 ACTION_TIME: 0 SERV_CON_SEQ: 0 Service Configuration Supported Transmission: Forward Traffic Channel Rate (Set 2): 14400, 7200, 3600, 1800 bpsReverse Traffic Channel Rate (Set 2): 14400, 7200, 3600, 1800 bpsService option: (6) Voice (13k) (0x8000) Forward Traffic Channel: Primary TrafficReverse Traffic Channel: Primary Traffic

SERVICE CONNECT MESSAGENow that the traffic channel is working

in both directions, the base station proposes that the requested call

actually begin.

The mobile agrees and says its ready to play.

17:48:55.779 Forward Traffic Channel: Order ACK_SEQ: 0 MSG_SEQ: 0 ACK_REQ: 0 ENCRYPTION: 0USE_TIME: 0 ACTION_TIME: 0 Base Station Acknowledgement Order


The base station agrees. SERVICE CONNECT COMPLETE is a major milestone in call processing. Up until now, this was an access attempt.

Now it is officially a call.

Now the switch completes the audio circuit and the two callers can talk!


Let’s End a Call!Let’s End a Call!



Ending A Call

■ A normal call continues until one of the parties hangs up. Thataction sends a Release Order, “normal release”.

■ The other side of the call sends a Release Order, “no reason given”.• If a normal release is seen, the call ended normally.

■ At the conclusion of the call, the mobile reacquires the system.• Searches for the best pilot on the present CDMA frequency• Reads the Sync Channel Message• Monitors the Paging Channel steadily

■ Several different conditions can cause a call to end abnormally:• the forward link is lost at the mobile, and a fade timer acts• the reverse link is lost at the base station, and a fade timer acts• a number of forward link messages aren’t acknowledged, and the

base station acts to tear down the link• a number of reverse link messages aren’t acknowledged, and the

mobile station acts to tear down the link


A Beautiful End to a Normal Call

17:49:21.715 Reverse Traffic Channel: Order ACK_SEQ: 1 MSG_SEQ: 1 ACK_REQ: 1 ENCRYPTION: 0 Release Order (normal release)

MOBILE RELEASE ORDER

BASE STATION ACKNOWLEDGMENT17:49:21.936 Forward Traffic Channel: Order ACK_SEQ: 1 MSG_SEQ: 2 ACK_REQ: 0 ENCRYPTION: 0, USE_TIME: 0 ACTION_TIME: 0 Base Station Acknowledgement Order

At the end of a normal call, this mobile user pressed end.

The mobile left the traffic channel, scanned to find the best pilot, and read

the Sync Channel Message.

BASE STATION RELEASE ORDER17:49:21.997 Forward Traffic Channel: Order ACK_SEQ: 1 MSG_SEQ: 3 ACK_REQ: 0 ENCRYPTION: 0USE_TIME: 0 ACTION_TIME: 0 Release Order (no reason given)

17:49:22.517 Sync Channel MSG_TYPE: 1 Sync Channel MessageP_REV: 1 MIN_P_REV: 1SID: 4112 NID: 2 Pilot_PN: 183 LC_STATE: 0x318fe5d84a5 SYS_TIME: 0x1ae9683dcLP_SEC: 9 LTM_OFF: -10 DAYLT: 1 Paging Channel Data Rate: 9600 CDMA_FREQ: 425

SYNC CHANNEL MESSAGE

The base station acknowledged receiving the message, then sent

a release message of its own.


Let’s receive Notificationof a Voice Message!

Let’s receive Notificationof a Voice Message!



Feature Notification

98/06/30 21:16:44.368 [PCH] Feature Notification MessageMSG_LENGTH = 144 bitsMSG_TYPE = Feature Notification MessageACK_SEQ = 0MSG_SEQ = 0ACK_REQ = 1VALID_ACK = 0ADDR_TYPE = IMSIADDR_LEN = 56 bitsIMSI_CLASS = 0IMSI_CLASS_0_TYPE = 3RESERVED = 0MCC = 134IMSI_11_12 = 00IMSI_S = 9055170325RELEASE = 0RECORD_TYPE = Message WaitingRECORD_LEN = 8 bitsMSG_COUNT = 1RESERVED = 0

FEATURE NOTIFICATION MESSAGE

The Feature Notification Message on the Paging Channel tells a specific mobile it has voice messages waiting.

There are other record types to notify the mobile of other features.

The mobile confirms it has received the notification by sending a Mobile Station Acknowledgment Order on the access

channel.



Let’s do a Handoff!Let’s do a Handoff!



The Detailed Rules of Soft Handoff

■ Handset views pilots in sets• Active: pilots of sectors actually in use• Candidates: pilots mobile requested, but

not yet set up & transmitting by system• Neighbors: pilots told to mobile by system,

as nearby sectors to check• Remaining: any pilots used by system but

not already in the other sets (div. by PILOT_INC)■ Handset sends Pilot Strength Measurement

Message to the system whenever triggered by:• It notices a pilot in neighbor or remaining set

exceeds T_ADD• An active set pilot drops below T_DROP for

T_TDROP time• A candidate pilot exceeds an active by

T_COMP■ The System may set up all requested handoffs,

or it may apply special manufacturer-specific screening criteria and authorize only some

65

Remaining

ActiveCandidateNeighbor 20

PILOT SETS

Max. M

embers

Req’d. B

y Std.

