01 Mn1789eu11mn 0002 Channel Configuration

8/3/2019 01 Mn1789eu11mn 0002 Channel Configuration

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Channel configuration and allocation strategy Siemens

MN1789EU11MN_0002 © 2005 Siemens AG

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Contents

1 Channel configuration overview 3

1.1 Control channel configuration 15

1.2 Dedicated channel 16

1.3 Smooth Channel Modification 18

1.4 Random access channel 23

1.5 Paging / access grant and notification channel 30

1.6 CCCH load 34

1.7 Additional ASCI service related parameters 38

2 Extended channel mode 43

3 Adaptive Multirate AMR 47 4 Channel allocation strategy 61

4.1 Basic 62

4.2 Multi Service Layer Support 64

4.3 Database parameters 69

5 Exercises 71

6 Solutions 81

Channel configuration and allocation

strategy



Siemens Channel configuration and allocation strategy

MN1789EU11MN_0002

© 2005 Siemens AG

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1 Channel configuration overview




MN1789EU11MN_0002

© 2005 Siemens AG

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On the radio interface Um two subbands for the BTS-MS duplex connection arespecified:

Uplink UL MS-BTS

824 - 849 MHz GSM850

890 - 915 MHz P-GSM900 (primary band)

880 - 915 MHz E-GSM900 (extended band)

1710 - 1785 MHz DCS1800

876 - 880 MHz GSM-R

1850 - 1910 MHz PCS1900

Downlink DL BTS-MS

869 - 894 MHz GSM850

935 - 960 MHz P-GSM900 (primary band)

925 - 960 MHz E-GSM900 (extended band)

1805 - 1880 MHz DCS1800

921 - 925 MHz GSM-R

1930 - 1990 MHz PCS1900

The radio frequency channel spacing in 200 kHz, allowing 124 RFC in P-GSM, 174RFC in E-GSM, 374 in DCS, 20 RFC in GSM-R and 299 in PCS1900.

Within the database or within the protocol messages a carrier frequency ischaracterized by its absolute radio frequency channel number (ARFCN).

Using the abbreviation n = ARFCN, there is the following relation between ARFCNand the frequency in MHz in the uplink Fu [MHz] and the downlink Fd [MHz].

GSM850 Fu(n) = 824.2 + 0.2 (n – 128) 128 < n < 251 Fd(n) = Fu(n) + 45

P-GSM900 Fu(n) = 890 + 0.2 n 1 < n < 124 Fd(n) = Fu(n) + 45

E-GSM 960 Fu(n) = 890 + 0.2 n

Fu(n) = 890 + 0.2 x (n -1024)

0< n < 124

975 < n < 1023

Fd(n) = Fu(n) + 45

DCS1800 Fu(n) = 1710.2 + 0.2 x (n -512) 512 < n < 885 Fd(n) = Fu(n) + 95

GSM-R Fu(n) = 876.2 + 0.2 x (n -955) 955 < n < 974 Fd(n) = Fu(n) + 45

PCS1900 Fu(n) = 1850.2 + 0.2 x (n -512) 512 < n < 810 Fd(n) = Fu(n) + 80





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25 (35) MHz75 MHz

UPLINK (UL)

915 Mhz1785 MHz

(880) 890 Mhz1710 MHz

Transmit band of themobile station

C124

(174)

374

C3

C2

C1

200 kHz

DOWNLINK (DL)

GSM 900

DCS 1800

960 Mhz1880 MHz

01...............124512...............885 975....1024

ARFCN(Absolute RF channel number)

C = radio frequency channel (RFC)

Guard bandnot used

(925) 935 Mhz1805 MHz

Transmit band of the basestation

C124’

(174’)

374

C3’

C2’

C1’

25 (35) MHz75 MHz

Duplex Distance 45 MHz resp. 95 MHz

E-GSM900

GSM900DCS1800

Fig. 1 Radio frequency channels RFC on Um




MN1789EU11MN_0002

© 2005 Siemens AG

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Each RFC offers 8 physical channels a time division multiplex access TDMA.

The physical channels are subdivided into logical channels, divided in traffic channelsand control channels according GSM 04.03.

200 kHzTime

0

43

21

07

65

432

1

4.615 msec

= 8 • 577 µs

Fig. 2 Radio frequency channels RFC on Um





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Speech Channels

(Full/Half)

Data

Channels

(Data Rate)

Control Channels

CCH

Traffic Channels TCH

Logical Channels

Broadcast Control

Channel BCCH

Dedicated Control

Channel DCCH

Common Control

Channel CCCH

Fig. 3 Logical channel types




MN1789EU11MN_0002

© 2005 Siemens AG

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Broadcast Control

Channel BCCH

Cell Broadcast

Channel CBCH

Synchronization

Channel SCH

Frequency

Correction Channel

FCCH

Broadcast Control

Channels BCCH

system information:

cell identifier, cell parameter, channel

configuration, cell frequencies,

broadcast frequencies of neighbour cells

broadcast of short messages:

traffic, weather, date, ...

(no mobile system info)

frame (time) synchronization,

identification of neighbour cells

(handover)

identification of BCCH frequency, MS

frequency synchronization

Fig. 4 Broadcast control channel

Paging Channel

PCH

Notification Channel

NCH

Access Grant

Channel AGCH

Random Access

Channel RACH

Common Control

Channel CCCH

paging of a MS in all cells of a

location area for a mobile

terminating call

paging of MS‘s in all cells of a

voice group call area to perform

ASCI (Advanced Speech Call Items)

answer to a random access,

assignment of dedicated

signaling channel

MS requests a dedicated

channel from network

Fig. 5 Common control channel





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Fast Associated

Control Channel

FACCH

Slow Associated

Control Channel

SACCH

Stand Alone

Dedicated ControlChannel SDCCH

Dedicated

Control

Channel DCCH

“in band” signaling channel (periodic):

downlink: system info, power command, TA;

uplink: measurements (level quality),

short messages service

“out of band” signaling channel for:

call setup signaling, short message service

(SMS), location update (LUP),IMSI attach/detach

“in band” signaling channel (sporadic):

handover signaling

channel mode modify: speech→

data

Fig. 6 Dedicated control channel




MN1789EU11MN_0002

© 2005 Siemens AG

10

Multiplexing of Logical Channels

1 physical channel (time slot) can carry one of the following logical channel

combinations:

Channel Combination Capacity

a) TCH/F + FAACH/F +SACCH/F

1 full rate subscriber

b) TCH/H (0, 1) + FACCH/H (0, 1)+ SACCH/H (0, 1)

2 half rate subscriber (speech or data)

c) FCCH + SCH + BCCH +CCCH

uplink: 800 000 RACH slots per hour downlink: 140 000 CCCH blocks per hour

d) FCCH + SCH + BCCH +CCCH +SDCCH/4 (0..3) + SACCH/4(0..3)

uplink: 400 000 RACH slots per hour downlink: 46 000 CCCH blocks per hour + dedicated signaling channels for 4 subscribers

e) SDCCH/8 (0..7) + SACCH/8(0..7)...

dedicated signaling channels for 8subscribers

1 RACH slot: 1 channel request message of 1 subscriber.

1 CCCH block (4 slots): • 1 paging message for 1..4 subscribers or

• 1 access grant message for 1..2 subscribers.





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MN1789EU11MN_0002

© 2005 Siemens AG

12

Channel Organization in a Cell

In SBS the following channel combinations are allowed:

• TCH/F + FACCH/F + SACCH/F TCHFULL

• FCCH + SCH+ BCCH+ CCCH (AGCH + PCH + RACH) MAINBCCH

• FCCH + SCH + BCCH + CCCH + 4 (SDCCH + SACCH) MBCCHC

• SDCCH/8 + SACCH/C8 SDCCH

• TCH/H (0) + FACCH/H (0) + SACCH/H (0) + TCH/H (1) ) +FACCH/H (1) + SACCH/H (1)

TCHF_HLF

• FCCH + SCH + BCCH + CCCH + 3 (SDCCH + SACCH) + CBCH BCBCH

• 7 (SDCCH + SACCH) + CBCH SCBCH

• BCCH + CCCH CCCH

TCH/H(0,1) + FACCH/H(0,1) + SACCH/H(0,1) or TCH/F + FACCH/F + SACCH/TF or SDCCH/8 + SACCH/C8

TCHSD

In a cell with a single RFC the allocation should be the following:

Timeslot 0 → FCCH+SCH + BCCH + CCCH + 4 (SDCCH + SACCH)

Timeslot 1...7 → TCH/F + FACCH/F + SACCH/F

The timeslot 0 runs in the 51 frame organization as shown in figures 7 and 8.

The timeslots 1 to 7 run in the 26 frame organization as shown in figure 9.

:

In a cell with 2 RFC there are more possibilities, depending on the used traffic model(SDCCH dimensioning), for example:

RFC-0 see cell with 1 TRX

RFC-1 Timeslot 0...7 → TCH/F + FACCH/F + SACCH/F

or

Timeslot 0 → 8 (SDCCH + SACCH)

Timeslot 1...7 → TCH/F + FACCH/F + SACCH/F





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F

0

S

1

BCCH

2 - 5

CCCH

6 - 9

F

10

S

11

CCCH

12 - 19

F

20

S

21

CCCH

22 - 29

F

30

S

31

CCCH

32 - 39

F

40

S

41

CCCH

42 - 49

I

50

DL: F = FCCH, S = SCH, B = BCCH, C = CCCH, (PCH, AGCH), I = idle

UL: R = RACH

R

0

R

1

R

10

R

11

R

20

R

21

R

30

R

31

R

40

R

41

R

50

Fig. 7 Multiframe for channel combination MAINBCCH

F S B C F S C C F S D0 D1 F S D2 D3 F S A0 A1 I

51 TDMA Frame = 235,38 ms

DOWNLINK: Broadcast Control Channel (BCCH), Common Control Channel (CCCH)

+4 Stand Alone Dedicated Control Channels (SDCCH/4)

UPLINK: Common Control Channel (CCCH)

+4 Stand Alone Dedicated Control Channels (SDCCH/4)

D3 R R A2 A3 R R R R R R R R R R R R R R R R R R R R R R R R RD0 D1 D2

D3 R R A0 A1 R R R R R R R R R R R R R R R R R R R R R R R R RD0 D1 D2

F S B C F S C C F S D0 D1 F S D2 D3 F S A2 A3 I

B BCCHC CCCHD SDCCHF frequency correction burstR RACHS synchronized burstI idle

Fig. 8 Multiframe for channel combination MBCCHC (2xMBCCH makes SACCHBCCH multiframe =2x 235,38 msec)




