GSM uses a cellular network structure with each cell served by a base station. The network components include the mobile station (MS), base station subsystem (BSS) including base transceiver stations (BTS) and base station controller (BSC), mobile switching center (MSC), home location register (HLR), visitor location register (VLR), equipment identity register (EIR), and authentication center (AUC). The BSS provides radio coverage for one or more cells using BTS and controls communication between MS and MSC. The MSC routes calls between mobile users in its area and external networks. The HLR and VLR store subscription and location data of mobile users.

1. GSM

2. Global system for mobile (GSM)
• Frequency of operation:
• Bandwidth: 200 KHz
• Tx/Rx spacing: 95 MHz
• Number of channel: 374
• Access method: TDMA, FDMA
• Modulation: GMSK
• Voice channel coding: RPE-LTE (regular pulse excitation – long term prediction)
• Full rate -13 Kbps
• Half rate- 6.5 Kbps

3. GSM architecture
GMSC
BTS
BTS
BSC HLR
OMC
VLR
BSS
AUC
Other MSC
VLR
Other Networks
(PSTN,PSPDN)
EIROther
MSC
MS
G
B
A C
F
E
Abis
D
Abis
Um
X.25

4. Mobile system (MS)

5. Network Components
Mobile Station (MS)
• The Mobile Station consists of the Mobile Equipment (ME) and the Subscriber Identity Module
(SIM).
Mobile Equipment (ME)
• The Mobile Equipment is the hardware used by the subscriber to access the network.
• The mobile equipment can be Vehicle mounted, with the antenna physically mounted on the
outside of the vehicle or portable mobile unit, which can be handheld.
• Mobiles are classified into five classes according to their power rating.
CLASS POWER OUTPUT
1 20W
2 8W
3 5W
4 2W
5 0.8W

6. Network Components
SIM - Subscriber Identity Module
• The SIM is a removable card that plugs into the ME.
• It identifies the mobile subscriber and provides information about the service that the
subscriber should receive.
• The SIM contains several pieces of information
– International Mobile Subscribers Identity ( IMSI ) - This number identifies the mobile
subscriber. It is only transmitted over the air during initializing.
– Temporary Mobile Subscriber Identity ( TMSI ) - This number also identifies the subscriber.
It can be alternatively used by the system. It is periodically changed by the system to
protect the subscriber from being identified by someone attempting to monitor the radio
interface.
– Location Area Identity ( LAI ) - Identifies the current location of the subscriber.

7. Network Components
– Subscribers Authentication Key ( Ki ) - This is used to authenticate the SIM card.
– Mobile Station International Standard Data Number ( MSISDN ) - This is the
telephone number of the mobile.
• Most of the data contained within the SIM is protected against reading (e.g. Ki ) or
alterations after the SIM is issued.
• Some of the parameters ( e.g.. LAI ) will be continuously updated to reflect the current
location of the subscriber.
• The SIM card can be protected by use of Personal Identity Number ( PIN ) password.
• The SIM is capable of storing additional information such as accumulated call charges.

8. Network Components
Mobile Station International Subscribers Dialing Number (MSISDN )
• Human identity used to call a MS
• The Mobile Subscriber ISDN (MSISDN) number is the telephone number of the MS.
• This is the number a calling party dials to reach the subscriber.
• It is used by the land network to route calls toward the MSC.
91 XXX 12345
CC
NDC
SN
CC NDC SN
= Country code
= National Destination Code
= Subscriber Number

9. MCC MNC MSIN
404 XX 12345..10
MCC
MNC
MSIN
= Mobile Country Code ( 3 Digits )
= Mobile Network Code ( 2 Digits )
= Mobile Subscriber Identity Number
International Mobile Subscribers Identity ( IMSI ) :
• Network Identity Unique to a MS
• The International Mobile Subscriber Identity (IMSI) is the primary identity of the subscriber
within the mobile network and is permanently assigned to that subscriber.
• The IMSI can be maximum of 15 digits.
Network Components

