introduction to 1xrtt

NORTEL NETWORKS CONFIDENTIAL

1xRTT RF Training for US RegionIntroduction to 1xRTT

Rubianto Satrio

Wireless Network Engineering

March 2002

Introduction to 1xRTT - 2NORTEL NETWORKS CONFIDENTIAL

Topics onIntroduction to 1xRTT• Comparison of IS-95 and 1xRTT

– New RCs (3,4,5) to support packet data– New channels: SCH, Reverse Pilot, QPCH– New power control: fast forward pc– Turbo coding– Impacts on Eb/Nt setting– RRM– QoS for packet data

• Details on SCH– Differences between FCH and SCH– SCH allocation method– Soft/softer handoff in SCH


Topics on Introduction to 1xRTT• Details on RRM

– Walsh code management– Traffic power management– Channel element management


Introduction to 1xRTT

• Comparison of IS-95 and 1xRTT– New RCs (3,4,5) to support packet data– New channels: SCH, Reverse Pilot, QPCH– New power control: fast forward pc– Turbo coding– Impacts on Eb/Nt setting– RRM– QoS for packet data

• Details on SCH

• Details on RRM

Scope: MTX10/NBSS10


Radio Configurations (RCs)

• 1xRTT is backward compatible with IS95, allowing for a fully integrated network with enhanced capacity

• Capacity gains attained with new detection, fast forward power control, and coding techniques available with the Radio Configuration (RC) selection during call setup

• 1xRTT Phase 1 incorporates 5 Radio Configurations, referred to as RC1 through RC5



• Walsh Code Length x Symbol Rate = Chip Rate = 1.2288 Mcps

• The higher the data rate (hence the symbol rate), the shorter the Walsh code length

• From now on we will discuss RC3 and RC4 only

RCServices

SupportedRates (Fwd Link)

Encoding Rate

Walsh Code

Length1 Voice 9.6 kbps (RS1/EVRC) 1/2 642 Voice 14.4 kbps (RS2) 1/2 64

3 Voice, Data RS1-based: 9.6 to 153.6 kbps 1/4Variable, max. 64





• Note: Fwd & Rvs FCH Base Rates for a call must match. RCs & SCH rates do not have to match. A combination Fwd EVRC, Rvs B13K is not allowed. If RC4 Fwd is used, then RC3 Rvs must be used. If RC5 Fwd is used, then RC4 Rvs must be used. RC >= 3 must use ESEL & XCEM. B8K RC3 is not supported.

Configuration Fwd FCH Base Rate Rvs FCH Base Rate

RC1 9600 bps (EVRC) 9600 bps (EVRC)

RC2 14400 bps (B13K) 14400 bps (B13K)

RC3 9600 bps (EVRC) 9600 bps (EVRC)

RC4 9600 bps (EVRC) 14400 bps (B13K)

RC5 14400 bps (B13K) Not Applicable (3x)

More details in “1x Carrier Config.”!



• Differences between RC3 and RC4:

• RC3: less power per channel, however, less number of Walsh codes available• RC4: more Walsh codes available, however, more power per channel• Use RC3 in power-limited and low SHO areas, RC4 in Walsh-code-limited

areas• RC4 should not be needed in the early deployment on 1xRTT

RC3 RC4Encoder Rate 1/4 (1 bit in, 4 bits out) 1/2 (1 bit in, 2 bits out)Max. Walsh Code Length 64 128# of Walsh Codes 64 128Symbol Rate Twice of RC4 Half of RC3Eb/Nt Requirement Lower than RC4 Higher than RC3RF Capacity Higher than RC4 Lower than RC3

•Parameter: RC4_Preferred (AdvSct MO)


New Physical Channels

Pilot Channel

Sync Channel

Paging Channel

Quick Paging Channel

Fundamental Channel (FCH)

Supplemental Channel (SCH)

Reverse Pilot Channel

Access Channel

= New channel in 1xRTT


New Physical ChannelsFCH and SCH• Fundamental Channel (FCH) = traffic channel (fwd &

rev) in IS-95– FCH rate = 9.6 kbps– Every active mobile is assigned and maintains a FCH

• Supplemental Channel (SCH) = additional traffic channel (fwd & rev) used to carry packet data– SCH rates = 19.2, 38.4, 76.8, 153.6 kbps (2X, 4X, 8X,

16X)– A mobile is assigned an SCH if the queue size of the

RLP-Q is above a certain threshold

• Voice call: always has one F-FCH and one R-FCH, no SCH• Packet data call: always has one F-FCH and one R-FCH, may have one F-SCH and/or one

R-SCH

More details later!


