1201L5

Course 1201 CDMA Technology and Standards

Issue 01.00

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Lesson Lesson 55Registration, Power Control, and Registration, Power Control, and HandoffsHandoffs


Issue 01.00 - 2

Lesson Objectives

• Identify TMSI zones and TMSI codes

• Describe roaming and how it relates to the HLR and VLR

• Describe forms of CDMA registration and related registration messages

• Identify the types of power control and related power control messages

• Describe the role of handoffs

• Describe pilot sets as they relate to initialization and maintenance of a call

• Describe handoffs- related messages


Issue 01.00


Section Section 11

RegistrationRegistration


Issue 01.00 - 4

Systems and Networks

SID = 7

SID = 3

SID = 9

SID = 4

SID = 1NID = 1

SID = 1NID = 2

SID = 1NID = 3


Issue 01.00 - 5

TMSI zones and TMSI codes

TMSI_ZONE = 527 (octal)



TMSI_CODE = 222 (octal)




Issue 01.00 - 6

Roaming

• A mobile station may be in any of the following roaming states:— Home: mobile station is at its home location (not roaming)— NID roaming: mobile station is within a foreign NID but in the home SID— SID roaming: mobile station is within a foreign SID

• A mobile station maintains a list of one or more “home pairs”— These are SID/NID combinations defining the mobile station’s home location— They are stored in semi-permanent memory

• The identity of current SID/NID is contained in the System Parameters Message (sent on the Paging Channel)

HomeSID/NID List

(2, 3)(2, 0)(3, 1)

SID = 2SID = 4

SID Roaming

NID = 7 NID =3NID = 0

NID Roaming Not RoamingRoaming Status


Issue 01.00 - 7


Issue 01.00 - 8

HLR & VLR

• Contains permanent subscriber data

• Contains dynamic information

• Supports call routing

• Allows querying by the switch regardless of mobile station’s location

• Contains temporary subscriber data

• Stores a subset of HLR data relating to the mobile stations that are currently in the VLR’s service area

HLR VLR


Issue 01.00 - 9

CDMA Registration• Registration is the means by which a mobile station notifies the cellular

system of its location, status, identification, and other characteristics• Balance is required between paging and registration

— Infrequent registration results in a high rate of paging

— Frequent registration places a high load on access channels

• Proper system design allows a base station to efficiently page the mobile station when establishing a mobile-terminated call

• Registration also provides— The mobile station’s SLOT_CYCLE_INDEX and SLOTTED_MODE

— The mobile station class mark and protocol revision number so that the base station will know the mobile station’s capabilities

• Two types of mobile registration— Non-Autonomous: explicitly requested by the base station, or implied

based on other types of messages received by the mobile station

— Autonomous: triggered by some event other than the reception of an explicit or implicit request from the base station


Issue 01.00 - 10

Forms of CDMA Registration

• Power-up registration

• Power-down registration

• Timer-based registration

• Distance-based registration

• Zone-based registration

• Parameter-change registration

• Implicit registration

• Ordered registration

• Traffic channel registration

AutonomousRegistration

Registration Types NOTSupported by Nortel

Non-AutonomousRegistration

All types of registration can be enabled or disabled by means of the System Parameters Message


Issue 01.00 - 11

Registration Message (ACH)

REG_TYPE 4

SLOT_CYCLE_INDEX 3

MOB_P_REV 8

EXT_SCM 1

RESERVED 1

SLOTTED_MODE 1

RESERVED 5

MOB_TERM 1

RESERVED 6

MSG_TYPE (‘00000001’)

ACK_SEQ

8

3

MSG_SEQ 3

ACK_REQ 1

VALID_ACK 1

ACK_TYPE 3

MSID_TYPE 3

MSID_LEN 4

MSID 8 X MSID_LEN

AUTH_MODE 2

AUTHR 0 or 18

RANDC 0 or 8

COUNT 0 or 6

Field Length (bits)


Issue 01.00 - 12

Mobile Station Registered Message (FTC)

BASE_LONG 23

REG_DIST 11

RESERVED 4

BASE_LAT 22

MSG_TYPE (‘00001111’)