10. Temporary Mobile Subscribers Identity ( TMSI ) :
• The GSM system can also assign a Temporary Mobile Subscriber Identity (TMSI).
• After the subscriber's IMSI has been initialized on the system, the TMSI can be used for sending
messages backwards and forwards across the network to identify the subscriber.
• The system automatically changes the TMSI at regular intervals, thus protecting the subscriber
from being identified by someone attempting to monitor the radio channels.
• The TMSI is a local number and is always allocated by the VLR.
• The TMSI is maximum of 4 octets.
Network Components

11. MSC

12. Mobile switching center (MSC)
• It is considered as heart of GSM Radio network.
• It undertakes Radio resource management’s
• Signaling protocol with BSC
• Paging and short message services.
• Routing of traffic and signaling
• Verifying IMSI
• Interrogation of HLR and authentication
• MSC is responsible for establishing a traffic channel connection to
• BSS
• To other MSC”s.
• To other networks.
Network Component

13. Registers

14. Equipment Identity Register ( EIR )
• The Equipment Identity Register (EIR) contains a centralized database for validating the international
mobile station equipment identity, the IMEI.
• The database contains three lists:
– The white list contains the number series of equipment identities that have been allocated in the
different participating countries. This list does not contain individual numbers but but a range of
numbers by identifying the beginning and end of the series.
– The grey list contains IMEIs of equipment to be monitored and observed for location and correct
function.
– The black list contains IMEIs of MSs which have been reported stolen or are to be denied service.
• The EIR database is remotely accessed by the MSC’s in the Network and can also be accessed by an
MSC in a different PLMN.
Network Component

15. Equipment Identity Register ( EIR )
White List
All Valid
assigned ID’s
Range 1
Range 2
Range n
Black list
Service denied
MS IMEI 1
MS IMEI 2
MS IMEI n
Grey List
Service allowed
but noted
MS IMEI 1
MS IMEI 2
MS IMEI n
EIR
Network Component

16. TAC FAC SNR
6 2 6 1
TAC
FAC
SNR
SP
SP
= Type Approval Code
= Final Assembly Code
= Serial Number
= Spare
International Mobile Equipment Identity ( IMEI ) :
• IMEI is a serial number unique to each mobile
• Each MS is identified by an International Mobile station Equipment Identity (IMEI) number which
is permanently stored in the Mobile Equipment.
• On request, the MS sends this number over the signaling channel to the
• The IMEI can be used to identify MSs that are reported stolen or operating incorrectly.
Network Component

17. HOME LOCATION REGISTER( HLR )
• The HLR contains the master database of all subscribers in the PLMN.
• This data is remotely accessed by the MSC´´s and VLRs in the network. The data can also be
accessed by an MSC or a VLR in a different PLMN to allow inter-system and inter-country
roaming.
• A PLMN may contain more than one HLR, in which case each HLR contains a portion of the total
subscriber database. There is only one database record per subscriber.
• The subscribers data may be accessed by the IMSI or the MSISDN.
• The parameters stored in HLR are
– Subscribers ID (IMSI and MSISDN )
– Current subscriber VLR.
– Supplementary services subscribed to.
– Supplementary services information (e.g.. Current forwarding address ).
– Authentication key and AUC functionality.
– TMSI and MSRN
Network Component

18. VISITOR LOCATION REGISTER ( VLR )
• The Visited Location Register (VLR) is a local subscriber database, holding details on those
subscribers who enter the area of the network that it covers.
• The details are held in the VLR until the subscriber moves into the area serviced by another
VLR.
• The data includes most of the information stored at the HLR, as well as more precise location
and status information.
• The additional data stored in VLR are
– Mobile status ( Busy / Free / No answer etc. )
– Location Area Identity ( LAI )
– Temporary Mobile Subscribers Identity ( TMSI )
– Mobile Station Roaming Number ( MSRN )
• The VLR provides the system elements local to the subscriber, with basic information on that
subscriber, thus removing the need to access the HLR every time subscriber information is
required.
Network Component

