The base station architecture deployment options in case of Non-standalone deployment are depicted in Figures 1, 2 and 3 below. Option 3, Option 3a and Option 3x.
Figure 1: Non-Standalone Base Station Architectures using the 4G Core Network Option 3
Figure 2: Non-Standalone Base Station Architectures using the 4G Core Network Option 3a
Figure 3: Non-Standalone Base Station Architectures using the 4G Core Network Option 3x
What is EN-DC?
The options listed in Figure 1, 2 and 3 are known as E-UTRA - New Radio Dual Connectivity (EN-DC). E-UTRA refers to the 4G air-interface and New Radio refers to the 5G air-interface. This naming convention orders the air interface technologies according to Master Node followed by Secondary Node. In case of EN-DC --- E-UTRA is the Master Node so is named first.
UEs supporting EN-DC
UEs which support EN-DC are required to be capable of receiving downlink data at the same time across 4G and 5G air-interfaces. In 3GPP release 15, EN-DC bands for up to 5 different operating bands are included.
Generally UEs which support EN-DC are required to be capable of transmissiting uplink data at the same time across 4G and 5G air interfaces.
A UE with 2 transmitters can generate inter-modulation products which fall within the UE's receive bandwidth. In other words, UE can desensitise itself by generating interference (inter-modulation products) within its own downlink receiver.
Figure 4: Illustration of 2nd order Inter-Modulation Products
- In Figure 4, it shows an example of using operating band 1 for 4G and operating band 77 for 5G. Second order inter-modulation products are generated according to (f2-f1). It leads to inter-modulation products within the range 1320 MHz to 2280 MHz across the downlink of operating band 1. The inter-modulation products will not always coincide with the downlink of operating band 1 but will depend upon the specific allocation within each band.
- 3GPP TS 38.101-3 lists which band combinations allow single uplink transmission. UE manufacturers can use decided whether or not to support multiple simultaneous uplink transmission for these band combinations
References
- 3GPP TS 36.331
- 3GPP TS 38.101-3
- 5G NR in Bullets by Chris Johnson