## 6 Comparison of the Proposed Schemes  
This section highlights the main differences between the proposed techniques that have been discussed in the previous sections. Table 3 summarizes these differences in terms of the modifications that each technique requires, the synchronization requirements, the complexity and the performance of each cooperation scheme. The complexity of each technique is divided into two different aspects named expected implementation complexity and information exchange overhead. The expected implementation complexity indicates the number of modifications to the current standards and protocols of each wireless technology that each proposed technique requires. For instance, the \"Enhanced LTE LAA\" technique requires only a few changes to the LTE LAA standards in order to allow variable mute and transmission opportunity periods, as well as transmission, reception and interpretation of the special energy patterns. On the other hand, the \"adjustment of LTE and Wi-Fi transmission based on requirements and history\" technique requires an average implementation effort, as it involves a sophisticated coordinator unit that must be capable to communicate with the co-located networks and tune the LTE parameters based on different parameters (current requirements and history). The information exchange overhead expresses the amount of information or signals that are exchanged between the co-located wireless networks towards the attainment of cooperation according to each technique. For example, the \"Inter-RAT TDMA\" cooperation scheme requires the exchange of several energy level patterns between the co-located networks, so that they can reserve and release the medium prior to and after a transmission. In contrast, according to the \"adjustment of LTE transmission based on Wi-Fi requirements\" technique, a Wi-Fi network informs the coordinator about its requirements in an event-based manner and in a relatively slow timescale (tens of milliseconds up to a few seconds). Thus, such technique is expected to have a low information exchange overhead. Furthermore, the performance of each proposed cooperation scheme is divided into two aspects named degree of cooperation and expected spectral efficiency. The degree of cooperation indicates the eagerness of each technique to cooperate. The lower the degree of cooperation, the lower the performance of the cooperation technique. For instance, the \"negotiation between LTE and Wi-Fi\" technique offers a high degree of cooperation, as the participating networks exchange information and negotiate about the spectral requirements towards the best possible serving of their QoS requirements. In contrast, the \"inter-RAT TDMA\" technique offers a low degree of cooperation as a network simply reserves the medium for the shortest possible period in an altruistic manner. The expected spectral efficiency indicates the expected capability of each proposed technique to manage and share the spectrum between the different co-located wireless technologies in an efficient way. For instance, the \"negotiation between LTE and Wi-Fi\" technique is expected to have a high spectral efficiency, as it selects variable LTE and Wi-Fi slots based on the negotiation result between the co-located technologies. Similar to the standalone operation of wireless technology, where there is no other competitor for the wireless resources, the number of the nodes operating in each technology will have an impact on the spectral efficiency that each technique can provide. Regarding the LTE network, if there are many UEs, then the resources will be divided in to the different UEs by the LTE scheduler. When there are multiple Wi-Fi nodes, then more nodes would compete during the LTE idle slots decreasing the provided spectral efficiency. In this case, a TDMA channel access scheme for Wi-Fi could improve the achieved spectral efficiency.