19. • The AUC is a processor system that perform authentication function.
• It is normally co-located with the HLR.
• The authentication process usually takes place each time the subscriber initializes on the
system.
• Each subscriber is assigned an authentication key (Ki) which is stored in the SIM and at the AUC.
• A random number of 128 bits is generated by the AUC & sent to the MS.
• The authentication algorithm A3 uses this random number and authentication key Ki to
produce a signed response SRES( Signed Response ).
• At the same time the AUC uses the random number and Authentication algorithm A3 along
with the Ki key to produce a SRES.
• If the SRES produced by AUC matches the one produced by MS is the same, the subscriber is
permitted to use the network.
Authentication Centre ( AUC )
Network Component

20. BSS

21. Base Station Sub-System ( BSS ) :
• The BSS is the fixed end of the radio interface that provides control and radio coverage
functions for one or more cells and their associated MSs.
• It is the interface between the MS and the MSC.
• The BSS comprises one or more Base Transceiver Stations (BTSs), each containing the radio
components that communicate with MSs in a given area, and a Base Site Controller (BSC) which
supports call processing functions and the interfaces to the MSC.
• Digital radio techniques are used for the radio communications link, known as the Air Interface,
between the BSS and the MS.
• The BSS consists of three basic Network Elements (NEs).
– Transcoder (XCDR) or Remote transcoder (RXCDR) .
– Base Station Controller (BSC).
– Base Transceiver Stations (BTSs) assigned to the BSC. .
Network Component

22. Transcoder( XCDR )
• The speech transcoder is the interface between the 64 kbps PCM channel in the land network
and the 13 kbps Vocoder (actually 22.8 kbps after channel coding) channel used on the Air
Interface.
• This reduces the amount of information carried on the Air Interface and hence, its bandwidth.
• If the 64 kbps PCM is transmitted on the air interface without occupation, it would occupy an
excessive amount of radio bandwidth. This would use the available radio spectrum inefficiently.
• The required bandwidth is therefore reduced by processing the 64 kbps PCM data so that the
amount of information required to transmit digitized voice falls to 13 kbps.
• The XCDR can multiplex 4 traffic channels into a single 64 kbps timeslot. Thus a E1/T1 serial link
can carry 4 times as many channels.
• This can reduce the number of E1/T1 leased lines required to connect remotely located
equipment.
• When the transcoder is between the MSC and the BSC it is called a remote transcoder (RXCDR).
Network Component

23. TRANSCODER(XCDR) - Siemens
Network Component

24. TRANSCODING
30 Timeslots
1 traffic channel / TS
64 Kbps / TS
4 E1 lines = 30 X 4
=120 Timeslots
Each Timeslot =16 X 4
= 64 Kb/s
30 timeslots = 30 x 4
=120 traffic channels
MSC XCDR BSC
0 1 2 3116
Transcoded information from four calls
Network Component

25. Base Station Controller (BSC)
• The BSC network element provides the control for the BSS.
• It controls and manages the associated BTSs, and interfaces with
the Operations and Maintenance Centre (OMC).
• The purpose of the BSC is to perform a variety of functions. The
following comprise the functions provided by the BSC:
– Controls the BTS components.-
– Performs Call Processing.
– Performs Operations and Maintenance (O & M).
– Provides the O & M link (OML) between the BSS and the OMC.
– Provides the A Interface between the BSS and the MSC.
– Manages the radio channels.
– Transfers signaling information to and from MS(s).
Network Component

26. Base Transceiver Station (BTS)
• The BTS network element consists of the hardware components,
such as radios, interface modules and antenna systems that
provide the Air Interface between the BSS and the MS(s).
• The BTS provides radio channels (RF carriers) for a specific RF
coverage area.
• The radio channel is the communication link between the MS(s)
within an RF coverage area and the BSS.
• The BTS also has a limited amount of control functionality which
reduces the amount of traffic between the BTS and BSC.
Network Component

