Sdcch

Know More - SDCCH

Nov 17, 2003

S. Rajshekhar Deshraj

Contents • Channel Concepts • Call Setup • Burst & Multi Frames • Mapping of Logical Channels • Definitions of SDCCH • Usage of SDCCH in the GSM network (BSC) • Possible SDCCH Configuration • SDCCH Holding Time Nov 17, 2003

S. Rajshekhar Deshraj

Contents • SDCCH Traffic Estimations • SDCCH Congestion • Reasons for SDCCH congestion • How to detect SDCCH congestions • Preventive actions to avoid SDCCH congestions • SDCCH Dimensioning • Parameters for SDCCH Dimensioning • Counters & Report Analysis Nov 17, 2003

S. Rajshekhar Deshraj

Logical Channels

Nov 17, 2003

S. Rajshekhar Deshraj

Broadcast Channels (BCH) Frequency Correction Channel (FCCH) •Downlink Channel •BTS: Transmits a carrier frequency (Pure sine wave of 67.7 KHz) This Solve 2 purpose : a> Make sure that this is BCCH Carrier b> To allow the MS to synchronize to the frequency •MS: After Switch on MS Scan for this channel, since it has no information to which frequency to use. FCCH carrier enables a mobile to tune its frequency to that being broadcast by the BTS.

Nov 17, 2003

Broadcast Channels (BCH)

Syncronization Channel (SCH) •Downlink Channels •BTS: Transmits TDMA Frame number + Base Station Identity Code (BSIC= NCC + BCC ) •MS: MS decodes the BSIC if the chosen BTS is GSM Base station within a cell

Nov 17, 2003

Broadcast Channels (BCH) •Broadcast Control Channel (BCCH) •Downlink Channels •BCCH contains the detailed Network and cell specific information such as : •Frequency used by Cell and its Neighboring cells. •Frequency HSN •Paging Groups •LAI •Max output power allowed in the cell

Nov 17, 2003

Common Control Channels (CCCH)

Paging Channel (PCH) •Downlink Channels • BTS: Broadcast the paging message to indicate the Incoming Calls or Incoming SMS. Paging message also includes the MS’s identity number IMSI/TMSI • MS: MS listens to the PCH. If it identifies its own mobile subscriber identity number on the PCH, it will respond.

Nov 17, 2003

Common Control Channels (CCCH) Random Access Channel (RACH) •RACH is transmitted Uplink only •When mobile is paged , it replies on RACH requesting a signaling channel. •RACH can also used if the MS wants to make a contact the NW/ Originating calls

Nov 17, 2003

Common Control Channels (CCCH)

Access Grant Channel (AGCH) •Downlink channel •AGCH is answer to the RACH •NW assigns a signaling channel (SDCCH) to the MS. This assignment is performed on the AGCH

Nov 17, 2003

Dedicated Control Channels (DCCH) Stand Alone Dedicated Control Channel (SDCCH) •SDCCH is bi-directional Channel •System Signaling •Call Setup •Authentication •Location Update •Assignment of Traffic channels and •Transmission of Short messages Nov 17, 2003

Dedicated Control Channels (DCCH) Slow Associated Control Channel (SACCH) •SACCH is transmitted in both Uplink and Downlink directions •SACCH is associated with each SDCCH and also with TCH •Uplink : MS Sends the averaged measurement on its own BTS and neighboring BTS’s •Downlink: MS receives information regarding information concerning •Transmit power to use •Instructions on Timing Advance

Nov 17, 2003

Dedicated Control Channels (DCCH) Fast Associated Control Channel (FACCH) •While Calls in progress and HO is required FACCH is used •FACCH works in Stealing mode meaning that one 20ms segment of speech is exchanged for signaling information necessary for the HO

Cell Broadcast Channel (CBCH) •CBCH is used in Downlink only •It is used to carry Short Message Service Cell Broadcast (SMSCB) and uses the same physical channel as the SDCCH

Nov 17, 2003

Traffic Channels (TCH) Traffic channels are Bi-directional logical channel that transfer the user speech or data. •Full Rate TCH ( TCH/F) : •This channel carries information at a gross rate at 13Kbit/s * * Now it is 22.8 Kbit/s with latest R9.1 •Half Rate TCH (TCH/H) : •This Channel carried information at a gross rate at 6.5Kbit/s* * Now it is 11.4 Kbit/s with latest R9.1 •Enhance Full Rate : •The speech coding in EFR is still done at 13Kbit/s, but the coding mechanism is different that is used for normal FR. EFR gives better speech quality at the same bit rate than normal FR.

