This document contains 125 questions about GSM RF topics including general questions about GSM services and standards, channels and TDMA structure, radio propagation and antennas, handovers, modulation, drive testing procedures, GPRS and EDGE, GSM system architecture, and three case studies on tower propagation, cells with the same BCCH, and location area code sizing. The questions cover both conceptual and technical aspects of GSM radio frequency design and optimization.
FREQUENCY CONCEPTS
The following table summarizes the frequency-related specifications of each of the GSM systems. The terms used in the table are explained in the remainder of this section.
System P-GSM 900 E-GSM 900 GSM 1800
Frequencies: • Uplink • Downlink
890-915 MHz
935-960 MHz
Wavelength ~ 33 cm
880-915 MHz
925-960 MHz
GSM 1900
1710-1785 MHz
1805-1880 MHz
1850-1910 MHz
1930-1990 MHz
~ 33 cm ~ 17 cm ~ 16 cm
Bandwidth 25 MHz
35 MHz 75 MHz 60 MHz
Duplex Distance 45 MHz
45 MHz 95 MHz 80 MHz
Carrier Separation 200 kHz
1
Radio Channels
200 kHz 200 kHz 200 kHz
125
175 375 300
Transmission Rate 270 kbits/s
270 kbits/s 270 kbits/s 270 kbits/s
Table 3-1 Frequency-related specifications
FREQUENCY
F Did you know?
Due to frequency, a BTS transmitting information at 1800 MHz with an output power of 10 Watts (W) will cover only half the area of a similar BTS transmitting at 900 MHz. To counteract this, BTSs using 1800 MHz may use a higher output power.
An MS communicates with a BTS by transmitting or receiving radio waves, which consist of electromagnetic energy. The frequency of a radio wave is the number of times that the wave oscillates per second. Frequency is measured in Hertz (Hz), where 1 Hz indicates one oscillation per second. Radio frequencies are used for many applications in the world today. Some common uses include:
• Television: 300 MHz approx. • FM Radio: 100 MHz approx. • Police radios: Country dependent • Mobile networks: 300 - 2000 MHz approx.
The frequencies used by mobile networks varies according to the standard being used
2
. An operator applies for the available frequencies or, as in the United States, the operator bids for frequency bands at an auction. The following diagram displays the frequencies used by the major mobile standards:
DAMPS 1900 MHz
0450900800 1500 1800 1900 NMT 450
PDC 800
GSM 900 GSM 1800 GSM 1900NMT 900
PDC 1500AMPS DAMPS 800
TACS
Figure 3-1 Frequencies for major mobile standards
The GSM standard was developed by the Groupe SpecialMobile, which was an initiative of the Conference of European Post and Telecommunications (CEPT) administrations.
The responsibility for GSM standardization now resides with the
Special Mobile Group (SMG) under the European Telecommunication Standard Institute (ETSI).
Fully digital system utilizing the 900MHz frequency band.
TDMA over radiocarriers(200 kHz carrier spacing)
8 full rate or 16 half rate TDMA channels per carrier
User/terminal authentication for fraud control
Encryption of speech and data transmissions over the radio path
Full international roaming capability
Low speed data services (upto 9.6kb/s)
Compatibility with ISDN for supplementary services
Support of short message services(SMS)
GSM supports a range of basic and supplementary services, and these services are defined analogous to those for ISDN(i.e.,bearer services, teleservices, and supplementary services).
The most important service supported by GSM is Telephony.
Other services derived from telephony included in the GSM specification are emergency calling and voice messaging.
Bearer services supported in GSM include various asynchronous and synchronous data services for information transfer.
Teleservices based on these bearer services include group 3 fax and short message service(SMS)
The data capabilities of GSM have now been enhanced to include high speed circiut-switched data(HSCSD) and general packet radio service (GPRS).
Call offering services call forwarding
Call resrtiction services call barring
Call waiting service
Call hold service
Multi party service tele conferencing
Calling line presentation restriction services
Advice of charge service
Closed user group service
The GSM System comprises of Base Transceiver Station (BTS), Base Station Controllers (BSC), Mobile Switching Centers (MSC), and set of registers (databases) to assist in mobility management and security functions.
All signaling between the MSC and the various registers (databases) as well as between the MSCs takes place using the Signaling System 7(SS7) network, with the application level messages using the Mobile Application Protocol (MAP) designed specifically for GSM.
The MAP protocol utilizes the lower layer functions from the SS7 protocol stack.