T_COMPT_ADD T_DROPT_TDROP

HANDOFF PARAMETERS

Exercise: How does a pilot in one set migrate into another set, for all cases? Identify the trigger, and the messages involved.


The Call is Already Established. What Next?Ec

/IoAll PN Offsets

0

032K

512Chips

PN

0

-20

Neighbor Set

The call is already in progress. PN 168 is the only active signal,and also is our timing reference.

Continue checking the neighbors.

If we ever notice a neighbor with Ec/Io above T_ADD,ask to use it! Send a Pilot Strength Measurement Message!

T_ADD

Rake Fingers !"#

Reference PN

Active Pilot

10752

16832000

50014080

220

! !

Mobile Rake RX

Srch PN??? W0

F1 PN168 W61F2 PN168 W61F3 PN168 W61


Mobile Requests the Handoff!

98/05/24 23:14:02.205 [RTC] Pilot Strength Measurement MessageMSG_LENGTH = 128 bitsMSG_TYPE = Pilot Strength Measurement MessageACK_SEQ = 5 MSG_SEQ = 0 ACK_REQ = 1ENCRYPTION = Encryption Mode DisabledREF_PN = 168 Offset Index (the Reference PN)PILOT_STRENGTH = -6.0 dBKEEP = 1PILOT_PN_PHASE = 14080 chips (PN220+0chips)PILOT_STRENGTH = -12.5 dBKEEP = 1PILOT_PN_PHASE = 32002 chips (PN500 + 2 chips)PILOT_STRENGTH = -11.0 dBKEEP = 1RESERVED = 0

PILOT STRENGTH MEASUREMENT MESSAGE

98/05/24 23:14:02.386 [FTC] Order MessageMSG_LENGTH = 64 bitsMSG_TYPE = Order MessageACK_SEQ = 0 MSG_SEQ = 0 ACK_REQ = 0ENCRYPTION = Encryption Mode DisabledUSE_TIME = 0 ACTION_TIME = 0ORDER = Base Station Acknowledgement OrderADD_RECORD_LEN = 0 bitsOrder-Specific Fields = Field Omitted RESERVED = 0


Just prior to this message, this particular mobile already was in handoff with PN 168 and 220. This pilot strength measurement message reports PN 500 has increased above T_Add, and the mobile wants to use it too.

The base station acknowledges receiving the Pilot Strength Measurement Message.


System Authorizes the Handoff!

98/05/24 23:14:02.926 [FTC] Extended Handoff Direction MessageMSG_LENGTH = 136 bitsMSG_TYPE = Extended Handoff Direction MessageACK_SEQ = 0 MSG_SEQ = 6 ACK_REQ = 1ENCRYPTION = Encryption Mode DisabledUSE_TIME = 0 ACTION_TIME = 0 HDM_SEQ = 0SEARCH_INCLUDED = 1 SRCH_WIN_A = 40 PN chipsT_ADD = -13.0 dB T_DROP = -15.0 dB T_COMP = 2.5 dBT_TDROP = 4 secHARD_INCLUDED = 0FRAME_OFFSET = Field OmittedPRIVATE_LCM = Field OmittedRESET_L2 = Field OmittedRESET_FPC = Field OmittedRESERVED = Field OmittedENCRYPT_MODE = Field OmittedRESERVED = Field OmittedNOM_PWR = Field OmittedNUM_PREAMBLE = Field OmittedBAND_CLASS = Field OmittedCDMA_FREQ = Field OmittedADD_LENGTH = 0PILOT_PN = 168 PWR_COMB_IND = 0 CODE_CHAN = 61PILOT_PN = 220 PWR_COMB_IND = 1 CODE_CHAN = 20PILOT_PN = 500 PWR_COMB_IND = 0 CODE_CHAN = 50RESERVED = 0

HANDOFF DIRECTION MESSAGEThe base station sends a HandofDirection Message authorizing the mobile to begin soft handoff with all three requested PNs. The pre-existing link on PN 168 will continue to use Walsh code 61, the new link on PN220 will use Walsh Code 20, and the new link on PN500 will use Walsh code 50.

The mobile acknowledges it has received the Handoff Direction Message.

98/05/24 23:14:02.945 [RTC] Order MessageMSG_LENGTH = 56 bits MSG_TYPE = Order MessageACK_SEQ = 6 MSG_SEQ = 6 ACK_REQ = 0ENCRYPTION = Encryption Mode DisabledORDER = Mobile Station Acknowledgement OrderADD_RECORD_LEN = 0 bitsOrder-Specific Fields = Field Omitted RESERVED = 0



Mobile Implements the Handoff!

The mobile searcher quickly re-checks all three PNs. It still hears their pilots!

The mobile sends a Handoff Completion Message, confirming it still wants to go

ahead with the handoff.

98/05/24 23:14:03.085 [FTC] Forward Traffic Channel: Order ACK_SEQ: 0 MSG_SEQ: 1 ACK_REQ: 0 ENCRYPTION: 0 USE_TIME: 0 ACTION_TIME: 0 Base Station Acknowledgement Order


98/05/24 23:14:02.985 [RTC] Handoff Completion MessageMSG_LENGTH = 72 bits MSG_TYPE = Handoff Completion MessageACK_SEQ = 6 MSG_SEQ = 1 ACK_REQ = 1ENCRYPTION = Encryption Mode DisabledLAST_HDM_SEQ = 0PILOT_PN = 168 Offset IndexPILOT_PN = 220 Offset IndexPILOT_PN = 500 Offset IndexRESERVED = 0

HANDOFF COMPLETION MESSAGE

The base station confirms it has received the mobile’s Handoff Completion message, and will continue with all of the links active.


