Post on 03-Apr-2018
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 1/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved
www.huawei.com
Internal
GSM Basics and KPIs
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 2/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved
GSM NETWORK ELEMENTS
Page 1
Um Interface is the central interface of every mobile network and typically
the only one to which the customer is exposed
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 3/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved
Air interface characteristics
Page 2
•ETSI(European Telecommunications Standards Institute) defined all the
characteristics of the air interface.
Examples of the air interface characteristics defined
by ETSI are:
• The output power of by the MS and the BTS • The transmit and receive frequencies of the MS and
the BTS
• The structure of the burst in which the data is sent
• When which type of messages may be sent.
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 4/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved
Mobile Equipment (ME or MS)
Page 3
•The ME is the only part of the GSM network which the subscriber will really
see.
• Mobile types have distinct features which must be known by the network, for
example their maximum transmission power and the services they support.
•The ME is therefore identified by means of a class mark.
•The class mark is sent by the ME in its initial message.
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 5/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved Page 4
The following pieces of information are held in the class mark:
Revision Level –
Identifies the phase of the GSM specifications that the mobile complies with.
RF Power Capability –
The maximum power the MS is able to transmit, used for power control and
handover preparation. This information is held in the mobile power class number.
Ciphering Algorithm –
Indicates which ciphering algorithm is implemented in the MS.
Frequency Capability –
Indicates the frequency bands the MS can receive and transmit on. Currently all
GSM MSs use one frequency band, in the future this band will be extended but not
all MSs will be capable of using it.
Short Message Capability –
Indicates whether the MS is able to receive short messages.
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 6/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved
Subscriber Identity Module (SIM)
Page 5
The SIM contains several pieces of information:
International Mobile Subscriber Identity (IMSI)
This number identifies the MS subscriber. It is only transmitted over the air during
initialization.
Temporary Mobile Subscriber Identity (TMSI)
This number identifies the subscriber, it is periodically changed by the system
management to protect the subscriber from being identified by someoneattempting to monitor the radio interface.
Location Area Identity (LAI)
Identifies the current location of the subscriber.
Subscriber Authentication Key (Ki)
This is used to authenticate the SIM card.
Mobile Station International Services Digital Network (MSISDN)
This is the telephone number of the mobile subscriber. It is comprised of a country
code, a network code and a subscriber number.
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 7/36HUAWEI TECHNOLOGIES CO., LTD. All rights reserved Page 6
Frequency Spectrum
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 8/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved Page 7
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 9/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved Page 8
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 10/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved
Absolute Radio Frequency Channel Number
Page 9
•The Absolute Radio Frequency Channel Number
(ARFCN) is a unique number given to each radio channel
in GSM. The ARFCN can be used to calculate the exact
frequency of the radio channel
Band Name ARFCN Uplink Downlink
(MHz) (MHz)
GSM900
Primary GSM 1 ≤ n ≤ 124 890 + 0.2×n f up(n) + 45
Extended GSM 0 ≤ n ≤ 124 890 + 0.2×n f up(n) + 45
975 ≤ n ≤ 1023 890 + 0.2×(n-1024)
GSM Rail 0 ≤ n ≤ 124 890 + 0.2×n f up(n) + 45
955 ≤ n ≤ 1023 890 + 0.2×(n-1024)
GSM1800 GSM1800 512 ≤ n ≤ 885 1710.2 + 0.2×(n-512) f up(n) + 95
(DCS1800)
GSM1900 GSM1900 512 ≤ n ≤ 810 1850.2 + 0.2×(n-512) f up(n) + 80
(PCS1900)
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 11/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved
Physical channels
Page 10
•FDMA and TDMA
To achieve a high spectral efficiency in the cellular network a
combination of FDMA (Frequency Division Multiple Access) and
TDMA (Time Division Multiple Access) is used.
Each of the carrier frequencies is divided in time, using a TDMA
scheme to increase the number of channels per carrier
frequency. This results that each carrier frequency channel carries
eight time-division multiplexed physical channels (eight timeslots)
A physical channel is determined by the carrier frequency and
the timeslot number.
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 12/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved Page 11
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 13/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved
Logical Channels
Page 12
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 14/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved
Broadcast Channel – BCH(Down Link)
Broadcast control channel (BCCH) is a base tomobile channel which provides general informationabout the network, the cell in which the mobile is
currently located and the adjacent cells Frequency correction channel (FCCH) is a base to
mobile channel which provides information forcarrier synchronization
Synchronization channel (SCH) is a base to mobilechannel which carries information for framesynchronization and identification of the base stationtransceiver
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 15/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved
Common Control Channel - CCH
Paging channel (PCH) is a base to mobilechannel used to alert a mobile to a call
originating from the network
Random access channel (RACH) is a mobileto base channel used to request for dedicated
resources
Access grant channel (AGCH) is a base tomobile which is used to assign dedicated
resources (SDCCH or TCH)
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 16/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved
Dedicated Control Channel - DCCH
Stand-alone dedicated control channel (SDCCH) is a bi-directionalchannel allocated to a specific mobile for exchange of location update
information and call set up information
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 17/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved
Dedicated Control Channel - DCCH
Slow associated control channel (SACCH) is a bi-
directional channel used for exchanging control
information between base and a mobile during the
progress of a call set up procedure. The SACCH is
associated with a particular traffic channel or stand
alone dedicated control channel
Fast associated control channel (FACCH) is a bi-
directional channel which is used for exchange of
time critical information between mobile and base
station during the progress of a call. The FACCH
transmits control information by stealing capacity
from the associated TCH
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 18/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved
Logical channel combinations
Page 17
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 19/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved
Frame Structure
Page 18
Graphical representation of the logical
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 20/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved
Graphical representation of the logical
channel combinations 4 and 5.
