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2. Shorter TTI and Low Latency: 5G NR allows to use flexible subcarrier spacing and mmWave are standardized for higher sub carrier spacing like 60 KHz, 120 KHz and 240 KHz. The ecosystem is aligned to use 120 KHz for the deployments. In comparison to LTE and 5G low bands which works for 15 KHz SCS with slot duration is 1 ms, the mmWave 120 kHz SCS slot duration is 0.125 ms (1/8th of 15 kHz SCS). In 5G, the transmission time interval (TTI) is scheduling entity and equals to 1 slot duration therefore mmWave represents a much shorter TTI duration which leads to low latency.
Figure 3: NR frame configuration for mmWave
3. Massive MIMO Antenna: Massive multiple input, multiple output (MIMO ) is a technique of employing a larger number of antenna arrays typically greater than 8. The antennas at each end of the communications circuit are combined to minimize errors, optimize data speed, and improve the capacity of radio transmissions by enabling data to travel over many signal paths at the same time. mmWave are the waves with wavelength in range of millimeter which enables packing large number of antenna elements in a smaller form factor as compared to traditionally systems. A massive MIMO system employs an antenna array with many antennas typically in the range of 64 – 512 or even further. This technique further enables better performance results in combination with beamforming as explained in below point.
Massive MIMO antenna with large no of antenna elements
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UE 1
UE 2
UE 2
Figure 4: Massive MIMO
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