MN1789EU11MN_0002

© 2005 Siemens AG

14

TT TT TT TT TT TT A TT TT TT TT TT -TT

t 2 Half Rate TCH

1 Full Rate TCH

26 frames = 120 ms

T tT tT tT tT tT A Tt Tt Tt Tt Tt aTt

T: Traffic Channel (TCH) Burst for subscriber 1t: Traffic Channel (TCH) Burst for subscriber 2A: Slow Associated Control Channel (SACCH) for subscriber 1a: Slow Associated Control Channel (SACCH) for subscriber 2

Fig. 9 Time organization for one TCH Multiframe





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1.1 Control channel configuration




MN1789EU11MN_0002

© 2005 Siemens AG

16

Introduction

In a MOC, MTC, LU the MS has to request an SDCCH using the RACH. There is a

time delay between the request and the SDCCH allocation due to the traffic load. If there is a free SDCCH, it is allocated using the AGCH. The SDCCH is used for theauthentication, transmission of cipher parameters and call initialization. Next a trafficchannel is requested and allocated, if available. After this, the SDCCH is released.The MS acknowledges the allocation on the FACCH. The TCH with its FACCH andSACCH is occupied until the end of the call. So the blocking probability is a functionof

• availability of SDCCH

• availability of TCH

• waiting time in TCH queue, if queuing performed (BTS parameter)

• time for connection establishment.

1.2 Dedicated channel

If we evaluate a given traffic model, we find a certain traffic load per subscriber.Additionally we have to calculate the SDCCH load per subscriber.

According to the traffic model given in appendix-C, there are four values to beconsidered:

• call attempts per subscriber per hour 1.1

• time for MOC/MTC setup signaling 3 sec

• time for Location Update 5 sec

• location updates per subscriber per hour 2.2.

The SDCCH load per subscriber is calculated as follows:

(1.1 * 3 sec + 2.2 * 5 sec) / 3600 sec = 0.004 Erl.

Furthermore we have for the TCH: 25 mErl.

At the following page an example for a channel configuration of a 2 carrier cellsis given using the assumptions above.





17

Example for Channel Configuration

Assumptions: 25 mErl TCH Load per subscriber

4 mErl SDCCH load per subscriber

no load problem on CCCH

Cell with 2 TRX: 16 channels

Configuration A Configuration B

• 1 comb. CCCH/SDCCH → 4 SDCCH

• 15 TCH

• uncomb. CCCH

• 1 SDCCH/8 → 8 SDCCH

• 14 TCH

offered TCH load at 1 % blocking

8.11 Erl → Subscriber 8.11 / 0.025 = 324

offered TCH load at 1 % blocking

7.35 Erl → Subscriber: 7.35 / 0.025 = 294

offered SDCCH load at 1 % blocking

0.87 Erl → Subscriber 0.87 / 0.004 = 218

offered SDCCH load at 1 % blocking

3.13 Erl → Subscriber: 3.13 / 0.004 = 782

→ SDCCH limited: 218 subscriber → TCH limited: 294 subscriber

→ Configuration B is the better one for this scenario.




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1.3 Smooth Channel Modification

The control channel configuration up to BR5.5 is a static definition of the channel type(TCH or SDCCH) independent of the dynamic variations of the SDCCH traffic load inthe network.

Smooth Channel Modification offers an automatic change of the channel type (e.g.between TCH and SDCCH/8) without operator interaction.

If the SDCCH load is higher than a settable threshold, an additional SDCCH isautomatically used instead of an idle TCH.

In case of unexpected high SDCCH load (SMS traffic, LCS, specific areas as airportsor PLMN borders, ...) a blocking of SDCCH is avoided.

This results in saving of resources on Um interface, since a further SDCCH does nothave to be configured permanently.

Flexible channels used as TCH or SDCCH are created as channel type 'TCHSD'. Toprovide full flexible channel configuration, a radio frequency pool concept isintroduced.

The customer selects and configures the channels to be used as TCH or SDCCH for each carrier. This can be done when new versions or new cells are introduced to the

network or new carriers are added to a cell. These channels are created using thenew TCH_SD channel type. When the BSC selects a TCHSD channel for a specificservice, the operational mode notifies the BTS on a call-by-call basis using a channelactivation message. The system can then dynamically use the timeslot as either aTCH or a SDCCH without further service interruption.

A radio frequency pool of resources in the BSC allows flexible allocation of radiofrequency resources. Each TCH, SDCCH and TCHSD is assigned to a specific pool,TCH and SDCCH are assigned permanently to their related pools, and each TCHSDis assigned by the operators using the new specific object attribute CHPOOLTYP.

This attribute can be changed using a SET command.





19

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TS 0 TS 1 TS 2 TS 3 TS 4 TS 5 TS 6 TS 7

SDCCH_POOL TCH_POOL TCH/SD_POOL

SDCCH_BACKUP _POOL

assignment

In case of

SDCCH request

Traffic Channel / SDCCH Request

Fig. 10 Pooling concept for smooth channel modification




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SDCCH Allocation Strategy

In case of SDCCH request the BSC first tries to get one SDCCH sub-channel from

the SDCCH_POOL. If the SDCCH_POOL and the SDCCH_BACKUP_POOL areempty or congested (i.e. all sub-channels are busy) the BSC moves eight sub-channels with best quality from TCH_SD_POOL to SDCCH_BACKUP_POOL anduses one sub-channel to satisfy the request.

If also in the TCH_SD_POOL there is no resource available and the service requestis MOC and MTC, the direct assignment procedure is tried. If the requested servicesare Location Update Procedure LUP-SMS or SDCCH/SDCCH-H/O the service isrejected.

Additionally a configurable SDCCH congestion threshold on cell basis is implementedin order to move a sub-channel from TCH_SD_POOL to SDCCH_BACKUP_POOL

when the sub-channel occupation (i.e. the sum of SDCCH_POOL andSDCCH_BACKUP_POOL) is higher than this threshold for two seconds. The rangeof the SDCCH congestion threshold can be set by the operator. Due to peak loadtraffic (e.g. SMS) at different times, the system can then automatically shareresources between signaling and speech without configuration changes thusreducing blocking probability in signaling phase.

SDCCH Release Strategy

When a SDCCH sub-channel is released and coming from the SDCCH_POOL thesub-channel is returned to that pool. If the sub-channel to be released is coming from

the SDCCH_BACKUP_POOL and is not the last sub-channel busy in the TCH_SD,the sub-channel is returned in the SDCCH_BACKUP_POOL. If the sub-channel to bereleased is coming from the SDCCH_BACKUP_POOL and is the last sub-channelbusy in the TCH_SD, the decision of the destination pool is based on a configurableattribute. This attribute is cell based and specifies the guard timer for return of theTCH_SD channel to the TCH_SD_POOL. This timer is implemented to avoidoscillation between TCH_SD_POOL and SDCCH_BACKUP_POOL.

TCH Allocation Strategy

In case of TCH full request, the BSC uses the TCH with the best quality from theTCH_POOL. In case of TCH half request the BSC first tries to use unpairedchannels. If TCH_POOL is empty or congested, the BSC tries to get one TCH_SDfrom the TCH_SD_POOL. If both pools are empty or congested, a directed retryprocedure is attempted for new MOC or MTC. In case of handover, the target cell listis scanned in order to find a target cell not congested.

TCH Release

At TCH release the TCH is returned to the original pool.





21

Fig. 11 The process trigger by an SDCCH request




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Parameters for Channel Configuration:

Specification Name DBName

Object Range

(default)

Meaning

CH_TYPE

GSM 04.08

GSM 05.01

GSM 05.02

CHTYPE CHAN TCHFULLSDCCHMAINBCCHMBCCHCCCCHSCBCHBCBCHTCHF_HLFTCHSD

Type of Channelcombination

CH_POOL_TYPE CHPOOLTYP

CHAN TCHPOOLSDCCHPOOLTCHSDPOOLNULL

(NULL)

Channel Pool Typemust be defined if CH_TYPE=TCHSD

SDCCH_CONGESTION_ THRESHOLD

SDCCHCONGTH

BTS 70 ... 100[ % ]

(70)

SDCCH CongestionThreshold

GUARD_TIMER_TCHSD TGUARDTCHSD

BSC SEC00

SEC10(SEC10)

SEC11SEC12SEC13SEC14SEC15

Guard Timer TCHSD





23

1.4 Random access channel

Capacity of the RACHThe RACH is used by the MS to request a dedicated channel, the SDCCH. Thechannel request needs one RACH timeslot. The cause for the channel request canbe a paging response in MTC, an emergency call, a MOC, LU or IMSI attach/detach.According to the traffic model from appendix-C there are about 4 RACH activities per subscriber per hour.

Configuration of the RACH

The RACH is configured only uplink, his frequency corresponds to the downlink

BCCH frequency. The RACH may be combined with the uplink part of the SDCCH. Inthe combined case, the RACH is multiplexed onto 27 timeslots 0 out of 51 of aBCCHcombined. These 27 RACH are spread over the multiframe as follows:

SSSSRRSSSSSSSSRRRRRRRRRRRRRRRRRRRRRRRSSSSSSSSRRSSSS

with S = SDCCH/SACCH and R = RACH.

The RACH can also be configured uncombined on all timeslots 0, 2, 4, 6.

This gives the following capacities, the frame duration is 4.6 ms (period between twosuccessive timeslots 0):

combined: 27/51 of all timeslots 0 => 400000 RACH slots per hour

uncombined: timeslot 0 => 800000 RACH slots per hour

uncombined: timeslot 0,2 => 1560000 RACH slots per hour (not in BR2.1)

uncombined: timeslot 0,2,4 => 2340000 RACH slots per hour (not in BR2.1)

uncombined: timeslot 0,2,4,6 => 3120000 RACH slots per hour (not in BR2.1)

In a cell with 5000 subscriber normally there are about 20 000 RACH activities per hour only!