27. BSIC allows a mobile station to distinguish between neighboring base stations.
It is made up of 8 bits.
NCC = National Color Code (Differs from operator to operator)
BCC = Base Station Color Code, identifies the base station to help distinguish between Cell’s
using the same BCCH frequencies
Base Station Identity Code
BCC00 BCCNCC
7 6 5 4 3 2 1 0
Network Component

28. MSC BSC BTS12
BTS1
BTS2
BTS4
BTS3BTS11
BTS13 BTS14
BTS5
BTS6
BTS7
BTS8
BTS9
BTS11
Open ended Daisy Chain
Daisy Chain
with a fork.
Fork has a
return loop
back to the
chain
Star
Daisy Chain
with a fork.
Fork has a
return loop
back to the
chain
BTS Connectivity
Network Component

29. • The OMC controls and monitors the Network elements within a region.
• The OMC also monitors the quality of service being provided by the Network.
• The following are the main functions performed by the OMC-R
– The OMC allows network devices to be manually removed for or restored to service. The
status of network devices can be checked from the OMC and tests and diagnostics
invoked.
– The alarms generated by the Network elements are reported and logged at the OMC. The
OMC-R Engineer can monitor and analyze these alarms and take appropriate action like
informing the maintenance personal.
– The OMC keeps on collecting and accumulating traffic statistics from the network
elements for analysis.
– Software loads can be downloaded to network elements or uploaded to the OMC.
Operation And Maintenance Centre For Radio (OMC-R)
Network Component

30. Cell

31. Cell
Ideal cells Fictitious cells
Representation of Cells

32. Cell
Cell size and capacity
• Cell size determines number of cells available to cover geographic
area and (with frequency reuse) the total capacity available to all
users
• Capacity within cell limited by available bandwidth and operational
requirements
• Each network operator has to size cells to handle expected traffic
demand

33. Cell
Cell structure
• Implements space division multiplex: base station covers a certain transmission area (cell)
• Mobile stations communicate only via the base station
• Advantages of cell structures:
• higher capacity, higher number of users
• less transmission power needed
• more robust, decentralized
• base station deals with interference, transmission area etc. locally
• Problems:
• fixed network needed for the base stations
• handover (changing from one cell to another) necessary
• interference with other cells
• Cell sizes from some 100 m in cities to, e.g., 35 km on the country side (GSM) - even less for higher
frequencies

34. Cell
Capacity of a Cellular System
• Frequency Re-Use Distance
• The K factor or the cluster size
• Cellular coverage or Signal to interference ratio
• Sectoring

35. i
j
1
2
3
4
5
6
7
• Frequency re-use distance is based on the cluster size K
• The cluster size is specified in terms of the offset of the center of a cluster from
the center of the adjacent cluster
K = i2 + ij + j2
Here i=2, j=1
K= 22 + 2*1 + 12
K = 4 + 2 + 1
K = 7
D = (√3)K*R
D = 4.58R
1
2
35
6
7
D
R
The K factor and Frequency Re-Use Distance

36. Increasing cellular system capacity
• Cell sectoring
• Directional antennas subdivide cell into 3 or 6 sectors
• Might also increase cell capacity by factor of 3 or 6
• Cell splitting
• Decrease transmission power in base and mobile
• Results in more and smaller cells
• Reuse frequencies in non-contiguous cell groups
• Example: ½ cell radius leads 4 fold capacity increase

37. Tri-Sector antenna for a cell

38. Highway
TownSuburb
Rural
Cell Distribution in a Network

39. Cell- antenna type
RTP RTT GBT GBM COW
(3,6,9m) (12,15,18,21m) (30,40,50,60m…) (30m) (25m)

40. Channel concepts

41. • Physical channel - Each timeslot on a carrier is referred to as a physical channel. Per carrier
there are 8 physical channels.
• Logical channel - Variety of information is transmitted between the MS and BTS. There are
different logical channels depending on the information sent. The logical channels are of
two types
• Traffic channel
• Control channel
Downlink
Uplink
CHANNEL