Full rate => Used for speech at 13 Kbits/s
or sending data at 9.6 Kbits/s
Half rate => Used for speech at 6.5 Kbits/s
or sending data at 4.8 Kbits/s
Enhanced Full rate => Used for speech at 13 Kbits/s
or sending data at 9.6 Kbits/s but
with almost Land line quality
FCCH = FREQUENCY CORRECTION CHANNEL
=> To tell the Mobile that this is the BCCH carrier
=> To able the Mobile to synchronize to the frequency
(Downlink only)
SCH = SYNCHRONISATION CHANNEL
=> Used for sending BSIC (Base station Identity Code)
=> Give TDMA frame number to the Mobile.
(Downlink only)
BCCH = BROADCAST CONTROL CHANNEL
=> Used for sending information to the mobile like
CGI (Cell Global identity), LAI (Location Area Identity),
BCCH carriers of the neighboring cells,
maximum output power allowed in the cell and other
broadcast messages like barred cell. (Downlink only)
PCH = PAGING CHANNEL
=> Used for paging the Mobile. (Downlink only)
Reason could be an incoming call or an incoming Short Message.
RACH = RANDOM ACCESS CHANNEL
=> Used for responding to the paging (terminating), Location updating
or to make call access (originating) by asking for a signaling channel.
(Uplink only)
AGCH = ACCESS GRANT CHANNEL
=> Used to allocate SDCCH to the mobile.
(Downlink only)
UMTS/3G RAN Capacity Management Guideline Part-02 (Sectorization))Md Mustafizur Rahman
UMTS RAN capacity management is one of the Key activities to maintain the good QoS & stability of the 3G system. A relatively high load can affect the accessibility, coverage and QoS of established services. The capacity, coverage and QoS of the WCDMA system are mutually affected. Hence, for a stable & good quality 3G network, UMTS capacity need to be monitored, expanded & manage regularly.
In the first part of document (Part-1) UMTS soft capacity management along with the correlation between capacity vs accessibility, UMTS expansion threshold, counters & effective mechanism of UMTS Soft capacity management have been depicted. This part of the Document is focused on UMTS Hard Expansion Methodology. 3G Capacity management by Sectorization has been explained thoroughly.
After completing this, you will be able to gain knowledge on 3G Expansion Parameters, 3G Expansion Threshold, Capacity Gain, Cost vs Capacity Gain by Sectorization. Moreover, you will be familiar with Planning, Optimization & Post Performance activities of Sectorization.
GSM is the globel system of organation . It consists of
M.S,BSC MSC ,OMC,FIXED Phone.Mobile station is carried by
the subscriber.and base station subsystem control the radio
link with mobile station . The main part of system is
mobile switching center perform switching of calls between
the mobile and fixed or mobile network use. and operational
and maintainence center oversees the proper operation and
set up of the network. The MS and BSC communicate across
the um link or air interface and BSC&MSC communicate across
A interface.
FREQUENCY CONCEPTS
The following table summarizes the frequency-related specifications of each of the GSM systems. The terms used in the table are explained in the remainder of this section.
System P-GSM 900 E-GSM 900 GSM 1800
Frequencies: • Uplink • Downlink
890-915 MHz
935-960 MHz
Wavelength ~ 33 cm
880-915 MHz
925-960 MHz
GSM 1900
1710-1785 MHz
1805-1880 MHz
1850-1910 MHz
1930-1990 MHz
~ 33 cm ~ 17 cm ~ 16 cm
Bandwidth 25 MHz
35 MHz 75 MHz 60 MHz
Duplex Distance 45 MHz
45 MHz 95 MHz 80 MHz
Carrier Separation 200 kHz
1
Radio Channels
200 kHz 200 kHz 200 kHz
125
175 375 300
Transmission Rate 270 kbits/s
270 kbits/s 270 kbits/s 270 kbits/s
Table 3-1 Frequency-related specifications
FREQUENCY
F Did you know?
Due to frequency, a BTS transmitting information at 1800 MHz with an output power of 10 Watts (W) will cover only half the area of a similar BTS transmitting at 900 MHz. To counteract this, BTSs using 1800 MHz may use a higher output power.
An MS communicates with a BTS by transmitting or receiving radio waves, which consist of electromagnetic energy. The frequency of a radio wave is the number of times that the wave oscillates per second. Frequency is measured in Hertz (Hz), where 1 Hz indicates one oscillation per second. Radio frequencies are used for many applications in the world today. Some common uses include:
• Television: 300 MHz approx. • FM Radio: 100 MHz approx. • Police radios: Country dependent • Mobile networks: 300 - 2000 MHz approx.