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1.4.1 RACH Control Parameter

RACH busy threshold, defines a threshold for the signal level during the RACHbursts. The BTS measures the signal level on each RACH timeslot and determineswhether a channel request is successfully received or not: If the received signal levelis greater than or equal to the value of RACHBT then the RACH burst in question willbe indicated as busy (one or more mobile stations have tried to access the network).The purpose of this parameter is to avoid unnecessary load on the BSS by normalnoise signals being decoded as RACH bursts (followed by seizure of SDCCH) bymistake. However, to be on the safe side the BTS does not only evaluate the RACHlevel but additionally decodes the Synch sequence bits of the RACH burst.

Note: The value entered for this parameter is not only relevant for the CHANNELREQUEST message on the RACH but also for the HANDOVER ACCESSmessage on the FACCH!

The MS receives the RACH control parameters from the base station on the BCCH:

• Maximum number of retransmission (max_retrans) MAXRETR = 1, 2, 4, 7.If a channel request is not acknowledged by the base station, the MS repeats therequest until the given value of MAXRETR.

• Number of slots to spread transmissions (tx_integer) NSLOTST = 0,..15

representing the real values according to the following table:

NSLOTST value 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

GSM value 3 4 5 6 7 8 9 10 11 12 14 16 20 25 32 50





25

The NSLOTST value determines the time period between sending of two channelrequests. This period is measured in RACH slots and is the sum of a deterministicpart td and a random part tr:

MS tx_integer td (RACH slots,combined)

td (RACH slots,uncombined)

3, 8, 14, 50 41 (0.35 sec) 55 (0.25 sec)

4, 9, 16 52 (0.45 sec) 76 (0.35 sec)

5, 10, 20 58 (0.50 sec) 109 (0.50 sec)

6, 11, 25 86 (0.75 sec) 163(0.75 sec)

Phase 2

7, 12, 32 115 (1.00 sec) 217(1.00 sec)

Deterministic part td of retransmission period as a function of tx_integer

The random part tr is an integer between 1 and tx_integer where the probability of choosing a certain time slot i is given by:

p ( tr = i ) = 1 / tx_integer for i = 1...tx_integer.

tr = tx_integer = 6

retransmission

td = 163 slots

first transmission

with a collision

Fig. 12 Retransmission of CHANNEL_REQUEST




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Immediate Assignment Procedure

The procedure is specified in GSM 04.08, chapter 3.3.1.2:

set timer T3126

wait for grant

WAIT

T3122

SDCCH

Allocation

N

Y

Y

N

N

Y

number of

retransmissions + 1

number of

retransmissions = 0

Select RACH slot

for first transmission

IMMEDIATE

ASSIGNMENT

PROCEDURE

no.of

retransmissions

= max_retrans

immediate

assignment

Send CHANNEL

REQUEST msg.

GRANT during

Sup. time

Rejection

CELL

RESELECTION

N

Y

Select RACH slot for

next transmission,

wait for grant

Fig. 13 Immediate assignment procedure





27

Evaluation of Immediate Assignment Procedure for different parameter values

Traffic Load/RACH Activities per Hour The relative traffic load is the average number of initiated immediate assignmentprocedures or RACH activities in a timeslot:

traffic load =total number of immediate assignment procedures / total number of RACH slots.

The absolute number of RACH activities per hour is obtained by multiplying thisrelative load with the number of RACH slots per hour.

Blocking

The blocking shows the percentage of not successful immediate assignmentprocedures initialized by the MS.

blocking [%] =(number of unsucc. imm. ass. proc. / total number of imm. ass. Proc. ) * 100.

Throughput

The channel throughput is the average number of successful transmissions per timeslot.

throughput = number of successful transmissions/number of simulated time slots.

throughput = ( 1 - blocking ) * traffic load.

Wait Time

The wait time is the time between the initiation of the immediate assignmentprocedure and the arrival of the immediate assignment message. For the waiting timeit is useful to consider the 90% quantile of the wait time:

for 90% of the immediate assignment procedures, the wait time is less than the timet90.

The blocking and the 90% (95%) quantile for different values of the RACH controlparameters is shown in the following tables for a combined RACH/SDCCH:




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tx_integer max_retrans blocking(%) 90% quantile(s) 95% quantile(s)

3 1 2.9 < 0.1 0.353 2 1.1 < 0.1 0.35

3 4 0.2 < 0.1 0.35

3 7 < 0.01 < 0.1 0.4

7 1 1.6 < 0.1 1.0

7 2 0.4 < 0.1 1.0

7 4 0.1 < 0.1 1.0

7 7 < 0.01 < 0.1 1.0

14 1 0.9 < 0.1 0.4

14 2 0.1 < 0.1 0.4

14 4 < 0.01 < 0.1 0.4

14 7 < 0.01 < 0.1 0.4

25 1 0.6 < 0.1 0.8

25 2 < 0.1 < 0.1 0.8

25 4 < 0.01 < 0.1 0.8

25 7 < 0.01 < 0.1 0.8

50 1 0.5 < 0.1 0.5

50 2 0.1 < 0.1 0.5

50 4 < 0.01 < 0.1 0.5

50 7 < 0.01 < 0.1 0.5

Values for 25000 RACH activities per hour





29

tx_integer max_retrans blocking(%) 90% quantile(s) 95% quantile(s)

3 1 6.1 0.353 2 2.8 0.35 0.75

3 4 0.6 0.35 0.75

3 7 0.1 0.35 0.75

7 1 3.6 1.0 1.1

7 2 1.0 1.0 1.1

7 4 0.1 1.0 1.1

7 7 < 0.1 1.0 1.1

14 1 2.6 0.4 0.45

14 2 0.5 0.4 0.45

14 4 < 0.1 0.4 0.45

14 7 < 0.01 0.4 0.45

25 1 2.0 0.8 0.9

25 2 0.4 0.8 0.9

25 4 < 0.01 0.8 0.9

25 7 < 0.01 0.8 0.9

50 1 1.8 0.5 0.7

50 2 0.2 0.5 0.7

50 4 < 0.01 0.5 0.7

50 7 < 0.01 0.5 0.7

Values for 50000 RACH activities per hour.

The results of these studies show, that even the RACH minimal configuration(combined RACH/SDCCH is able to serve 50000 RACH activities per hour at a lowblocking (< 0.5%) with an acceptable wait time. An uncombined RACH is able toserve twice the traffic load with the same grade of service. The minimum blocking for the considered traffic load is achieved by the following setting of parameters:max_retrans = 7, tx_integer = 50.

Though a combined RACH can serve the expected traffic load, another RACHconfiguration may have to be chosen. The RACH is only the uplink part of the CCCH.The downlink parts (AGCH,PCH) may need a higher capacity. Therefore, theconfiguration of CCCH is determined by the capacity needed by the downlinkchannels, the RACH configuration is uncritical.




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1.5 Paging / access grant and notification channel

PCH/AGCH

The paging channel and the access grant channel share the same TDMA framemapping (modulo 51) when combined onto a basic physical channel. The channelsare shared on a block by block basis. The information within each block allows theMS to determine if it is a paging or an access grant message. Every paging channelcan be used by the system as access grant channel but it is not allowed to thesystem to use access grant channels as paging channels. However, to ensure amobile a satisfactory access to the system, there is a control parameter to define afixed number of access grant blocks in the 51 multiframe. The number of blocksreserved for AGCH is broadcasted on the BCH. The number of available paging

blocks is reduced by this number.

1.5.1 PCH/AGCH Control Parameters

Paging channels may be used as access grant channels but not vice versa.Therefore it is useful to set the parameter BS_AG_BLKS_RES to the smallest valueand let the system organize the use of channels. In case of MOC more AGCH areneeded, in case of MTC more PCH are needed. In average the number of MOC ishigher than the number of MTC. If the BS_AG_BLKS_RES value is set too high withthe result of a PCH shortage, a overload indication for the PCH may arise in hightraffic time.

In GSM traffic model the paging per subscriber per hour is 0.93.

The second parameter to be set is called BS_PA_MFRMS (value = 2..9, number of multiframes between paging). It indicates the number of TDMA multiframes betweentransmission of paging messages to the same paging subgroup. The MS gets theinformation on BCH, to which paging groups it should listen to. By this way the MScan save battery because it only listens to its own paging group. If the value is toohigh so that the time between two blocks of the same paging sub-channel is high, thetime for setting up an MTC is high.

In a medium cell the common channel pattern on timeslot 0 on one of the TRX canuse the following combination downlink (in uplink all channels are used as RACH):

FSBBBBPPPPFSPPPPPPPPFSPPPPPPPPFSPPPPPPPPFSPPPPPPPP

F = FCCH

S = SCH

B = BCCH

P = PACH/AGCH.

An example for the load and the servable number of subscribers is given at the

following pages.





31

M

S

C

B

S

C

LAC

PAGING MESSAGE :

- IMSI or IMSI+TMSIPAGING COMMAND:

- IMSI or TMSIB

T

Spaging group:

NFRAMEPG

(CCCHs monitored by MS)

M

S

queuing of

paging requests

MS

MS

paging request

type 1, 2 or 3

Fig. 14 Number of multiframes between paging

1.5.2 NCH Control Parameters

In all cells where the ASCI (Advanced Speech Call Item) service is enabled, andownlink logical channel belonging to CCCH is defined, Notification Channel (NCH).An MS which is VBS/VGCS (Voice Broadcast Service /Voice Group Call Service)subscriber, besides the paging blocks, monitors also the Notification Channel. Thislogical channel is mapped onto contiguous blocks reserved for access grants, theposition and the number of blocks are defined by the two parametersNCH_FIRST_BLOCK and NCH_BLOCK_NUMBER.

Service subscribers are notified of the VBS/VGCS call in each cell via notificationmessages that are broadcasted on the Notification Channel; these messages don’tuse individually TMSI/IMSI but the group identity and service area identity.

The process of broadcasting messages on NCH is carried out throughout the call inorder to provide late entry facility. The repetition time is defined by the parameter TIMER_NCH.




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1.5.3 Improved CCCH handling between AGCH and PCH

To make the CCCH block management more flexible, in BR8.0 a new mechanismwas introduced which observes the current filling state (load) of the AGCH queue.The mechanism dynamically priorities the AGCH message higher then the pagingmessages if the detected AGCH queue load requires that and features thepreemption of unreserved CCCH blocks (i.e. blocks that are shared between PCHand AGCH) for AGCH procedures even if also paging messages are queued for transmission in the BTS paging queues.