42. LOGICAL CHANNELS
TRAFFIC SIGNALLING
FULL RATE
Bm 22.8 Kb/S
HALF RATE
Lm 11.4 Kb/S
BROADCAST COMMON CONTROL DEDICATED CONTROL
FCCH SCH BCCH
PCH RACH AGCH
SDCCH SACCH FACCH
FCCH -- FREQUENCY CORRECTION CHANNEL
SCH -- SYNCHRONISATION CHANNEL
BCCH -- BROADCAST CONTROL CHANNEL
PCH -- PAGING CHANNEL
RACH -- RANDOM ACCESS CHANNEL
AGCH -- ACCESS GRANTED CHANNEL
SDCCH -- STAND ALONE DEDICATED CONTROL CHANNEL
SACCH -- SLOW ASSOCIATED CONTROL CHANNEL
FACCH -- FAST ASSOCIATED CONTROL CHANNEL
DOWN LINK ONLY
UPLINK ONLY
BOTH UP &
DOWNLINKS

43. Broadcast Channel - BCH
• Broadcast control channel (BCCH) is a base to mobile channel which provides
general information about 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 for carrier synchronization
• Synchronization channel (SCH) is a base to mobile channel which carries
information for frame synchronization and identification of the base station
transceiver

44. Common Control Channel - CCH
• Paging channel (PCH) is a base to mobile channel used to alert a
mobile to a call originating from the network
• Random access channel (RACH) is a mobile to base channel used to
request for dedicated resources
• Access grant channel (AGCH) is a base to mobile which is used to
assign dedicated resources (SDCCH or TCH)

45. Dedicated Control Channel - DCCH
• Stand-alone dedicated control channel (SDCCH) is a bi-directional channel
allocated to a specific mobile for exchange of location update information
and call set up information
• 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

46. TAIL BIT
ENCRYPTION BIT
GUARD PERIOD
TRAINING BITS MIXED BITS
SYNCHRONISATION BITSFIXED BITS
FLAG BITS
3 57 1 26 1 57 3 8.25NORMAL BURST
- NB
3 142 3 8.25
FREQUENCY
CORRECTION
BURST - FB
3 3 8.2539 64 39SYNCHRONISATION
BURST - SB
36 41 36 68.25ACCESS
BURST - AB
DEFINITION OF TIME SLOT - 156.25 BITS 15/26ms = 0.577ms

47. • 114 bits are available for data transmission.
• The training sequence of 26 bits in the middle of
the burst is used by the receiver to synchronize
and compensate for time dispersion produced by
multipath propagation.
• 1 stealing bit for each information block (used for
FACCH)

48. 0 1 2 3 4 5 6 2043 2044 2045 2046 2047
0 1 2 3 4 48 49 50
0 1 2 24 25
0 1 2 3 24 25
0 1 2 3 4 48 49 50
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0
1 HYPER FRAME = 2048 SUPERFRAMES = 2 715 648 TDMA FRAMES ( 3 H 28 MIN 53 S 760 MS )
1 SUPER FRAME = 1326 TDMA FRAMES ( 6.12 S )
LEFT (OR) RIGHT
1 MULTI FRAME = 51 TDMA FRAMES (235 .4 ms )
1 SUPER FRAME = 26 MULTI FRAMES
1 SUPER FRAME = 51 MULTI FRAMES
1 MULTIFRAME = 26 TDMA FRAMES ( 120 ms )
TDMA FRAME NO.
0 1
0 1
HIERARCHY OF FRAMES
1 2 3 4 155 156
1 TIME SLOT = 156.25 BITS
( 0.577 ms)
(4.615ms)
(4.615 ms)
1 bit =36.9 micro sec
TRAFFIC CHANNELS
SIGNALLING CHANNELS

