English: LTE logo (Photo credit: Wikipedia) 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
- 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 .
- MBSFN
- 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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