Neighbor List Updated, Handoff is Complete!

98/05/24 23:14:03.245 [RTC] Order MessageMSG_LENGTH = 56 bits MSG_TYPE = Order MessageACK_SEQ = 7 MSG_SEQ = 7 ACK_REQ = 0ENCRYPTION = Encryption Mode DisabledORDER = Mobile Station Acknowledgement OrderADD_RECORD_LEN = 0 bitsOrder-Specific Fields = Field OmittedRESERVED = 0


98/05/24 23:14:03.166 [FTC] Neighbor List Update MessageMSG_LENGTH = 192 bitsMSG_TYPE = Neighbor List Update MessageACK_SEQ = 1 MSG_SEQ = 7 ACK_REQ = 1ENCRYPTION = Encryption Mode DisabledPILOT_INC = 4 Offset IndexNGHBR_PN = 164 Offset IndexNGHBR_PN = 68 Offset IndexNGHBR_PN = 52 Offset IndexNGHBR_PN = 176 Offset IndexNGHBR_PN = 304 Offset IndexNGHBR_PN = 136 Offset IndexNGHBR_PN = 112 Offset IndexNGHBR_PN = 372 Offset IndexNGHBR_PN = 36 Offset IndexNGHBR_PN = 8 Offset IndexNGHBR_PN = 384 Offset IndexNGHBR_PN = 216 Offset IndexNGHBR_PN = 328 Offset IndexNGHBR_PN = 332 Offset IndexNGHBR_PN = 400 Offset IndexNGHBR_PN = 96 Offset IndexRESERVED = 0

NEIGHBOR LIST UPDATE MESSAGE

In response to the mobile’s Handoff Completion Message, the base station assembles a new composite neighbor list including all the neighbors of each of the three active pilots.This is necessary since the mobile could be traveling toward any one of these pilots and may need to request soft handoff with any of them soon.

The mobile confirms receiving the Neighbor List Update Message. It is

already checking the neighbor list and will do so continuously from now on.

The handoff is fully established.


Handoff Now In Effect, keep checking Pilots!Ec

/IoAll PN Offsets

0

032K

512Chips

PN

0

-20

Neighbor Set

Continue checking each ACTIVE pilot. If any are less than T_DROP and remain so for T_TDROP time, send Pilot Strength Measurement Message, DROP IT!!

Continue checking each NEIGHBOR pilot. If any ever rises above T_ADD, send PSMM, ADD IT! Keep watching CANDIDATES vs ACTIVES using T_COMP, too.

T_ADD

Rake Fingers!

Reference PN

Active Set

10752

16832000

50014080

220

"#T_DROP

Mobile Rake RX

Srch PN??? W0

F1 PN168 W61F2 PN500 W50F3 PN220 W20


The Complete Picture of Handoff & Pilot Sets

T_ADD

Ec/Io

All PN Offsets

00

32K512

ChipsPN

0

-20

Neighbor Set

SRCH_WIN_N

Active Set

Candidate SetT_DROP

SRCH_WIN_A

Remaining SetT_ADD

SRCH_WIN_R

SRCH_WIN_A" #

T_DROP

Rake Fingers !

Reference PN

Pilots of sectors now used for communication

Pilots requested by mobile but not set up by system

Pilots suggested by system for more checking

All other pilots divisible by PILOT_INC but not presently in Active, Candidate, or Neighbor sets

Mobile Rake RX

Srch PN??? W0

F1 PN168 W61F2 PN500 W50F3 PN220 W20


Timing of Pilot Searcher’s Measurement Process

The searcher checks pilots in nested loops, much like meshed gears. Actives and candidatesoccupy the fastest-spinning wheel. Neighbors are next, advancingone pilot for each Act+Cand. revolution.Remaining is slowest, advancing one pilot each time the Neighbors revolve.

CURRENT PILOT SET CONTENTSA A A

C

N N N N N N N N N N N N

R R R R R R R R R R R R









R R R R

31

12112

PILOT SEARCHER VIEWED IN SEQUENCE: Typical Elapsed Time = 4 secondsA A A C N

R

A A A C A A A C A A A C A A A C A A A C A A A CN N N N N N

A A A C N A A A C A A A C A A A C A A A C A A A C A A A CN N N N N

A A A CN A A A C A A A C A A A C A A A C A A A C A A A CN N N N N N

N A A A C A A A C A A A CN N N R A A A C N A A A C A A A C A A AN N

C A A A C A A A CN N N

R

A A A C N A A A C A A A C A A AN N C A A AN

C A A A CN N Only 3 of 112 remaining set pilots have been checked thus far!

A

N

R

R

R

R

R

R

R

NN

N

N

NN N N

AA


Troubleshooting Call Events: Watch Messaging, Mobile State

■ Your current capabilities• Earlier in this course we reviewed handset call processing

states• You have just seen the entire vocabulary of messages

ordinarily used in call processing• Now you’re equipped to do serious troubleshooting of CDMA

calls!■ Auditing Call Processing Problems using messages

• Watch the messages from birth (origination) to death (release)– is the order proper? are there inappropriate responses?– are any messages repeated? why? which link is bad?– are any messages missed or not acknowledged?– are contents and included parameter values reasonable?– is the timing appropriate -- delays not too long?– track the state in which the mobile and system should be


Course 134

Handoff PerspectiveHandoff Perspective


Overall Handoff Perspective

■ Soft & Softer Handoffs are preferred, but not always possible• a handset can receive BTS/sectors simultaneously only on one

frequency • all involved BTS/sectors must connect to a networked BSCs.

