The 5G new radio (NR) network is designed with the expectation that it will coexist with legacy networks for many years. Operators around the world have spent billions building out the 2G/3G/4G network on radio equipment and site acquisition. As such, there is substantial interest in leveraging and repurposing the existing infrastructure for the 5G network rollout to speed up its deployment and reduce costs. This includes sharing the existing 4G core networks, adding capacity to the backhaul, and adding on to the existing radio towers. The co-location deployment scenario of multiple radios next to each other means that the new 5G radio must be able to operate in compliance in the presence of high-power interference from the exiting radios and at the same time not interfere itself.
The 5G new radio could be co-locating with many different types of legacy radios that include permutations of the following radio access technologies (RATs).
- 5GNR time division duplexing (TDD), 5G frequency division duplexing (FDD).
- 4G long-term evolution (LTE) TDD, 4G LTE FDD.
- 3G, 2G RATs such as GSM, UMTS, CDMA, etc.
For example, a 5GNR TDD base station transceiver (BTS) could be co-located with another 5GNR FDD BTS, or a 5GNR TDD BTS could be co-located with a 4G TDD. The co-located radios might or might not be synchronous in transmit and receiver time frames.
When located in close proximity to an existing radio, the 5G radio must be designed such that it does not transmit excessive power in the neighboring radio’s receive band (UL). Furthermore, its own receiver must have the ability to handle very high input power from the neighboring radio while at the same time maintain the ability to receive very low power signals from user equipment (UE).