Читать книгу Dynamic Spectrum Access Decisions - George F. Elmasry - Страница 106

The previous sections focused on spatial modeling and evaluation metrics without considering some DSA techniques that can decrease the impact of SIR on the transmission capacity of 5G infrastructure. This section focuses on one important aspect of DSM in 5G, the maximization of SI cancellation. In order to increase the infrastructure capacity, 5G uses different stages of SI cancellation, as shown in Figure 6.9.

Figure 6.9 5G FD communications with different stages of noise cancellation.

Let us consider the following aspects of SI cancellation with FD communications that makes DSM more efficient and possible with the higher frequency bands 5G is utilizing:

1 Directionality. 5G beam forming relying on MIMO antenna technology means the signal is as narrow as possible where the spectrum is concentrated to the receiving node, with minimal spectrum leaks to other transmitting and receiving node pairs using the same frequency.

2 5G MIMO antennas implement SI cancellation using multipath fading analysis stages that reach up to 20 dB gain at both the transmitting and receiving antenna. This is shown in Figure 6.9 as the MIMO antenna cancellation.

3 After using a low noise amplifier, the receiver implements further analog noise cancellation of the RF signal.

4 After the analog to digital converter, the 5G receiver further implements other digital signal noise cancellation techniques.

The 5G protocol stack and the SDR concepts of 5G allow the service provider more flexibility in implementation. Figure 6.10 shows the 5G protocol stack at a higher level. The use of 5G in specific industrial applications has the flexibility of adding software modules that can allow for adapting 5G to the industrial application needs. For example, a service provider can explore using a form of network coding in the open wireless architecture (OWA) layer for further dB gain that can be achieved when using 5G mm‐wave links for long‐range reachability. This technique will trade some bandwidth for additional error control coding redundancy.

Figure 6.10 5G protocol stack.

The reader is encouraged to explore antenna design literature for more details about how 5G MIMO antenna interference cancellation is achieved in the mm‐wave range, which is beyond the scope of this book. However, the next chapter introduces some MIMO techniques that can be considered for adapting 5G for military communications systems.