Some manufacturers do not presently support this, and so are unable to do soft-handoff at boundaries between BSCs.

• frame timing must be same on all BTS/sectors■ If any of the above are not possible, handoff still can occur but can

only be “hard” break-make protocol like AMPS/TDMA/GSM• intersystem handoff: hard• change-of-frequency handoff: hard• CDMA-to-AMPS handoff: hard, no handback

– auxiliary trigger mechanisms available (RTD), Ec/Io■ Global Service Redirection Messages on outlooking sectors….


Which is better - 3-way or 6-way Soft Handoff?

■ 3 Way or 6 Way?• All handsets are capable of up to 6-way soft handoff• Nortel & Qualcomm networks allow up to 6-way soft-handoff• Lucent and Motorola networks allow only up to 3 way soft

handoff– “bug” or “feature”?– Advantage of 6-way: mobile does not depend on speedy

system reaction to handoff requests; this gives somewhat improved dropped call rates in areas with extensive RF overlap

– Disadvantage: additional channel elements are used


Optional Network-Specific Handoff Features

■ Ec/Io Handoff Candidate Screening• all networks rank the pilots reported by the mobiles, and in

cases where more candidates are proposed than the network can support in soft handoff, the soft handoff is set up using the best N pilots

• Some networks also screen candidates and apply a more conservative theory when authorizing handoffs

– some networks use T_Comp as a secondary parameter to implement hysteresis and prevent hyperactive handoffs

• Some networks are experimenting with algorithms for dynamic, adaptive assignment of T_Add, T_Drop, and T_Comp


Nortel Handoff & Channel Allocation Features

■ Inter-System Soft Handoff (ISSHO)• Soft handoff across SBS and MTX boundaries

■ Multi-Carrier Traffic Allocation (MCTA)• Intelligent carrier selection during call setup

■ Soft Handoff Reduction Algorithm (SHORA)• Eliminating unneeded excessive soft handoff to improve capacity

■ Multi_Pilot Hard HandOff (MPHHO)• Round-trip delay triggers, Pilot Beacon techniques

■ Enhanced Hard HandOff (EHHO)• Call quality triggers hard handoff when necessary

■ Multi-Mode Hard HandOff (MMHHO)• Sending capable CDMA mobiles between band classes or to analog

■ For more detail and latest improvements to all these features and algorithms, take the Nortel 1203 handoffs course!


Course 134

Nortel ISSHO:Inter-System Soft Handoff

Nortel ISSHO:Inter-System Soft Handoff


ISSHO Overview

■ Before ISSHO, mobiles could not enjoy soft handoff between BTSs on different BSCs. This caused major problems:• Hard handoffs were the only type available, with annoying

muting• If the disjoint BTSs were on the same frequency, serious

interference and capacity problems plagued the boundary area

• If the disjoint BTSs were on different frequencies, auxiliary trigger mechanisms (RTD and Pilot_Beacon) were necessary to allow the system to determine when the handoff should be implemented

■ ISSHO allows mobiles to handoff over simultaneous links through BTSs on more than one BSC• This improves call quality, reduces drops, eliminates muting• However, ISSHO requires special networking between the

BSCs involved so that packets from all BTSs can be routed to the vocoder responsible for the call


Inter-BSC/Inter-System ISSHO Configuration

■ ISSHO networks multiple BSCs’ CISs together into one virtual CIS, using T1 links or ATM• If both BSCs are on the same MTX, this is an Inter-BSC soft

handoff• If BSCs are on different MTXs, this is an intersystem soft handoff

■ BTSs on the two BSCs must be on the same frequency■ All packets from all BTSs in handoff with the mobile are routed to one

common Vocoder in one BSC

INTER-BSC/INTER-SYSTEM ISSHO CONFIGURATION

BSC1CIS

BSC2CIS

SBS

SBS

SBS

SBS

BTS BTS BTS BTS

Virtual CIS

T1s

or ATM

Bord

er


Course 134

Nortel MCTA:Multi-Carrier Traffic Allocation

Nortel MCTA:Multi-Carrier Traffic Allocation


Who Chooses Carriers during Call Setup?

■ Idle mobiles choose their carriers by Hashing or GSRM, and originate or respond to pages on those carriers

■ The system has the last word on the carrier to be used during a call• System can force the mobile to any channel it chooses for call setup

– Chosen channel is listed in the Channel Assignment Message• The System can force the mobile to any channel it chooses anytime

while the call is in progress– If any form of hard handoff trigger condition occurs, the system

can choose the carrier frequency to be commanded to the mobile in the handoff direction message

• Idle mobiles are like automobile drivers – they choose what they want to do, consistent with the rules of the road

• Mobiles in calls are like airline passengers – they board when instructed, and sit where they are told


MCTA: Choosing best Carrier for Call Setup

■ Idle-mode selection methods can help equalize the distribution of mobiles among carriers, but traffic inequalities can still occuramong carriers