Nov 17, 2003

Call to an MS

More.. Nov 17, 2003

S. Rajshekhar Deshraj

Relationship Between Burst & Frame Burst

: Physical content of a TS is called Burst.There are 5 types of Bursts each having 15/26 ms duration and 156.25 Bits.

Hyperframe: In GSM system every TDMA frame is assigned a fixed number, which repeats itself in a time period of 3 HOURS 28 MINUTES 53 SECONDS 760 MILLISECONDS. This time period is referred to as Hyperframe. Superframe : =51x26 Multiframes. So, Duration =51x26x8x15/26=6Sec 120ms Multiframe :There are two types of multiframe. 26 TDMA Frame Multiframe :Used to carry TCH, SACCH and FACCH Duration =26 x 8 x 15/26 =120ms 51 TDMA Frame Multiframe : Used to carry BCCH,CCCH,SDCCH and SACCH. Duration =51 x 8 x 15/26 =235.38ms Nov 17, 2003

S. Rajshekhar Deshraj

TDMA frames with Common and Dedicated Channels

Nov 17, 2003

Bursts Normal Bursts: This burst is used to carry information on

:

•Traffic channel •SDCCH Channel •Broadcast Control Channel •Paging Channel •Access Grant Channel •SACCH & FACCH Channel 1 Time slot = 156.25 bits durations (15/26 = 0.577 ms ) TB Encrypted bits 3 57

F

Training Sequence F 26

Encrypted bits TB 57 3

GP 8.25

F : One Stealing Bit:=0 Indicates 57bit packet contains user data or speech :=1 Indicates burst stolen for FACCH Signalling RxQual derived from the 26 bit midable from the TDMA frame

Nov 17, 2003

Bursts Frequency Bursts: All 148 bits(142+6) are coded with 0. The output of GMSK Modulator is a fixed frequency signal exactly 67.7 Khz above the BCCH carrier frequency. Thus the MS on receiving this fixed frequency signal fine tunes to the BCCH frequency and waits for the Sync burst to arrive after 1 TDMA Frame .i.e =15/26*8=4.615ms 1 Time slot = 156.25 bits durations (15/26 = 0.577 ms ) TB 3

Nov 17, 2003

ALL ZERO 142 BITS

TB 3

GP 8.25

Bursts Synchronization Bursts: This burst is used for time synchronization of the MS

1 Time slot = 156.25 bits durations (15/26 = 0.577 ms ) TB 3

SCH DATA 39 Bits

Extended Training Sequence 64 Bits

SCH DATA 39 Bits

TB 3

GP 8.25

39Bit x 2=78 Bits :Are decoded to arrive 25-SCH control bits and that contains the information of the NCC ,BCC & TDMA FN 64 Bits : Long training seq. of 64 Bits are identical for all BTS

Nov 17, 2003

Bursts Access Bursts: This burst is used only for initial access by the MS to the BTS which applies 2 cases : •For connection setup when idle state where a CHAN_REQ message is sent using access burst •For HO when MS send HND_ACC message. 1 Time slot = 156.25 bits durations (15/26 = 0.577 ms ) TB 8

SCH Sequence 41 Bits

RACH Data 36 Bits

TB 3

Guard Band 68.25 Bits

36Bit Contains : BSIC+CHAN_REQ or HND_ACC 41Bit Contains : Fixed bit sequence allow BTS to recognize it is Access Burst 86.25 bits GP: Long GP enables BTS to get Propagation delay information. Nov 17, 2003

Bursts Dummy Bursts: To enable the BCCH frequency to be transmitted with a constant power level, dummy burst are inserted. This burst is transmitted on CHGR=0 when no other type of burst is to be sent. Thus it makes possible for MS to perform the power measurement on the BTS in order to determine which BTS to use for initial access or which to use for HO

CCCH is replaced by the dummy page, when there is no paging message to transmit. 1 Time slot = 156.25 bits durations (15/26 = 0.577 ms ) TB 3

Mixed Bits 58

Training Sequence 26

Mixed Bits 58

TB Guard Band 3 8.25

58Bits: Coded with pseudo random bit seq. to prevent confusion with Freq correction burst

Nov 17, 2003

Mapping of Logical Channel Method of transmitting logical channels onto physical channel is called Mapping

FCCH+SCH+BCCH+CCCH: An idle MS search for the FCH. When MS finds the frequency correction burst it knows that this is TS 0 on CHGR=0 The cycle means F,S,B repeats after the Idle frame I.e. at Frame no 50. Cycle=51TS TS=0 / CHGR=0 0

1

DOWNLINK 7

0

F0 F1 F2-F5 F6-9 TS-0 F S BCCH CCCH

F10 F

1

7

0

1

7

F11 F12-F15 F16-19 F20-23 F24 F25 F26-29 F30 F31 F32-F35 F36-F39 F40 F41 F42-F45 F46-49 F50 S BCCH CCCH CCCH F S CCCH F S CCCH CCCH F S CCCH CCCH I

