61. What could be the cause of soft handover failure?
Answer –
• Undefined neighbors
• One way Neighbor definition
• UE issue.
• Resource unavailable at target NodeB.
• Inadequate SHO threshold defined.
62. What are the three sets in handover?
Answer –
Active Set
Monitored Set
Detected Set
63. What are the major differences between GSM and UMTS handover decision?
Answer –
GSM:
• Time-based mobile measures of RxLev and RxQual – mobile sends measurement report every SACH period (480ms).
• BSC instructs mobile to handover based on these reports.
UMTS:
• Event-triggered reporting – UE sends a measurement report only on certain event “triggers”.
• UE plays more part in the handover decision.
64. What are the events 1a, 1b, 1c, etc.?
Answer –
e1a – a Primary CPICH enters the reporting range, i.e. add a cell to active set.
e1b – a primary CPICH leaves the reporting range, i.e. removed a cell from active set.
e1c – a non-active primary CPICH becomes better than an active primary CPICH, i.e. replace a cell.
e1d: change of best cell.
e1e: a Primary CPICH becomes better than an absolute threshold.
e1f: a Primary CPICH becomes worse than an absolute threshold.
65. What are event 2a-2d and 3a-3d?
Answer –
Events 2a-2d are for inter-frequency handover measurements and events 3a-3d are for IRAT handover measurements.
e3a: the UMTS cell quality has moved below a threshold and a GSM cell quality had moved above a threshold.
e3b: the GSM cell quality has moved below a threshold.
e3c: the GSM cell quality has moved above a threshold.
e3d: there was a change in the order of best GSM cell list.
66. What may happen when there’s a missing neighbor or an incorrect neighbor?
Answer –
• Access failure and handover failure: may attempt to access to a wrong scrambling code.
• Dropped call: UE not aware of a strong scrambling code, strong interference.
• Poor data throughput.
• Poor voice quality.
• Etc.
67. How is inter-frequency Handover triggered?
Answer –
The network decides that inter frequency measurements need to be performed and sends the MEASUREMENT CONTROL MESSAGE with Measurement type set to Inter-Frequency measurements. Generally it will set an Event as well along with the measurements. The following are list of Events that can trigger Measurement Report.
• Event 2a: Change of Best Frequency
• Event 2b: The estimated quality of the currently used frequency is below a certain threshold and the estimated quality of a non-used frequency is above a certain threshold
• Event 2c: The estimated quality of a non-used frequency is above a certain threshold
• Event 2d: The estimated quality of the currently used frequency is below a certain threshold
• Event 2e: The estimated quality of a non-used frequency is below a certain threshold
• Event 2f: The estimated quality of the currently used frequency is above a certain threshold
The Inter-Frequency Handover Evaluation bases its decision on P-CPICH quality measures on the currently used frequency and on one or more non-used frequencies. If the evaluation result is positive, one cell on a non-used frequency is proposed to Inter-Frequency handover Execution.
Inter-Frequency Handover is a hard handover where the UE is ordered by the network to tune to another frequency. This means that there will be small interruptions in the data flow to and from the UE.
68. What kind of Handover takes place in Load Sharing?
Answer –
It’s a blind handover to the co-located cell. IFHO i.e.
69. What do you understand by IFHO?
Answer –
IFHO – Inter Frequency Handover
70. What do you understand by Directed Retry?
Answer –
When there is a co-existing GSM RAN, excess traffic in a WCDMA cell may be off-loaded to GSM
If a call is chosen for Directed Retry to GSM, the request for the speech RAB will be rejected with cause "Directed retry" and then a request is made to the core network to relocate the UE to a specific GSM cell, using the Inter-RAT handover procedure. This handover is a blind one since the target cell is chosen not based on UE measurements. Therefore, the target cell must be co-located with the WCDMA cell. Co-located GSM cells are assumed to have similar coverage and accessibility as their respective WCDMA cells.
Wednesday, January 5, 2011
UMTS Question and answer part 3
44. Which link is required to perform Inter RNC SHO?
Answer -Iur
45. What is “noise rise”? What does a higher noise rise mean in terms of network loading?
Answer - For every new user added to the service, additional noise is added to the network. That is, each new user causes a “noise rise”. In theory, the “noise rise” is defined as the ratio of total received wideband power to the noise power. Higher “noise rise” value implies more users are allowed on the network, and each user has to transmit higher power to overcome the higher noise level. This means smaller path loss can be tolerated and the cell radius is reduced. To summarize, a higher noise rise means higher capacity and smaller footprint, a lower noise rise means smaller capacity and bigger footprint.
46. What is Pilot Pollution?
Answer - Simply speaking, when the number of strong cells exceeds the active set size, there is “pilot pollution” in the area. Typically the active set size is 3, so if there are more than 3 strong cells then there is pilot pollution.
Definition of “strong cell”: pilots within the handover window size from the strongest cell. Typical handover window size is between 4 to 6dB. For example, if there are more than 2 cells (besides the strongest cell) within 4dB of the strongest cell then there is pilot pollution.
47. How many fingers does a UE rake receiver have?
Answer – 4
48. What is “compressed mode”?
Answer - Compressed mode is a physical layer function that allows the UE to temporarily tune to another frequency, and measure the RF environment of another UMTS frequency (e.g. IFHO) or another technology (e.g. IRAT), while maintaining an existing dedicated channel
49. When in 3-way soft handover, if a UE receives power down request from one cell and power up request from the other 2 cells, should the UE power up or down and why?
Answer - UE will power down because if a cell is able to sustain a good connection with one cell on lower power level it will discard power up messages from other cells. It also helps in maintaining low interference level for other surrounding UE’s.
50. Suppose two UE are served by the same cell, the UE with weaker link (poor RF condition) uses more “capacity”, why does this mean?
Answer -The UE with weaker RF link will require NodeB to transmit higher traffic power in order to reach the UE, resulting in less power for other UE – therefore consumes more “capacity
51. Under what circumstances can a NodeB reach its capacity? What are the capacity limitations?
Answer -NodeB reaches its maximum transmit power, runs out of its channel elements, uplink noise rise reaches its design target, etc.
52. What is “cell breathing” and why?
Answer - The cell coverage shrinks as the loading increases, this is called cell breathing.