The frequencies used by mobile networks varies according to the standard being used
2
. An operator applies for the available frequencies or, as in the United States, the operator bids for frequency bands at an auction. The following diagram displays the frequencies used by the major mobile standards:
DAMPS 1900 MHz
0450900800 1500 1800 1900 NMT 450
PDC 800
GSM 900 GSM 1800 GSM 1900NMT 900
PDC 1500AMPS DAMPS 800
TACS
Figure 3-1 Frequencies for major mobile standards
The GSM standard was developed by the Groupe SpecialMobile, which was an initiative of the Conference of European Post and Telecommunications (CEPT) administrations.
The responsibility for GSM standardization now resides with the
Special Mobile Group (SMG) under the European Telecommunication Standard Institute (ETSI).
Fully digital system utilizing the 900MHz frequency band.
TDMA over radiocarriers(200 kHz carrier spacing)
8 full rate or 16 half rate TDMA channels per carrier
User/terminal authentication for fraud control
Encryption of speech and data transmissions over the radio path
Full international roaming capability
Low speed data services (upto 9.6kb/s)
Compatibility with ISDN for supplementary services
Support of short message services(SMS)
GSM supports a range of basic and supplementary services, and these services are defined analogous to those for ISDN(i.e.,bearer services, teleservices, and supplementary services).
The most important service supported by GSM is Telephony.
Other services derived from telephony included in the GSM specification are emergency calling and voice messaging.
Bearer services supported in GSM include various asynchronous and synchronous data services for information transfer.
Teleservices based on these bearer services include group 3 fax and short message service(SMS)
The data capabilities of GSM have now been enhanced to include high speed circiut-switched data(HSCSD) and general packet radio service (GPRS).
Call offering services call forwarding
Call resrtiction services call barring
Call waiting service
Call hold service
Multi party service tele conferencing
Calling line presentation restriction services
Advice of charge service
Closed user group service
The GSM System comprises of Base Transceiver Station (BTS), Base Station Controllers (BSC), Mobile Switching Centers (MSC), and set of registers (databases) to assist in mobility management and security functions.
All signaling between the MSC and the various registers (databases) as well as between the MSCs takes place using the Signaling System 7(SS7) network, with the application level messages using the Mobile Application Protocol (MAP) designed specifically for GSM.
The MAP protocol utilizes the lower layer functions from the SS7 protocol stack.
Full rate => Used for speech at 13 Kbits/s
or sending data at 9.6 Kbits/s
Half rate => Used for speech at 6.5 Kbits/s
or sending data at 4.8 Kbits/s
Enhanced Full rate => Used for speech at 13 Kbits/s
or sending data at 9.6 Kbits/s but
with almost Land line quality
FCCH = FREQUENCY CORRECTION CHANNEL
=> To tell the Mobile that this is the BCCH carrier
=> To able the Mobile to synchronize to the frequency
(Downlink only)
SCH = SYNCHRONISATION CHANNEL
=> Used for sending BSIC (Base station Identity Code)
=> Give TDMA frame number to the Mobile.
(Downlink only)
BCCH = BROADCAST CONTROL CHANNEL
=> Used for sending information to the mobile like
CGI (Cell Global identity), LAI (Location Area Identity),
BCCH carriers of the neighboring cells,
maximum output power allowed in the cell and other
broadcast messages like barred cell. (Downlink only)
PCH = PAGING CHANNEL
=> Used for paging the Mobile. (Downlink only)
Reason could be an incoming call or an incoming Short Message.
RACH = RANDOM ACCESS CHANNEL
=> Used for responding to the paging (terminating), Location updating
or to make call access (originating) by asking for a signaling channel.
(Uplink only)
AGCH = ACCESS GRANT CHANNEL
=> Used to allocate SDCCH to the mobile.
(Downlink only)
UMTS/3G RAN Capacity Management Guideline Part-02 (Sectorization))Md Mustafizur Rahman
UMTS RAN capacity management is one of the Key activities to maintain the good QoS & stability of the 3G system. A relatively high load can affect the accessibility, coverage and QoS of established services. The capacity, coverage and QoS of the WCDMA system are mutually affected. Hence, for a stable & good quality 3G network, UMTS capacity need to be monitored, expanded & manage regularly.
In the first part of document (Part-1) UMTS soft capacity management along with the correlation between capacity vs accessibility, UMTS expansion threshold, counters & effective mechanism of UMTS Soft capacity management have been depicted. This part of the Document is focused on UMTS Hard Expansion Methodology. 3G Capacity management by Sectorization has been explained thoroughly.
After completing this, you will be able to gain knowledge on 3G Expansion Parameters, 3G Expansion Threshold, Capacity Gain, Cost vs Capacity Gain by Sectorization. Moreover, you will be familiar with Planning, Optimization & Post Performance activities of Sectorization.