F: FCCH 1 TS ( Use 4 Slots in each 51 TDMA Frame) S: SCH 1 TS ( Use 4 Slots in each 51 TDMA Frame) I: IDLE 1 TS BCCH 4 TS CCCH 4 TS (PCH or AGCH) Paging Block 51 TDMA Frame = 9 Paging Blocks TS=0 / CHGR=0 F0 F1 TS-0 R

R

UPLINK

F3

F3

F4

F5

F6

F7

F8

F9 F10

R

R

R

R

R

R

R

R

R: RACH 1 TS

Nov 17, 2003

R

F46 F47 R

R

F48

F49

F50

R

R

R

Mapping of Logical Channel SDCCH+SACCH:

Cycle=102 TS This sequence is repeated after last idle frame.

The Uplink & Downlink pattern are time shifted, so SDCCH sub channel is sent in frame 0-3 on downlink and in frame 15-18 on uplink. The reason for this is to achieve efficient communication, by giving MS time to calculate its answer to the request received on down link SDCCH TS=2 / CHGR=0 1

2

3

F0-F3

F4-F7

F8-F11

1

2

F12-F15

F16-F19

3

1

2

3

7

F20-F23 F24-F27 F28-F31 F32-F35 F36-F39 F40-F43 F44-F47 F48 F49 F50

SDCCH0 SDCCH1 SDCCH2 SDCCH3 SDCCH4 SDCCH5 SDCCH6 SDCCH7 SACCH0 SACCH1 SACCH2 SACCH3

I

I

I

SDCCH0 SDCCH1 SDCCH2 SDCCH3 SDCCH4 SDCCH5 SDCCH6 SDCCH7 SACCH4 SACCH5 SACCH6 SACCH7

I

I

I

TS=2 / CHGR=0

I:

1

DOWNLINK

2

3

F0-F3

F4-F7

UPLINK

IDLE 1 TS SDCCH1 4 TS 2 SACCH 4 TS

F8-F11

3

1

2

3

7

F12 F13 F14 F15-F18 F19-F22 F23-F26 F27-F30 F31-F34 F35-F38 F39-F42 F43-F46 F47-F50

SACCH5 SACCH6 SACCH7

I

I

I

SDCCH0 SDCCH1 SDCCH2 SDCCH3 SDCCH4 SDCCH5 SDCCH6 SDCCH7 SACCH0

SACCH1 SACCH2 SACCH3

I

I

I

SDCCH0 SDCCH1 SDCCH2 SDCCH3 SDCCH4 SDCCH5 SDCCH6 SDCCH7 SACCH4

I:

IDLE 1 TS SDCCH 4 TS SACCH 4 TS

Nov 17, 2003

Mapping of Logical Channel TCH+SACCH: 0&2 used by control channels. This leaves TS-1and 3-7 free for the use by TCHs. Repetition time (Cycle) =26 Frames .i.e. =26*8*(15/26)=120ms Every 13th TS contains SACCH. Downlink contains TA value and Uplink contains measuring report.

TS=1 / CHGR=0 DOWNLINK 0

1

2

F0

F1

T

T

7

0

1

F2

F3

F4 F5 F6 F7 F8 F9 F10 F11 F12 F13 F14 F15 F16 F17 F18 F19 F20 F21 F22 F23 F24 F25 F26

T

T

T

T

T: TCH 1 TS A: SACCH

Nov 17, 2003

0

T

T

1

T

2

T

7

T

T

A

T

T

T

T

T

T

T

T

T

T

T

T

T

I

Usage of SDCCH The SDCCH are used in some different ways in the GSM network: • Registrations: Periodic Location Updates, IMSI Attach/Detach • Call Setup: Immediate Assignment -> Assignment. • SMS point-to-point: SMS messages to/from MS in Idle mode. • Fax Setup • Optional: USSD (Unstructured Supplementary Service Data) data transfer. MS<->Network. Similar to SMS. Controlled by the MSC.

Nov 17, 2003

Possible Configurations SDCCH/8 : 8 Sub channels for signaling are mapped on 1 TS, this results 1 less TCH for the cell. SDCCH/4 (Combining BCCH and SDCCH) :4 Sub channels for signaling are mapped on BCCH TS. As a result Paging capacity on BCCH is reduced by 1/3. CBCH : If CBCH is active 1 sub channel of SDCCH is replaced by 1 CBCH channel.