In the uplink, as more and more UE are served by a cell, each UE needs to transmit higher power to compensate for the uplink noise rise. As a consequence, the UE with weaker link (UE at greater distance) may not have enough power to reach the NodeB – therefore a coverage shrinkage.
In the downlink, the NodeB also needs to transmit higher power as more UE are being served. As a consequence UE with weaker link (greater distance) may not be reachable by the NodeB.
53. If you have 3 cells in your Active Set and a drop call occurs, which Cell a Drop call would be pegged?
Answer - Serving Cell in Active Set
54. Is UMTS an uplink-limited or downlink-limited system?
Answer – Initially, A typical WCDMA network is Uplink Limited. Later a Loaded Network becomes Downlink Limites.
55. What is OCNS?
Answer - Orthogonal Carrier Noise Simulator
56. Briefly describe Capacity Management and its functions?
Answer - Capacity Management is responsible for the control of the load in the cell. It consists of 3 main functions:
1. Dedicated Monitored Resource Handling: tracks utilization of critical resources of the system.
2. Admission Control: accepts/refuses admission requests based on the current load on the dedicated monitored resources and the characteristics of the request
3. Congestion Control: detects/resolves overload situations
57. What Resources are monitored for Capacity Management?
Answer –
DL Power
Received Total Wideband power
OVSF Codes
RBS Channel Elements
58. What Radio Measurements are used for Congestion Monitoring?
Answer –
Downlink Received Power
Uplink Received Total Wideband Power
59. Are System Information Blocks (SIB) transmitted all the time?
Answer - Yes
60. How does UE camp (synchronize) to a NodeB?
Answer –
1. UE uses the primary synchronization channel (P-SCH) for slot alignment (TS synchronization).
2. After aligning to NodeB time slot, UE then uses secondary synchronization channel (S-SCH) to obtain frame synchronization and scrambling code group identification.
3. UE then uses scrambling code ID to obtain CPICH, thus camping to a NodeB.
Answer -Iur
45. What is “noise rise”? What does a higher noise rise mean in terms of network loading?
Answer - For every new user added to the service, additional noise is added to the network. That is, each new user causes a “noise rise”. In theory, the “noise rise” is defined as the ratio of total received wideband power to the noise power. Higher “noise rise” value implies more users are allowed on the network, and each user has to transmit higher power to overcome the higher noise level. This means smaller path loss can be tolerated and the cell radius is reduced. To summarize, a higher noise rise means higher capacity and smaller footprint, a lower noise rise means smaller capacity and bigger footprint.
46. What is Pilot Pollution?
Answer - Simply speaking, when the number of strong cells exceeds the active set size, there is “pilot pollution” in the area. Typically the active set size is 3, so if there are more than 3 strong cells then there is pilot pollution.
Definition of “strong cell”: pilots within the handover window size from the strongest cell. Typical handover window size is between 4 to 6dB. For example, if there are more than 2 cells (besides the strongest cell) within 4dB of the strongest cell then there is pilot pollution.
47. How many fingers does a UE rake receiver have?
Answer – 4
48. What is “compressed mode”?
Answer - Compressed mode is a physical layer function that allows the UE to temporarily tune to another frequency, and measure the RF environment of another UMTS frequency (e.g. IFHO) or another technology (e.g. IRAT), while maintaining an existing dedicated channel
49. When in 3-way soft handover, if a UE receives power down request from one cell and power up request from the other 2 cells, should the UE power up or down and why?
Answer - UE will power down because if a cell is able to sustain a good connection with one cell on lower power level it will discard power up messages from other cells. It also helps in maintaining low interference level for other surrounding UE’s.
50. Suppose two UE are served by the same cell, the UE with weaker link (poor RF condition) uses more “capacity”, why does this mean?
Answer -The UE with weaker RF link will require NodeB to transmit higher traffic power in order to reach the UE, resulting in less power for other UE – therefore consumes more “capacity
51. Under what circumstances can a NodeB reach its capacity? What are the capacity limitations?
Answer -NodeB reaches its maximum transmit power, runs out of its channel elements, uplink noise rise reaches its design target, etc.
52. What is “cell breathing” and why?
Answer - The cell coverage shrinks as the loading increases, this is called cell breathing.
In the uplink, as more and more UE are served by a cell, each UE needs to transmit higher power to compensate for the uplink noise rise. As a consequence, the UE with weaker link (UE at greater distance) may not have enough power to reach the NodeB – therefore a coverage shrinkage.
In the downlink, the NodeB also needs to transmit higher power as more UE are being served. As a consequence UE with weaker link (greater distance) may not be reachable by the NodeB.
53. If you have 3 cells in your Active Set and a drop call occurs, which Cell a Drop call would be pegged?
Answer - Serving Cell in Active Set
54. Is UMTS an uplink-limited or downlink-limited system?
Answer – Initially, A typical WCDMA network is Uplink Limited. Later a Loaded Network becomes Downlink Limites.
55. What is OCNS?
Answer - Orthogonal Carrier Noise Simulator
56. Briefly describe Capacity Management and its functions?
Answer - Capacity Management is responsible for the control of the load in the cell. It consists of 3 main functions:
1. Dedicated Monitored Resource Handling: tracks utilization of critical resources of the system.
2. Admission Control: accepts/refuses admission requests based on the current load on the dedicated monitored resources and the characteristics of the request
3. Congestion Control: detects/resolves overload situations
57. What Resources are monitored for Capacity Management?
Answer –
DL Power
Received Total Wideband power
OVSF Codes
RBS Channel Elements
58. What Radio Measurements are used for Congestion Monitoring?
Answer –
Downlink Received Power
Uplink Received Total Wideband Power
59. Are System Information Blocks (SIB) transmitted all the time?
Answer - Yes
60. How does UE camp (synchronize) to a NodeB?
Answer –
1. UE uses the primary synchronization channel (P-SCH) for slot alignment (TS synchronization).
2. After aligning to NodeB time slot, UE then uses secondary synchronization channel (S-SCH) to obtain frame synchronization and scrambling code group identification.