Improvements

• 16 instead of 4 Immediate Assignment entries can be queued

• two Immediate Assignment Command can be combined within one AGCH

• modification of the priority for ''not reserved'' CCCH blocks by defining threesignaling loads (NORMAL, MEDIUM and HIGH) for AGCH queue

The priority of PCH messages before AGCH messages depends on the currentAGCH queue filling state.

The AGCH queue load is assumed NORMAL when less then 12 out of 16 AGCHqueuing places are used. This implies that the IMMEDIATE ASSIGNMENT (REJ)

messages waiting for delivery in the AGCH queue are delivered on a non-reservedblock only if no PAGING REQUEST message is pending in the paging queue (seepicture below).

The AGCH queue load is assumed MEDIUM when there are still less then 12IMMEDIATE ASSIGNMENT (REJ) messages in the queue but some are in danger of being delayed too much if not quickly delivered over the Um interface. Under theseconditions, the preemption takes place only on those paging queues that arecompletely empty or half full, but not already preempted during the last CCCH cycle(e.g. IMMEDIATE ASSIGNMENT (REJ) message is sent if in the previous cyclePAGING REQUEST was sent from the queue).

The AGCH queue load is assumed HIGH when there are more then 12 IMMEDIATEASSIGNMENT (REJ) messages in the queue. In this case AGCH blocks haveabsolute precedence over PCH ones until the number of AGCH pending in queuedrops again below 12.

There is no parameter to enable improved handling of CCCH mechanism.





33

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Fig. 15 Common control channel handling




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1.6 CCCH load

paging messages per hour: SUBSCR * LA_size * MTC_ph * REPET/subscr_per_pag_message

random messages per hour: SUBSCR * (MTC_PR_ph + MOC_ph + LU_ph +IMSI_ph + SMS_ph)

access grant messages per hour:

SUBSCR * (MTC_PR_ph + MOC_ph + LU_ph +IMSI_ph + SMS_ph) / subscr_per_agch_message

SUBSCR number of subscribers within the cell

LA_size number of cells on the location area

MTC_ph mobile terminating calls per subscriber per hour (with andwithout paging response)

REPET mean number of repetitions of a paging message (nopaging response to first paging)

MTC_PR_ph mobile terminating calls per subscriber per hour withpaging response to first paging)

MOC_ph mobile originating calls per subscriber per hour

LU_ph location updates per subscriber per hour

IMSI_ph IMSI attach/detach per subscriber per hour

SMS_ph short message service requests per subscriber per hour





35

CCCH Load

ExampleCalculate the number of subscribers that can be served in a cell regarding CCCHload if the traffic model described with the following values is used.

SUBSCR: ?

LA_size: 20

MTC_ph: 0.46

REPET: 1.33

MTC_PR_ph 0.30MOC_ph 0.64

LU_ph 2.2

IMSI_ph 1.0

SMS_ph -

subscr_per_pag_message = 2

subscr_per_agch_message = 1.0

Consider both possible configurations for the CCH.

Solution

• paging messages per hour = SUBSCR * 20 * 0.46 * 1.33/2 ∼ SUBSCR * 6/h

• access grant messages per hour ∼ SUBSCR * 4/h

→ paging + access grant messages per hour ∼ SUBSCR * 10/h

→ ∼ 4600 subscriber (combined CCCH)

→ ∼ 14000 subscriber (uncombined CCCH)

• random access messages per hour ∼ SUBSCR * 4 / h

(at 10 % load)

→ ∼ 10000 subscriber (combined CCCH)

→ ∼ 20000 subscriber (uncombined CCCH)




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Parameters for Common Control Channel Configuration

Specification Name DB Name Object Range

(default)

Meaning

RACH_BUSY_THRES RACHBT BTS 0...127

(109)

RACH busy threshold defined insteps of -1 dBm

MAX_RETRANS

GSM 04.08

GSM 05.08

MAXRETR BTS ONETWOFOURSEVEN

(FOUR)

Maximum number of allowedretransmissions of a channelrequest on the RACH

TX_INTEGER

GSM 04.08

NSLOTST BTS 0...15

(10)

Number of RACH slots tospread re-transmission of channel request; also fixing hedeterministic part of wait time

0 ... 15 =

3, 4, 5, 6, 7, 8, 9, 10, 11, 12,14, 16, 20, 25, 32, 50

BS_AG_BLKS_RES

GSM 04.08

GSM 05.02

NBLKACGR BTS 0...7 for uncomb. 0...2for comb.CCCH

(1)

Number of common controlblocks per multiframe used for access grant exclusively

BS_PA_MFRMS

GSM 04.08

GSM 05.02

GSM 05.08

NFRAMEPG

BTS 2...9

(2)

number of multiframes betweenpaging blocks belonging to thesame paging sub-channel

NCH_FIRST_BLOCK NOCHFBLK BTS 1...7

(1)

indicates the first block of downlink CCCH to be used for NCH

NCH_BLOCK_NUMBER NOCHBLKN BTS 1...4

(1)

number of downlink CCCHblocks to be used for NCH

TIMER_NCH TNOCH BTS 1...254

(1)

repetition period for notificationmessages defined in steps of one multi-frame period – 235ms





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MN1789EU11MN_0002

© 2005 Siemens AG

38

1.7 Additional ASCI service related parameters

ASCI service is enabled via parameter ASCISERThis service introduced in the SBS BR5.5 has been improved with a number of procedures since BR6.0 that are defined with a number of additional parameters.

Uplink reply procedure

Uplink reply procedure delays the assignment of common broadcasted (TCH)channel until required by a mobile "interested" in that ASCI call. In that way the trafficchannel resources in the cell belonging to the Group Call Area but without ASCIlistening subscribers are saved. Notification messages are sent without the

VBS/VGCS channel description in that cell.The parameter ASCIULR is used to enable or disable the uplink reply procedure for VGCS calls only (VGCSENABLE), VBS calls only (VBSENABLE) or both at the sametime (VBS_VGCSENABLE).

Description

When an ASCI group call (VBS or VGCS) is set up in a cell and simultaneously anASCI common TCH was activated, the BTS broadcasts the group call reference andthe Channel Description data of the ASCI common TCH via the NCH in the cell. Inthis situation, the BSC may initiate the release of the activated ASCI common TCH, if no listening ASCI MSs are available in the cell. To check whether or not ASCI MSs

are present in the cell, the BTS sends the UPLINK FREE message via the FACCHassociated to the ASCI common TCH and waits for an UPLINK ACCESS message.This UPLINK ACCESS message is sent on the ASCI common TCH and is theresponse from the ASCI MSs, if they have previously received the UPLINK FREEmessage with the IE ‘Uplink Access Request’ included.

For the supervision of this procedure, the BTS uses 2 timers: TWUPA (timer to waitfor uplink access, hardcoded in the BTS) and the administrable timer TUPLREPwhich are both started when the UPLINK FREE message is sent. The BTS assumesthat no listening ASCI MS is present in the cell and initiates the de-allocation of theASCI common TCH in this cell by sending the VBS/VGCS CHANNEL RELEASE

INDICATION towards the BSC, which in turn releases the channel by sendingCHANNEL RELEASE, DEACTIVATE SACCH, RF CHANNEL RELEASE etc.

ASCI one channel model and Talker Change Procedure

Even the Notification without Channel Description and Uplink Reply procedure allowssaving of the resources on the air interface, still remains the problem, that both sides,the talker and the listeners, have assigned different duplex connections each for hisown, not using the DL in case of the talker and the UL in case of the listeners.

With the ASCI one channel model feature the group call channel may be used both

by the talker and by the listeners: The UL will be occupied by the talker, if present in.





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Cell A

Cell 1 Cell 2 Cell 3

common downlinkcommondownlink

common downlink

uplink

Fig. 16 Advanced speech call items - principle




MN1789EU11MN_0002

© 2005 Siemens AG

40

The cell, the DL by the listeners. This way no separate dedicated TCH is necessaryfor the talker. In a cell with only listeners the UL of the group call channel is unused.In a cell without talker and listeners no group call channel will be allocated at all.

In case of an already allocated VGCS common channel one of the listener mobilestations may want to become talker (subsequent talker). The MS is sending UplinkAccess messages to the BTS. BTS reacts by sending a VGCS Uplink Grant messageto the requesting mobile station and a Talker Detection message to the BSC.

After the VGCS Uplink Grant message has been sent to the mobile station wanting tobecome talker, the respective task within BTS ignores any further Uplink Accessmessage on the VGCS common channel.

This way it is always guaranteed that in case of competitor talkers belonging to thesame VGCS group there may be only one talker per cell at a time to which the VGCScommon channel uplink has been granted by the BTS.

The call-initiating talker can not become a ‘subsequent’ talker with an originator reconfiguration. For this very first talker only an intra- or intercell HO to a dedicatedTCH is possible. Obviously, this call-initiating talker can subsequently become atalker again after he has left the uplink and he can try the talker change procedurelater on.

A subsequent talker may gain access to the uplink of a VGSC only through a Talker Change procedure.

For the BSC the parameter ASCIONECHMDL has to be set to true to enable theASCI one channel mode.

In case of setting the parameter ASCIONECHMDL to false BSC assigns a new TCHto the subsequent talker, this is also called 1,5 channel mode.

Late entry notification for VGC listeners

When a VGCS/VBS group call is established with a priority level equal to or higher than the level set by the operator (defined by the NOTFACCH parameter), FACCHnotifications (Fast Associated Control Channel) are periodically sent on the commonchannels of all other ongoing voice group (VGCS) and broadcast calls (VBS) in thatcell.

This notification is sent as long as the relevant high priority call lasts, and will berepeated at a rate indicated by a new PERNOTFACCH O&M parameter.

With this solution, mobile stations in the group receive mode are informed aboutongoing high-priority calls, irrespective of whether the call is a late entrant to a cell, or whether there is another ongoing ASCI call, or irrespective of a group transmit modeof a late entrant in that cell due to the handover of the subsequent talker (one-channel model).





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MN1789EU11MN_0002

© 2005 Siemens AG

42

Specification Name DB Name Object Range

(default)

Meaning

ASCI_SERVICE ASCISER BTS ENABLED,

DISABLED(DISABLED)

Enables or disables ASCIservice on a cell basis

ASCI_UPLINK_REPLY ASCIULR BTS ULRDISABLE

VBSENABLE

VGCSENABLE

VBC_VGCSENABLE

(ULRDISABLE)

The ASCI Uplink Replyparameter enables or disables the uplink replyprocedures for both VGCSand VBS

TIMER_UPLINK_REPLY TUPLREP BTS 5..60 s

(20)

This timer determines theperiod betweentransmissions of the UplinkFree message in the uplinkreply procedure.