49. GSM speech coding

50. Transmit Path
BS Side
8 bit A-Law
to
13 bit Uniform
RPE/LTP speech
Encoder To Channel Coder 13Kbps
8K samples
MS Side
LPF A/D RPE/LTP speech
Encoder To Channel Coder 13Kbps
8K samples
Sampling Rate - 8K
Encoding - 13 bit Encoding (104 Kbps)
RPE/LTP - Regular Pulse Excitation/Long Term Prediction
RPE/LTP converts the 104 Kbps stream to 13 Kbps

51. GSM Speech Coding
• GSM is a digital system, so speech which is inherently analog, has to
be digitized.
• The method employed by current telephone systems for multiplexing
voice lines over high speed trunks and is pulse coded modulation
(PCM). The output stream from PCM is 64 kbps, too high a rate to be
feasible over a radio link.
• Speech is divided into 20 millisecond samples, each of which is
encoded as 260 bits, giving a total bit rate of 13 kbps.
• Regular pulse excited -- linear predictive coder (RPE--LPC) with a long
term predictor loop is the speech coding algorithm.

52. GSM Speech Coding
• The 260 bits are divided into three classes:
• Class Ia 50 bits - most sensitive to bit errors.
• Class Ib 132 bits - moderately sensitive to bit errors.
• Class II 78 bits - least sensitive to bit errors.
• Class Ia bits have a 3 bit cyclic redundancy code added for error detection = 50+3
bits.
• 132 class Ib bits with 4 bit tail sequence = 132 + 4 = 136.
• Class Ia + class Ib = 53+136=189, input into a 1/2 rate convolution encoder of
constraint length 4. Each input bit is encoded as two output bits, based on a
combination of the previous 4 input bits. The convolution encoder thus outputs
378 bits, to which are added the 78 remaining class II bits.
• Thus every 20 ms speech sample is encoded as 456 bits, giving a bit rate of 22.8
kbps.

53. RF optimization

54. RF optimization
• Coverage – good signal level across the whole cell, coverage holes
within a cell service are must be minimized.
• Interference – a reasonable level of interference must be contained at
cell service area in order to provide a quality air interface
• Handover behavior – the quality of air interface in a cell with respect
to handover behavior is good, no unnecessary handover. Rxquality at
acceptable level, BTS &MS use minimum transmit power.
• Traffic Distribution – the quality of air – interface in a cell with respect
to traffic distribution is good, maximum amount of traffic can be
handed

55. Drive testing and analysis
Drive test equipment
• Hardware
• Test mobile phone
• GPS
• Laptop
• Software key
• Air interface analysis Software (any one)
• Ericsson TEMS 900/1800
• Camarco wireless
• Safeco walkabout
• Agilent technologies (HP)
• QVOICE98

56. Drive testing and analysis
Drive tests for optimization
• Initial network coverage verification and benchmarking
• Verification before and after changes
• Locating and measuring interference
• Locating areas where problems exists
• Local coverage holes
• preventive maintenance

57. Drive testing and analysis
Drive rest data collection
• CELL ID including BSIC, LAC and time slot
• RXLEVEL for serving and 6 neighbor cells
• RXQUALITY for the serving cell
• BCCH, BSIC for serving and the neighbor cells
• TIMING ADVANCE
• TRANSMIT POWER
• GPS coordinates
• TIME STAMPS

58. Drive testing and analysis
Drive test route planning
• Primary route (street level)
Includes all major roads, highways and wide thoroughfares
• Secondary route (street level)
Includes all streets, subdivisions and compounds when accessible
• Miscellaneous routes (in-building and special locations)
Includes golf courses, beach resorts, shopping malls, departmental stores,
convention centers, hotels and resorts

59. Drive testing and analysis
Performance problems that often encountered
• Cell dragging
• Dropped calls
• Ping-ponging
• System busy
• Handover boundary

60. Drive testing and analysis
Call dragging – calls may drag a cell beyond the desired handover
boundary. This might result dropped calls or bad RXQUALITY.
Suggestion
• Create an appropriate neighbor cell list
• Change HO parameters such as thresholds, margin, cell baring etc.
• Check serving cell’s cell identifier in the neighbor cell’s neighbor list
• Check neighbor cell’s BCCH, BSIC, LAC, cell ID etc.