3. UE then uses scrambling code ID to obtain CPICH, thus camping to a NodeB.
UMTS Question and answer part 2
22. What is cell selection criterion?
Answer - Cell selection is based on:
•Qmean: the average SIR of the target cell.
•Qmin: minimum required SIR.
•Pcompensation: a correction value for difference UE classes.
S = Qmean - Qmin - Pcompensation
•If S>0 then the cell is a valid candidate.
•A UE will camp on the cell with the highest S.
23. Idle Mode Behaviour is managed by System information send on which L3 Channel?
Answer – BCH
24. How many Radio Bearers (RB) are involved in CS voice call?
Answer – 3
25. How many Service Radio Bearers (SRB) are involved in CS voice call?
Answer – 4
26. SCH channel consists of how many chips?
Answer -256 chips
27. What do you understand by DRX cycle?
Answer - The UE listens to the PICH only at certain predefined times, reducing power consumption. The periodicity of these searches is set by the system and the time interval is called Discontinuous Reception (DRX) cycle.
Different DRX cycles are used for circuit switched and packet switched services in Idle mode. A separate DRX cycle is also used to page Connected mode UEs in state URA_PCH.
28. Cell Reselection is valid in both Idle and in which Sate in Connected mode?
Answer - CELL FACH
29. Difference between PICH and PCH?
Answer - PICH-Paging Indicator Channel
PCH-Paging Channel
PICH is used to indicate UE to when it should read to S-CCPCH (Carries PCH) whereas PCH is used to carry RRC Message “Paging type 1” which contains actual Paging information.
30. When is System information sent to UE?
Answer - The system information is regularly broadcast to the UE on the BCCH. When a parameter in the system information is changed, all UE in a cell are notified by a paging message or by a system information change indication message.
31. Explain Timer T3212?
Answer -Periodic LA and RA updating is used to notify the network of the UEs availability, and to avoid unnecessary paging attempts for a UE that has lost coverage and is not able to inform the CN that it is inactive.
The periodic LA update procedure is controlled by a timer, called t3212, which gives the time interval between two consecutive periodic location updates. The value is sent by the WCDMA RAN to UEs on the BCCH.
32. Explain Near far effect?
Answer;-All users use the same bandwidth at the same time and therefore users interfere with one another. Due to the propagation path loss, the signal received by the base station from a UE close to the base station will be stronger than the Signal received from another terminal located at the boundary. Hence, the distant user will be dominated by the close user. This is called the near-far effect. To achieve a considerable capacity, all signals, irrespective of distance, should arrive at the base station with the same mean power. A solution to this problem is power control, which attempts to achieve the same mean received power for each user.
33. Name three loops in Power control In WCDMA? Explain them briefly.
Answer; - Open Loop
Inner Loop
Outer Loop
Open Loop Power control
The open-loop power control technique requires that the transmitting entity measures the channel interference and adjusts its transmission power accordingly. This can be done quickly, but the problem is that the interference estimation is done on the received signal, and the transmitted signal probably uses a different frequency, which differs from the received frequency by the system’s duplex offset. As uplink and downlink fast fading (on different frequency carriers) do not correlate, this method gives the right power values only on average.
Inner Loop
In this method the received signal-to interference ratio (SIR) is measured over a 667-microsecond period (i.e., one time slot), and based on that value, a decision is made about whether to increase or decrease the transmission power in the other end of the connection. Note that the delay inherent in this closed-loop method is compensated for by making the measurements over a very short period of time. The transmit power control (TPC) bits are sent in every time slot within the uplink and the downlink. There is not a neutral signal; all power control signals contain either an increase or decrease command.
Outer Loop
The outer loop power control functions within the base station system, and adjusts the required SIR value (SIRtarget), which is then used in the inner loop control. Different channel types, which can be characterized by, for example, different coding and interleaving methods, constitute a channel’s parameters. Different channel parameters may require different SIRtarget values. The final result of the transmission process can only be known after the decoding process, and the resulting quality parameter is then used to adjust the required SIR value. If the used SIR value still gives a low quality bit stream, then the outer loop power control must increase the SIRtarget value. This change in the outer loop will trigger the inner loop power control to increase the mobile station transmission power accordingly
34. What is SIR?
Answer - SIR is the Signal-to-Interference Ratio – the ratio of the energy in dedicated physical control channel bits to the power density of interference and noise after dispreading.
35. How many time Inner Loop Power Control happens and what type of fading it compensates?
Answer - 1500Hz and compensates Fast Fading.
36. What is BLER?
Answer - Block Error Rate
37. How is Initial RACH Power is calculated?
Answer - The initial power on the PRACH - the power of the first preamble - is determined according to equation
P_PRACH = L_PCPICH + RTWP + constantValueCprach
Where L_PCPICH is the path loss estimated by UE since it knows transmit & receive CPICH power
RTWP is received Total Wideband Power(uplink interference) measured by RBS .
constantValueCprach is used by the UE to calculate the initial power on the PRACH . This parameter is configurable and decides at which level below RTWP preamble ramping will start.
38. What power RACH message Control Part is sent?
Answer - The power of the control part of the RACH message is determined by the power of the last transmitted preamble and by a configurable offset powerOffsetPpm
39. Briefly describe why open loop power control is needed and how it works?
Answer -Open Loop power control is used when no feedback mechanism is possible. An estimate of the required power is made from measurements and system information.
This is used for initial network access and finding initial power settings during dedicated mode.
40. Explain the functionality of TPC?
Answer – During Power Control, Transmit Power control(TPC) commands are used to power up or power down based on SIR target in the step of 0.5 dB ( 1 dB if the connection is made over Iur).
41. How many types of handovers are there in UMTS?
Answer –
Soft/Softer Handover
Inter Frequency Handover
Inter RAT Handover
Core Network Hard Handover
Service based handover to GSM
HSDPA Mobility
42. Explain Soft and Softer handover? Give some advantage and disadvantage for soft handover. What is the target for soft handover in WCDMA networks?
Answer - In Soft Handover, the UE connection consists of at least two radio links established with cells belonging to different RBSs. In Softer handover, the UE connection consists of at least two radio links established with cells belonging to the same RBS.
It acts as macro diversity since UE is connected to more than one radio link at any given point, adds redundancy and reduces interference.
However there is a tradeoff between soft/softer handover & system capacity.
