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.
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