New Physical ChannelsQPCH• Quick Paging Channel (QPCH) is an signal sent by a base

station to inform mobile stations operating in the slotted mode during the idle state whether to receive the Paging Channel starting in the next Paging Channel slot.

• Its purpose is to provide slotted mode paging operation while conserving battery power on the mobile station

80 mSec

80 mSec

20 mSecSlot of Paging indications

Slot of Paging message directed to mobile

Paging Channel

Quick Paging Channel

1 2 3 4 5 6 7

0 1 2 3 4 5 6

Figure 1. Quick Paging slot timing alignment with the assigned Paging slot.

100 ms

•Parameters: NumofQPCH, QPCH_Rate, QPCH_PowerLevelPage(AdvSct MO)


New Physical ChannelsR-PICH

• Reverse Pilot Channel (R-PICH) is introduced in 1xRTT to facilitate a coherent detection in the reverse link– Transmitted by the mobile using Walsh code

(different from the traffic channel)– Used by BTS to estimate the traffic channel quality

• Coherent detection provides Eb/No performance improvement over the non-coherent scheme– Reverse link Eb/No gain 2.5 dB

320W


New Power Controls

IS-95 1xRTTReverse Link Open Loop Open Loop

Closed/Inner Loop (800 Hz, 1dB step, based on traffic

channel Eb/Nt)

Closed/Inner Loop (800 Hz, 0.5dB step, based on

Reverse Pilot Ec/Io)Outer Loop

(50 Hz, adjust Ew/Nt setpoint)Outer Loop

(50 Hz, adjust Ec/Io setpoint)

Forward LinkTraffic Channel

(50 Hz)Fast Inner Loop

(800 Hz*, 0.25 to 1dB step)Outer Loop

(50 Hz, adjust Eb/Nt setpoint)PC Synchronization

(50 Hz)

* 800 Hz for FCH only, or 400 Hz for FCH and 400 Hz for SCH


Fast Forward Power Control

• Fast forward power control improves link capacity by significantly reducing Rayleigh fading effect– Most effective at slow mobile speed, single multipath, and

small FER target– Gain can reach 4 dB (from simulation)

• Fast Inner Loop: executed at the mobile based on comparison to the current Eb/Nt threshold– If measured Eb/Nt > threshold, then power down (and

vice versa)– Mobile multiplexes PC bits into R-PICH channel– BTS applies PC bit commands for forward traffic channel

correction


Fast Forward Power Control

• In the Outer Loop, mobile adjusts the Eb/Nt setpoint to maintain a given FER– Received frame = erasure increase setpoint by 0.5 dB– Decrease setpoint by 0.125 dB after a certain numbers

of good frames

FFPC Outer Loop(illustration for 5% FER case)

5.000

5.125

5.250

5.375

5.500

1000 1005 1010 1015 1020

Frame no.

Eb/

No

Set

poin

t

Erasure framereceived

•Parameter (SBS MO): TxMinSetPoint, TxMaxSetPoint, TxInitSetPoint for RCxFCHData and RCxSCHData (for different data rates)


New CodingTurbo Coding for SCH

• Turbo Coding:– Combines two convolutional encoder– Perform better in high data rate system with low error

rate requirement– Performance gain is highest at low mobile speeds and

smallest at moderate speeds– Used for SCH (rate 19.2 kbps)

• Average forward Eb/No gain due to Turbo Coding:Data Rate

(kb/s)RC3 RC4

19.2 0.61 dB 0.15 dB38.4 1.02 dB 0.52 dB76.8 1.30 dB 0.86 dB153.6 1.55 dB 1.18 dB

Note: averaged over several mobile speeds, one-path and two-path propagation.


