LTE Network Fundamentals

 LTE Network Fundamentals: Essential Questions and Answers :-

Q.1 What is possible range of PCI?
->0-503, PSS(0,1,2) and SSS(0-167)
Q.2 What are the Physical Downlink Signals?
->Reference signal and synchronization signals - PSS and SSS
Q.3 Difference between RSRP & RSRQ?
->RSRP – avg power across all received RS symbols in measurement bandwidth
->RSRQ-NxRSRP/RSSI
->N- no of RBs of eutra rssi measurement bandwidth
Q.4 Repetition period of MIB?
->40ms
Q.5 What is modulation scheme used for MIB?
->QPSK
Q.6 Which channel carries user data in DL? (Basic)
->PDSCH
Q.7 How many OFDM symbols are used for PDCCH?
->1, 2, or 3 as indicated by PCFICH
Q.8 Which Physical DL channel carries the Paging channel?
->PDSCH
Q.9 S1 Interface
->Enode B - MME - S1C and Enode B - SGW - S1U
Q.10 Function of PHICH
->HARQ indication
Q.11 Modulation scheme in PHICH?
->BPSK
Q.12 What All BW supported in LTE?
->1.4MHz, 3MHz, 5MHz, 10MHz, 15MHz, 20MHz
Q.13 What is X2?
->Inter eNB link for HO
Q.14 Modulation in LTE?
->BPSK, QPSK, 16QAM, 64QAM
Q.15 Define RB
-> 12 subcarriers * 14 Symbols makes one RB
Q.16 What is Resource Element?
->Smallest entity, 1 symbol (1 subcarrier x 1 symbol period)
Q.17 What is TTI, Subframe?
->1ms, 14 Symbols
Q.18 Frame Length?
->10ms
Q.19 User plane Latency target in LTE?
->10ms
Q.20 What is Subcarrier BW?
->15KHz
Q.21 What Type of HO Supported in LTE?
->Hard Handover
Q.22 What are A3 & A5 events?
->Better Cell Handover and Threshold based - Coverage based
Q.23 What is MIMO?
->Spatial Multiplexing technique - Enhance Data Rates
Q.24 Types of MIMO?
->Singletx, Tx Diversity, Spatial Multiplexing
Q.25 Difference between TDD and FDD?
->Frame Uses (FDD different Carrier for UL and DL, in TDD same Carrier for UL/DL and Frame is shared)
Q.26 How Does UE decode PCI?
-> From PSS and SSS
Q.27 What is CQI?
-> Channel Quality Index - Range 1-15, Used as input for LA - Link Adaptation
Q.28 What Is PMI?
-> Precoding Matrix Indicator, UE reports in case of close loop MIMO. Provides feedback as PMI - Indicating the correlation of the 2 signals received in 2 receivers of UE.
Q.29 What is RI?
-> Rank Indication (1 Code Word, 2 Code Word)
Q.30 How Does RI Affect Throughput?
-> 1 Code Word: Tx Diversity, 2 Code Word: Spatial Multiplexing, throughput doubled in case of 2 Codewords
Q.31 How Does MIMO Affect Throughput?
-> Multiple Input Multiple Output, simultaneous different data from different antenna doubles the data rate
Q.32 Who reports PMI?
-> UE Reports PMI as feedback.
Q.33 What is MCS?
->Modulation Coding Scheme
Q.34 What is the difference between Tx Diversity and Spatial Multiplexing?
->Tx Diversity: Same data over Multiple Antennas, Spatial Multiplexing: Different Data over different Antennas
Q.35 What is Tracking Area Code?
->Similar to Location area or Routing Area
Q.36 What is TAI?
->MCC, MNC, TAC
Q.37 What is TAI List?
->List of Tracking areas where UE is registered