Page 19
rap ca represen a on o e og ca
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 21/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved
rap ca represen a on o e og cachannel combinations 1,2,and 7
Page 20
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 22/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved
Mobile looks for BCCH after switching on
RACH send channel request
AGCH receive SDCCH
SDCCH do the authentication and TMSI allocation
SDCCH require traffic channel assignment
SDCCH send call establishment request
SDCCH send the setup message and desired number
FACCH switch to traffic channel and send ack (steal bits)
FACCH receive alert signal ringing sound
FACCH acknowledge connect message and use TCH
TCH conversation continues
FACCH receive connect message
Call establishment from a mobile
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 23/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved
GetServi
ce
GetSDC
CH
Establish SD
Channe
l
Est. TCHConn. Call PhoneRef. Phon
SD
Blocking
SDCCH Seizer
TCH
Blocking
CSSR or TCHAssignment
Call Establishment
Call
completion
Rate (TCH
Drop call)
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 24/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved
Main KPIs
KPIs Can be classified in to two based on
Accessibility KPIs
▪ SD Blocking
▪ SD Drop
▪ Immediate Assignment Success Rate
▪ TCH Assignment Success Rate
▪ TCH Blocking
▪ Call Setup Success Rate
Retainability KPIs
▪ TCH Drop
Handover Success Rate
Page 23
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 25/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved
SD Blocking
Main Reasons•Location Area not optimized
•SMS usage
•SDCCH availability
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 26/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved Page 25
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 27/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved
Main reasons
Page 26
following issues that could be possible reasons for SDCCH Drops:
•Low signal strength
•Interference
•Path loss Imbalance between UL/DL
•High Timing Advance
•MS error or Subscriber behavior •TCH Congestion
•Transmission Congestion (LAPD Concentration)
•Hardware or Transmission failures
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 28/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved Page 27
Call Setup Success Rate (%)
KPI Formula
Call Setup Success Rate (%) = ((Immediate Assignment Success Rate x TCH
Assignment Success Rate) x (1 - SDCCH Drop Rate)) x 100%
Counters
CA303J: CELL_IMM_ASS_SUCC,
CA300J: CELL_IMM_ASS_REQ
CA313: CELL_ASS_SUCC
CA310: CELL_ASS_REQ
CM30:CELL_SD_CALL_DROPS
K3003:CELL_KPI_SD_SUCC
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 29/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved Page 28
Immediate Assignment Success Rate
KPI Formula
Immediate Assignment Success Rate = Call Setup Indications (Circuit Service)
/ Channel Requests (Circuit Service) x 100%
Immediate assignment procedure
CA300J
CA303J
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 30/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved Page 29
Immediate Assignment Success Rate
Related Factor
Coverage/Interference/Transmission/Device/System Traffic Volume
Statistics
TRX power 、TA、 Antenna system、Rxlevel&Power level
Interference Band、RxQuality、Rxlevel、RACH Overload
Alarm
Cell/TRX/SDCCH/TCH Availability、TCH Assignment Successful Rate
、TCH channel active NACK/Timeout
SDCCH/TCH Traffic Volume、SDCCH/TCH Congestion、Immediate
Assignment Measurement、Location Update
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 31/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved Page 30
TCH Assignment Success Rate
Formula
TCH Assignment Success Rate = Successful Assignments / Assignment
Requests x 100%
Assignment procedure on the radio interface
CA310
CA313
• Description
•
The number of successfulassignments is equal to the number
of ASS REQ messages received by
the BSC minus the number of ASS
FAIL messages reported by the BSC
to the MSC in various scenarios,
such as air interface assignment,
Mode Modify, and directed retry.
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 32/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved Page 31
TCH Assignment Success Rate
Related Factor
Coverage/Interference/Transmission/Device/System TrafficVolume
Statistics
TRX power 、TA、 Antenna system、Rxlevel&Power Controllevel、UL&DL Balance
Interference Band、RxQuality、Rxlevel
Alarm
Cell/TRX/TCH Availability、TCH channel activeNACK/Timeout
TCH Traffic Volume、TCH Congestion、Handover (ping-pong)
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 33/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved
TCH Blocking
Page 32
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 34/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved
TCH Drop Rate
Page 33
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 35/36
HUAWEI TECHNOLOGIES CO., LTD. All rights reserved Page 34
Radio Handover Success Rate (%)
Formula Handover Success Rate (%) = (Successful Outgoing Internal Inter-Cell Handovers + Successful
External Outgoing inter-Cell Handovers)/ (Outgoing Internal Inter-Cell Handover Commands +
Outgoing External Inter-Cell Handover Commands) x 100%
Description TCH handover (Intra BSC/Inter BSC)
CH311 :Outgoing Internal Inter-Cell Handover Commands
CH331 :Outgoing External Inter-Cell Handover Commands
CH313 :Successful Outgoing Internal Inter-Cell Handovers
CH333 :Successful Outgoing External Inter-Cell Handovers
7/28/2019 GSM Basics Final
http://slidepdf.com/reader/full/gsm-basics-final 36/36
HUAWEI TECHNOLOGIES CO LTD All i ht d Page 35
Radio Handover Success Rate (%)
Related Factor
Coverage/Interference/Transmission/Device/System Traffic Volume
r Boost before handover 、Direct Retry
Statistics
TRX power 、TA、 Antenna system、Rxlevel、UL&DL Balance
Interference Band、RxQuality、Rxlevel、Rxquality Handover 、Power Control
Alarm、BSC clock、 A interface circuit
Cell/TRX/TCH Availability、TCH channel active NACK/Timeout、Handover measurement
TCH Traffic Volume、TCH Congestion、Neighbor Cell Traffic