Limitations : SDCCH/8 in a cell = Number of TRX’s CONFIGURATIONS

SDCCH/4 SDCCH/4+CBCH SDCCH/8 SDCCH/8+CBCH SDCCH/4+SDCCH/8 SDCCH/4+SDCCH/8+CBCH SDCCH/4+SDCCH/8+SDCCH/8 SDCCH/4+SDCCH/8+SDCCH/8+CBCH

Nov 17, 2003

HYD007A 1 TRX SDCCH TCH 4 7 3 7 8 6 7 6 12 6 11 6 X X X X

HYD006A 2 TRX SDCCH TCH 4 15 3 15 8 14 7 14 12 14 11 14 20 13 19 13

Possible Configurations -BCCH COMBC+CBCH

Nov 17, 2003

CELL

BCCH

CBCH

SDCCH

NOOFTCH

HYD007A

1

1

3

7

CHGR CHBAND

BPC CHANNEL

0

4590 SDCCH-28646

BUSY

SDCCH-28645

IDLE

CBCH-34305

BUSY

SDCCH-28644

IDLE

BCCH-34797

BUSY

CHRATE SPV

4496 TCH-4629

FR

1,2

IDLE

4497 TCH-4630

FR

1,2

IDLE

4499 TCH-4631

FR

1,2

IDLE

4505 TCH-4654 FR

1,2

IDLE

4506 TCH-4655

FR

1,2

IDLE

4509 TCH-4661

FR

1,2

IDLE

4575 TCH-4670

FR

1,2

IDLE

STATE ICMBAND

Possible Configurations -BCCH NCOMB+CBCH CELL

BCCH

CBCH

SDCCH

NOOFTCH

HYD006A

1

1

7

14

CHGR 0

CHGR 1

Nov 17, 2003

BPC

CHANNEL

CHRATE SPV

STATE ICMBAND CHBAND 64K

6899 SDCCH-27810

IDLE

SDCCH-27809

IDLE

CBCH-34619

BUSY

SDCCH-27808

IDLE

SDCCH-27807

IDLE

SDCCH-27806

IDLE

SDCCH-27805

IDLE

SDCCH-27804

IDLE

6900

BCCH-34804

BUSY

6887

TCH-1242

FR

1,2

IDLE

NONE

6888

TCH-1243

FR

1,2

IDLE

NONE

6891

TCH-1246

FR

1,2

IDLE

NONE

6893 TCH-1248

FR

1,2

IDLE

NONE

6895 TCH-1250

FR

1,2

BUSY

NONE

6897 TCH-1252

FR

1,2

IDLE

NONE

BPC

CHANNEL

CHRATE SPV

STATE ICMBAND CHBAND 64K

6885 TCH-1240

FR

1,2

BUSY

NONE

6886 TCH-1241

FR

1,2

IDLE

NONE

6889 TCH-1244

FR

1,2

IDLE

NONE

6890 TCH-1245

FR

1,2

IDLE

NONE

6892 TCH-1247

FR

1,2

IDLE

NONE

6894 TCH-1249

FR

1,2

BUSY

NONE

6896 TCH-1251

FR

1,2

IDLE

NONE

6898 TCH-1253

FR

1,2

IDLE

NONE

SDCCH Congestion SDCCH congestion: All SDCCH in a cell are at the same time busy for a period of time which leads to rejection for new MS.

Reasons : • Hanging SDCCH: Are SDCCH that are hanging busy and unusable for a long time (many minutes or indefinite). Hanging SDCCH are generally caused by SW faults.

• Heavily used SDCCH: SDCCH seen as continuously busy even though they are used by different MS and thus carries traffic. It may cause due to : > Extreme end-user behaviors: Sport event ending, festivals or celebrations. > Increased mean hold time of the SDCCH: Mean hold time increase from 2 to 10 seconds can give SDCCH congestion.

Nov 17, 2003

SDCCH Holding Time Normal Location Updating = 3.5 Sec Periodic Registration

= 3.5 Sec

IMSI Attach IMSI Detach

= 3.5 Sec = 2.9 Sec (IMSI detach Indication message sent to NW, no authentication is performed (which normally takes 0.6Sec) & no ack is sent to MS.)

Call Setup

= 2.7 Sec (MOC) = 2.9 Sec (MTC)

Short Message Service(SMS) = 6.2 Sec (Vary depending the length of SMS) Fax Transmission

= 2.7 Sec (MOC) = 2.9 Sec (MTC)

False Access

= 1.8 Sec (when Channel req is rec’d by system ,as SDCCH is allocated by sending Imm Ass message, and the system waits a certain time before performing disconnection.)