A UE involved in Soft/Softer Handover uses several radio links, more DL channelization codes, and more DL power than a single-link connection. Consequently, if all the UEs connected to a particular RNC are considered, more resources are needed in the RBSs, more resources over the Iub and Iur interfaces, and more resources in the RNC. For this reason, the number of radio links involved in the Soft/Softer handover must be limited
A typical target for soft handover in WCDMA network is less than or equal to 30%
43. Define Active Set? Pros and Cons of having a small or longer Active Set.
Answer - Active Set consists of group of cells that takes part in soft/softer handover & measure by UE.
Typical size of Active set is 3 or 4 & generally a standard practice in all WCDMA networks.
A small active set size may provide more resources available due to less soft/softer handover but at the expense of handover gain thereby reducing the capacity & link redundancy
Answer - Cell selection is based on:
•Qmean: the average SIR of the target cell.
•Qmin: minimum required SIR.
•Pcompensation: a correction value for difference UE classes.
S = Qmean - Qmin - Pcompensation
•If S>0 then the cell is a valid candidate.
•A UE will camp on the cell with the highest S.
23. Idle Mode Behaviour is managed by System information send on which L3 Channel?
Answer – BCH
24. How many Radio Bearers (RB) are involved in CS voice call?
Answer – 3
25. How many Service Radio Bearers (SRB) are involved in CS voice call?
Answer – 4
26. SCH channel consists of how many chips?
Answer -256 chips
27. What do you understand by DRX cycle?
Answer - The UE listens to the PICH only at certain predefined times, reducing power consumption. The periodicity of these searches is set by the system and the time interval is called Discontinuous Reception (DRX) cycle.
Different DRX cycles are used for circuit switched and packet switched services in Idle mode. A separate DRX cycle is also used to page Connected mode UEs in state URA_PCH.
28. Cell Reselection is valid in both Idle and in which Sate in Connected mode?
Answer - CELL FACH
29. Difference between PICH and PCH?
Answer - PICH-Paging Indicator Channel
PCH-Paging Channel
PICH is used to indicate UE to when it should read to S-CCPCH (Carries PCH) whereas PCH is used to carry RRC Message “Paging type 1” which contains actual Paging information.
30. When is System information sent to UE?
Answer - The system information is regularly broadcast to the UE on the BCCH. When a parameter in the system information is changed, all UE in a cell are notified by a paging message or by a system information change indication message.
31. Explain Timer T3212?
Answer -Periodic LA and RA updating is used to notify the network of the UEs availability, and to avoid unnecessary paging attempts for a UE that has lost coverage and is not able to inform the CN that it is inactive.
The periodic LA update procedure is controlled by a timer, called t3212, which gives the time interval between two consecutive periodic location updates. The value is sent by the WCDMA RAN to UEs on the BCCH.
32. Explain Near far effect?
Answer;-All users use the same bandwidth at the same time and therefore users interfere with one another. Due to the propagation path loss, the signal received by the base station from a UE close to the base station will be stronger than the Signal received from another terminal located at the boundary. Hence, the distant user will be dominated by the close user. This is called the near-far effect. To achieve a considerable capacity, all signals, irrespective of distance, should arrive at the base station with the same mean power. A solution to this problem is power control, which attempts to achieve the same mean received power for each user.
33. Name three loops in Power control In WCDMA? Explain them briefly.
Answer; - Open Loop
Inner Loop
Outer Loop
Open Loop Power control
The open-loop power control technique requires that the transmitting entity measures the channel interference and adjusts its transmission power accordingly. This can be done quickly, but the problem is that the interference estimation is done on the received signal, and the transmitted signal probably uses a different frequency, which differs from the received frequency by the system’s duplex offset. As uplink and downlink fast fading (on different frequency carriers) do not correlate, this method gives the right power values only on average.
Inner Loop
In this method the received signal-to interference ratio (SIR) is measured over a 667-microsecond period (i.e., one time slot), and based on that value, a decision is made about whether to increase or decrease the transmission power in the other end of the connection. Note that the delay inherent in this closed-loop method is compensated for by making the measurements over a very short period of time. The transmit power control (TPC) bits are sent in every time slot within the uplink and the downlink. There is not a neutral signal; all power control signals contain either an increase or decrease command.
Outer Loop
The outer loop power control functions within the base station system, and adjusts the required SIR value (SIRtarget), which is then used in the inner loop control. Different channel types, which can be characterized by, for example, different coding and interleaving methods, constitute a channel’s parameters. Different channel parameters may require different SIRtarget values. The final result of the transmission process can only be known after the decoding process, and the resulting quality parameter is then used to adjust the required SIR value. If the used SIR value still gives a low quality bit stream, then the outer loop power control must increase the SIRtarget value. This change in the outer loop will trigger the inner loop power control to increase the mobile station transmission power accordingly
34. What is SIR?
Answer - SIR is the Signal-to-Interference Ratio – the ratio of the energy in dedicated physical control channel bits to the power density of interference and noise after dispreading.
35. How many time Inner Loop Power Control happens and what type of fading it compensates?
Answer - 1500Hz and compensates Fast Fading.
36. What is BLER?
Answer - Block Error Rate
37. How is Initial RACH Power is calculated?
Answer - The initial power on the PRACH - the power of the first preamble - is determined according to equation
P_PRACH = L_PCPICH + RTWP + constantValueCprach
Where L_PCPICH is the path loss estimated by UE since it knows transmit & receive CPICH power
RTWP is received Total Wideband Power(uplink interference) measured by RBS .
constantValueCprach is used by the UE to calculate the initial power on the PRACH . This parameter is configurable and decides at which level below RTWP preamble ramping will start.
38. What power RACH message Control Part is sent?
Answer - The power of the control part of the RACH message is determined by the power of the last transmitted preamble and by a configurable offset powerOffsetPpm
39. Briefly describe why open loop power control is needed and how it works?
Answer -Open Loop power control is used when no feedback mechanism is possible. An estimate of the required power is made from measurements and system information.
This is used for initial network access and finding initial power settings during dedicated mode.
40. Explain the functionality of TPC?
Answer – During Power Control, Transmit Power control(TPC) commands are used to power up or power down based on SIR target in the step of 0.5 dB ( 1 dB if the connection is made over Iur).