ACK_SEQ

8

3

MSG_SEQ 3

ACK_REQ 1

ENCRYPTION 2

SID 15

NID 16

REG_ZONE 12

TOTAL_ZONES 3

ZONE_TIMER 3

MULTI_SIDS 1

MULTI_NIDS 1

Field Length (bits)


Issue 01.00 - 13

System Parameters Message (PCH)

MSG_TYPE (‘00000001’)

PILOT_PN

8

9

CONFIG_MSG_SEQ 6

SID 15

NID 16

REG_ZONE 12

TOTAL_ZONES 3

ZONE_TIMER 3

MULT_SIDS 1

MULT_NIDS 1

BASE_ID 16

BASE_CLASS 4

PAGE_CHAN 3

MAX_SLOT_CYCLE_INDEX 3

HOME_REG

FOR_SID_REG

1

1

FOR_NID_REG 1

POWER_UP_REG 1

POWER_DOWN_REG 1

PARAMETER_REG 1

REG_PRD 7

BASE_LAT 22

BASE_LONG 23

REG_DIST 11

SRCH_WIN_A 4

SRCH_WIN_N 4

SRCH_WIN_R 4

NGHBR_MAX_AGE 4

PWR_REP_THRESH

PWR_REP_FRAMES

5

4

PWR_THRESH_ENABLE 1

PWR_PERIOD_ENABLE 1

PWR_REP_DELAY 5

RESCAN 1

T_ADD 6

T_DROP 6

T_COMP 4

T_TDROP 4

EXT_SYS_PARAMETER 1

EXT_NGHBR_LIST 1

GLOBAL_REDIRECT 1

RESERVED 1

FieldLength(bits)


Issue 01.00 - 14

Access Parameters Message (PCH)

MSG_TYPE (‘00000010’)

PILOT_PN

ACC_MSG_SEQ

ACC_CHAN

NOM_PWR

INIT_PWR

PWR_STEP

8

9

6

5

4

5

3

MSG_PSIST

REG_PSIST

PROBE_PN_RAN

ACC_TMO

PROBE_BKOFF

BKOFF

MAX_REQ_SEQ

MAX_RSP_SEQ

AUTH

RAND

NOM_PWR_EXT

RESERVED

NUM_STEP

3

3

4

4

4

4

4

4

2

0 or 32

1

6

4

MAX_CAP_SZ

PAM_SZ

PSIST(0-9)

PSIST(10)

PSIST(11)

PSIST(12)

PSIST(13)

3

4

6

3

3

3

3

FieldLength(bits)

PSIST(14) 3

PSIST(15) 3


Issue 01.00


Section Section 22

Power ControlPower Control


Issue 01.00 - 16

CDMA Power Control

• CDMA is an interference-limited system based on the number of users

• Unlike AMPS/TDMA, CDMA has a soft capacity limit— Each user is a noise source on the shared channel— The noise contributed by users is cumulative— This creates a practical limit to how many users a system will sustain

• Precise power control of the mobile stations is critical if we want to— Maximize system capacity— Increase battery life of the mobile stations

• The goal is to keep each mobile station at the absolute minimum power level necessary to ensure acceptable service quality— Ideally the power received at the base station from each mobile station

should be the same (minimum signal to interference)— Mobile stations which transmit excessive power increase interference to

other mobile stations


Issue 01.00 - 17

Reverse Open Loop Power Control

• The mobile station makes a coarse initial estimation of the required transmit power, based upon the total received power.

• Problems with Reverse Open Loop Power Control: — Assumes same exact path loss in both directions; therefore, cannot account for

asymmetrical path loss— Estimates are based on total power received; therefore the power received from

other cell sites by mobile station introduces inaccuracies

Mobile BTS

Reverse Open LoopPower Control


Issue 01.00 - 18

Reverse Closed Loop Power Control

• Compensates for asymmetries between the forward and reverse paths

• Consists of power up (0) and power down (1) commands sent to the mobile stations, based upon their signal strength, measured at the Base Station and compared to a specified threshold (setpoint)

• Each command requests a 1dB increment or decrement of the mobile station transmit power

