Tuesday, July 3, 2012

LTE Key Features in Short

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 LTE Key Features in Short
  • Downlink: OFDMA (Orthogonal Frequency Division Multiple Access)
    • Less critical AMP efficiency in BS side
    • Concerns on high RX complexity in terminal side
  • Uplink: SC-FDMA (Single Carrier-FDMA)
    • Less critical RX complexity in BS side
    • Critical AMP complexity in terminal side (Cost, power Consumption, UL coverage)
  • Single node RAN (eNB)
  • Support FDD (frame type 1) & TDD (frame type 2 for TD-SCDMA evolution) H-FDD MS
  • User data rates
    • DL (baseline): 150.8 Mbps @ 20 MHz BW w/ 2x2 SU-MIMO
    • UL (baseline): 75.4 Mbps @ 20 MHz BW w/ non-MIMO or 1x2 MU-MIMO
  • Radio frame: 10 ms (= 20 slots), Sub-frame: 1 ms (= 2 slots), Slot: 0.5 ms 
  • TTI: 1 ms
  • HARQ
    • Incremental redundancy is used as the soft combining strategy.
    • Retransmission time: 8 ms.
  • Modulation
    • DL/UL data channel = QPSK/16QAM/64QAM.
  • Hard handover-based mobility.
  • MIMO SM (Spatial Multiplexing), Beamforming, Antenna Diversity Min requirement: 2 eNB antennas & 2 UE rx antennas.
    • DL: Single-User MIMO up to 4x4 supportable, MU-MIMO.
    • UL: MU-MIMO.
  • Resource block
    • 12 subcarriers with subcarrier BW of 15kHz  ->  “180kHz”.
    • 24 subcarriers with subcarrier BW of 7.5kHz (only for MBMS).
  • Subcarrier operation
    • Frequency selective by localized subcarrier.
    • Frequency diversity by distributed subcarrier & frequency hopping.
  • Frequency hopping
    • Intra-TTI: UL (once per 0.5ms slot), DL (once per 66us symbol).
    • Inter-TTI: across retransmissions.
  • Bearer services
    • Packet only –no circuit switched voice or data services are supported.
    • Voice must use VoIP or CS-Fallback .
    • Multicast/Broadcast over a Single Frequency Network.
    • To support a Multimedia Broadcast and Multicast System (MBMS).
    • Time-synchronized common waveform is transmitted from multiple cells for a given duration.
    • The signal at MS will appear exactly as a signal transmitted from a single cell site and subject o multi-path.
    • Not only “improve the received signal strength”but also “eliminate inter-cell interference”.
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