UMTS Question and answer part 5

71. What can we try to improve when access failure is high?


Answer –

• When access failure is high we can try the following to improve RACH performance:

• Increase maximum UE transmit power allowed: Max_allowed_UL_TX_Power.

• Increase power quickly: power_Offset_P0.

• Increase number of preambles sent in a given preamble cycle: preamble_Retrans_Max.

• Increase the number of preamble cycles: max_Preamble_Cycle.

• Increase number of RRC Connection Request retries: N300.



72. What is Eb/No requirement for HSDPA?

Answer –

The Eb/No requirement for HSDPA varies with user bit rate (data rate), typically 2 for 768kbps and 5 for 2Mbps.



73. What HS Channels are introduced in HSDPA in L1?

Answer –

HS-PDSCH – High Speed Physical Downlink Shared Channel

HS-SCCH – High Speed Shared Control Channel



74. How Power Control is implemented in HSDPA?

Answer -Initial Power is set in the same way as open Loop Power control of DCH & there is no further power control on HSDPA Shared Channel HS-DSCH. The Channel Rate is controlled by adaptive modulation & coding formats.



The principles and functionality of the power control for the HSDPA associated dedicated channels are the same as for the DPCH power control.



HS-DPCCH power is an offset relative to DPCCH depending upon whether the UE is in soft handoff or not.



The Power for HS-SCCH is fixed.



75. What FIXED SF is used for HSDPA?

Answer –

SF 16, maximum of 5 codes.



76. What do you understand by CQI Measurements?

Answer – Channel Quality Estimation (CQI) for HSDPA sessions only.

In order to aid scheduling and TFRC selection in the RBS, the UE sends a channel quality indicator (CQI) report on the uplink.

The CQI report estimates the number of bits that can be transmitted to the UE using a certain assumed HS-PDSCH power with a block error rate of 10%



77. What type of Channel Coding is used for Voice and Data services?

Answer –

Voice – Convolution Coding

Data – Turbo coding