ell multiple cells Figure 5.2.2 Small-cell deployment with and without IAB: without IAB, a separate fiber link is needed for every cell. IAB allows reducing the number of fiber links through self-backhauling. The economic constraints of rolling out 5G in the mmWave frequency range can be con- siderably lowered by also using the wireless access spectrum for backhauling and leveraging the nmWave-inherent advantages (Figure 5.2.2): The abundant capacity available at mm Wave frequencies represents a significant benefit that can be leveraged to allocate capacity for backhauling. Resource sharing between access and backhaul adds deployment flexibility and provides an incremental deployment strategy. To achieve area coverage at small traffic load, as will apply in most cases during an initial rollout, only a few fiber points are necessary to support a large quantity of mmWave cells, and most of the mmWave spectrum will be used for backhauling. As traffic grows, additional fiber points can be added, which locally shifts the resource usage from backhauling toward access. High gain beamforming can be applied on both endpoints of the backhaul link, which suppresses inter-link interference creating "wires through the air." This allows extension of backhaul to multiple hops with efficient resource reuse. Beam steering - another unique feature developed for mmWave access - is leveraged on the backhaul links for autonomous neighbor detection and connection establishment. In this manner, plug-and-play deployment of mmWave small cells can be achieved. Wireless backhauling can also be used for sub-6 GHz technologies. However, the benefits are less prominent due to smaller beamforming gain, which increases inter-link inter- ference and therefore lowers the achievable spectral efficiency. Moreover, the need for multi-hop relaying is less critical than in the mmWave frequency range. Finally, mmWave backhauling can be paired with sub-6 GHz access; for example, to enable densified net- work deployments in the sub-6 GHz range while taki