Читать книгу Dynamic Spectrum Access Decisions - George F. Elmasry - Страница 110

One can conceptualize this case with very dense urban deployment where the end‐user device can obtain spectrum awareness information from multiple SAs and can use spectrum recommendations from multiple SAs to select the best spectrum band to operate on. Notice that if some QoS metrics are supplied to the end user as part of the recommendations, the end user can make the final decision on which band and which access point to select based on multiple factors, including least power consumption, highest data rate, and adhering to required QoS metrics thresholds.

Figure 6.14 illustrates this case where the end user obtains four different recommendations of spectrum use from four different SAs. The end user makes the final local DSA decision on which recommendation it will use.

Figure 6.14 The end use as the final arbitrator.

It is important to note that this case with the end user making the final arbitration decision does not exclude designing a system that uses the macrocell as the fusion center or a system that makes SAs work autonomously. The arbitration here is in the context of arbitrating between different recommendations from different SA points and considering other metrics such as QoS and rate while making the end user reach the final decision on which recommendation to use.

A service provider building a 5G infrastructure can build all the above capabilities in the deployed infrastructure and can enable or disable certain capabilities based on network management decisions or some cognitive algorithms that can morph the deployed infrastructure functionalities based on sensing information. One always needs to distinguish between capabilities or assets and how to use them dynamically. There are pros and cons for some capabilities that make them worth enabling only under certain conditions. For example, the case in Figure 6.14 has the disadvantage of requiring the end‐user device to perform an arbitration decision, which is an extra processing requirement on a device with limited battery. However, in very dense urban deployment with the close proximity of multiple cells, the device is already not consuming too much power in maintaining links, making it possible for the device to use some power for arbitration decisions. Also, in the case of autonomous SAs, we have the challenge of having a sparse deployment where an SA would have to rely on limited spectrum sensing information sources, which can lead to encountering a hidden node. However, one can see that in disaster areas, creating autonomous 5G access points is urgent enough to overcome the impact of higher probability of hidden node interference.

5G standardization offers the service provider a lot of flexibility and different service providers will use different spectrum arbitration techniques or have some capabilities enabled or disabled based on network monitoring and management decisions.