Nov 17, 2003

SDCCH Traffic Estimations Normal Location Update:

Mean Holding time No of Location update

=3.5 Sec =1.0 per sub and BH

AC: Avg No of Location updates =1000X(1 X 3.5)/3600=0.972 mE/Sub IC : No Location updating at all =1000X(0 X 3.5)/3600=0 mE/Sub BC: 3 times the Avg no of Location updates =1000X(3 X 3.5)/3600=2.916mE/Sub SMS:

Mean Holding time No of SMS submitted

=6.2 Sec =1.0 per Sub and BH

Traffic : 1000 X (1.0 X 6.2) / 3600 =1.7 mE/sub Call Setup:

Mean Holding time =2.7 Sec(MOC) & 2.9 Sec(MTC) Mob Originating Traffic (Incl B Ans) =0.8 BHCA Mob Terminating Traffic (Incl B Ans) =0.4 BHCA

Traffic : 1000 X {(0.8 X 2.7)+(0.4 X 2.9)} / 3600 =0.9 mE/sub Nov 17, 2003

Reasons for SDCCH congestion Increased mean hold time of SDCCH can be caused by: • Too low signal strength at access to the system Due to LSS MS will be lost communication with the system, This will lead to timeout in the BSC (RLINKT ), and thus the SDCCH is used until timeout. Increase ACCMIN.

• Congestion of TCH/TRA/RALT Will increase CP execution time before rejecting Imm Ass. Minor increase in mean hold time expected.

• C7 problems to MSC (or TRC) In case of C7 signalling problems (SCCP) towards MSC (and/or TRC) can lead to timeout on SCCP connection setup. This will lead to more than 2 minutes hold time for SDCCH.

• Handover on SDCCH Handover on SDCCH will in itself increase mean hold time on SDCCH. However minor increase is expected.

Nov 17, 2003

Reasons for SDCCH congestion

• Congestion on Air-interface Congestion on Air-interface leads to delay in communication to the MS. Can give timeout in BSC during Imm Ass.Increases SDCCH mean hold time with more than 2 seconds.

• Congestion on Abis (LAPD link) Congestion on Abis leads to delay in communication with BTS and MS. Can give timeout in BSC during channel activation (TCHACTIVE). Increase SDCCH mean hold time with more than 5 seconds..

• Congestion on A-interface Congestion on the A-interface will lead to increased mean hold time on SDCCH. Increase is unknown.

• High load in MSC/VLR or HLR High load in MSC/VLR and/or HLR will lead to increased mean hold time on SDCCH. Increase is unknown.

Nov 17, 2003

How to detect SDCCH congestion in the BSC There is no good way to detect SDCCH congestion in real time in the BSC!

A number of symptoms to look for: • Increased CP Load. • Decreased usage of TRA devices. • Location Updates fails => Mobile terminating calls does not reach the subscriber. • Subscriber complaints. Can not access the system. • STS counters . Object type: CLSDCCH and CLSDCCHO. • Seizure Supervision of LCHs (but only for Hanging SDCCHs!)

Nov 17, 2003

Preventive actions to avoid SDCCH congestion • Avoid combined BCCH in cells with many SDCCHs

• Use the optional feature Adaptive Configuration of SDCCHs (ACLC) • Use USSD (Unstructured Supplementary Service data) with care, can cause long meanhold time on SDCCH. • Avoid Handover on SDCCH • Proper Dimensioning of the TCHs and TRA devices in the BSC. • Use recommended values for Periodic Location Updates Avoid unnecessary Periodic Location Updates : BSC: T3212 (RLSBC) = 40 (4 hours) MSC: BTDM (MGIDI) = 240 (4 hours) MSC: GTDM (MGIDI) = 6 (6 minutes) • Use Immediate Assignment on TCH. • Increases the no of SDCCH in a Cell where SDCCH load is high Nov 17, 2003

SDCCH Dimensioning SDCCH Dimensioning is a compromise between SDCCH blocking rate and TCH Capacity. In order to have a successful call setup there has to be an available SDCCH as well as available TCH. Basic SDCCH configuration: It is recommended to choose 1 SDCCH/8 as the basic configuration for all the cells, If LA> 2100 Erlang (500 TRX) 1 SDCCH/4 as the basic configuration for all the cells, If LA< 2100 Erlang (500 TRX)

Nov 17, 2003

SDCCH Dimensioning Automatic SDCCH dimensioning: This can be done with optional Adaptive Configuration of Logical Channel feature. This feature will add extra SDCCH/8 by reconfiguring idle TCH when SDCCH load is high, and revert back to TCH if SDCCH load goes down. Manual SDCCH Dimensioning : •Monitoring SDCCH / TCH Traffic in a cell •SDCCH/TCH load ratio •SDCCH Grade of Service:- Max allowed TCH GOS % = 2 % The rule of Thumb says: SDCCH/4 : Max. SDCCH GOS =1/2 * 2= 1 % SDCCH/8 : Max. SDCCH GOS =1/4 * 2= 0.5% Nov 17, 2003