■ Nortel’s proprietary Multi-Carrier Traffic Allocation feature takes current conditions into account when determining the channel fora mobile’s call• This allows carriers to supplement each other in true trunking

fashion for maximum system capacity• MCTA can be deployed on networks of up to three carriers• MCTA can be deployed on Legacy BTSs, MetroCell BTSs,

and combinations of the two types• SBS interrogates all BTSs at a site for their current available

capacities during call setup; may also use arbitrary priorities• Channel assignment is made to the carrier with the most

capacity and and/or highest preference


Initial MCTA Configuration Considerations

■ Cell requirements for MCTA use• All carriers of each sector must have same cell ID (cell number

& sector ID)• Multiple records (of individual BTSs) will share same Cell Ids

– Only one Pilot DataBase record (PDB) will exist per sector■ Selector chooses carrier during call setup

• All BTSs receive Capacity Request message and respond• PDB is used to return information from queried cell

– BTSC address, neighbor list, HO thresholds, search windows, type of cell

• PDB is configured with the following:– Frequency Priorities (can favor some frequencies over

others)– Thresholds – capacity value which triggers carrier

migration


The MCTA Call Determination Algorithm

■ The CDA is the algorithm which drives MCTA• Assigns carriers based on frequency priority and Excess

Forward Link Capacity (EFLC) threshold response• Responses received after an arbitrary time delay are ignored• CDA selects BTS with first positive relative threshold in the

Capacity Response Message• If all responses are negative, CDA will choose least negative

(closest to zero)• It’s best to set the Threshold parameter high enough that all

values are negative; otherwise, CDA will select first positive return it sees, not necessarily the best carrier


Course 134

Nortel SHORA:Soft Handoff Reduction Algorithm

Nortel SHORA:Soft Handoff Reduction Algorithm


Soft Handoff: The Tradeoffs

■ Soft Handoff improves call quality!• Mobile experiences diversity gain due to multiple

forward link pathways combined in rake receiver• System experiences more reliable reverse link ,

listening to mobile frame-by-frame over whichever BTS hears mobile best– Mobile reverse link power actually decreases

during soft handoff, improving reverse capacity■ Soft Handoff uses up resources!

• Each involved BTS must dedicate a channel element to this call while soft handoff is in effect

• Forward link: Each involved BTS uses a few percent of precious transmit power for this call

• System resources: more packet traffic over T-1s between BTSs and the BSC


IS-95A Handoff: Inflexible, Threshold Driven

■ Mobile requests soft handoff with all pilots above T_Add• This occasionally leads to some

rigid, less-than-optimum decisions!■ Problem Situation 1

• One dominant, strong signal and a lot of weak ones:– Mobile asks for them all, but

only one is really needed!■ Problem Situation 2

• Heavy pilot pollution, many signals lurk barely below the threshold– Mobile may request one or two,

but ignore the others which could have helped call survive

Pilo

t Stre

ngth

(Ec/

Io, d

b)

-3

-20

All Six sectors in

soft handoff!

T_AddActive

Active

ActiveActiveActiveActive

Pilo

t Stre

ngth

(Ec/

Io, d

b)

-3

-20

Only One Sector in soft

handoff!

T_AddActive


Two Methods for Improving Rigid Handoffs

■ IS-95B Improved Handoff Algorithm• Uses additional soft handoff parameters to make handoffs

smarter -- slopes and intercepts• Only by IS-95B-equipped mobiles can use these parameters

– pre-existing mobiles can’t benefit from the improvements– Net system improvement depends on IS-95A/IS-95B user

mix■ Nortel’s Proprietary Soft Handoff Reduction Algorithm (SHORA)

• Uses additional intelligent algorithms in system to evaluate allhandoffs requested by mobile

• Handoff performance of all mobiles is improved, not just IS-95B-capable mobiles


The IS-95B Approach to Handoff Reduction

Additional Soft Handoff Parameters:■ SOFT_SLOPE■ ADD_INTERCEPT■ DROP_INTERCEPTSpecial Selection Criteria:■ CANDIDATE CRITERIA■ NEIGHBOR>CANDIDATE CRITERIA■ ACTIVE SET REMOVAL CRITERIA


IS-95B Handoff Trigger

■ A handoff process more intelligent than fixed thresholds• Handoff events driven by smarter, situation-influenced triggers

■ Candidate Set Removal:

■ Neighbor-to-Active transition:

■ Removal from Active Set:


Nortel’s Proprietary Approach

■ The soft-handoff reduction improvements in IS-95B can be achieved without requiring all mobiles to upgrade to IS-95B

■ New Parameters are used in the Nortel Soft Handoff Reduction Algorithm (SHORA)

■ Mobiles continue to request handoffs using the original parameters T_Add, T_Drop, T_TDrop and T_Comp

• BSC analyzes pilot strength data received from each mobile• The system dynamically updates T_Add, T_Drop, T_TDrop

and T_Comp to each mobile for best performance in current situation

■ The system uses special DELTA parameters to avoid excessive soft handoff


SHORA Algorithm Operation Perspective

■ SHORA works in two main ways:■ The threshold manipulation parameters

• The main benefit of these is to ensure that mobiles in multi-pilot soft handoff situations are not restricted from asking for the pilots they need due a fixed T_Add

• These ensure that all needed pilots will be requested■ The DELTA parameters

• DELTA parameters are used to safeguard against too much soft handoff

• The delta parameters inhibit excessive soft handoff by making sure that each additional sector added in handoff is really needed

■ The DELTA parameters require careful setup!