NOTIFICATION_ FACCH NOTFACCH BSC NO SUPP,

ALWAYS,

HIGHEQx, x=0…4

(NOSUPP)

Indicates for which mobilepriorities theNOTIFICATION FACCHmessages are sent on theFACCH belonging to theTCH seized by one ASCIsubscriber

TIMER_GRANT TGRANT BTS 1…-254

unit 10ms

(4)

This timer determines the

periodin which BTS waits for acorrectly decoded messagefrom MS as an answer tothe sent message VGCS ULGRANT

VG_UPINK _FREE VGRLUF BTS 1…254

(1)

This parameter is used for the repetition of the UPLINKFREE message during theTalker Change procedure toinform all MS that UL is free

ASCI_ONE _CH_MODEL ASCIONE-CHMDL

BSC TRUE,FALSE

(FALSE)

Determines whether theASCI "one channel model"

is enabledor not

ENABLE _NCH_REPET ENPERNOTDE BTS TRUE, FALSE

(FALSE)

This attribute enables therepetition of notifications ondedicated channels

REPET_PER_FACCH PNOFACCH BTS 2…10

unit 0,5s

(5)

This attribute defines theduration of the repetitionperiod for the FACCHnotification of a given ASCIcall





43

2 Extended channel mode




MN1789EU11MN_0002

© 2005 Siemens AG

44

In a normal GSM standard cell the maximum MS-BTS distance is 35 km; this is thelimit given by the maximum TA (timing advance 0...63 bit) which is possible on oneradio timeslot.

Distance calculation:

Dist = TA * bit-period * light-speed / 2

bit-period = 48/13 (3.69) µs

light-speed = 300000 km/s.

The feature ‘Extended Cells’ supports a larger distance between MS and BTS byusing two subsequent radio timeslots to compensate the longer delay of the bursts.The first timeslot of a double timeslot has always an even number (0,2,4,6), thefollowing corresponding channel must not be created.

For a double timeslot the maximum propagation delay can be 219 bit ( 120 km), butnote that the maximum distance which can be configured by O&M is 100 km.

The BTS splits the propagation delay into two values:

• timing advance (TA), covering the first 63 bit delay

• timing offset (TO), used for extended cells as an offset to TA for delays greater 63bit (the propagation delay is the algebraic sum of TA and TO).

When activating the SDCCH and later the TCH for that corresponding MS, theevaluated initial TA value forms part of the layer 1 header downlink, the initial TO isused BTS-internally.

If the average of the deviation exceeds 1 bit period (48/13 µs) in comparison to theTA confirmed by the MS (contained in every uplink SACCH header information), thepreviously ordered TA is incremented/decremented by one and sent as new orderedTA in the layer 1 header downlink to MS. As previously mentioned TA cannot exceed63 bit. TO is used internally for processing further delay in case of extended cells.Note that TO may only be greater then 0 when TA has the maximum value 63.

In extended cells all control and signaling channels must be defined in extended(double) mode.

Specification

Name

DB Name Object Range

(default)

Meaning

CELL_TYPE CELLTYPE BTS STDCELL

(STDCELL)

EXTCELL

DBSTDCELL

maximum range35 km a cell covering,

maximum range 100 kma cell covering,

dual band standard cell

EXTENDED_MODE EXTMODE CHAN TRUEFALSE

(FALSE)

defines if a channel isused in extended

mode or not





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Max

100 km

Max

35 km

BTS

0 42 3 51 6 7 TRX in Extended Cell

(for near and far area)EXTMODE=TRUE EXTMODE=FALSE

Fig. 17 Extended Cell




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3 Adaptive Multirate AMR




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3.1.1 General

The Adaptive Multi Rate Speech Codec (AMR) is made up of a set of speech codecmodes at different bit rates. Each codec mode provides a different level of error protection on the air interface, obtained by varying the balance between source (i.e.speech) coding bit rate and radio channel coding bit rate. All modes may be mappedto full rate channels, only the lower bit rate modes may be mapped to half ratechannels.

The currently available speech codecs (FR, EFR, HR) show several constraints.They operate at constant source and channel coding bit rate and at constant error protection. The quality of FR and HR is not high enough to cope with wireline speech,EFR is not robust enough against bad radio conditions. The flexibility of AMRprovides important benefits:

• Improved speech quality in both half-rate and full-rate modes by means of codecmode adaptation, i.e. varying the balance between speech and channel coding for the same gross bit-rate.

• Ability to trade speech quality and capacity smoothly and flexibly by a combinationof channel and code mode adaptation.

• Improved robustness to channel errors under bad radio signal conditions in full-rate mode. This increased robustness to errors and hence to interference may beused to increase capacity by operating a tighter frequency re-use pattern. Thisallows the optimization of networks for high quality or high capacity.

• Use of certain modes for special applications, e.g. wireline quality half-rate for indoor with low channel errors

• In full-rate mode only, the robustness to high error levels is substantially increasedsuch that the quality level of EFR at a C/I of 10 dB is extended down to a C/I of 4dB. This gives additional coverage in noise limited scenarios.





49

Channel Coding Speech Coding

Traffic Channel Full: Gross rate 22.8 kbit/s

Flexible

balance

Fig. 18 AMR principle

11,4

kbit/s

22,8

kbit/s

0FR1 FR2 FR3 FR4 FR5 HR2 HR5 HR6

channel coding FR

channel coding HR

speech coding

FR6 FR7 FR8 HR1 HR4HR3

Fig. 19 AMR codecs




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1.0

2.0

3.0

4.0

5.0

Conditions

MOS

EFR

12.210.2

7.95

7.46.7

5.95.15

4.75

EFR 4.01 4.01 3.65 3.05 1.53

12.2 4.01 4.06 4.13 3.93 3.44 1.46

10.2 4.06 3.96 4.05 3.80 2.04

7.95 3.91 4.01 4.08 3.96 3.26 1.43

7.4 3.83 3.94 3.98 3.84 3.11 1.39

6.7 3.77 3.80 3.86 3.29 1.87

5.9 3.72 3.69 3.59 2.20

5.15 3.50 3.58 3.44 2.43

4.75 3.50 3.52 3.43 2.66

No Errors C/I=16 dB C/I=13 dB C/I=10 dB C/I= 7 dB C/I= 4 dB C/I= 1 dB

Fig. 20 Family of curves (clean speech in full rate) acc. to ETSI study

1.0

2.0

3.0

4.0

5.0

No Errors C/I=16 dB C/I=13 dB C/I=10 dB C/I= 7 dB C/I= 4 dB C/I= 1 dB

Conditions

DMOS

Sel. Requir.

AMR-FR

EFR

FRG.729

Fig. 21 AMR performance curves (full rate with street noise) acc. to ETSI study





51

1.0

2.0

3.0

4.0

5.0

Conditions

MOS

EFR

7.957.4

6.75.95.15

4.75FRHR

EFR 4.21 4.21 3.74 3.34 1.58

7.95 4.11 4.04 3.96 3.37 2.53 1.60

7.4 3.93 3.93 3.95 3.52 2.74 1.78

6.7 3.94 3.90 3.53 3.10 2.22 1.21

5.9 3.68 3.82 3.72 3.19 2.57 1.33

5.15 3.70 3.60 3.60 3.38 2.85 1.84

4.75 3.59 3.46 3.42 3.30 3.10 2.00

FR 3.50 3.50 3.14 2.74 1.50

HR 3.35 3.24 2.80 1.92

No Errors C/I=19 dB C/I=16 dB C/I=13 dB C/I=10 dB C/I= 7 dB C/I= 4 dB

Fig. 22 Family of curves (clean speech in half rate) acc. to ETSI study

Capacity Improvement as a function of the AMR Handset

Penetration

(Parameter: Half Rate Operating Threshold)

0.0%

20.0%

40.0%

60.0%

80.0%

100.0%

120.0%

50% 60% 70% 80% 90% 100%

AMR Penetration

C a p a c i t y I m p r o v e m

e n t

15 dB

20 dB

25 dB

HR

Only

Fig. 23 AMR capacity gain acc. to ETSI study




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Most speech codecs including the existing GSM codecs (FR, HR and EFR) operateat a fixed coding rate. Channel protection against errors is added also at a fixed rate.The coding rates are chosen as a compromise between best clear channel

performance and robustness to channel errors. The AMR system exploits thisperformance compromise by adapting the speech and channel coding ratesaccording to the quality of the radio channel resulting in better quality and increasedrobustness against errors.

The new radio resource algorithm, enhanced to support AMR operation, allocates ahalf-rate or full-rate channel according to channel quality and the traffic load on thecell in order to obtain best balance between quality and capacity.

The channel measurement reports and any other information for the codec modeadaptation are transmitted in-band in the traffic channel. In addition the channelmode of the codec can be switched in order to increase channel capacity while

maintaining the speech quality to operator specified limits. These variations arecarried out by means of AMR modifications and handovers.

The allocation of AMR FR or AMR HR codecs can also be related to the currenttraffic load in the network. The operator sets the threshold for the traffic dependentallocation of HR channels (c.f. "Cell Load Dependent Activation of Half Rate").

Principles

• Channel state information is derived in MS and BTS.

• BTS/BSC decide which AMR codec mode is used based on channel state

information.

• Quality/robustness of AMR modes depend on division of the gross bit-rate intospeech and channel coding.

• In-band signaling is provided over the air interface to switch rapidly between thedifferent modes (within full-rate or half-rate modes) in order to adapt to the channelconditions.

• Switching between codec modes is seamless.

• AMR can also be operated in "HR only" mode. The speech quality perceived by

the subscriber is similar to present FR quality. AMR "HR only" mode is even better in respect to clean speech and channel errors. In case of background noise andchannel errors the performance is lower.

AMR Codec Modes

The AMR codec operates at different codec mode bit-rates (4.75 kbit/s to 12.2 kbit/s)including GSM EFR. Each codec mode performs differently under changing channelquality (C/I). The following table provides an overview on the codecs used.