41. How many types of handovers are there in UMTS?
Answer –
Soft/Softer Handover
Inter Frequency Handover
Inter RAT Handover
Core Network Hard Handover
Service based handover to GSM
HSDPA Mobility
42. Explain Soft and Softer handover? Give some advantage and disadvantage for soft handover. What is the target for soft handover in WCDMA networks?
Answer - In Soft Handover, the UE connection consists of at least two radio links established with cells belonging to different RBSs. In Softer handover, the UE connection consists of at least two radio links established with cells belonging to the same RBS.
It acts as macro diversity since UE is connected to more than one radio link at any given point, adds redundancy and reduces interference.
However there is a tradeoff between soft/softer handover & system capacity.
A UE involved in Soft/Softer Handover uses several radio links, more DL channelization codes, and more DL power than a single-link connection. Consequently, if all the UEs connected to a particular RNC are considered, more resources are needed in the RBSs, more resources over the Iub and Iur interfaces, and more resources in the RNC. For this reason, the number of radio links involved in the Soft/Softer handover must be limited
A typical target for soft handover in WCDMA network is less than or equal to 30%
43. Define Active Set? Pros and Cons of having a small or longer Active Set.
Answer - Active Set consists of group of cells that takes part in soft/softer handover & measure by UE.
Typical size of Active set is 3 or 4 & generally a standard practice in all WCDMA networks.
A small active set size may provide more resources available due to less soft/softer handover but at the expense of handover gain thereby reducing the capacity & link redundancy
UMTS Question and answer part 1
1. What is Significance of Eb/No? On what factors it is dependent? who provides Eb/No? What is typical Eb/No for AMR 12.2 for Node B and MS?
Answer - Eb_No is related to QOS of a service which in terms related to bit error rate. Technically it is the minimum signal to noise needed by infrastructure equipment after despreading it signal. This is a value used to compare different infrastructure vendors. Eb_No changes with the service type. Typically Eb_No for AMR 12.2 is ~ 4 db for node B and 8 dB for MS. It is infrastructure vendor (NSN) provides the Eb_No for Node B.
The Eb/N0 value is the value that needs to be reached for insuring the targeted service quality. This is the ratio between the energy per bit for the related service over the noise spectral efficiency over the whole spreading band.
The spread signal is characterized by the ratio of the energy per chip over the spectral noise density Ec/N0.
2. What effect is there on signal by spreading and dispreading?
Answer - Spreading will increase the bandwidth of a as signal. A signal of 10 Kb/s will become 40 Kb/s after spreading and will become 10 Kb/s after despreading.
The processing gain term expresses the gain achieved by spreading a narrow band signal over a wideband spectrum.
This gain is the ratio between the spreading chip rate and the actual service bit rate measured at the RLC level
3. Define Processing Gain.
Answer - Processing Gain is ratio between rate of spreaded signal and rate of non spreaded signal.
PG= 10 log (Chip rate /Bit rate)
4. What is a chip rate of WCDMA System? How much is the bandwidth required for WCDMA?
Answer: - 3840 Kc/s. FDD 5 MHZ of paired band. TDD 5 MHz only.
5. What is the processing gain for 384 Kb/s service?
Answer:- =10*Log(3840/384)
=10*log (10)
=10*1
=10
6. What is the relationship of SF and data rate?
Answer; - They are inversely proportional. Lower the SF higher the data rate.
7. What is the relationship between SF and power required?
Answer - The lower the SF, the more power required.
8. What is the relationship with SF and coverage area of different services?
Answer: - They are directly proportional. Lower SF will have less coverage area.
For example Coverage area decreases with increased throughput. If we compare 12.2 Kb/s and 384 Kb/s coverage area.12.2 kb/s coverage area will be bigger then 384 Kb/s coverage area.
9. What is the family of codes used for Chanelization in WCDMA
Answer: - Orthogonal Variable Spreading Factor.(OVSF)
10. What is the minimum and maximum SF in Downlink and uplink for FDD Mode?
Answer; - Minimum of 4 and maximum of 512 chips in downlink
Minimum of 4 and maximum of 256 chips in uplink
11. What is the usage of Channelization code in downlink and uplink?
Answer;- Uplink separation of physical data (DPDCH) and control channel (DPCCH) from same terminal.
Downlink separation of downlink connections to different users within one cell.
12. What is the Chanelization code used for PCPICH (PILOT CHANNEL)?
Answer: - C ch(256,0)
13. What is a typical CPICH power?
Answer - CPICH power typically takes about 8~10% of the total NodeB power. For a 20W (43dBm) NodeB, CPICH is around 2W (35.1 ~ 33dBm).
In urban areas where in-building coverage is taken care of by in-building installations, the CPICH may sometimes go as low as 5% because:
1) The coverage area is small since users are close to the site, and
2) More power can be allocated to traffic channels.
14. How much power usually a NodeB is allocated to control channels?
Answer - The power allocated to control channels may depend on equipment vendor recommendation. Typically no more than 20% of the total NodeB power is allocated to control channels, including CPICH. However, if HSDPA is deployed on the same carrier then the total power allocated to control channel may go up to 25 to 30% because of the additional HSDPA control channels required.
15. What is the usage of scrambling code in WCDMA for both downlink and uplink?
Answer; - There is only one frequency in Downlink. SC is used to separate cells. In uplink it is used to differentiate terminals.
16. How many numbers of SC codes available in Downlink and Uplink?
Answer; - Downlink 512, Uplink several millions.
17. What is the Modulation scheme is used in UMTS for voice service in Downlink and uplink?
Answer; - QPSK in downlink and HPSK (Hybrid Phase shift keying) in uplink.
18. How many slots are there in a WCDMA Frame? How big is a frame in ms. how many chips are there in a slot?
Answer: - WCDMA Frame is 15 slots wide. It is 10ms in length. There are 2560 chips in one slot.
Chip rate is 3840 Kc/s
Length of frame = 10 ms
Number of chips in a frame = 3840 *10=38400 chips
Number of chips in a slot = 38400/15= 2560 chips.