SHORA Parameters

■ After each PSMM is received from the mobile, Nortel’s SHORA analyzes the reported strengths and applies the following parameters

■ New values of T_Add, T_Drop, T_Comp, and T_Tdrop are then communicated to the mobile for use in future handoffs

Parameter NameValid

Range, dBStep

Size, dbDatafill Values

To Disable, Set Value Function

Recommended Initial Value Comments

T_ADD_OFFSET_A 0-4 dB 0.5 dB 0 - 8 0 Offset added to T_ADD when 2 pilots active 1 - 2 dbT_ADD_OFFSET_B 0-4 dB 0.5 dB 0 - 8 0 Offset added to T_ADD when 3 or more active 1 - 2 dbT_DROP_OFFSET_A 0-4 dB 0.5 dB 0 - 8 0 Offset added to T_DROP when 2 pilots active 1 - 2 dbT_DROP_OFFSET B 0-4 dB 0.5 dB 0 - 8 0 Offset added to T_DROP when 3 or more active 1 - 2 dbT_COMP_OFFSET_A -2 to +2 dB 0.5 dB -4 to +4 0 Offset added to T_COMP when 2 pilots active 0T_COMP_OFFSET_B -2 to +2 dB 0.5 dB -4 to +4 0 Offset added to T_COMP when 3 or more active 0T_TDROP_OFFSET_B -2 to +2 sec 0.5 sec. -4 to +4 0 Offset added to T_TDROP when 3 or more active 0DELTA_6 0 to 15.5 0.5 dB 0 - 31 31 Strongest vs 6th strongest pilot strength delta 1 to 4 dbDELTA_5 0 to 15.5 0.5 dB 0 - 31 31 Strongest vs 5th strongest pilot strength delta 1 to 4 dbDELTA_4 0 to 15.5 0.5 dB 0 - 31 31 Strongest vs 4th strongest pilot strength delta 1 to 4 dbDELTA_3 0 to 15.5 0.5 dB 0 - 31 31 Strongest vs 3th strongest pilot strength delta 1 to 4 db

not recommended for use

depends on level of reduction desired,

higher = more reduction

depends on level of reduction desired,

experiment for optimum results in specific


Course 134

Nortel MPHHO:Multiple Pilot Hard Handoff

Nortel MPHHO:Multiple Pilot Hard Handoff


Comparing Hard Handoff Trigger Methods

■ Round-Trip Delay (RTD)• Generally the best method for multi-carrier/same system situations

– allows precise tailoring of where the handoffs will occur– This allows the good coverage of boundary sectors to be fully

exploited for maximum system capacity■ Pilot Beacons (PB)

• Pilot beacons are cells or scaled-down pilot-sync-paging transmitting devices which do not carry traffic but which mobiles can see, measure, and request for handoff – like police posing as fences for stolen merchandise

• The PN offsets of their pilots are specially “tagged” in the pilot database so when a mobile requests to use a beacon, the system can step in and send the mobile where it belongs – the other carrier!

■ Enhanced Hard Handoff (EHHO)• This unique method allows you to design your own trigger based on

a flexible selection of quality measurements and thresholds you specify

• EHHO is so flexible, it has its own chapter later in this course!


How Round Trip Delay Method Operates

■ Hard handoff is triggered when the system detects all the following conditions are met:• All Active pilots are defined as

CELL_BORDER in pilot database records

• The shortest measured RTD on any active sector must exceed the datafilled BorderRefPilotRTDThresh

■ Method• BTSs send RTD measurements to IHM• IHM sorts meas in order of increasing

delay• Minimum RTD is compared against

maximum BorderRefPilotRTDThresh of all active sectors

• If min. meas. RTD > max RTDThresh, HO!!

System Border

Frequency F1

Frequency F2

Datafill as Cell_BorderMobile’s path

RTD = round trip delay

IHM = Intersystem Handoff Manager

PDB = Pilot DataBase


RTD Reference Sector & First Target Sector

■ IHM uses sector with shortest RTD as Reference Sector• Not necessarily the mobile’s timing reference PN!!

■ IHM’s choice of reference sector is very important!• Datafill of “MPHHOEnabled” for the reference sector

determines whether MPHHO will be used• All datafilled target sectors of the reference sector are selected• The MSCId for the reference sector’s first target sector

becomes the target MSCId for the hard handoff– Any target CellIds not appearing with this MSCId will not be

used in the MPHHO and are not passed to the target MSC• The frequency/bandclass for the reference’s first target sector

becomes the target frequency for the hard handoff unless MCTA is enabled

– Any target CellIds lacking this frequency won’t be used in MPHHO


RTD Reference, First Target Sector, & MCTA

■ MCTA will be triggered if it is available for the first target sector• Any target CellIds lacking the MCTA-chosen frequency will not

be used in the MPHHO• Notice MCTA may result in a frequency change across an

ISSHO border!■ OMs and Billing Implications of MPHHO

• All OMs relating to the hard handoff are pegged against the first target sector

• Logs, billing, and VLR entries use the first target sector


RTD Calculations: Setting Delay Thresholds

■ RTD is the total delay the signal encounters from BTS to mobile back to BTS• Every 244.14 meters traveled adds 1 chip of delay

– 800.98 feet is 1 chip of delay• Every kilometer traveled adds 4.1 chips of delay

– 1 mile is 6.7 chips of delay■ Example in the figure at right:

• BTS to Mobile is 4 KM; delay is 4 x 4.1 = 16.4 chips• Mobile to BTS is 4 KM, delay is 4 x 4.1 = 16.4 chips• Total round-trip delay is 16.4 + 16.4 = 32.8 chips