• Transmitted 800 times per second, always at full power

• Allows to compensate for the effects of fast fading

Mobile BTS

Signal StrengthMeasurement

Setpoint

or

Reverse Closed LoopPower Control


Issue 01.00 - 19

Reverse Closed Loop Output Power Correction

mean output power (dBm) = - mean power input (dBm)+ K+ NOM_PWR - 16 x NOM_PWR_EXT+ INIT_PWR+ the sum of all access probe corrections (dB)+ the sum of all closed loop power control

corrections (dB)

Once the first power control bit has been received after initializing Reverse Traffic Channel transmissions, the mean output power is defined as follows:

The “turn around constant” K is calculated assuminga nominal cell Effective Radiation Power (ERP) of 5 W

and a nominal cell loading of 50%.

Its value is -73 for cellular systems and -76 for PCS systems


Issue 01.00 - 20

Access Parameters Message (PCH)Length(bits)

MSG_TYPE (‘00000010’)

PILOT_PN

ACC_MSG_SEQ

ACC_CHAN

NOM_PWR

INIT_PWR

PWR_STEP

PSIST(14)

8

9

6

5

4

5

3

3

PSIST(15)

MSG_PSIST

REG_PSIST

PROBE_PN_RAN

ACC_TMO

PROBE_BKOFF

BKOFF

MAX_REQ_SEQ

MAX_RSP_SEQ

AUTH

RAND

NOM_PWR_EXT

RESERVED

NUM_STEP

3

3

3

4

4

4

4

4

4

2

0 or 32

1

6

4

MAX_CAP_SZ

PAM_SZ

PSIST(0-9)

PSIST(10)

PSIST(11)

PSIST(12)

PSIST(13)

3

4

6

3

3

3

3

Field


Issue 01.00 - 21

Reverse Outer Loop Power Control

• Not part of IS-95A or J-STD-008.

• Most gradual form of reverse link error control— Setpoint is varied according to the FER on the Reverse Traffic Channel

(determined at the Base Station Controller)— Sampled at a rate of 50 frames per second (20 ms/frame)— Setpoint adjusted every 1-2 seconds

FER

Mobile BTS BSC

Reverse Outer Loop Power

Control


Setpoint

or



Issue 01.00 - 22

Forward Traffic Channel Power Control

• The base station slowly decreases power to each mobile station

• As the FER (determined at the mobile station) increases, the mobile station “requests” a Forward Traffic Channel power increase

FER

Mobile BTS BSC

Adjust Fwd.power

Forward Link Power Control


Issue 01.00 - 23


MSG_TYPE (‘00000001’)

PILOT_PN

8

9

CONFIG_MSG_SEQ 6

SID 15

NID 16

REG_ZONE 12

TOTAL_ZONES 3

ZONE_TIMER 3

MULT_SIDS 1

MULT_NIDS 1

BASE_ID 16

BASE_CLASS 4

PAGE_CHAN 3


HOME_REG

FOR_SID_REG

1

1

FOR_NID_REG 1

POWER_UP_REG 1

POWER_DOWN_REG 1

PARAMETER_REG 1

REG_PRD 7

BASE_LAT 22

BASE_LONG 23

REG_DIST 11

SRCH_WIN_A 4

SRCH_WIN_N 4

SRCH_WIN_R 4

NGHBR_MAX_AGE 4

PWR_REP_THRESH

PWR_REP_FRAMES

5

4

PWR_THRESH_ENABLE 1

PWR_PERIOD_ENABLE 1

PWR_REP_DELAY 5

RESCAN 1

T_ADD 6

T_DROP 6

T_COMP 4

T_TDROP 4

EXT_SYS_PARAMETER 1

EXT_NGHBR_LIST 1

GLOBAL_REDIRECT 1

RESERVED 1

bad

total


Issue 01.00 - 24

Power Control Parameters Message (FTC)

MSG_TYPE (‘00001010’)