GSM is the globel system of organation . It consists of
M.S,BSC MSC ,OMC,FIXED Phone.Mobile station is carried by
the subscriber.and base station subsystem control the radio
link with mobile station . The main part of system is
mobile switching center perform switching of calls between
the mobile and fixed or mobile network use. and operational
and maintainence center oversees the proper operation and
set up of the network. The MS and BSC communicate across
the um link or air interface and BSC&MSC communicate across
A interface.
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Just a game Assignment 3
1. What has made Louis Vuitton's business model successful in the Japanese luxury market?
2. What are the opportunities and challenges for Louis Vuitton in Japan?
3. What are the specifics of the Japanese fashion luxury market?
4. How did Louis Vuitton enter into the Japanese market originally? What were the other entry strategies it adopted later to strengthen its presence?
5. Will Louis Vuitton have any new challenges arise due to the global financial crisis? How does it overcome the new challenges?Assignment 3
1. What has made Louis Vuitton's business model successful in the Japanese luxury market?
2. What are the opportunities and challenges for Louis Vuitton in Japan?
3. What are the specifics of the Japanese fashion luxury market?
4. How did Louis Vuitton enter into the Japanese market originally? What were the other entry strategies it adopted later to strengthen its presence?
5. Will Louis Vuitton have any new challenges arise due to the global financial crisis? How does it overcome the new challenges?Assignment 3
1. What has made Louis Vuitton's business model successful in the Japanese luxury market?
2. What are the opportunities and challenges for Louis Vuitton in Japan?
3. What are the specifics of the Japanese fashion luxury market?
4. How did Louis Vuitton enter into the Japanese market originally? What were the other entry strategies it adopted later to strengthen its presence?
5. Will Louis Vuitton have any new challenges arise due to the global financial crisis? How does it overcome the new challenges?
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1. Created by: Faisal Adnan Siddiqui
GSM RF INTERVIEW QUESTIONS
………………………………………………………………………………………………
General Questions about GSM
1. What are the three services offered by GSM? Explain each of them briefly.
2. Which uplink/downlink spectrum is allocated to GSM-900?
3. Which uplink/downlink spectrum is allocated to DCS-1800?
4. How many carrier frequencies are there in GSM-900/DCS-1800? How much
is the separation between the carrier frequencies?
5. What is Ciphering? Why do we need it? Name the algorithm(s) used in it?
6. What is Authentication? Why do we need it? Name the algorithm(s) used in
it?
7. What is equalisation? Why do we need it?
8. What is Interleaving? Why do we need it?
9. Why do we need digitisation?
10. Explain Speech Coding.
11. What is channel coding?
12. What do you mean by Frequency re-use?
13. What is Cell Splitting?
14. Name the interfaces between a) BTS and MS b) BTS and BSC c) BSS and
MSC d) TRAU and BSC e)BSC and PCU
15. What are LAPD and LAPDm?
16. What is WPS?
17. What is MA?
18. What is MAIO?
2. Created by: Faisal Adnan Siddiqui
19. What is the difference between Synthesised Frequency Hopping and Base
Band Frequency Hopping?
20. What is Cycling Frequency Hopping?
21. What is HSN? How do we apply it?
22. What is DTX? Why is it used?
23. What is DRX? Why do we need it?
24. What is the gross data rate of GSM?
25. What is Erlangs? What is meant by GoS?
26. We use two different bands for GSM/DCS communications; GSM900 and
DCS-1800. Which one is the better of the two in terms of quality and
coverage?
27. What is TA? Why do we need TA?
28. What is meant by Location Area?
29. What is location update? Why do we need location update?
30. What is meant by IMSI, TMSI, IMEI and MS-ISDN? Why they are needed?
31. What is ARFCN? Which ARFCNs are allocated to Ufone?
32. Explain Power Control.
33. What is the difference between FDD and TDD?
34. What is an extended cell? How does it impact the system?
Channels and TDMA structure
35. Why do we use Multiple Access Schemes? What is the difference between
FDMA, TDMA and CDMA?
36. Which channel(s) is used for SMS?
3. Created by: Faisal Adnan Siddiqui
37. Which channel is used by MS to request access to the network?
38. What is AGCH?
39. Why do we need SDCCH?
40. What is a physical channel? How do we differentiate between physical and
logical channels?
41. What are TDMA frames, multiframes, superframes and hyperframes?
42. Why do we need FCCH, SCH and BCCH?
43. Why do we need SACCH?
44. What is the purpose of PCH and CBCH?
45. Do we keep BCCH on a hopping radio? Give the reason to support your
answer.
46. How much delay is present between downlink and uplink frames? Why do
we need this delay?