53

AMR CodecMode Bitrate

(kbit/s)

Designation

(Full Rate / Half RateMode)

Support byBTSplus

Support byBTSone

12.2 FR 1 ("Enhanced FR") Yes Yes

10.2 FR 2 Yes Yes

7.95 FR 3 / HR 1 FR 3 only FR 3 only

7.40 FR 4 / HR 2 Yes FR 4 only

6.70 FR 5 / HR 3 Yes FR 5 only

5.90 FR 6 / HR 4 Yes Yes



AMR FR channels are mapped on 16 kbit/s TRAU frames on the Abis interface whileAMR HR channels are mapped on 8 kbit/s TRAU frames. (GSM standards, however,map HR1 codec, 7.95 kbit/s source bit rate, to 16 kbit/s TRAU frames.)

Radio Interface

The AMR codec and its control operate without any changes to the air-interfacechannel multiplexing. Conventional TCH/F and TCH/H channels are used for full-rateand half-rate channel modes of the AMR codec.

Channel Mode Handover

Channel mode handovers (AMR HR AMR FR) are executed in the same way asexisting intra cell handovers. A new algorithm for determination when and whether toperform an AMR handover is applied.

Code Mode Signaling

Signaling and measurement reporting for codec mode changes (e.g. AMR FRi AMR FR j) are transmitted in-band on the radio interface.

VAD/DTX

Signaling and measurement reporting for codec mode changes are transmitted in-band on the radio interface.




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3.1.2 SBS implementation

Both BTSplus and BTSone support all FR codecs. However, not all AMR HR codecsare supported: Due to static alignment of HR channels on 8 kbit/s TRAU frames,AMR HR codec HR1 (for BTSplus) and AMR HR codecs HR1, HR2 and HR3 (for BTS1) are not supported.

The TRAU equipped with TRAC V7 modules supports all codecs (FR/HR/EFRspeech, data, AMR full rate, AMR half rate, …)

3.1.3 TRAU pooling

For the TRAU pools can be defined for the timeslots of a PCMA:

Parameter Object Range Meaning

DEFPOOLTYP PCMA 0 .. 143 Default pool type

POOLTYP TSLA POOL_NOTDEF,POOL_1,…,POOL_48

Pool type for TSLA (different fromDEFPOOLTYP)

3.1.4 AMR codec adaptation

AMR codec adaptation is done within a restricted set of codec modes (using half-rateor full-rate). This set is called Active Code Set ACS and can be composed of up tofour codec modes.

The dynamic changes between AMR codecs is done according to an adaptationalgorithm without notification or intervention by the BSC. This algorithm is called AMRLink Adaptation. It is based on channel quality measurements performed in the BTSand MS (Quality Indicator is defined in terms of carrier to interference ratio C/I).

For the AMR link adaptation DL the thresholds and the associated hysteresis areadministrable by the parameters given in the following table.

For the AMR link adaptation UL so called reference thresholds for the transitionbetween the possible codec modes are hard-coded.





55

3.1.5 Database parameters

This table contains parameters concerning basic AMR settings (used codec modes,threshold - hysteresis for the active codecs and initial coding mode). In the BSC DBthere are two sets of this parameters with the same meaning that can be configuredindependently. One set is applied for AMR subscribers allocated on hopping andanother on non hopping channels (e.g. FHAMRFRC1 and AMRRFC1 respectively).

Parameter Object Range

(default)

Meaning

AMRFRC1,

AMRFRC2,

AMRFRC3,

AMRFRC4

BTS 1:RATE_01 (4.75 kbit/s),

2:RATE_02 (5.15 kbit/s),

3:RATE_03 (5.90 kbit/s),

4:RATE_04 (6.70 kbit/s),

5:RATE_05 (7.40 kbit/s),

6:RATE_06 (7.95 kbit/s),

7:RATE_07 (10.2 kbit/s),

8:RATE_08 (12.2 kbit/s)

AMR Full Rate Codec no. 1,




AMRFRTH12 Threshold: 0 (0.0 dB)... 63 (31.5dB), step is 0.5 dB;

Default: 7(3,5dB)Hysteresis: 0..15 (7.5 dB)Default: 4 (2dB)

"Threshold-Hysteresis" related to theactive codecs specified in theAMRFRC1 and AMRFRC2

AMRFRTH23 Threshold: 0 ... 63; Default:12(6 dB)

Hysteresis: 0 ... 15(7,5dBDefault: 4(2 dB)5


AMRFRTH34 Threshold: 0 ... 63; Default:23(11,5 dB)

Hysteresis: 0... 15 (7,5dB)Default: 4 ( 2dB)


AMRHRC1

AMRHRC2,

AMRHRC3,

AMRHRC4

1:RATE_01 (4.75 kbit/s),

2:RATE_02 (5.15 kbit/s),

3:RATE_03 (5.90 kbit/s),

4:RATE_04 (6.70 kbit/s),

5:RATE_05 (7.40 kbit/s)

AMR Half Rate Codec no. 1,




AMR Half Rate Codec no. 5

AMRACMRDL HAND 1…63 , Unit=CMR

(5 CMR)

Size of averaging window for CodecMode Requests (CMR)




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Parameter Object Rang

(default)

Meaning

AMRHRTH12 Threshold 0..63

Default: 19 (9,5 dB)

Hysteresis 0..15

Default:4 (2 dB)

"Threshold-Hysteresis" related to theactive codecs specified in theAMRHRC1 and AMRHRC2

AMRHRTH23 Threshold: 0 ... 63

Default: 24 (12 dB)

Hysteresis: 0 ... 15

Default:4 (2 dB)


AMRHRTH34 BTS Threshold: 0 ... 63

Default: 30(15 dB)

Hysteresis: 0 ... 15

Default:4 (2 dB)

Null (BTS One)


For BTS One family these two valuesshould be set as NULL

AMRFRIC BTS 0:START_MODE_FR,

1:CODE_MODE_01,

2:CODE_MODE_02,

3:CODE_MODE_03,4:CODE_MODE_04

Initial FR codec mode (i.e. start modeamong the ACS)

Default:0

AMRHRIC BTS 0:START_MODE_HR,

1:CODE_MODE_01,

2: CODE_MODE_02,

3:CODE_MODE_03,

4:CODE_MODE_04

Initial HR codec mode

Default:0

AMRLKAT BTS Range: 0..200

0 = -10dB,

100 = 0dB,

200 = +10dB

unit: 0.1dB

Default: 100

The AMR link adaptation tuningparameter is used by the AMR UplinkCodec Mode Adaptation in the BTS.

It tunes the transition betweenCODEC modes determined byinternal thresholds. A value higher than the default shifts the transitiontowards higher carrier-to-interferer or signal-to-noise ratios. A value lower than the default has the oppositeeffect. Adaptation of AMR HR andAMR FR is affected simultaneously.





57

The thresholds and hysteresis values indicated in the table (for HR and FR codecmodes, see above) must fulfill the following conditions:

Thr_1 ≤ Thr_2 ≤ Thr_3

Thr_1 + Hys_1 ≤ Thr_2 + Hys_2 ≤ Thr_3 + Hys_3

Parameter Description Range

Thr_1 / 2 / 3 Thr_i gives the "downward" threshold for switching to mode i (from mode i+1)

0 (0.0 dB)... 63(31.5 dB)

Hys_1 / 2 / 3 Hys_i determines the "upward" threshold for switching to mode i+1 (from i, the switch occursat Thr_i+Hyst_i)

0 (0.0 dB)... 15(7.5 dB)

Carrier-to-

interference

ratio C/ICodec_Mode_4

Codec_Mode_3

Codec_Mode_2

Codec_Mode_1

Thr_3 + Hyst_3 = Thr_Mx_Up (3)

Thr_3 = Thr_Mx_Down (4)





Thr Threshold

Hyst Hysteresis

Fig. 24 Threshold and hysteresis determine the switching "up" and "down" between codec modes in downlink




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Complete table of Thresholds and Hysteresis for Link Adaptation

AMR FULL RATE

Rate 1

(4.75

Kb/s)

2

(5.15

Kb/s)

3

(5.90

Kb/s)

4

(6.70

Kb/s)

5

(7.40

Kb/s)

6

(7.95

Kb/s)

7

(10.2

Kb/s)

8

(12.2

Kb/s)

1 (4.75 Kb/s) 4.0 3.5 5.0 5.5 5.0 6.5 7.5

2 (5.15 Kb/s) 3.0 5.0 5.5 5.0 6.5 8.0

3 (5.90 Kb/s) 6.0 6.5 6.0 7.0 8.5

4 (6.70 Kb/s) 7.0 6.0 7.5 9.5

5 (7.40 Kb/s)3.5

8.0 10.5

6 (7.95 Kb/s) 10.0 11.5

7 (10.2 Kb/s) 11.0

8 (12.2 Kb/s)

Table: Default values for the AMR Full Rate Thresholds attributes, table units are in dB so each entry value has to be doubled toobtain the corresponding parameter unit value.

AMR HALF RATE

Rate 1

(4.75 Kb/s)

2

(5.15 Kb/s)

3

(5.90 Kb/s)

4

(6.70 Kb/s)

5

(7.40 Kb/s)

6

(7.95 Kb/s)

1 (4.75 Kb/s) 9.5 11.0 12.0 12.5 13.5

2 (5.15 Kb/s) 12.0 12.5 13.5 14.0

3 (5.90 Kb/s) 13.0 14.5 15.0

4 (6.70 Kb/s) 14.5 15.0

5 (7.40 Kb/s) 16.0

-

Table: Default values for the AMR Half Rate Thresholds attributes, table units are in dB so each entry value has to be doubledto obtain the corresponding parameter unit value





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The AMR link adaptation is based on the quality of the connection. Since a finer scaleis needed than the one RXQUAL offers, C/I is used. The approach to consider C/Ivalues for AMR calls was basically used to achieve a higher resolution of quality

values for AMR link adaptation. PC and HO decisions however are still based on RXQUAL values which are thenmapped into C/I values.