■ Exercise: • If we want to trigger MPHHO when the mobile is 1

KM from the BTS, what RTD in chips should be set?• Ans.: 1 KM is 4.1 chips. RTD = 4.1 + 4.1 = 8.2

chips

4 KM

= 1

6.4

chip

s

MOBILE

BTS

4 KM

= 1

6.4

chip

s

RTD = 16.4 + 16.4= 32.8 chips


Pilot Beacon Triggers

■ Pilot Beacon Trigger is activated whenever• Mobile sees pilot beacon, sends

PSMM• The SHM in the BSC recognizes

the reported pilot is from a CELL_PILOT_BEACON in the PDB

• The MultiPilotHHOEnabled flag is set to allow MPHHO

■ If all the above are true, the SHM sends orders to set up the MPHHO• If SHORA is enabled, only

SHORA-acceptable pilots are set up in handoff

• If SHORA is not enabled, SHM sets up links for all requested pilots

System Border

MTX1

MTX2

Pilot_BeaconCellMobile’s path

LogicalCell


Pilot Beacon Reference and Target Sectors

■ The IHM arranges pilots from the PSMM in order of strongest-first• Pilot with strongest reported Ec/Io becomes the IHM reference sector

– IHM reference sector may not be the mobile’s reference PN!!■ IHM’s choice of reference sector is very important!

• Datafill of “MPHHOEnabled” for the reference sector determines whether MPHHO will be used

• All datafilled target sectors of the reference sector are selected• The MSCId for the reference sector’s first target sector becomes the

target MSCId for the hard handoff– Any target CellIds not appearing with this MSCId will not be used

in the MPHHO and are not passed to the target MSC• The frequency/bandclass for the reference’s first target sector

becomes the target frequency for the hard handoff unless MCTA isenabled – Any target CellIds lacking this frequency won’t be used in

MPHHO


Multiple Target Selection for MPHHO■ The main advantage of MPHHO is allowing multiple target sectors for the

hard handoff• Since most hard handoffs occur in difficult RF conditions, this feature

improves the likelihood of a successful handoff

Pilot0(VirRef)

RTD TriggerPilot_Beacon

Trigger

RTD increases

Pilot Ec/Io increases

All of Ref Pilot Targets selected

1st traverse2nd traverse3rd traverse4th traverse

Target Lists

Pilot1 Pilot2 Pilot3 Pilot4 Pilot5


Target Selection Process for Pilot_Beacon

■ Demonstration:• A PSMM is received with four pilots

– Assume already Ec/Io ranked: A, B, C, D• Their target lists are as shown at right

■ Handoff MPHHO process is:• Take ref sector A’s target list (now ABEG)• Add 1st target from second ranked sector (B) (list still

ABEG)• Add 1st target from third ranked sector ( C) (now ABEGD)• Add 1st target from fourth ranked sector ( D) (still ABEGD)• Add 2nd target from 2nd ranked sector (B) (still ABEGD)• Add 2nd target from 3rd ranked sector (C ) (still ABEGD)• Add 2nd target from 4th ranked sector (D) (now ABEGDH)• Six targets is the limit, so scanning now stops

Sector TargetCellIdListA A, B, E, GB B, A, C, FC D, E, FD B, H, J, K

Example Target List


Course 134

Nortel EHHO:Enhanced Hard Handoff

Nortel EHHO:Enhanced Hard Handoff


EHHO Background & Perspective

■ MPHHO is a big step forward in utilizing overlay sectors• Extended target lists allows RTD threshold to be pushed far

away■ When the underlay is analog or an unfriendly network, there is

desire to stretch the overlay coverage even farther if possible■ There is a need for additional trigger mechanisms to allow the call

to remain on the overlay sector(s) as long as possible• Only hand down to the underlay when call quality is impacted

■ The answer to this need is Nortel’s Enhanced Hard HandOff (EHHO)


EHHO: Using Call Quality as an HHO Trigger

■ What is EHHO?• Another Hard Handoff Triggering Mechanism, like RTD and

Pilot_Beacon■ What’s different about EHHO?

• RTD is based on absolute time delay, which is absolute distance• Pilot_Beacon is based on visibility of pilots• Neither RTD nor Pilot_Beacon triggers mean the Overlay CDMA

service is bad; in fact, premature handoff is still often triggered■ How EHHO Works

• User-configured trigger conditions are defined from many parameters– FER, Forward Traffic Gain, Eb/No are common triggers,

individually or in combinations specified by the operator• The triggers can be set to occur only when the mobile exhausts the

coverage of the CDMA overlay, making handdown appropriate■ EHHO can be deployed for individual sectors

• Allows customized response to individual sector propagation


Course 134

Nortel MMHHO:Multi-Mode Hard Handoff

Nortel MMHHO:Multi-Mode Hard Handoff


The Current Mode Algorithm

■ MMHHO performs target cell selection using the current mode algorithm, based on

• The mobile’s multimode capabilities• The created handoff target list• The current mode of operation


MMHHO Handoff Capabilities

■ This diagram shows all of the handoff types available in the MMHHO feature

■ Not all transitions are possible for all phones, but the feature supports all possible transitions

■ Note there is no handoff from Analog back to CDMA because of the long lockup time (~10 sec.) required by the mobile• Most users would assume

the call had dropped!