47. Explain the structure of a Traffic Multiframe. Why do we need SACCH and
Idle bursts in a traffic multiframe?
48. How is a FACCH formed? When is a FACCH used?
49. What are bursts? Explain various types of bursts.
Radio Propagation and Antennas
50. What is VSWR? Why do we need it?
51. What do you mean by EIRP?
52. What is Polarisation? What are the types of polarisation?
53. What is fading? What are its different types: a) Based on Multipath time
delay spread b) Based on Doppler Spread?
54. What is Rayleigh Fading?
55. What is multipath fading?
4. Created by: Faisal Adnan Siddiqui
56. How can we minimise multipath fading?
57. What are the different types of diversity?
58. Explain various types of Antenna Diversity?
59. Explain Frequency Diversity.
60. Explain Time Diversity.
61. What are the basic mechanisms of propagation?
62. What do you mean by Diffraction?
63. What is knife-edge diffraction?
64. What is Scattering?
65. What is FSPL?
66. What is meant by Fresnel zone and Fraunhofer zone?
67. What is beamwidth? What is the relation of beamwidth to length of antenna?
68. Define: a) Bandwidth, b) 3dB Bandwidth and c) absolute Bandwidth d)
Coherence Bandwidth e) Modulation Bandwidth f) Null-to-Null Bandwidth?
69. What do we understand from the terms a) SNR b) F/B ratio?
Handovers
70. What are the types of Handovers (intra-bsc, inter-msc, etc)?
71. What can be the reasons of Handover Failure?
72. What is the difference between a soft handover and a hard handover?
73. What are SYNC handovers? How are the different from asynchronous
handovers?
74. What are emergency handovers?
75. What are the different types of Handovers? (PBGT, Quality, Level, etc)
76. How do we classify the handovers on the basis of decision making?
5. Created by: Faisal Adnan Siddiqui
77. What are Vertical and Horizontal handovers?
78. What is “Multilayer Handoff” Strategy? What is “Ping pong effect” and
“take-back”?
79. Who makes the handover decisions in GSM?
80. What is the role of the MSC in handovers?
81. What is the role of the MS in handovers?
Modulation
82. Which modulation scheme is used in GSM? Explain.
83. What is the difference between PSK, ASK and FSK?
84. What are QPSK and OQPSK?
85. What is MSK? What is its application in GSM?
86. What is QAM? What is its application in GSM?
87. What is meant by PAM and PCM? What is its application in GSM?
88. Explain FDM, TDM and OFDM.
89. Which modulation scheme is used in GPRS? In EDGE? Explain/Compare.
Drive Testing
90. What is C/I?
91. What is C/A?
92. What is RxQual? How do we relate it to BER?
93. What is the difference between BER-Full and BER-Sub?
94. What is SQI? Why do we prefer it over RxQual?
95. What is BSIC? Why do we need it?
96. What is AMR?
6. Created by: Faisal Adnan Siddiqui
97. What can be the reasons of a Call drop?
98. What are counters? Why do we need them?
99. When do we need drive test?
100. What is cell-reselection?
101. What are C1 & C2?
102. What is call re-establishment?
103. Why do we make “short calls” and “long calls” during drive test?
104. What do you mean by CEFR and CSSR?
105. What is RSSI?
106. What is the difference between RxLev and RxQual?
107. What is the difference between FER and BER?
Procedures
108. What is cell selection? How does MS select a cell?
109. Explain the call flow for MOC and MTC.
110. Handover procedures.
111. How does a MS get “registered” with the network? (Explain IMSI
attach procedure)
GPRS and EDGE
112. What is GPRS?
113. What is the basic difference between GSM and GPRS architecture?
114. What makes GPRS technology different from traditional GSM?
115. What are the functions of GGSN and SGSN?
7. Created by: Faisal Adnan Siddiqui
116. How many coding schemes are used in GPRS? Why are they
important?
117. What is the gross data rate offered by GPRS and EDGE?
118. What is EDGE? How is it different from normal GSM/GPRS?
119. How do we classify GPRS terminals?
GSM System Architecture
120. What are the main components of BSS?
121. What are the main components of NSS?
122. Why do we need HLR and VLR?
123. Why do we need EIR and AuC?
124. What is RBS?
125. What are the paging limitations of a BSC?
126. What is a coupling system?
127. What do we mean by E1 and T1?
Case Study 1
Case Study: 1 km high tower in Karachi. Discuss.
Case Study 2
Case Study: Two cells having same BCCH. Discuss.
Case Study 3
Case Study: LAC size. The whole Karachi being given one LAC VS each cell
having its own LAC.