ignals are transmitted with reduced transmit power. In contrast to ABS, a blank subframe does not include transmission of control and reference signals. The coexistence between LTE and Wi-Fi networks by adjusting the output power of LTE nodes is an alternative method to minimize the interference. The Wi-Fi nodes typically employ energy detection to determine the activities of other users. More specifically, if the aggregate received energy is above a threshold, a Wi-Fi node would consider the channel to be busy and would postpone its transmission. For LTE/Wi-Fi coexistence, one may increase the transmission opportunity of Wi-Fi nodes by reducing the output power of the LTE nodes. As illustrated in Fig. 8.41, when the LTE transmit power is reduced, the transmission window for a Wi-Fi node becomes larger and the Wi-Fi node can more opportunistically transmit. On the other hand, the reduction in LTE transmit power will also result in lower LTE throughput due to the decrease of the SINR as a result of increased Wi-Fi transmissions. Considering the potentially large number of deployed Wi-Fi APs and/or LTE-based LAA nodes, the backhaul and inter-node connectivity is another key challenge in such heteroge- neous networks. An ideal backhaul (a dedicated point-to-point connection) is considered a link which provides (one-way) transport latency less than 2.5 ms and a throughput of up to 10 Gbps. Other types of backhaul links are considered non-ideal. The unlicensed and licensed carriers in ideal backhaul deployments can be co-located or inter-connected. 910 Chapter 8 Inter-node synchronization is another deployment consideration in heterogeneous networks. Both synchronous and asynchronous scenarios have been considered between LTE-based LAA and/or Wi-Fi small cells as well as between the small cells and the macrocell(s). Modern UEs often implement multiple RATs, where very close proximity of the RF compo- nents would cause in-device coexistence (IDC) interference. 3GPP LTE Rel-11 introduced several solutions for handling t