61. Drive testing and analysis
Dropped calls – caused by either RF environments or incorrect system
parameters
Suggestions
• Check if an appropriate neighbor cell list is defined
• Check HO parameters
• Existing or new coverage holes
• Interference, co-channels, adjacent channels or external interference
• Serving cell might go down, coverage smaller as before
• Abnormalities such as call setup failure

62. Drive testing and analysis
Ping ponging – serving keep changing causes bad audio quality
Suggestion
• Check if an appropriate neighbor cell list is defined
• Check HO parameters
• Interference, Co-channels, adjacent channels or external interference
• lack of dominating server
• Poor coverage
• Not optimal antenna configuration

63. Drive testing and analysis
System busy – system busy on several call attempts and site appears
consistently on traffic report
Suggestions
• Short term – reduce the traffic on the congested cell/site. However,
the proposed changes MUST NOT create any unacceptable problems
such as coverage holes, dropped calls etc. redesigning the antenna
configuration, add additional RTs, change BTS configuration
• Long term – build a new cell site to off-load traffic

64. Drive testing and analysis
Handover boundary – handover don’t occur at the desires HO boundary, the
result is am imbalance in traffic distribution across the system
Suggestions
• Check if an appropriate neighbor cell list is defined
• Check HO parameters
• Inappropriate antenna configurations of the serving and neighbor cells
• Interference, co-channels, adjacent channels or external interference
• No TCH available (neighbor cells congestion)

65. Advantages and
disadvantages

66. Performance characteristics of GSM
• Communication
• mobile, wireless communication; support for voice and data services
• Total mobility
• international access, chip-card enables use of access points of different
providers
• Worldwide connectivity
• one number, the network handles localization
• High capacity
• better frequency efficiency, smaller cells, more customers per cell
• High transmission quality
• high audio quality and reliability for wireless, uninterrupted phone calls at
higher speeds (e.g., from cars, trains)
• Security functions
• access control, authentication via chip-card and PIN

67. Disadvantages of GSM
• No full ISDN bandwidth of 64 kbps to the user
• Reduced concentration while driving
• Electromagnetic radiation
• Abuse of private data possible
• High complexity of the system
• Several incompatibilities within the GSM standards

68. Advancements
• In early 2000s with the development of internet and service demand among
clients the GSM network seems to be limiting.
• Internet access is made possible by GPRS and EDGE (2.5G) with the speeds
limited to 115 and 135 kbps respectively (theoretically)
• New standards were introduced based on packet switching instead of circuit
switching
• The new standards also included advancements such as higher order modulation
and MIMO

69. Advancement towards 3GPP
• Utilises Packet Switched (PS) domain for Internet access and MMS in parallel with circuit switched
(CS) for voice and SMS, based on WCDMA with TDMA/FDMA in radio part, started in 2000s.
• Incorporates both UMTS (3G) and HSPA/HSPA+ (3.5G)
• High bit rates theoretically up to 2 Mbps in 3GPP Release ’99, and beyond 10 Mbps in 3GPP
Release 5. Practical bit rates are up to 384 kbps initially, and beyond 2 Mbps with Release 5
• MIMO (Multiple Input Multiple Output) antennas
• Higher-Order Modulation (adding 64QAM on downlink and 16 QAM on uplink) Low delays with
packet round trip times below 200 ms
• Seamless mobility also for packet data applications
• Simultaneous voice and data capability
• Interworking with existing GSM/GPRS networks. (backwards compatibility)

70. Advancement towards 4G
• 4G (Fourth Generation)
Mobile systems is all-IP based by default in access and core parts, based on OFDMA (Orthogonal
Frequency Division Multiple Access) with TDMA/FDMA in radio access, started at the beginning of
2010s.

71. Thank You