 4x2 MIMO As shown in Figure 12.45 the 4x2 MIMO provides considerable throughput gain compared 2x2 MIMO across the whole UE-measured SINR range (the peak throughput is slightly decreased 2 When per-antenna transmit power is kept constant, RSRP and SNR measured from reference signals do not change when changing from two to four transmit antennas. LTE Key Performance Indicator Optimization Figure 12.46 Average downlink cell throughput comparison between 4x2 MIMO and 2x2 MIMO due to the higher RS overhead). Similar performance improvement can also be measured from the network statistics as a cell level throughput improvement as shown in Figure 12.46. The average cell throughput improvement is measured over network-level over weekly statistics. The 2x2 MIMO downlink throughput is averaged over 9 weeks and then the 4x2 MIMO weekly downlink throughput is calculated over 10 weeks. The 4x2 MIMO gain comes from power gain (i.e. 3 dB higher total power compared to 2x2 MIMO) and therefore higher usage of dual-stream transmission especially at low coverage areas (as shown in Figure 12.45). Double cross-polarized antennas were used to minimize the correlation impact and get the best possible performance gain. On average per cell the 4x2 MIMO provides around 120% throughput compared to the 2x2 MIMO which is similar to the improvement for around 5 dB UE-measured SINR area in Figure 12.45. In the uplink direction the four-way interference rejection combining (IRC) reception at the eNodeB improves the average PUSCH SINR. The network statistics of four-way IRC reception PUSCH SINR improvement over two-way IRC reception is shown in Figure 12.47. The PUSCH SINR improvement is calculated as the difference between daily cluster-level PUSCH SINR after activation or four-way IRC reception and average of PUSCH SINR over 10 consecutive days before activation of four-way IRC reception. The PUSCH SINR improvement is around 4 dB which provides uplink throughput improvement as shown in Figure 12.40 as well as decreases the number of UEs for w