1. Introduction
2. Overview of MU-MIMO in 3GPP Standards
2.1. Theoretical Foundations of MU-MIMO
2.2. Overview of 3GPP LTE PHY MIMO
2.2.1. Reference Signals
2.2.2. Transmission Modes
2.2.3. Precoding
2.2.4. Signalling and Terminal Feedback
2.3. LTE Release 8
Feedback | CQI type | PMI type |
---|---|---|
Aperiodic | Higher-layer configured, set of subbands: subband and wideband CQI per codeword | Single PMI |
Periodic | Wideband CQI for first codeword spatial differential CQI for
| Single PMI |
Periodic | UE-selected subbands: full CQI for first codeword spatial differential CQI for
| Single PMI |
2.4. LTE Release 9
2.5. LTE Advanced
Tx rank | Beams | ||
---|---|---|---|
Rank 1-2 | 32 | 16 (per rank) | 16 (per rank) |
Rank 3-4 | 16 | 4 (per rank) | 16 (rank 3), 8 (rank 4) |
Rank 5–7 | 1 | 4 | 1 (per rank) |
Rank 8 | 1 | 1 | 1 (per rank) |
2.6. Optimal Precoding Strategy for LTE Release 8
2.6.1. System Model
2.6.2. PMI Calculation
2.6.3. Scheduling
2.6.4. Extension to Four Transmit Antennas
3. Receiver Design and Link-Level Studies
3.1. Receiver Overview
3.2. Low-Complexity Interference-Aware Receiver
3.3. Performance and Complexity Study
Parameters | Settings |
---|---|
Test scenario | 3GPP Macrocell case 1, 19 sites, 57 cells with 3 center cells simulated |
Number of UEs | 20 UEs per cell and all 20 UEs are semistatically allocated in MU-MIMO mode when MU-MIMO transmission is configured |
Carrier frequency and simulated bandwidth | 10 MHz bandwidth centered at 2 GHz |
Packet scheduling | Proportional fair in both time and frequency domains |
1st BLER target | 10% |
Tx and Rx |
and
MIMO with SU and MU configured transmission scheme |
Tx Correlation | Uncorrelated with 4 λ Tx antennas separation and 15°azimuth spreadCorrelated with 0.5 λ Tx antennas separation and 8°azimuth spread |
MU-MIMO precoding | Unitary precoder as used in SU-MIMO LTE Release 8 |
Minimum supported datarate in MU-MIMO mode | 64 kbps |
UE MU Receiver type | LMMSE, IRC, and IA max-log MAP |
Feedback type | Per subband CQI and wideband PMI feedback(one PMI for the whole bandwidth) |
Feedback delay | 0 TTI and 8 TTI delay |
Channel models | Urban microchannel model (uncorrelated) and urban macro (correlated) |