Impacts on Eb/No Setting

• Performance improvements (Eb/No gain) are mainly due:– Forward link: fast fwd power control and Turbo Coding– Reverse link: coherent detection and Turbo Coding

• Reverse Eb/No requirement for different services:Service Type Data Rate

(kb/s)Reverse Eb/No

(dB)IS-95 Voice 9.6 7.00

1xRTT Voice 9.6 4.509.6 4.50

19.2 3.7038.4 3.2576.8 2.75153.6 2.25

1xRTT Data

Notes:• FCH FER = 2%• SCH FER = 5%• For FWA (stationary

terminals), we get an additional 1-2 dB improvement in Eb/No.


Radio Resource Manager

• In 1xRTT, power, Walsh codes, and channel elements have to be allocated for voice and for packet data

• RRM (in BTS) handles the resource allocation for voice vs data– Can be configured independently for each sector of each

carrier– Expressed as a percentage of total resources

• Refers to power and Walsh code space• Does not apply to physical resources (e.g., channel elements)

– Separate thresholds for voice and data– The sum of the two thresholds can exceed 100% to allow

dynamic tradeoff of voice vs. dataMore details later!


QoS for Packet Data

• Quality of Service (QoS) indicates a set of performance attributes associated with a service

• Packet data introduces additional QoS indicators

QoS Metrics Voice Packet DataArea Reliability (%) Area Reliability (%)

RF Blocking (%) RF Blocking (%)Access Failure (%) Access Failure (%)Dropped Call (%) Dropped Call (%)

FER (%) FER (%)Throughput (kbps)Packet Loss (%)Delay/Latency (s)

Jitter (s)

Service Availability Metrics

Other Metrics


Class of Service

• A 1xRTT service provider may offer different CoS (Class of Service) or Class of Users, e.g.:– Gold class: max. data rate = 153.6 kbps,– Sliver class: max. data rate = 76.8 kbps, etc.– Rates are maximum, not guaranteed (non-assured QoS)

• QOSPI parameter:– MTX datafill under CELLFEAT – Used to identify which QoS priority

the subscriber is assigned in terms of maximum data rate.

QOSPI Max. Data Rate0 to 4 19.2 kbps5 to 7 38.4 kbps8 to 10 76.8 kbps

11 to 13 153.6 kbps14 to 15 Reserved



• Comparison of IS-95 and 1xRTT

• Details on SCH– Differences between FCH and SCH– SCH allocation method– Soft/softer handoff in SCH

• Details on RRM

Scope: MTX10/NBSS10


Differences between FCH and SCH

FCH SCHSimilar channel in IS-95 Traffic channel NoneData rate (RC3) 9.6 kbps (fwd & rev) 19.2 to 153.6 kbpsData rate (RC4) 9.6 kbps fwd, 14.4 kbps rev 19.2 to 153.6 kbpsCoding scheme Convolutional Encoder Turbo CodingWalsh code length (RC3) 64 32 to 4Walsh code length (RC4) 128 64 to 8FER target 2% 5%Allocated to a voice user? Always (fwd & rev) NoAllocated to a data user? Always (fwd & rev) If needed (fwd and/or rev)Allocation duration Call duration Allocated in bursts (max 5.12s) ^Maximum allocation per user 1 1Maximum sectors in handoff 6 2*

^ = assuming finite burst* = settable parameter

•Parameter (SBS MO under SCHDurationParameters): Mode_Selection_Index, Minimum_ and Maximum_SCH_Duration_Time, FSCH_ and RSCH_Fixed_SCH_Duration_Time


Differences between FCH and SCHIllustrations of FCH & SCH during a Data Call

SCH 19.2 Kb/s

SCH 38.4 Kb/s SCH 76.8 Kb/s

SCH 153.6 Kb/s

FCH 9.6 Kb/s


Differences between FCH and SCHIllustrations of FCH & SCH during a Data Call

FCH

FCH + SCH


SCH Allocation Method

• Four factors determine whether a mobile has SCH, and what SCH rate it can have (in fwd link):

– RLP-Q queue size. BSC checks for the buffer size every 0.5 s and will request the appropriate SCH rate to BTS.