19. Give a simple definition of pole capacity?
Answer - The pole capacity is the theoretical maximum capacity of the system. In WCDMA, this capacity is only theoretical since, once reached, the system goes in an instable state that leads to its collapse. However it is still a reference for expressing the load.
The uplink noise increases with the loading exponentially. When the uplink noise approaches infinity then no more users can be added to a cell – and the cell loading is close to 100% and has reached its “pole capacity”.
Mathematically, to calculate the uplink pole capacity we need to know:
W: chip rate (for UMTS 3,840,000 chips per second)
R: user data rate (assuming 12,200 kbps for CS-12.2k)
f: other-cell to in-cell interference ratio (assuming 65%)
EbNo: Eb/No requirement (assuming 5dB)
AF: Activity factor (assuming 50%)
Pole Capacity = (W/R) / ((1+f) * AF * 10^(EbNo/10)) = 120.6
To calculate the downlink pole capacity we also need to know:
α: downlink channels orthogonality factor (assuming 55%)
Pole Capacity = (W/R) / ((1- α +f) * 10^(EbNo/10)) = 64.06
20. What is typical pole capacity for CS-12.2, PS-64, PS-128 and PS-384?
Answer - With same assumptions as above:
CS-12.2k: 120.6 (UL), 64.1 (DL).
PS-64k: 34.8 (UL), 12.8(DL).
PS-128k: 16.2 (UL), 8.4 (DL).
PS-384k: 16.2 (UL), 2.8 (DL).
PS-384k has only 128k on the uplink, therefore the uplink capacity is the same for both.
21. Different Idle mode tasks UE performs
Answer -In Idle mode, the UE has no connection to the radio network
Keeping UEs in Idle mode minimizes the use of resources both for the UEs and in the network. However, the UEs must still be able to access the system and be reached by the system with acceptable delays. For this, the following procedures need to be performed:
§ PLMN selection and reselection
§ Cell selection and reselection
§ Location Area (LA) and Routing Area (RA) updating
§ Paging
§ System information broadcast
Answer - Eb_No is related to QOS of a service which in terms related to bit error rate. Technically it is the minimum signal to noise needed by infrastructure equipment after despreading it signal. This is a value used to compare different infrastructure vendors. Eb_No changes with the service type. Typically Eb_No for AMR 12.2 is ~ 4 db for node B and 8 dB for MS. It is infrastructure vendor (NSN) provides the Eb_No for Node B.
The Eb/N0 value is the value that needs to be reached for insuring the targeted service quality. This is the ratio between the energy per bit for the related service over the noise spectral efficiency over the whole spreading band.
The spread signal is characterized by the ratio of the energy per chip over the spectral noise density Ec/N0.
2. What effect is there on signal by spreading and dispreading?
Answer - Spreading will increase the bandwidth of a as signal. A signal of 10 Kb/s will become 40 Kb/s after spreading and will become 10 Kb/s after despreading.
The processing gain term expresses the gain achieved by spreading a narrow band signal over a wideband spectrum.
This gain is the ratio between the spreading chip rate and the actual service bit rate measured at the RLC level
3. Define Processing Gain.
Answer - Processing Gain is ratio between rate of spreaded signal and rate of non spreaded signal.
PG= 10 log (Chip rate /Bit rate)
4. What is a chip rate of WCDMA System? How much is the bandwidth required for WCDMA?
Answer: - 3840 Kc/s. FDD 5 MHZ of paired band. TDD 5 MHz only.
5. What is the processing gain for 384 Kb/s service?
Answer:- =10*Log(3840/384)
=10*log (10)
=10*1
=10
6. What is the relationship of SF and data rate?
Answer; - They are inversely proportional. Lower the SF higher the data rate.
7. What is the relationship between SF and power required?
Answer - The lower the SF, the more power required.
8. What is the relationship with SF and coverage area of different services?
Answer: - They are directly proportional. Lower SF will have less coverage area.
For example Coverage area decreases with increased throughput. If we compare 12.2 Kb/s and 384 Kb/s coverage area.12.2 kb/s coverage area will be bigger then 384 Kb/s coverage area.
9. What is the family of codes used for Chanelization in WCDMA
Answer: - Orthogonal Variable Spreading Factor.(OVSF)
10. What is the minimum and maximum SF in Downlink and uplink for FDD Mode?
Answer; - Minimum of 4 and maximum of 512 chips in downlink
Minimum of 4 and maximum of 256 chips in uplink
11. What is the usage of Channelization code in downlink and uplink?
Answer;- Uplink separation of physical data (DPDCH) and control channel (DPCCH) from same terminal.
Downlink separation of downlink connections to different users within one cell.
12. What is the Chanelization code used for PCPICH (PILOT CHANNEL)?
Answer: - C ch(256,0)
13. What is a typical CPICH power?
Answer - CPICH power typically takes about 8~10% of the total NodeB power. For a 20W (43dBm) NodeB, CPICH is around 2W (35.1 ~ 33dBm).
In urban areas where in-building coverage is taken care of by in-building installations, the CPICH may sometimes go as low as 5% because:
1) The coverage area is small since users are close to the site, and
2) More power can be allocated to traffic channels.
14. How much power usually a NodeB is allocated to control channels?
Answer - The power allocated to control channels may depend on equipment vendor recommendation. Typically no more than 20% of the total NodeB power is allocated to control channels, including CPICH. However, if HSDPA is deployed on the same carrier then the total power allocated to control channel may go up to 25 to 30% because of the additional HSDPA control channels required.
15. What is the usage of scrambling code in WCDMA for both downlink and uplink?
Answer; - There is only one frequency in Downlink. SC is used to separate cells. In uplink it is used to differentiate terminals.
16. How many numbers of SC codes available in Downlink and Uplink?
Answer; - Downlink 512, Uplink several millions.
17. What is the Modulation scheme is used in UMTS for voice service in Downlink and uplink?
Answer; - QPSK in downlink and HPSK (Hybrid Phase shift keying) in uplink.
18. How many slots are there in a WCDMA Frame? How big is a frame in ms. how many chips are there in a slot?
Answer: - WCDMA Frame is 15 slots wide. It is 10ms in length. There are 2560 chips in one slot.