SDCCH Dimensioning Immediate Assignment on TCH: In case of this feature on the channel administration assigns TCH for signaling instead of an SDCCH, based on 7 different channels allocation strategies (CHAPs) TCH first strategy : Decreases the SDCCH load and enable to use SDCCH/4 in all the cells Traffic load on TCH will in this case increases substantially so this strategy is not recommended. SDCCH first strategy : SDCCH is always allocated first if available, otherwise signaling is performed on TCH.

Nov 17, 2003

SDCCH Dimensioning Example : ASSUME: CELL=3TRX ,SDCCH Traffic =4 Erlang, Bcchtype=NCOMB.No CBCH GOS: SDCCH/4 = 1%, SDCCH/8 =0.5% & TCH % =2% 1> When Immediate Assignment on TCH not used Erlang B Table :To maintain 0.5 % GOS & 4 Erlang min 13 Subchannels reqd 2SDCCH/8 => TCH=(3TRX*8TS) –(1BCCH)-(2SDCCH/8)=21TCH’s 21TCH’s with 2 % GOS => 14.04 Erlang 2> When Immediate Assignment on TCH used If we use 1SDCCH/8 only than 4 Erlangs with 8 sub channels GOS=>3 % Congested Erlang will be =4 Erlang x 3 %=0.12Erlang 1SDCCH/8 => TCH=(3TRX*8TS) –(1BCCH)-(1SDCH/8)=22TCH’s 22TCH’s with 2 % GOS => 14.9 Erlang Actual TCH Capacity=14.9 – 0.12 = 14.7 Erlang TCH Capacity in the cell is increased with 0.7 Erlang Nov 17, 2003

SDCCH Dimensioning Immediate Assignment on TCH not used

Nov 17, 2003

SDCCH Dimensioning Recommended SDCCH Configurations

Nov 17, 2003

SDCCH Dimensioning HALF RATE CAPACITY CALCULATION Half rate will affect SDCCH dimensioning since more signaling will be req’d when no of TCH is increased. Important dimensioning factor is therefore the Half rate penetration .i.e.the % of Half rate mobile in a NW. Example: 2 TRX Cell, Half Rate Penetration =10 %, 1 SDCCH/8 TCH/F =14 support 14 Subscriber Penetration 10% of 14 is 1.4 = 2 Subscribers (Req’d 2 Half Rate TCH/H) Total 13 TCH/F+2TCH/H = 15 TCH required Capacity : Erlang B Table: 15 TCH @ 2% GOS => 9.0096 Erlang Nov 17, 2003

SDCCH Dimensioning Max Allowed SDCCH/TCH Load Ratio (Half Rate)

AC : Average Cells BC : Border Cells IC : Inner Cells

Nov 17, 2003

SDCCH Dimensioning Dimensioning based on STS data More accurate dimensioning is achieved by using cell statistics .i.e. STS counters •SDCCH Traffic •TCH Traffic •SDCCH/TCH Load Ratio % •SDCCH Congestion •TCH Congestion •SDCCH Mean Holding Time •Availability of SDCCH Channels •Availability of TCH Channels

Nov 17, 2003

Parameters MFRMS :This parameter defines period of transmission for PAGING REQUEST messages to the same paging subgroup. T3212 : Is the periodic registration timer ACCSTATE : Activate/Deactivate the Adaptive config of logical channel feature per cell basis CHAP :Selecting Channel Allocation profile per cell. SLEVEL: The attempt to increase the number of SDCCH/8 will take place when allocation of an SDCCH has failed due to congestion. STIME :Parameter STIME determines how long the system waits before the number of SDCCH/8 added by this function is decreased when the demand for signalling channels has returned to a low level BTDM :Implicit detach supervision should be equal or longer than T3212 in BSC. GTDM : is an extra Gurad time in minutes before the subscriber is set to detach. RLINKT: Radio link time-out This parameter defines the time before an MS disconnects a call due to failure in decoding SACCH messages. The parameter is given as number of SACCH periods (480ms). Nov 17, 2003

Parameters for SDCCH Dimensioning

Nov 17, 2003

STS Counters CCALLS

: Call attempt counter

CCONGS

: Congestion counter

CTRALACC : Traffic level accumulator. CNSCAN

: Number of accumulations of SDCCH traffic level counter.

CNDROP

: Dropped connections due to Failure.

CNUCHCNT : Number of defined channels. CAVAACC

: Available channels accumulator.