The following mapping between C/I values and RXQUAL values is applied:

RXQUAL C/I RXQUAL C/I

6.88 ... 7 1 3.13 ... 3.37 14

6.63 ... 6.87 2 2.88 ... 3.12 14

6.38 ... 6.62 4 2.63 ... 2.87 15

6.13 ... 6.37 5 2.38 ... 2.62 16

5.88 ... 6.12 6 2.13 ... 2.37 16

5.63 ... 5.87 7 1.88 ... 2.12 17

5.38 ... 5.62 8 1.63 ... 1.87 17

5.13 ... 5.37 8 1.38 ... 1.62 18

4.88 ... 5.12 9 1.13 ... 1.37 18

4.63 ... 4.87 10 0.88 ... 1.12 19

4.38 ... 4.62 11 0.63 ... 0.87 19

4.13 ... 4.37 11 0.38 ... 0.62 19

3.88 ... 4.12 12 0.13 ... 0.37 20

3.63 ... 3.87 13 0 ... 0.12 20

• 3.38 ... 3.62 13




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4 Channel allocation strategy




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4.1 Basic

Allocation of the radio channels is not only based on the best interference band as itwas in early SBS releases but is service dependant.

The Service Dependant Channel Allocation Strategy (SDCA) applied on Um interfaceoffers the possibility to decide the call policy for resource allocation (data callspreferably on BCCH carrier and speech calls on non BCCH carriers or vice versa)and the downgrading strategy (parameter DGRSTRGY) for multislot data calls incase of congestion.

Cell Load Dependent Activation of Half Rate allocates half rate channels only duringhigh traffic peaks in the cell, when additional capacity is needed. The feature can beenabled with the parameter EHRACT within a cell which is configured for dual rate

channels. A threshold HRACTT1 for standard cells and HRACTT2 for extended andconcentric cells is implemented.

If the cell traffic load exceeds the percentage defined by HRACTT1, all incoming callsor incoming handovers, for which HR in the info element (IE) is indicated assupported speech version, are forced to HR. If the cell load is below the percentagedefined by HRACTT1, all incoming calls are forced to FR.

The allocation of half rate channels according to the current cell load is also providedfor AMR half rate codecs with the parameters EHRACTAMR, HRACTAMRT1,HRACTAMRT2 (see chapter 3, section 4.5.3).

Enhanced pairing of HR channels, parameter EPA set on the BSC basis, impliesautomatically triggered forced intracell handovers that fill up dual rate TCHs, carryingonly one HR call, with another HR call.

Enhanced pairing due to Um radio TCH load is triggered if the percentage of dualrate TCHs or full rate TCHs in the BTS in usage state ''idle'' drops below a definablethreshold. This thresholds are based on the parameters EPAT1 in case of standardcell, complete area of a concentric cell and far area of an extended cell, and EPAT2in case of inner area of a concentric cell and near area of an extended cell.

In addition, for circuit switched (CS) services Service Dependant Handover andPower Control was introduced to offer higher flexibility for handover and power control algorithms (parameters SGxHOPAR and SGxPCPAR discussed in chapters 3and 6 respectively).

Further step to improve the Channel Allocation Strategy (SDCA) has been done inthe SBS BR8.0 by introducing the feature “Multi Service Layer Support'.





63

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. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

BR6.0

BR7.0

BR8.0

Service dependent Channel Allocation Strategy (SDCA)

BCCH TRX Packet Switchedtraffic

Downgrade Strategy: HSCSD first

Service dependent Power Control and Handover

Service Group 1

Service Group 2

Service Group 14

Thresholds

Enable / Disable

BTS

Service List:

• CS speech

• Signaling

• GPRS...

Layer 1

Layer 2

Fig. 25 SDCA history




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4.2 Multi Service Layer Support

Operators can split-up the frequency spectrum of their network to supply a variety of services based on their marketing forecast for them.

In order to be able to supply the quality required for a variety of services the networkhas to be designed with different frequency reuse patterns. That means that a cellmay consist of one or more service layers that, in turn, may comprise one or moreTRXs with the same reuse pattern and that provide the same mean quality in termsof C/I.

The “Multi Service Layer Support” feature enables operators to assign the requirednumber of TRXs to the different service layers. This feature distinguishes between upto nine different types of services having different quality demands. These service

types can be assigned to the respective service layers.





65

Service Type Description

Signaling Signaling services only use the Stand Alone DedicatedControl Channel (SDCCH) for signaling purposes, e.g. callsetups, Short Message Service, location updates, LocationServices, etc.

CS SpeechEFR/FR/HR

Denotes circuit switched single slot speech services thatuse the following codecs: Enhanced Full Rate (EFR), FullRate (FR) or Half Rate (HR).

CS Speech AMR FR Denotes circuit switched single slot speech services thatuse the Adaptive Multi-Rate Full Rate codec (AMR FR)

CS Speech AMR HR Denotes circuit switched single slot speech services thatuse the Adaptive Multi-Rate Half Rate codec (AMR HR)

CS Data Performs circuit switched single slot data transfers usingrates up to 9.6 kbit/s or up to 14.4 kbit/s

HSCSD Denotes circuit switched single slot or multislot datatransfers that carry High Speed Circuit Switched DataServices (HSCSD).

GPRS Denotes packet switched single slot or multislot datatransfers that carry General Packet Radio Services (GPRS)on the Packet Data Traffic Channels (PDTCH) that are

either embedded alone or multiplexed in dynamicallyallocated Packet Data Channels (PDCH)

EGPRS Denotes packet switched single slot or multislot datatransfers that carry Enhanced General Packet RadioServices (EGPRS) in Packet Data Traffic Channels(PDTCH) that are either embedded alone or multiplexed indynamically allocated Packet Data Channels (PDCH).

ASCI The Voice Broadcast Services (VBS) of Advanced SpeechCall Items (ASCI) allocate specific channels; e.g. GSM-Railway subscribers (GSM-R) use common voice groupbroadcast channels for Voice Group Call Services (VGCS).




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Two new concepts have been introduced to provide flexible resource allocation - theService Layer that a transceiver belongs to and the Service List SL.

The Service List is a collection of all of the service types supported within a cell and

defines the mapping of the service types onto the Service Layer Lists (SLL). TheService Layer List is a logical entity, i.e. it is not an O&M parameter, that includes allof the Service Layers, one or more, assigned to a particular service and listed indecreasing order of their priority. A certain level of mean radio quality, as a result of radio network planning characterizes a service ‘Layer’ - referred to as ‘Layer’ (LY) inthis document.

The Service List has to be configured per cell. Modification or deletion of the prioritylayers within the SLL can be done for CS service types without interrupting serviceprovisioning, but for PS service types the service is interrupted because the PTPPKFobject has to be locked.

In order to avoid blocking on a layer as long as unused resources are available, it isrecommended to assign the layers to several Service Layer Lists.

NOTE

Please note that service types not included in the SL are not supported in the cell.The system checks network consistencies such as hardware support before enablingor disabling services, i.e. before modifying the ‘Service List’.

Separate Service Lists must be maintained per area in case of dual area cells, i.e.concentric cells using single/dual bands or extended cells. The Service List of thecomplete or far area is referred to as the Service List of the Primary Area. TheService List of the inner or near area is referred to as the Service List of theComplementary Area.

For dual band standard cells, an Service List of the Primary Area belongs to the areathat supports the radio frequency band using the BCCH.

Please note that GPRS is not available in specific cell areas, e.g. in the inner areas of concentric cell structures, although both dual band standard cell areas support it.

EGPRS needs transceivers that are capable of satisfying its service requirements.

Resource allocation:

On receiving a request for a particular service, the system reads the SL of the cell tocheck its resources. If it contains the relevant service type, the system searchesthrough the resources in the first layer of the relevant SLL. If there are no resourcesavailable in the highest priority layer, the system checks the next layer of that SLLand so forth. Thus, services may be temporarily allocated on a layer other than thehighest prior layer.

Therefore, a resource reallocation procedure is periodically triggered to move such

CSC calls into a more appropriate layer as soon as possible.





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Service List

Service 1(e.g. signaling)

Service 2(e.g. GPRS)

Service 3(e.g. cs data)

Service 4

(e.g. cs speech)

Layer 1

Layer 2

Layer 3

TRX 0

TRX 1

TRX 2

TRX 3

TRX 4

TRX 5

List of all or

selected of the 9

service types

Service layer list defined per

service, e.g.

signaling -> LY1

GPRS -> LY1, LY2

cs data -> LY2, LY1

cs speech -> LY3, LY2, LY1

TRX with same expected C/I

are assigned to layers, e.g.

LY 1 -> TRX 0

LY 2 -> TRX 1, TRX 2

LY 3 -> TRX 3, TRX 4, TRX 5

Fig. 26 Allocation example




MN1789EU11MN_0002

© 2005 Siemens AG

68

4.2.1.1 Service Layer List

The Service Layer List contains radio channels of one or several TRXs with expected

the same quality and the same characteristics. Each TRX in the BTS will beassociated to a layer via O&M. The selection of the appropriate layer LYn andgrouping layers in the SLL for each service will be performed on the Radio Networkplanning and customer consideration basis.

SLL0 is default for signaling services. SLL1 is created for data services requiringhigher quality. SLL2 is designed for less demanding services.

After creation of SL and SLL, resources assignment table can be created.

By default LY0 is reserved for signaling services.

4.2.1.2 New parameters related to the Multi Service Layer Support andsome changes in the BSC DB

In the BSC DB object (SET) BTS the new attributes xLLPRM and xLLCOM related tothe Service List Primary and Complementary respectively (x stands in this documentfor different services like S for signaling, AMRFR, AMRHR, SCRTSWD for circuitswitched data, CRTSWSPE speech, EDGE, GPRS and HSCSD) are introduced.

In the BSC DB object TRX a new attribute LAYER ASSIGNED (LYn where n=0…11)is introduced.

GSUP parameter in TRX is no longer supported.

CPOLICY is also no longer supported as the service layer concept is introduced.

DGRSTRGY is from the BSC object moved to the BTS object.





69

4.3 Database parameters


(default)

Meaning

DGRSTRGY BTS HSCSD_FIRST_DOWNGRADE,GPRS_FIRST_DOWNGRADE,DOWNGRADE_HSCSD _ONLY,DOWNGRADE_GPRS_ ONLY,NO_DOWNGRADE(NO_DOWNGRADE)

Downgrade strategy

<x>LLPRM BTS LY_00,

LY_01,…

LY_11,

(NULL)

Primary Service List for thecorresponding service.

X = AMRFR, AMRHR, ASCI, S,CRTSWD,CRTSWSPE, E, G, HSCSD.

Multiple selection possible

<x>LLCOM BTS LY_00,

LY_01,…

LY_11,

(NULL)

Complementary Service List for

the corresponding service.

X = AMRFR, AMRHR, ASCI, S,CRTSWD,CRTSWSPE, E, G, HSCSD.