BTS then will check for its resource availability:– Channel element availability– Walsh code availability– HPA power availabilityIf any of these BTS resources is insufficient to support the

requested rate, the BTS will downgrade the request (go to the lower rate) or deny/block the request.


SCH Allocation Method

BSC checks RLP-Q queue size against threshold values for 2X, 4X, 8X, & 16X

BSC checks RLP-Q queue size against threshold values for 2X, 4X, 8X, & 16X

BSC request SCH burst with certain rate to BTS:• Rate QOSPI setting• SCH power estimated• Sectors indicated

BSC request SCH burst with certain rate to BTS:• Rate QOSPI setting• SCH power estimated• Sectors indicated

BTS checks resources availability:• CE availability• Walsh code availability• HPA power availability

BTS checks resources availability:• CE availability• Walsh code availability• HPA power availability

Request grantedRequest granted

Request downgradedRequest downgraded

Request deniedRequest denied

BTS assigns:• F-SCH rate • F-SCH power• F-SCH Walsh

codeBSC sends:• Eb/Nt offset

estimate

BTS assigns:• F-SCH rate • F-SCH power• F-SCH Walsh

codeBSC sends:• Eb/Nt offset

estimate

F-SCHBurst!


SCH Allocation MethodRequesting SCH Burst

BSC checks RLP-Q against thresholds (L1, L2, L3, L4) and requests SCH burst with certain rate to BTS.Rate QOSPI setting.

•Parameter (SBS MO under RLPParameters):BufferThreshold_192, _384, _768, and _1536.


SCH Allocation MethodSectors to Send SCH Burst

• BSC orders the sectors in the FCH active set by strength (Ec/Io), e.g.:– FCH active set = (A, B, C, D, E, F)– FCH active set ordered by strength = (B, E, A, C, D, F)

• Try to send SCH burst via B and E– Resource allocation starts with strongest sector (B)– If resources are not able to be allocated in neither of the

first two sectors (B, E), then the SCH setup is considered blocked


SCH Allocation MethodSectors to Send SCH Burst

SCH assignment: 496, 500

Ec/Io


SCH Allocation MethodEstimating SCH Power

• When BSC requests SCH burst to BTS, it sends:– Estimated SCH power required for the requested rate– Also the estimated power required for each rate below

the requested rate

• SCH power is estimated from the current FCH power and the differences in data rate, coding, target FER, and maximum SHO links between FCH and SCH


SCH Allocation MethodEstimating SCH Power – Formula

• Estimated required power calculation:

PSCH = PFCH + 10log10(RSCH/RFCH) + TurboCodeCorrection(RSCH)+ ReducedAsetCorrection(NFCH,NSCH)+ FER_Correction(FERSCH, FERFCH) + PowerControlCorrection

Where:PFCH Current power required by the FCHRSCH Data rate of the SCHRFCH Data rate of the FCH (9.6 or 14.4)NSCH Number of legs in the SCH active setNFCH Number of legs in the FCH active setFERFCH Target FER of the FCHFERSCH Target FER of the SCH



• 10log10(RSCH/RFCH): The required power is approximately proportional to the channel data rate, when convolutional codes are used

• TurboCodeCorrection(RSCH): Accounts for the gain of turbo codes over convolutional codes. This is a lookup table:

• ReducedAsetCorrection(NFCH,NSCH): A lookup table to account for increase in power required from a reduced SCH active set.

Rate (kb/s) RC3 RC419.2 -0.6 -0.138.4 -1.0 -0.576.8 -1.2 -0.8

153.6 -1.4 -1.1

NFCH \ NSCH 1 2 3 4 5 61 0.0 - - - - -2 3.0 0.0 - - - -3 5.0 1.8 0.0 - - -4 5.0 1.8 0.0 0.0 - -5 5.0 1.8 0.0 0.0 0.0 -6 5.0 1.8 0.0 0.0 0.0 0.0



• FER_Correction(FERSCH, FERFCH): Accounts for the decrease in required power that results from increasing the FER target. We assume an average of 1 dB decrease in power per doubling of FER.

