Dynamic Spectrum Access Decisions. George F. Elmasry

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      1 Standalone mm‐wave access. This deployment scenario is illustrated in Figure 6.1. One can think of dense urban deployments for this scenario where a high‐rise building would have most apartments using 5G cells connected to the core network through fiber links. This deployment scenario offers multiple access points to the end user and 5G calls for opportunistic serving of the end user where the cell that can offer the best service can be elected to serve the end user and hand over between cells can happen frequently.Opportunistic serving of an end user relies on DSM approaches. For example, the signal strength indicator from the different reachable cells can be used to decide which cell can be selected by the end‐user device as the access point. Other factors, such as the availability of services (a cell may have no more resources to allocate to a new end user), are also considered. Handover between cells also relies on signal strength and the calculation of self‐interference (SI) to decide which cell to switch to. This chapter elaborates more on how an end‐user device arbitrates between different access points.

      2 Nonstandalone mm‐wave access. With this deployment scenario, which is illustrated in Figure 6.2, the end user can get services through either a 5G cell or an LTE (or enhanced LTE) tower. Opportunistic serving is also used with this deployment scenario where the end user can connect through the cell or tower access point, selecting the access point that would offer the best services. The tower DSM algorithms may override the end user selection. One can conceptualize such a deployment scenario in suburbs where cell access relying on fiber cables to houses may exist offering high density mm‐wave access and high bandwidth reach to the core network through the fiber cables. This cell access does not cover all the areas, however, making the use of cellular towers using LTE or enhanced LTE necessary to create full wireless coverage.Notice in Figure 6.2 the difference between mm‐wave access depicted by the dotted small circles and the cellular tower access using the below 6 GHz range depicted by the gray circles and wider areas of coverage.

      3 The mm‐wave as an enabler. With this deployment scenario, which is illustrated in Figure 6.3, the mm‐wave is an enabler in the sense that the LTE or enhanced LTE access is already present and 5G cells can be added incrementally to the area. This scenario can be conceptualized at the start of early deployment of 5G in a given suburbs area as well as in rural areas where coverage can be sparse and fiber cables connectivity availability is limited. 5G cells can be added gradually to the area as user demand increases.One important aspect of this deployment scenario is the mm‐wave backhaul links where 5G cells can be deployed without the need for fiber cable connectivity. A 5G cell dropped anywhere can connect to the tower through a high capacity mm‐wave point‐to‐point wireless link. This ability to just deploy a 5G cell in a busy area that will find the closest tower and establish a mm‐wave point‐to‐point wireless link to the tower to flexibly offer 5G services is an important aspect of DSM. The concept of a self‐organized network (SON) is a core 5G capability.