ame band. This can be done in the laboratory, where the BTSs provided by all ven- dors are set up. A power probe is installed in each BTS transmitting antenna port and 8.8 5G Overlay with Another Vendor LTE Ref Lvl M2 -85.90 dBm @ 3 us -20.0 dBm -20.0 dBm ADC Over Range: Increase Reference Level Input Atten -30.0 0.0 dB -40.0 Detection BTS1 TX RMS/Avg -50.0 BTS2 TX 1 MHz -60.0 300 kHz #Sweep Time -70.0 200 uS BTS2 RX Traces A: Normal B: Trace Hold -90.0 BTS1 RX -100.0 Sweep -110.0 dBm Continuous Trigger -160 us Center 2.372 GHz 40 us Figure 8.26 Two nearly "perfectly" misaligned TDD BTSs on oscilloscope screen. connected to an oscilloscope. The timing is then adjusted by tuning a BTS parameter that offsets the timing. The following figure shows an example of poor alignment where BTS2 starts trans- mission when BTS1 has transferred to the receiving mode. This would result in mas- sive interference in both directions. Transmissions and switching to the receiving mode should start at the same time (Figure 8.26). The synchronization process between eNodeB's, for both the intra- and inter- frequency cases, could also be automated in the future by utilizing the receiver in the BTS. The BTS could be switched to UE-receive-only mode for a period during which it could measure the timing differences on the same frequency and on other frequencies on the same band and potentially automate the timing alignment in TDD networks. 8.8 5G Overlay with Another Vendor LTE This section discusses options how to implement the 5G network using radio vendors other than the existing LTE network. The target is to introduce a new radio network vendor with 5G without significant support from an incumbent LTE vendor, and without significantly impacting the resultant network performance and user experience. The first phase of 5G is deployed with a non-standalone architecture (NSA), which couples the LTE and 5G radio layers together. The two layers are logically joined via an X2 connection, which allows for dual connectivity between the LTE and