800 Mhz AMPS

800 Mhz CDMA

1900 Mhz CDMA

Dual ModeNetwork:

1900 CDMA800 AMPS

Dual ModeNetwork:

800 CDMA800 AMPS

Tri-Mode Network:

1900 CDMA, 800 CDMA, 800 AMPS


Bibliography“Wireless Communications Principles & Practice” by Theodore S. Rappaport. 641 pp., 10 chapters, 7 appendices.

Prentice-Hall PTR, 1996, ISBN 0-13-375536-3. If you can only buy one book, buy this one. Comprehensive summary of wireless technologies along with principles of real systems. Includes enough math for understanding and solving real problems. Good coverage of system design principles.

“The Mobile Communications Handbook” edited by Jerry D. Gibson. 577 pp., 35 chapters. CRC Press/ IEEE Press 1996, ISBN 0-8493-0573-3. $89 If you can buy only two books, buy this second. Solid foundation of modulation schemes, digital processing theory, noise, vocoding, forward error correction, excellent full-detailed expositions of every single wireless technology known today, RF propagation, cell design, traffic engineering. Each chapter is written by an expert, and well-edited for readability. Clear-language explanations for both engineers and technicians but also includes detailed mathematics for the research-inclined. Highly recommended.

“CDMA Systems Engineering Handbook” by Jhong Sam Lee and Leonard E. Miller, 1998 Artech House, ISBN 0-89006-990-5. Excellent treatment of CDMA basics and deeper theory, cell and system design principles, system performance optimization and capacity issues. Highly recommended.

“Wireless Telecom FAQs” by Clint Smith, 2001 McGraw Hill, ISBN 0-07-134102-1. Succint, lucid explanations of telecom terms in both wireless and landline technologies. Includes cellular architecture, AMPS, GSM, TDMA, iDEN, CDMA. Very thorough coverage; an excellent reference for new technical people or anyone wishing for clear explanations of wireless terms.

“CDMA RF System Engineering” by Samuel C. Yang, 1998 Artech House, ISBN 0-89006-991-3. Good general treatment of CDMA capacity considerations from mathematical viewpoint.

"CDMA: Principles of Spread Spectrum Communication" by Andrew J. Viterbi. 245 p. Addison-Wesley 1995. ISBN 0-201-63374-4, $65. Definitive very deep CDMA Theory. You can design CDMA chipsets after reading it, but beware lots of triple integrals; not very relevant to operations. Prestige collector’s item among CDMA faithful.

"Mobile Communications Engineering" 2nd. Edition by William C. Y. Lee. 689 pp. McGraw Hill 1998 $65. ISBN 0-07-037103-2 Lee’s latest/greatest reference work on all of wireless; very complete and well done.

"Spread Spectrum Communications Handbook" by Simon, Omura, Scholtz, and Levitt. 1227 pp., 15 illus., McGraw-Hill # 057629-7, $99.50 Definitive technical reference on principles of Spread Spectrum including direct sequence as used in commercial IS-95/JStd008 CDMA. Heavy theory.


Bibliography (concluded)“Wireless and Personal Communications Systems” by Garg, Smolik & Wilkes. 445 pp., Prentice Hall, 1996, $68.

ISBN 0-13-234-626-5 $68. This is the little brother of “The Mobile Communications Handbook”. Good explanation of each technology for a technical newcomer to wireless, but without quite as much authoritative math or deep theoretical insights. Still contains solid theory and discussion of practical network architecture.

"Voice and Data Communications Handbook" by Bates and Gregory 699 pp, 360 illus., McGraw-Hill # 05147-X, $65 Good authoritative reference on Wireless, Microwave, ATM, Sonet, ISDN, Video, Fax, LAN/WAN

"Communication Electronics" by Louis E. Frenzel, 2nd. Ed., list price $54.95. Glencoe/MacMillan McGraw Hill, April, 1994, 428 pages hardcover, ISBN 0028018427. All the basic principles of transmission and their underlying math. If you didn’t take signals & systems in school, this is your coach in the closet.

“Digital Communications: Fundamentals and Applications” by Bernard Sklar. 771 pp., Prentice Hall, 1988. $74 ISBN# 0-13-211939-0 Excellent in depth treatment of modulation schemes, digital processing theory, noise.

"Wireless Personal Communications Services" by Rajan Kuruppillai. 424 pp., 75 illus., McGraw-Hill # 036077-4, $55 Introduction to major PCS technical standards, system/RF design principles and process, good technical reference

"PCS Network Deployment" by John Tsakalakis. 350 pp, 70 illus., McGraw-Hill #0065342-9, $65 Tops-down view of the startup process in a PCS network. Includes good traffic section.

"The ARRL Handbook for Radio Amateurs (1997)" published by the American Radio Relay League (phone 800-594-0200). 1100+ page softcopy ($44); useful exposure to nuts-and-bolts practical ideas for the RF-unfamiliar. Solid treatment of the practical side of theoretical principles such as Ohm’s law, receiver and transmitter architecture and performance, basic antennas and transmission lines, and modern circuit devices. Covers applicable technologies from HF to high microwaves. If you haven’t had much hands-on experience with real RF hardware, or haven’t had a chance to see how the theory you learned in school fits with modern-day communications equipment, this is valuable exposure to real-world issues. Even includes some spread-spectrum information in case you’re inclined to play and experiment at home. At the very least, this book will make dealing with hardware more comfortable. At best, it may motivate you to dig deeper into theory as you explore why things behave as they do.

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