• PowerControlCorrection: A constant that accounts for the reduction in required transmit power that is a result of improved Eb/Nt estimation at the mobile of an SCH over that of an FCH. The term is expected to be about –1.0 dB.

• Summary (for RC3):Data Rate

(kbps)

Rate Correction

Turbo Code Correction

ReducedASet Correction

FER Correction

Power Control

Correction

Total Correction

9.6 0.0 0.0 0.0 0.0 0.0 0.019.2 3.0 -0.6 1.8 -1.3 -1.0 1.938.4 6.0 -1.0 1.8 -1.3 -1.0 4.576.8 9.0 -1.2 1.8 -1.3 -1.0 7.3

153.6 12.0 -1.4 1.8 -1.3 -1.0 10.1


SCH Soft/Softer Handoff

• The max. number of SHO links for SCH is set using MaxFwdSCHSHOLinks (SBS MO)– Range 1-3. Recommended = 2.

• Advantages of SCH reduced active set:– Walsh code, RF power, and channel element

requirements on the adjacent sector/BTS is reduced– Faster SCH setup time

• Disadvantages:– May not have the strongest PN in SCH active set during

the SCH burst interference FER problem– Power required from the serving sector(s) will be greater


SCH SHO AlgorithmExample

Say FCH ASet is {P1, P2, P3} (in that order of strength)

Then SCH ASet is {P1,P2} (assuming Max SCH links =2)

Now say a PSMM comes in resulting in a FCH Aset of {P1, P4, P2} (in that order of strength)

Then the SCH ASet stays {P1,P2} although P4 is stronger that P2.

Now say a PSMM had come in resulting in a FCH ASet of {P1, P3, P4} (in that order of strength)

Then the SCH Aset would have become {P1, P3} and consequently the burst would have been released.



• Comparison of IS-95 and 1xRTT

• Details on SCH

• Details on RRM– Walsh code management– Traffic power management– Channel element management

Scope: MTX10/NBSS10


Radio Resource Manager (RRM)

• BTS RRM manages three types of radio resources:– Walsh codes (WC)– Forward traffic power– Channel elements (CE)

• These resource pools are checked when– A new call (voice or data) request is received– A new SCH request is received

• The resource pools are updated when:– A request is granted– A call is terminated– An SCH is torn down


Radio Resource Manager (RRM)Walsh Code Management

• Maximum number of Walsh codes:– RC3 and RC5: 64– RC4: 128

• Walsh code of length N (N>1) is generated from Walsh code of length N/2

• If a Walsh code is used then all of its children cannot be used– Example: if Walsh code 0011 is used, then Walsh codes

0011xxxxxx … cannot be used



RC4 FCH

RC3 FCH

16X SCH

A mobile in N-way SHO will need the same number of Walsh codes from the N sectors it is connected with.

2X SCH

4X SCH

8X SCH

2X SCH

4X SCH

8X SCH

16X SCH

RC4

RC3



What is going on?

Pilot &Paging Sync FCH

SCH 16X



What is going on?

x x xx x x x x x

x xx x x x x

z z z z z zz

z

x = SCH 16X

z = SCH 8X

ff

f = FCH



0

00

01

0000

0011

0101

0110

00000000

00001111

00110011

00111100

01010101

01011010

01100110

01101001

80W

84W8

2W8

6W

81W

85W8

3W

87W

40W

42W

41W

43W

160W

168W

Assuming there is no other (power, channel element) limitations, how many simultaneous 16X calls can RC3 support?