Multiple selection possible

LAYERID TRX LY_00,

LY_01,… LY_11,

(NULL)

Specification of the group of theradio resources the TRX belongsto

EPA BSC TRUE, FALSE (FALSE) Enable HR channels pairing

EPAT1 BTS 0…10000,

unit:0,01%

(4000)

Enhanced pairing threshold 1indicates the percentage of busyTCHs in a standard cell or complete area of a concentric cellor far area of an extended cell




MN1789EU11MN_0002

© 2005 Siemens AG

70


(default)

Meaning

EPAT2 BTS 0…10000,

unit:0,01%

(4000)

Enhanced pairing threshold 2indicates the percentage of busyTCH of the inner area of aconcentric cell or near area of anextended cell

EHRACT BTS TRUE, FALSE

(FALSE)

Enable cell load dependent HRactivation

HRACTT1 BTS 0 ... 10000

(default 6000,)

Threshold 1 for HR activation:percentage of busy TCH in astandard cell or complete area of aconcentric cell or far area of anextended cell

HRACTT2 BTS 0 ... 10000

(default 6000)

Threshold 2 for HR activation:percentage of busy TCH for theinner area of a concentric cell or near area of an extended cell





71

t

5 Exercises




MN1789EU11MN_0002

© 2005 Siemens AG

72

Exercise 1

Title: Creation of a RFC in the SBS

Task

The object in the SBS configuration language specifying a RFC is called TRX(transceiver).

Take the UMN: BSC-CML (User Manual: BSC command manual) and check therequired input parameters.





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MN1789EU11MN_0002

© 2005 Siemens AG

74

Exercise 2

Title: Dimensioning control channels of an extended cell

Task

Given an extended cell with 2 carriers.

In this cell, 3 channels with extended_mode = true are required.

Assume Erlang B and the following values:

Typical SDCCH load per subscriber and hour: 8 mErl.

Typical TCH load per subscriber and hour: 25 mErl.Blocking probability 1%.

Determine the control channel configuration which offers highest capacity.





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MN1789EU11MN_0002

© 2005 Siemens AG

76

Exercise 3

Title: Determining the highest "Trunking Gain" for the system

Task

By using Erlang B-traffic model table (chapter 9, page 45) compare the "Trunkinggain" in the operator's network composed of:

• an Erlang B system with 36 trunks

• 2 Erlang B systems with 18 trunks each

• 4 Erlang B systems with 9 trunks each

Which solution gives the highest offered traffic (trunking gain) if 1% blocking isassumed in all cases?





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MN1789EU11MN_0002

© 2005 Siemens AG

78

Exercise 4

Title: SS7 signaling load per BSC and needed number of CCSS7links per BSC

Task

Assume the standard profile subscriber that makes signaling load of 900byte, BSCsystem of 3500Erlang traffic capacity and traffic load per subscriber 25mErlang.

Calculate the total signaling load in the system and the number of needed CCSS7links.





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MN1789EU11MN_0002

© 2005 Siemens AG

80

Exercise 5

Title: Configuration of the Multi Service Layer in the given BTS

Task

Given an standard cell with 3carriers. TRX0 is the BCCH carrier

The BTS should support Signaling, CS speech, GPRS and HSCSH.

Create the service list for the given services in the BTS.





81

6 Solutions




MN1789EU11MN_0002

© 2005 Siemens AG

82

Solution 1

Title: Creation of a RFC in the SBS

Task

CREATE TRX:NAME=BTSM:0/BTS:0/TRX:1, TRXFREQ=CALLF05, PWRRED=0,RADIOMR=OFF, RADIOMG=254, MOEC=TRUE, TRXAREA=NONE, LPDLMN=0,;TRXMD=GSM; LAYERID=LY_02; USFGRAN=DISABLED;

The parameters are specified as following:

BTSM: BTS site manager number 0 ... 199

BTS: Number of sector/site 0 ... 11, 23 Pico

TRX: TRX number to the related cell 0 ... 23

TRXFREQ: TRX-frequency - ARFCN BCCHFREQ,CALLF01,

CALLF02,:

CALLF63

PWRRED: Power reduction [0...12 dB in steps of 2 dB] for

decrease max. transmit power

0 ... 6

RADIOMR: Radio measurement reports from TRXto the BSC ON / OFF

RADIOMG: Granularity of radio measurement reports insteps of 1 SACCH multiframe

0 ... 254

MOEC Member of emergency configuration TRUE / FALSE

TRXAREA: Configuration of concentric cells NONE /COMPLETE /INNER

LPDLM Number of LAPD link 0 ... 10

TRXMD TRX is associated to the GSM or EDGE CU GSM / EDGE

USFGRAN Flexible USF granularity ENABLED/

DISABLED





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MN1789EU11MN_0002

© 2005 Siemens AG

84

Solution 2

Title: Dimensioning control channels of an extended cell

Task

Example configuration A:

1 BCCH combined (containing 4 SDCCH subslots), extmode must be true!

3 TCH_full, extmode = true

2 carriers

NTCH = 11, ATCH = 5.16 Erl, B = 0.01 206 subscribers

NSDCCH = 4, ASDCCH = 0.87 Erl, B = 0.01 108 subscribers

Configuration A is SDCCH limited to 108 subscribers.

Example configuration B:

1 BCCH uncombined, extmode must be true!

1 SDCCH timeslot (containing 8 SDCCH subslots), extmode must be true!

3 TCH_full, extmode = true

2 carriers

NTCH = 9, ATCH = 3.78 Erl, B = 0.01 151 subscribers

NSDCCH = 8, ASDCCH = 3.13 Erl, B = 0.01 391 subscribers

Configuration B is TCH limited to 151 subscribers.

Configuration B offers higher capacity.





85

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MN1789EU11MN_0002

© 2005 Siemens AG

86

Solution 3

Title: Determining the highest "Trunking Gain" for the operator'ssystem

Task

The offered traffic for the given number of trunks and blocking is:

• 25.51 Erlang if the operator uses only 1 system with 36 trunks

• 2x 10.44=20.88Erlang if the operator uses 2 systems with 18 trunks each

• 4x3.78=15.12 Erlang if the operator uses 4 systems with 9 trunks each.

Obviously the highest trunking gain is obtained by using the available number of trunks in one system only.





87

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MN1789EU11MN_0002

© 2005 Siemens AG

88

Solution 4

Title: SS7 signaling load per BSC and needed number of CCSS7links per BSC

Task

Number of the subscriber in the system is defined as:

Number of subscribers=Traffic capacity of the system/traffic per subscriber

Thus for the given values the number of subscribers is:

Number of subscribers=3500Erlang/25mErlang=140 000.

Total signaling load made by all subscribers is in 1h observation period is:

Total signaling load=Number of subscribes*signaling load per subscriber/1h , i.e.

Total signaling load=140 000*900byte/3600s= 35kbyte/s.

CCSS7 link single capacity is 64kbit/s=8kbyte/s.

Thus needed number of signaling links to handle offered signaling load is 5 asobtained from:

35kbyte/s : 8kbyte/s=4,37 .





89

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MN1789EU11MN_0002

© 2005 Siemens AG

90

Solution 5

Title: Configuration of the Multi Service Layer in the given BTS

Task

The first step is to define in the TRX object the layers.

BCCH TRX should be defined as LY0 (best expected quality)

The other two TRXs we define as LY1 (normal quality).

Therefore three available TRXs are building 2 Layers:

• LY0 (BCCH TRX)

• LY1 (TRX1, TRX2)

Then SLL can be created. The position of the service in the service list correspondsto the service priority:

• SLL0 (LY0)

• SLL1 (LY0, LY1)

• SLL2 (LY1, LY0)

It means that for SLL0 services will be allocated on BCCH TRX only.

For SLL1 system will look for a channel on BCCH TRX, and in case of channelcongested will search for a TCH of TRX1 and TRX2.

For SLL2 the services allocation will take place on TCHs of TRX1 and TRX2 and incase of congestion on BCCH TRX.





91

HSCSD4

GPRS3

CS speech2

Signaling (SDCCH)1

Service TypePriority

SLL2 (LY1, LY0)HSCSD4

SLL1 (LY0, LY1)GPRS3

SLL2 (LY1, LY0)CS speech2

SLL0 (LY0)Signaling (SDCCH)1

SLLService TypePriority

Fig. 27 Service List and Service Layer List

Service List

Service 1(signaling)

Service 2(speech)

Service 3(GPRS)

Service 4(HSCSD)

Layer0

Layer1

TRX 0

TRX 1

TRX 2

List of services

supported in the

cell

Service layer list defined per

service, e.g.

signaling -> LY0

GPRS -> LY0&LY1

speech -> LY1& LY0

HSCSD -> LY1& LY0,

TRX with same expected C/I

are assigned to layers, e.g.

LY0-> TRX 0

LY1 -> TRX 1, TRX 2

Fig. 28 Services supported in the cell by available TRXs




TRX:NAME=BTSM:0/BTS:0/TRX:0,TRXFREQ=BCCHFREQ,PWRRED=0,RADIOMR=ON,RADIOMG=2,MOEC=TRUE,TRXAREA=NONE,LPDLMN=0,TRXMD=GS

M,MAIO=<NULL>,FHSYID=<NULL>,LAYERID=LY_00,USFGRAN=DISABLED;

TRX:NAME=BTSM:0/BTS:0/TRX:1,TRXFREQ=CALLF01,PWRRED=0,RADIOMR

=ON,RADIOMG=2,MOEC=TRUE,TRXAREA=NONE,LPDLMN=0,TRXMD=GSM,M

AIO=<NULL>,FHSYID=<NULL>,LAYERID=LY_01,USFGRAN=DISABLED;

TRX:NAME=BTSM:0/BTS:0/TRX:2,TRXFREQ=CALLF02,PWRRED=0,RADIOMR

=ON,RADIOMG=2,MOEC=TRUE,TRXAREA=NONE,LPDLMN=0,TRXMD=GSM,M

AIO=<NULL>,FHSYID=<NULL>,LAYERID=LY_01,USFGRAN=DISABLED;

BTS:NAME=BTSM:0/BTS:0, SLLPRM=LY_00,CRTSWSPELLPRM=LY_01&LY_00,GPRSLLPRM= LY_00&LY_01,

HSCSDLLPRM=LY_01& LY_00…;

Fig. 29 Database entry example

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01 Mn1789eu11mn 0002 Channel Configuration