1. Tell me how does soft/softer handover work?
★ Soft/softer handover down-link: UE rake receiver performs maximum ratio combining, i.e. UE combines multi-path signals and form a stronger signal.
★ Soft handover up-link: RNC performs selection combining, i.e. RNC selects the better signal coming from multiple NodeB.
★ Softer handover up-link: NodeB performs maximum ratio combining, i.e. NodeB rake receiver combines signals from different paths and forms a stronger signal
The uplink noise increases with the loading exponentially. When the up-link 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
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.
RSCP stands for Received Signal Code Power - the energy per chip in CPICH averaged over 512 chips.
5. Do you know how does TMA work?
A TMA reduces system noise, improves up-link sensitivity and leads to longer UE battery life. Sensitivity is the minimum input power needed to get a suitable signal-to-noise ratio (SNR) at the output of the receiver. It is determined by receiver noise figure, thermo noise power and required SNR. Thermo noise power is determined by bandwidth and temperature, SNR is determined by modulation technique, therefore the only variable is noise figure.
6. Explain typical maximum path loss?
The maximum path loss is dependent on the service and vendor recommendations; typically it is in between 135 to 140dB for urban areas and between 150 to 160dB for rural areas.
7. Do you know what is a typical antenna gain?
The antenna gain depends on antenna model; in link budget we use around 17dBi.
8. Tell me what is a typical NodeB maximum output power?
The maximum NodeB output power is usually 20W or 40W, that is, 43dBm or 46dBm.
9. What is a typical NodeB sensitivity level?
The service and load determines the NodeB sensitivity; in general, in a no-load condition, the sensitivity is between -115dBm to -125dBm. For Ericsson, the NodeB sensitivity level is calculated at around:
CS12.2: -124 dBm ,PS-64: -119 dBm, PS-128: -115 dBm, PS-384: -115 dBm
10. Explain several Event in 3G?
★ Event 1A:UTRAN will add the new cell in the UE's active cell list and will send an ACTIVE SET UPDATE message.
★ Event 1B:UTRAN will send ACTIVE SET UPDATE message to remove the cell from UE's active set.
★ Event 1C:UTRAN will send ACTIVE SET UPDATE message that will remove one or more cells and will add one or more cells. The only restriction for 1C is that there should be atleast one radio link that is not affected by the procedure.