Chip rate is 3840 Kc/s
Length of frame = 10 ms
Number of chips in a frame = 3840 *10=38400 chips
Number of chips in a slot = 38400/15= 2560 chips.
19. Give a simple definition of pole capacity?
Answer - The pole capacity is the theoretical maximum capacity of the system. In WCDMA, this capacity is only theoretical since, once reached, the system goes in an instable state that leads to its collapse. However it is still a reference for expressing the load.
The uplink noise increases with the loading exponentially. When the uplink noise approaches infinity then no more users can be added to a cell – and the cell loading is close to 100% and has reached its “pole capacity”.
Mathematically, to calculate the uplink pole capacity we need to know:
W: chip rate (for UMTS 3,840,000 chips per second)
R: user data rate (assuming 12,200 kbps for CS-12.2k)
f: other-cell to in-cell interference ratio (assuming 65%)
EbNo: Eb/No requirement (assuming 5dB)
AF: Activity factor (assuming 50%)
Pole Capacity = (W/R) / ((1+f) * AF * 10^(EbNo/10)) = 120.6
To calculate the downlink pole capacity we also need to know:
α: downlink channels orthogonality factor (assuming 55%)
Pole Capacity = (W/R) / ((1- α +f) * 10^(EbNo/10)) = 64.06
20. What is typical pole capacity for CS-12.2, PS-64, PS-128 and PS-384?
Answer - With same assumptions as above:
CS-12.2k: 120.6 (UL), 64.1 (DL).
PS-64k: 34.8 (UL), 12.8(DL).
PS-128k: 16.2 (UL), 8.4 (DL).
PS-384k: 16.2 (UL), 2.8 (DL).
PS-384k has only 128k on the uplink, therefore the uplink capacity is the same for both.
21. Different Idle mode tasks UE performs
Answer -In Idle mode, the UE has no connection to the radio network
Keeping UEs in Idle mode minimizes the use of resources both for the UEs and in the network. However, the UEs must still be able to access the system and be reached by the system with acceptable delays. For this, the following procedures need to be performed:
§ PLMN selection and reselection
§ Cell selection and reselection
§ Location Area (LA) and Routing Area (RA) updating
§ Paging
§ System information broadcast
Tuesday, January 4, 2011
GSM RF INTERVIEW QUESTIONS
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?
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?
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?
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?
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?
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?
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 Delhi. Discuss.
Case Study 2
Case Study:
Two cells having same BCCH. Discuss.
Case Study 3
Case Study: LAC size. The whole Delhi being given one LAC VS each cell having its own LAC.
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?
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?
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?
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?
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?
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?
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 Delhi. Discuss.
Case Study 2
Case Study:
Two cells having same BCCH. Discuss.
Case Study 3
Case Study: LAC size. The whole Delhi being given one LAC VS each cell having its own LAC.
REPORT ON MASS COMMAND SOLUTION IN HLR
REPORT ON MASS COMMAND SOLUTION IN HLR
The is a report on usage and advantages of the tool Gonzales which is very useful for mass command exercises in HLR with respect to O&M activities .
1 Introduction
The Tool Gonzales has been used to execute mass commands in HLR with APG and its been found very effective as the output results are much faster than the mml commands or even HGMCI Command, This can help us all in Important migrations like HLR, SCP or SDP migrations. The tool has been tested successfully in few important migrations in north.
• The commands can be checked for any possible error with different procedure options.
• The average time for executing 1 Lac mml commands is around 7 mins..
• The mass execution is always recommended in off peak hours as processor load shoots up to 30-40%.
• Error result in executing any command will be captured in the output logs and can be checked and corrected.
2 Existing difficulties in Handling Mass Command Activities
1. Executing DT’s of mml commands from normal desktops is quite time consuming. Hence all the activities involving mass change in subscriber’s profile in HLR results in either delay in completion of the migration activities or errors in running DT’s manually are found out after quite some time which may be leading to revenue loss or customer dissatisfaction.
2. Sometimes, speed of mml session becomes very slow due to more parallel sessions resulting in much time for executing mml commands.
3. To manage the multiple mml sessions in HLR sometimes
3 How we can use this for O& M Activities
We can use Gonzales and IOCMI command to run any mml command in HLR or any AXE node. The testing has been done for HLR with APG only.The complete procedure can be simply divided into three parts.
3.1 Prepare the load file through Gonzales
All mml commands which are to be executed in HLR can be captured in a CMD file. It is always recommended to put a maximum of 1 Lac commands in a single CMD file as it keeps the processor load of CP within safe limit. Following is the procedure to make loadfile from the tool
• Use the File menu and click “Open” option.
• Select the CMD file where you have kept the commands.
• The screen will show you list of three processed files as shown below
• All three file will be automatically saved where CMD file is kept.
• The load file which is without any extension (first in the list as shown above) is the actual load file which is to be used further.
• It is recommended to rename the CMD filenames as acloadfile1 and next CMD filename as acloadfile2 and so on.
3.2 Transfer the load file in AP of HLR
After selecting the Load file, the next task is to transfer the file from your desktop to CP; the following steps will cover the procedure
• Login into the cluster of the the APG using pcAnywhere.
• Open the following directory in L drive of the APG
L:\FMS\Data\tmp\
• Make a new directory in the current “tmp” folder using mkdir command
mkdir Gonzales
• This will be a temporary folder which can be deleted after the completion of the activity.
• Now using the File Transfer Application of the APG.transfer the load file from your desktop to the following location of the APG.
L:\FMS\Data\tmp\gonzales
3.3 Executing Mass Commands
The Load file which is kept in the L drive of the APG is to be shifted to CP before running this load file. But we need a temporary CP file which will be used to keep the contents of this loadfile. ; the following steps will cover the procedure
• Create a CP file by using the command cpfmkfile, name the CP file as “acloadfile”
cpfmkfile -l 512 -c acloadfile relvolumsw
• Check the contents of the file by cpfls command.