Radio Resource Manager (RRM)Forward Traffic Power Management

• MaxVoiceResources (Tv): upper limit on the % of BTS resources used on voice calls– Voice calls consist of 2G voice, 2G circuit-switched data,

and 3G voice calls on FCH

• MaxDataResources (Td): upper limit on the % of BTS resources used on 3G data calls– These data calls could exist on FCH or SCH

• Both are expressed as % of total traffic power: (Power at Call Blocking Threshold – Overhead Power)• BTS resources = forward link power and Walsh codes



Max

Voi

ceR

esou

rces

Max

Dat

aRes

ourc

es

Overhead Power

Handoff Power

Max

. Dat

a P

ower

Min. GuaranteedVoice Power

Min. GuaranteedData Power

DynamicallyAllocated Power

Max

. Voi

ce P

ower

0 %

20 %

20 %

40 %

0 %

100 %

80 %

60 %

100 %

80 %

60 %

40 %

Max

. Tra

ffic

Pow

er

Max

Voi

ceR

esou

rces

Max

Dat

aRes

ourc

es

Overhead Power

Handoff Power

Max

. Dat

a P

ower

Min. GuaranteedVoice Power

Min. GuaranteedData Power

DynamicallyAllocated Power

Max

. Voi

ce P

ower

0 %

20 %

20 %

40 %

0 %

100 %

80 %

60 %

100 %

80 %

60 %

40 %

Max

. Tra

ffic

Pow

er



• Four Different RRM Modes of Operation– Operating Mode 1: Static Power Partitioning

• Tv + Td = 100%– Operating Mode 2: Dynamic Power Partitioning

• Tv + Td > 100%, Td and Tv < 100%– Operating Mode 3: Fully Dynamic Power Partitioning

• Tv = Td = 100%– Operating Mode 4: Optimum Capacity and Throughput with

Minimum Guaranteed Voice Performance (Dynamic Power Partitioning)

• Tv = 100%, Td = MAX_AVAILABLE_DATA_POWER (e.g., 50%)



• MaxDataFchResources: – Defines the % of MaxDataResources that can be

allocated for FCHs, expressed as % of the current total data resources

– Control the number of 3G data resources on FCHs vs. those on SCHs

– Allows the operator to tune the system between having fewer users/sector at higher throughput and having more users/sector at lower throughput



Max

Voi

ceR

esou

rces

Max

Dat

aRes

ourc

es

Overhead Power

Handoff Power

Carried Voice Traffic Power

SCH Data Power Available

FCH Data Power Avail.

100% Voice Blocking

SCH Blockingor downgrade

Data Call Blocking

UnutilizedPower

UnutilizedPower



Example of BSM Picture


Radio Resource Manager (RRM)Channel Element Management

Channel Type RC Rate (kbps) Forward Resources

Reverse Resources

Forward overhead channel Pilot

N/A N/A 1 0

Forward overhead channel Synch

N/A N/A 1 0

Forward overhead channel Paging

N/A N/A 1 0

Forward overhead channel Quick Paging

N/A N/A 1 0

Total Forward Overhead Channels

4 0

Reverse overhead channel Access Channel

N/A N/A 0 1

Total Reverse Overhead Channels

0 1

FCH 3,4,5 9.6 or 14.4 (kbps) 1 1 3 N*9.6

(N= 2,4,8,16) N

1 (due to R-PICH) F-SCH

4 N*9.6 (N= 2,4,8,16)

N/2 1 (due to R-PICH)

R-SCH 3 N*9.6 (N= 2,4,8,16)

0 N/2



• Overhead Channel CE usage:– Forward = 4 CEs per sector (1 for Pilot, 1 for Paging, 1

for Sync and 1 for Quick Paging)– Reverse: 1 CE per sector for access channel

• Traffic Channel usage:– For forward link RC3, SCH of rate N*9.6 kbps will require

N CEs per link– For forward link RC4 and for reverse link RC3, SCH with

rate N*9.6 only requires half as much CE, = N/2



• Notes:– A mobile in K-way soft handoff will need the same

number of forward and reverse CEs from each of the K BTSs (e.g., 2-way soft handoff need twice as many CEs). However, softer handoffs do not need additional CE.

– Even if there is no reverse SCH, for each forward SCH, there will be one CE needed to track the reverse pilot.

Thank You!

introduction to 1xrtt

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