Lte – long term evolution

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LTE - Physical Layer

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  • MBSFN : Multicast/Broadcast – Single Frequency Network.
  • Focus to e-UTRAN
  • Types of Logical and Transport channels available
  • Main Functions : Coding , Phy. Layer hybrid ARQ processing, modulation, multi antenna processing, mapping of signals to corresponding time-freq. resources
  • -. 1 resource grid per antenna.
  • Multi path intensity profile
  • -. Cross Correlation of AWGN is an impulse response. What is the meaning of this?-. Spaced freq. Correlation function is generated by cross correlating two carriers which are separated by Delta(f)-. Disadv. Of single carrier transmission??
  • -. Symbol periods are now longer compared to single carrier. but bits are txd parallel in order to achieve the desired data rate. -. As Ts is high ISI can completely be removed from the system.-. Depending on the channel condition each subcarrier can be modulated using different modulation schemes (QPSK, 16QAM, 64 QAM etc..)
  • -. Each OFDM symbol is a liner combination of instantaneous signals on each of the subcarriers in the channel.
  • Lte – long term evolution

    1. 1. Why LTE ?
    2. 2. Network Topology
    3. 3. Overall RAN Architecture Logical IP Packet PDCP RLC MAC Transport PHY  PDCP : Packet Data Convergence Protocol  RLC : Radio Link Control  MAC : Medium Access Control  PHY : Physical Layer
    4. 4. Physical Layer MAC LayerLogical channels Transport channels Physical channels Channel Mapping
    5. 5. Physical LayerPhysical Channels : DL UL PDSCH PUSCH PBCH PUCCH PMCH PRACH PDCCH PHICH PCFICH
    6. 6. Generic Frame Structure 1 Frame (10 ms) 1 Slot (0.5 ms) 1 Sub Frame (1 ms) 7 OFDM symbols
    7. 7. Resource Grid 7 OFDM symbols TimeFREq R E S O U R C R E E S B O L U O R C C K E G R I DResource Element
    8. 8. OFDMWhy ?
    9. 9. ISI – Inter Symbol Interference
    10. 10. Time Spreading (Freq. SelectiveFading) When an impulse is transmitted , how Power Delay Profiledoes the average power received by Mobilevary as a function of time delay ζ ? Freq. Selective Fading : Ts < ζ0 Non Freq. Selective Fading : Ts > ζ0
    11. 11. Power Delay Profile Spaced Freq. Correlation function FTInside Coherence BW channel passes all freq. components withequal gain and linear phase Freq. Selective Fading : W > f0 Non Freq. Selective Fading : W < f0
    12. 12.  Symbol rate not increased in order to achieve high data rates. Instead of that Available BW breaks in to many narrower subcarriers and modulate generated symbols to these subcarriers. These subcarriers then combine linearly and transmit (OFDM symbol).
    13. 13. : Single Carrier Transmission1 0 1 1 : OFDM Transmission 0 1 t
    14. 14.  Cyclic Prefix added to the beginning of the OFDM symbol in order to eliminate ISI ICI – Inter Carrier Interference has already been removed by selecting subcarriers with Ts > ζ0

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