L:\FMS\Data\tmp\gonzales>cpfls –l acloadfile
CPF FILE TABLE
FILE TYPE CMP VOLUME
ACLOADFILE reg yes RELVOLUMSW
TRANSFER QUEUE MODE
RLENGTH MAXSIZE MAXTIME REL ACTIVE SIZE USERS
512 0 0 [ 0R 0W]
• Copy the contents of loadfile from L:\FMS\Data\tmp\gonzales to CP file acloadfile by using ap command cpfport.
cpfport -i -m over L:\FMS\data\tmp\gonzales acloadfile
• Check the contents again after copying by cpfls command. Make sure acloadfile1 is there in the list
L:\FMS\Data\tmp\shooter>cpfls -ls acloadfile
CPF FILE TABLE
FILE TYPE CMP VOLUME
ACLOADFILE reg yes RELVOLUMSW
TRANSFER QUEUE MODE
RLENGTH MAXSIZE MAXTIME REL ACTIVE SIZE USERS
512 0 0 [ 0R 0W]
SUBFILES SIZE USERS
ACLOADFILE-LOADFILE1 17007 0 [ 0R 0W]
• Create a mml session.
• Now when the CMD file is copied in the CP file acloadfile, the command file will be executed using command IOCMI. Refer ALEX to know the details about the different procedure options available.
IOCMI:file=acloadfile-,proc=c;
Here we’ve used procedure C while executing IOCMI command. In this option remaining commands are executed even if some commands are not accepted or executed. But in Procedure a can be used in case output printout of each command is desired.
• Output logs can be captured to check for those commands which are not executed.
4 Summary
It is now clear that this procedure of handling mass commands will help us in a lot many ways in managing the critical activities involving mass change in subscriber’s profile. Till now, we’ve tested it with APG only. IOG possibility is yet to be explored.
The is a report on usage and advantages of the tool Gonzales which is very useful for mass command exercises in HLR with respect to O&M activities .
1 Introduction
The Tool Gonzales has been used to execute mass commands in HLR with APG and its been found very effective as the output results are much faster than the mml commands or even HGMCI Command, This can help us all in Important migrations like HLR, SCP or SDP migrations. The tool has been tested successfully in few important migrations in north.
• The commands can be checked for any possible error with different procedure options.
• The average time for executing 1 Lac mml commands is around 7 mins..
• The mass execution is always recommended in off peak hours as processor load shoots up to 30-40%.
• Error result in executing any command will be captured in the output logs and can be checked and corrected.
2 Existing difficulties in Handling Mass Command Activities
1. Executing DT’s of mml commands from normal desktops is quite time consuming. Hence all the activities involving mass change in subscriber’s profile in HLR results in either delay in completion of the migration activities or errors in running DT’s manually are found out after quite some time which may be leading to revenue loss or customer dissatisfaction.
2. Sometimes, speed of mml session becomes very slow due to more parallel sessions resulting in much time for executing mml commands.
3. To manage the multiple mml sessions in HLR sometimes
3 How we can use this for O& M Activities
We can use Gonzales and IOCMI command to run any mml command in HLR or any AXE node. The testing has been done for HLR with APG only.The complete procedure can be simply divided into three parts.
3.1 Prepare the load file through Gonzales
All mml commands which are to be executed in HLR can be captured in a CMD file. It is always recommended to put a maximum of 1 Lac commands in a single CMD file as it keeps the processor load of CP within safe limit. Following is the procedure to make loadfile from the tool
• Use the File menu and click “Open” option.
• Select the CMD file where you have kept the commands.
• The screen will show you list of three processed files as shown below
• The load file which is without any extension (first in the list as shown above) is the actual load file which is to be used further.
• It is recommended to rename the CMD filenames as acloadfile1 and next CMD filename as acloadfile2 and so on.
3.2 Transfer the load file in AP of HLR
After selecting the Load file, the next task is to transfer the file from your desktop to CP; the following steps will cover the procedure
• Login into the cluster of the the APG using pcAnywhere.
• Open the following directory in L drive of the APG
L:\FMS\Data\tmp\
• Make a new directory in the current “tmp” folder using mkdir command
mkdir Gonzales
• This will be a temporary folder which can be deleted after the completion of the activity.
• Now using the File Transfer Application of the APG.transfer the load file from your desktop to the following location of the APG.
L:\FMS\Data\tmp\gonzales
3.3 Executing Mass Commands
The Load file which is kept in the L drive of the APG is to be shifted to CP before running this load file. But we need a temporary CP file which will be used to keep the contents of this loadfile. ; the following steps will cover the procedure
• Create a CP file by using the command cpfmkfile, name the CP file as “acloadfile”
cpfmkfile -l 512 -c acloadfile relvolumsw
• Check the contents of the file by cpfls command.
L:\FMS\Data\tmp\gonzales>cpfls –l acloadfile
CPF FILE TABLE
FILE TYPE CMP VOLUME
ACLOADFILE reg yes RELVOLUMSW
TRANSFER QUEUE MODE
RLENGTH MAXSIZE MAXTIME REL ACTIVE SIZE USERS
512 0 0 [ 0R 0W]
• Copy the contents of loadfile from L:\FMS\Data\tmp\gonzales to CP file acloadfile by using ap command cpfport.
cpfport -i -m over L:\FMS\data\tmp\gonzales acloadfile
• Check the contents again after copying by cpfls command. Make sure acloadfile1 is there in the list
L:\FMS\Data\tmp\shooter>cpfls -ls acloadfile
CPF FILE TABLE
FILE TYPE CMP VOLUME
ACLOADFILE reg yes RELVOLUMSW
TRANSFER QUEUE MODE
RLENGTH MAXSIZE MAXTIME REL ACTIVE SIZE USERS
512 0 0 [ 0R 0W]
SUBFILES SIZE USERS
ACLOADFILE-LOADFILE1 17007 0 [ 0R 0W]
• Create a mml session.
• Now when the CMD file is copied in the CP file acloadfile, the command file will be executed using command IOCMI. Refer ALEX to know the details about the different procedure options available.
IOCMI:file=acloadfile-
Here we’ve used procedure C while executing IOCMI command. In this option remaining commands are executed even if some commands are not accepted or executed. But in Procedure a can be used in case output printout of each command is desired.
• Output logs can be captured to check for those commands which are not executed.
4 Summary
It is now clear that this procedure of handling mass commands will help us in a lot many ways in managing the critical activities involving mass change in subscriber’s profile. Till now, we’ve tested it with APG only. IOG possibility is yet to be explored.
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