CMSESTAB : Successful MS channel establishment on SDCCHs. CTCONGS Nov 17, 2003

: SDCCH congestion time ( Sec)

Formulas No. of SDCCH Attempts

CCALLS

SDCCH Congestion (%)

100 X { CCONGS / CCALLS }

No. of SDCCH Connections

CMSESTAB

SDCCH Establishments No Congestion (%)

100 X {CMSESTAB / (CCALLS - CCONGS)}

SDCCH Time Congestion (%)

100 X { CTCONGS / (RPL * 60)}

SDCCH Drop (%)

100 X { CNDROP / CMSESTAB }

SDCCH Mean Holding Time (Sec.)

RPL X 60 X {(CTRALACC/CNSCAN) / CMSESTAB }

SDCCH Traffic (Erlang)

CTRALACC / CNSCAN

SDCCH/TCH Ratio

(CTRALACC/CNSCAN) / ((TFTRALACC/TFNSCAN)+(THTRALACC/THNSCAN))

Nov 17, 2003

Quality Report : Call Setup Analysis Report

W-6

Measuring Period : 03 Nov 2003 to 09 Nov 2003 (7Days) (Weekly Avg Stats) QUALITY REPORT :Call Setup Analysis Report ( W-6) S DRP(HYD)

15Sep-21Sep 22Sep-29Sep 29Sep-5Oct 06Oct-12Oct 03Nov-09Nov Sr No 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

S DRP (ROAP)

CELL

134 127 112 25 89 NOD

Cells Cells Cells Cells Cells >1%

HYD001B HYD004B HYD005A HYD007B HYD012C HYD018A HYD018B HYD020B HYD025C HYD026C HYD028A HYD028C HYD030C HYD031C HYD038A HYD040A HYD040B HYD042A HYD045B HYD051C

633 305 359 79 432 433 653 298 481 653 413 601 373 581 327 279 522 505 1632 229

1.08 1.03 1.54 1.34 6.51 1.18 1.13 1.02 1.28 1.7 1.03 1.23 1.26 1.35 1.11 1.07 1.3 1.14 1.28 1.01

SDRP NOD SCSR CONR

CELL ADO001B ADO002B AKI001A AKI001B AKI001C AMA001A AMA001A AMA001B AMA001C AMA001C ANK001B ANN001A ANN001B ANN001C ANP001A ANP001B ANP001C AVA001A AVA001B BHI001A

275 295 309 154 295 NOD

Cells Cells Cells Cells Cells >1%

109 54 29 21 37 3 82 37 5 72 144 14 30 96 18 29 20 49 26 258

1.52 1.33 1.04 1.04 2.15 1.54 2.66 1.08 2.94 2.94 1.11 3.29 2.15 5.64 1.06 2.19 1.7 1.95 1.13 1.45

SCSR %(HYD)

175 192 187 178 206 CELL HYD012C HYD117C HYD155B HYD161B HYD168A HYD058A HYD124B HYD146B HYD012A HYD093B HYD170B HYD155A HYD161C HYD089B HYD011B HYD121B HYD146C HYD145B HYD108C HYD101C

LEGENDS SDCCH Drop Rate % Week Total Dropped SDCCH's SDCCH Call Success Rate % SDCCH Congestion rate %

Nov 17, 2003

SCSR % (ROAP)

Cells Cells Cells Cells Cells < 96 %

357 378 400 382 372 CELL

Cells Cells Cells Cells Cells < 96 %

73.35 78.45 81.57 82.57 83.77 83.99 84 86.41 86.52 86.86 87 87.29 87.59 87.82 87.85 87.97 88.01 88.23 88.49 88.71

KOL001B JGP001C HIN002C RAJ001B VIZ020C JGP001A VJA018B CHI001C EMG001C RAZ001B NID001C CHL004C RJM007B VJA020A ONG004B ANN001A CHI003B VSP001B ANN001C VJA019B

65.95 72.07 73.01 73.06 73.67 75.2 75.81 77.68 78.01 78.98 79.41 79.47 80.13 81.21 81.78 81.92 82.55 82.8 83.19 83.22

NOC CT(S) ALL

23.09.03

CONR% (HYD)

68 98 71 55 59 CELL HYD201A HYD176A HYD176C HYD176B HYD137C HYD168A HYD005B HYD155A HYD161B HYD137B HYD054B HYD170B HYD171B HYD168C HYD137A HYD177B HYD142A HYD053C HYD161C HYD153C

Cells Cells Cells Cells Cells >0.5% NOC 3.31 3081 3.19 2862 2.98 1695 2.3 942 1.94 559 1.75 207 1.6 725 1.39 152 1.36 138 1.3 257 1.28 386 1.27 139 1.23 323 1.22 82 1.1 129 1.05 206 1.02 147 1.01 161 1 95 0.99 191