ACK_SEQ

MSG_SEQ

ACK_REQ

ENCRYPTION

PWR_REP_THRESH

PWR_REP_FRAMES

PWR_THRESH_ENABLE

PWR_PERIOD_ENABLE

PWR_REP_DELAY

RESERVED

8

3

3

1

2

5

4

1

1

5

7

Field Length (bits)


Issue 01.00 - 25

Power Measurement Report Message (RTC)

MSG_TYPE (‘00000110’)

ACK_SEQ

MSG_SEQ

ACK_REQ

ENCRYPTION

ERRORS_DETECTED

POWER_MEAS_FRAMES

LAST_HDM_SEQ

NUM_PILOTS

PILOT_STRENGTH

RESERVED

8

3

3

1

2

5

10

2

4

6

0-7 (as needed)

NUM_PILOTS occurrences of the following field:

Field Length (bits)

HANDOFF-relatedfields


Issue 01.00 - 26

Summary of All Power Control Mechanisms

• All types of power control work together to minimize transmit power

FER FER

Mobile BTS BSC


Setpoint

or

Adjust Fwd.power

Reverse Outer Loop Power

Control


Forward Link Power Control

Reverse Open LoopPower Control


Issue 01.00


Section Section 33

CDMA HandoffsCDMA Handoffs


Issue 01.00 - 28

CDMA Handoffs

• Handoff is the process by which a mobile station maintains communications with the Mobile Telephone Switching Office (MTSO), when traveling from the coverage area of one base station to that of another

• Handoffs keep the call established during the following conditions:— the subscriber crosses the boundaries of a cell— the subscriber experiences noise or other interference above a specified

threshold— a base station component experiences an out-of-service condition

during a call

• Handoffs consist of the following phases:— Handoff initiation— Target selection— Handoff completion


Issue 01.00 - 29

Pilot Sets

• Pilot sets:— Active Set:- Pilots associated with the forward traffic channels assigned

to the mobile station (max 6 pilots)— Candidate Set - Pilots not currently in the Active Set but received by the

mobile station with sufficient strength to indicate that the corresponding Traffic Channels can be successfully demodulated (max 5 pilots)

— Neighbor Set - Pilots not currently on the Active or Candidate Sets that are likely handoff candidates (at least 20 pilots)

— Remaining Set - All other possible pilots in the current system on the current CDMA frequency assignment

• All pilots in a pilot set have the same frequency assignment

• These sets can be updated during handoff by the base station

Pilot Sets

1. Active2. Candidate3. Neighbor4. Remaining


Issue 01.00 - 30

Pilot Set Initialization(While in the Idle or in an Active Call)

Candidate

Remaining

Active

Neighbor

Pilot whose Paging Channel is being monitored or

associated with the assigned Forward Traffic Channel

Pilots specified in the most recently received Extended

Neighbor List Message(AGE set at NGHBR_MAX_AGE)

Empty

Any other possible pilotin the system


Issue 01.00 - 31

Pilot Set Maintenance(While in an Active Call)

Candidate

Remaining

Active

Neighbor

Pilots listed the most recently received Extended

Handoff Direction Msg

Pilots specified in the most recently received Neighbor

List Update Message (or whose AGE is still less than NGHBR_MAX_AGE)

Pilots whose strength exceeds T_ADD

Any other possible pilotin the system


Issue 01.00 - 32

Pilot Strength Measurement Message (RTC)

• The Pilot Strength Measurement Message (PSMM) is used by the mobile station to direct the Base Station Controller (BSC) in the handoff process.

• With this message the mobile station reports the strength of the pilots associated with forward traffic channels currently being demodulated (and whether it would like to continue to receive traffic from them), as well as pilots from the neighbor and remaining list, which are being received with sufficient strength so that traffic could be demodulated from them successfully.

• In the drawing above: — The mobile station is demodulating traffic and deriving its time reference from cell A.— The mobile station is still demodulating traffic from cell B (It is in soft handoff with cell

B.), but the pilot from cell B has become too weak to be useful.— the pilot from cell C has become sufficiently strong, and the mobile station would like

to start receiving traffic from this cell.• The mobile station sends a PSMM requesting update of its Active Pilot set.

