1. How UE finds out whether N/W is using FDD or TDD ?
> Once UE finishes slot and frame synchronization (PSS &SSS reading), it figures out below 2 things apart from knowing PCI:
a. Whether system is FDD/TDD
b. Whether cyclic/extended CP is used
2. How N/W decides whether to use normal or extended CP ?
> Generally for areas having large cell coverage (may be remote area having less users), N/W prefers to use extended CP in order to compensate the large propagation delay. For areas having more UEs, N/W would prefer to use normal CP, so that overall cell Tput could be high due to more symbols.
3. How UE figures out center 62 SCs?
> By reading PSS and SSS
4. How UE figures out the number of eNB Tx Antenna, as it is not part of MIB ?
> eNB uses separate masks for 1/2/4 antenna, which is added as CRC (16bit) in MIB. These masks are pre-defined, and is known both to UE and eNB. So once MIB CRC passes, UE comes to know number of eNB Tx Antennas. This is not the only way for UE to figure out this information. Infact UE figures it out much earlier, and uses this way to cross check it.
5. Why phich-config is needed in MIB ?
> It helps UE in performing PDCCH blind decoding. In order to find the applicable PDCCH REs in control region, UE need to know how many REs will be occupied by PHICH. 1 PHICH group occupies 12 REs. Using Ng and Nprb, no of possible PHICH group can be figured out using predefined table in specification.
6. How UE knows if cell supports IMS emergency call ?
> SIB 1
7. What is the content of MSG1/MSG2?
> MSG1: Preamble Index , Size of L2/L3 message to be sent as MSG3
> MSG2: RAPID (same as preamble index in MSG1), Timing advance, UL Grant, Temp C-RNTI
8. How to debug RACH failure ?
> Case 1: RAR not received:
> If UE is successfully monitoring PDCCH (masked with RA-RNTI) till ra-ResponseWindowSize SFs (SIB2). Lets say MSG1 was sent at 323/4 and ra-ResponseWindowSize is configured as 10. So UE will be monitoring RAR from 323/8 till 324/4
> If any CRC error seen (Check radio condition: RSRP/RSRQ/SNR). In poor condition, CRC errors are expected.
> Case 2: RAR received:
> If RAPID matches with preamble index sent in MSG1
> If RAPID matches, any BackOffInd(BI) received
> Once UE finishes slot and frame synchronization (PSS &SSS reading), it figures out below 2 things apart from knowing PCI:
a. Whether system is FDD/TDD
b. Whether cyclic/extended CP is used
2. How N/W decides whether to use normal or extended CP ?
> Generally for areas having large cell coverage (may be remote area having less users), N/W prefers to use extended CP in order to compensate the large propagation delay. For areas having more UEs, N/W would prefer to use normal CP, so that overall cell Tput could be high due to more symbols.
3. How UE figures out center 62 SCs?
> By reading PSS and SSS
4. How UE figures out the number of eNB Tx Antenna, as it is not part of MIB ?
> eNB uses separate masks for 1/2/4 antenna, which is added as CRC (16bit) in MIB. These masks are pre-defined, and is known both to UE and eNB. So once MIB CRC passes, UE comes to know number of eNB Tx Antennas. This is not the only way for UE to figure out this information. Infact UE figures it out much earlier, and uses this way to cross check it.
5. Why phich-config is needed in MIB ?
> It helps UE in performing PDCCH blind decoding. In order to find the applicable PDCCH REs in control region, UE need to know how many REs will be occupied by PHICH. 1 PHICH group occupies 12 REs. Using Ng and Nprb, no of possible PHICH group can be figured out using predefined table in specification.
6. How UE knows if cell supports IMS emergency call ?
> SIB 1
7. What is the content of MSG1/MSG2?
> MSG1: Preamble Index , Size of L2/L3 message to be sent as MSG3
> MSG2: RAPID (same as preamble index in MSG1), Timing advance, UL Grant, Temp C-RNTI
8. How to debug RACH failure ?
> Case 1: RAR not received:
> If UE is successfully monitoring PDCCH (masked with RA-RNTI) till ra-ResponseWindowSize SFs (SIB2). Lets say MSG1 was sent at 323/4 and ra-ResponseWindowSize is configured as 10. So UE will be monitoring RAR from 323/8 till 324/4
> If any CRC error seen (Check radio condition: RSRP/RSRQ/SNR). In poor condition, CRC errors are expected.
> Case 2: RAR received:
> If RAPID matches with preamble index sent in MSG1
> If RAPID matches, any BackOffInd(BI) received