SDCCH Congestion Counter Cong. Time in Secs (Week Tot) SDCCH Drop Rate % SDCCH Estab Success Rate % SDCCH Congestion rate %

CONR% (ROAP)

CT (S) 1952 8177 4397 3095 1423 656 2465 403 262 993 1654 375 1219 320 346 791 701 496 147 541

109 174 135 109 78 CELL HIN002C KAD001B GUN009B VIZ027C KAD001C HIN001B ANA001B TEN002C KAD001A VIZ023C ADO001C GOD001B SUL001A MAH002A STP001B VSP001C STP001A TVR001C RJM008B SAN001B

Cells Cells Cells Cells Cells >0.5% NOC 2.37 2.35 2.19 1.91 1.72 1.59 1.42 1.4 1.33 1.32 1.32 1.31 1.3 1.23 1.05 1.03 1.01 1.01 0.98 0.98

90 602 641 267 392 183 275 372 268 183 190 372 71 104 374 135 329 258 15 134

ALL SDRP>1% SER <96% CONR >0.5 % 72Cells 116Cells 97Cells 81Cells 60Cells CT Worst Cells (S) 326 NIZ001A 1989 NIZ001B 2410 CHL001A 638 BHI001A 1702 MAH002B 664 KHA001B 1084 TEN002C 1434 TIR008A 1127 AKI001A 790 BPL001B 860 TVR001C 1099 DHA001C 169 MAH002A 390 HIN001B 1865 BPL001C 270 TAD001C 1542 CHL002C 924 MAC001A 65 DHA001B 318 ADO001B

Know More - SDCCH

Thank you

Nov 17, 2003

S. Rajshekhar Deshraj

Call Setup-Mobile Terminating Call MS

BTS

PCH RACH

3>Paging Req(Imsi on PCH)

2>Paging Command Imsi/Tmsi+PG+TRX+CG+TN

4>Channel Req(On RACH)

5>Channel Reqd (Access Delay)

BSC

MSC

1>Paging(LAI+IMSI/TMSI)

6>Channel Actn (MSPwr,BSPwr,TA) 7>Channel Activation Ack AGCH

8>Imm Assign Cmd(On AGCH , Freq +TS+ SDCCH SubChannel No+TA

8>Immediate Assign SABM (Paging Resp:IMSI/MS Class)

SDCCH

UA(Paging Resp) Unnumbered Ack Frame which confirms only 1 MS is using Sig Channel 10>Auth Req (128 bit RAND+3bitCKSN)

SDCCH

9>Estblish Ind (Paging Resp) IMSI+MS Class 10>Auth Req (128 bit RAND+3bitCKSN)

11>Auth Response (MS Calculate 11>Auth Response (SRES) SRES & Kc with its own Ki stored in SIM by appling algorithm A3&A8)

9>Conn Req (Paging Resp: BSC add CGI) 10>Auth Req (128 bit RAND+ 3bit CKSN)

11>Auth Response (SRES)

Next.. Nov 17, 2003

Call Setup-Mobile Terminating Call MS SDCCH SDCCH

BTS

14>Setup 15>Call Confirmed

SDCCH 19>Assignment Cmnd (BSC send message on SDCCH to MS telling to go TCH)

TCH

TCH TCH

TCH

20>Assign Comp (MS tune to TCH and send Ind that Chan is Seized)

22>Alert (MS Send Alert to MSC as soon as the ringing is started in MS) 23>Connect (When MS Sub Answer the Conn message sent to MSC) 24>Connect Ack

Nov 17, 2003

BSC 14>Setup

15>Call Confirmed 17>Channel Activation (BSC Allocated Idle TS for Traffic)

MSC

14>Setup (Req for Services I.e. Speech/Data/Fax etc) 15>Call Confirmed 16>Assignment Req (MSC send CIC to BSC)

18>Channel Activation Ack 19>Assignment Cmnd (BSC send message on SDCCH to MS telling to go TCH)

20>Assign Comp (MS tune to TCH and send Ind that Chan is Seized) 21>RF Chann Realease 21>RF Chann Realease Ack 22>Alert (MS Send Alert to MSC as soon as the ringing is started in MS) 23>Connect (When MS Sub Answer the Conn message sent to MSC) 24>Connect Ack

20>Assign Comp (MS tune to TCH and send Ind that Chan is Seized)

22>Alert (MS Send Alert to MSC as soon as the ringing is started in MS) 23>Connect (When MS Sub Answer the Conn message sent to MSC) 24>Connect Ack

Exit..