PSMM

A

C

B


Issue 01.00 - 33

Extended Handoff Direction Message (FTC)

• The Extended Handoff Direction Message (EHODM) is used by the Base Station Controller (BSC) to tell the mobile station on which base stations the BSC has allocated traffic channels for that user.

• In the drawing above:— Provided that there are sufficient resources available, the BSC allocates a traffic channel for

the mobile station on cell C, and starts sending traffic to the mobile station on it.— Mixed with the traffic, the BSC sends an EHODM for the mobile station with the new list of

authorized pilots for the Active Set (cells A and C).— The mobile station updates its Active Set ands sends a HCM to the base station.— The mobile station continues demodulating traffic & deriving time reference from cell A.— The mobile station stops demodulating traffic from cell B.— The mobile station begins demodulating traffic from cell C using the Walsh Code indicated in

the EHODM.— The BCS sends a Neighbor List Update message to the mobile station.— The mobile station updates its Neighbor Set.

A

C

B

EHODM

( EHODM )


Issue 01.00 - 34

Pilot Search Windows

• A search window is a range of PN offsets (in chips) where the mobile station searches for usable multipath components of the pilots in a set

— Usable means that multipath components can be used for demodulation of an associated traffic channel

Search Window for pilots in the Active and Candidate Set:

Search Window for pilots in the Neighbor Set:

Search Window for pilots in the Remaining Set:

Earliest arriving usable multipath component of the pilot

pilot PN offset

pilot PN offset

SRCH_WIN_N

SRCH_WIN_A

SRCH_WIN_R


Issue 01.00 - 35

Soft Handoff Signaling

• T_ADD: pilot detection threshold (Typically 28 = -14 dB)

• T_DROP: pilot drop threshold (Typically 32 = -16 dB)

• T_TDROP: drop timer value (Typically 3 = 4 sec)— Prevents unnecessary transmissions of PSMM when a mobile station experiences

a fade

PilotStrength

Pilot Strengthexceeds T_ADD

EHODM received, Pilot Dropped into Neighbor Set,

HOC message sent,NLU message received

Time

Pilot strength drops below T_DROP,Drop Timer started

T_TDROP

T_ADD

T_DROP

EHODM received, Pilot Added to Active Set,

HOC message sent,NLU message received

N C NA(1)(2) (3) (4) (5)(6) (7)

Drop Timer expires

PSMM sent (request to add) , Pilot added to Candidate Set

PSMM Sent (request to remove)


Issue 01.00 - 36

Active versus Candidate SetComparison Threshold

Candidate Set: P0 – Active Set: P1 and P2

t0 – Pilot Strength Measurement Message sent, P0 > T_ADD

t1 – Pilot Strength Measurement Message sent, P0 > P1 + T_COMP x 0.5 dB

t2 – Pilot Strength Measurement Message sent, P0 > P2 + T_COMP x 0.5 dB

(Typically 1 = 0.5 dB)

Pilot P0

Pilot P2

Pilot P1

T_ADD

t0 t1 t2

PilotStrength

(C / I)

Time

T_COMP x 0.5 dB

T_COMP x 0.5 dB


Issue 01.00 - 37


MSG_TYPE (‘00000001’)

PILOT_PN

8

9

CONFIG_MSG_SEQ 6

SID 15

NID 16

REG_ZONE 12

TOTAL_ZONES 3

ZONE_TIMER 3

MULT_SIDS 1

MULT_NIDS 1

BASE_ID 16

BASE_CLASS 4

PAGE_CHAN 3


HOME_REG

FOR_SID_REG

1

1

FOR_NID_REG 1

POWER_UP_REG 1

POWER_DOWN_REG 1

PARAMETER_REG 1

REG_PRD 7

BASE_LAT 22

BASE_LONG 23

REG_DIST 11

SRCH_WIN_A 4

SRCH_WIN_N 4

SRCH_WIN_R 4

NGHBR_MAX_AGE 4

PWR_REP_THRESH

PWR_REP_FRAMES

5

4

PWR_THRESH_ENABLE 1

PWR_PERIOD_ENABLE 1

PWR_REP_DELAY 5

RESCAN 1

T_ADD 6

T_DROP 6

T_COMP 4

T_TDROP 4

EXT_SYS_PARAMETER 1

EXT_NGHBR_LIST 1

GLOBAL_REDIRECT 1

RESERVED 1

FieldLength(bits)


Issue 01.00 - 38

In-Traffic System Parameters Message (FTC)

SRCH_WIN_A 4

SRCH_WIN_N 4

SRCH_WIN_R 4

NGHBR_MAX_AGE 4

T_ADD 6

T_DROP 6

T_COMP 4

T_TDROP 4

RESERVED 4

MSG_TYPE (‘00000111’)

ACK_SEQ

8

3

MSG_SEQ 3

ACK_REQ 1

ENCRYPTION 2

SID 15

NID 16

Field Length (bits)


Issue 01.00 - 39

Pilot Strength Measurement Message (RTC)

MSG_TYPE (‘00000101’)

Zero or more occurrences of the following record:

Field Length (bits)

ACK_SEQ

MSG_SEQ

ACK_REQ

ENCRYPTION

REF_PN

PILOT_STRENGTH

KEEP

PILOT_PN_PHASE

PILOT_STRENGTH

KEEP

RESERVED

8

3

3

1

2

9

6

1

15

6

1

0 - 7 (as needed)

Pilot from which the mobile station derives its time reference

All pilots in the Active and Candidate Sets


Issue 01.00 - 40

Extended Handoff Direction Message (FTC)

MSG_TYPE(‘00010001’) 8

T_COMP 0 or 4

BAND_CLASS 0 or 5

ACK_SEQ 3

T_TDROP 0 or 4

CDMA_FREQ 0 or 11

MSG_SEQ 3

HARD_INCLUDED 1

ADD_LENGTH 3

ACK_REQ 1

FRAME_OFFSET 0 or 4

Additional fields 8 x ADD_LENGTH

ENCRYPTION 2

PRIVATE_LCM 0 or 1USE_TIME 1

RESET_L2 0 or 1

PILOT_PN 9

ACTION_TIME 6

RESET_FPC 0 or 1

PWR_COMB_IND 1

HDM_SEQ 2

RESERVED 0 or 1

CODE_CHAN 8

SEARCH_INCLUDED 1

ENCRYPT_MODE 0 or 2SRCH_WIN_A 0 or 4

NOM_PWR_EXT 0 or 1

RESERVED 0 - 7 (as needed)

T_ADD 0 or 6

NUM_PREAMBLE 0 or 3

NOM_PWR 0 or 4T_DROP 0 or 6

Field Length (bits)

One occurrence of the following record for each member of thenew Active Set:


Issue 01.00 - 41

Handoff Completion Message (RTC)

MSG_TYPE (‘00001010’) 8

ACK_SEQ 3

MSG_SEQ 3

ACK_REQ 1

ENCRYPTION 2

LAST_HDM_SEQ 2

PILOT_PN 9

RESERVED 0-7 (as needed)

One occurrence of the following fieldfor each member of the new Active Set:

Field Length (bits)


Issue 01.00 - 42

Neighbor List Update Message (FTC)

RESERVED 0 – 7 (as needed)

MSG_TYPE (‘00001000’)

ACK_SEQ

8

3

MSG_SEQ 3

ACK_REQ 1

ENCRYPTION 2

Field

Length (bits)

One occurrence of the following fieldfor each pilot in the composite Neighbor Set:

PILOT_INC 4

NGHBR_PN 9


Issue 01.00 - 43

Power Measurement Report Message (RTC)

MSG_TYPE (‘00000110’)

ACK_SEQ

MSG_SEQ

ACK_REQ

ENCRYPTION

ERRORS_DETECTED

POWER_MEAS_FRAMES

LAST_HDM_SEQ

NUM_PILOTS

PILOT_STRENGTH

RESERVED

8

3

3

1

2

5

10

2

4

6

0-7 (as needed)

NUM_PILOTS occurrences of the following field:

Field Length (bits)

Fields used to report the number of frames

received by the mobile station (bad

and total)

Fields used to report the strength of all the pilots in the current

Active Set

Documents

1201L5